Why must the speed light be constant?

Discussion in 'Physics & Math' started by Saint, May 30, 2021.

  1. Saint Valued Senior Member

    Why must the speed light be constant?
    Did Einstein explain?
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  3. Write4U Valued Senior Member

    Speed gives photons mass and at "c" this mass becomes infinite and the inherent dynamical energy is unable to drive it any faster than "c".
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  5. Q-reeus Banned Valued Senior Member

    Wrong. That speed limit via infinite energy input only applies to massive particles i.e. having non-zero rest mass e.g. electron. Photons have perfectly finite energy-momentum when always traveling at c in vacuo. Photon energy is determined by frequency according to E = hν and is a frame-dependent quantity.
    exchemist likes this.
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  7. Write4U Valued Senior Member

    No, read the question. It asks why the speed of light is always constant. Photons cannot travel faster than "c". That why their speed is constant.
    Yes, but light cannot travel at faster than "c", because a photon acquires virtual mass and at "c", and that mass exceeds its dynamic energy. But because they have zero rest-mass, they must always travel @ "c" and require no acceleration. That is the constancy of light .

    Massive particles require acceleration and can never even travel @ "c", because of the amount of energy required is too great. Their speed limit is always below "c".

    BBC - The real reasons nothing can ever go faster than light
    We are told that nothing can travel faster than light. This is how we know it is true
    p.s. question ; Does "in vacuo" mean , absence of quantum fields like the Higgs field which imparts mass on moving quanta?
    Last edited: May 30, 2021
  8. Q-reeus Banned Valued Senior Member

    Here is part of what you originally posted and my reply to it:
    So you had quick second thoughts and edited heavily.
    How could the Higgs field be absent since in QFT it's an integral feature of the vacuum? If you do some checking it will become clear the Higgs field operates on only a subset of the fundamental particle zoo, and photons are not among the affected ones.
  9. Write4U Valued Senior Member

    Second thoughts are used when editing an original statement. The question now becomes is the edited post in error? I did not change the underlying logic. The thrust of my statement was that a photon did not have sufficient energy to accelerate faster than "c".
    Thanks, I did check on that and it seems to be that way. However, that does not answer why "c" is the absolute speed limit of all quanta of any value.
    Apparently you are not reading me correctly, perhaps my fault. That's why I edit. It is attempt to make my posts more transparent. There is no attempt to obfuscate.

    But you have not answered the question why the speed of light is constant @ "c", i.e not faster, not slower, but always constant. So why is "c" the absolute limit for zero (rest mass) particles?

    Why is there a limit at all? Does it have to do with insufficient energy for acceleration to a faster speed? And if it requires energy for acceleration, we are dealing with momentum, no?
    It is a simple question.

    Actually I have a secondary concept why c is an ultimate speed limit. It has to do with quantum action itself.
    Last edited: May 30, 2021
  10. Q-reeus Banned Valued Senior Member

    It's a brute fact of nature as manifested in our particular universe. In some other incarnation c could have an entirely different value. Well that's the pov in Multiverse/Cyclic-universe theories.
  11. Write4U Valued Senior Member

    But that is pure speculation and does not answer the question.
    In effect you are saying that we don't know. OK, I can buy that.

    But then that allows me to speculate also. IMO, "c" is the rate at which quantum events can physically manifest. Any faster speed does not allow sufficient time for quantum complete its quantum process.

    If we consider that quantum is dis-continuous, and that it requires time, we immediately run into the problem of time limits.

    From the Internet Encyclopedia of Philosophy (a peer reviewed academic resource)

    What Else Science Requires of Time
    .......much more (good stuff)

    This would suggest that quantum is time dependent and as light is a quantum phenomenon it requires time to renew its energy. This poses a time/speed limit. Could this limit be @ "c" , the fastest possible speed a quantum event can complete its function?
    Last edited: May 30, 2021
  12. sculptor Valued Senior Member

    is space a perfect vacuum?
    if no
    if different wavelengths travel at different speeds---except in a perfect vacuum
    if space is not a perfect vacuum
    can the speed of light ever be constant?

