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Physics LibreTexts

5.1.1: Speeds of Different Types of Waves

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  • Kyle Forinash and Wolfgang Christian

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The speed of a wave is fixed by the type of wave and the physical properties of the medium in which it travels. An exception is electromagnetic waves which can travel through a vacuum. For most substances the material will vibrate obeying a Hooke's law force as a wave passes through it and the speed will not depend on frequency. Electromagnetic waves in a vacuum and waves traveling though a linear medium are termed linear waves and have constant speed. Examples:

  • For sound waves in a fluid (for example air or water) the speed is determined by \(v=(B/\rho )^{1/2}\) where \(B\) is the bulk modulus or compressibility of the fluid in newtons per meter squared and \(\rho\) is the density in kilograms per cubic meter.
  • For sound waves in a solid the speed is determined by \(v= (Y/\rho )^{1/2}\) where \(Y\) is Young's modulus or stiffness in Newtons per meter squared and \(\rho\) is the density in kilograms per meter cubed.
  • For waves on a string the speed is determined by \(v=(T/\mu )^{1/2}\) where \(T\) is the tension in the string in Newtons and \(\mu\) is the mass per length in kilograms per meter.
  • Although electromagnetic waves do not need a medium to travel (they can travel through a vacuum) their speed in a vacuum, \(c = (1/\mu _{o} ε_{o})^{1/2} = 3.0\times 10^{8}\text{ m/s}\) is governed by two physical constants, the permeability \(\mu_{o}\) and the permittivity, \(ε_{o}\) of free space (vacuum).

Table \(\PageIndex{1}\)

Here is a more comprehensive list of the speed of sound in various materials .

As we saw in the previous chapter, there is a relationship between the period, wavelength and speed of the wave. The period of a cork floating in the water is affected by how fast the wave passes (wave speed) and the distance between peaks (wavelength). The relationship between speed, period and wavelength of a sine wave is given by \(v=\lambda /T\) where wavelength and period for a sine wave were defined previously. This can also be written as \(v=\lambda f\) since frequency is the inverse of period and is true for all linear waves. Notice that, since wave speed is normally a fixed quantity the frequency and wavelength will be inversely proportion; higher frequencies mean shorter wavelengths.

Often it is easier to write \(ω = 2πf\) where \(\omega\) is the angular frequency in radians per second instead of having to write \(2\pi f\) everywhere. Likewise it is easier to write \(k=2\pi /\lambda \) where \(k\) is the wave number in radians per meter rather than having to write \(2\pi /\lambda\) a lot. (Note that \(k\) is not a spring constant here.) Using these new definitions the speed of a wave can also be written as \(v=f\lambda =\omega /k\).

If the medium is uniform the speed of a wave is fixed and does not change. There are circumstances where the speed of a particular wave does change, however. Notice that the speed of sound in air depends on the density of the air (mass per volume). But the density of air changes with temperature and humidity. So the speed of sound can be different on different days and in different locations. The temperature dependence of the speed of sound in air is given by \(v = 344 + 0.6 (T - 20)\) in meters per second where \(T\) is the temperature in Celsius (\(T\) here is temperature, not period). Notice that at room temperature (\(20^{\circ}\text{C}\)) sound travels at \(344\text{ m/s}\).

The speed of sound can also be affected by the movement of the medium in which it travels. For example, wind can carry sound waves further (i.e. faster) if the sound is traveling in the same direction or it can slow the sound down if the sound is traveling in a direction opposite to the wind direction.

Electromagnetic waves travel at \(\text{c} = 3.0\times 10^{8}\text{ m/s}\) in a vacuum but slow down when they pass through a medium (for example light passing from air to glass). This occurs because the material has a different value for the permittivity and/or permeability due to the interaction of the wave with the atoms of the material. The amount the speed changes is given by the index of refraction \(n=c/v\) where \(c\) is the speed of light in a vacuum and \(v\) is the speed in the medium. The frequency of the wave does not change when it slows down so, since \(v=\lambda f\), the wavelength of electromagnetic waves in a medium must be slightly smaller.

Video/audio examples:

  • What is the speed of sound in a vacuum? Buzzer in a bell jar . Why is there no sound when the air is removed from the jar?
  • Demonstration of speed of sound in different gasses . Why is there no sound when the air is removed from the jar?
  • These two videos demonstrate the Allasonic effect. The speed of sound is different in a liquid with air bubbles because the density is different. As the bubbles burst, the speed of sound changes, causing the frequency of sound waves in the liquid column to change, thus changing the pitch. Example: one , two . What do you hear in each case?
  • The Zube Tube is a toy that has a spring inside attached to two plastic cups on either end. Vibrations in the spring travel at different speeds so a sound starting at one end (for example a click when you shake the tube and the spring hits the cup) ends up changing pitch at the other end as the various frequencies arrive. In other words this is a nonlinear system. See if you can figure out from the video which frequencies travel faster, high frequencies or low.

Mini-lab on measuring the speed of sound .

Questions on Wave Speed:

\(f=1/T,\quad v=f\lambda ,\quad v=\omega /k,\quad k=2\pi /\lambda,\quad \omega =2\pi f,\quad y(x,t)=A\cos (kx-\omega t+\phi ),\quad v=\sqrt{B/Q}\)

  • Light travels at \(3.0\times 10^{8}\text{ m/s}\) but sound waves travel at about \(344\text{ m/s}\). What is the time delay for light and sound to arrive from a source that is \(10,000\text{ m}\) away (this can be used to get an approximate distance to a thunderstorm)?
  • What two mistakes are made in science fiction movies where you see and hear an explosion in space at the same time?
  • Consult the table for the speed of sound in various substances. If you have one ear in the water and one ear out while swimming in a lake and a bell is rung that is half way in the water some distance away, which ear hears the sound first?
  • At \(20\text{C}\) the speed of sound is \(344\text{ m/s}\). How far does sound travel in \(1\text{ s}\)? How far does sound travel in \(60\text{ s}\)?
  • Compare the last two answers with the distance traveled by light which has a speed of \(3.0\times 10^{8}\text{ m/s}\). Why do you see something happen before you hear it?
  • The speed of sound in water is \(1482\text{ m/s}\). How far does sound travel under water in \(1\text{ s}\)? How far does sound travel under water in \(60\text{ s}\)?
  • What happens to the speed of sound in air as temperature increases?
  • Using the equation for the speed of sound at different temperatures, what is the speed of sound on a hot day when the temperature is \(30^{\circ}\text{C}\)? Hint: \(v = 344\text{ m/s} + 0.6 (T - 20)\) where \(T\) is the temperature in Celsius.
  • Using the speed of sound at \(30^{\circ}\text{C}\) from the last question, recalculate the distance traveled for the cases in question four.
  • Suppose on a cold day the temperature is \(-10^{\circ}\text{C}\: (14^{\circ}\text{F}\)). You are playing in the marching band outside. How long does it take the sound from the band to reach the spectators if they are \(100\text{ m}\) away?
  • What is the difference in the speed of sound in air on a hot day (\(40^{\circ}\text{C}\)) and a cold day (\(0^{\circ}\text{C}\))?
  • What would an orchestra sound like if different instruments produced sounds that traveled at different speeds?
  • The speed of a wave is fixed by the medium it travels in so, for a given situation, is usually constant. What happens to the frequency of a wave if the wavelength is doubled?
  • What happens to the wavelength of a wave if the frequency is doubled and has the same speed?
  • Suppose a sound wave has a frequency \(200\text{ Hz}\). If the speed of sound is \(343\text{ m/s}\), what wavelength is this wave?
  • What factors determine the speed of sound in air?
  • Why do sound waves travel faster through liquids than air?
  • Why do sound waves travel faster through solids than liquids?
  • The speed of sound in a fluid is given by \(v=\sqrt{B/Q}\) where \(B\) is the Bulk Modulus (compressibility) and \(Q\) is the density. What happens to the speed if the density of the fluid increases?
  • What must be true about the compressibility, \(B\), of water versus air, given that sound travels faster in water and water is denser than air?
  • The speed of sound in a fluid is given by \(v=\sqrt{B/Q}\) where \(B\) is the Bulk Modulus (compressibility) and \(Q\) is the density. Can you think of a clever way to measure the Bulk Modulus of a fluid if you had an easy way to measure the speed of sound in a fluid? Explain.
  • The speed of sound on a string is given by \(v=\sqrt{T/\mu}\) where \(T\) is the tension in Newtons and \(\mu\) is the linear density (thickness) in \(\text{kg/m}\). You also know that \(v=f\lambda\). Give two ways of changing the frequency of vibration of a guitar string based on the knowledge of these two equations.
  • For the previous question, increasing the tension does what to the frequency? What does using a denser string do to the frequency?
  • The following graph is of a wave, frozen in time at \(t = 0\). The equation describing the wave is \(y(x,t)=A\cos (kx-\omega t+\phi )\). Sketch the effect of doubling the amplitude, \(A\).

clipboard_e5f764e637575a65b45b9f0eb09115dd2.png

Figure \(\PageIndex{1}\)

  • For the following graph of a wave, sketch the effect of doubling the wavelength.

clipboard_e37815ebeb535ef7dffe9296d845d3d06.png

Figure \(\PageIndex{2}\)

  • The mathematical description of a sine wave is given by \(y(x,t)=A\cos (kx-\omega t+\phi )\). Explain what each of the terms \((A, k, \omega, \phi )\) represent.

Universe Today

Universe Today

Space and astronomy news

radio waves travel fastest in

Device Makes Radio Waves Travel Faster Than Light

[/caption] A scientist has created a gadget that can make radio waves travel faster than light . Einstein predicted that particles and information can’t travel faster than the speed of light, but phenomena like radio waves are a different story, said John Singleton, who works at the Los Alamos National Laboratory. The polarization synchrotron combines the waves with a rapidly spinning magnetic field, and the result could explain why pulsars — which are super-dense spinning stars that are a subclass of neutron stars — emit such powerful signals, a phenomenon that has baffled many scientists.

Singleton said the polarization synchrotron basically abuses radio waves so severely that they finally give in and travel faster than light. This may be what happens in pulsars, as well. “Pulsars are rapidly rotating neutron stars that emit radio waves in pulses, but what we don’t know is why these pulses are so bright or why they travel such long distances,” Singleton said. “What we think is these are transmitting the same way our machine does.”

The device consists of a 2 meter-long gently curving arc of alumina (a dielectric material), with a series of electrodes fitted at regular intervals along its length. Applying a sinusoidal voltage across each electrode and displacing the phase of the voltage very slightly from one electrode to the next generates a sinusoidally-varying polarization pattern that moves along the device. By carefully adjusting the frequency of the voltage and the phase displacement the researchers say they can make the wave travel at greater than the speed of light. However no physical quantity of charge travels faster than light speed.

And beyond explaining what has been a bit of a mystery to the astronomical community, Singleton’s discovery could have wide-ranging technological impacts in areas such as medicine and communications, he said.

“Because nobody’s really thought about things that travel faster than light before, this is a wide-open technological field,” Singleton said.

