# Why does light travel at 299,792,458 meters per second

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You cant equate sound waves to the quantum world, sound waves are just that waves, in the macro- world In the micro- world, light just like other fundamental particles, can exist both as a wave and as a particle. Google the "Double Spit Experiment"

Yes "space is a thing", or something, it is a 3 dimensional reality, which contains the stuff of our universe.

Wouldn't space be like darkness, the absence of matter?

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What are you expecting me to say: yes or no?

Amusingly, there are 2 ways to read your sentence.

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I said I hope that someone will explain why the speed of light is constant as measured by any inertial observer before I die.

In the meanwhile I have made my own idea on this. I prefer being wrong than to have no answer at all.

Your last statement makes little sense, we don't know why the fundamental constants are set as the mathematical reality they are, but luckily they are what they are and they allow the conditions of the universe to support life, on planet earth at least.

Your question is like asking why pi is not exactly 3 instead of 3.14159 to infinitity

Wikipedia

The number π is a mathematical constant that is the ratio of a circle's circumference to its diameter and is approximately equal to 3.14159. It has been represented by the Greek letter "π" since the mid-18th century "pi" ().

Edited by Alan McDougall
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Since it makes Michel123456 feel better

"It is universal.

No material thing in the Universe travels faster than C."

Happy now?

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Wouldn't space be like darkness, the absence of matter?

Of course it would, mass=energy EMC2 , light is energy/electromagnetic spectrum , which the absence of would = absolute darkness. Quantum physics will not allow this to happen , what we suppose is empty space really seethes with energy. And also you are referring to the visual spectrum of electromagnetism in which our human eyes are designed by evolution to observe our reality.

Just a thought! darkness is relative, a snake perceives objects in infrared , our eyes do not react in that particular part of electromagnetism.

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Of course it would, mass=energy EMC2 , light is energy/electromagnetic spectrum , which the absence of would = absolute darkness. Quantum physics will not allow this to happen , what we suppose is empty space really seethes with energy. And also you are referring to the visual spectrum of electromagnetism in which our human eyes are designed by evolution to observe our reality.

Just a thought! darkness is relative, a snake perceives objects in infrared , our eyes do not react in that particular part of electromagnetism.

I was just giving a basic example. Here, would this one make you happy Cold is the absence of heat.

And coldness isn't relative...

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I was just giving a basic example. Here, would this one make you happy Cold is the absence of heat.

And coldness isn't relative...

Cold is relative the Inuit (Eskimo) people perceive cold differently from an African who has lived all his life in the blazing heat of the Sahara Desert. Technically you are right, cold is the absence of heat, heat is just the vibration of molecules in the substance.

Since it makes Michel123456 feel better

"It is universal.

No material thing in the Universe travels faster than C."

Happy now?

No material thing in the universe travels, "Through" space faster than C

Galaxies, which are embedded in space(Much like raisins embedded the dough of bread loaf), can travel faster than light, relative to other galaxies from which they are receding, due to the expansion of the universe. Galaxies mostly "move with space as the expansion of the universe" continues, with exceptions of the like the Andromeda Galaxy, our nearest neighbor, which are being drawn together by their mutual gravity fields, but later,once combined into a colossal new galaxy, it will join the rest of the universe in its increasing expansion to its ultimate doom of the heat death.

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(...) Galaxies mostly "move with space as the expansion of the universe" continues, with exceptions of the like the Andromeda Galaxy, our nearest neighbor, which are being drawn together by their mutual gravity fields, but later,once combined into a colossal new galaxy, it will join the rest of the universe in its increasing expansion to its ultimate doom of the heat death.

Isn't that a bit problematic that "the fabric of space" which is an "immaterial thing" is able to "move galaxies"?

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Isn't that a bit problematic that "the fabric of space" which is an "immaterial thing" is able to "move galaxies"?

It isn't like a force "pushing" the galaxies through space. It is just that the "metric" (crudely, the measurement of distance between things) increases over time. So, over time, things get further apart (without themselves moving).

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Isn't that a bit problematic that "the fabric of space" which is an "immaterial thing" is able to "move galaxies"?

No. The problem is hanging on to classical notions of motion which are being applied to a more nuanced situation.

