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Paradox-Free Time Travel Is Theoretically Possible, Researchers Say

Matthew S. Schwartz

A dog dressed as Marty McFly from Back to the Future attends the Tompkins Square Halloween Dog Parade in 2015. New research says time travel might be possible without the problems McFly encountered. Timothy A. Clary/AFP via Getty Images hide caption

A dog dressed as Marty McFly from Back to the Future attends the Tompkins Square Halloween Dog Parade in 2015. New research says time travel might be possible without the problems McFly encountered.

"The past is obdurate," Stephen King wrote in his book about a man who goes back in time to prevent the Kennedy assassination. "It doesn't want to be changed."

Turns out, King might have been on to something.

Countless science fiction tales have explored the paradox of what would happen if you went back in time and did something in the past that endangered the future. Perhaps one of the most famous pop culture examples is in Back to the Future , when Marty McFly goes back in time and accidentally stops his parents from meeting, putting his own existence in jeopardy.

But maybe McFly wasn't in much danger after all. According a new paper from researchers at the University of Queensland, even if time travel were possible, the paradox couldn't actually exist.

Researchers ran the numbers and determined that even if you made a change in the past, the timeline would essentially self-correct, ensuring that whatever happened to send you back in time would still happen.

"Say you traveled in time in an attempt to stop COVID-19's patient zero from being exposed to the virus," University of Queensland scientist Fabio Costa told the university's news service .

"However, if you stopped that individual from becoming infected, that would eliminate the motivation for you to go back and stop the pandemic in the first place," said Costa, who co-authored the paper with honors undergraduate student Germain Tobar.

"This is a paradox — an inconsistency that often leads people to think that time travel cannot occur in our universe."

A variation is known as the "grandfather paradox" — in which a time traveler kills their own grandfather, in the process preventing the time traveler's birth.

The logical paradox has given researchers a headache, in part because according to Einstein's theory of general relativity, "closed timelike curves" are possible, theoretically allowing an observer to travel back in time and interact with their past self — potentially endangering their own existence.

But these researchers say that such a paradox wouldn't necessarily exist, because events would adjust themselves.

Take the coronavirus patient zero example. "You might try and stop patient zero from becoming infected, but in doing so, you would catch the virus and become patient zero, or someone else would," Tobar told the university's news service.

In other words, a time traveler could make changes, but the original outcome would still find a way to happen — maybe not the same way it happened in the first timeline but close enough so that the time traveler would still exist and would still be motivated to go back in time.

"No matter what you did, the salient events would just recalibrate around you," Tobar said.

The paper, "Reversible dynamics with closed time-like curves and freedom of choice," was published last week in the peer-reviewed journal Classical and Quantum Gravity . The findings seem consistent with another time travel study published this summer in the peer-reviewed journal Physical Review Letters. That study found that changes made in the past won't drastically alter the future.

Bestselling science fiction author Blake Crouch, who has written extensively about time travel, said the new study seems to support what certain time travel tropes have posited all along.

"The universe is deterministic and attempts to alter Past Event X are destined to be the forces which bring Past Event X into being," Crouch told NPR via email. "So the future can affect the past. Or maybe time is just an illusion. But I guess it's cool that the math checks out."

• time travel
• grandfather paradox

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Time travel for travelers? It’s tricky.

Scientific theories suggest it’s possible to travel through time. But the reality isn’t so clear.

Time travel has fascinated scientists and writers for at least 125 years. The concept feels especially intriguing now, when physical travel is limited. Here, a photo illustration of Tokyo’s Robot Restaurant captures the idea of speeding through time.

I’m stuck at home, you’re stuck at home, we’re all stuck at home. Jetting off to some fun-filled destination like we used to might not be in the cards for a little while yet. But what about travelling through time? And not just the boring way, where we wait for the future to arrive one second at a time. What if you could zip through time at will, travelling forward to the future or backward to the past as easily as pushing buttons on the dashboard of a souped-up DeLorean, just like in the movie Back to the Future ?

Time travel has been a fantasy for at least 125 years. H.G. Wells penned his groundbreaking novel, The Time Machine , in 1895, and it’s something that physicists and philosophers have been writing serious papers about for almost a century.

What really kick-started scientific investigations into time travel was the notion, dating to the closing years of the 19th century, that time could be envisioned as a dimension, just like space. We can move easily enough through space, so why not time?

At the end of the 19th century, scientists thought of time as a dimension like space, where travelers can go anywhere they want. This photo illustration of Tokyu Plaza in Tokyo’s Omotesando Harajuku evokes the feeling of visiting endless destinations.

“In space, you can go wherever you want, so maybe in time you can similarly go anywhere you want,” says Nikk Effingham, a philosopher at the University of Birmingham in the United Kingdom . “From there, it’s a short step to time machines.”

( Why are people obsessed with time travel? Best-selling author James Gleick has some ideas .)

Dueling theories

Wells was a novelist, not a physicist, but physics would soon catch up. In 1905, Albert Einstein published the first part of his relativity theory, known as special relativity . In it, space and time are malleable; measurements of both space and time depend on the relative speed of the person doing the measuring.

A few years later, the German mathematician Hermann Minkowski showed that, in Einstein’s theory, space and time could be thought of as two aspects of a single four-dimensional entity known as space-time . Then, in 1915, Einstein came up with the second part of his theory, known as general relativity . General relativity renders gravity in a new light: Instead of thinking of it as a force, general relativity describes gravity as a bending or warping of space-time.

But special relativity is enough to get us started in terms of moving through time. The theory “establishes that time is much more similar to space than we had previously thought,” says Clifford Johnson, a physicist at the University of Southern California. “So maybe everything we can do with space, we can do with time.”

Well, almost everything. Special relativity doesn’t give us a way of going back in time, but it does give us a way of going forward— and at a rate that you can actually control. In fact, thanks to special relativity, you can end up with two twins having different ages, the famous “twin paradox.”

Suppose you head off to the Alpha Centauri star system in your spaceship at a really high speed (something close to the speed of light), while your twin remains on Earth. When you come back home, you’ll find you’re now much younger than your twin. It’s counterintuitive, to say the least, but the physics, after more than a century, is rock solid.

“It is absolutely provable in special relativity that the astronaut who makes the journey, if they travel at very nearly the speed of light, will be much younger than their twin when they come back,” says Janna Levin, a physicist at Barnard College in New York . Interestingly, time appears to pass just as it always does for both twins; it’s only when they’re reunited that the difference reveals itself.

Maybe you were both in your 20s when the voyage began. When you come back, you look just a few years older than when you left, while your twin is perhaps now a grandparent. “My experience of the passage of time is utterly normal for me. My clocks tick at the normal rate, I age normally, movies run at the right pace,” says Levin. “I’m no further into my future than normal. But I’ve travelled into my twin’s future.”

( To study aging, scientist are looking to outer space .)

With general relativity, things really start to get interesting. In this theory, a massive object warps or distorts space and time. Perhaps you’ve seen diagrams or videos comparing this to the way a ball distorts a rubber sheet . One result is that, just as travelling at a high speed affects the rate at which time passes, simply being near a really heavy object—like a black hole —will affect one’s experience of time. (This trick was central to the plot of the 2014 film, Interstellar , in which Matthew McConaughey’s character spends time in the vicinity of a massive black hole. When he returns home, he finds that his young daughter is now elderly.)

To get around the “grandfather paradox,” some scientists theorize there could be multiple timelines. In these images of Nakagin Capsule Tower in Tokyo, Japan, time seems to pass at different rates.

But black holes are just the beginning. Physicists have also speculated about the implications of a much more exotic structure known as a wormhole . Wormholes, if they exist, could connect one location in space-time with another. An astronaut who enters a wormhole in the Andromeda Galaxy in the year 3000 might find herself emerging from the other end in our own galaxy, in the year 2000. But there’s a catch: While we have overwhelming evidence that black holes exist in nature—astronomers even photographed one last year—wormholes are far more speculative.

“You can imagine building a bridge from one region of space-time to another region of space-time,” explains Levin, “but it would require kinds of mass and energy that we don’t really know exist in reality, things like negative energy.” She says it’s “mathematically conceivable” that structures such as wormholes could exist, but they may not be part of physical reality.

There’s also the troubling question of what happens to our notions of cause and effect if backward time travel were possible. The most famous of these conundrums is the so-called “ grandfather paradox .” Suppose you travel back in time to when your grandfather was a young man. You kill him (perhaps by accident), which means your parent won’t be born, which means you won’t be born. Therefore, you won’t be able to travel through time and kill your grandfather.

Multiple timelines?

Over the years, physicists and philosophers have pondered various resolutions to the grandfather paradox. One possibility is that the paradox simply proves that no such journeys are possible; the laws of physics, somehow, must prevent backward time travel. This was the view of the late physicist Stephen Hawking , who called this rule the “ chronology protection conjecture .” (Mind you, he never specified the actual physics behind such a rule.)

But there are also other, more intriguing, solutions. Maybe backward time travel is possible, and yet time travelers can’t change the past, no matter how hard they try. Effingham, whose book Time Travel: Probability and Impossibility was published earlier this year, puts it this way: “You might shoot the wrong person, or you might change your mind. Or, you might shoot the person you think is your grandfather, but it turns out your grandmother had an affair with the milkman, and that’s who your grandfather was all along; you just didn’t know it.”

Which also means the much-discussed fantasy of killing Hitler before the outbreak of World War II is a non-starter. “It’s impossible because it didn’t happen,” says Fabio Costa, a theoretical physicist at the University of Queensland in Australia . “It’s not even a question. We know how history developed. There is no re-do.”

In fact, suggests Effingham, if you can’t change the past, then a time traveler probably can’t do anything . Your mere existence at a time in which you never existed would be a contradiction. “The universe doesn’t care whether the thing you’ve changed is that you’ve killed Hitler, or that you moved an atom from position A to position B,” Effingham says.

But all is not lost. The scenarios Effingham and Costa are imagining involve a single universe with a single “timeline.” But some physicists speculate that our universe is just one among many . If that’s the case, then perhaps time travelers who visit the past can do as they please, which would shed new light on the grandfather paradox.

( The Big Bang could have led to the creation of multiple universes, scientists say .)

“Maybe, for whatever reason, you decide to go back and commit this crime [of killing your grandfather], and so the world ‘branches off’ into two different realities,” says Levin. As a result, “even though you seem to be altering your past, you’re not really altering it; you’re creating a new history.” (This idea of multiple timelines lies at the heart of the Back to the Future movie trilogy. In contrast, in the movie 12 Monkeys , Bruce Willis’s character makes multiple journeys through time, but everything plays out along a single timeline.)

More work to be done

What everyone seems to agree on is that no one is building a time-travelling DeLorean or engineering a custom-built wormhole anytime soon. Instead, physicists are focusing on completing the work that Einstein began a century ago.

After more than 100 years, no one has figured out how to reconcile general relativity with the other great pillar of 20th century physics: quantum mechanics . Some physicists believe that a long-sought unified theory known as quantum gravity will yield new insight into the nature of time. At the very least, says Levin, it seems likely “that we need to go beyond just general relativity to understand time.”

Meanwhile, it’s no surprise that, like H.G. Wells, we continue to daydream about having the freedom to move through time just as we move through space. “Time is embedded in everything we do,” says Johnson. “It looms large in how we perceive the world. So being able to mess with time—I’m not surprised we’re obsessed with that, and fantasize about it.”

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What is TravelTime?

Travel Time Map Generator & Isochrones

I know i can get from a to b by public transport within my selected time, but it's not showing up.

If you're using public transport to do your analysis, it can look like we don't include a specific transit line. But it is rare that we have forgotten to add it! We have a full data team collecting transport data, and they're rarely caught out. It's usually due to understanding how we calculate travel time catchments. We build the area to include:

• Walking to the station platform
• Waiting for the next available departure
• Time spent boarding the train
• Giving enough time to take the A to B journey
• Depart on the station on the other side.

That means if you set your max travel time at 30 minutes, and the train journey you think should be included takes 28 minutes, it probably won't show up, because the other steps push it over the max 30 min limit. Try adding an extra 5-10 minutes to your max catchment area and see if this helps! Understand how we built our public transport model

You can't drive that far / you can drive much further than that

We recommend that you do a little experiment.

• Open another mapping app of your choice and enter an A to B route
• Select a departure time for tomorrow.

The average mapping provider gives very vague driving estimations. It's not uncommon to see a journey estimation between 30 minutes up to 2 hours. That's a lot of buffer room!

Our driving model only returns one singular best possible time estimate. We do this using our purpose-built driving model. Explore how we've built our driving model.

Still not convinced?

You can explain your data issue to us here and we can help you out. Please include in your request whether you're using the API for commercial or personal purposes.

About this tool

This demo was built to showcase the TravelTime API. To use the full capabilities of the API you will need coding skills, or experience with one of our integrations: QGIS, Alteryx or ArcGIS. Access to the API gives you larger travel time catchment areas, more transport mode options and large request volumes. Access the developer playground here.

What is a travel time map?

Our map tool allows you to create a 'How far can I go map' by transport mode and time limit. For example someone can ask how far can I drive from my home in 30 minutes. The tool outputs shapes, also known as travel time isochrones visualise where's reachable. Sometimes these shapes are incorrectly labelled as a 'travel time radius map'. A radius is always just a circular shape, but a travel time shape is completely unique as it analyses all locations reachable using a specific mode of transport.

How to create a drive time radius map or other modes

• Select a start location
• Select a maximum travel time limit
• Select a mode of transport, for example driving
• Voila! There's your driving radius map

Use cases for consumers

• Create a commute time map so you can see where to live based on commute time.
• How far can i travel in a given time: compare transport coverage for different areas.
• Create a drive time radius map: explore how far you can travel on a road trip.

Use cases for businesses

• Travel time mapping up to 4 hours & cross reference other data sets in GIS such as population data
• Site selection analysis: analyse the best location to locate a business by adding thousands of analysis points
• Create a distance matrix or travel time matrix & calculate travel times from thousands of origins to thousands of destinations
• Network analysis / travelling salesman problem: use spatial analytics to solve routing problems
• Commute time map - plot thousands of employee commute times for an office relocation

This web page is a limited demo that can do the following:

• Create up to 3 time polygons visualising where's reachable within 2 hours or less. Our API can create large travel time areas, talk to sales.
• Calculate travel times from an origin to various points of interest - in this demo we use points from Foursquare Give A to B routing details

Full access

We provide full analysis by all transport modes and all travel time areas in our full service. You can access this by:

• Book a demo
• Trial TravelTime API
• Trial QGIS Plugin
• Trial ArcGIS Pro Add-In
• Trial Alteryx Macros

Problem with the data?

Create a Travel Time Map

Draw a travel time area or make your own commute time map.

• See 'How far can I get' in X minutes
• Create a drive time map or any other transport mode
• Overlap many shapes & highlight overlap area
• Search points of interest within the area
• Get A to B routing details

Is time travel possible? Why one scientist says we 'cannot ignore the possibility.'

A common theme in science-fiction media , time travel is captivating. It’s defined by the late philosopher David Lewis in his essay “The Paradoxes of Time Travel” as “[involving] a discrepancy between time and space time. Any traveler departs and then arrives at his destination; the time elapsed from departure to arrival … is the duration of the journey.”

Time travel is usually understood by most as going back to a bygone era or jumping forward to a point far in the future . But how much of the idea is based in reality? Is it possible to travel through time? 

Is time travel possible?

According to NASA, time travel is possible , just not in the way you might expect. Albert Einstein’s theory of relativity says time and motion are relative to each other, and nothing can go faster than the speed of light , which is 186,000 miles per second. Time travel happens through what’s called “time dilation.”

Time dilation , according to Live Science, is how one’s perception of time is different to another's, depending on their motion or where they are. Hence, time being relative. 

Learn more: Best travel insurance

Dr. Ana Alonso-Serrano, a postdoctoral researcher at the Max Planck Institute for Gravitational Physics in Germany, explained the possibility of time travel and how researchers test theories. 

Space and time are not absolute values, Alonso-Serrano said. And what makes this all more complex is that you are able to carve space-time .

“In the moment that you carve the space-time, you can play with that curvature to make the time come in a circle and make a time machine,” Alonso-Serrano told USA TODAY. 

She explained how, theoretically, time travel is possible. The mathematics behind creating curvature of space-time are solid, but trying to re-create the strict physical conditions needed to prove these theories can be challenging. 

“The tricky point of that is if you can find a physical, realistic, way to do it,” she said. 

Alonso-Serrano said wormholes and warp drives are tools that are used to create this curvature. The matter needed to achieve curving space-time via a wormhole is exotic matter , which hasn’t been done successfully. Researchers don’t even know if this type of matter exists, she said.

“It's something that we work on because it's theoretically possible, and because it's a very nice way to test our theory, to look for possible paradoxes,” Alonso-Serrano added.

“I could not say that nothing is possible, but I cannot ignore the possibility,” she said. 

She also mentioned the anecdote of  Stephen Hawking’s Champagne party for time travelers . Hawking had a GPS-specific location for the party. He didn’t send out invites until the party had already happened, so only people who could travel to the past would be able to attend. No one showed up, and Hawking referred to this event as "experimental evidence" that time travel wasn't possible.

What did Albert Einstein invent?: Discoveries that changed the world

Just Curious for more? We've got you covered

USA TODAY is exploring the questions you and others ask every day. From "How to watch the Marvel movies in order" to "Why is Pluto not a planet?" to "What to do if your dog eats weed?" – we're striving to find answers to the most common questions you ask every day. Head to our Just Curious section to see what else we can answer for you. 

Flight Time Calculator

Flying time between cities.

Travelmath provides an online flight time calculator for all types of travel routes. You can enter airports, cities, states, countries, or zip codes to find the flying time between any two points. The database uses the great circle distance and the average airspeed of a commercial airliner to figure out how long a typical flight would take. Find your travel time to estimate the length of a flight between airports, or ask how long it takes to fly from one city to another.

You can also search for the closest airport to any city in the world or check the flying distance between airports. If you're thinking about a road trip, compare the driving time for the same route.

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Is Time Travel Possible?

We all travel in time! We travel one year in time between birthdays, for example. And we are all traveling in time at approximately the same speed: 1 second per second.

We typically experience time at one second per second. Credit: NASA/JPL-Caltech

NASA's space telescopes also give us a way to look back in time. Telescopes help us see stars and galaxies that are very far away . It takes a long time for the light from faraway galaxies to reach us. So, when we look into the sky with a telescope, we are seeing what those stars and galaxies looked like a very long time ago.

However, when we think of the phrase "time travel," we are usually thinking of traveling faster than 1 second per second. That kind of time travel sounds like something you'd only see in movies or science fiction books. Could it be real? Science says yes!

This image from the Hubble Space Telescope shows galaxies that are very far away as they existed a very long time ago. Credit: NASA, ESA and R. Thompson (Univ. Arizona)

How do we know that time travel is possible?

More than 100 years ago, a famous scientist named Albert Einstein came up with an idea about how time works. He called it relativity. This theory says that time and space are linked together. Einstein also said our universe has a speed limit: nothing can travel faster than the speed of light (186,000 miles per second).

Einstein's theory of relativity says that space and time are linked together. Credit: NASA/JPL-Caltech

What does this mean for time travel? Well, according to this theory, the faster you travel, the slower you experience time. Scientists have done some experiments to show that this is true.

For example, there was an experiment that used two clocks set to the exact same time. One clock stayed on Earth, while the other flew in an airplane (going in the same direction Earth rotates).

After the airplane flew around the world, scientists compared the two clocks. The clock on the fast-moving airplane was slightly behind the clock on the ground. So, the clock on the airplane was traveling slightly slower in time than 1 second per second.

Credit: NASA/JPL-Caltech

Can we use time travel in everyday life?

We can't use a time machine to travel hundreds of years into the past or future. That kind of time travel only happens in books and movies. But the math of time travel does affect the things we use every day.

For example, we use GPS satellites to help us figure out how to get to new places. (Check out our video about how GPS satellites work .) NASA scientists also use a high-accuracy version of GPS to keep track of where satellites are in space. But did you know that GPS relies on time-travel calculations to help you get around town?

GPS satellites orbit around Earth very quickly at about 8,700 miles (14,000 kilometers) per hour. This slows down GPS satellite clocks by a small fraction of a second (similar to the airplane example above).

GPS satellites orbit around Earth at about 8,700 miles (14,000 kilometers) per hour. Credit: GPS.gov

However, the satellites are also orbiting Earth about 12,550 miles (20,200 km) above the surface. This actually speeds up GPS satellite clocks by a slighter larger fraction of a second.

Here's how: Einstein's theory also says that gravity curves space and time, causing the passage of time to slow down. High up where the satellites orbit, Earth's gravity is much weaker. This causes the clocks on GPS satellites to run faster than clocks on the ground.

The combined result is that the clocks on GPS satellites experience time at a rate slightly faster than 1 second per second. Luckily, scientists can use math to correct these differences in time.

If scientists didn't correct the GPS clocks, there would be big problems. GPS satellites wouldn't be able to correctly calculate their position or yours. The errors would add up to a few miles each day, which is a big deal. GPS maps might think your home is nowhere near where it actually is!

In Summary:

Yes, time travel is indeed a real thing. But it's not quite what you've probably seen in the movies. Under certain conditions, it is possible to experience time passing at a different rate than 1 second per second. And there are important reasons why we need to understand this real-world form of time travel.

If you liked this, you may like:

Time travel could be possible, but only with parallel timelines

Assistant Professor, Physics, Brock University

Disclosure statement

Barak Shoshany does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

Brock University provides funding as a member of The Conversation CA-FR.

Brock University provides funding as a member of The Conversation CA.

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Have you ever made a mistake that you wish you could undo? Correcting past mistakes is one of the reasons we find the concept of time travel so fascinating. As often portrayed in science fiction, with a time machine, nothing is permanent anymore — you can always go back and change it. But is time travel really possible in our universe , or is it just science fiction?

Read more: Curious Kids: is time travel possible for humans?

Our modern understanding of time and causality comes from general relativity . Theoretical physicist Albert Einstein’s theory combines space and time into a single entity — “spacetime” — and provides a remarkably intricate explanation of how they both work, at a level unmatched by any other established theory. This theory has existed for more than 100 years, and has been experimentally verified to extremely high precision, so physicists are fairly certain it provides an accurate description of the causal structure of our universe.

