how long light year travel

How Long Would It Take To Travel A Light Year

Using the fastest man-made vehicle, NASA’s Juno spacecraft, which travels at 165,000 mph (365,000 kmph), it would take 2,958 years to travel a light year. A light year is equivalent to about 5.88 trillion miles (9.46 trillion kilometers).

Traveling at the speed of light would be the fastest way to cover vast distances in space, but current technology makes it impossible for humans or even our most advanced spacecraft to reach this speed.

Can people match the speed of a light year?

According to Einstein, it is impossible to match the speed of light. It is because light is the fastest thing in the universe, traveling at 186,000 miles per second (300,000 kilometers per second). There is not one thing that we could invent that could even match a fraction of how fast light travels.

Some scientists have theorized that a new type of engine, called a warp drive , could potentially allow humans to reach the speed of travel required to match the speed of light. However, even if future spacecrafts were able to achieve this level of propulsion, it would still take thousands of years to travel from one star system to another.

Despite the challenges, scientists continue to study space travel at faster-than-light speeds, as they are optimistic that one day we will be able to explore the vast reaches of our universe and even discover life on other planets.

For now, it would take many thousands of years to travel a light year using current technology. However, scientists remain hopeful that one day we will be able to explore the far reaches of space and perhaps even discover other life forms in distant star systems. Until then, we can continue marveling at the

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What Is a Light-Year?

An image of distant galaxies captured by the NASA/ESA Hubble Space Telescope. Credit: ESA/Hubble & NASA, RELICS; Acknowledgment: D. Coe et al.

For most space objects, we use light-years to describe their distance. A light-year is the distance light travels in one Earth year. One light-year is about 6 trillion miles (9 trillion km). That is a 6 with 12 zeros behind it!

Looking Back in Time

When we use powerful telescopes to look at distant objects in space, we are actually looking back in time. How can this be?

Light travels at a speed of 186,000 miles (or 300,000 km) per second. This seems really fast, but objects in space are so far away that it takes a lot of time for their light to reach us. The farther an object is, the farther in the past we see it.

Our Sun is the closest star to us. It is about 93 million miles away. So, the Sun's light takes about 8.3 minutes to reach us. This means that we always see the Sun as it was about 8.3 minutes ago.

The next closest star to us is about 4.3 light-years away. So, when we see this star today, we’re actually seeing it as it was 4.3 years ago. All of the other stars we can see with our eyes are farther, some even thousands of light-years away.

Stars are found in large groups called galaxies . A galaxy can have millions or billions of stars. The nearest large galaxy to us, Andromeda, is 2.5 million light-years away. So, we see Andromeda as it was 2.5 million years in the past. The universe is filled with billions of galaxies, all farther away than this. Some of these galaxies are much farther away.

An image of the Andromeda galaxy, as seen by NASA's GALEX observatory. Credit: NASA/JPL-Caltech

In 2016, NASA's Hubble Space Telescope looked at the farthest galaxy ever seen, called GN-z11. It is 13.4 billion light-years away, so today we can see it as it was 13.4 billion years ago. That is only 400 million years after the big bang . It is one of the first galaxies ever formed in the universe.

Learning about the very first galaxies that formed after the big bang, like this one, helps us understand what the early universe was like.

This picture shows hundreds of very old and distant galaxies. The oldest one found so far in GN-z11 (shown in the close up image). The image is a bit blurry because this galaxy is so far away. Credit: NASA, ESA, P. Oesch (Yale University), G. Brammer (STScI), P. van Dokkum (Yale University), and G. Illingworth (University of California, Santa Cruz)

More to explore

What Is a Galaxy?

How Far Away Is the Moon?

What Is a Nebula?

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How Far is a Light Year?

How far is a light-year ? It might seem like a weird question because isn’t a ‘year’ a unit of time, and ‘far’ a unit of distance? While that is correct, a ‘light-year’ is actually a measure of distance. A light-year is the distance light can travel in one year.

Light is the fastest thing in our Universe traveling through interstellar space at 186,000 miles/second (300,000 km/sec). In one year, light can travel 5.88 trillion miles (9.46 trillion km).

A light year is a basic unit astronomers use to measure the vast distances in space.

To give you a great example of how far a light year actually is, it will take Voyager 1 (NASA’s longest-lived spacecraft) over 17,000 years to reach 1 light year in distance traveling at a speed of 61,000 kph.

Related Post: 13 Amazing Facts About Space

Why Do We Use Light-Years?

Because space is so vast, the measurements we use here on Earth are not very helpful and would result in enormous numbers.

When talking about locations in our own galaxy we would have numbers with over 18 zeros. Instead, astronomers use light-time measurements to measure vast distances in space. A light-time measurement is how far light can travel in a given increment of time.

• Light-minute: 11,160,000 miles
• Light-hour: 671 million miles
• Light-year: 5.88 trillion miles

Understanding Light-Years

To help wrap our heads around how to use light-years, let’s look at how far things are away from the Earth starting with our closest neighbor, the Moon.

The Moon is 1.3 light-seconds from the Earth.

Earth is about 8 light-minutes (~92 million miles) away from the Sun. This means light from the Sun takes 8 minutes to reach us.

Jupiter is approximately 35 light minutes from the Earth. This means if you shone a light from Earth it would take about a half hour for it to hit Jupiter.

Pluto is not the edge of our solar system, in fact, past Pluto, there is the Kieper Belt , and past this is the Oort Cloud . The Oort cloud is a spherical layer of icy objects surrounding our entire solar system.

If you could travel at the speed of light, it would take you 1.87 years to reach the edge of the Oort cloud. This means that our solar system is about 4 light-years across from edge to edge of the Oort Cloud.

The distance between the Sun and Interstellar Space. NASA/JPL-Caltech .

The nearest known exoplanet orbits the star Proxima Centauri , which is four light years away (~24 trillion miles). If a modern-day jet were to fly to this exoplanet it would not arrive for 5 million years.

One of the most distant exoplanets is 3,000 light-years (17.6 quadrillion miles) away from us in the Milky Way. If you were to travel at 60 miles an hour, you would not reach this exoplanet for 28 billion years.

Our Milky Way galaxy is approximately 100,000 light-years across (~588 quadrillion miles). Moving further into our Universe, our nearest neighbor, the Andromeda galaxy is 2.537 million light-years (14.7 quintillion miles) away from us.

The Andromeda Galaxy is 2.537 million light-years away from us.

Light, a Window into the Past

While we cannot actually travel through time, we can see into the past. How? We see objects because they either emit light or light has bounced off their surface and is traveling back to us.

Even though light is the fastest thing in our Universe, it takes time to reach us. This means that for any object we are seeing it how it was in the past. How far in the past? However long it took the light to reach us.

For day-to-day objects like a book or your dog, it takes a mere fraction of a fraction of a second for the light bouncing off the object to reach your eye. The further away an object is, the further into its past you are looking.

For instance, light from the Sun takes about 8 minutes to reach Earth, this means we are always seeing the Sun how it looked 8 minutes ago if you were on its surface.

The differences between Lunar Distance, an Astronomical Unit, and a Light Year. Illustration by Star Walk .

Traveling back through our solar system, Jupiter is approximately 30 light-minutes from Earth, so we see Jupiter how it looked 30 minutes ago if you were on its surface. Extending out into the Universe to our neighbor the Andromeda galaxy, we see it how it was 2.537 million years ago.

If there is another civilization out in the Universe watching Earth, they would not see us here today, they would see Earth in the past. A civilization that lives 65 million light-years away would see dinosaurs roaming the Earth.

Helpful Resources:

• How big is the Solar System? (Universe Today)
• What is an Astronomical Unit? (EarthSky)
• How close is Proxima Centauri? (NASA Imagine The Universe)

Light Year Calculator

What is light year, how to calculate light years.

With this light year calculator, we aim to help you calculate the distance that light can travel in a certain amount of time . You can also check out our speed of light calculator to understand more about this topic.

We have written this article to help you understand what a light year is and how to calculate a light year using the light year formula . We will also demonstrate some examples to help you understand the light year calculation.

A light year is a unit of measurement used in astronomy to describe the distance that light travels in one year . Since light travels at a speed of approximately 186,282 miles per second (299,792,458 meters per second), a light year is a significant distance — about 5.88 trillion miles (9.46 trillion km) . Please check out our distance calculator to understand more about this topic.

The concept of a light year is important for understanding the distances involved in space exploration. Since the universe is so vast, it's often difficult to conceptualize the distances involved in astronomical measurements. However, by using a light year as a unit of measurement, scientists and astronomers can more easily compare distances between objects in space.

As the light year is a unit of measure for the distance light can travel in a year , this concept can help us to calculate the distance that light can travel in a certain time period. Hence, let's have a look at the following example:

• Source: Light
• Speed of light: 299,792,458 m/s
• Time traveled: 2 years

You can perform the calculation in three steps:

Determine the speed of light.

The speed of light is the fastest speed in the universe, and it is always a constant in a vacuum. Hence, the speed of light is 299,792,458 m/s , which is 9.46×10¹² km/year .

Compute the time that the light has traveled.

The subsequent stage involves determining the duration of time taken by the light to travel. Since we are interested in light years, we will be measuring the time in years.

To facilitate this calculation, you may use our time lapse calculator . In this specific scenario, the light has traveled for a duration of 2 years.

Calculate the distance that the light has traveled.

The final step is to calculate the total distance that the light has traveled within the time . You can calculate this answer using the speed of light formula:

distance = speed of light × time

Thus, the distance that the light can travel in 100 seconds is 9.46×10¹² km/year × 2 years = 1.892×10¹³ km

How do I calculate the distance that light travels?

You can calculate the distance light travels in three steps:

Determine the light speed .

Determine the time the light has traveled.

Apply the light year formula :

distance = light speed × time

How far light can travel in 1 second?

The light can travel 186,282 miles, or 299,792,458 meters, in 1 second . That means light can go around the Earth just over 7 times in 1 second.

Why is the concept of a light year important in astronomy?

The concept of a light year is important in astronomy because it helps scientists and astronomers more easily compare distances between objects in space and understand the vastness of the universe .

Can light years be used to measure time?

No , despite the name, you cannot use light years to measure time. They only measure distance .

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FREQUENTLY ASKED QUESTIONS

What is a light-year.

Light-year is the distance light travels in one year. Light zips through interstellar space at 186,000 miles (300,000 kilometers) per second and 5.88 trillion miles (9.46 trillion kilometers) per year.

We use light-time to measure the vast distances of space.

It’s the distance that light travels in a specific period of time. Also: LIGHT IS FAST, nothing travels faster than light.

How far can light travel in one minute? 11,160,000 miles. It takes 43.2 minutes for sunlight to reach Jupiter, about 484 million miles away. Light is fast, but the distances are vast . In an hour, light can travel 671 million miles.

Earth is about eight light minutes from the Sun. A trip at light-speed to the very edge of our solar system – the farthest reaches of the Oort Cloud, a collection of dormant comets way, way out there – would take about 1.87 years. Keep going to Proxima Centauri, our nearest neighboring star, and plan on arriving in 4.25 years at light speed.

When we talk about the enormity of the cosmos, it’s easy to toss out big numbers – but far more difficult to wrap our minds around just how large, how far, and how numerous celestial bodies really are.

To get a better sense, for instance, of the true distances to exoplanets – planets around other stars – we might start with the theater in which we find them, the Milky Way galaxy

Our galaxy is a gravitationally bound collection of stars, swirling in a spiral through space. Based on the deepest images obtained so far, it’s one of about 2 trillion galaxies in the observable universe. Groups of them are bound into clusters of galaxies, and these into superclusters; the superclusters are arranged in immense sheets stretching across the universe, interspersed with dark voids and lending the whole a kind of spiderweb structure. Our galaxy probably contains 100 to 400 billion stars, and is about 100,000 light-years across. That sounds huge, and it is, at least until we start comparing it to other galaxies. Our neighboring Andromeda galaxy, for example, is some 220,000 light-years wide. Another galaxy, IC 1101, spans as much as 4 million light-years.

Based on observations by NASA’s Kepler Space Telescope, we can confidently predict that every star you see in the sky probably hosts at least one planet. Realistically, we’re most likely talking about multi-planet systems rather than just single planets. In our galaxy of hundreds of billions of stars, this pushes the number of planets potentially into the trillions. Confirmed exoplanet detections (made by Kepler and other telescopes, both in space and on the ground) now come to more than 4,000 – and that’s from looking at only tiny slices of our galaxy. Many of these are small, rocky worlds that might be at the right temperature for liquid water to pool on their surfaces.

The nearest-known exoplanet is a small, probably rocky planet orbiting Proxima Centauri – the next star over from Earth. A little more than four light-years away, or 24 trillion miles. If an airline offered a flight there by jet, it would take 5 million years. Not much is known about this world; its close orbit and the periodic flaring of its star lower its chances of being habitable.

The TRAPPIST-1 system is seven planets, all roughly in Earth’s size range, orbiting a red dwarf star about 40 light-years away. They are very likely rocky, with four in the “habitable zone” – the orbital distance allowing potential liquid water on the surface. And computer modeling shows some have a good chance of being watery – or icy – worlds. In the next few years, we might learn whether they have atmospheres or oceans, or even signs of habitability.

One of the most distant exoplanets known to us in the Milky Way is Kepler-443b. Traveling at light speed, it would take 3,000 years to get there. Or 28 billion years, going 60 mph.

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What is a light-year?

The fastest thing that we know of is light which travels at a speed of 186,000 miles or 300,000 kilometers per second in empty space. To get an idea of how fast this is, light can travel about seven times around Earth in one second! Astronomers use the speed of light to measure how far away things are in space. A light-year (ly) is the distance that light can travel in one year. In one year, light travels about 5,880,000,000,000 miles or 9,460,000,000,000 kilometers. So, this distance is 1 light-year. For example, the nearest star to us is about 4.3 light-years away. Our galaxy, the Milky Way, is about 150,000 light-years across, and the nearest large galaxy, Andromeda, is 2.3 million light-years away.