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Of course it would, mass=energy EMC2 , light is energy/electromagnetic spectrum , which the absence of would = absolute darkness. Quantum physics will not allow this to happen , what we suppose is empty space really seethes with energy. And also you are referring to the visual spectrum of electromagnetism in which our human eyes are designed by evolution to observe our reality.

Just a thought! darkness is relative, a snake perceives objects in infrared , our eyes do not react in that particular part of electromagnetism.

Are you saying that energy and matter is like space and time? What I mean by that the more energy there is, the less matter there is, and were there is matter, there is no energy?

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It isn't like a force "pushing" the galaxies through space. It is just that the "metric" (crudely, the measurement of distance between things) increases over time. So, over time, things get further apart (without themselves moving).

The best analogy in my opinion is that galaxies are to think of galaxies as being embedded in space and thus, they expand at the expansion rate of the universe. A spaceship on the other hand would have to travel 'through space to get to another nearby galaxy because it is not embedded in space. However if the if the spaceship needed to travel between the stars of its home galaxy, it would also have to travel through space to get there. "Nothing can exceed the speed of light "Through Space"

But the spaceship which is part of its home galaxy , and its home galaxy is embedded in space, would also be subject to the overall expansion of the universe and would move outwards with space because it home galaxy is embedded in space, at the rate of expansion of the universe. Thus said spaceship could be said to be both "traveling "through Space" and traveling with space!

Something can exceed the speed of light if it is embedded in space.

Isn't that a bit problematic that "the fabric of space" which is an "immaterial thing" is able to "move galaxies"?

RAISINS = GALAXIES

DOUGH = SPACE

Space is not really an immaterial thing, it is more like the analogy of dough in a raisin cake, the dough, loosely equate to space and the raisins to galaxies. When the rising of the dough of the raisin cake could be analogous to the expansion of the universe. The raisins don't move, they just separate, further and further apart as the dough rises. The raisins separate of a greater rate, if more heat is supplied,maybe we could equate the heat, to the mysterious dark energy that is causing the universe to expand.

There are no perfect analogies , but that is my effort to try and explain the topic.

Edited by Alan McDougall
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Are you saying that energy and matter is like space and time? What I mean by that the more energy there is, the less matter there is, and were there is matter, there is no energy?

Not exactly what I was referring to is "Vacuum Energy' or what is called zero-point energy that exists in a vacuum. It is rather complex, I just put two chapters about it below, but if you want to know more about read the whole article.

http://en.wikipedia.org/wiki/Vacuum_state

Energy

Main article: Vacuum energy

The vacuum state is associated with a zero-point energy, and this zero-point energy has measurable effects. In the laboratory, it may be detected as the Casimir effect. In physical cosmology, the energy of the cosmological vacuum appears as the cosmological constant. In fact, the energy of a cubic centimeter of empty space has been calculated figuratively to be one trillionth of an erg.[8] An outstanding requirement imposed on a potential Theory of Everything is that the energy of the quantum vacuum state must explain the physically observed cosmological constant.

Electrical permittivity

In principle, quantum corrections to Maxwell's equations can cause the experimental electrical permittivity ε of the vacuum state to deviate from the defined scalar value ε0 of the electric constant.[10] These theoretical developments are described, for example, in Dittrich and Gies.[5] In particular, the theory of quantum electrodynamics predicts that the QED vacuum should exhibit nonlinear effects that will make it behave like a birefringent material with ε slightly greater than ε0 for extremely strong electric fields.[11][12] Explanations for dichroism from particle physics, outside quantum electrodynamics, also have been proposed.[13] Active attempts to measure such effects have been unsuccessful so far.[14According to Astrid Lambrecht (2002): "When one empties out a space of all matter and lowers the temperature to absolute zero, one produces in a Gedankenexperiment the quantum vacuum state."[1]

According to Fowler & Guggenheim (1939/1965), the third law of thermodynamics may be precisely enunciated as follows:

It is impossible by any procedure, no matter how idealized, to reduce any assembly to the absolute zero in a finite number of operations.[24] (See also.[25][26][27])

Photon-photon interaction can occur only through interaction with the vacuum state of some other field, for example through the Dirac electron-positron vacuum field; this is associated with the concept of vacuum polarization.[28]

According to Milonni (1994): "... all quantum fields have zero-point energies and vacuum fluctuations."[29] This means that there is a component of the quantum vacuum respectively for each component field (considered in the conceptual absence of the other fields), such as the electromagnetic field, the Dirac electron-positron field, and so on.