For decades, physicists have been trying to use general relativity to figure out if time travel is possible . It turns out that you can write down equations that describe time travel and are fully compatible and consistent with relativity. But physics is not mathematics, and equations are meaningless if they do not correspond to anything in reality.

Arguments against time travel

There are two main issues which make us think these equations may be unrealistic. The first issue is a practical one: building a time machine seems to require exotic matter , which is matter with negative energy. All the matter we see in our daily lives has positive energy — matter with negative energy is not something you can just find lying around. From quantum mechanics, we know that such matter can theoretically be created, but in too small quantities and for too short times .

However, there is no proof that it is impossible to create exotic matter in sufficient quantities. Furthermore, other equations may be discovered that allow time travel without requiring exotic matter. Therefore, this issue may just be a limitation of our current technology or understanding of quantum mechanics.

The other main issue is less practical, but more significant: it is the observation that time travel seems to contradict logic, in the form of time travel paradoxes . There are several types of such paradoxes, but the most problematic are consistency paradoxes .

A popular trope in science fiction, consistency paradoxes happen whenever there is a certain event that leads to changing the past, but the change itself prevents this event from happening in the first place.

For example, consider a scenario where I enter my time machine, use it to go back in time five minutes, and destroy the machine as soon as I get to the past. Now that I destroyed the time machine, it would be impossible for me to use it five minutes later.

But if I cannot use the time machine, then I cannot go back in time and destroy it. Therefore, it is not destroyed, so I can go back in time and destroy it. In other words, the time machine is destroyed if and only if it is not destroyed. Since it cannot be both destroyed and not destroyed simultaneously, this scenario is inconsistent and paradoxical.

Eliminating the paradoxes

There’s a common misconception in science fiction that paradoxes can be “created.” Time travellers are usually warned not to make significant changes to the past and to avoid meeting their past selves for this exact reason. Examples of this may be found in many time travel movies, such as the Back to the Future trilogy.

But in physics, a paradox is not an event that can actually happen — it is a purely theoretical concept that points towards an inconsistency in the theory itself. In other words, consistency paradoxes don’t merely imply time travel is a dangerous endeavour, they imply it simply cannot be possible.

This was one of the motivations for theoretical physicist Stephen Hawking to formulate his chronology protection conjecture , which states that time travel should be impossible. However, this conjecture so far remains unproven. Furthermore, the universe would be a much more interesting place if instead of eliminating time travel due to paradoxes, we could just eliminate the paradoxes themselves.

One attempt at resolving time travel paradoxes is theoretical physicist Igor Dmitriyevich Novikov’s self-consistency conjecture , which essentially states that you can travel to the past, but you cannot change it.

According to Novikov, if I tried to destroy my time machine five minutes in the past, I would find that it is impossible to do so. The laws of physics would somehow conspire to preserve consistency.

Introducing multiple histories

But what’s the point of going back in time if you cannot change the past? My recent work, together with my students Jacob Hauser and Jared Wogan, shows that there are time travel paradoxes that Novikov’s conjecture cannot resolve. This takes us back to square one, since if even just one paradox cannot be eliminated, time travel remains logically impossible.

So, is this the final nail in the coffin of time travel? Not quite. We showed that allowing for multiple histories (or in more familiar terms, parallel timelines) can resolve the paradoxes that Novikov’s conjecture cannot. In fact, it can resolve any paradox you throw at it.

The idea is very simple. When I exit the time machine, I exit into a different timeline. In that timeline, I can do whatever I want, including destroying the time machine, without changing anything in the original timeline I came from. Since I cannot destroy the time machine in the original timeline, which is the one I actually used to travel back in time, there is no paradox.

After working on time travel paradoxes for the last three years , I have become increasingly convinced that time travel could be possible, but only if our universe can allow multiple histories to coexist. So, can it?

Quantum mechanics certainly seems to imply so, at least if you subscribe to Everett’s “many-worlds” interpretation , where one history can “split” into multiple histories, one for each possible measurement outcome – for example, whether Schrödinger’s cat is alive or dead, or whether or not I arrived in the past.

But these are just speculations. My students and I are currently working on finding a concrete theory of time travel with multiple histories that is fully compatible with general relativity. Of course, even if we manage to find such a theory, this would not be sufficient to prove that time travel is possible, but it would at least mean that time travel is not ruled out by consistency paradoxes.

Time travel and parallel timelines almost always go hand-in-hand in science fiction, but now we have proof that they must go hand-in-hand in real science as well. General relativity and quantum mechanics tell us that time travel might be possible, but if it is, then multiple histories must also be possible.

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April 26, 2023

Is Time Travel Possible?

The laws of physics allow time travel. So why haven’t people become chronological hoppers?

By Sarah Scoles

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In the movies, time travelers typically step inside a machine and—poof—disappear. They then reappear instantaneously among cowboys, knights or dinosaurs. What these films show is basically time teleportation .

Scientists don’t think this conception is likely in the real world, but they also don’t relegate time travel to the crackpot realm. In fact, the laws of physics might allow chronological hopping, but the devil is in the details.

Time traveling to the near future is easy: you’re doing it right now at a rate of one second per second, and physicists say that rate can change. According to Einstein’s special theory of relativity, time’s flow depends on how fast you’re moving. The quicker you travel, the slower seconds pass. And according to Einstein’s general theory of relativity , gravity also affects clocks: the more forceful the gravity nearby, the slower time goes.

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“Near massive bodies—near the surface of neutron stars or even at the surface of the Earth, although it’s a tiny effect—time runs slower than it does far away,” says Dave Goldberg, a cosmologist at Drexel University.

If a person were to hang out near the edge of a black hole , where gravity is prodigious, Goldberg says, only a few hours might pass for them while 1,000 years went by for someone on Earth. If the person who was near the black hole returned to this planet, they would have effectively traveled to the future. “That is a real effect,” he says. “That is completely uncontroversial.”

Going backward in time gets thorny, though (thornier than getting ripped to shreds inside a black hole). Scientists have come up with a few ways it might be possible, and they have been aware of time travel paradoxes in general relativity for decades. Fabio Costa, a physicist at the Nordic Institute for Theoretical Physics, notes that an early solution with time travel began with a scenario written in the 1920s. That idea involved massive long cylinder that spun fast in the manner of straw rolled between your palms and that twisted spacetime along with it. The understanding that this object could act as a time machine allowing one to travel to the past only happened in the 1970s, a few decades after scientists had discovered a phenomenon called “closed timelike curves.”

“A closed timelike curve describes the trajectory of a hypothetical observer that, while always traveling forward in time from their own perspective, at some point finds themselves at the same place and time where they started, creating a loop,” Costa says. “This is possible in a region of spacetime that, warped by gravity, loops into itself.”

“Einstein read [about closed timelike curves] and was very disturbed by this idea,” he adds. The phenomenon nevertheless spurred later research.

Science began to take time travel seriously in the 1980s. In 1990, for instance, Russian physicist Igor Novikov and American physicist Kip Thorne collaborated on a research paper about closed time-like curves. “They started to study not only how one could try to build a time machine but also how it would work,” Costa says.

Just as importantly, though, they investigated the problems with time travel. What if, for instance, you tossed a billiard ball into a time machine, and it traveled to the past and then collided with its past self in a way that meant its present self could never enter the time machine? “That looks like a paradox,” Costa says.

Since the 1990s, he says, there’s been on-and-off interest in the topic yet no big breakthrough. The field isn’t very active today, in part because every proposed model of a time machine has problems. “It has some attractive features, possibly some potential, but then when one starts to sort of unravel the details, there ends up being some kind of a roadblock,” says Gaurav Khanna of the University of Rhode Island.

For instance, most time travel models require negative mass —and hence negative energy because, as Albert Einstein revealed when he discovered E = mc 2 , mass and energy are one and the same. In theory, at least, just as an electric charge can be positive or negative, so can mass—though no one’s ever found an example of negative mass. Why does time travel depend on such exotic matter? In many cases, it is needed to hold open a wormhole—a tunnel in spacetime predicted by general relativity that connects one point in the cosmos to another.

Without negative mass, gravity would cause this tunnel to collapse. “You can think of it as counteracting the positive mass or energy that wants to traverse the wormhole,” Goldberg says.

Khanna and Goldberg concur that it’s unlikely matter with negative mass even exists, although Khanna notes that some quantum phenomena show promise, for instance, for negative energy on very small scales. But that would be “nowhere close to the scale that would be needed” for a realistic time machine, he says.

These challenges explain why Khanna initially discouraged Caroline Mallary, then his graduate student at the University of Massachusetts Dartmouth, from doing a time travel project. Mallary and Khanna went forward anyway and came up with a theoretical time machine that didn’t require negative mass. In its simplistic form, Mallary’s idea involves two parallel cars, each made of regular matter. If you leave one parked and zoom the other with extreme acceleration, a closed timelike curve will form between them.

Easy, right? But while Mallary’s model gets rid of the need for negative matter, it adds another hurdle: it requires infinite density inside the cars for them to affect spacetime in a way that would be useful for time travel. Infinite density can be found inside a black hole, where gravity is so intense that it squishes matter into a mind-bogglingly small space called a singularity. In the model, each of the cars needs to contain such a singularity. “One of the reasons that there's not a lot of active research on this sort of thing is because of these constraints,” Mallary says.

Other researchers have created models of time travel that involve a wormhole, or a tunnel in spacetime from one point in the cosmos to another. “It's sort of a shortcut through the universe,” Goldberg says. Imagine accelerating one end of the wormhole to near the speed of light and then sending it back to where it came from. “Those two sides are no longer synced,” he says. “One is in the past; one is in the future.” Walk between them, and you’re time traveling.

You could accomplish something similar by moving one end of the wormhole near a big gravitational field—such as a black hole—while keeping the other end near a smaller gravitational force. In that way, time would slow down on the big gravity side, essentially allowing a particle or some other chunk of mass to reside in the past relative to the other side of the wormhole.

Making a wormhole requires pesky negative mass and energy, however. A wormhole created from normal mass would collapse because of gravity. “Most designs tend to have some similar sorts of issues,” Goldberg says. They’re theoretically possible, but there’s currently no feasible way to make them, kind of like a good-tasting pizza with no calories.

And maybe the problem is not just that we don’t know how to make time travel machines but also that it’s not possible to do so except on microscopic scales—a belief held by the late physicist Stephen Hawking. He proposed the chronology protection conjecture: The universe doesn’t allow time travel because it doesn’t allow alterations to the past. “It seems there is a chronology protection agency, which prevents the appearance of closed timelike curves and so makes the universe safe for historians,” Hawking wrote in a 1992 paper in Physical Review D .

Part of his reasoning involved the paradoxes time travel would create such as the aforementioned situation with a billiard ball and its more famous counterpart, the grandfather paradox : If you go back in time and kill your grandfather before he has children, you can’t be born, and therefore you can’t time travel, and therefore you couldn’t have killed your grandfather. And yet there you are.

Those complications are what interests Massachusetts Institute of Technology philosopher Agustin Rayo, however, because the paradoxes don’t just call causality and chronology into question. They also make free will seem suspect. If physics says you can go back in time, then why can’t you kill your grandfather? “What stops you?” he says. Are you not free?