What is the speed of light?

The speed of light is the speed limit of the universe. Or is it?

What is a light-year?

• Speed of light FAQs
• Special relativity
• Faster than light
• Slowing down light
• Faster-than-light travel

Bibliography

The speed of light traveling through a vacuum is exactly 299,792,458 meters (983,571,056 feet) per second. That's about 186,282 miles per second — a universal constant known in equations as "c," or light speed. 

According to physicist Albert Einstein 's theory of special relativity , on which much of modern physics is based, nothing in the universe can travel faster than light. The theory states that as matter approaches the speed of light, the matter's mass becomes infinite. That means the speed of light functions as a speed limit on the whole universe . The speed of light is so immutable that, according to the U.S. National Institute of Standards and Technology , it is used to define international standard measurements like the meter (and by extension, the mile, the foot and the inch). Through some crafty equations, it also helps define the kilogram and the temperature unit Kelvin .

But despite the speed of light's reputation as a universal constant, scientists and science fiction writers alike spend time contemplating faster-than-light travel. So far no one's been able to demonstrate a real warp drive, but that hasn't slowed our collective hurtle toward new stories, new inventions and new realms of physics.

Related: Special relativity holds up to a high-energy test

A l ight-year is the distance that light can travel in one year — about 6 trillion miles (10 trillion kilometers). It's one way that astronomers and physicists measure immense distances across our universe.

Light travels from the moon to our eyes in about 1 second, which means the moon is about 1 light-second away. Sunlight takes about 8 minutes to reach our eyes, so the sun is about 8 light minutes away. Light from Alpha Centauri , which is the nearest star system to our own, requires roughly 4.3 years to get here, so Alpha Centauri is 4.3 light-years away.

"To obtain an idea of the size of a light-year, take the circumference of the Earth (24,900 miles), lay it out in a straight line, multiply the length of the line by 7.5 (the corresponding distance is one light-second), then place 31.6 million similar lines end to end," NASA's Glenn Research Center says on its website . "The resulting distance is almost 6 trillion (6,000,000,000,000) miles!"

Stars and other objects beyond our solar system lie anywhere from a few light-years to a few billion light-years away. And everything astronomers "see" in the distant universe is literally history. When astronomers study objects that are far away, they are seeing light that shows the objects as they existed at the time that light left them. 

This principle allows astronomers to see the universe as it looked after the Big Bang , which took place about 13.8 billion years ago. Objects that are 10 billion light-years away from us appear to astronomers as they looked 10 billion years ago — relatively soon after the beginning of the universe — rather than how they appear today.

Related: Why the universe is all history

Speed of light FAQs answered by an expert

We asked Rob Zellem, exoplanet-hunter and staff scientist at NASA's Jet Propulsion Lab, a few frequently asked questions about the speed of light. 

Dr. Rob Zellem is a staff scientist at NASA's Jet Propulsion Laboratory, a federally funded research and development center operated by the California Institute of Technology. Rob is the project lead for Exoplanet Watch, a citizen science project to observe exoplanets, planets outside of our own solar system, with small telescopes. He is also the Science Calibration lead for the Nancy Grace Roman Space Telescope's Coronagraph Instrument, which will directly image exoplanets. 

What is faster than the speed of light?

Nothing! Light is a "universal speed limit" and, according to Einstein's theory of relativity, is the fastest speed in the universe: 300,000 kilometers per second (186,000 miles per second). 

Is the speed of light constant?

The speed of light is a universal constant in a vacuum, like the vacuum of space. However, light *can* slow down slightly when it passes through an absorbing medium, like water (225,000 kilometers per second = 140,000 miles per second) or glass (200,000 kilometers per second = 124,000 miles per second). 

Who discovered the speed of light?

One of the first measurements of the speed of light was by Rømer in 1676 by observing the moons of Jupiter . The speed of light was first measured to high precision in 1879 by the Michelson-Morley Experiment. 

How do we know the speed of light?

Rømer was able to measure the speed of light by observing eclipses of Jupiter's moon Io. When Jupiter was closer to Earth, Rømer noted that eclipses of Io occurred slightly earlier than when Jupiter was farther away. Rømer attributed this effect due the time it takes for light to travel over the longer distance when Jupiter was farther from the Earth. 

How did we learn the speed of light?

As early as the 5th century, Greek philosophers like Empedocles and Aristotle disagreed on the nature of light speed. Empedocles proposed that light, whatever it was made of, must travel and therefore, must have a rate of travel. Aristotle wrote a rebuttal of Empedocles' view in his own treatise, On Sense and the Sensible , arguing that light, unlike sound and smell, must be instantaneous. Aristotle was wrong, of course, but it would take hundreds of years for anyone to prove it. 

In the mid 1600s, the Italian astronomer Galileo Galilei stood two people on hills less than a mile apart. Each person held a shielded lantern. One uncovered his lantern; when the other person saw the flash, he uncovered his too. But Galileo's experimental distance wasn't far enough for his participants to record the speed of light. He could only conclude that light traveled at least 10 times faster than sound.

In the 1670s, Danish astronomer Ole Rømer tried to create a reliable timetable for sailors at sea, and according to NASA , accidentally came up with a new best estimate for the speed of light. To create an astronomical clock, he recorded the precise timing of the eclipses of Jupiter's moon , Io, from Earth . Over time, Rømer observed that Io's eclipses often differed from his calculations. He noticed that the eclipses appeared to lag the most when Jupiter and Earth were moving away from one another, showed up ahead of time when the planets were approaching and occurred on schedule when the planets were at their closest or farthest points. This observation demonstrated what we today know as the Doppler effect, the change in frequency of light or sound emitted by a moving object that in the astronomical world manifests as the so-called redshift , the shift towards "redder", longer wavelengths in objects speeding away from us. In a leap of intuition, Rømer determined that light was taking measurable time to travel from Io to Earth. 

Rømer used his observations to estimate the speed of light. Since the size of the solar system and Earth's orbit wasn't yet accurately known, argued a 1998 paper in the American Journal of Physics , he was a bit off. But at last, scientists had a number to work with. Rømer's calculation put the speed of light at about 124,000 miles per second (200,000 km/s).

In 1728, English physicist James Bradley based a new set of calculations on the change in the apparent position of stars caused by Earth's travels around the sun. He estimated the speed of light at 185,000 miles per second (301,000 km/s) — accurate to within about 1% of the real value, according to the American Physical Society .

Two new attempts in the mid-1800s brought the problem back to Earth. French physicist Hippolyte Fizeau set a beam of light on a rapidly rotating toothed wheel, with a mirror set up 5 miles (8 km) away to reflect it back to its source. Varying the speed of the wheel allowed Fizeau to calculate how long it took for the light to travel out of the hole, to the adjacent mirror, and back through the gap. Another French physicist, Leon Foucault, used a rotating mirror rather than a wheel to perform essentially the same experiment. The two independent methods each came within about 1,000 miles per second (1,609 km/s) of the speed of light.

Another scientist who tackled the speed of light mystery was Poland-born Albert A. Michelson, who grew up in California during the state's gold rush period, and honed his interest in physics while attending the U.S. Naval Academy, according to the University of Virginia . In 1879, he attempted to replicate Foucault's method of determining the speed of light, but Michelson increased the distance between mirrors and used extremely high-quality mirrors and lenses. Michelson's result of 186,355 miles per second (299,910 km/s) was accepted as the most accurate measurement of the speed of light for 40 years, until Michelson re-measured it himself. In his second round of experiments, Michelson flashed lights between two mountain tops with carefully measured distances to get a more precise estimate. And in his third attempt just before his death in 1931, according to the Smithsonian's Air and Space magazine, he built a mile-long depressurized tube of corrugated steel pipe. The pipe simulated a near-vacuum that would remove any effect of air on light speed for an even finer measurement, which in the end was just slightly lower than the accepted value of the speed of light today. 

Michelson also studied the nature of light itself, wrote astrophysicist Ethan Siegal in the Forbes science blog, Starts With a Bang . The best minds in physics at the time of Michelson's experiments were divided: Was light a wave or a particle? 

Michelson, along with his colleague Edward Morley, worked under the assumption that light moved as a wave, just like sound. And just as sound needs particles to move, Michelson and Morley and other physicists of the time reasoned, light must have some kind of medium to move through. This invisible, undetectable stuff was called the "luminiferous aether" (also known as "ether"). 

Though Michelson and Morley built a sophisticated interferometer (a very basic version of the instrument used today in LIGO facilities), Michelson could not find evidence of any kind of luminiferous aether whatsoever. Light, he determined, can and does travel through a vacuum.

"The experiment — and Michelson's body of work — was so revolutionary that he became the only person in history to have won a Nobel Prize for a very precise non-discovery of anything," Siegal wrote. "The experiment itself may have been a complete failure, but what we learned from it was a greater boon to humanity and our understanding of the universe than any success would have been!"

Special relativity and the speed of light

Einstein's theory of special relativity unified energy, matter and the speed of light in a famous equation: E = mc^2. The equation describes the relationship between mass and energy — small amounts of mass (m) contain, or are made up of, an inherently enormous amount of energy (E). (That's what makes nuclear bombs so powerful: They're converting mass into blasts of energy.) Because energy is equal to mass times the speed of light squared, the speed of light serves as a conversion factor, explaining exactly how much energy must be within matter. And because the speed of light is such a huge number, even small amounts of mass must equate to vast quantities of energy.

In order to accurately describe the universe, Einstein's elegant equation requires the speed of light to be an immutable constant. Einstein asserted that light moved through a vacuum, not any kind of luminiferous aether, and in such a way that it moved at the same speed no matter the speed of the observer. 

Think of it like this: Observers sitting on a train could look at a train moving along a parallel track and think of its relative movement to themselves as zero. But observers moving nearly the speed of light would still perceive light as moving away from them at more than 670 million mph. (That's because moving really, really fast is one of the only confirmed methods of time travel — time actually slows down for those observers, who will age slower and perceive fewer moments than an observer moving slowly.)

In other words, Einstein proposed that the speed of light doesn't vary with the time or place that you measure it, or how fast you yourself are moving. 

Therefore, objects with mass cannot ever reach the speed of light. If an object ever did reach the speed of light, its mass would become infinite. And as a result, the energy required to move the object would also become infinite: an impossibility.

That means if we base our understanding of physics on special relativity (which most modern physicists do), the speed of light is the immutable speed limit of our universe — the fastest that anything can travel. 

What goes faster than the speed of light?

Although the speed of light is often referred to as the universe's speed limit, the universe actually expands even faster. The universe expands at a little more than 42 miles (68 kilometers) per second for each megaparsec of distance from the observer, wrote astrophysicist Paul Sutter in a previous article for Space.com . (A megaparsec is 3.26 million light-years — a really long way.) 

In other words, a galaxy 1 megaparsec away appears to be traveling away from the Milky Way at a speed of 42 miles per second (68 km/s), while a galaxy two megaparsecs away recedes at nearly 86 miles per second (136 km/s), and so on. 

"At some point, at some obscene distance, the speed tips over the scales and exceeds the speed of light, all from the natural, regular expansion of space," Sutter explained. "It seems like it should be illegal, doesn't it?"

Special relativity provides an absolute speed limit within the universe, according to Sutter, but Einstein's 1915 theory regarding general relativity allows different behavior when the physics you're examining are no longer "local."

"A galaxy on the far side of the universe? That's the domain of general relativity, and general relativity says: Who cares! That galaxy can have any speed it wants, as long as it stays way far away, and not up next to your face," Sutter wrote. "Special relativity doesn't care about the speed — superluminal or otherwise — of a distant galaxy. And neither should you."

Does light ever slow down?

Light in a vacuum is generally held to travel at an absolute speed, but light traveling through any material can be slowed down. The amount that a material slows down light is called its refractive index. Light bends when coming into contact with particles, which results in a decrease in speed.

For example, light traveling through Earth's atmosphere moves almost as fast as light in a vacuum, slowing down by just three ten-thousandths of the speed of light. But light passing through a diamond slows to less than half its typical speed, PBS NOVA reported. Even so, it travels through the gem at over 277 million mph (almost 124,000 km/s) — enough to make a difference, but still incredibly fast.

Light can be trapped — and even stopped — inside ultra-cold clouds of atoms, according to a 2001 study published in the journal Nature . More recently, a 2018 study published in the journal Physical Review Letters proposed a new way to stop light in its tracks at "exceptional points," or places where two separate light emissions intersect and merge into one.

Researchers have also tried to slow down light even when it's traveling through a vacuum. A team of Scottish scientists successfully slowed down a single photon, or particle of light, even as it moved through a vacuum, as described in their 2015 study published in the journal Science . In their measurements, the difference between the slowed photon and a "regular" photon was just a few millionths of a meter, but it demonstrated that light in a vacuum can be slower than the official speed of light. 

Can we travel faster than light?

— Spaceship could fly faster than light

— Here's what the speed of light looks like in slow motion

— Why is the speed of light the way it is?

Science fiction loves the idea of "warp speed." Faster-than-light travel makes countless sci-fi franchises possible, condensing the vast expanses of space and letting characters pop back and forth between star systems with ease. 

But while faster-than-light travel isn't guaranteed impossible, we'd need to harness some pretty exotic physics to make it work. Luckily for sci-fi enthusiasts and theoretical physicists alike, there are lots of avenues to explore.

All we have to do is figure out how to not move ourselves — since special relativity would ensure we'd be long destroyed before we reached high enough speed — but instead, move the space around us. Easy, right? 

One proposed idea involves a spaceship that could fold a space-time bubble around itself. Sounds great, both in theory and in fiction.

"If Captain Kirk were constrained to move at the speed of our fastest rockets, it would take him a hundred thousand years just to get to the next star system," said Seth Shostak, an astronomer at the Search for Extraterrestrial Intelligence (SETI) Institute in Mountain View, California, in a 2010 interview with Space.com's sister site LiveScience . "So science fiction has long postulated a way to beat the speed of light barrier so the story can move a little more quickly."