One possible use for faster than light radio waves — which are packed into a very powerful wave the size of a pencil point — could be the creation of a new generation of cell phones that communicate directly to satellites, rather than transmitting through relay towers as they now do.

Those phones would have more reliable service and would also be more difficult for hackers to intercept, Singleton said.

Speedy radio waves could also revolutionize the computing industry. Data could be transferred more quickly, and if used in semiconductors, it would mean faster caches and the ability to communicate across separate pieces of silicon nearly instantly.

In the health field, faster than light radio waves could be in extremely targeted chemotherapy, where a patient takes the drugs, and the radio waves are used to activate them very specifically in the area around a tumor, Singleton said.

Read the paper on the Polarization Synchrotron.

Sources: Current, Geek.com , Roland Piquepaille’s Technology Trends

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29 Replies to “Device Makes Radio Waves Travel Faster Than Light”

I’ve heard of this phenomenon before, and it should be noted while the waves travel (or appear to travel) faster than light, information that can be transmitted by these waves cannot (it goes regular light speed or slower). Therefore, we’re not seeing a breakdown of the laws of physics here, nor is this really all that new an idea. It’s probably just a new implementation.

Agreed. The speed of light is a fundamental limit on causality. No causal signal or information can travel faster. In this case what is travelling faster than light is a phase, but not information.

Is’all greek to me as I don’t understand much of anything about this or how it violates causality and laws of the universe to find loopholes in Einsteins theories.

What I don’t understand most tho is how something can be moving faster than the speed of light, and we are aware of this somehow, but that something carries no information (when its existence is information).

Is this just a quirky thing that happens on a bench or can we someday look forward to FTL Morse code from mars?

This article is very confusing as written. The paragraph about using this phenomenon to speed up data processing in computers clearly indicates that this can be used to convey information faster. Even if only a portion of the wave is moving faster than light speed, that is still significant. Even though the signal itself cannot carry information the signal itself can be the information. If it’s delivery can be varied in any particular way then that variance can be translated into a message very easily. Granted such a message would not be secure but that isn’t always the point. Perhaps we are beginning to see the advent of “subspace communication” or ftl messaging.

“What I don’t understand most tho is how something can be moving faster than the speed of light, and we are aware of this somehow, but that something carries no information (when its existence is information).”

It’s existence could be thought of as providing information – i.e. Does this radio wave exist? > I can detect it > Yes it does. > OK – that provides me with information.

However, what we are interested in here is the transmission of non-random information from one place to another. To do this, you have to modulate the signal somehow to allow the wave to carry information. Here it gets technical, but suffice it to say that the modulated wave packet travels more slowly than the phase velocity of the wave in question.

It gets very involved with a lot of subtle points. It confuses and trips up many an intelligent physicist. I certainly don’t too much beyond the basics…

Maxwell – try this thought (or real) experiment:

Take a laser pointer, and point it at the moon. Next, swing the laser so it traverses the moon in about a 1/100 of a second. (that’s equivalent to about one complete revolution of your hand every 3 seconds).

The spot of the laser pointer is moving across the lunar landscape at approximately the speed of light!

Want to go faster? either swing your arm faster, or aim for Mars…

Just like in this device, no information is transmitted from one side of the moon to the other.

(Just thought of another – if you pre-program the audience, you can make a stadium wave move faster than the speed of light too!)

On the causality thing, I don’t think it would be a violation. The speed of light is fast but its not instantaneous. I’d figure a signal could be faster, blisteringly faster, and still never arrive before it was sent. It would simply arrive before a light based signal did.

We are not the center of time any more than we are the center of the universe.

Greg: but that’s just the problem; at no point does this process push information even a tiny bit faster than light. The phase that this article describes can only transfer information about one part to the Universe to another at the speed of light or less; no faster. This article is very misleading about the wording it uses in addition to the implied result it present. This article may as well be about the invention of a perpetual motion machine.

I know there’s a good article out there that states that Special Relativity and FTL imformation transfer cannot co-exist but my Google-Fu is failing me tonight. Basically, if Special Relativity is true, the FTL information transfer cannot be, and vice versa. What the argument boils down to is that Special Relativity dictates that the receiver would get the signal before the transmitter sent it, and can do something to disrupt the signal before it is sent by the transmitter, thus preventing the receiver from getting the signal, etc, etc. That would obviously violate casuality and create a paradox, which would make the scenario impossible.

Can anyone help me find that article? Parts of it got math-y, but it was a very good description of the problem posed by FTL information transfer.

This is the kind or article that you either disregard or perhaps glance through to see how the original informants are trying to mess with their readers mind.

Note that the paper is from -04, which means that the research has emptied out the possibilities of their setup. Since the research isn’t interesting they are probably trying to wake interest by bloviating on technological possibilities, which in turn also seems to have awoken little interest.

I see that many have anticipated much of the rest of my kvetch on this.

This article is very confusing as written.

Greg, they are trying to shuffle the cards fast. First, as CEB notes you can yourself recreate such signal sweeps. I don’t think it is meaningful to speak about the apparent speed or phase of the wavefront since you, the observer, is recronstructing global information, and elsewhere. There is no local observer! So no break with relativity, but also no meaningful way of discussing this.

Second, AFAIU these types of phenomena is often seen in astronomy too, where for example jets seen at an angle seems to travel superluminally. The difference is, I think, that no astronomer would term it “superluminal”?!

As for technological possibilities, it is true that electrical signals in narrow conductors limit signaling and global clock reconstructions over large circuit boards. Even in a free conductor a voltage signal would go with 2/3 of light speed due to vacuum inductance. This is why optic signaling is tried, with (directed signaling) or without fiber (omni-directional signaling).

What these researcher have observed is a narrow lobe 1/R field, which is reminiscent of the near field behavior. For comparison a “wide” mono-lobe (spherical field) displays the well known 1/R^2 behavior.

If it is an extended near field, which by all means is an interesting phenomena by itself, I doubt that it can be used for fast communication. Near fields close to an antenna by definition hasn’t yet coupled the electric and magnetic field. There are thus no real photons (coupled E and M field), only virtual non-observable ones and little energy transfered (thus the 1/R behavior). Signals would look different at different positions and times, and hopeless to decode.

But even if it is instead a halfway house to a transmitted signal akin to a narrow laser “lobe” (ideally no energy leak with R at all) it can never be as effective or easy to make.

[The reason a wide near field effect would be interesting is IMO that _that_ probably has technological applications. Near field microscopy/pattern transfer has resolution way below the wavelength of the used light. If so, this is then perhaps the only thing the press release/article gets right – perhaps these things, by stacking energy faster than it normally dissipates in confined directions, can achieve superior radio/chemotherapy.]

No, it wouldn’t help to imagine a faster process, then that simply would be “light”. Einstein realized that there must be a fastest signal, and that it is tied into how space and time works. It is rather easy to identify that fields that have infinite range (which means their interactions are mediated by massless particles: EM, gravity) transmit at this speed. [“rather easy” reads, as usual, as: “I’m sure I have seen this beautiful argument somewhere somewhen, but I can’t remember or reconstruct it.” :-)]

Unfortunately I dunno about such a good article. But I have one old link somewhere to an article how superluminal signals in general would destabilize your typical gauge field.

Then we have computer scientist Scott Aaronson’s testable hypothesis against time travel, which would work against superluminal signaling too. If such beasts exist they could be used to deflate computer science tower of algorithmic difficulty. In other words, we would instantly know everything. We don’t, so they don’t (exist).

That type of gedanken experiment reminds me of that old maxim, roughly and generally “space exists so that not everything happens here, and time exists so it doesn’t all happen to me”. I recently saw it attributed to Einstein, which if true would be a delicious happenstance.

This reminds me of quantum mechanics and the interpretation of particles being waves. The “particle” is made up of many waves. These waves travel with different phase-velocities and can be faster than the speed of light. But a single wave is not transporting any information about the particle. It is the group of waves that counts and the corresponding group-velocity is always less than the speed of light…

Thanks, this makes alot more sense than the article did. I’ll try to put this in simplified concrete terms. If such a signal could be sent over a long distance then essentially what an observer would see would be random signals and there would be no way to control the delivery to convey a message. But on second thought the observer would see nothing even though part of the waveform was sent and would only detect the signal when the rest of the wavefrom arrived at light speed.

Hmmm. I have always came back to the ideal in my little brain that gravity has been the one thing that does not have speed. Or….maybe it simply moves or JUST IS within the universe. It does bend light. So my question is…is gravity a phase or a wave or a particles? Or all three, it does seem to break ‘Einstein’s Rule’. Maybe. I can not be completely held down to the thought that ‘nothing moves faster then the speed of light’. I think we have just begun to figure out the physics of the universe. I do think this is a new way to come at an old ideal and should make us think…all rules can be ‘broken’. A friend of mine said once that light is massless, and gravity present mass, sort of like a rock in the middle of a fast moving stream, the water is the light and the force that stream is moving is the ‘energy…and the rock is the gravity, the water [light] does flow [bend] around it. He was trying to break the ideal down so I could understand it. He said if you are standing on that rock, nothing can move faster then that ‘stream’ , the speed of light. Until we figure out an angle, or another way of seeing the physics of light, Einsten’s rule, we thinks can’t be broken. Tho the speed of light is a hard one to break. Which swings me back to gravity. I just don’t know. Now remember everyone, you are dealing with a person with a little brain, that is now even more confused. Thanks

I request an Astronomy Cast about this subject!! 🙂

Really, so it´s possible to send information faster than speed of light? As far as I know (and understood about the article) it breaks some known physical laws, doesnt it? I will read the paper and than I post what I find out…

When you throw a rock in water, waves carry the disturbance across the pond, in the form of a growing ring. If you look very carefully, you will notice that each individual wave (‘phase’) moves faster than the ring (‘group’). Waves appear to ‘be born’ on the inside edge of the ring, grow and move outward faster than it, then dissipate and disappear on the outside edge. The ‘information’ about the rock fall, as well as what energy can be harnessed from it, crosses the pond at the speed of the ring, not the waves’. Waves on water behave like this because the system (fluids boundary under gravity) is highly ‘non-linear’ – (= complex; as strange as it may seem, it is so difficult to calculate analytically, as to be in fact impossible).

Light in ordinary media does not behave that way, it is ‘linear’; phase and group speeds are equal (= c in vacuum, = c/n in a medium where n is the refraction index of that medium; n>1). But it is possible to find, and even make, weirdly non-linear media for light, and radio-waves. If you can make nc! This is then just for phase velocity, which cannot carry information: only the group of waves does.

The system described in this article does just that: by modifying its properties along with the passing wave, it interacts with the wave in a very non-linear way.

Two more things about relativity. 1- Of course, as just any other physics theory, it is only valid within its domain of tested verification, to the extent of the precision of the best observations, and until otherwise proved (‘falsified’). It may happen, and it may not.

Until it happens, relativity is a good tool to understand the place we live, but it is not very intuitive.

2- The notion that ‘it is not possible to go faster than light’ is over-simplified, and misses the point. It tends to lead to meaningless ‘what-ifs’. c is much more than ‘the speed of light’: it is the ‘space-time constant’, the ratio between time and space (which relativity states are related, and not independent as our intuition would have it).