Rayo suspects that time travel is consistent with free will, though. “What’s past is past,” he says. “So if, in fact, my grandfather survived long enough to have children, traveling back in time isn’t going to change that. Why will I fail if I try? I don’t know because I don’t have enough information about the past. What I do know is that I’ll fail somehow.”

If you went to kill your grandfather, in other words, you’d perhaps slip on a banana en route or miss the bus. “It's not like you would find some special force compelling you not to do it,” Costa says. “You would fail to do it for perfectly mundane reasons.”

In 2020 Costa worked with Germain Tobar, then his undergraduate student at the University of Queensland in Australia, on the math that would underlie a similar idea: that time travel is possible without paradoxes and with freedom of choice.

Goldberg agrees with them in a way. “I definitely fall into the category of [thinking that] if there is time travel, it will be constructed in such a way that it produces one self-consistent view of history,” he says. “Because that seems to be the way that all the rest of our physical laws are constructed.”

No one knows what the future of time travel to the past will hold. And so far, no time travelers have come to tell us about it.

A Student Just Proved Paradox-Free Time Travel Is Possible

Now we can all go back to 2019.

• This follows recent research observing that the present is not changed by a time-traveling qubit.
• It's still not very nice to step on butterflies, though.

In a peer-reviewed paper, an honors undergraduate student says he has mathematically proven the physical feasibility of a specific kind of time travel. The paper appears in Classical and Quantum Gravity .

University of Queensland student Germain Tobar, who the university’s press release calls “prodigious,” worked with UQ physics professor Fabio Costa on this paper . In “ Reversible dynamics with closed time-like curves and freedom of choice ,” Tobar and Costa say they’ve found a middle ground in mathematics that solves a major logical paradox in one model of time travel. Let’s dig in.

The math itself is complex, but it boils down to something fairly simple. Time travel discussion focuses on closed time-like curves (CTCs), something Albert Einstein first posited. And Tobar and Costa say that as long as just two pieces of an entire scenario within a CTC are still in “causal order” when you leave, the rest is subject to local free will.

“Our results show that CTCs are not only compatible with determinism and with the local 'free choice' of operations, but also with a rich and diverse range of scenarios and dynamical processes,” their paper concludes.

In a university statement, Costa illustrates the science with an analogy:

“Say you travelled in time, in an attempt to stop COVID-19's patient zero from being exposed to the virus. However if you stopped that individual from becoming infected, that would eliminate the motivation for you to go back and stop the pandemic in the first place. This is a paradox, an inconsistency that often leads people to think that time travel cannot occur in our universe. [L]ogically it's hard to accept because that would affect our freedom to make any arbitrary action. It would mean you can time travel, but you cannot do anything that would cause a paradox to occur."

Some outcomes of this are grouped as the “ butterfly effect ,” which refers to unintended large consequences of small actions. But the real truth, in terms of the mathematical outcomes, is more like another classic parable: the monkey’s paw. Be careful what you wish for, and be careful what you time travel for. Tobar explains in the statement:

“In the coronavirus patient zero example, you might try and stop patient zero from becoming infected, but in doing so you would catch the virus and become patient zero, or someone else would. No matter what you did, the salient events would just recalibrate around you. Try as you might to create a paradox, the events will always adjust themselves, to avoid any inconsistency.”

While that sounds frustrating for the person trying to prevent a pandemic or kill Hitler, for mathematicians, it helps to smooth a fundamental speed bump in the way we think about time. It also fits with quantum findings from Los Alamos , for example, and the way random walk mathematics behave in one and two dimensions.

At the very least, this research suggests that anyone eventually designing a way to meaningfully travel in time could do so and experiment without an underlying fear of ruining the world—at least not right away.

Caroline Delbert is a writer, avid reader, and contributing editor at Pop Mech. She's also an enthusiast of just about everything. Her favorite topics include nuclear energy, cosmology, math of everyday things, and the philosophy of it all. 

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How to Adjust to a New Time Zone

Steer clear of jet lag with these easy tips

Traveling to a different time zone can be exciting—but the time change can take some getting used to. Depending on how far you travel, it may be necessary to take specific steps to adapt to a new time zone and avoid the symptoms of jet lag , which can make your journey less enjoyable.

Jet lag can cause you to feel ill as well as tired, and it can ruin a trip. Fortunately, there are ways to prepare for time zone transitions.

This article explains the signs of jet lag and strategies to help you avoid it or manage the symptoms.

Symptoms of Jet Lag

The most common symptoms of jet lag include:

• Mental confusion
• Slowing down of mental and physical abilities
• Irritability
• Muscle soreness

Being unable to move around during a long flight, dehydration, and disrupted eating schedules can contribute to these problems.

Light and Jet Lag

Light, whether from the sun or a lamp , has a strong effect on the body's circadian rhythms . That's one of the factors determining when you're alert and awake and when you're tired and need to sleep.

When you travel to another time zone, there's a dramatic shift in your exposure to light and a misalignment of your body’s sense of day and night. Until the circadian rhythm is reset, jet lag symptoms persist.

The sudden disruption of your circadian rhythms that occurs with jet lag can be distressing, especially the further you travel. If you fly from, say, the east coast of the United States to the west coast, you'll be crossing only a few time zones, and adjusting will be relatively easy. But if you cross oceans and continents it will be more challenging.

In general, it can take one day per time zone changed for circadian rhythms and sleep to get in sync. 

How quickly you switch time zones matters as well. Since driving or traveling by bus or even train takes longer than flying, your body has an opportunity to adjust to time zone changes gradually. For example, if it takes 10 hours to pass through a time zone while driving, then you essentially have a half-day to accommodate for the shift.

Finally, the direction of travel impacts circadian rhythms. You may have heard a frequent traveler say, "East is a beast, west is best." What he means is that traveling in a westward direction is often easier to tolerate because it is easier to shift the circadian rhythm to a later time. To think about it another way, consider how easy it is to stay up a few hours later in the night and how challenging it can be to wake up that much earlier in the morning.

Adjusting to a New Time Zone

If you're planning travel that will land you in a different time zone, severe jet lag isn't inevitable. There are ways to help you prepare your body for the change so that you can enjoy your trip with as little disruption to your sleep as possible.

Before your trip, figure out how much you'll need to shift your sleep and wake times to be in sync after you arrive. Allowing enough time to do it gradually, begin to go to bed earlier and get up earlier, or vice-versa depending on the direction you'll be traveling in, to get your body used to the new time zone before you have to live in it.

Make Yourself Stay Awake 

Delaying sleep generates a very robust sleep drive and may counteract some of the issues related to a misaligned circadian rhythm. Much like pulling an all-nighter, your desire for sleep will be exceptionally strong if you stay awake for a prolonged period , no matter what time zone you're in.

To reset yourself, try to stay awake on the plane and when you arrive. Once you're settled in, fight the urge to take a nap, and try to stay awake until your normal bedtime based on local time.

See the Light

The most important factor in resetting your body clock is light. If you can, get 15 to 30 minutes of direct sunlight as soon as you wake up. Go for a walk, eat breakfast outside, or just sit in the sun and read.

Keeping a regular bedtime and wake time with morning light exposure will help a great deal.

Deflect Drowsiness

When dealing with jet-lag-related daytime sleepiness, the same go-to remedies you use at home can help:

• Drink a cup of coffee or tea, but don't overdo your caffeine intake.
• Take a short nap when needed, sleeping for 20 minutes or less; longer naps may make you feel groggier when you wake up.
• Consider taking melatonin . A 5 mg dose can realign your circadian rhythm to the new time zone. Take it in the morning to set your internal clock to a later time and in the evening to set it to an earlier time.
• Don't drive when you're drowsy.

Returning Home

As your trip comes to an end, ease yourself into the change to come by gradually adjusting your bedtime and wake time in 30- to 60-minute increments towards the new clock setting. If this isn't possible, follow the same advice above to adjust to the new time zone at home.

Ambesh P, Shetty V, Ambesh S, Gupta SS, Kamholz S, Wolf L. Jet lag: Heuristics and therapeutics .  J Family Med Prim Care . 2018;7(3):507-510. doi:10.4103/jfmpc.jfmpc_220_17

Fowler PM, Knez W, Crowcroft S, et al. Greater effect of east versus west travel on jet lag, sleep, and team sport performance . Medicine & Science in Sports & Exercise . 2017;49(12):2548-2561. doi:10.1249/mss.0000000000001374

Kryger, MH et al.  Principles and Practice of Sleep Medicine . Elsevier, 5th edition, 2011.

By Brandon Peters, MD Dr. Peters is a board-certified neurologist and sleep medicine specialist and is a fellow of the American Academy of Sleep Medicine.

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Is time travel possible? An astrophysicist explains

Will it ever be possible for time travel to occur? – Alana C., age 12, Queens, New York

Have you ever dreamed of traveling through time, like characters do in science fiction movies? For centuries, the concept of time travel has captivated people’s imaginations. Time travel is the concept of moving between different points in time, just like you move between different places. In movies, you might have seen characters using special machines, magical devices or even hopping into a futuristic car to travel backward or forward in time.

But is this just a fun idea for movies, or could it really happen?

The question of whether time is reversible remains one of the biggest unresolved questions in science. If the universe follows the  laws of thermodynamics , it may not be possible. The second law of thermodynamics states that things in the universe can either remain the same or become more disordered over time.

It’s a bit like saying you can’t unscramble eggs once they’ve been cooked. According to this law, the universe can never go back exactly to how it was before. Time can only go forward, like a one-way street.

Time is relative

However, physicist Albert Einstein’s  theory of special relativity  suggests that time passes at different rates for different people. Someone speeding along on a spaceship moving close to the  speed of light  – 671 million miles per hour! – will experience time slower than a person on Earth.

Related: The speed of light, explained

People have yet to build spaceships that can move at speeds anywhere near as fast as light, but astronauts who visit the International Space Station orbit around the Earth at speeds close to 17,500 mph. Astronaut Scott Kelly has spent 520 days at the International Space Station, and as a result has aged a little more slowly than his twin brother – and fellow astronaut – Mark Kelly. Scott used to be 6 minutes younger than his twin brother. Now, because Scott was traveling so much faster than Mark and for so many days, he is  6 minutes and 5 milliseconds younger .

Some scientists are exploring other ideas that could theoretically allow time travel. One concept involves  wormholes , or hypothetical tunnels in space that could create shortcuts for journeys across the universe. If someone could build a wormhole and then figure out a way to move one end at close to the speed of light – like the hypothetical spaceship mentioned above – the moving end would age more slowly than the stationary end. Someone who entered the moving end and exited the wormhole through the stationary end would come out in their past.

However, wormholes remain theoretical : Scientists have yet to spot one. It also looks like it would be  incredibly challenging  to send humans through a wormhole space tunnel.

Time travel paradoxes and failed dinner parties

There are also paradoxes associated with time travel. The famous “ grandfather paradox ” is a hypothetical problem that could arise if someone traveled back in time and accidentally prevented their grandparents from meeting. This would create a paradox where you were never born, which raises the question: How could you have traveled back in time in the first place? It’s a mind-boggling puzzle that adds to the mystery of time travel.