According to Milonni (1994), some of the effects attributed to the vacuum electromagnetic field can have several physical interpretations, some more conventional than others. The Casimir attraction between uncharged conductive plates is often proposed as an example of an effect of the vacuum electromagnetic field. Schwinger, DeRaad, and Milton (1978) are cited by Milonni (1994) as validly, though unconventionally, explaining the Casimir effect with a model in which "the vacuum is regarded as truly a state with all physical properties equal to zero."[30][31]

In this model, the observed phenomena are explained as the effects of the electron motions on the electromagnetic field, called the source field effect. Milonni writes: "The basic idea here will be that the Casimir force may be derived from the source fields alone even in completely conventional QED, ..." Milonni provides detailed argument that the measurable physical effects usually attributed to the vacuum electromagnetic field cannot be explained by that field alone, but require in addition a contribution from the self-energy of the electrons, or their radiation reaction. He writes: "The radiation reaction and the vacuum fields are two aspects of the same thing when it comes to physical interpretations of various QED processes including the Lamb shift, van der Waals forces, and Casimir effects."[32] This point of view is also stated by Jaffe (2005): "The Casimir force can be calculated without reference to vacuum fluctuations, and like all other observable effects in QED, it vanishes as the fine structure constant, α, goes to zero."[33]

Edited by Alan McDougall
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Just note I couldn't find this on Google.

So why?

Why not slower, or faster?

This is a confusing question that I hope someone could answer.

And another question along these lines,

if a photon has no mass, how does it "fall" into a black hole.

Gravity is the force of attraction between two objects, right?

which one should i answer first?

see it has its own particular velocity as sound and cars(speed limit only)

proton have mass of 1.003 amu

and gravity is the force of attraction of any rotating object(with huge mass usually) on nearby object

hope i made some sense this time

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What are you expecting me to say: yes or no?

Amusingly, there are 2 ways to read your sentence.

-----------------------------------------------------

I said I hope that someone will explain why the speed of light is constant as measured by any inertial observer before I die.

In the meanwhile I have made my own idea on this. I prefer being wrong than to have no answer at all.

The light speed limit C has something to do with the concept of diminishing returns. Lets take the analogy of a world class athlete like Usain Bolt, it is easy for him to run the hundred meters at say 10 second, but harder to run it at 9.8 much harder to run it at 9.6 and he needs much more energy to run just a little faster than that. The closer he comes to his physical limit the more and more energy he needs To achieve his world record time of 9.58 for the 100 meters, he had to accumulate the maximum energy output condensed in the final strides of the race to better his time, imperceptibly from 9.6 to 9.59. That is one example of diminishing returns (You mostly read about diminishing returns in economics, but it also applies to the performance of world class athletes)

In a way an object that approaches the speed of light has the same dilemma. The closer it gets to C the more and more energy it needs to go faster and its mass increases. Near the speed of light say at 99.01 C it by now needs an unimaginable amount of energy to go a tiny bit faster and is also becoming increasingly massive. Theoretically to actually reach the speed of light, the object will need all the energy in the universe to achieve it and by that moment would have become as massive than the entire universe. There is some speculation if this impossibility were to actually happen the universe would become one colossal fundamental particle of infinite mass. This is an example of the ultimate case of diminishing returns.

Another example is the Large Hadron Collider it needs over 20 megawatts of power to push protons to 0.99991 C . but to achieve C with the same protons my above paragraph would apply!

I hope this helps somewhat! Alan

An

Edited by Alan McDougall
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I must open a thread some day on the geometric effects of scaling.

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and gravity is the force of attraction of any rotating object(with huge mass usually) on nearby object

The source of gravity is not rotation

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I must open a thread some day on the geometric effects of scaling.

Why?

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• 2 weeks later...

Light travels at a constant speed (in a vacuum) relative to it's source because that's the speed at which a photon is ejected. For the same reason that objects close to earth all fall at approximately the same speed.

The idea of light moving at a constant speed relative to the observer rather than the source is one of those rumors that has been widely accepted with no legitimate proof. Yes, the speed of light coming from a moving object was measured at the predicted speed. This was done with an array of mirrors... Since light was absorbed and re-emitted by the first mirror it hit, they did nothing beyond proving the consistancy of the speed of light between those stationary mirrors.