    (outside of a theoretical model)
  13. Janus58 Valued Senior Member

    It doesn't matter. Relativity is not dependent on the speed of light. The fact that light (in a a vacuum) has a speed of c is a consequence of Relativity. It comes from the fact that light, to the best of our knowledge, has no proper mass. Even if it were to be discovered that light in fact does have some non-zero rest mass, and didn't travel exactly at c in a vacuum, it would have no effect on the accuracy of Relativity.
  14. exchemist Valued Senior Member

    What ballocks.
  15. Write4U Valued Senior Member

    Yes, but we are not talking about Relativity. The question is about "constancy" and why this "constancy" at "c"?

    Obviously there is a limit, else a zero mass particle like a photon would continue to accelerate to infinitely fast. But it can't.

    So what causes this constant "limit" at exactly "c"? To my understanding that is the OP question.

    I have now speculated on two possible reasons, both backed up by links to confirmation of that position.

    I am trying ....... I am merely proposing and open to correction.
  16. Janus58 Valued Senior Member

    Because "c", is the invariable speed built into the universe. It is a universal constant factor that inter-relates time and space measurement. When one says that the speed of light in a vacuum(c) is a constant, they mean that all inertial reference frames will measure it as have the same value relative to themselves.
    So for example, if a flashlight is moving at 0.5c relative to you, you measure the light it emits as traveling at c relative to you, while someone moving with the flashlight measures that same light as moving at c relative to themselves. It's about how different inertial frame measure "time and space" differently, not about something physically acting on light.
  17. Write4U Valued Senior Member

    Well let's unpack this further shall we?
    Can we start by modifying that post to read "speed gives photons energy equivalent to mass?"

    Here is a peer reviewed explanation.

    Light has no mass so it also has no energy according to Einstein, but how can sunlight warm the earth without energy?
    Category: Physics Published: April 1, 2014

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    Light indeed carries energy via its momentum despite having no mass. Public Domain Image, source: Christopher S. Baird.
    IMO, that translates "not necessarily related to its "rest-mass". But at speed it does acquire energy
    equivalent of mass.
    And here we run up against the question "why is that speed @ c", what causes that specific limitation?
    Is this a physical limitation or an observational limitation? And are there any secondary effects from this
    specific speed? If time stands still @ "c" is that how entanglement behaviors can happen simultaneously
    at distance. Or does this speed limit enter into a new timeless dimension?
  18. Write4U Valued Senior Member

    Wonderful, I can follow that.
    But it does raise an additional question; "why does time stand still at "c" ?

    Is this perhaps due to the possibility that at this speed we enter a new timeless dimension, which would account for the simultaneity of "entanglement"?
    RainbowSingularity likes this.
  19. mathman Valued Senior Member

    He said it is. The laws of physics make it so.
  20. RainbowSingularity Valued Senior Member

    now this is what confuses me
    black holes are interacting with light as a particle not a wave ?

    removing the space between electrons & protons & positrons (gravitrons also probably not?)etc ...

    so folding space may be the ability to as desired, remove the space between electrons protons & nucli's ?
    this would allow the ability to fold space effectively as a field ?

    so if the mass of the object is shifted from one point to another as space is folded then it doesn't need to obey the laws of light speed because space its self remains constant at light speed, because the distance light travels is reduced to a very small distance
    smaller than we would possibly assume.
    [{[self caricature]}i do feel a bit like im poking rubber ducks in a bath tub wondering which one will develop a scram jet and fly off by its self as 6th gen stealth fighters fly over head un noticed]
    thinking out loud ...
    Last edited: May 30, 2021
  21. Write4U Valued Senior Member

    we might ask if there is an "in vacuo" space inside a BH .
    Exactly, what happens to in vacuo space with faster than light speeds? Do we enter another dimension where space is condensed (fields) or does time begin to slow down relative to space? d Moreover, does folding space reduce surface area? If I bend an 8 x 10 piece of paper does the surface area shrink?

    Only a wormhole, bypassing surface travel altogether, would breach the distance barrier, no? But then a wormhole would cause a paradox between current spacetime and past spacetime.
    I do this all the time. My math teacher once told me that philosophically there are no stupid questions, but practically there are plenty stupid answers......

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  22. Write4U Valued Senior Member

    The question is "why" and "which" laws of physics make it so? In a mathematical universe, such questions do have answers. We're just not quite sure how to pose the question.
  23. arfa brane call me arf Valued Senior Member

    Why is the speed of light a constant?

    Because, if it wasn't there wouldn't be a fibre-optics industry; high-speed communication wouldn't be an engineering course at any university.
    Come to think of it, there wouldn't be any radar either.

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