Famously, physicist Stephen Hawking tested the possibility of time travel by  throwing a dinner party  where invitations noting the date, time and coordinates were not sent out until after it had happened. His hope was that his invitation would be read by someone living in the future, who had capabilities to travel back in time. But no one showed up.

As he  pointed out : “The best evidence we have that time travel is not possible, and never will be, is that we have not been invaded by hordes of tourists from the future.”

Telescopes are time machines

Interestingly, astrophysicists armed with powerful telescopes possess a unique form of time travel. As they peer into the vast expanse of the cosmos, they gaze into the past universe. Light from all galaxies and stars takes time to travel, and these beams of light carry information from the distant past. When astrophysicists observe a star or a galaxy through a telescope, they are not seeing it as it is in the present, but as it existed when the light began its journey to Earth millions to billions of years ago.

NASA’s newest space telescope, the  James Webb Space Telescope , is peering at galaxies that were formed at the very beginning of the Big Bang, about 13.7 billion years ago.

While we aren’t likely to have time machines like the ones in movies anytime soon, scientists are actively researching and exploring new ideas. But for now, we’ll have to enjoy the idea of time travel in our favorite books, movies and dreams.

This article first appeared on the Conversation. You can read the original here .

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Time travel: five ways that we could do it

Cathal O’Connell

Cathal O'Connell is a science writer based in Melbourne.

In 2009 the British physicist Stephen Hawking held a party for time travellers – the twist was he sent out the invites a year later (No guests showed up). Time travel is probably impossible. Even if it were possible, Hawking and others have argued that you could never travel back before the moment your time machine was built.

But travel to the future? That’s a different story.

Of course, we are all time travellers as we are swept along in the current of time, from past to future, at a rate of one hour per hour.

But, as with a river, the current flows at different speeds in different places. Science as we know it allows for several methods to take the fast-track into the future. Here’s a rundown.

1. Time travel via speed

This is the easiest and most practical way to time travel into the far future – go really fast.

According to Einstein’s theory of special relativity, when you travel at speeds approaching the speed of light, time slows down for you relative to the outside world.

This is not a just a conjecture or thought experiment – it’s been measured. Using twin atomic clocks (one flown in a jet aircraft, the other stationary on Earth) physicists have shown that a flying clock ticks slower, because of its speed.

In the case of the aircraft, the effect is minuscule. But If you were in a spaceship travelling at 90% of the speed of light, you’d experience time passing about 2.6 times slower than it was back on Earth.

And the closer you get to the speed of light, the more extreme the time-travel.

Computer solves a major time travel problem

The highest speeds achieved through any human technology are probably the protons whizzing around the Large Hadron Collider at 99.9999991% of the speed of light. Using special relativity we can calculate one second for the proton is equivalent to 27,777,778 seconds, or about 11 months , for us.

Amazingly, particle physicists have to take this time dilation into account when they are dealing with particles that decay. In the lab, muon particles typically decay in 2.2 microseconds. But fast moving muons, such as those created when cosmic rays strike the upper atmosphere, take 10 times longer to disintegrate.

2. Time travel via gravity

The next method of time travel is also inspired by Einstein. According to his theory of general relativity, the stronger the gravity you feel, the slower time moves.

As you get closer to the centre of the Earth, for example, the strength of gravity increases. Time runs slower for your feet than your head.

Again, this effect has been measured. In 2010, physicists at the US National Institute of Standards and Technology (NIST) placed two atomic clocks on shelves, one 33 centimetres above the other, and measured the difference in their rate of ticking. The lower one ticked slower because it feels a slightly stronger gravity.

To travel to the far future, all we need is a region of extremely strong gravity, such as a black hole. The closer you get to the event horizon, the slower time moves – but it’s risky business, cross the boundary and you can never escape.

And anyway, the effect is not that strong so it’s probably not worth the trip.

Assuming you had the technology to travel the vast distances to reach a black hole (the nearest is about 3,000 light years away), the time dilation through travelling would be far greater than any time dilation through orbiting the black hole itself.

(The situation described in the movie Interstellar , where one hour on a planet near a black hole is the equivalent of seven years back on Earth, is so extreme as to be impossible in our Universe, according to Kip Thorne, the movie’s scientific advisor.)

The most mindblowing thing, perhaps, is that GPS systems have to account for time dilation effects (due to both the speed of the satellites and gravity they feel) in order to work. Without these corrections, your phones GPS capability wouldn’t be able to pinpoint your location on Earth to within even a few kilometres.

3. Time travel via suspended animation

Another way to time travel to the future may be to slow your perception of time by slowing down, or stopping, your bodily processes and then restarting them later.

Bacterial spores can live for millions of years in a state of suspended animation, until the right conditions of temperature, moisture, food kick start their metabolisms again. Some mammals, such as bears and squirrels, can slow down their metabolism during hibernation, dramatically reducing their cells’ requirement for food and oxygen.

Could humans ever do the same?

Though completely stopping your metabolism is probably far beyond our current technology, some scientists are working towards achieving inducing a short-term hibernation state lasting at least a few hours. This might be just enough time to get a person through a medical emergency, such as a cardiac arrest, before they can reach the hospital.

In 2005, American scientists demonstrated a way to slow the metabolism of mice (which do not hibernate) by exposing them to minute doses of hydrogen sulphide, which binds to the same cell receptors as oxygen. The core body temperature of the mice dropped to 13 °C and metabolism decreased 10-fold. After six hours the mice could be reanimated without ill effects.

Unfortunately, similar experiments on sheep and pigs were not successful, suggesting the method might not work for larger animals.

Another method, which induces a hypothermic hibernation by replacing the blood with a cold saline solution, has worked on pigs and is currently undergoing human clinical trials in Pittsburgh.

4. Time travel via wormholes

General relativity also allows for the possibility for shortcuts through spacetime, known as wormholes, which might be able to bridge distances of a billion light years or more, or different points in time.

Many physicists, including Stephen Hawking, believe wormholes are constantly popping in and out of existence at the quantum scale, far smaller than atoms. The trick would be to capture one, and inflate it to human scales – a feat that would require a huge amount of energy, but which might just be possible, in theory.

Attempts to prove this either way have failed, ultimately because of the incompatibility between general relativity and quantum mechanics.

5. Time travel using light

Another time travel idea, put forward by the American physicist Ron Mallet, is to use a rotating cylinder of light to twist spacetime. Anything dropped inside the swirling cylinder could theoretically be dragged around in space and in time, in a similar way to how a bubble runs around on top your coffee after you swirl it with a spoon.

According to Mallet, the right geometry could lead to time travel into either the past and the future.

Since publishing his theory in 2000, Mallet has been trying to raise the funds to pay for a proof of concept experiment, which involves dropping neutrons through a circular arrangement of spinning lasers.

His ideas have not grabbed the rest of the physics community however, with others arguing that one of the assumptions of his basic model is plagued by a singularity, which is physics-speak for “it’s impossible”.

The Royal Institution of Australia has an Education resource based on this article. You can access it here .

Related Reading: Computer solves a major time travel problem

Originally published by Cosmos as Time travel: five ways that we could do it

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How to avoid the worst of jet lag and maximize your travel time

Jet lag is a problem for many travelers but there are some easy ways to adjust your body clock

LONDON -- It's the bane of many travelers: jet lag. Nobody wants to lose out because they're too tired to enjoy the delights of their vacation spot.

Here are some tips on how to handle jet lag, wherever you might end up.

Scientists define jet lag as the effect on the human body of traveling across different time zones. Our bodies have biological clocks programmed into almost every cell in the body, according to Sofia Axelrod, who studies circadian rhythms at Rockefeller University in New York.

“The clock is set by the 24-hour light and dark pattern,” Axelrod said. “Every morning when we wake up, specialized (light) receptor cells in our retina receive a daylight signal, which is transmitted to the brain and from there, the whole body.”

When we travel to another time zone, our eyes receive the daylight signal at a different time than usual, causing our internal clocks to reset. But that process can take awhile — and it’s during that adjustment period that we feel the effects of jet lag.

Yes, but that can come at a cost. Malcolm von Schantz, a professor who specializes in circadian rhythms at Northumbria University in Newcastle, said that flying in premium cabins where travelers can stretch out and properly rest, can ward off sleep deprivation, but he acknowledges that isn't an option for most people. Still, he said that timing your flights can help. For example, he suggests flying from Europe to North America during the day, so that it’s evening when passengers land and they can get a proper night’s sleep.

“If you take the evening flight instead, you’ll be woken up at midnight to be served breakfast and land an hour or two later, when both jet lag and sleep deprivation will hit you hard and simultaneously,” he said.

Von Schantz also said flying in newer models with a lighter frame, like the Airbus A350 or Boeing 787 Dreamliner, would help. That’s because those planes can maintain a more comfortable cabin atmosphere, which should help travelers feel less worn out by the end of their flights.

Experts say getting exposure to sunlight is critical to resetting your internal body clock. That can mean either avoiding morning sun or deliberately seeking it out, depending on where you’ve travelled from. Getting light in the morning will advance your body clock, while light exposure in the early evening will delay it. Naps are OK, but scientists warn against taking long siestas later in the day, as that might compromise your ability to sleep through the night.

Melatonin, a hormone that the brain naturally produces when the body thinks it’s night, can be helpful. But it’s not available everywhere and in some countries like the U.K. and France, a prescription is required. Von Schantz of Northumbria University said that one of the advantages of melatonin is that you can start taking it before your journey, to reset your internal clock quicker.

“If you’re in a part of the world where melatonin is available over the counter, you can combine the effects of light and melatonin to achieve the advance or delay (in your body clock) that you need,” he said.

Business travelers might want to consider arriving a day or two ahead of any important meetings or events, said Russell Foster of Oxford University, who has authored a book on circadian rhythms.

“You should just be aware that if you’re jet-lagged, you’re more likely to make unwise decisions, be less empathetic and unable to multitask,” he said.

Tourists might not need to be as alert as business travelers, but they should still be careful, he said. He advises tourists to get caught up on their sleep before doing anything potentially risky or that requires concentration, like driving.

Foster said he tries to maximize his light exposure when he arrives at a new destination to offset jet lag. But he also has a fallback strategy: coffee.

“I’m not suggesting it’s an ideal thing to do, but caffeine will help override the sleepiness and cognitive impairment you might be feeling as a result of jet lag,” he said.

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Educational Media Group. The AP is solely responsible for all content.

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Time is luxury, and having it all means squat without the calendar space to enjoy it. For ultra-high-end travel operators, the search for lost time has led to demand for a product that may sound slightly down market: package itineraries.

“More and more, travelers are looking for immersive, personalized, and worry-free travel experiences,” says Marc Speichert, executive vice president and chief commercial officer at the Four Seasons .

There is, however, one massive difference between these package itineraries and the geriatric-themed bus tours of yore: They’re by private jet, yacht, and Bentley.

For years, the Four Seasons has offered a Private Jet Experience , which Speichert says is about creating “a seamless end-to-end journey with our legendary comfort, service, and amenities.”

In a similar vein, White Desert speeds up Antarctic exploration by replacing the multi-day southward cruise with a private jet, a luxury whip.

“Many of our clients are company owners or entrepreneurs with highly pressurized jobs,” says Mindy Roberts, the company’s CMO. “When it comes to leisure travel, they’ve said they enjoy that the decision-making has been taken away from them and they can completely relax and be on holiday.”

Another factor driving growth in ultra-luxury, pre-planned, package bookings is their ability to facilitate slow travel. Both the Four Seasons and White Desert offer tours lasting upwards of three weeks, leaving plenty of time to explore each stop thoroughly.

Kalindi Juneja, CEO of U.K. firm PoB Hotels , says its guests are increasingly opting for longer stays in fewer destinations—its longest curated itinerary is 12 days. The brand is “prioritizing depth over breadth in their exploration,” says Juneja. “‘Authenticity’ drives guests to explore off-the-beaten-path destinations, engage with local artisans, savor traditional cuisine, and participate in cultural activities unique to each location on their itinerary.”

Below is a look at some of the most extravagant planned holidays on the market today and all the wild perks they offer.

Around the World in 24 Days

Four Seasons offer a wide range of itineraries using the private-jet service it launched in 2015, with eight tours taking place each year and varying between 13 and 24 nights in duration.

The World of Adventures tour begins in Seattle, spending a couple of days exploring the city and getting to know your jet-mates for the next three weeks, before heading to Kyoto for the first of eight stops. Along the way you will experience an immersion in Japanese tea culture, unwind in the incredible tropical nature of Bali and the Seychelles , and re-energise amidst the buzz of Bogotá. 

The stand-out experiences, however, are the time spent among wild mountain gorillas in Rwanda, observing these extraordinary animals at breathtakingly close quarters, and sailing on a specially chartered yacht around the Galápagos Islands. This trip has it all, from vibrant cities to truly remote wilderness—and by the time you reach your final leg in Fort Lauderdale, consider extending for a couple of days more to catch your breath and reflect on all you’ve seen.

From $215,000 per person

Seven Continent Completist

Having seen huge success with its South Pole trips—including its Echo Camp being named as one of Robb Report’s Top 50 Luxury Hotels in 2023—White Desert has created an expanded tour dubbed White Desert World that takes guests to all seven continents. 

Meet your group in Mexico City for a day before shoving off for 21 days of flying gradually eastwards. You’ll take in the majesty of Easter Island, the orangutans of Borneo and tigers of Jaipur, and the eclectic buzz of Istanbul before heading south through Namibia and South Africa and eventually arriving at Wolf Fang runway for a day spent on the planet’s most southerly continent. Those with more of an appetite for cold can opt to spend a further five days in Antarctica (there won’t be any nighttime there at that point in the year), exploring the whole of the landscape, meeting the local penguins, and witnessing some of the most astounding beauty our world has to offer.

From $188,000 per person; optional Antarctica extension $37,500

Britain by Bentley 

You may not immediately associate a luxury car brand with travel bookings, but that’s exactly why Bentley wanted to create this Extraordinary Journeys experience.

Bentley has led trips in destinations across the world, but the flagship route is in its home country, the United Kingdom. The week begins with a tour of the factory in Crewe followed by a dinner on the very line where each Bentley is handmade, with the models currently in production suspended above your head. An early start the next day lets a fleet of Bentleys—all provided by the brand, with the option for you to swap models each morning—begin the journey to the Highlands of Scotland and the home of partner brand the Macallan . Lunch and refreshment stops call in at some of the finest properties in the U.K., and routes are specifically plotted to provide maximum driving enjoyment. The crescendo is an incredible whisky tasting and dinner inside Macallan’s distillery—don’t worry, the chauffeurs will drive you afterwards.

From roughly $18,900 per person, based on double occupancy

A Gracious Grand Tour

A few hundred years ago it was customary for the wealthy young men of Europe to complete a Grand Tour after their education. They traveled to the most cultured cities on the continent with the goal of expanding their horizons and becoming more well-rounded, “worldly” individuals. 

Rocco Forte Hotels , taking inspiration from that period, have leveraged its network of luxury hotels across Europe to create an itinerary that reflects the most popular spots of the 17th century, from Scotland to Sicily. The trip begins in Edinburgh at the legendary Balmoral hotel. You’re invited to spend two nights first in the Scottish capital and then in London before heading through the channel tunnel to Brussels. From there, you’ll travel through Germany and Italy to eventually arrive in Sicily. 

In total, eight of Europe’s most cultured cities are on the menu, with experiences arranged in each to showcase the local art scenes. Travel from point-to-point is on first-class rail, catering to the taste for slow travel and allowing you to enjoy not just the cities you’ll stop in, but the landscapes between them as well.

From roughly $8,600 per person

Best of British

The PoB Hotels group has more than 50 properties all across the British mainland in its portfolio. Members include country retreats, like the Fife Arms and Glenapp Castle in Scotland, as well as city spots such as west London’s the Hari. The group’s PoB Breaks tour allows you to join up stays at multiple hotels, creating a road map for exploring the hidden pockets of Scotland, England, and Wales. 

Options range from a short four-day tour of northern England based on the recommendations of a local celebrity chef to an extended 12-night exploration of the west coast of Scotland. And if the line-ups PoB have chosen don’t completely meet your requirements, simply use the interactive map on its booking site to create your own bespoke itinerary from scratch.

Rates depend on properties chosen

Fjord Like a Nord

The utter seclusion of the Norwegian fjords make them an ideal destination for those looking to escape the stresses of modern life. Local experts 62 Nord have curated a series of Drive the Fjords trips around the most opulent hotels in the region.

You’ll drive between each hotel along some exceptionally exciting roads in a Porsche Taycan . Dramatic scenery, world-class accommodation, and the chance to drive the legendary Trollstigen are among the attractions of this itinerary, but there is plenty more to discover along the way.  

From roughly $9,000 based on double occupancy

The Set Collection Grand Tour

Another tour based on the wanderings of the aristocracy is the Set Collection Grand Tour . It’s a condensed version of the historic tour that visits the three founding members of the luxury hotel group.  

The trip begins in London at the magnificent Hotel Café Royal before heading to Paris and Amsterdam. At every stage, the best of the art and culinary scenes in Europe’s most cosmopolitan cities is highlighted. You’ll spend three nights in each city, and the concierge team in each hotel— Hôtel Lutetia in Paris; Conservatorium in Amsterdam—works with you ahead of time to plan a bespoke agenda of experiences. Booking into suites includes private use of a chauffeur-driven Rolls-Royce or Mercedes for 10 hours each day, meaning your exploration of each city will be as opulent and relaxing as your accommodation.

Rates based on tier of accommodation

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How long does it take to get to Mars?

We explore how long it takes to get to Mars and the factors that affect a journey to the Red Planet.

• Distance to Mars
• Traveling at the speed of light

Fastest spacecraft so far

Mars travel time q&a with an expert.

• Travel time calculation problems
• Past mission's travel times

Additional resources

Ever wondered how long does it take to get to Mars? 

The answer depends on several factors, ranging from the position of Earth and Mars to the technology that would propel you there. According to NASA , a one-way trip to the Red Planet would take about nine months . If you wanted to make it a round-trip , all in all, it would take about 21 months as you will need to wait about three months on Mars to make sure Earth and Mars are in a suitable location to make the trip back home. 

We take a look at how long a trip to the Red Planet would take using available technology and explore some of the factors that would affect your travel time.

Related: Curiosity rover: 15 awe-inspiring photos of Mars (gallery) 

How far away is Mars?

To determine how long it will take to reach Mars, we must first know the distance between the two planets.

Mars is the fourth planet from the sun, and the second closest to Earth (Venus is the closest). But the distance between Earth and Mars is constantly changing as they travel around the sun .

In theory, the closest that Earth and Mars would approach each other would be when Mars is at its closest point to the sun (perihelion) and Earth is at its farthest (aphelion). This would put the planets only 33.9 million miles (54.6 million kilometers) apart. However, this has never happened in recorded history. The closest recorded approach of the two planets occurred in 2003 when they were only 34.8 million miles (56 million km) apart.

The two planets are farthest apart when they are both at their farthest from the sun, on opposite sides of the star. At this point, they can be 250 million miles (401 million km) apart.

The average distance between Earth and Mars is 140 million miles (225 million km).

Related: What is the temperature on Mars?

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

Light travels at approximately 186,282 miles per second (299,792 km per second). Therefore, a light shining from the surface of Mars would take the following amount of time to reach Earth (or vice versa):

• Closest possible approach: 182 seconds, or 3.03 minutes
• Closest recorded approach: 187 seconds, or 3.11 minutes
• Farthest approach: 1,342 seconds, or 22.4 minutes
• On average: 751 seconds, or just over 12.5 minutes

The fastest spacecraft is NASA's Parker Solar Probe , as it keeps breaking its own speed records as it moves closer to the sun. On Nov 21, 2021, the Parker Solar Probe reached a top speed of 101 miles (163 kilometers) per second during its 10th close flyby of our star, which translates to a phenomenal 364,621 mph (586,000 kph). According to a NASA statement , when the Parker Solar Probe comes within 4 million miles (6.2 million kilometers) of the solar surface in December 2024, the spacecraft's speed will top 430,000 miles per hour (692,000 kph)!

So if you were theoretically able to hitch a ride on the Parker Solar Probe and take it on a detour from its sun-focused mission to travel in a straight line from Earth to Mars, traveling at the speeds the probe reaches during its 10th flyby (101 miles per second), the time it would take you to get to Mars would be:

• Closest possible approach: 93 hours 
• Closest recorded approach: 95 hours  
• Farthest approach: 686 hours (28.5 days)  
• On average: 384 hours (16 days)  

We asked Michael Khan, ESA Senior Mission Analyst some frequently asked questions about travel times to Mars. 

Michael Khan is a Senior Mission Analyst for the European Space Agency (ESA). His work involves studying the orbital mechanics for journeys to planetary bodies including Mars.

How long does it take to get to Mars & what affects the travel time?

The time it takes to get from one celestial body to another depends largely on the energy that one is willing to expend. Here  "energy" refers to the effort put in by the launch vehicle and the sum of the maneuvers of the rocket motors aboard the spacecraft, and the amount of propellant that is used. In space travel, everything boils down to energy. Spaceflight is the clever management of energy.

Some common solutions for transfers to the moon are 1) the Hohmann-like transfer and 2) the Free Return Transfer. The Hohmann Transfer is often referred to as the one that requires the lowest energy, but that is true only if you want the transfer to last only a few days and, in addition, if some constraints on the launch apply. Things get very complicated from there on, so I won't go into details.

Concerning transfers to Mars, these are by necessity interplanetary transfers, i.e., orbits that have the sun as central body. Otherwise, much of what was said above applies: the issue remains the expense of energy. An additional complication lies in the fact that the Mars orbit is quite eccentric and also its orbit plane is inclined with respect to that of the Earth. And of course, Mars requires longer to orbit the sun than the Earth does. All of this is taken into account in a common type of diagram called the "pork chop plot", which essentially tells you the required dates of departure and arrival and the amount of energy required.

The "pork chop plot" shows the trajectory expert that opportunities for Mars transfers arise around every 25-26 months, and that these transfers are subdivided into different classes, one that is a bit faster, with typically around 5-8 months and the other that takes about 7-11 months. There are also transfers that take a lot longer, but I’m not talking about those here. Mostly, but not always, the second, slower one turns out to be more efficient energy-wise. A rule of thumb is that the transfer to Mars takes around as long as the human period of gestation, approximately 9 months. But that really is no more than an approximate value; you still have to do all the math to find out what applies to a specific date.