Anyone wishing to dispute this is welcome to provide an example upon which they base their understanding... Where the light measured is not absorbed and re-emitted by a stationary object.

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Light travels at a constant speed (in a vacuum) relative to it's source because that's the speed at which a photon is ejected. For the same reason that objects close to earth all fall at approximately the same speed.

The idea of light moving at a constant speed relative to the observer rather than the source is one of those rumors that has been widely accepted with no legitimate proof. Yes, the speed of light coming from a moving object was measured at the predicted speed. This was done with an array of mirrors... Since light was absorbed and re-emitted by the first mirror it hit, they did nothing beyond proving the consistancy of the speed of light between those stationary mirrors.

Anyone wishing to dispute this is welcome to provide an example upon which they base their understanding... Where the light measured is not absorbed and re-emitted by a stationary object.

In a word, no.

This represents a very narrow view of physics: that one can only know something if it is directly observed. The principle of relativity has ramifications, and if those ramifications are found to be true, then that's evidence that the principle is correct. My radio works in my car when it's moving. That's evidence, because Maxwell's equations would not give a wave solution unless c was invariant.

So it is not true that there is no legitimate proof.

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Swan, the motion of a car is essentially irrelevant. The difference between frequency of a radio wave traveling at the speed of light vs. the speed of light +/- 60 MPH is pretty negligible. Does your car radio only work if there is a pure vacuum between the source of the signal and your car? How much does the speed of light vary due to the change in mediums between the tower and your car parked in your garage right now?

Let me know when you can find a single source of the speed of light being reliably measured without re-emitting it from a stationary object before the measurement's taken.

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Light travels at a constant speed (in a vacuum) relative to it's source because that's the speed at which a photon is ejected. For the same reason that objects close to earth all fall at approximately the same speed.

The idea of light moving at a constant speed relative to the observer rather than the source is one of those rumors that has been widely accepted with no legitimate proof. Yes, the speed of light coming from a moving object was measured at the predicted speed. This was done with an array of mirrors... Since light was absorbed and re-emitted by the first mirror it hit, they did nothing beyond proving the consistancy of the speed of light between those stationary mirrors.

Anyone wishing to dispute this is welcome to provide an example upon which they base their understanding... Where the light measured is not absorbed and re-emitted by a stationary object.

Are photons ejected?

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Are photons ejected?

They are emitted. But everybody understood what he had in mind.

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Swan, the motion of a car is essentially irrelevant. The difference between frequency of a radio wave traveling at the speed of light vs. the speed of light +/- 60 MPH is pretty negligible. Does your car radio only work if there is a pure vacuum between the source of the signal and your car? How much does the speed of light vary due to the change in mediums between the tower and your car parked in your garage right now?

Let me know when you can find a single source of the speed of light being reliably measured without re-emitting it from a stationary object before the measurement's taken.

Again, you are limiting the situation to a measurement, rather than some other test of the principle. You don't get to artificially restrict the evidence like that.

If you don't like the car example, it works just as well with a space probe moving much faster. The problem isn't the Doppler shift, though. The problem is that the wave equation fails if the speed of propagation isn't invariant.

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They are emitted. But everybody understood what he had in mind.

.

I am sure they knew what he meant, but for those who might not, can I add a comment below?

Photons and other "mass-less" particles have Zero rest mass.

When a Photon is created it is already moving. It isn't like a ball that in laying on the ground and gets kicked. At the point of conversion the photon is instantly traveling at the speed of light namely C

SR dictates that only things with mass require more energy to be accelerated. Since photons have "no mass" and actually never "accelerate" the restriction doesn't apply to them.

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.

I am sure they knew what he meant, but for those who might not, can I add a comment below?

Photons and other "mass-less" particles have Zero rest mass.

When a Photon is created it is already moving. It isn't like a ball that in laying on the ground and gets kicked. At the point of conversion the photon is instantly traveling at the speed of light namely C

SR dictates that only things with mass require more energy to be accelerated. Since photons have "no mass" and actually never "accelerate" the restriction doesn't apply to them.

This is moot. Such acceleration wasn't part of the discussion

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