Without faster-than-light travel, any "Star Trek" (or "Star War," for that matter) would be impossible. If humanity is ever to reach the farthest — and constantly expanding — corners of our universe, it will be up to future physicists to boldly go where no one has gone before.

Additional resources

For more on the speed of light, check out this fun tool from Academo that lets you visualize how fast light can travel from any place on Earth to any other. If you’re more interested in other important numbers, get familiar with the universal constants that define standard systems of measurement around the world with the National Institute of Standards and Technology . And if you’d like more on the history of the speed of light, check out the book " Lightspeed: The Ghostly Aether and the Race to Measure the Speed of Light " (Oxford, 2019) by John C. H. Spence.

Aristotle. “On Sense and the Sensible.” The Internet Classics Archive, 350AD. http://classics.mit.edu/Aristotle/sense.2.2.html .

D’Alto, Nick. “The Pipeline That Measured the Speed of Light.” Smithsonian Magazine, January 2017. https://www.smithsonianmag.com/air-space-magazine/18_fm2017-oo-180961669/ .

Fowler, Michael. “Speed of Light.” Modern Physics. University of Virginia. Accessed January 13, 2022. https://galileo.phys.virginia.edu/classes/252/spedlite.html#Albert%20Abraham%20Michelson .

Giovannini, Daniel, Jacquiline Romero, Václav Potoček, Gergely Ferenczi, Fiona Speirits, Stephen M. Barnett, Daniele Faccio, and Miles J. Padgett. “Spatially Structured Photons That Travel in Free Space Slower than the Speed of Light.” Science, February 20, 2015. https://www.science.org/doi/abs/10.1126/science.aaa3035 .

Goldzak, Tamar, Alexei A. Mailybaev, and Nimrod Moiseyev. “Light Stops at Exceptional Points.” Physical Review Letters 120, no. 1 (January 3, 2018): 013901. https://doi.org/10.1103/PhysRevLett.120.013901 . 

Hazen, Robert. “What Makes Diamond Sparkle?” PBS NOVA, January 31, 2000. https://www.pbs.org/wgbh/nova/article/diamond-science/ . 

“How Long Is a Light-Year?” Glenn Learning Technologies Project, May 13, 2021. https://www.grc.nasa.gov/www/k-12/Numbers/Math/Mathematical_Thinking/how_long_is_a_light_year.htm . 

American Physical Society News. “July 1849: Fizeau Publishes Results of Speed of Light Experiment,” July 2010. http://www.aps.org/publications/apsnews/201007/physicshistory.cfm . 

Liu, Chien, Zachary Dutton, Cyrus H. Behroozi, and Lene Vestergaard Hau. “Observation of Coherent Optical Information Storage in an Atomic Medium Using Halted Light Pulses.” Nature 409, no. 6819 (January 2001): 490–93. https://doi.org/10.1038/35054017 . 

NIST. “Meet the Constants.” October 12, 2018. https://www.nist.gov/si-redefinition/meet-constants . 

Ouellette, Jennifer. “A Brief History of the Speed of Light.” PBS NOVA, February 27, 2015. https://www.pbs.org/wgbh/nova/article/brief-history-speed-light/ . 

Shea, James H. “Ole Ro/Mer, the Speed of Light, the Apparent Period of Io, the Doppler Effect, and the Dynamics of Earth and Jupiter.” American Journal of Physics 66, no. 7 (July 1, 1998): 561–69. https://doi.org/10.1119/1.19020 . 

Siegel, Ethan. “The Failed Experiment That Changed The World.” Forbes, April 21, 2017. https://www.forbes.com/sites/startswithabang/2017/04/21/the-failed-experiment-that-changed-the-world/ . 

Stern, David. “Rømer and the Speed of Light,” October 17, 2016. https://pwg.gsfc.nasa.gov/stargaze/Sun4Adop1.htm . 

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Vicky Stein is a science writer based in California. She has a bachelor's degree in ecology and evolutionary biology from Dartmouth College and a graduate certificate in science writing from the University of California, Santa Cruz (2018). Afterwards, she worked as a news assistant for PBS NewsHour, and now works as a freelancer covering anything from asteroids to zebras. Follow her most recent work (and most recent pictures of nudibranchs) on Twitter. 

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What is a light year? How long is it? Why you might not be seeing stars in real time.

Humans have discovered powerful telescopes to gaze at the beautiful night sky, only to realize that distant objects in space are things of the past. The light of these distant objects takes a certain amount of time to reach Earth.

Take the Sun for example, it is the closest star to Earth and its light takes about 8.3 minutes to reach Earth and its inhabitants. This also means humans always see the sun as it was 8.3 minutes ago each time they look up.

This characteristic applies to stars, galaxies and any other illuminating celestial objects in space. Depending on their distance from Earth, the light exuded by these space objects takes equivalent time to reach humans.

Coldest place in the universe: It's only *slightly* warmer than absolute zero.

What are the biggest planets?: Trying to understanding the scale of our universe.

What is a light year?

While a year is a measure of time, a light year or light-year is a measure of distance. A light year is the distance light travels in one Earth year, according to NASA. 

The International Astronomical Union defines a light year as the distance traveled by light in one Julian year or 365.25 days in vacuum.

According to NASA, light travels in the interstellar space at 186,000 miles (300,000 kilometers) per second and 5.88 trillion miles (9.46 trillion kilometers) per year.

Earth is approximately 320 light years from the North Star, Polaris which means that it takes 320 years for the Polaris' light to reach Earth. 

Space facts: What's the coldest planet in the solar system? What about in the known universe?

Just Curious: Answering your everyday questions about life, pets, travel and more.

How fast is a light year in mph?

There’s no answer to this question. A light year is a measure of distance while mph (miles per hour) is a measure of speed. So, a light year cannot be measured in mph.

Here's what we know:

Light travels at a constant speed of 670,616,629 mph which means that light covers a speed of 670 million miles in an hour.

Light travels a distance of 5.88 trillion miles in one Earth year, according to NASA.

By Darin Anthony - Last Updated: April 17, 2024

How Long Would It Take to Travel One Light Year?

Article Contents

We hear the term “light-years” almost anytime a new star or exo-planet is discovered. But how long would it take to travel one light year?

The fastest human-made vehicle, NASA’s Parker Solar Probe, would take 1,698 years to travel one light-year , the sum of roughly 5.88 trillion miles (9.46 trillion kilometers), the distance light travels in one year.

In September 2023, NASA’s Parker Solar Probe set a new record, clocking a blistering speed of 394,736 miles per hour (635,266 kilometers per hour)—the fastest ever recorded.

But 1,698 years is an incredibly long time. The Parker Solar Probe would have just completed a distance of one light year if it had left during the 4th century (326 A.D.) and maintained its top speed the entire journey.

Let’s look more closely at the speed of light and what it means to travel one light-year.

Understanding Light Years

Speed of light.

Over one hundred years ago, Albert Einstein’s theory of relativity deciphered the math of a cosmic limit. It says nothing can go faster than  the speed of light , which is approximately 186,282 miles per second (299,792 km/s) within the vacuum of space.

To help understand how fast light speed is, we’ll compare it to the longest intercontinental flight in the world today.

A flight from New York to Singapore covers 9,526 miles (15.332km) and, on average, takes 18hrs 40 minutes. If a commercial airliner could travel the speed of light, symbolically, it could make that trip almost 20 times in one second!

Measuring Distances

Understanding the vastness of space begins with grasping the concept of a light-year . It’s a unit of measurement scientists use to note the length of astronomical distances.

Astronomers use two common measurements to help make an incredibly long distance, a huge number, more manageable.

Astronomical Unit (AU) : It’s the distance the Sun’s light takes to reach the Earth. This distance is approximately 93 million miles (150 million kilometers) and takes eight light minutes.

Light-Year (LY): It represents the unit of distance that light travels in one Earth year , which is approximately 5.88 trillion miles (9.46 trillion kilometers).

So, the time it takes Light to travel one light year? One Earth year or roughly 365 days .

When speaking of distances in the universe, an astronomer refers to distances in an (AU) or (LY) depending on how great of a distance.

For example, when referring to the distance of the Andromeda Galaxy from Earth, it is stated as 2.5m (LY) light years( i ). However, the shorter distance to Neptune from the Sun is noted as approximately 30.7 (AU)( i ).

Since a light-year is a larger unit of distance than (AU) it is more likely to be used when expressing bigger numbers.

Travel Time

If we could travel the distance of one light-year from Earth, we would end up in the mid-region of the Oort cloud .

It is the outermost area of our solar system before reaching the realm of deep outer space. The time it would take to journey this one light-year would greatly depend on our mode of transportation.

I’ve put together several calculations using a light-year (ly) calculator. Using the average miles per hour (mph) for current technology we use today. It makes the complexity of traversing such an immense distance very obvious.

See the infographic I have provided below, which has a link to the calculator within the caption.

Let’s look at some of the examples the infographic highlights in relation to how long it takes to travel a light-year.

If you decide to put on some walking shoes and head off towards the mid-region of the Oort cloud , a light year away, be sure to pack lunch. At a normal pace of 3/mph, it would take nearly 224 million years to get there without stopping to eat, sleep, or bathroom breaks.

Walking (3/mph) >>> One Light Year >>> 224M Years

You could pull the car cover off the Corvette stored in the garage for a quicker ride. Even then, traveling at an average speed of 100 mph would take six million and seven hundred thousand years (6.7m years) to travel a light year . That’s without stopping or slowing down.

Drive (100/mph) >>> One Light Year >>> 6.7M Years

How about a ticket on the “Big ol’ Jet Airliner”? It would still take you over one million years (1.118m yrs) to span the distance of one light year on a commercial Jet .

Commercial Jet (600/mph) >>> One Light Year >>> 1.18M Years

The point is that the distances between objects in our solar system, galaxy, and universe are so vast it’s very challenging for our minds to grasp and comprehend it.

As of today, we do not have technology that can travel the distance of a light-year within the span of a human life, but there are future concepts. Let’s take a look.

Future Concepts to Travel Light-Years

Considering our Milky Way galaxy stretches across 100,000 light-years. Even at the speed of light, it takes 100,000 Earth years to journey from edge to edge. To bridge that distance, we’ll need to inspire some new ideas through quantum physics.

But some interesting concepts are in the works right now to dramatically shorten the length of time it takes to travel a light year.

Breakthrough Starshot

In 2016, Physicist Yuri Milner announced an engineering endeavor named “ Breakthrough Starshot ,” with backing support from such notable figures as Stephen Hawking (now deceased), and Mark Zuckerberg.

Their aim is to develop a fleet of light sail centimeter-sized probes called StarChips . These probes are designed to travel to the Alpha Centauri star system , located 4.37 light-years away, potentially within 20 to 30 years at speeds of 15-20% the speed of light.

Currently, using the Parker Solar Probe’s top speed, to travel 4 light-years would take over 7000 years, so that would be an amazing feat.

The project proposes a flyby mission to our next closest star beyond our Sun, Proxima Centauri. It is believed to be home to an Earth-sized exoplanet in the habitable zone.

The concept will leverage advanced laser technology to propel the spacecraft. Current estimates for launch are 2036.

Helical Engine

A space and aeronautics engineer has developed a concept that, in theory, would reach 99% of the speed of light without conflicting with Einstein’s theory of relativity .

Dr Burn, now a former engineer from NASA’s Space Flight Center in Alabama , believes that a system where instead of expelling propellant, it is retained, could generate an almost limitless specific impulse and open the door to interstellar space exploration.

This method involves accelerating ions near the light speed limit within a closed circuit, adjusting their speed to modify momentum. Thrust is generated by oscillating the ions back and forth in the direction of travel.

It’s Designed for long-term satellite operations without the need for refueling or powering voyages across vast distances; this engine operates without any mechanical components, relying solely on ions circulating in a vacuum loop contained by electric and magnetic fields.

If this concept is proven and successful it would mean we could travel a light-year in a little more than one year!

It’s impossible to talk about traveling at the speed of light without discussing the theory of warp drive , which was popularized by the 1960s Star Trek series.

NASA has explored this concept and will continue to do so as science and modern physics expand with future breakthroughs.

The idea behind warp drive is to manipulate the fabric of spacetime to create a bubble or a wave, often referred to as a “ warp bubble ,” that would contract space in front of the ship and expand it from behind , allowing the vessel to move from one point to another faster than light would in normal space.

It would theoretically enable interstellar travel within human lifetimes without violating the fundamental principles of Einstein’s theory of general relativity, which states that nothing can travel faster than the speed of light in a vacuum.

If this concept is ever proven, it will be a game changer for space travel in our cosmic neighborhood and beyond.

For now, the Parker Solar Probe’s top speed makes it the fastest vehicle to span the distance of a light year . The enormity of the universe will make reaching distant stars and exoplanets impossible until we can develop technologies like the Warp Drive, Starshot, or Helical engine.

It’s a humbling distance across our Milky Way. But scientists continue to unlock the mysteries of the cosmos, and one day, we may crack the code to bridge the vast galactic space within the universe.

Astronomy has peaked my curiosity and imagination from an early age. I am always thrilled to read about the latest galactic discovery or planning my next celestial observation. More about me [..]

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What Is a Light Year? Definition and Examples

The light year (ly) is a unit of length that is the distance light travels in a vacuum in one Earth year. One light year is approximately 9.46  trillion  kilometers (9.46 x 10 12  km) or 5.88 trillion miles (5.88 x 10 12  mi). The light year is used to describe distances to stars without having to use very large numbers.

Abbreviations for light year and its multiple are:

• ly – one light year
• kly – 1000 light years or one kilolight year
• Mly – 1,000,000 light years or one megalight year
• Gly – 1,000,000,000 light year or one gigalight year

Examples of Distances in Light Years

Here is a light of astronomical objects and their distance from the Sun in light years:

How Long Is a Light Year?

One common misconception about the light year is thinking it is a unit of time. This arises because the unit has the word “year” in it. The length of a light year is a length or distance, not a time (9.46 x 10 12  kilometers or 5.88 x 10 12  miles).

Julian Year vs Gregorian Year

The light year is defined with the speed of light defined as 299792458 m/s and the year being a Julian year (365.25 days).

There are different ways to measure the length of a year on Earth. The light year is defined as distance light travels in a Julian year (365.25 days). This is slightly different from the Gregorian year (365.2425 days). The Gregorian year is the type of year most of the world uses, based on the Gregorian calendar. Before 1984, astronomers defined the light year using a measured speed of light (as opposed to a defined speed) and a tropical year (time it takes for the Earth to return to the same position, like summer solstice to summer solstice, which is 31556925.9747 ephemeris seconds). Before 1984, a light year was approximately 9.460530×10 12  km. For the most part, the change doesn’t make much of a difference, but it’s good to know!

Light Year, Parsec, and AU

In addition to the light year, two other units of length are used in astronomy:

The astronomical unit (AU or au) is the distance from the Sun to the Earth. The distance between the Sun and Earth changes throughout the year because Earth’s orbit is an ellipse, but is equal to approximately 93 million miles or 150 million kilometers. In 2012, the AU was defined as exactly 149,597,870,700 meters. This is approximately 92,9555807 million miles. The modern AU definition is based on the definition of the meter, while retaining the spirit of the original definition. Because the AU is a relatively short distance (in astronomy), scientists use the astronomical unit to measure distances within the solar system or around other stars.

The parsec (pc) is a unit of length defined as exactly 648000/ π astronomical units. It is the distance from the Sun to an astronomical object with a parallax angle of one arcsecond. One parsec is equal to about 3.3 light years, 210,000 AU, 31 trillion kilometers, or 19 trillion miles. It is used to measure large distances in astronomy. Multiples of parsecs are used for enormous distances, like kiloparsecs (kpc) within the Milky Way, megaparsecs (Mpc) for mid-distance galaxies, and gigaparsecs (GPc) for distant galaxies and quasars.

In summary:

• A light year (ly) is the distance light travels in one Earth year. It is 9.4607×10 15 meters or 5.8786×10 12 miles, about 63 astronomical units or about 0.3 parsecs. It is an intermediate unit of astronomical distance.
• An astronomical unit (AU) is approximately the distance from the Sun to the Earth. It is defined as exactly 149,597,870,700 meters or about 92,9555807 million miles. It is the shortest astronomical unit of distance.
• A parsec (pc) is the distance from the Sun to a distance object with a parallax angle of one arcsecond. It is about 3.3 light years, 31 trillion kilometers, or 19 trillion miles.
• Cox, Arthur N., ed. (2000). Allen’s Astrophysical Quantities (4th ed.). New York: AIP Press / Springer. ISBN 978-0387987460.
• Hussmann, H.; Sohl, F.; Oberst, J. (2009), “Astronomical units.” in Joachim E Trümper (ed.). Astronomy, Astrophysics, and Cosmology – Volume VI/4B Solar System . Springer. ISBN 978-3-540-88054-7.
• Luque, B.; Ballesteros, F. J. (2019). “To the Sun and beyond.” Nature Physics . 15: 1302. doi: 10.1038/s41567-019-0685-3
• McNamara, D. H.; Madsen, J. B.; Barnes, J.; Ericksen, B. F. (2000). “The Distance to the Galactic Center.” Publications of the Astronomical Society of the Pacific 112 (768): 202. doi: 10.1086/316512
• Seidelmann, P. Kenneth (ed.) (1992). Explanatory Supplement to the Astronomical Almanac . Mill Valley, California: University Science Books. ISBN 978-0-935702-68-2.

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What is the speed of light? Here’s the history, discovery of the cosmic speed limit

On one hand, the speed of light is just a number: 299,792,458 meters per second. And on the other, it’s one of the most important constants that appears in nature and defines the relationship of causality itself.

As far as we can measure, it is a constant. It is the same speed for every observer in the entire universe. This constancy was first established in the late 1800’s with the experiments of Albert Michelson and Edward Morley at Case Western Reserve University . They attempted to measure changes in the speed of light as the Earth orbited around the Sun. They found no such variation, and no experiment ever since then has either.

Observations of the cosmic microwave background, the light released when the universe was 380,000 years old, show that the speed of light hasn’t measurably changed in over 13.8 billion years.

In fact, we now define the speed of light to be a constant, with a precise speed of 299,792,458 meters per second. While it remains a remote possibility in deeply theoretical physics that light may not be a constant, for all known purposes it is a constant, so it’s better to just define it and move on with life.

How was the speed of light first measured?

In 1676 the Danish astronomer Ole Christensen Romer made the first quantitative measurement of how fast light travels. He carefully observed the orbit of Io, the innermost moon of Jupiter. As the Earth circles the Sun in its own orbit, sometimes it approaches Jupiter and sometimes it recedes away from it. When the Earth is approaching Jupiter, the path that light has to travel from Io is shorter than when the Earth is receding away from Jupiter. By carefully measuring the changes to Io’s orbital period, Romer calculated a speed of light of around 220,000 kilometers per second.

Observations continued to improve until by the 19 th century astronomers and physicists had developed the sophistication to get very close to the modern value. In 1865, James Clerk Maxwell made a remarkable discovery. He was investigating the properties of electricity and magnetism, which for decades had remained mysterious in unconnected laboratory experiments around the world. Maxwell found that electricity and magnetism were really two sides of the same coin, both manifestations of a single electromagnetic force.

As Maxwell explored the consequences of his new theory, he found that changing magnetic fields can lead to changing electric fields, which then lead to a new round of changing magnetic fields. The fields leapfrog over each other and can even travel through empty space. When Maxwell went to calculate the speed of these electromagnetic waves, he was surprised to see the speed of light pop out – the first theoretical calculation of this important number.

What is the most precise measurement of the speed of light?

Because it is defined to be a constant, there’s no need to measure it further. The number we’ve defined is it, with no uncertainty, no error bars. It’s done. But the speed of light is just that – a speed. The number we choose to represent it depends on the units we use: kilometers versus miles, seconds versus hours, and so on. In fact, physicists commonly just set the speed of light to be 1 to make their calculations easier. So instead of trying to measure the speed light travels, physicists turn to more precisely measuring other units, like the length of the meter or the duration of the second. In other words, the defined value of the speed of light is used to establish the length of other units like the meter.

How does light slow down?

Yes, the speed of light is always a constant. But it slows down whenever it travels through a medium like air or water. How does this work? There are a few different ways to present an answer to this question, depending on whether you prefer a particle-like picture or a wave-like picture.

In a particle-like picture, light is made of tiny little bullets called photons. All those photons always travel at the speed of light, but as light passes through a medium those photons get all tangled up, bouncing around among all the molecules of the medium. This slows down the overall propagation of light, because it takes more time for the group of photons to make it through.

In a wave-like picture, light is made of electromagnetic waves. When these waves pass through a medium, they get all the charged particles in motion, which in turn generate new electromagnetic waves of their own. These interfere with the original light, forcing it to slow down as it passes through.

Either way, light always travels at the same speed, but matter can interfere with its travel, making it slow down.

Why is the speed of light important?

The speed of light is important because it’s about way more than, well, the speed of light. In the early 1900’s Einstein realized just how special this speed is. The old physics, dominated by the work of Isaac Newton, said that the universe had a fixed reference frame from which we could measure all motion. This is why Michelson and Morley went looking for changes in the speed, because it should change depending on our point of view. But their experiments showed that the speed was always constant, so what gives?

Einstein decided to take this experiment at face value. He assumed that the speed of light is a true, fundamental constant. No matter where you are, no matter how fast you’re moving, you’ll always see the same speed.

This is wild to think about. If you’re traveling at 99% the speed of light and turn on a flashlight, the beam will race ahead of you at…exactly the speed of light, no more, no less. If you’re coming from the opposite direction, you’ll still also measure the exact same speed.

This constancy forms the basis of Einstein’s special theory of relativity, which tells us that while all motion is relative – different observers won’t always agree on the length of measurements or the duration of events – some things are truly universal, like the speed of light.

Can you go faster than light speed?

Nope. Nothing can. Any particle with zero mass must travel at light speed. But anything with mass (which is most of the universe) cannot. The problem is relativity. The faster you go, the more energy you have. But we know from Einstein’s relativity that energy and mass are the same thing. So the more energy you have, the more mass you have, which makes it harder for you to go even faster. You can get as close as you want to the speed of light, but to actually crack that barrier takes an infinite amount of energy. So don’t even try.

How is the speed at which light travels related to causality?

If you think you can find a cheat to get around the limitations of light speed, then I need to tell you about its role in special relativity. You see, it’s not just about light. It just so happens that light travels at this special speed, and it was the first thing we discovered to travel at this speed. So it could have had another name. Indeed, a better name for this speed might be “the speed of time.”

Related: Is time travel possible? An astrophysicist explains

We live in a universe of causes and effects. All effects are preceded by a cause, and all causes lead to effects. The speed of light limits how quickly causes can lead to effects. Because it’s a maximum speed limit for any motion or interaction, in a given amount of time there’s a limit to what I can influence. If I want to tap you on the shoulder and you’re right next to me, I can do it right away. But if you’re on the other side of the planet, I have to travel there first. The motion of me traveling to you is limited by the speed of light, so that sets how quickly I can tap you on the shoulder – the speed light travels dictates how quickly a single cause can create an effect.

The ability to go faster than light would allow effects to happen before their causes. In essence, time travel into the past would be possible with faster-than-light travel. Since we view time as the unbroken chain of causes and effects going from the past to the future, breaking the speed of light would break causality, which would seriously undermine our sense of the forward motion of time.

Why does light travel at this speed?

No clue. It appears to us as a fundamental constant of nature. We have no theory of physics that explains its existence or why it has the value that it does. We hope that a future understanding of nature will provide this explanation, but right now all investigations are purely theoretical. For now, we just have to take it as a given.

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What is a light-year?

The light-year is an indispensable unit of measurement for anyone trying to understand outer space. Get a group of astronomers talking, and you’ll hear them say “light-years” about as often as you hear football fans mention “yards.”

For nonscientists, though, the light-year can be a puzzling concept. It’s a unit of distance even though it might sound like a unit of time. Adding to the confusion, sci-fi movies and TV shows routinely bungle the concept.

Even the original "Star Trek" series got light-years wrong. In a 1968 episode, the alien princess Elaan of Troyius tells Captain Kirk she’d rather hide in her room for “10 light-years” than come out and speak to him. Oops.

How far is a light-year?

A light-year is the distance a beam of light travels in a vacuum in one year. It’s important to specify a vacuum because light slows as it passes through any kind of matter. (In water, for instance, it travels about 25 percent slower.) Most of the universe is a near-perfect vacuum, so astronomers can generally assume that light is moving at its top speed .

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Light travels at 299,792,458 meters (186,282.397 miles) per second. Multiply that number by the number of seconds in a year (31,557,600), and you get your answer: One light-year is 9,460,730,473,000 kilometers, or 5,878,625,373,000 miles.

That’s probably more digits than you were looking for. Round it off to 6 trillion miles, and you’re still close enough for any in-the-know nerd conversation.

Why do astronomers measure distance in light-years?

Familiar units like kilometers and miles are absurdly small for describing the vastness of the cosmos. Take the example of Proxima Centauri , the nearest star beyond the sun. You could say that it's about 24,900,000,000,000 miles away — or save a lot of breath and call the distance a tidy 4.24 light-years.

Most of the stars you see at night lie within a few hundred light-years of Earth. The Milky Way galaxy in which we live happens to be a nice, round 100,000 light-years across . The Andromeda Galaxy is 2.54 million light-years away — a big number but still a whole lot more manageable than “14 quintillion, 900 quadrillion miles.”

So light-years are only a measure of distance, not time?

Strictly speaking, yes. A light-year is a unit of distance, just like feet and inches. If you want to avoid any confusion, you can stop right here.

But there’s another fascinating side to the light-year story. Since light moves at a finite speed , everything you see is outdated: Your view of the world is actually an image of what things looked like at the instant their light began traveling toward you.

If you're staring across a room, the lag is just billionths of a second — utterly imperceptible. Look at the moon, and you see it as it was about a second-and-a-half ago. Watch a sunset, and you're seeing the sun of 8.3 minutes ago.

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The effect is far more pronounced for the stars. They're light-years away, so when you look at them you're looking years into the past.

Sirius, the brightest star in the sky, lies 8.6 light-years from Earth, which means the light you’re seeing left it 8.6 years ago. Put another way, we always see Sirius as it was 8.6 years ago. Deneb, a prominent summer star in the constellation Cygnus, is about 2,500 light-years away. Its twinkling glow was already en route to us while Aristotle was alive.

And remember, other galaxies are even more distant. Powerful telescopes like Hubble can detect galaxies whose light has been traveling our way for billions of years. Thus those ethereal Hubble images show us galaxies as they were billions of years ago — in some cases, from a time before Earth came to be.

In short, a light-year describes distance only — but light itself provides a sort of time machine, allowing us to observe the cosmos as it was long ago.

How do we know the speed of light?

The crucial insight came from Ole Rømer, a 17th-century Danish astronomer. During the 1660s, he was studying one of Jupiter’s moons, Io , when he noticed something odd: When Jupiter and Earth were at their greatest distance from one another, Io would slip into Jupiter’s shadow a few minutes later than astronomers predicted. When the two planets were closest together, the event seemed to occur a few minutes early.

Rømer realized that the delay had nothing to do with Io. Rather, it was an illusion caused by the time it takes for light to span the extra distance when Earth and Jupiter are on opposite sides of the sun. His calculations showed that light travels 131,000 miles a second — a remarkably good estimate, considering that he was doing this work just 60 years after the invention of the telescope.

Who came up with the term light-year?

“The concept of light speed as a measurement of distance already happened by the end of the 17th century, following from the discovery of the finiteness of light speed by Rømer,” says Frédéric Arenou, an astronomer and science historian at the Paris Observatory.

People latched on to the idea so quickly that it’s impossible to credit any individual with certainty. Arenou points to one good candidate, however: the English scholar Francis Roberts, who in 1694 mused that “Light takes up more time in travelling from the stars to us, than we in making a West-India Voyage.”

At first, these ideas were necessarily vague because scientists had only a rough idea of how far away the stars are. The breakthrough moment came in 1838, when German astronomer Friedrich Bessel measured the exact distance to the star 61 Cygni. In describing the huge number he got, Bessel wrote that “light employs 10.3 years to traverse this distance.” That’s the closest thing to a specific moment when the specific concept of the light-year was born.

Within a couple of decades, the light-year was commonplace in popular science writing. But Arenou says professional astronomers long resisted using the term — and for a surprising reason. They considered the light-year insufficiently scientific, since it cannot be measured directly.

How do astronomers measure distances in light-years?

Bessel reckoned the distance to 61 Cygni by observing its parallax, the apparent back-and-forth motion in the sky caused by Earth’s motion around the sun.

Parallax is still one of astronomers’ most powerful tools for measuring distance. The European Space Agency spent 650 million Euros ($750 million) on the Gaia space telescope , which is currently using parallax to measure the distances to more than a billion stars across our galaxy.

Science Scientists say mysterious 'Oumuamua' object could be an alien spacecraft

Beyond the Milky Way, where parallaxes are too small even for Gaia to detect, astronomers calculate distances by observing certain types of variable stars or brilliant supernova explosions . Those approaches still rely on parallax measurements as their point of reference, however.

Because their work is so deeply rooted in parallax, astronomers commonly use a second distance unit, the parsec (“parallax arc-second,” a small angle). One parsec equals 3.26 light-years. Sometimes the parsec is more scientifically relevant, but researchers often switch between the two terms for no obvious reason except style.

Unfortunately, the “sec” in parsec sounds like a unit of time, leading to more confusion. In the 1977 movie "Star Wars: A New Hope," Han Solo brags that he “ made the Kessel Run in less than 12 parsecs .” Star Wars fans have tied themselves in knots trying to explain away that obvious goof. Better to stick with the light-year. It’s all the astronomy you need — and lets you dabble in time travel, too.

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How Long is a Light-Year?

The light-year is a measure of distance, not time. It is the total distance that a beam of light, moving in a straight line, travels in one year. To obtain an idea of the size of a light-year, take the circumference of the earth (24,900 miles), lay it out in a straight line, multiply the length of the line by 7.5 (the corresponding distance is one light-second), then place 31.6 million similar lines end to end. The resulting distance is almost 6 trillion (6,000,000,000,000) miles!

How Long Would It Take to Travel 1 Light Year?

On Earth, we measure distance through steps, meters, kilometers, miles, or some other unit of measurement by which we can determine distance. The universe is so large, that sometimes measuring in kilometers or miles is pointless. In space, it is easier to measure distance with the help of light years. We can easily determine how long it takes us to cover a certain distance in kilometers if we know how fast we are going, but we never calculate how long it takes us to travel a light year. Maybe it’s time to answer that question. How long would it take to travel one light year?

To travel one light year, if we travel at the speed of light, it would take us one year. In spacecraft, time would pass differently, so one would not even have the feeling of traveling and the travel time would fly by in less than a second. Time stops for a man, as does his aging, as long as his spacecraft travels at the speed of light. 

For people on Earth, however, the journey of one light year would take one year.  The difference in the experience of traveling one light year occurs due to different perceptions of time on Earth and in space. On Earth, we have learned to count time in seconds, minutes, hours, days and years. For an object traveling at the speed of light, time is irrelevant. A journey lasting one light year or a billion light years for a person traveling at the speed of light will seem absolutely the same in time. Less than a second, almost zero time.

How long is a light year?

First thing you need to know: a light year is a unit of measurement for distance, not for time! It is a unit of distance that represents the total distance that the beam of light travels in one year moving in a straight line in empty space. It is assumed that there are no strong magnetic or gravitational fields at this distance. This unit of measurement is used primarily in astronomy to calculate the distance between celestial objects. It would be a bit complicated to use kilometers or miles to measure distances in space given that the distance between certain celestial bodies would require numerous zeros. 

The speed of light is 299 792458 meters per second. One Julian year, the year how we measure it, has 365.25 days, or 31,500,000 seconds. The light year is equal to 9,460,730,472,580,800 meters or approximately 9,461 × 1015 meters.

How many days is a light year in human years?

A light year is used to calculate the distance that light travels in a human year. One light year is therefore the same as one human year. Fifty light years is 50 human years. There is no difference in the length of the light year and human year.

A light year is just a name used for a unit of distance, not time. When we hear the term light year, we immediately think of time, but a light year has nothing to do with calculating the year. The distances in space are becoming so great that it is impractical to express them in common units of measurement, so we turn to light years.

There is even a unit that is larger than a light year, and that is the parsec. It is used to measure the distance between celestial bodies located outside the Solar System. One parsec is equal to 3.3 light years or 31 trillion kilometers.

How fast can we travel in space?

The speed at which we will travel in space depends on the spacecraft we use.

The human speed record was set by astronauts during the Apollo 10 mission. Apollo 10 was a test mission just before sending a man to the Moon. When returning from lunar orbit, their spacecraft reached a speed of 39,897 kilometers per hour. Such speed is still not possible to reach with today’s technology. Its successor, the Apollo 11, reached tremendous speeds at times but traveled at an average speed of 5,000 km / h.

In order to stay in space orbit, the shuttle must reach a speed of 28,000 km / h. That’s 9 times faster than a bullet. However, the space shuttle doesn’t go that fast all the time. The speed at which it will fly depends on the orbital altitude, which is approximately between 304 kilometers to 528 kilometers above sea level depending on the mission.

SpaceX, a private company whose goal is to enable the colonization of Mars, is one of the most modern spacecraft companies. In 2012, it began supplying the International Space Station with supplies. In 2020, SpaceX sent its Crew Dragon spacecraft to the International Space Station for the first time. The spacecraft was transporting two astronauts traveling at an average speed of 28 163 kilometers per hour. The International Space Station is quite close to Earth, so it’s hard to reach a higher speed on such a short journey.

The fastest object that humans have made is the NASA Helios 2 rehearsal. During the mission, Helios 2 reached a speed of 252,793 km / h. This rehearsal was launched back in 1976, so it is surprising that no one has overtaken it so far.

Parker Solar Probe will soon break the record set by Helios 2. Parker solar probe is a NASA probe launched in 2018 whose mission is making observations of the outer corona of the Sun. In 2025, it should come closest to the Sun and at that time it will travel at a speed of 690,000 km / h or 0.064% of the speed of light.

When we study the speed that modern spacecraft can reach, we are still years, and perhaps centuries, far from reaching the speed of light, if we ever reach it at all.

We know, however, to what extent we can go. The first discussions about the speed of light began with the ancient Greek philosopher Aristotle who considered light travel instantaneously. Albert Einstein later in 1905 wrote a paper on special relativity. Einstein’s theory of special relativity proved that there is a limited speed of travel that we can reach: the speed of light. Nothing can travel faster than 300,000 kilometers per second which is the speed of light. The object should have an infinite amount of energy to make the object reach the speed of light.

How long would it take us right now to travel 1 light year?

With today’s technology, it would take us approximately 37,200 years to travel the distance of one light year.

For example, if we were to travel at a speed of 58,536 km / h, which is the speed at which the New Horizons rehearsal travels on its way to Pluto, it would take us just under 20,000 years to cross the path of one light year.

If the spacecraft were traveling at the speed at which Helios 2 was traveling, the spacecraft would have traveled one light-year in 4269 light-years.

If a Saturn V rocket that took the man to the moon were to travel, it would take 108,867 years to travel.

If we set out on that journey by the fastest plane, we will need 305975 human years.

If we were to set out on foot on a journey one light year long, it would take us 225 million years to cross it. At this time, the breaks that you would definitely need along the way are not even included.

A snail would cross a distance of one light-year by 83304201370000 years.

How long would it take to travel 1 light year at the speed of light?

If spacecraft traveled at the speed of a light year, it would travel the distance of one light year in one human year. If we were to travel at a speed of half a light year, it would take us 2 years. If we could travel at the speed of light, we could go around the Earth 7.5 times in one second.

However, for a man traveling in a spacecraft at the speed of light, time would not flow the same as outside the spacecraft. The man in the spacecraft would not age, and the time it took to cross one light-year would seem like a second. Even less than a second. This is not just an assumption. Numerous experiments have proven that indeed time flows differently when it travels at the speed of light.

It’s hard to explain what it would feel like to travel at the speed of light because we’re still a long way from technology that could allow us to do so at that speed. We currently need three days to the moon, but if we traveled at the speed of light, we would cross that path in just 1.3 seconds. Exploring the universe at the speed of a light year would significantly speed up the whole process, and we can only hope for that for now.

https://www.grc.nasa.gov/www/k-12/Numbers/Math/Mathematical_Thinking/how_long_is_a_light_year.htm

https://spaceplace.nasa.gov/light-year/en/

https://futurism.com/how-long-would-it-take-to-walk-a-light-year

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Could A Telescope Ever See The Beginning Of Time?

The James Webb Space Telescope, or JWST for short, is one of the most advanced telescopes ever built . Planning for JWST began over 25 years ago, and construction efforts spanned over a decade. It was launched into space on Dec. 25, 2021, and within a month arrived at its final destination: 930,000 miles away from Earth. Its location in space allows it a relatively unobstructed view of the universe .

The telescope design was a global effort , led by NASA, and intended to push the boundaries of astronomical observation with revolutionary engineering. Its mirror is massive – about 21 feet (6.5 meters) in diameter. That’s nearly three times the size of the Hubble Space Telescope, which launched in 1990 and is still working today.

It’s a telescope’s mirror that allows it to collect light. JWST’s is so big that it can “see” the faintest and farthest galaxies and stars in the universe. Its state-of-the-art instruments can reveal information about the composition, temperature and motion of these distant cosmic objects.

As an astrophysicist , I’m continually looking back in time to see what stars, galaxies and supermassive black holes looked like when their light began its journey toward Earth, and I’m using that information to better understand their growth and evolution. For me, and for thousands of space scientists, the James Webb Space Telescope is a window to that unknown universe.

Just how far back can JWST peer into the cosmos and into the past? About 13.5 billion years.

Time Travel

A telescope does not show stars, galaxies and exoplanets as they are right now. Instead, astronomers are catching a glimpse of how they were in the past . It takes time for light to travel across space and reach our telescopes. In essence, that means a look into space is also a trip back in time.

This is even true for objects that are quite close to us. The light you see from the Sun left it about 8 minutes, 20 seconds earlier. That’s how long it takes for the Sun’s light to travel to Earth .

You can easily do the math on this. All light – whether sunlight, a flashlight or a light bulb in your house – travels at 186,000 miles (almost 300,000 kilometers) per second . That’s just over 11 million miles (about 18 million kilometers) per minute. The Sun is about 93 million miles (150 million kilometers) from Earth. That comes out to about 8 minutes, 20 seconds.

But the farther away something is, the longer its light takes to reach us. That’s why the light we see from Proxima Centauri , the closest star to us aside from our Sun, is 4 years old; that is, it’s about 25 trillion miles (approximately 40 trillion kilometers) away from Earth, so that light takes just over four years to reach us. Or, as scientists like to say, four light years .

Most recently, JWST observed Earendel, one of the farthest stars ever detected . The light that JWST sees from Earendel is about 12.9 billion years old.

The James Webb Space Telescope is looking much farther back in time than previously possible with other telescopes, such as the Hubble Space Telescope . For example, although Hubble can see objects 60,000 times fainter than the human eye is able, the JWST can see objects almost nine times fainter than even Hubble can .

The Big Bang

But is it possible to see back to the beginning of time?

The Big Bang is a term used to define the beginning of our universe as we know it. Scientists believe it occurred about 13.8 billion years ago . It is the most widely accepted theory among physicists to explain the history of our universe.

The name is a bit misleading, however, because it suggests that some sort of explosion, like fireworks, created the universe. The Big Bang more closely represents the appearance of rapidly expanding space everywhere in the universe. The environment immediately after the Big Bang was similar to a cosmic fog that covered the universe, making it hard for light to travel beyond it. Eventually, galaxies, stars and planets started to grow.

That’s why this era in the universe is called the “cosmic dark ages.” As the universe continued to expand, the cosmic fog began to rise , and light was eventually able to travel freely through space. In fact, a few satellites have observed the light left by the Big Bang, about 380,000 years after it occurred. These telescopes were built to detect the splotchy leftover glow from the Big Bang , whose light can be tracked in the microwave band.

However, even 380,000 years after the Big Bang, there were no stars and galaxies. The universe was still a very dark place. The cosmic dark ages wouldn’t end until a few hundred million years later, when the first stars and galaxies began to form.

The James Webb Space Telescope was not designed to observe as far back as the Big Bang, but instead to see the period when the first objects in the universe began to form and emit light. Before this time period, there is little light for the James Webb Space Telescope to observe, given the conditions of the early universe and the lack of galaxies and stars.

Peering back to the time period close to the Big Bang is not simply a matter of having a larger mirror – astronomers have already done it using other satellites that observe microwave emission from very soon after the Big Bang . So, the James Webb Space Telescope observing the universe a few hundred million years after the Big Bang isn’t a limitation of the telescope. Rather, that’s actually the telescope’s mission. It’s a reflection of where in the universe we expect the first light from stars and galaxies to emerge.

By studying ancient galaxies, scientists hope to understand the unique conditions of the early universe and gain insight into the processes that helped them flourish. That includes the evolution of supermassive black holes, the life cycle of stars, and what exoplanets – worlds beyond our solar system – are made of.

Adi Foord is an Assistant Professor of Astronomy and Astrophysics at the University of Maryland, Baltimore County. This article is republished from The Conversation under a Creative Commons license . Read the original article .

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Never seen an exploding star? This year, you'll have your chance

Joe Hernandez

An artist's rendering shows the T Coronae Borealis star system, which contains a white dwarf and a red giant. Conceptual Image Lab/Goddard Space Flight Center/NASA hide caption

An artist's rendering shows the T Coronae Borealis star system, which contains a white dwarf and a red giant.

Space enthusiasts, thank your lucky stars.

Astronomers expect that this year you'll be able to see the explosion of a star system in our Milky Way galaxy by simply looking up at the sky.

Yes, we know you just spent all that time figuring out how to catch the solar eclipse.

But the upcoming nova of the T Coronae Borealis star system is far less common, occurring roughly once every 80 years. A nova takes place when a small star suddenly and dramatically brightens for a short period.

"Seeing that star blow up is much rarer than a solar eclipse," NASA astronomer Bill Cooke told NPR . "So it's kind of a once-in-a-lifetime thing."

Located about 3,000 light years from Earth, T Coronae Borealis is a binary star system containing a white dwarf and a red giant.

As the red giant heats up and its pressure grows, it starts spewing matter that's collected by the white dwarf, according to NASA . The smaller star, roughly the size of Earth, gets so overloaded with that matter that explodes.

This star ate its own planet. Earth may share the same fate

"Eventually it accumulates so much material that literally a thermonuclear reaction starts and the star brightens by hundreds of times. It just gets super bright," Cooke said.

Such an event is called a nova , derived from the Latin for "new star," because a once-dim celestial object suddenly becomes illuminated, giving the impression of a new star.

T Coronae Borealis is expected to nova at any moment between now and September. When it does, the star system could surge from a +10 magnitude, which can't be seen by the naked eye, to a +2 magnitude, roughly the same level of brightness as the North Star. (Higher positive numbers indicate dimmer stars.)

Astronomers say that once the nova reaches its peak brightness, it will be visible to viewers for several days. Those using binoculars will be able to see it for just over a week before it dims again.

The Picture Show

A rare solar eclipse darkened skies and dazzled viewers across the u.s..

An outburst of T Coronae Borealis was scientifically observed in 1866, but it may have also been spotted as far back as 1217 by a German monk who documented an object that "shone with great light" for "many days." The star system last exploded in 1946.

NASA says the nova will be visible in the constellation Corona Borealis, which is a "small, semicircular arc" located between the constellations Bootes and Hercules.

When you do spot the T Coronae Borealis outburst, think about this: because the star system is so far away, the outburst we'll see will have already occurred about 3,000 years earlier.

"The collapse of the Bronze Age," said Cooke. "You know, the great empires of Egypt, Troy, they were falling apart."

Venus Facts

Venus is the second planet from the Sun, and our closest planetary neighbor. It's the hottest planet in our solar system, and is sometimes called Earth's twin.

Quick Facts

Venus is the second planet from the Sun.

Venus is a bit smaller than Earth. It's 7,521 miles (12,104 kilometers) across, and Earth is 7,926 miles (12,756 kilometers).

On Venus, the Sun would rise in the west and set in the east, because Venus spins backward compared to Earth.

Except for Earth, Venus has by far the fewest impact craters of any rocky planet.

Venus is named for the ancient Roman goddess of love and beauty, who was known as Aphrodite to the ancient Greeks. Most features on Venus are named for women.

Introduction

Venus is the second planet from the Sun, and Earth's closest planetary neighbor. Venus is the third brightest object in the sky after the Sun and Moon. Venus spins slowly in the opposite direction from most planets.

Venus is similar in structure and size to Earth, and is sometimes called Earth's evil twin. Its thick atmosphere traps heat in a runaway greenhouse effect, making it the hottest planet in our solar system with surface temperatures hot enough to melt lead. Below the dense, persistent clouds, the surface has volcanoes and deformed mountains.

How Venus Got Its Name

The ancient Romans could easily see seven bright objects in the sky: the Sun, the Moon, and the five brightest planets: Mercury, Venus, Mars, Jupiter, and Saturn. They named the objects after their most important gods.

Venus is named for the ancient Roman goddess of love and beauty, who was known as Aphrodite to the ancient Greeks. Most features on Venus are named for women. It’s the only planet named after a female god.

Potential for Life

Thirty miles up (about 50 kilometers) from the surface of Venus temperatures range from 86 to 158 Fahrenheit (30 to 70 Celsius). This temperature range could accommodate Earthly life, such as “extremophile” microbes. And atmospheric pressure at that height is similar to what we find on Earth’s surface.

At the tops of Venus’ clouds, whipped around the planet by winds measured as high as 224 mph (360 kph), we find another transformation. Persistent, dark streaks appear. Scientists are so far unable to explain why these streaks remain stubbornly intact, even amid hurricane-force winds. They also have the odd habit of absorbing ultraviolet radiation.

The most likely explanations focus on fine particles, ice crystals, or even a chemical compound called iron chloride. Although it's much less likely, another possibility considered by scientists who study astrobiology is that these streaks could be made up of microbial life, Venus-style. Astrobiologists note that ring-shaped linkages of sulfur atoms, known to exist in Venus’ atmosphere, could provide microbes with a kind of coating that would protect them from sulfuric acid. These handy chemical cloaks would also absorb potentially damaging ultraviolet light and re-radiate it as visible light.

Some of the Russian Venera probes did, indeed, detect particles in Venus’ lower atmosphere about a micron in length – roughly the same size as a bacterium on Earth.

None of these findings provide compelling evidence for the existence of life in Venus’ clouds. But the questions they raise, along with Venus’ vanished ocean, its violently volcanic surface, and its hellish history, make a compelling case for missions to investigate our temperamental sister planet. There is much, it would seem, that she can teach us.

Size and Distance

Venus orbits the Sun from an average distance of 67 million miles (108 million kilometers), or 0.72 astronomical units. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight about six minutes to travel from the Sun to Venus.

Earth's nearness to Venus is a matter of perspective. The planet is nearly as big around as Earth. Its diameter at its equator is about 7,521 miles (12,104 kilometers), versus 7,926 miles (12,756 kilometers) for Earth. From Earth, Venus is the brightest object in the night sky after our own Moon. The ancients, therefore, gave it great importance in their cultures, even thinking it was two objects: a morning star and an evening star. That’s where the trick of perspective comes in.

Because Venus’ orbit is closer to the Sun than ours, the two of them – from our viewpoint – never stray far from each other. The ancient Egyptians and Greeks saw Venus in two guises: first in one orbital position (seen in the morning), then another (your “evening” Venus), just at different times of the year.

At its nearest to Earth , Venus is about 24 million (about 38 million kilometers) distant. But most of the time the two planets are farther apart; Mercury, the innermost planet, actually spends more time in Earth’s proximity than Venus.

One more trick of perspective: how Venus looks through binoculars or a telescope. Keep watch over many months, and you’ll notice that Venus has phases, just like our Moon – full, half, quarter, etc. The complete cycle, however, new to full, takes 584 days, while our Moon takes just a month. And it was this perspective, the phases of Venus first observed by Galileo through his telescope, that provided the key scientific proof for the Copernican heliocentric nature of the solar system.

Orbit and Rotation

Spending a day on Venus would be quite a disorienting experience – that is, if your spacecraft or spacesuit could protect you from temperatures in the range of 900 degrees Fahrenheit (475 Celsius). For one thing, your “day” would be 243 Earth days long – longer even than a Venus year (one trip around the Sun), which takes only 225 Earth days. For another, because of the planet's extremely slow rotation, sunrise to sunset would take 117 Earth days. And by the way, the Sun would rise in the west and set in the east, because Venus spins backward compared to Earth.

While you’re waiting, don’t expect any seasonal relief from the unrelenting temperatures. On Earth, with its spin axis tilted by about 23 degrees, we experience summer when our part of the planet (our hemisphere) receives the Sun’s rays more directly – a result of that tilt. In winter, the tilt means the rays are less direct. No such luck on Venus: Its very slight tilt is only three degrees, which is too little to produce noticeable seasons.

Venus is one of only two planets in our solar system that doesn't have a moon, but it does have a quasi-satellite that has officially been named Zoozve . This object was discovered on Nov. 11, 2002, by Brian Skiff at the Lowell Observatory Near-Earth-Object Search (LONEOS) in Flagstaff, Arizona, a project funded by NASA that ended in February 2008.  

Quasi-satellites, sometimes called quasi-moons, are asteroids that orbit the Sun while staying close to a planet. A quasi-satellite’s orbit usually is more oblong and less stable than the planet's orbit. In time, the shape of a quasi-satellite’s orbit may change and it may move away from the planet. 

According to the International Astronomical Union (IAU), the organization that names space objects, Zoozve is the first-identified quasi-satellite of a major planet. Earth also has quasi-satellites, including a small asteroid discovered in 2016 . 

Based on its brightness, scientists at NASA’s Jet Propulsion Laboratory (JPL) estimate Zoozve ranges in size from 660 feet (200 meters) to 1,640 feet (500 meters) across. 

Interestingly, Zoozve also orbits relatively close to Earth but does not pose a threat to our planet. For the next 175 years, the closest Zoozve will get to Earth is in the year 2149 when it will be about 2.2 million miles (3.5 million kilometers) away, or about 9 times the distance from Earth to the Moon.  

How Zoozve Got Its Name  

After the discovery in 2002, Skiff reported his finding to the Minor Planet Center , which is funded by a Near-Earth Object (NEO) Observations Program grant from NASA’s Planetary Defense Coordination Office . At that time, it was given the provisional name 2002 VE68. Skiff said he didn’t realize the asteroid’s importance and forgot about the object until a radio show host reached out to him in 2023 about naming it Zoozve. 

Soon after Skiff’s discovery, a team of astronomers, including Seppo Mikkola with the University of Turku in Finland and Paul Wiegert with the University of Western Ontario in London, determined that the object was the first of its kind to be discovered. They think that Zoozve may have been a companion to Venus for at least 7,000 years, and that Earth’s gravity helped push Zoozve into its present orbit. 

The name Zoozve comes from a child's poster of the solar system. The artist, Alex Foster, saw “2002 VE68” on a list of solar system objects, wrote down “2002 VE,” and then misread his own handwriting as “Zoozve.”  

Latif Nasser, co-host of the WNYC Studios show Radiolab, tracked down the source of the mistake with the help of Liz Landau , a NASA senior communications specialist. Nasser suggested that Skiff request that the IAU officially name the asteroid Zoozve. Skiff agreed, and the name Zoozve was approved in February 2024. 

Venus has no rings.

A critical question for scientists who search for life among the stars: How do habitable planets get their start? The close similarities of early Venus and Earth, and their very different fates, provide a kind of test case for scientists who study planet formation. Similar size, similar interior structure, both harboring oceans in their younger days. Yet one is now an inferno, while the other is the only known world to host abundant life. The factors that set these planets on almost opposite paths began, most likely, in the swirling disk of gas and dust from which they were born. Somehow, 4.6 billion years ago that disk around our Sun accreted, cooled, and settled into the planets we know today. Better knowledge of the formation history of Venus could help us better understand Earth – and rocky planets around other stars.

If we could slice Venus and Earth in half, pole to pole, and place them side by side, they would look remarkably similar. Each planet has an iron core enveloped by a hot-rock mantle; the thinnest of skins forms a rocky, exterior crust. On both planets, this thin skin changes form and sometimes erupts into volcanoes in response to the ebb and flow of heat and pressure deep beneath.

On Earth, the slow movement of continents over thousands and millions of years reshapes the surface, a process known as “plate tectonics.” Something similar might have happened on Venus early in its history. Today a key element of this process could be operating: subduction, or the sliding of one continental “plate” beneath another, which can also trigger volcanoes. Subduction is believed to be the first step in creating plate tectonics.

NASA’s Magellan spacecraft, which ended a five-year mission to Venus in 1994, mapped the broiling surface using radar. Magellan saw a land of extreme volcanism – a relatively young surface, one recently reshaped (in geologic terms), and chains of towering mountains.

The Soviet Union sent a series of probes to Venus between 1961 and 1984 as part of its Venera program (Venera is Russian for Venus). Ten probes made it to the surface, and a few functioned briefly after landing. The longest survivor lasted two hours; the shortest, 23 minutes. Photos snapped before the landers fried show a barren, dim, and rocky landscape, and a sky that is likely some shade of sulfur yellow.

Volcanoes and tectonic forces appear to have erased most traces of the early surface of Venus. Newer computer models indicate the resurfacing may have happened piecemeal over an extended period of time. The average age of surface features could be as young as 150 million years, with some older surfaces mixed in.

Venus has valleys and high mountains dotted with thousands of volcanoes. Its surface features – most named for both real and mythical women – include Ishtar Terra, a rocky, highland area around the size of Australia near the north pole, and an even larger, South-America-sized region called Aphrodite Terra that stretches across the equator. One mountain reaches 36,000 feet (11 kilometers), higher than Mt. Everest. Notably, except for Earth, Venus has by far the fewest impact craters of any rocky planet.

Other notable features of the Venus landscape include:

• A volcanic crater named Sacajawea for Lewis and Clark’s Native American guide.
• A deep canyon called Diana for the Roman goddess of the hunt.
• “Pancake” domes with flat tops and steep sides, as wide as 38 miles (62 kilometers), likely formed by the extrusion of highly viscous lava.
• “Tick” domes, odd volcanoes with radiating spurs that, from above, make them look like their blood-feeding namesake.
• Tesserae, terrain with intricate patterns of ridges and grooves that suggest the scorching temperatures make rock behave in some ways more like peanut butter beneath a thin and strong chocolate layer on Venus.

Venus’ atmosphere is one of extremes. With the hottest surface in the solar system, apart from the Sun itself, Venus is hotter even than the innermost planet, charbroiled Mercury. The atmosphere is mostly carbon dioxide – the same gas driving the greenhouse effect on Venus and Earth – with clouds composed of sulfuric acid. And at the surface, the hot, high-pressure carbon dioxide behaves in a corrosive fashion. But higher up in the atmosphere, temperatures and pressure begin to ease.

Magnetosphere

Even though Venus is similar in size to Earth and has a similar-sized iron core, the planet does not have its own internally generated magnetic field. Instead, Venus has what is known as an induced magnetic field. This weak magnetic field is created by the interaction of the Sun's magnetic field and the planet's outer atmosphere. Ultraviolet light from the Sun excites gases in Venus' outermost atmosphere; these electrically excited gases are called ions, and thus this region is called the ionosphere (Earth has an ionosphere as well). The solar wind – a million-mile-per-hour gale of electrically charged particles streaming continuously from the Sun – carries with it the Sun's magnetic field. When the Sun's magnetic field interacts with the electrically excited ionosphere of Venus, it creates or induces, a magnetic field there. This induced magnetic field envelops the planet and is shaped like an extended teardrop, or the tail of a comet, as the solar wind blows past Venus and outward into the solar system.

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Comet 12P/Pons-Brooks, aka the 'Devil Comet' is visible this week. Here's how to spot it

Science Comet 12P/Pons-Brooks, aka the 'Devil Comet' is visible this week. Here's how to spot it

This week is the best time for Australians to see a comet that won't be back again for 71 years — almost a whole lifetime.

The so-called "Devil Comet", or 12P/Pons–Brooks has already been visible to Northern Hemisphere viewers, but it's just become visible in the southern sky.

So, grab some binoculars and a camera and find somewhere where you can view the night sky without too much light pollution.

"There's been some astonishingly beautiful photos coming out on social media of the comet taken from the Northern Hemisphere near the Andromeda Galaxy," Jonti Horner, an astronomer with the University of Southern Queensland, says.

In the Southern Hemisphere, we've had to wait a bit longer for the comet to arrive as it moves into our part of the sky, but it should be at its brightest this weekend.

And then you   should be able to watch it over the next few weeks as it travels back into the far Solar System

It's worth getting somewhere dark to try and catch a glimpse of the comet, as it won't be back for another 70 years from now.

12P/Pons-Brooks is a Halley-type comet. Just like Halley's comet, it only comes close to Earth every few decades — Halley's takes 75 years, compared to 12P/Pons-Brooks's 71-year orbit. 

Despite its ominous name, there's no threat to Earth  — it's much too far away to hit us.

The comet's closest approach to Earth will be on June 2nd, reaching within 231 million kilometres of the planet — about 1.5 times the distances from the Earth to the Sun.  

When is the best time to see it?

If you're a keen stargazer, the most important date to put in your calender to be able to see the comet is April 21.

This is when the comet will be closest to the Sun (or perihelion) and at its brightest. It will reach a "magnitude" — a logarithmic measurement of brightness used by astronomers — of around 4.5.  

This is enough to see with the naked eye, but less bright than the brightest stars in the sky, which have a magnitude of -1. 

Professor Horner says the comet will "look like a bit of a fuzzy blob" to the naked eye, and its tail may also be visible in dark locations.

"That's with the caveat that there is a famous saying: 'Comets are like cats — they've got tails and they do what they want.'"

Why is it called the 'Devil Comet'?

While most comets are made up of dust, rock, ice and gas, researchers believe 12P/Pons–Brooks is a cryovolcanic comet. This means the ice, dust and gas erupt when the Sun's heat increases pressure on the inside of the comet. 

"As it's been coming in towards the Sun and heating up, it's been periodically giving out bursts or explosions of activity, throwing gas and dust out and then slowing down again," Professor Horner says.

"[Over] the last 12 months or so it keeps burping, it keeps having outbursts."

At one stage, the outbursts caused the comet to look like it had two tails, giving it a horned appearance. 

Unfortunately, stargazers are unlikely to see the horns now, as recent outbursts have given the comet a more conventional appearance.

It's hard to measure how large the comet is from so far away, and therefore how large the outbursts are, but estimates have put 12P/Pons-Brooks at about 17 kilometres on it's longest side.  

We do know that these bright, cryovolcanic outbursts may get more violent as the comet approaches the Sun.

But Professor Horner says the outbursts themselves will actually appear less bright, due to the relative increase in brightness of sunlight striking the comet.

This makes it hard to predict how bright the comet will appear to viewers on Earth, he adds.

"There's a chance that the comet will be a bit brighter than predicted or equally, it could be a bit fainter than predicted."

How to see 12P/Pons-Brooks

Astronomers suggest you look for the comet just after sunset , as it will be visible close to the western horizon near Jupiter. 

Although the advice varies depending on your location around Australia, about 60 minutes after sunset is the comet-viewing sweet spot, when it's dark enough to see the stars, and 12P/Pons-Brooks itself isn't too low on the horizon.

"Go and find somewhere dark, away from city lights," advises Donna Burton, an astronomer at the Milroy Observatory. 

She suggests using a free app like Star Walk or Night Sky as "they'll show you exactly where it is".

"You don't need people like me to teach you how to find things in the sky anymore."

Although the comet will be visible with the naked eye, Ms Burton suggests taking a pair of binoculars just in case, as you'll be more likely to see the tail and other features of the comet. 

"It's still bright enough to see with your naked eye. But it's not going to be super-bright like some media outlets are making it out to be."

More comet watching on the horizon

While you won't want to miss checking out 12P/Pons-Brooks before it sails off for another 71 years, there might be another comet on the horizon. 

Comet C/2023 A3 (Tsuchinshan-ATLAS) was discovered last year, and it's already got astronomers excited.

According to their models, it will come within just 59 million kilometres of the Sun by September this year. That's twice as close to the Sun as 12P/Pons-Brooks will come this time around.

Even better, the comet will be best seen in the Southern Hemisphere because of the time of year and position of the comet entering the inner Solar System. 

It's already quite bright even out past Jupiter, so if it stays on track we could be in for a treat when it arrives. 

"I'm cautiously optimistic. It's behaving really well and could become as much 100 times brighter than Pons-Brooks," Professor Horner says.

"But it's a comet we've never seen before, it's never come through the inner Solar System. It's what we'd call a long period comet. And they're even more notorious for being hard to predict."

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• Science and Technology

Scientists solved the 70-year-old mystery of an insect's invisibility coat that can manipulate light

• Leafhoppers are the only species that secrete brochosomes: rare nanoparticles with invisibility properties.
• But for the first time, a group of scientists has created their own synthetic brochosomes.
• They hope their brochosomes will one day be used for invisible cloaking devices and other technologies.

We tend to think of invisibility cloaks as science fiction . But one group of scientists has taken a big step toward making them a reality.

For the first time, scientists at Pennsylvania State University have created synthetic replicas of brochosomes, naturally occurring nanoparticles that could one day be used to make invisibility cloaking devices .

Invisibility cloaking isn't the only application for synthetic brochosomes. In the next few years, they could find their way into a range of commercial applications — from solar energy to pharmaceuticals, according to lead investigator Tak Sing Wong, professor of mechanical engineering and biomedical engineering at Penn State.

Solving a 70-year-long geometric mystery

Brochosomes are bucky-ball-shaped, hollow nanoparticles covered in holes — known as through-holes — that go all the way through them. This complex structure allows them to absorb or scatter certain wavelengths of light, depending on the size of the brochosome and its holes.

The only place in the world where you can find naturally occurring brochosomes is on the back of a leafhopper — a common backyard insect . Their brochosome coats were first discovered in the 1950s, and they probably help them blend into their surroundings.

Scientists aren't sure why leafhoppers secrete and cover themselves in brochosomes. Until now, they didn't even understand the purpose of the nanoparticles' intricate geometry.

"This is really the first study to understand how the brochosome's complex geometry interacts with light," Wong said.

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To reach that understanding, Wong and his colleagues had to figure out how to make a replica of a brochosome. After almost a decade of research, they managed to 3D print the world's first synthetic brochosomes.

The invisibility properties of brochosomes

There are two important elements of brochosome geometry: the diameter of the particle, and the diameter of its through-holes.

If a wavelength of light is the same length as the diameter of the brochosomes, it will be scattered in all directions when it hits the particle. But if the wavelength of light is the same length as the diameter of the brochosomes' through-holes, it will pass through the particle and get absorbed by it.

This absorption coupled with light-scattering means that brochosomes have very limited light reflection — and can be invisible over certain electromagnetic ranges. Covering an object in them could, in theory, work as an invisibility cloak.

The beauty of synthetic brochosomes is that they could be made at different sizes, and thus tailored to absorb and scatter different wavelengths across the electromagnetic spectrum . That means that engineers can customize brochosomes for specific functions, such as invisibility to infrared radiation to help with military defense.

In fact, Wong's brochosomes are the right size to do that. They're about 40 to 50 times larger than naturally occurring ones, and they only interact with infrared radiation. Wong's future research will partly focus on making smaller synthetic brochosomes to target the shorter end of the electromagnetic spectrum.

The commercial potential of brochosomes

Although Wong's synthetic brochosomes mark a major step towards invisibility-cloaking technology, scientists are still decades away from bringing anything to market.

"I think in my lifetime, it's possible," said Hao Xin , a professor of electrical and computer engineering and physics at the University of Arizona who was not involved in the study. It will take at least 50 years, he said.

But in just three to five years, Wong hopes to produce brochosomes on a large enough scale to use them in pigments, pharmaceuticals, and solar panels .

For example, titanium oxide, a white pigment that's used in everything from candy to sunscreen , was recently banned as a food additive by the European Union. Wong believes that brochosomes could eventually replace titanium oxide in foods like candy and coffee creamers.

"Depending on our imagination, I think there are many cool applications that can come out of brochosomes," Wong said.

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How to see the northern lights in alaska in 2024.

If seeing the northern lights in Alaska is on your bucket list, this is the year to do it.

How to See the Northern Lights in Alaska

Chris McLennan | Courtesy of State of Alaska

The National Oceanic and Atmospheric Administration says solar activity is intensifying and will peak (at a higher level than previously thought) in 2024. This means travelers will have more opportunities to see the northern lights around the world .

If you're considering a trip to Alaska to witness this atmospheric phenomenon, read on to discover the best months to visit as well as a variety of viewing options.

The best time to see the northern lights in Alaska

Where to see the northern lights in alaska, northern lights alaska cruises.

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Courtesy of Travel Alaska

According to the Alaska Travel Industry Association, the best time to see the northern lights is typically from Aug. 21 to April 21 , also known as the Aurora Season. While the aurora can appear at any time of night, 10 p.m. to 2 a.m. are the prime viewing hours.

The winter solstice – which is the shortest day of the year, typically falling between Dec. 20 and 23 – is a particularly good time to be in Alaska for the northern lights. This day affords less daylight and more time to spot the aurora. In parts of Alaska, the amount of daylight during the winter solstice can range from around six hours in Anchorage to less than four further north in Fairbanks. Up in remote Utqiagvik (formerly called Barrow), about 320 miles north of the Arctic Circle, there are roughly 67 days of darkness from Nov. 18 to Jan. 23, resulting in even more opportunities to spot the northern lights.

Of course, 2024 is expected to be a little different. Scientists say solar activity will reach its peak from January to October, expanding the typical time frame for spotting the aurora. Ahead of and during your visit, experts recommend utilizing these forecasting resources:

• Aurora Tracker: Whether you're a beginner or an experienced aurora chaser, you'll appreciate Explore Fairbanks' real-time Aurora Tracker . This online reference shows up-to-the-minute information on the temperature, weather and likelihood of catching the northern lights in Fairbanks. Much of the data comes from one of the world's foremost aurora research centers, the Geophysical Institute at the University of Alaska–Fairbanks . To further assist in your search, you can also download the My Aurora Forecast & Alerts app on your smartphone.
• Aurora Forecast: For other parts of the state, the Geophysical Institute website's Aurora Forecast has daily forecasts of geomagnetic activity up to three days in advance and taken at three-hour intervals. There's also a summation on the webpage of whether the aurora will be active – or not – and where you'll find the best visibility in Alaska.

Courtesy of Aurora Villa

Below are the top destinations to consider when deciding where to see the northern lights in Alaska.

Fairbanks, known as the Golden Heart of Alaska, sits at 65 degrees north latitude, making it an excellent choice for aurora hunters, especially first-timers. It's easily accessible and offers plenty of accommodations , restaurants and other unique attractions . You can also be outside of Fairbanks within minutes to find excellent northern lights viewing locales.

Your chances of seeing the aurora display are excellent as the city sits where the activity of the polar lights is concentrated – under the ring-shaped zone known as the auroral oval. Local experts say that on clear evenings when the sky is very dark, you should be able to witness the skies light up on an average of four out of five nights in Fairbanks.

Where to stay:

• Aurora Villa : Located on the outskirts of Fairbanks, Aurora Villa offers luxurious guest rooms with floor-to-ceiling windows for viewing the northern lights in a cozy private space. The modern wooden cabin sits on 10 acres surrounded by forested hills, yet it's close enough to the city (less than 15 miles northeast) to explore all that Fairbanks has to offer.
• Pike's Waterfront Lodge : Located along the Chena River in Fairbanks, just minutes from Fairbanks International Airport, this property offers 180 rooms and 28 cabins for aurora-hunting adventurers. As a guest of the lodge, you can request that the front desk alert you when the northern lights appear – no matter the time of day or night. Pike's Waterfront Lodge also offers amenities to keep guests warm while viewing the light show outdoors.