Why are journey times a lot slower for spacecraft intending to orbit or land on the target body e.g. Mars compared to those that are just going to fly by?

If you want your spacecraft to enter Mars orbit or to land on the surface, you add a lot of constraints to the design problem. For an orbiter, you have to consider the significant amount of propellant required for orbit insertion, while for a lander, you have to design and build a heat shield that can withstand the loads of atmospheric entry. Usually, this will mean that the arrival velocity of Mars cannot exceed a certain boundary. Adding this constraint to the trajectory optimisation problem will limit the range of solutions you obtain to transfers that are Hohmann-like. This usually leads to an increase in transfer duration.

The problems with calculating travel times to Mars

The problem with the previous calculations is that they measure the distance between the two planets as a straight line. Traveling through the farthest passing of Earth and Mars would involve a trip directly through the sun, while spacecraft must of necessity move in orbit around the solar system's star.

Although this isn't a problem for the closest approach, when the planets are on the same side of the sun, another problem exists. The numbers also assume that the two planets remain at a constant distance; that is, when a probe is launched from Earth while the two planets are at the closest approach, Mars would remain the same distance away over the length of time it took the probe to travel. 

Related: A brief history of Mars missions

In reality, however, the planets are moving at different rates during their orbits around the sun. Engineers must calculate the ideal orbits for sending a spacecraft from Earth to Mars. Like throwing a dart at a moving target from a moving vehicle, they must calculate where the planet will be when the spacecraft arrives, not where it is when it leaves Earth. 

It's also not possible to travel as fast as you can possibly go if your aim is to eventually orbit your target planet. Spacecraft need to arrive slow enough to be able to perform orbit insertion maneuvers and not just zip straight past their intended destination. 

The travel time to Mars also depends on the technological developments of propulsion systems.

According to NASA Goddard Space Flight Center's website, the ideal lineup for a launch to Mars would get you to the planet in roughly nine months. The website quotes physics professor Craig C. Patten , of the University of California, San Diego:

"It takes the Earth one year to orbit the sun and it takes Mars about 1.9 years (say 2 years for easy calculation) to orbit the sun. The elliptical orbit which carries you from Earth to Mars is longer than Earth's orbit but shorter than Mars' orbit. Accordingly, we can estimate the time it would take to complete this orbit by averaging the lengths of Earth's orbit and Mars' orbit. Therefore, it would take about one and a half years to complete the elliptical orbit.

"In the nine months it takes to get to Mars, Mars moves a considerable distance around in its orbit, about three-eighths of the way around the sun. You have to plan to make sure that by the time you reach the distance of Mar's orbit, Mars is where you need it to be! Practically, this means that you can only begin your trip when Earth and Mars are properly lined up. This only happens every 26 months. That is, there is only one launch window every 26 months."

The trip could be shortened by burning more fuel — a process not ideal with today's technology, Patten said.

Evolving technology can help to shorten the flight. NASA's Space Launch System (SLS) will be the new workhorse for carrying upcoming missions, and potentially humans, to the red planet. SLS is currently being constructed and tested, with NASA now targeting a launch in March or April 2022 for its Artemis 1 flight, the first flight of its SLS rocket.

Robotic spacecraft could one day make the trip in only three days. Photon propulsion would rely on a powerful laser to accelerate spacecraft to velocities approaching the speed of light. Philip Lubin, a physics professor at the University of California, Santa Barbara, and his team are working on Directed Energy Propulsion for Interstellar Exploration (DEEP-IN). The method could propel a 220-lb. (100 kilograms) robotic spacecraft to Mars in only three days, he said.

"There are recent advances which take this from science fiction to science reality," Lubin said at the 2015 NASA Innovative Advanced Concepts (NIAC) fall symposium . "There's no known reason why we cannot do this." 

How long did past missions take to reach Mars?

Here is an infographic detailing how long it took several historical missions to reach the Red Planet (either orbiting or landing on the surface). Their launch dates are included for perspective. 

Explore NASA's lunar exploration plans with their Moon to Mars overview . You can read about how to get people from Earth to Mars and safely back again with this informative article on The Conversation . Curious about the human health risks of a mission to the Red Planet? You may find this research paper of particular interest.  

Bibliography

• Lubin, Philip. " A roadmap to interstellar flight. " arXiv preprint arXiv:1604.01356 (2016). 
• Donahue, Ben B. " Future Missions for the NASA Space Launch System. " AIAA Propulsion and Energy 2021 Forum . 2021. 
• Srinivas, Susheela. " Hop, Skip and Jump—The Moon to Mars Mission. " (2019). 

Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: [email protected].

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Nola Taylor Tillman is a contributing writer for Space.com. She loves all things space and astronomy-related, and enjoys the opportunity to learn more. She has a Bachelor’s degree in English and Astrophysics from Agnes Scott college and served as an intern at Sky & Telescope magazine. In her free time, she homeschools her four children. Follow her on Twitter at @NolaTRedd

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The Ultimate Guide to Solo Travel in Amsterdam: More than Just Gorgeous Tulips

C onsidering a solo trip in amsterdam look no further…i was there on my own and absolutely loved it. read on for everything you need to know.

This article may contain affiliate links . If you purchase through these links, I may earn a small commission at no cost to you. Thank you for your support!

Why A Solo Trip To Amsterdam Is A Great Idea

I ventured to Amsterdam alone and oh, what an adventure it was! This city, famed for its Van Gogh Museum and picturesque canals, couldn’t have been a better pick for solo travel in Amsterdam style. Why, you ask?

For starters, the atmosphere there is just so welcoming. You’ll find that traveling to Amsterdam alone doesn’t feel lonely at all. With the city center bustling with friendly faces and the Centraal Station being a hub of connections, getting around is a breeze. Safety was never a worry for me, even when exploring the vibrant Red Light District or enjoying a late-night canal cruise.

Key Takeaways:

• Amsterdam’s welcoming atmosphere: Ideal for solo travelers, including solo female travel in Amsterdam.
• Abundant attractions: From the Anne Frank House to bike tours, there’s no shortage of things to do alone in Amsterdam.
• Safety: Feel at ease exploring, knowing Amsterdam ranks high in safety for solo adventurers.

Boutique Hotel

The Craftsmen

INCREDIBLE rooms

Fantastic central location

Keukenhof & Windmill Village Guided Day Tour

Get your tulips AND windmill fix in one day!

Classic Canal Cruise with Cheese & Wine Option

Fabulous tour and very generous with the wine and cheese.

The Best Time To Visit Amsterdam

Spring in Amsterdam dazzles with its mild weather, making it an ideal time for solo travelers to explore the city. As the days grow longer and warmer, the tulip fields near Amsterdam bloom spectacularly, a sight not to be missed. During this season, tourist crowds haven’t reached their peak, offering a more relaxed atmosphere for wandering through the nine streets or taking a leisurely bike tour around the Amsterdam city center.

Notably, spring hosts a variety of local festivals, from the King’s Day celebrations in April to the Open Garden Days in June. These events provide solo travelers with an excellent opportunity to immerse themselves in Dutch culture and connect with locals and other travelers alike.

Getting To Amsterdam From Schiphol Airport

Landing at Amsterdam’s Schiphol Airport, you’ll find yourself at the gateway to one of Europe’s most enchanting cities. Several options are at your disposal to reach the heart of Amsterdam. First off, the train, a favorite amongst many, offers a swift journey to Amsterdam Centraal . Running frequently, it ensures you’re city center -bound in no time, and that too, without burning a hole in your pocket.

Buses form another viable alternative, connecting the airport with various parts of the city, marking both convenience and cost-effectiveness. The airport bus is how I traveled into Amsterdam city center and it was very easy and clean. My only advice is to check for local holidays before making your transfer plans. I unknowingly arrived during the King’s Day celebrations so the bus couldn’t take us as far into the city as normal. It wasn’t the end of the world walking several more blocks but I wish I had known beforehand.

For those prioritizing comfort, taxis and ride-share services stand ready to whisk you directly to your hotel, ensuring safety and peace of mind, especially late at night. Each mode of transport boasts its own charm, laying out Amsterdam’s welcome mat in the way that best suits your solo travel vibe.

Getting the Eurostar to Amsterdam

The idea of zipping through the countryside, crossing the channel, and arriving in Amsterdam has always captivated me. For those of us journeying from the UK, this train offers a seamless, direct path to the heart of the Netherlands. The comfort levels are high – think spacious seats and ample legroom, which means you can relax and enjoy the scenic views outside your window.

Practical Tips For Visiting Amsterdam Solo

Embarking on a solo adventure to Amsterdam? I’ve got you covered with the essentials. First off, securing a stay in well-rated establishments is key. These spots not only promise safety but also a friendly atmosphere where mingling is much easier. Dining alone might seem daunting at first. Yet, Amsterdam’s welcoming cafes and restaurants turn this into a delightful experience. Don’t hesitate to strike up conversations with locals or fellow travelers; they often share the best tips and hidden gems of the city. Remember, every solo journey opens doors to unexpected friendships and unforgettable tales.

How To Get Around Amsterdam

Navigating Amsterdam alone will be a breeze, trust me! The city boasts an incredibly comprehensive public transport system. From trams whisking you through the city center to ferries carrying you across the canal, getting around feels like part of the adventure. And let’s not forget about the iconic bikes!

Amsterdam is the city of bikes, and even though I was WAY too scared to try a bike out, I feel like joining locals in pedaling along the picturesque streets and pathways offers an authentic Dutch experience. This array of options ensures you’ll find traveling across Amsterdam not just easy but enjoyable. With everything conveniently accessible, you’ll have more time to soak in the beauty of the Netherlands’ capital, making your solo trip unforgettable.

Where To Stay as a Solo Traveler In Amsterdam

Choosing where to stay as a solo traveler in Amsterdam can make or break your trip. Central locations are golden. They put you right in the heart of Amsterdam city, with everything from the Van Gogh Museum to the bustling Dam Square just a bike ride away. I leaned towards neighborhoods like the city center and near Amsterdam Centraal for their convenience.

Very nice breakfast

Leonardo Boutique Museumhotel

Located 2 min from Rijksmuseum and Van Gogh museum

5 min walk from airport bus stop

Great restaurant

ibis Styles Amsterdam Central Station

Very close to the main rail station

Great prices

Clean and Comfortable

Where to Eat Alone in Amsterdam

Dining alone in Amsterdam opens up a world of delightful experiences. I found cozy cafes tucked away in the Nine Streets district, serving up not just coffee but engaging conversations. These spots make you feel right at home, perfect for solo travelers seeking a warm welcome. Then there are the restaurants near Centraal Station , where the service is so nice; you’ll forget you’re dining solo.

It turned out, enjoying a meal by myself gave me the freedom to truly savor the flavors of Amsterdam, from traditional Dutch dishes to international cuisine. It’s the blend of friendly locals and inviting atmospheres that makes eating alone here not just easy but enjoyable.