Light happens to travel at c (in a vacuum), because c is also a ratio between electrical and magnetic properties of vacuum, because light happens to be electro-magnetic waves (propagating vibrations of the electric and magnetic fields, just like vibrations of the surface of water propagates) and because electric and magnetic fields are space- and time-derived from each other (this was stated by JC Maxwell).

(btw, gravity probably also travels at c, but this has not been observed yet.)

Einstein’s idea is that c is a constant for all observers. This is much deeper, and in fact much more surprising, than the better-known idea of ‘no faster than c’. Suppose you drive a spaceship at c/4, heading for the klingon ship in front. That ship is travelling towards you at c/2. Both ships fire their laser cannons. Q: What will each of you, as well an an innocent bystander, measure for the speed of these rays of doom? A: c! All of you, for both rays of light! And not c+c/2, c-c/2, c+c/4, c-c/4 you would observe in a newtonian universe. c is really constant.

What this actually means, is that speed is a very, very different thing from the notion we have of it. All that exists is a link between time and space, which is different for each observer. This link means that, among other things, V>c is not only impossible, but physically meaningless, for any observer. Think of it as a sort of rotation between observers, such as one observer’s ‘time’ becomes mingled with another’s ‘space’.

Sorry, that was long…

This was the best I can find so far about the whole subject. Now that I realized my previous error (I confused the terms casualty and causality [Bad Dave! No cookie for you!]), I’m finding more useful references to the whole subject.

…long but interesting!

Hey, there was a bug with > and < !

"But it is possible to find, and even make, weirdly non-linear media for light, and radio-waves. If you can make nc!"

should read:

"If you can make n smaller than 1, then V larger than c!"

I have a comment that I would like to inject here, not so much about the article as much as about a few of the comments. Repeatedly a few folks have stated that “nothing can travel faster than light” in reference to Einstein’s theories and these comments are being stated as an undeniable fact. I wanted to address this because these comments also insinuate that if nothing can travel faster than light, well then “what’s the point of even trying?” and to me this is a very sad view of things. To me attitudes such as this simply say that we’re in for a very lonely existence on this planet and that there’s really no point to any of this. After all, why even look at the stars if we can NEVER visit them…what’s the point?

I’m not going to debate any of the science in regards to this with anyone here…I barely understand any of Einstein’s theories to begin with. I will say however that as I understand it, while Einstein was certainly right about most things, as far as I know this concept about travel and light is still a theory…it has NOT been conclusively proven beyond a shadow of a doubt yet. That said, we can’t allow ourselves to fall victim to a belief that it’s simply “not possible”. For years the “experts” swore up and down that the Earth was flat. For many more years most folks, including the experts thought it was impossible for “man to fly” let alone reach the moon…until someone proved them wrong.

If we give up the effort based on the belief that it’s not possible, we may be sacrificing something truly great. Further, even if it turns out that it’s not possible, what other truly wonderful things could be discovered in the attempt…things that may not be discovered if we simply “give up because it’s not possible”.

Anyways, I’m sure this isn’t going to change the opinion of any of the experts who are so positive that faster than light travel isn’t possible…they have gotten so wrapped up in their facts, science and mathematics that they have forgotten how to dream. For the rest of you though, please don’t give up “the dream” simply because others don’t think it’s possible. We have to dream of the possibilities before we can ever achieve them! Hopefully one day someone will be able to prove the experts, including Einstein wrong.

Just some thoughts from a dreamer 🙂

to: Iomitus

I’m all for dreaming but it has been determined experimentally that a particle moving at a velocity close to the speed of light is much more massive than one at a lower velocity. So the closer you get to c the more massive it becomes and the more energy it takes to go faster until takes infinite energy as you get infinitely close to c.

Face it, Relativity describes the way the universe works.

Dreaming is good! It can lead you to very exciting things. And space travel would, indeed, be a great thing.

The problem here is, as CinIN already states, SR (special relativity) is proven without any doubts. Especially particle physics experiments have shown its effects to be real. Even such a different theory like quantum mechanics relies on SR; you need SR to achieve the correct explanation of electrons in an atom – and this has been proven, too! We must face it: SR is right and faster-than-light-travel is not possible in the conventional way. Btw: Theoretically the warp-drive of Enterprise could work! One major problem could be to put thirty solar masses into the space ship and keep it from collapsing into a black hole. But as a professor once stated: “Theoretically it works. How to build it is up to the engeneers!” 😀

I’m hesitant to open this can of worms but then curiosity killed the cat. I’m not a proponent of the EU theory but am intrigued by some of what it suggests. Is faster than light speed possible according to EU? Where is Anaconda when you need him?

I can’t believe I really just typed that…

The spped of light is not really a property of light, but of spacetime. The speed of light is where there is zero distance in spacetime (space + time), and massless particles such as photons travel along these paths or geodesics.

Phase terms can travel faster than light. Even stranger quantum entanglements can exist simultaneously. Two charged and spinning particles in an entangled states may be separated by a huge distance. If one particle is in a region with a magnetic field that particle will exhibit a precession. This is the basis of MRI. Now the other particle far removed and with no magnetic field will also precess!

Can there be a speed up of information because a phase travels faster than light? Surprisingly yes, but under certain conditions. This is the basis for quantum computers, where the entanglement of states can quantum compute in a log(time) compared to a classical computer. There is a hitch though. There has to be a classical signal transmitted to read the output of the quantum computation.

With the case of the laser pointer suppose it points at various spots on the moon. These are specific little pulses of codes and the pointer hits detectors so there is no speed of light connection between them. Each of these little detectors then processes the information and then communicates to some “hub.” In that sense you can actually have a faster communication of information. Yet it has to be remembered that no information actually travels faster than light.

Lawrence B. Crowell

This article confusing too much to me. First all all original paper was already 5 years old. Why you writing article as if this letter is quite new one? Sencond “polarization synchrotron” is not way to sending meaning data by faster than light. In short this article is not crrect by physically speaking and it looks like yellow journalism. I am sorry to say to use a such a words because of your article is always very good.

According to what Lawrence B. Crowell wrote, a pulse of light sent ftl would be detectable. If you could power your laser pointer sufficiently and make it accurate enough, one could send pulses to specific locations to a detector array and the arrangement of those locations would convey the message. Over short distances this would not matter, but over many light years it would speed up messaging considerably.

Ouch, that is not exactly what I said. You can send a phase FLT, or one can change the pointer of a laser so the spot on a target moves faster than light. The motion of this spot is not a causal propagation of information. Yet one could send a signal to distant detectors on the moon, with different phases, and these detectors then process their information and relay it to a central region. There will be a speed up of information processing, even though information has NOT actually propagated faster than light.

Quantum computers exploit nonlocality of quantum entanglements in a related way to speed up the processing of information. The architype is the controlled-NOT gate which can process entangled quantum bits.

To lomitus,

You sir are not a dreamer you are a visionary. I agree with your line of thinking. I have an explanation of why this device works as it does. You may be interested in seeing it. Please go to this Internet site, Super Relativity.org. At this site read the article How to Build a Warp Drive using SR Theory. It will explain the mechanics of the discovery talked about in the article above. It discusses the principle idea of what I call the Slip Wave Field.

I don’t understand why this finding is not being taken more seriously. Although I do not believe this damaged Einstein’s theories in any way (as his theory only applies to objects with an existential mass, and not waves), I think it is worth noting that these waves can be used to send information, even if they can’t contain information.

Take for example, fiber optics. The idea behind fiber optics is not that light can store information and then send it from one node to another, but rather that the light’s presence (or lack there of) can represent a number in binary.

Couldn’t the same idea be applied to radio waves, allowing us to send information faster than fiber optics allows us, and beyond that, we can send it through space, rather than only in network cables?

Comments are closed.

SaveNetRadio

How fast do radio waves travel.

We use radio waves from television and cellular service to navigation and air traffic control. Still, we don’t often stop appreciating them and just how crazy fast they really are. So, how fast do radio waves travel anyway?

Topics Covered - Index

How Fast Do Radio Waves Travel Through Space?

How long does it take for a radio signal to reach pluto, how long does it take for a radio message to travel from earth to the moon and back, how long does it take for radio waves to travel to the sun, how fast are radio waves compared to other types, can we detect radio waves from an alien civilization, so really, how fast do radio waves travel.

How Fast Does Radio Waves Travel on Earth or Moon or Sun

Unimpeded, radio waves travel at the speed of light because they are part of the electromagnetic spectrum. In terms of miles, radio waves travel at approximately 186,000 miles per second or 300,000,000 meters per second.

If you’re a science lover or just curious about the technology that makes your life easier, you’ve come to the right place. In the sections below, we will break down how fast radio waves travel, whether they’re in space or here on earth.

We’ll also answer interesting questions like how long it takes for radio waves to reach the moon or pluto. So let’s just dive right in!

There is a common misconception that radio waves travel slower through space than they do through the air. The truth is that radio waves travel at the speed of light, even in space. It might seem like it’s taking them longer because space is so vast that even light and radio waves take considerable time to make their way across it. 

There are galaxies we will never be able to see because they are so far away from us that the speed of light waves can’t keep up with the expansion of the universe. The same, of course, would be true of any radio waves coming from a civilization outside the observable universe. 

To get some perspective on how vast the distances are that radio waves travel through space , let’s see how long it takes for them to travel from our friendly rock Earth to the dwarf planet Pluto.

Radio waves take about four and a half hours to travel from Earth to Pluto. That’s because the waves must travel about three billion miles before reaching their destination. 

Now let’s look at an object that’s a little closer. Our moon . The question is, how long does it take for a radio message to travel from the earth to the moon and back? 

Radio waves can travel to the moon and back at an average of about 2.56 seconds. Therefore if you sent radio waves on a journey to the moon and back, it would be the blink of an eye before they return.  They can make it quickly because the distance from Earth to the moon is only about 238,855 miles. When compared to the 92.5 million miles between Earth and the Sun, that’s nothing. 

You may be wondering, what about the sun then? How long does it take for radio waves to travel from the earth to the sun?

Radio waves take eight minutes to make their way from the earth to the sun. 

That may seem like a short period, but remember, these waves are traveling at the speed of light. This just goes to show how unbelievably big our solar system is, let alone the whole universe. 

To really get an idea of just how incredibly fast radio waves to travel, you just need to compare them to other kinds of waves like sound waves and light waves. 

Below we’ve listed two other types of waves and their speed compared to radio waves:

  • Sound waves : Radio waves are a form of electromagnetic wave. Sound waves on the other hand, are a form of mechanical waves. Mechanical waves are not nearly as fast as electromagnetic waves because they are not made of light. Therefore sound waves can only travel 1,100 feet per second. That’s a far cry from the speed of light. 
  • Light waves : Like radio waves, light waves are also a form of electromagnetic wave. As such, light waves also travel at the speed of light. The main difference between light waves and radio waves is their frequency. 

The only thing that technically moves faster than the speed of radio waves or light isn’t a wave at all. The only thing faster than the speed of light is the expansion of the universe itself. That’s why radio waves outside the observable universe will never actually reach us.

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Let’s end on a fun note. Because radio waves can travel so far, so quickly, it’s only natural to wonder if we could detect radio waves sent out by an alien civilization living somewhere else in the universe.

While it is possible for us to detect radio waves from an alien civilization, the following issues make it less probable that we will:

  • The vastness of space: It’s hard to even wrap your head around just how ridiculously big the universe we live in is. Every indication we have now suggests that intelligent life is relatively rare, so knowing where to point our satellites is like a shot in the dark.
  • Radio waves diffuse: The real challenge is that as radio waves travel, they become diffused and unreadable. Therefore, if the advanced civilization is just a little too far away, it would be much harder to distinguish and interpret the radio waves they send. 

There have been scientific projects like SETI (Search for Extraterrestrial Intelligence) that have aimed satellites at the sky in the hopes of detecting a signal. Sadly, every single thing they’ve detected that seemed like it could be from aliens has turned out not to be so far. Still, the future isn’t written, so maybe someday that will be successful.

The only thing faster than traveling radio waves is the expansion of the universe. That’s because radio waves actually travel at the speed of light or 186,000 miles per second. 

This means that radio waves could travel to the sun in about eight minutes and to Pluto in about four and a half hours. Considering the vast distances between us and those objects, we can definitively say radio waves travel quickly. 

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Why does it take so long for the radio waves to travel through space?

Actually, radio waves travel very quickly through space. Radio waves are a kind of electromagnetic radiation, and thus they move at the speed of light. The speed of light is a little less than 300,000 km per second. At that speed, a beam of light could go around the Earth at the equator more then 7 times in a second.

The reason that it takes so long for radio messages to travel in space is that space is mind-bogglingly big. The distances to be traveled are so great that even light or radio waves take a while getting there. It takes around eight minutes for radio waves to travel from the Earth to the Sun, and four years to get from here to the nearest star.

How long does it take for transmissions to get between DS1 and Earth? How often is DS1 in communication with Earth? What are radio waves?
How is lag dealt with? Why does the data transfer rate have to drop with distance? What kind of data is DS1 sending back? How do the instruments and sensors coordinate sending signals? How much data is DS1 able to transfer? What is electromagnetic radiation?
How do you make a radio wave?

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Fast radio burst linked with gravitational waves for the first time

radio waves travel fastest in

We have  just published evidence  in  Nature Astronomy  for what might be producing mysterious bursts of radio waves coming from distant galaxies, known as  fast radio bursts  or FRBs.

Two colliding  neutron stars  — each the super-dense core of an exploded star — produced a burst of gravitational waves when they merged into a “ supramassive” neutron star . We found that two and a half hours later they produced an FRB when the neutron star collapsed into a black hole.

Or so we think. The key piece of evidence that would confirm or refute our theory — an optical or gamma-ray flash coming from the direction of the fast radio burst — vanished almost four years ago. In a few months, we might get another chance to find out if we are correct.

Brief and powerful

FRBs are incredibly powerful pulses of radio waves from space lasting about a thousandth of a second. Using data from a radio telescope in Australia, the Australian Square Kilometre Array Pathfinder ( ASKAP ),  astronomers have found  that most FRBs come from galaxies so distant, light takes  billions of years to reach us . But what produces these radio wave bursts has been puzzling astronomers since  an initial detection  in 2007.

The best clue comes from an object in our galaxy known as SGR 1935+2154. It’s a  magnetar , which is a neutron star with magnetic fields about a trillion times stronger than a fridge magnet. On April 28, 2020, it produced a  violent burst of radio waves  — similar to an FRB, although less powerful.

Astronomers have long predicted that two neutron stars — a binary — merging to produce a  black hole  should also produce a burst of radio waves. The two neutron stars will be highly magnetic, and black holes cannot have magnetic fields.  The idea  is the sudden vanishing of magnetic fields when the neutron stars merge and collapse to a black hole produces a fast radio burst. Changing magnetic fields produce electric fields — it’s how most power stations produce electricity. And the huge change in magnetic fields at the time of collapse could produce the intense electromagnetic fields of an FRB.

radio waves travel fastest in

The search for the smoking gun

To test this idea, Alexandra Moroianu, a masters student at the University of Western Australia, looked for merging neutron stars detected by the Laser Interferometer Gravitational-Wave Observatory ( LIGO ) in the U.S. The gravitational waves LIGO searches for are ripples in space-time, produced by the collisions of two massive objects, such as neutron stars.

LIGO has found two binary neutron star mergers. Crucially, the second, known as  GW190425 , occurred when a new FRB-hunting telescope called  CHIME  was also operational. However, being new, it took CHIME two years  to release its first batch of data . When it did so, Moroianu quickly identified a fast radio burst called  FRB 20190425A  which occurred only two and a half hours after GW190425.

Exciting as this was, there was a problem – only one of LIGO’s two detectors was working at the time, making it  very uncertain  where exactly GW190425 had come from. In fact, there was a 5 percent chance this could just be a coincidence.

Worse, the  Fermi  satellite, which could have detected gamma rays from the merger — the “smoking gun” confirming the origin of GW190425 — was  blocked by Earth  at the time.

radio waves travel fastest in

Unlikely to be a coincidence

However, the critical clue was that FRBs trace the total amount of gas they have passed through. We know this because high-frequency radio waves travel faster through the gas than low-frequency waves, so the time difference between them tells us the amount of gas.

Because we know the  average gas density of the universe , we can relate this gas content to distance, which is known as the  Macquart relation . And the distance travelled by FRB 20190425A was a near-perfect match for the distance to GW190425. Bingo!

So have we discovered the source of all FRBs? No. There are not enough merging neutron stars in the Universe to explain the number of FRBs — some must still come from magnetars, like SGR 1935+2154 did.

And even with all the evidence, there’s still a one in 200 chance this could all be a giant coincidence. However, LIGO and two other gravitational wave detectors,  Virgo , and  KAGRA , will  turn back on  in May this year, and be more sensitive than ever, while CHIME and  other radio telescopes  are ready to immediately detect any FRBs from neutron star mergers.

In a few months, we may find out if we’ve made a key breakthrough — or if it was just a flash in the pan.

Clancy W. James would like to acknowledge Alexandra Moroianu, the lead author of the study; his co-authors, Linqing Wen, Fiona Panther, Manoj Kovalem (University of Western Australia), Bing Zhang and Shunke Ai (University of Nevada); and his late mentor, Jean-Pierre Macquart, who experimentally verified the gas-distance relation, which is now named after him.

Clancy William James , Senior Lecturer (astronomy and astroparticle physics),  Curtin University

This article is republished from  The Conversation  under a Creative Commons license. Read the  original article .

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How Fast Do Radio Waves Travel in Space (Explained with FAQs)

radio waves travel fastest in

Writen by Edwin Jones

radio waves travel fastest in

Fact checked by Andrew Wright

how fast do radio waves travel in space

Radio waves play an essential role in most of the technological solutions around you. Unfortunately, very few people know about them; many people do not even know the meaning of radio waves. Therefore, there are a lot of misconceptions about radio waves and their velocity.

This article will provide everything you need to know about radio waves, including how fast do radio waves travel in space.

Table of Contents

What is the Speed of Radio Waves in Space?

What are radio waves, 1. low to medium frequencies, 2. higher frequencies, 3. shortwave radio, 4. highest frequencies, what are the properties of radio waves, 1. do radio waves continue in outer space, 2. does wi-fi take advantage of radio waves, 3. are radio waves the only type of electromagnetic wave, 4. what shape is a radio wave, 5. what are some practical applications of radio waves, 6. what electronics use radio waves, 7. are radio waves from a cell phone harmful.

Radio waves in space travel at the speed of light (c ≈299,79×10^6 m/s). That means the distance radio waves travel in 1 second in space is 299,792,458 meters (983,571,056 ft). So the speed of radio waves is much higher than that of sound waves .

Radio waves can travel through many different media at different speeds. When passing through a medium, the radio wave speed is decreased depending on the medium’s permittivity and permeability.

Radio waves have a wavelength of 0.04 inch to over sixty-two miles. As these waves go farther from the antenna that transmits them, their strength declines.

Contrary to what many people think, radio waves are not the sound you hear from your speakers or radio devices. What you hear are sound waves, not radio waves.

In essence, radio waves are electromagnetic radiation; therefore, they are pretty similar to a light wave . One difference between radio waves and light waves is that you cannot see radio waves.

Physicist James Clerk Maxwell foresaw the existence of radio waves; he created a famous Maxwell’s equation around the 1870s. Later, his prediction of radio waves was advanced by Heinrich Hertz, a German physicist. Heinrich Hertz was also the first to apply Maxwell’s equations to the transmission and reception of radio waves.

The unit of frequency for radio waves was named Hertz (Hz) in honor of Heinrich Hertz.

4 Main Types of Radio Waves

radio-wave-speed

Radio waves are divided into several different types; these include:

These frequencies are the first kind in the radio frequency spectrum; this frequency range covers extremely low to medium radio waves.

ELF stands for extremely low frequency while VLF stands for very low frequency; They operate with frequencies from under 3 to 30 kHz. These frequencies are considered the lowest type of radio frequencies. Moreover, their long-range capability made them suitable for communications equipment in submarines.

In particular, they can penetrate water and rocks. Hence, they have been widely applied in caves and mines.

These frequencies are HF, VHF, and UHF. They are widely used in broadcast audio, public service radio, cell phones, FM, and GPS. As a rule, low frequencies travel farther and propagate better than higher frequencies.

Shortwave radio makes use of frequencies that range from 1.7 MHz to 30 MHz. They are applied in the transmission of radio signals from shortwave stations around the world.

For example, stations like the VOA, BBC, and Voice of Russia use this frequency range for broadcast purposes.

On the other hand, shortwave is also widely used for long-distance broadcast.

These are SHF (Super high frequency) and EHF (extremely high frequency). SHF is widely used in wireless USB, Wi-Fi, and Bluetooth; it is also utilized for radar purposes. In particular, super high frequencies can only operate on straight lines; that means they bounce off any obstacle.

speed-of-radio-waves-in-space

Radio waves come with some very different properties; these include:

  • Their wavelength is longer than that of infrared light.
  • Can overcome materials or obstacles.
  • Can travel great distances.
  • They cannot be seen and cannot be felt.
  • Moving in a vacuum at the speed of light.
  • They can be formed by electric currents (including lightning).
  • Possess both electric and magnetic components.
  • They can be absorbed, refracted, reflected, as well as polarized.

Frequently Asked Questions

radio-waves-get-weaker-in-space

Radio waves can be used to send messages to space. NASA actually uses them for communication.

radio-waves-travel-in-space

Wi-Fi, like other wireless devices, applies radio frequencies to send signals between devices. However, the range of radio frequencies applied by Wifi is different from devices such as car radios, cell phones, weather radios, etc.

The short answer is no.

They are not the only components of the electromagnetic spectrum. There are several other forms of electromagnetic waves, including radar, BlueTooth, microwaves, infrared, ultraviolet light waves, and X-rays; all these components are electromagnetic waves.