Talkeetna sits about 115 miles north of Anchorage in south-central Alaska, at the base of Denali, the tallest mountain peak in North America. With its old clapboard buildings, log cabins and roadhouse dating back to 1917, this historic town offers a lot of outdoor fun beyond chasing the aurora. Main Street is filled with galleries, shops, restaurants and a brewery. The quirky village, once a former mining town, was the inspiration for the imaginary borough of Cicely in the TV show "Northern Exposure."

If you visit in December, check out the festivities at the monthlong Winterfest. This event features a parade of lights, a tree lighting ceremony and the Taste of Talkeetna food festival, plus entertaining events like the Bachelor Auction and the Wilderness Woman Competition.

When it's time to look up in the sky for the lights, local aurora hunters recommend heading out of town to Christiansen Lake or past the airport on Beaver Road. If you prefer to stay close by, look north into the sky toward Denali from Talkeetna Riverfront Park.

• Talkeetna Alaskan Lodge : Book a Mountain View room for views of Denali and the Alaskan Range. The cozy lodge offers multiple dining venues, including the award-winning Foraker Restaurant.
• Talkeetna Lakeside Cabins : These cabins provide peace and quiet on a private lake just 12 miles from Talkeetna.

Denali National Park

Denali National Park is another spectacular place to view the northern lights in Alaska – not to mention one of the top tourist attractions in the U.S. The National Park Service says almost everywhere within the park is free from city light pollution, so if the conditions are right (meaning that's it's clear and dark enough), you should be able to see the aurora borealis, especially when looking toward the northern horizon.

However, when wintertime rolls around – from September or October through April – it's more difficult to access parts of the park, even though it's open year-round. Keep in mind, too, that the lodges closest to the park are typically closed from mid-September to mid-May.

Where to stay: Located less than 15 miles from the Denali National Park entrance, the Aurora Denali Lodge offers year-round accommodations equipped with queen-sized beds, smart TVs and private bathrooms. Rates at the lodge include a continental breakfast, free Wi-Fi, free parking and complimentary hot drinks. What's more, the property says visitors can expect plenty of wildlife sightings, such as bears, moose, lynxes, owls and snowshoe hares, just outside your door.

Coldfoot Camp

Coldfoot Camp is situated above the Arctic Circle in the Brooks Mountain Range, near the Gates of the Arctic National Park and Preserve and the Arctic National Wildlife Refuge. The remote wilderness destination is ideal for aurora viewing since it sits directly under the auroral oval. It's also the perfect locale for backcountry snowshoeing, wildlife viewing and dog mushing.

Where to stay: The Inn at Coldfoot Camp offers rustic accommodations located in trailers that once housed Alaskan pipeline workers. The rooms include two twin beds and a private bathroom and shower. Guests can dine at the on-site Trucker's Cafe, which offers breakfast and dinner buffets in the summer months and all-day a la carte dining in the winter. When you're ready for a cold one at the end of the day, check out the Frozen Foot Saloon and order an Alaska-brewed beer.

If you prefer camping and have your own gear , you can camp free of charge on the property during the summer months. Coldfoot Camp also hosts a selection of year-round Arctic adventures and excursions, including a trip to the nearby village of Wiseman for aurora viewing.

This remote wilderness retreat has just 13 full-time residents. Wiseman is located in Alaska's Brooks Range, about 15 miles north of Coldfoot Camp, 60 miles north of the Arctic Circle and 270 miles from Fairbanks. The community sits directly under the auroral oval, making it one of the best places in Alaska to view the northern lights. You can expect to see the spectacle in the sky in Wiseman about 250 nights a year, especially between late August and mid-April.

• Arctic Hive : Arctic Hive has the distinction of being the northernmost yoga studio in the U.S. A common fiberglass lodge allows guests to gather for cooking and meals, and meditation, educational gatherings and other activities are hosted in a geodesic dome. Arctic Hive also offers retreats that include northern lights viewing opportunities in February and March.
• Arctic Getaway : This bed-and-breakfast sits between the middle fork of the Koyukuk River and Wiseman Creek, offering three cabins. While here, you can learn what it's like to homestead in Alaska above the Arctic Circle and enjoy outdoor activities like dog sled rides across the vast wilderness, cross-country skiing , pack rafting and flightseeing by bush plane.
• Boreal Lodging : Reachable by vehicle, Boreal Lodging has several rental options, ranging from lodge rooms to larger cabins with living areas and kitchens.

Located in western Alaska overlooking the Norton Sound of the Bering Sea, Nome is the ending point for the more than 1,000-mile, 51-year-old Iditarod Trail Dog Sled Race in March. Once the most populated city in Alaska, Nome had almost 20,000 residents and an average of 1,000 new people arriving daily during the height of the gold rush in 1899. Nome is a little quieter now, with a population of less than 4,000 residents.

Where to stay: Some of the best spots for viewing the aurora are at the end of town, where the 52-room Aurora Inn & Suites is located. The hotel conveniently offers car rentals on-site.

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Situated on the banks of the Arctic Ocean, Utqiagvik is the northernmost city in the U.S. The town, formerly known as Barrow, changed its name in 2016 back to Utqiagvik, its traditional Inupiaq name. Utqiagvik is only accessible by plane: Alaska Airlines and other regional carriers offer service from both Anchorage and Fairbanks.

Where to stay: For accommodations, make reservations at a hotel named for its location – the Top of the World Hotel . The property's comfortable rooms offer views of the Arctic Ocean, and the on-site restaurant, Niggivikput (meaning "our place to eat"), serves traditional local dishes like reindeer soup. While you may be there for aurora hunting, don't miss the excellent wildlife-viewing opportunities: You may see polar bears, caribou, foxes, bearded seals, whales, walruses, migratory birds and the great snowy owl on the tundra.

Borealis Basecamp

One of the best glamping destinations in the U.S. , Borealis Basecamp is a remote 100-acre property that sits within a boreal forest 25 miles north of Fairbanks. The property features 20 individual igloos, resembling those you'd find at Arctic research stations and on polar expeditions, as well as five glass cubes. All accommodations allow guests to gaze up at the aurora and the starry night sky while snuggled up in bed. You'll also enjoy many amenities you'd find in a hotel, including full bathrooms with toiletries and a selection of coffee, hot cocoa and tea.

Choose from a variety of packages that include accommodations and activities like dog-sledding, UTV tours, helicopter sightseeing experiences and more.

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One of the best times to cruise to Alaska is during the aurora season. Aurora season sailings to Alaska are available with the following cruise lines this year.

If you're interested in excursions for aurora viewing, look for a line that offers cruisetours, such as Holland America. These tours offer the best of both worlds, giving you time on land and at sea to view the dancing night sky. Holland America's cruisetours range from overnight stays just 2 miles from Denali National Park at the McKinley Chalet Resort to a domed luxury train ride through Alaska's backcountry on the McKinley Explorer. On a Tundra Wilderness Tour in Denali, look for Alaska's "Big Five": grizzly bears, moose, caribou, Dall sheep and wolves. Just keep in mind that none of the above cruise lines can guarantee you'll see the northern lights during your journey.

The best northern lights tours in Alaska

Jody Overstreet | Courtesy of State of Alaska

If you want to experience the aurora borealis by joining a tour group, you'll find a variety of options led by expert guides and granting you easier access to many of the state's remote destinations, often with other activities included. (Just be aware that, on any tour or excursion, there's no way to guarantee that the aurora will be visible.) These are some of the best northern lights tours in Alaska:

Arctic Dog Adventure Co.: Aurora Overnight Tour

Dog-sledding is one of the top winter activities in Alaska, and you can choose to do it by day or night. If you want to experience an Alaska dog-sledding adventure while chasing the aurora, book a once-in-a-lifetime experience with Arctic Dog's Aurora Overnight Tour. Highlights of this two-day, one-night excursion – which starts in Fairbanks – are dog mushing your own sled team and glamping in a heated tent under an aurora-filled sky. Other features of the tour include cold weather gear, a photography lesson and Alaska-inspired meals.

Alaska Wildlife Guide: Northern Lights & Murphy Dome Tour

Located around 20 miles northwest of the city, Murphy Dome is regarded as one of the best places to watch the northern lights in Fairbanks at nearly 3,000 feet above sea level. This location, once home to Murphy Dome Air Force Station with as many as 250 personnel stationed at the base, now houses a long-range radar station that detects military air threats from overseas.

Alaska Wildlife Guide leads 5.5-hour northern lights tours to Murphy Dome, typically from late August to early April – you can check with the company for day-to-day tour availability. Excursion prices include round-trip transportation from Fairbanks, 360-degree views of the north-facing sky, hot beverages and bottled water – in addition to (hopefully) hours of memorable aurora viewing.

Alaska Wildlife Guide: Northern Lights & Arctic Circle Tour

This full-day (14-hour) excursion, also offered by Alaska Wildlife Guide, begins in Fairbanks and crosses the Arctic Circle into Alaska's vast and remote wilderness. The tour includes a drive along the more than 800-mile Trans-Alaskan Pipeline and a half-mile walk along the loop at Finger Mountain with views overlooking the Kanuti Flats (depending on the season). Your guide will also stop along the riverbank after crossing the Yukon River Bridge.

During the tour, you'll learn about the history of the pipeline and hear narratives around the other included stops. A snack and warm beverage are included; then, if conditions are just right, you'll have the chance to see the brilliant light show dance across the dark, clear skies before you arrive back in Fairbanks at dawn.

Alaska Journey Tours: Northern Lights (Aurora) Chasing Tour

Get picked up at your Fairbanks hotel (or meet at the Hyatt Place Fairbanks) for this three-hour northern lights tour in a heated SUV. Guides take photos of tourgoers as well as their own photos of the night sky, which are later shared with the group. Recent travelers praise this tour, and appreciate that the guides are always determined to give them the best northern lights viewing experience.

Alaska Tours: Bettles Lodge Winter Adventure

Hosted by Alaska Tours, the Bettles Lodge Winter Adventure is available January to March and August to December. This excursion includes two, three or four nights at this wilderness lodge about 35 miles north of the Arctic Circle. During the winter days, enjoy outdoor Arctic sports such as snowshoeing and cross-country skiing or stay warm indoors chatting with other guests at the Aurora Lodge. In the evenings, you can bundle up and head outside at one of the best places in Alaska to see the spectacle in the sky.

Prices include round-trip airfare between Fairbanks and Bettles, accommodations at the lodge, meals, a village tour and complimentary use of the Arctic gear (in season).

Alaska Photo Treks: Anchorage Aurora Quest

Alaska Photo Treks offers one of the best ways to see the northern lights in Anchorage – and you'll even learn how best to photograph the aurora, which can be a challenge to capture digitally or on film. This experience, the Anchorage Aurora Quest, is available nightly (when conditions are right), typically from mid-August to mid-April. The approximately six-hour guided tour with a professional photographer explains the science behind the northern lights and provides photo tips for budding aurora photographers in a small-group format. Tourgoers are picked up from their hotel by the guide at about 10 p.m. and return around 4 a.m., though that time can vary based on the aurora forecast.

On the Alaska Photo Treks website, you'll find a list of recommended camera equipment to bring. If you're using a smartphone, the tour group suggests downloading an aurora app and bringing a tripod. The company also advises that you'll be outdoors for about two hours, so you need to dress appropriately for the weather. For the best aurora viewing, the guides usually travel between one to three locations within a 70-mile radius of Anchorage. If you're in town for an extended stay, Alaska Photo Treks also offers a four-day pass for even more nocturnal viewing of the auroral activity.

Alaska Tours: Chena Hot Springs and Northern Lights

Chena Hot Springs Resort is known for its therapeutic waters and aurora-viewing opportunities. If you prefer to head out with a guide rather than on your own, book the Chena Hot Springs and Northern Lights tour with Alaska Tours. This package includes a four- to five-hour Aurora Expedition tour, four nights of accommodations, and access to resort amenities including cross-country skiing and snow machine tours.

Alaska Wildlife Guide: Northern Lights and Chena Hot Springs

Day trips are also an option for those who'd like to enjoy the resort amenities and a chance at seeing the northern lights from Chena Hot Springs. This tour offered by Alaska Wildlife Guide includes admission to the hot springs and Aurora Ice Museum as well as pickup from local hotels. Recent travelers say the tour guides are top-notch.

John Hall's Alaska: Alaska's Winter Wonders

For an extended land tour to chase the aurora – and experience Alaska's magical winter wonderland – book this bucket list eight-day adventure with John Hall's Alaska. The company's Alaska's Winter Wonders tour is offered in February and March; it features up to seven nights of northern lights viewing, as well as adventure-filled days with skiing, snowmobiling and snowshoeing. You'll also take an awe-inspiring flightseeing bush plane ride over Denali National Park, which includes a fly-by of the Foraker, Silverthorne, Hunter and Moose's Tooth peaks before landing on the Great Gorge of Ruth Glacier – the deepest in the world.

If that's not enough adventure, test your skills at dog mushing and curling or take an aerial tram ride. Travelers can also check out the local breweries or just sit back, relax and enjoy the spectacular views. Additional highlights include spending two evenings under the dancing night sky in one of the domed igloos at Borealis Basecamp, as well as aurora borealis photography lessons.

All-inclusive pricing covers accommodations, meals, luxury land and small plane transportation, fully guided service, gratuities, and baggage handling – plus a black subzero jacket to keep you warm during your Alaska adventure.

Why Trust U.S. News Travel

Gwen Pratesi is an avid travel adventurer who fell in love with Alaska on her first visit to the state many years ago. She's returned several times on land trips and by ship for year-round outdoor adventure and to chase the northern lights in one of the best places on the planet to view them. She writes about the travel and culinary industries for a variety of major publications.

You might also be interested in:

• The Top Packable Jackets
• The Top Things to Do in Alaska
• How to See the Northern Lights in Iceland
• The Best Travel Insurance Companies

Tags: Travel , Alaska Vacations , Vacation Ideas

World's Best Places To Visit

• # 1 South Island, New Zealand
• # 4 Bora Bora

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