Here are a few of my favorites:

• Foodhallen : Incredibly fun food hall where you can try a bunch of different things. This was a really easy choice as a solo traveler if you’re intimidated by sitting in a traditional restaurant alone.
• SUMO Sushi Amsterdam Leidseplain : This sushi place is epic and it was right near my hotel which was a problem. Haha! They do a really fun “unlimited” sushi special where you order rounds of small bites off a tablet. Highly recommend.
• If you’re spending a couple days in the museum district then I would recommend the Rijksmuseum Café and outside the Rijksmuseum there is a lovely park with a bunch of food vendors set up. If the weather is nice, it’ll be packed but worth it!

Safety Tips For Solo Female Travelers To Amsterdam

I often heard tales about Amsterdam’s thrilling nightlife and cobblestone streets, brimming with history and culture. As a solo female traveler, navigating these experiences safely became my top priority. Embracing Amsterdam wasn’t just about the adventure; it was also about ensuring a smooth journey.

Amsterdam’s reputation as a friendly and safe city for women traveling alone precedes it, yet taking a few precautions can enhance this experience. Always stay in well-lit areas at night and keep an eye on your belongings, especially in crowded places like Centraal Station or Dam Square.

Public transport offers a reliable way back to your accommodation after a long day of exploring the Nine Streets or enjoying a canal cruise. But, if I ever felt uncomfortable I would use a ride-sharing app that offers peace of mind so that I can prepay and track my journey.

Furthermore, bonding with fellow travelers or locals can transform your trip. Hotels and guided tours, especially those emphasizing Amsterdam’s rich art scene with visits to the Van Gogh Museum or Anne Frank House, provide excellent opportunities for connection. Simply put, being cautious yet open ensures your Amsterdam solo adventure will be as safe as it is unforgettable.

The Best Things to Do in Amsterdam as a Solo Traveler

Amsterdam, a city famous for its rich history and vibrant culture, offers a plethora of activities that make traveling alone an adventure to cherish. Exploring the iconic Van Gogh Museum gave me an intimate glimpse into the troubled genius’s world, a must for any art lover. The tranquility contrasted with the bustling Centraal Station , where I marveled at the blend of Gothic and Renaissance architecture.

Walking through the Nine Streets , I could pretend to be a local as I people watched everyone going about their daily lives. But nothing compared to the serenity of a canal cruise at dusk. Gliding through waterways, I watched Amsterdam’s cityscape transition from day to night, a truly magical experience. Lastly, no solo journey here would be complete without savoring Dutch delicacies at a cozy local market , where food not only tastes but also tells stories.

Explore a Local Amsterdam Museum or Three

Embarking on solo travel in Amsterdam opened my eyes to the rich tapestry of culture and history that is inseparable from the city’s very essence. Museums, I discovered, form the heart of this tapestry. The Van Gogh Museum beckoned with its colorful whirls of paint, whispering tales of brilliance and madness. Nestled within its walls, I felt a connection to the art that was both personal and profound.

I would definitely recommend setting aside at least half a day if not longer for the Rijksmuseum . There was so much to see it was overwhelming but if you make a list of your priorities you’ll end up with a good strategy on how to conquer this GINORMOUS museum.

Not far away, the Anne Frank House stood as a somber reminder of the resilience of the human spirit. Walking through its secret annex, I could almost hear the echoes of the past, a poignant narrative of hope amidst despair. Pro tip: Do NOT wait to buy your tickets. The Anne

Spend time at the Royal Palace of Amsterdam

I have always been fascinated by the rich tapestry of history and architecture that European cities offer. On my trip to Amsterdam, I made sure to schedule a visit to the Royal Palace . Nestled in Dam Square, this majestic beauty stands as a testament to the grandeur of Dutch monarchy and artistry. I remember walking through its opulent halls, each corner telling a story of a bygone era.

What struck me the most was how every detail, from the intricate carvings to the lavish furnishings, reflected the deep-rooted cultural heritage of the Netherlands. A visit there isn’t just a step back in time; it’s a deep dive into the heart of Dutch identity. I urge you to not miss out on this gem in the heart of Amsterdam city.

Unforgettable Things To Do In Amsterdam As A Solo Traveler

Amsterdam offers a plethora of unique experiences that make solo travel incredibly rewarding. Visiting the Red Light District might seem daunting at first, but it’s a uniquely Amsterdam experience you shouldn’t miss. It will challenge your perspectives and is a testament to the city’s open-minded culture. On the other hand, joining a local food tour will not only satiate your taste buds with delicious Dutch delights but also introduce you to fellow travelers and locals.

These activities exemplify the thrill of discovery and exploration inherent to solo travel in Amsterdam. Amsterdam’s friendly vibe and safe streets further enhance the joy of uncovering the city’s hidden gems on your own. Whether it’s cycling by the canal, admiring Van Gogh’s masterpieces, or soaking in the architectural beauty of Amsterdam Centraal, doing these alone adds a personal touch to the memories you’ll cherish forever.

Best Tours For Solo Travel in Amsterdam

Rotterdam, Delft & The Hague Guided Day Tour

Venture outside of Amsterdam and experience a little more of the Netherlands!

Amsterdam unfurls a mosaic of experiences for the solo traveler, each infused with the spirit of exploration and connection. Bike tours beckon with the promise of wind in your hair as you meander through the nine streets and beyond. They offer a unique vantage point of Amsterdam city, from bustling Centraal Station to the serene canals, making every pedal a story.

Equally enriching, walking tours guide you through Amsterdam’s heart, from the historic Anne Frank House to the vibrant Dam Square. Solo travelers find these guided trips a treasure trove of local insights, anecdotes, and hidden gems. It’s not just about the sights; it’s the stories behind them, the whispered legends of the Red Light District, and the artistic legacy of the Van Gogh Museum that spring to life.

Each step or pedal in Amsterdam offers solo adventurers a blend of freedom and camaraderie. You’ll mingle with fellow wanderers and locals, transforming your travel into an anthology of shared moments and smiles.

FAQ for Solo Travel in Amsterdam

What’s the best time to visit amsterdam solo.

Spring Charm : April to May, when the tulips are in full bloom, painting the city in vibrant colors. It’s a sight that’s truly uplifting for the soul!

Autumn Colors : September to November, offering cooler weather and fewer crowds, perfect for leisurely explorations and cozy cafe visits.

Is Amsterdam safe for solo travelers?

Absolutely! Amsterdam is renowned for its high safety standards. Here are a few tips to keep your trip smooth:

Stay Aware : Keep your belongings close in busy areas like the Centraal Station or the Dam Square.

Night Moves : Feel confident exploring at night, but stick to well-lit, populated areas.

Local Numbers : Keep emergency numbers handy, just in case.

Can I get by with English in Amsterdam?

Yes, you can! The Dutch are fantastic English speakers. Signs, menus, and public transport announcements are often in English, making it super easy to navigate the city.

Any tips for dining alone in Amsterdam?

Cafe Culture : Amsterdam’s cafes are welcoming spots to enjoy a meal alone with a book or your thoughts.

Street Eats : Grab a stroopwafel or herring from a street vendor for a delicious snack on the go.

Bar Seats : Many restaurants have bar seating, perfect for solo diners to feel less conspicuous.

Or check out my favs above!

What’s the best way to get around Amsterdam solo?

I’d say walking, public transit and biking are the best ways to get around. Amsterdam is very compact making it incredibly walkable!

Any solo travel safety tips specific to Amsterdam?

Bike Safety : Familiarize yourself with local cycling rules to stay safe on the road.

Pickpocketing : Be mindful of your belongings in crowded places.

Accommodation : Choose well-reviewed accommodations in safe areas.

Final Thoughts on Solo Travel in Amsterdam

I remember stepping outside Schipol Airport, heart racing with excitement. Amsterdam awaited me, a solo traveler thirsty for adventure and personal growth. This city, steeped in history and brimming with life, never once made me feel alone. If you’ve ever dreamed of navigating the enchanting canals, marveling at masterpieces in the Van Gogh Museum, or savoring a quiet moment in the Anne Frank House, let me assure you, doing it solo only adds to the charm.

The freedom of planning my days, choosing whether to walk through the Nine Streets or embark on a canal cruise, taught me a lot about myself. I discovered resilience in navigating public transport and the joy of connecting with locals and fellow travelers at a cozy cafe or a lively brewery. Amsterdam offered me a blend of tranquility and exhilaration that I hadn’t experienced anywhere else.

So, to anyone contemplating a trip to Amsterdam alone, whether you’re drawn to the vibrant city life, the rich tapestry of art and history, or the simple pleasure of a Dutch pancake by the canal, embrace it with all your heart. The memories of your solo journey will be as colorful and unforgettable as the city itself. Amsterdam doesn’t just welcome solo travelers; it celebrates them.

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This City Was Just Named the Best in the World for Nightlife — and it's a Stunning South American Destination

A visit to Rio de Janeiro isn’t just about Christ the Redeemer and the Copacabana, but experiencing the partying way of life.

Gonzalo Azumendi/Getty Images

Rio de Janeiro has long had a reputation for being one of the most epic party cities on the planet — and it still lives up to the hype, earning the Brazilian coastal city the No. 1 spot in Time Out’s World’s Best Cities for Nightlife for 2024. Yet these days, life after dark comes with some innovative twists. “Gone are the days when nightclubs were the go-to places at night in Rio de Janeiro,” Time Out Rio de Janeiro editor Renata Magalhães said of the rankings . “In the lively Botafogo district, up-and-coming gastronomic hotspots like Alba and Vian Cocktail Bar , become dance floors on the weekends, and the streets have never been livelier since the end of the pandemic.” While the festive atmosphere has always filled the city during the Rio Carnival, typically held in February and March, those vibes are now spilling off the dance floors year-round, making it always the right time to enjoy the Brazilian nightlife. Magalhães added that the beats of samba de rodas , the country’s best-known musical form, which includes music, dance, and poetry and was inscribed on UNESCO’s   Representative List of the Intangible Cultural Heritage of Humanity in 2008 , echoes throughout the city, from areas like Glória to the Port Zone. She also called out Morro do Pinto as the newest trendy area, while the timelessness of Lapa still enchants locals and visitors alike, especially at Bar da Cachaça and Beco do Rato

“ Suru Bar has become one of my favorites in the area, drawing crowds every night of the week for its Brazilian-inspired cocktails and sensational vibes,” she added. Time Out curated the list by surveying thousands of people in hundreds of cities. They were asked to name their favorite venues and experiences, as well as rank the quality and affordability of nightlife. Rio amassed an impressive 90 percent quality score, while also snagging high marks in affordability. Respondents also called out the plethora of live music and dance halls, as well as Lapa’s bohemian bars, and the city's spontaneous outdoor samba parties. 

Earlier this year, Magalhães also named Rio's best bars , including psychedelic garage-themed Hocus Pocus DNA , bookstore-bar hybrid Al Farabi ,  Liz Cocktails & Co with pop-culture inspired drinks, Madeira Island-inspired Adega Pérola , and fun-loving Boteco do Raoni .

Also making the Time Out list for best nightlife cities of 2024 were Manila, Philippines in second; Berlin in third; and Guadalajara, Mexico, in fourth. The only American city on the list was Austin, snagging the fifth-place spot. 

With 13 cities on five continents, the list also included Lagos, Nigeria, and Accra, Ghana, in Africa; Rotterdam, Netherlands; Manchester, England; and Budapest in Europe; Taipei and Singapore in Asia; and Buenos Aires in South America.

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