Like other electromagnetic waves, radio waves look like ocean surface waves or any other type of wave. Wavelength is measured by the distance from the top of a peak to its neighboring peak.

Radio waves are used to transmit radio signals that your radio can pick up. In addition, they also work in carrying the signals you use for your smartphones and TVs.

There are devices that use radio waves for communication, such as two-way radios, television broadcasts, radio broadcasts, cellular telephones, cordless telephones, garage door openers, satellites, and countless other devices.

Some studies show that radio waves from cell phones can affect the metabolism of brain cells. However, there is no evidence that this effect is harmful.

Hopefully, after you finish reading this article, you will be confident enough to answer when someone asks you “how fast do radio waves travel in space” or “do radio waves travel at the speed of light?”

Thank you for reading. Please share this article if you find it helpful.

Amaro-Frank

Hi, I am Amaro Frank – the Wind Up Radio’s content editor and writer. Working with Adam is so much fun, as his stories and experiences enrich my knowledge about radio communications and radio accessories. My main tasks in Wind Up Radio are building content and generating great articles on different topics around radio accessories.

What Is the Speed of Radio Waves? The Surprising Answer!

Last Updated on Jan 23 2023

a cellphone, tablet and laptop on desk

Similar to light , radio waves are a type of electromagnetic radiation. They are used in communications and are most commonly seen in televisions and audio broadcasts but may also be used to send signals to and from spacecraft and space stations. Although many people think of them as a form of soundwave because they are converted by receivers to create audio, radio waves are actually electromagnetic, which means that they are similar to and travel at the same speed as light.

Radio waves travel at 300,000 kilometers per second. They can only achieve this speed in a vacuum but are only fractionally slower in Earth’s atmosphere.

  • What Is the Speed of Radio Waves?

Radio waves are electromagnetic radiation like sound waves, microwaves, and X-rays. All of these types of radiation travel at the same speed, which is 300,000 kilometers per second. This means that radio waves could travel around the earth seven times in a single second. It would take 8 minutes for them to travel from Earth to the Sun, and 4 years to reach the nearest star.

  • How Far Can a Radio Wave Travel?

Radio waves, and all forms of electromagnetic radiation, dissipate in Earth’s atmosphere, which means that they will eventually stop. However, in the void of space, they will travel on forever so they have no limit to the distance they will travel.

  • Are Radio Waves Harmful?

Radiofrequency radiation, which is the type of radiation caused by radio waves, is considered non-ionizing radiation, which means that it does not remove electrons from an atom and does not cause cancer. However, if the body absorbs enough radiofrequency radiation, it can cause parts of the body to heat up, which may cause burns and other related injuries.

It is also theorized that some forms of non-ionizing radiation may cause damage or changes to the body’s cells that lead to cancer, so while they don’t directly cause cancer, it is possible that some of this radiation may indirectly lead to cancerous changes of the body’s cells.

Radio waves are not considered harmful at the levels that most people are exposed to them, although research continues into the effects of non-ionizing radiation in general.

  • Does Rain Affect Radio Waves?

Radio waves are, or can be, affected by rain . The waves are reflected, refracted, and essentially diverted by the rain. This can lead to a phenomenon called rain fade, which means that the radio wave signal fades over distance, and it can have a significant impact on the use of radio waves for communication and other purposes.

  • Final Thoughts

Radio waves are used to transmit data, including pictures and audio, but while many people think of radio waves as a type of sound wave because radio plays sounds, radio waves are actually a type of electromagnetic radiation, which means that they are in the same class as light. They even travel at the same speed of light, which is slightly slower than 300,000 kilometers per second. Radio waves can travel to the Sun in 8 minutes but can be affected by rain. They are not thought to cause cancer in humans or animals.

  • https://www.nasa.gov/pdf/583093main_Earth_Calling.pdf
  • https://en.wikipedia.org/wiki/Radio_wave
  • https://www.qrg.northwestern.edu/projects/vss/docs/communications/2-why-does-it-take-so-long.html
  • https://www.ametsoc.org/index.cfm/ams/policy/policy-memos/the-radio-frequency-spectrum-and-weather-water-and-climate-uses-and-challenges/
  • https://physics.stackexchange.com/questions/461024/can-there-be-old-radio-waves-broadcasted-years-ago-still-traveling-in-the-air
  • https://www.cancer.org/healthy/cancer-causes/radiation-exposure/radiofrequency-radiation.html

Featured Image Credit: Mariakray, Pixabay

Table of Contents

About the Author Robert Sparks

Robert’s obsession with all things optical started early in life, when his optician father would bring home prototypes for Robert to play with. Nowadays, Robert is dedicated to helping others find the right optics for their needs. His hobbies include astronomy, astrophysics, and model building. Originally from Newark, NJ, he resides in Santa Fe, New Mexico, where the nighttime skies are filled with glittering stars.

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by Chris Woodford . Last updated: July 23, 2023.

Photo: Sound is energy we hear made by things that vibrate. Photo by William R. Goodwin courtesy of US Navy and Wikimedia Commons .

What is sound?

Photo: Sensing with sound: Light doesn't travel well through ocean water: over half the light falling on the sea surface is absorbed within the first meter of water; 100m down and only 1 percent of the surface light remains. That's largely why mighty creatures of the deep rely on sound for communication and navigation. Whales, famously, "talk" to one another across entire ocean basins, while dolphins use sound, like bats, for echolocation. Photo by Bill Thompson courtesy of US Fish and Wildlife Service .

Robert Boyle's classic experiment

Artwork: Robert Boyle's famous experiment with an alarm clock.

How sound travels

Artwork: Sound waves and ocean waves compared. Top: Sound waves are longitudinal waves: the air moves back and forth along the same line as the wave travels, making alternate patterns of compressions and rarefactions. Bottom: Ocean waves are transverse waves: the water moves back and forth at right angles to the line in which the wave travels.

The science of sound waves

Picture: Reflected sound is extremely useful for "seeing" underwater where light doesn't really travel—that's the basic idea behind sonar. Here's a side-scan sonar (reflected sound) image of a World War II boat wrecked on the seabed. Photo courtesy of U.S. National Oceanographic and Atmospheric Administration, US Navy, and Wikimedia Commons .

Whispering galleries and amphitheaters

Photos by Carol M. Highsmith: 1) The Capitol in Washington, DC has a whispering gallery inside its dome. Photo credit: The George F. Landegger Collection of District of Columbia Photographs in Carol M. Highsmith's America, Library of Congress , Prints and Photographs Division. 2) It's easy to hear people talking in the curved memorial amphitheater building at Arlington National Cemetery, Arlington, Virginia. Photo credit: Photographs in the Carol M. Highsmith Archive, Library of Congress , Prints and Photographs Division.

Measuring waves

Understanding amplitude and frequency, why instruments sound different, the speed of sound.

Photo: Breaking through the sound barrier creates a sonic boom. The mist you can see, which is called a condensation cloud, isn't necessarily caused by an aircraft flying supersonic: it can occur at lower speeds too. It happens because moist air condenses due to the shock waves created by the plane. You might expect the plane to compress the air as it slices through. But the shock waves it generates alternately expand and contract the air, producing both compressions and rarefactions. The rarefactions cause very low pressure and it's these that make moisture in the air condense, producing the cloud you see here. Photo by John Gay courtesy of US Navy and Wikimedia Commons .

Why does sound go faster in some things than in others?

Chart: Generally, sound travels faster in solids (right) than in liquids (middle) or gases (left)... but there are exceptions!

How to measure the speed of sound

Sound in practice, if you liked this article..., find out more, on this website.

  • Electric guitars
  • Speech synthesis
  • Synthesizers

On other sites

  • Explore Sound : A comprehensive educational site from the Acoustical Society of America, with activities for students of all ages.
  • Sound Waves : A great collection of interactive science lessons from the University of Salford, which explains what sound waves are and the different ways in which they behave.

Educational books for younger readers

  • Sound (Science in a Flash) by Georgia Amson-Bradshaw. Franklin Watts/Hachette, 2020. Simple facts, experiments, and quizzes fill this book; the visually exciting design will appeal to reluctant readers. Also for ages 7–9.
  • Sound by Angela Royston. Raintree, 2017. A basic introduction to sound and musical sounds, including simple activities. Ages 7–9.
  • Experimenting with Sound Science Projects by Robert Gardner. Enslow Publishers, 2013. A comprehensive 120-page introduction, running through the science of sound in some detail, with plenty of hands-on projects and activities (including welcome coverage of how to run controlled experiments using the scientific method). Ages 9–12.
  • Cool Science: Experiments with Sound and Hearing by Chris Woodford. Gareth Stevens Inc, 2010. One of my own books, this is a short introduction to sound through practical activities, for ages 9–12.
  • Adventures in Sound with Max Axiom, Super Scientist by Emily Sohn. Capstone, 2007. The original, graphic novel (comic book) format should appeal to reluctant readers. Ages 8–10.

Popular science

  • The Sound Book: The Science of the Sonic Wonders of the World by Trevor Cox. W. W. Norton, 2014. An entertaining tour through everyday sound science.

Academic books

  • Master Handbook of Acoustics by F. Alton Everest and Ken Pohlmann. McGraw-Hill Education, 2015. A comprehensive reference for undergraduates and sound-design professionals.
  • The Science of Sound by Thomas D. Rossing, Paul A. Wheeler, and F. Richard Moore. Pearson, 2013. One of the most popular general undergraduate texts.

Text copyright © Chris Woodford 2009, 2021. All rights reserved. Full copyright notice and terms of use .

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Can information travel faster than light?

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One of the tenets of Einstein's Theory of Special Relativity is that nothing can travel faster than the speed of light in a vacuum. Light speed is considered the universal speed limit of everything, and this is widely accepted by the scientific community. But in science, if you make a hard-and-fast rule, someone will try to disprove it, or at least find a loophole. And the speed of light is no exception.

Light, in a vacuum, travels at approximately 299,792 kilometers per second (186,282 miles per second). In September 2011, physicists working on the Oscillation Project with Emulsion-tRacking Apparatus (OPERA) created a frenzy in the scientific community when they announced that their experiments resulted in subatomic particles called neutrinos traveling from the European Organization for Nuclear Research (CERN) near Geneva, Switzerland to the Gran Sasso National Laboratory near L'Aquila, Italy and arriving around 60 nanoseconds earlier than a beam of light. Ideas as to either how these neutrinos could have actually broken the speed of light, or as to what errors could have caused the impossible results, abounded. Finally, equipment issues, including a loose cable, were discovered as likely culprits, and the results were declared erroneous. So no rewriting of Einstein's theories turned out to be necessary.

Other researchers are trying to bend the rules rather than break them. In fact, bending space-time is one theory of how superluminal – faster-than-light -- speeds in space travel might be reached. The idea is that space time could be contracted in front of a spaceship and expanded behind it, while the ship would remain stationary in a warp bubble that itself was moving faster than the speed of light. This concept was originally modeled by Mexican theoretical physicist Miguel Alcubierre in 1994 as a theoretical possibility, but one that would require a universe-sized amount of negative energy to power the phenomenon. It was later refined to requiring a planet-sized amount and then again to needing an amount around the size of the Voyager 1 space probe. Unfortunately, the negative energy would have to come from exotic matter that is difficult to come by, and we're currently only at the level of miniature lab experiments on warp drives. The math behind these theories is based on the laws of relativity, so theoretically it wouldn't be breaking the rules. The technology, if it ever exists, could also be used for going slower than light, but much faster than we can go now, which might be more practical.

Space travel is just one of the possible applications of reaching or exceeding the speed of light. Some scientists are working on doing the same for the purposes of much faster data transfer. Read on to find out about current data speeds and the potential for faster-than-light information.

Can data even travel at the speed of light?

The possibility of superluminal data transfer.

Currently, most of our data travels through either copper wire or fiber optic cable. Even when we send data via our cell phones over radio waves, which also travel at light speed, it ends up traversing the wired networks of the Internet at some point. The two most common types of copper wire for long-distance information transfer are twisted pair (used first for telephony, and later for dial-up Internet and DSL ), and coaxial cable (used for cable TV initially, then Internet and phone). Coaxial cable is the faster of the two. But still faster is fiber optic cable. Rather than using copper to conduct data in the form of electrical signals, fiber optic cable moves data as pulses of light.

The "in a vacuum" reference on the previous page regarding the speed of light is important. Light through fiber optic is not as fast as light through a vacuum. Light, when moving through just about any medium, is slower than the universal constant we know as the speed of light. The difference is negligible through air, but light can be slowed down considerably through other media, including glass, which makes up the core of most fiber optic cabling. The refractive index of a medium is the speed of light in a vacuum divided by the speed of light in the medium. So if you know two of those numbers, you can calculate the other. The index of refraction of glass is around 1.5. If you divide the speed of light (approximately 300,000 kilometers, or 186,411 miles, per second) by this, you get around 200,000 kilometers (124,274 miles) per second, which is the approximate speed of light through glass. Some fiber optic cabling is made of plastic, which has an even higher refractive index, and therefore a lower speed.

Part of the reason for the decrease in speed is the dual nature of light. It has the attributes of both a particle and a wave. Light is actually made up of particles called photons , and they do not move in a straight line through the cabling. As the photons hit molecules of material, they bounce in various directions. Light refraction and absorption by the medium eventually lead to some energy and data loss. This is why a signal can't travel indefinitely and has to be boosted periodically to cover long distances. However, the slowing of light isn't all bad news. Some impurities are added to fiber optics to control the speed and aid in channeling the signal effectively.

Fiber optic cable is still far faster than copper wire, and isn't as susceptible to electromagnetic interference. Fiber can achieve speeds of hundreds of Gigabits per second, or even Terabits. Home Internet connections don't achieve those super high speeds, at least partially because wiring is being shared by many households over entire areas, and even networks that use fiber optics generally have copper running the last stretch into people's homes. But with fiber running all the way to your neighborhood or home, you can get something in the range of 50 to 100 Megabits per second of data transfer, compared to 1 to 6 Megabits per second from average DSL lines and 25 or so Megabits per second from cable. Actual data speeds vary greatly by location, provider and your chosen plan, of course.

There are also other things that cause signal latency (delay), such as the back and forth communication required when you access a Web page or download data (handshaking). Your computer and the server housing the data are communicating to make sure they are synchronized and data transfer is successful, causing a delay, albeit a brief and necessary one. The distance your data has to travel will also affect how long it takes to get there, and there could be additional bottlenecks at any hardware and cabling the data has to travel through to get to its destination. A system is only as fast as its slowest component, and every millisecond counts in the days of seemingly (but not really) instant communication.

There have been recent breakthroughs in transferring data over copper wiring at nearly fiber optic speeds via reducing interference and other techniques. And researchers are also working on transmitting data via light through the air, say using lightbulbs for WiFi, or transmitting laser beams from building to building. Again, light through the air does move at close to light speed, but nothing we have now is surpassing the speed limit. Can we achieve actual faster-than-light transfer?

The use of fiber optic cable wasn't the first attempt to harness light for data transfer. Alexander Graham Bell himself invented the photophone, which was essentially the first wireless telephone, but using light rather than the radio waves used by modern cell phones. It worked by projecting a voice toward a mirror, which caused the mirror to vibrate. Light from the sun was bounced off the vibrating mirror into a selenium receiver that converted it into an electrical current for transmission via telephone (his most famous invention). Its major flaw was that direct sunlight was necessary, so clouds or other objects could block the signal. Never mind making a call in the middle of the night. But it actually worked, and served as a predecessor to fiber optics.

radio waves travel fastest in

Scientists at the National Institute of Standards and Technology (NIST) are claiming to have achieved faster-than-light transfer of quantum data using something called four-wave mixing, which incidentally is a phenomenon that's considered a form of interference in fiber optic lines. The experiment involves sending a short 200-nanosecond seed pulse through heated rubidium vapor and at the same time sending in a second pump beam at a different frequency to amplify the seed pulse. Photons from both beams interact with the vapor in a way that generates a third beam. Apparently, the peaks of both the amplified seed pulse and the newly generated pulse can exit faster than a reference beam traveling at the speed of light in a vacuum. The speed differences they reported were 50 to 90 nanoseconds faster than light through a vacuum. They even proclaimed being able to tune the speed of the pulses by altering the input seed detuning and power.

Another fast data transfer technology in the works is quantum teleportation , which relies on the existence of entangled pairs: two particles that are in tune with each other to the point that if you measure one, the other ends up with the same quality that you found in the first one, no matter their distance from one another. This also requires a third particle that contains the actual bits of data you are trying to transfer. A laser is used to teleport one of the entangled particles elsewhere, in a manner of speaking. It isn't really transporting a photon, but rather changing a new photon into a copy of the original. The photon in the entangled pair can be compared to the third photon to find their similarities or differences, and that information can be relayed to the other location and used for comparison with the twin particle to glean the data. This sounds like something that would result in instant transfer, but that's not the case. Laser beams only travel at the speed of light. But this has potential applications for sending encrypted data via satellite, and for networking quantum computers, should we ever invent them. And it's further along than any attempts at superluminal data transfer. It works over miles at this point, and researchers are trying to increase the teleportation distance.

The answer to whether meaningful information can travel faster than light is currently no. We're only at the level of moving a few quantum particles at speeds that may possibly be over the speed of light, if the data pans out on subsequent experiments. To have a practically applicable form of data transfer, you have to be able to send organized bits of data that mean something, uncorrupted, to another machine that can interpret it. The fastest transmission in the world will mean nothing otherwise. But you can be sure that if the speed of light is broken, we'll be applying it to our Internet transmissions far sooner than to interstellar travel. Our ability to watch the highest quality television and surf the net at the fastest speeds will be paramount. And perhaps for those purposes, even getting ourselves to truly as-fast-as-light transmission would do wonders.

Frequently Answered Questions

Is it possible for information to travel faster than light, lots more information, author's note.

Physics is a truly fascinating subject, as it attempts to find the answer to how everything in the universe works. Without the study of physics, we probably wouldn't have a lot of modern conveniences, for instance those that require electricity, or depend upon the behavior of waves of any sort (like just about every form of long distance communication). You certainly wouldn't be reading this right now. Without an understanding of physical laws, lifting a piano would be more difficult, video games wouldn't be as much fun (or exist), and cartoon animators wouldn't know what laws to break to make us laugh. And we certainly wouldn't have ventured into space, an ability we'll need if we discover, via astrophysics or a keen observer, that a planet-destroying asteroid is headed our way. Also, kudos to mathematics for making the study of physics possible. I will continue to sit back and reap the benefits made possible by all the hard-working mathematicians, physicists and engineers of the world.

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  • ABC Science. "Ask an Expert - Why is fibre optic technology 'faster' than copper?" (Nov. 24, 2012) http://www.abc.net.au/science/articles/2010/10/21/3044463.htm
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  • Boyle, Rebecca. "Fed Up With Sluggish Neutrinos, Scientists Force Light To Move Faster Than Its Own Speed Limit." PopSci. May 3, 2012. (Nov. 26, 2012) http://www.popsci.com/science/article/2012-05/fed-sluggish-neutrinos-scientists-force-light-move-faster-its-own-speed-limit
  • CBC News. "'Faster-than-light' data in doubt after new results." Mar. 19, 2012. (Nov. 15, 2012) http://www.cbc.ca/news/technology/story/2012/03/19/technology-faster-than-light-neutrinos-icarus.html
  • CBC News. "'Faster-than-light' particles may have been even speedier." Feb. 23, 2012. (Nov. 15, 2012) http://www.cbc.ca/news/story/2012/02/23/technology-faster-than-light-neutrinos-opera.html
  • Ceurstemont, Sandrine. "One-Minute Physics: Why light slows down in glass." New Scientist TV. Oct. 24, 2011. (Nov. 30, 2012) http://www.newscientist.com/blogs/nstv/2011/10/one-minute-physics-why-light-slows-down-in-glass.html
  • Collins, Nick. "Speed of light 'broken' at CERN, scientists claim." The Telegraph. Sept. 22, 2011. (Nov. 30, 2012) http://www.telegraph.co.uk/science/science-news/8783011/Speed-of-light-broken-at-CERN-scientists-claim.html
  • Condliffe, Jamie. "Did Scientists Really Just Break the Speed of Light?" Gizmodo. May 7, 2012. (Nov. 15, 2012) http://gizmodo.com/5908206/did-scientists-really-just-break-the-speed-of-light
  • Das, Saswato R. "Was Einstein Wrong?" New York Times. Sept. 29, 2011. (Dec. 2, 2012) http://www.nytimes.com/2011/09/30/opinion/30iht-eddas30.html
  • Diaz, Jesus. "Ridiculous: A Loose Cable Caused Those 'Faster-Than-Light' Particles." Gizmodo. Feb. 22, 2012. (Nov. 15, 2012) http://gizmodo.com/5887398/a-loose-cable-caused-the-faster+than+light-particles-test
  • Dillow, Clay. "Physicists Say Speed-of-Light Breaking Neutrinos Would've Lost Their Energy Along the Way." PopSci. Oct. 3, 2011. (Nov. 30, 2012) http://www.popsci.com/science/article/2011-10/physicists-say-speed-light-breaking-neutrinos-wouldve-lost-their-energy-along-way
  • Dodson, Brian. "Warp drive looks more promising than ever in recent NASA studies." Gizmag. Oct. 3, 2012. (Nov. 27, 2012) http://www.gizmag.com/warp-drive-bubble-nasa-interstellar/24392/
  • FCC. "Measuring Broadband America - July 2012." July 2012. (Dec. 2, 2012) http://www.fcc.gov/measuring-broadband-america/2012/july
  • Fettweis, Alfred. "Can signals truly be faster than light?" Signal Processing. August 2003, Volume 83, Issue 8, Pages 1583-1596. (Nov. 20, 2012)
  • Finnie, Matthew. "How clouds cheat the speed of light." The Guardian. Sept. 6, 2012. (Nov. 24, 2012) http://www.guardian.co.uk/media-network/media-network-blog/2012/sep/06/cloud-computing-speed-light-network
  • Glasser, Ryan T, Ulrich Vogl, and Paul D. Lett. "Stimulated generation of superluminal light pulses via four-wave mixing." Apr. 3, 2012. (Nov. 20, 2012) http://arxiv.org/pdf/1204.0810v1.pdf
  • Hartley, Darleen. "Data Faster Than the Speed of Light." BSN. June 27, 2012. (Nov. 30, 2012) http://www.brightsideofnews.com/news/2012/6/27/data-faster-than-the-speed-of-light.aspx
  • Higginbotham, Stacey. "Kotura: A startup betting on the speed of light in the data center." GigaOM. Nov. 23, 2012. (Nov. 25, 2012) http://gigaom.com/cloud/kotura-a-startup-betting-on-the-speed-of-light-in-the-data-center/
  • Hsu, Jeremy. "Spaceship Could Fly Faster Than Light." Space.com. Aug. 13, 2008. (Dec. 1, 2012) http://www.space.com/5725-spaceship-fly-faster-light.html
  • Iannone, P. "Optical Communications." IEEE Photonics Society. (Nov. 24, 2012) http://www.photonicssociety.org/content/optical-communications
  • Johnston, James H. "Internet With the Speed of Light." Legal Times. Volume XXV, Issue 45, Nov. 18, 2002. (Nov. 30, 2012) http://www.ieeeusa.org/communications/Massmedia/files/Internet%20With%20the%20Speed....pdf
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  • Lentine, A. "Optical Interconnects & Processing Systems." IEEE Photonics Society. (Nov. 24, 2012) http://www.photonicssociety.org/content/optical-interconnects-processing-systems
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  • Mims, Christopher. "Achieving Fiber Optic Speeds over Copper Lines." MIT Technology Review. Apr. 22, 2012. (Nov. 25, 2012) http://www.technologyreview.com/news/418646/achieving-fiber-optic-speeds-over-copper-lines/
  • Moskowitz, Clara. "Einstein's math may also describe faster-than-light velocities." Christian Science Monitor. Oct. 10, 2012. (Dec. 1, 2012) http://www.csmonitor.com/Science/2012/1010/Einstein-s-math-may-also-describe-faster-than-light-velocities
  • Page, Lewis. "US gov boffins achieve speeds FASTER THAN LIGHT - 'Loophole' found in Special Theory of Relativity." The Register. May 7, 2012. (November 15, 2012) http://www.theregister.co.uk/2012/05/07/faster_than_light_quantum/
  • Pennsylvania State University. "Researchers push transmission rate of copper cables." Nov. 14, 2007. (Nov. 24, 2012) http://live.psu.edu/story/27265
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  • Quigley, Brian. "Speed of Light in Fiber - The First Building Block of a Low-Latency Trading Infrastructure." Technically Speaking. Apr. 7, 2011. (Nov. 30, 2012) http://blog.advaoptical.com/speed-light-fiber-first-building-block-low-latency-trading-infrastructure/
  • Reich, Eugenie Samuel. "Neutrino experiment replicates faster-than-light finding." Nature. Nov. 18, 2011. (Nov. 15, 2012) http://www.nature.com/news/neutrino-experiment-replicates-faster-than-light-finding-1.9393
  • Schneider, David. "Financial Trading at the Speed of Light." IEEE Spectrum. Oct. 2011. (Nov. 25, 2012) http://spectrum.ieee.org/computing/it/financial-trading-at-the-speed-of-light
  • Wrenn, Eddie. "Can we finally break the speed of light? Nasa breakthrough suggested Star Trek's 'warp drives' may not only be possible - but practical." Daily Mail. Sept. 18, 2012. (Dec. 1, 2012) http://www.dailymail.co.uk/sciencetech/article-2204913/Nasa-breakthrough-suggests-Star-Treks-warp-drives-possible--practical.html
  • Wright, Robert. "Richard Feynman on the Weirdness of Physical Reality." Video of lecture at Cornell University: The Character of Physical Law: Probability and Uncertainty - The Quantum Mechanical View of Nature - November 18, 1964. The Atlantic. July 11, 2012. (Nov. 30, 2012) http://www.theatlantic.com/technology/archive/2012/07/richard-feynman-on-the-weirdness-of-physical-reality/259718/

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How Fast Radio Waves Travel

How Radio Waves Travel Faster

How Fast Radio Waves Travel, radio waves play a crucial function in the vast majority of technology solutions you see around you.   It is unfortunate that very few are aware of their significance; and many don’t even understand what radio waves mean.   So, there are many misconceptions regarding radio waves and their speed.

Radio waves play a major role in many of the technological solutions that we see around us.   For the majority of people, they do not even understand the meaning that radio waves have.

There’s a lot of confusion about radio waves.   From what they represent to how they work there are only a handful of people have any knowledge about this type of wave. When you’re finished reading this article you will be able to tell anyone else the radio waves and how they work.

What are Radio Waves?

Contrary to what many people think radio waves aren’t the sound you hear from the radio speakers.   These are sound waves and not radio waves. Radiation from radio waves is electromagnetic.   Radio waves are very like light waves.   The only distinction is that you are unable to detect these as light. Consider them to be generated by charged particles that go through acceleration, similar to electrical currents that are changing in time.

Transmitters create them artificially.   Radio receivers are required to receive and intercept radio waves by means by an antenna. Radio waves are a method of communication that can be found in numerous technologies. They are utilized in fixed and mobile radio communications, radar and navigation systems streaming, the radio wireless networks satellites for communication and many more.

Radio waves were first discovered in the 1870s by James Clerk Maxwell, the physicist the best well-known for his famous Maxwell’s Equation around the 1870s. A German scientist known in the form of Heinrich Hertz was the one who formulated Maxwell’s theory that radio waves would be a phenomenon.

What is the Speed of Radio Waves in Space?

Space radio waves are traveling at the rate of light (c 299,79×106 milliseconds).   This means the distance that radio waves can travel within one minute in space would be 299,792,458 m (983,571,056 feet).   Therefore, that radio wave speed is more powerful than sound waves.

Radio waves travel through a variety of different media with different speed.   While passing through a medium the speed of radio waves decreases depending on its permittivity, as well as its the permeability.

Radio waves span a distance of 0.04 inch up to more than sixty-two miles.   When these waves travel further away from the antenna that broadcasts them, their power decreases.

Main Types of Radio Waves

  • Low to Medium Frequencies The frequencies listed here are the very first in the spectrum of radio frequencies; the frequency spectrum covers low to medium-sized radio waves. ELF is an acronym in for Extremely Low Frequency, while VLF refers to extremely low frequency. They use frequencies that range from three to thirty kHz.   These frequencies are considered to be the most low-frequency radio frequencies.   Additionally, their range of operation makes them ideal for communication equipment used in submarines.
  • Higher Frequencies These frequencies include The frequencies are HF, VHF, and UHF.   They are used extensively in broadcast audio and public service radios and cell phones, FM, as well as GPS.   The general rule is that low frequencies are more powerful and spread more efficiently than higher frequencies.
  • Shortwave Radio Shortwave radio uses frequencies that vary between 1.7 Mhz and up to the 30th MHz.   They are utilized to transmit broadcast signals of shortwave radio stations across all over the world. For instance, stations such as VOA, BBC and Voice of Russia. VOA, BBC, and Voice of Russia use this frequency band for broadcasting purposes.
  • Highest Frequencies They comprise SHF (Super High Frequency) in addition to EHF (extremely very high frequency).   SHF is commonly utilized in wireless USB as well as Wi-Fi as well as Bluetooth and is employed for radar use.   Particularly, super high frequencies only work in straight lines, which means that they bounce off of any obstruction.

What are the Properties of Radio Waves

  • Radio waves possess  distinctive properties  which you must understand.   These properties will be described below.
  • They are a type of electromagnetic waves.   They possess an extended wavelength than that for infrared radiation.
  • When they pass through the vacuum and then through a medium, they move with the velocity of light.   However, their speed slows when they traverse the medium, according to its permeability.
  • Radio waves can form  by altering  electrical currents.   Naturally, they could be released by lightning or objects of the night that exhibit magnetic field fluctuations.

How Fast Do Radio Waves Travel?   Through Space, Air or Vacuum

The speed at which radio waves travel .

In the past, we have been successful in establishing the fact that electromagnetic waves exist.   They are therefore likely behave just like electromagnetic waves, too. One thing common with the electromagnetic wave is that all move at the speed of light in the vacuum.   They move at an approximate rate of around 186,000 miles per minute in an atmosphere.

Like audio waves, they are unable to traverse an air vacuum.   They are only able to transported through the medium. That is in other words, without a medium there is no way to hear.   Radio waves don’t necessarily require any media for their propagation.

Radio waves move in the exact same way as light waves because they’re similar to light waves, but they are not visible. The Radio waves can traverse different media at various speeds.   The speed at which they will be able to traverse a certain medium will depend on a few variables.

What is the Function of Radio Waves?

The best method to determine what radio waves do is to employ antennas to explain the idea. For the effectiveness of radio wave it’s require two antennas.   One antenna will be the transmitter, and the second will serve as the receiver. Let’s take the radio station as an illustration.   In the radio station, voices can be recorded by an audio microphone, and then the system converts it into electrical energy.

The electricity is then transmitted to an analogue (transmitter) at a high altitude.   The transmitter increases the strength of the electricity, allowing it to travel as far as is possible. The tiny particles of electric current constantly move between the antenna.

Radio waves then are able to travel with the speed light, or near that speed while the voices remain in them. So, when someone turns on their radio the electrons inside the antenna go between them (vibrated) due to coming radio waves. The resonating effect creates electricity.   The electronics component converts the electric signal into audio, which allows you to listen to the recorded voice at the station.

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Why do radio waves travel at the speed of light and not sound?

by How It Works Team · 06/07/2013

Radio waves are a form of electromagnetic radiation – the same phenomenon as light, X-rays and various other types of radiation, but with much longer wavelengths. As such, they travel at the speed of light (ie 300,000 kilometres/186,000 miles per second) – a lot faster than the 340 metres (1,125 feet) per second that sound itself moves through the air. It’s easy to be fooled by the fact that when you hear the word ‘radio’, you usually think of voices or music, but radio waves aren’t sounds themselves – just the medium used to broadcast an electronic signal from the studio to your hi-fi, which the speaker then turns back into the vibrations in the air which we hear.

Answered by Giles Sparrow.

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Chapter 6: Electromagnetics

Page One | Page Two | Page Three | Page Four | Page Five | Page Six

Chapter Objectives

Upon completion of this chapter you will be able to describe in general terms characteristics of natural and artificial emitters of radiation. You will be able to describe bands of the spectrum from RF to gamma rays, and the particular usefulness radio frequencies have for deep-space communication. You will be able to describe the basic principles of spectroscopy, Doppler effect, reflection and refraction.

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Electromagnetic Radiation

Electromagnetic radiation (radio waves, light, etc.) consists of interacting, self-sustaining electric and magnetic fields that propagate through empty space at 299,792 km per second (the speed of light , c ), and slightly slower through air and other media. Thermonuclear reactions in the cores of stars (including the Sun) provide the energy that eventually leaves stars, primarily in the form of electromagnetic radiation. These waves cover a wide spectrum of frequencies. Sunshine is a familiar example of electromagnetic radiation that is naturally emitted by the Sun. Starlight is the same thing from "Suns" much farther away.

When a direct current (DC) of electricity, for example from a flashlight battery, is applied to a wire or other conductor, the current flow builds an electromagnetic field around the wire, propagating a wave outward. When the current is removed the field collapses, again propagating a wave. If the current is applied and removed repeatedly over a period of time, or if the electrical current is made to alternate its polarity with a uniform period of time, a series of waves is propagated at a discrete frequency. This phenomenon is the basis of electromagnetic radiation.

Electromagnetic radiation normally propagates in straight lines at the speed of light and does not require a medium for transmission. It slows as it passes through a medium such as air, water, glass, etc.

The Inverse Square Law

Electromagnetic energy decreases as if it were dispersed over the area on an expanding sphere, expressed as 4pR 2 where radius R is the distance the energy has travelled. The amount of energy received at a point on that sphere diminishes as 1/R 2 . This relationship is known as the inverse-square law of (electromagnetic) propagation. It accounts for loss of signal strength over space, called space loss .

The inverse-square law is significant to the exploration of the universe, because it means that the concentration of electromagnetic radiation decreases very rapidly with increasing distance from the emitter. Whether the emitter is a distant spacecraft with a low-power transmitter or an extremely powerful star, it will deliver only a small amount of electromagnetic energy to a detector on Earth because of the very great distances and the small area that Earth subtends on the huge imaginary sphere.

An illustration of the inverse square law.

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Astronomers Find Powerful ‘Fast Radio Burst’ That Traveled for Eight Billion Years

The strong blast of radio waves is the oldest known, and it could tell scientists more about the mysterious matter that lies between galaxies

Will Sullivan

Will Sullivan

Daily Correspondent

Four large telescopes below an evening sky

Astronomers have detected an extremely brief flash of radio waves called a fast radio burst (FRB) that originated in deep space eight billion years ago.

This pulse of energy, which was more than three times stronger than what scientists thought was possible, is also the oldest FRB ever observed, researchers reported in October in the journal Science .

“We didn’t know whether fast radio bursts even existed that far back in time,” Stuart Ryder , co-lead author of the study and an astronomer at Macquarie University in Australia, tells Nature News ’ Gemma Conroy.

FRBs last only for milliseconds. But despite its brief duration, the newly detected FRB contained as much energy as the sun emits in 30 years, per Reuters ’ Will Dunham. These powerful, short-lived events could provide insight into how much matter lies between galaxies, according to a statement from Macquarie University.

“It’s very exciting, definitely one of the great applications of fast radio bursts,” Ziggy Pleunis , an astronomer at the University of Toronto who did not contribute to the findings, says to Popular Science ’s Rahul Rao. “Fast radio bursts currently are really the only thing that we know that interacts with the intergalactic medium in a meaningful enough way that we can measure properties.”

Since the first FRB was detected in 2007, astronomers have spotted around 800 more, data scientist Kshitij Aggarwal wrote in the Conversation last year. But researchers still aren’t sure about what causes these phenomena.

Ryan Shannon , a co-author of the study and an astronomer at Swinburne University in Australia, tells Reuters that the most likely source is a type of neutron star with a powerful magnetic field called a magnetar . Neutron stars are the ultra-dense remains of supermassive stars that have exploded.

“[Magnetars] are some of the most extreme objects in the universe, which you would need to produce such extreme bursts,” Shannon tells Reuters.

For the new detection, the researchers turned to the Australian Square Kilometer Array Pathfinder (ASKAP), a radio telescope made up of three dozen dishes on Wajarri Yamaji Country in Western Australia. ASKAP determined where the burst had come from, then the team used the Very Large Telescope in Chile to pinpoint the source galaxy.

“The further you go out in the universe, of course, the fainter the galaxies are, because they’re farther away. It’s quite difficult to identify the host galaxy, and that’s what they’ve done,” Sarah Burke-Spolaor , an astronomer at West Virginia University who was not involved in the study, tells Popular Science .

That galaxy, though fuzzy in their images, appeared to have two or three bright blobs within it, suggesting the FRB originated when a group of galaxies collided in the early universe. The eight-billion-year-old burst is more than half the universe’s age, which is about 13.7 billion years.

The researchers hope to use FRBs to find out how much of the hot and diffuse gas called plasma lies between galaxies. These intergalactic particles cause FRBs to disperse as they pass through, which astronomers can measure. This can enable scientists to calculate how much plasma lies between Earth and the site where the FRB began.

“As the sample of these distant bursts grows, they will tell us a lot about how the universe evolved,” Kiyoshi Masui , an astrophysicist at MIT who did not contribute to the findings, tells Nature News .

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Will Sullivan

Will Sullivan | | READ MORE

Will Sullivan is a science writer based in Washington, D.C. His work has appeared in Inside Science and NOVA Next .

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COMMENTS

  1. 5.1.1: Speeds of Different Types of Waves

    5.1.1: Speeds of Different Types of Waves. The speed of a wave is fixed by the type of wave and the physical properties of the medium in which it travels. An exception is electromagnetic waves which can travel through a vacuum. For most substances the material will vibrate obeying a Hooke's law force as a wave passes through it and the speed ...

  2. Radio wave

    Air is thin enough that in the Earth's atmosphere radio waves travel very close to the speed of light. The wavelength is the distance from one peak (crest) of the wave's electric field to the next, and is inversely proportional to the frequency of the wave. The relation of frequency and wavelength in a radio wave traveling in vacuum or air is.

  3. Device Makes Radio Waves Travel Faster Than Light

    Singleton said the polarization synchrotron basically abuses radio waves so severely that they finally give in and travel faster than light. This may be what happens in pulsars, as well ...

  4. How Fast Do Radio Waves Travel?

    Unimpeded, radio waves travel at the speed of light because they are part of the electromagnetic spectrum. In terms of miles, radio waves travel at approximately 186,000 miles per second or 300,000,000 meters per second. If you're a science lover or just curious about the technology that makes your life easier, you've come to the right place.

  5. Why does it take so long for the radio waves to travel through space?

    Actually, radio waves travel very quickly through space. Radio waves are a kind of electromagnetic radiation, and thus they move at the speed of light. The speed of light is a little less than 300,000 km per second. At that speed, a beam of light could go around the Earth at the equator more then 7 times in a second. The reason that it takes so ...

  6. Radio Waves

    Radio waves have the longest wavelengths in the electromagnetic spectrum. They range from the length of a football to larger than our planet. Heinrich Hertz proved the existence of radio waves in the late 1880s. He used a spark gap attached to an induction coil and a separate spark gap on a receiving antenna. When waves created by the sparks of ...

  7. Relative speed of sound in solids, liquids, and gases

    The stiffer the medium the faster the sound waves will travel through it. This is because in a stiff material, each molecule is more interconnected to the other molecules around it. So any disturbance gets transmitted faster down the line. The other factor that determines the speed of a sound wave is the density of the medium.

  8. Fast radio burst linked with gravitational waves for the first time

    But what produces these radio wave bursts has been puzzling astronomers since an initial detection in 2007. The best clue comes from an object in our galaxy known as SGR 1935+2154.

  9. Is the speed of gamma rays equal to the speed of radio waves?

    Does a radio wave or gamma radiation have a faster speed? I know that all light travels at $\pu{3E8 m s-1}$, but does that include these forms of electromagnetic radiation? Or do radio waves travel at $700~\mathrm{nm}$ and gamma rays $400~\mathrm{nm}$?

  10. Radio wave

    radio wave, wave from the portion of the electromagnetic spectrum at lower frequencies than microwaves. The wavelengths of radio waves range from thousands of metres to 30 cm. These correspond to frequencies as low as 3 Hz and as high as 1 gigahertz (10 9 Hz). Radio-wave communications signals travel through the air in a straight line, reflect ...

  11. Understanding Radio Waves: Nature and Properties

    Understanding Radio Waves: Nature and Properties. Radio waves, the unsung heroes of the electromagnetic spectrum, serve as the cornerstone of amateur radio, enabling enthusiasts to experiment, communicate, and explore a world invisible to the naked eye. These waves, oscillating electric and magnetic fields that travel through space at the speed ...

  12. How Fast Do Radio Waves Travel in Space (Explained with FAQs)

    Radio waves in space travel at the speed of light (c ≈299,79×10^6 m/s). That means the distance radio waves travel in 1 second in space is 299,792,458 meters (983,571,056 ft). So the speed of radio waves is much higher than that of sound waves. Radio waves can travel through many different media at different speeds.

  13. What Is the Speed of Radio Waves? The Surprising Answer!

    Radio waves are electromagnetic radiation like sound waves, microwaves, and X-rays. All of these types of radiation travel at the same speed, which is 300,000 kilometers per second. This means that radio waves could travel around the earth seven times in a single second. It would take 8 minutes for them to travel from Earth to the Sun, and 4 ...

  14. How fast do radio waves travel?

    Radio waves are able to travel as fast as light in space. Even though it may seem that it takes longer, it is because the space is so vast. It can take a long time for radio waves and light to ...

  15. Sound

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  16. Can information travel faster than light?

    Even when we send data via our cell phones over radio waves, which also travel at light speed, it ends up traversing the wired networks of the Internet at some point. The two most common types of copper wire for long-distance information transfer are twisted pair (used first for telephony, and later for dial-up Internet and DSL ), and coaxial ...

  17. Understanding The Physics Behind How Fast Radio Waves Travel

    Space radio waves are traveling at the rate of light (c 299,79×106 milliseconds). This means the distance that radio waves can travel within one minute in space would be 299,792,458 m (983,571,056 feet). Therefore, that radio wave speed is more powerful than sound waves. Radio waves travel through a variety of different media with different speed.

  18. Why do radio waves travel at the speed of light and not sound?

    Radio waves are a form of electromagnetic radiation - the same phenomenon as light, X-rays and various other types of radiation, but with much longer wavelengths. As such, they travel at the speed of light (ie 300,000 kilometres/186,000 miles per second) - a lot faster than the 340 metres (1,125 feet) per second that sound itself moves ...

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  20. How far can radio waves travel in vacuum? and light waves?

    1. Radio wave and light wave are the same thing. They all are electromagnetic radiation, the only difference between them is frequency. My question : 1, is there any photon-like thing for radio wave? 2, how far can they travel in vacuum space? Thanks. visible-light. waves. photons. space.

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    Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere. [1] : 26‑1 As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and ...

  22. Astronomers Find Powerful 'Fast Radio Burst' That Traveled for Eight

    Sven Creutzmann / Getty Images. Astronomers have detected an extremely brief flash of radio waves called a fast radio burst (FRB) that originated in deep space eight billion years ago. This pulse ...

  23. Physics

    A) travel at the same speed as sound waves. B) always travel much faster than sound waves. C) travel slower, on average, than sound waves. B. If a light signal and a radio signal were emitted simultaneously from Alpha Centauri, the first to reach Earth would be the. A) radio signal. B) light signal.