Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Ever-present vacuum

  1. Apr 12, 2010 #1
    If light travels at constant velocity c in vacuum and constantly relative to any inertial reference body, then does that not mean all bodies and space are perforated, or rather filled in, with vacuum within which light can travel?
     
  2. jcsd
  3. Apr 12, 2010 #2
    I fail to grasp what you mean by 'filled in with vacuum' - vacuum is not a substance.
     
  4. Apr 13, 2010 #3
    Yeah, it was difficult to express for that reason. Rather, if light travels at constant velocity c in vacuum and constantly relative to any inertial reference body, then is not the whole of existence greatly vacuum within which light can travel constantly?
     
  5. Apr 13, 2010 #4

    Mentz114

    User Avatar
    Gold Member

    Classically, light requires no medium and travels through empty space. In quantum theory the vacuum cannot be ignored and has measurable effects. But I don't think there's a theory of light transmission that involves the vacuum as a medium.

    The fact that all observers will locally measure the speed of light to be the same begs an explanation and some people think it can be found by giving light a medium, but that transfers the 'weirdness' to the medium.

    Not long ago there was an experiment (PVLAS arxiv.org/pdf/hep-ex/0512022) which looked for an effect of the vacuum on a light beam in a very strong magnetic field. The experiment failed to detect anything beyond reasonable doubt.

    You might also be interested in this, which discusses new experiments,

    www.nature.com › Journal home › Current Issue › News and Views
     
  6. Apr 13, 2010 #5
    Thanks, this was the point I was getting at. Does it not seem that an ever present vacuum about and within any inertial reference body would cause/ allow light to travel at constant velocity throughout all space, with only slight regard to said reference bodies? This is not a medium, as it is nothing, but still acts as one.
     
  7. Apr 13, 2010 #6

    Mentz114

    User Avatar
    Gold Member

    I don't think having anything acting as a medium can explain why light speed ( in vacuo) is measured as the same in all inertial frames. What happens inside material bodies is subject to different laws, so the fact that the vacuum is everywhere doesn't actually explain much. The passage of light through anistropic crystals is rather complicated to model and not like a beam of light propagating in empty space.

    If you're looking at light as a classical phenomenon in relativity, no medium is required, and it doesn't help to suppose one.
     
  8. Apr 13, 2010 #7
    I am not supposing a medium, I am supposing an ever-present vacuum, about and within all inertial reference bodies, through which quantum energy travels constantly. Does not light traveling through molecules travel also at c?
     
  9. Apr 14, 2010 #8

    ZapperZ

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    This would act as a strange "medium" if that's the case. A "medium", using the usual definition, tends to have a certain preferred frame. The water you see in the pond is at rest in a particular frame. So this is what people normally associated with a medium.

    You've simply redefined this and want to attach it to vacuum, or to light's properties. It is OK if you're the first person to want to define the word "medium", but you're not, especially when this vacuum doesn't behave like any other medium that we know. So you're trying to disguise what is really a tennis ball and trying to pass it as an apple.

    Zz.
     
  10. Apr 14, 2010 #9
    Forgive me, but is this not the same as proposing that the vacuum be similar to the fictional "Luminiferous Aether"?
     
  11. Apr 15, 2010 #10
    I indeed am using the term medium loosely. And yes, the point I was getting at, is that the ever-present nothing through which radiation travels, while by definition is not a wave medium, but in fact is the only space/ place for electromagnetic radiation to be found and as this vacuum is absolutely frictionless (it's nothing) it allows all photo-electric energy to travel constantly throughout. The luminiferous aether proposed by physicists centuries ago was perceived to be a tangible thing with physical properties relate-able to other physical bodies and indeed it does, in a sense, but it is the zero factor. If you read about descriptions, "observations", and theoretical necessities of the proposed aether, they very clearly describe a vacuum. It doesn't need a particular frame as it is the presence of nothing. And zapperz, if you read my post right before yours i am not supposing a medium, by definition, but an ever-present vacuum for photo-electric energy to propagate through, about and within all inertial mass bodies. This vacuum indeed cannot be ignored and clearly plays a very large part of our physical world. IT IS NOT A MEDIUM, but is the "substance", also used very loosely, for constant light propagation.
     
  12. Apr 15, 2010 #11

    zonde

    User Avatar
    Gold Member

    Would like to add that looking at measurement process can help much more for understanding why light speed is measured as the same in all inertial frames.

    About helping or not it's quite subjective.

    If we take light as identifiable phenomenon then from classical world we have two options - compare it with something that exists independently from surrounding like particles or something that depends from surrounding like medium waves.
    Particle type tend to have different speeds and tend to come to rest because of friction and inelastic collisions.
    Wave type however tend to maintain certain common speed and instead of collisions you have superposition of waves.
    And of course there are something that is more in between the two - solitons that are waves with some particle like features and medium in different phases that is particle type but more linked to surrounding.

    I think it's quite obvious that medium waves (or even better solitons) are much closer to description of light then some oscillating particle.

    So don't say it does not help to suppose one.
     
  13. Apr 15, 2010 #12

    ZapperZ

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    Then don't call it a "medium".

    Furthermore, you are now proposing something new, and if you wish to do that, then I will point to you the IR forum.

    If in physics, there isn't a need for such a definition, then the impetus is on YOU to show why your scenario is necessary. What new physics can we separate out based on current physics and your "physics" that would allow us to adopt such a thing. After all, why would we want to pay attention to your hypothesis when it doesn't change anything?

    Other proposal about quantum foam, etc. do make predictions that differ from current understanding, i.e. they are falsifiable. What you just described produces nothing that can be tested to differentiate it from our current understanding. So what's the point? Simply to adopt it as a matter of taste?

    Unless you have some specific valid references to back this up, further development of this idea should be done in the IR forum.

    BTW, don't use the phrase "photo-electric". That already has a well-defined phenomenon associated with that, the same way a "medium" already has known physics associated with it. If you want to talk about light, says "light" or "electromagnetic wave". Don't try to over-jazz it with unnecessary embellishment.

    Zz.
     
  14. Apr 15, 2010 #13
    Thank you for the advice Zz. I am indeed currently doing independent research into this and several other related theories, and while they do not necessarily drastically change the scope of physics I feel they provide applicable insight and explanation to physical phenomenon. I think predominant physical theory of the past few centuries is strong skeleton, greatly supporting our understanding of a beast we haven't totally identified yet. For this reason I feel any new, correct theories wont change the shape and form of the beast, but rather help us fill it out. I understand how new propositions based on a theory are necessary to weed out the right from wrong via falsifiability, and I will try hard to find such propositions based on this theory and others I hold, so that they may be put through the weeding process.
     
  15. Apr 15, 2010 #14

    ZapperZ

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    Then this thread is done, so I'll stick a fork into it.

    Zz.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook