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falling light

still cant measure the effective rest mass
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Jim understands gravity bends the path of a photon…

It could be that the photon is bound to a curved pathway - or the photon has effective rest mass.

If a photon falls in a gravitational field - a photon emittted perpendicularly to parrallel mirrors will descend.

(Also the assumption of zero rest mass is discontinuous)

madness, Oct 22 2011

Deflection of light due to gravity http://books.google...approach%3F&f=false
[ldischler, Oct 26 2011]

[link]






       Jim fails to demonstrate any form of invention or innovation via these revelations.
Alterother, Oct 22 2011
  

       Gravity bends the spacetime through which the photon travels in a straight line.   

       Inventive misunderstanding isn't.
lurch, Oct 22 2011
  

       Maybe it's my lack of quantum physics knowledge [I apparently don't even know enough to see that this *isn't* quantum physics], but I don't see the invention, either. (If you're a reader who "gets" this, please translate. Thanks!)   

       [Edit: at least one commentator sees this as "a cool experiment", so I'm holding off.]
jutta, Oct 22 2011
  

       This would be more relativity than quantum physics, but I don't think it makes much difference.
MaxwellBuchanan, Oct 22 2011
  

       This makes more sense than it might seem at first reading. By bouncing a photon between two mirrors--the surfaces of which are parallel to the direction of gravity--madness expects to observe whether a photon falls at g, like any mass.
ldischler, Oct 23 2011
  

       Well of course the photon would fall.
DIYMatt, Oct 23 2011
  

       //Well of course the photon would fall.//   

       Since a photon has no mass, it wouldn't fall. If it did and the photon were traveling straight up from the earth, you would measure a constant decreasing speed. But photons don't act that way. They become red shifted instead.
ldischler, Oct 23 2011
  

       I think the assumption is based on observations that photons sometimes exhibit properties of massive particles, which is one of the features that make them unique. Key word: 'sometimes'.
Alterother, Oct 23 2011
  

       //This would be more relativity than quantum physics, but I don't think it makes much difference.// Marked for tagline
theircompetitor, Oct 23 2011
  

       //Key word: 'sometimes'.// But in this case, they would. Gravity does affect photons causing them to bend towards the source, see gravitational lensing. If you fired a laser perpendicular to the two mirrors and had an instrument that could measure the location of the "impact" of the reflected light, it should show up maybe a nanometer lower than the original source. Bun for an interesting experiment.
DIYMatt, Oct 23 2011
  

       // a photon emittted perpendicularly to parrallel mirrors //   

       You mean like a laser?
Ling, Oct 23 2011
  

       This Idea needs to specify that the mirrors are perpendicular to the local gravity field, so that the photon starts out traveling horizontally across the local gravity field.   

       The main problem is that mirrors are not 100% reflective, so the photon would get absorbed before falling any significant distance in an ordinary gravity field like Earth's.
Vernon, Oct 23 2011
  

       Yes, but on the plus side, the cat would probably survive.
Alterother, Oct 23 2011
  

       Gravity definitely affects light, but that fact doesn't prove that it has mass, rest or otherwise.   

       I have to go ahead and back up jutta's MFD as there is no idea here, or if there is there is, it is widely known to exist, as observing the displacement of light due to gravity is well understood and used in scientific instruments.
MechE, Oct 24 2011
  

       There is no reason to MFD this. He isn't suggesting that gravity affects light, that is well known. I had to read it a couple times but he's proposing a cool experiment - if you bounce a photon between two mirrors it won't reflect straight back to the source, it will fall slightly as it bounces.
DIYMatt, Oct 24 2011
  

       // He isn't suggesting that gravity affects light... if you bounce a photon between two mirrors it won't reflect straight back to the source, it will fall slightly as it bounces//   

       I don't get the difference.   

       If there is one, and most of us have missed it, then perhaps [madness] would consider putting a bit more effort into the idea. Just because you can chip away at a lump of rock to make a statue, it doesn't mean the statue was there to begin with.
MaxwellBuchanan, Oct 24 2011
  

       Conversely, seeing that the statue is already there doesn't mean you're the one that can free it from the stone.
Alterother, Oct 25 2011
  

       //he's proposing a cool experiment // - a cool *thought* experiment, unless you have some mirrors of 100% reflectivity.
hippo, Oct 25 2011
  

       // on the plus side, the cat would probably survive //   

       We assure you the cat will not survive.   

       // gravitational lensing //   

       Gravitational lensing happens not because the gravitational field acts on the photon, but because the field distorts space-time; from the photon's point of view, it never deviates from its straight line.   

       Consider three equidistant points A, G and B, all lying on a straight line in a region of space that is for experimental purposes homogenous and isotropic.   

       At G, let there be an arbitrarily large point mass.   

       if a photon or a physical object is launched directly from A towards B, it will strike G.   

       If a physical object is launched from A with sufficient velocity at an angle +dL from A towards B, such that the gravitational field of G will cause its course to deviate by -2dL, then the object will strike B   

       If a photon is launched from A with velocity C at an angle +dP from A towards B, such that the gravitational field of G will cause its course to deviate by -2dP, then the photon will strike B.   

       However:   

       When the physical object is located at its nearest point to G, an observer on the object would note that external distant points of reference were changing their relative positions as the path of the object was deflected by the gravity field of G. This is clearly observable from Earth-orbiting satellites.   

       An observer on the photon would not see this effect. The observer would perceive that they are passing from A to B with no deflection, since the photon is travelling in a straight line; it is space- time that is curved.   

       [MB] is correct when he states that this is Relativity, not Quantum Physics.
8th of 7, Oct 25 2011
  

       Space and time, and I suspect spacetime, do not exist. There is only mass and velocity. A distance, d if you must, between two objects is defined by the mass and velocity of the system...
madness, Nov 05 2011
  

       Space and time, and I suspect spacetime, do not exist. There is only mass and velocity. A distance, d if you must, between two objects is defined by the mass and velocity of the system...
madness, Nov 05 2011
  

       The mere fact that you were able to accidentally double- post your last anno disproves your assertion that space- time 'does not exist'. I think, however, you may be confusing a fundamental property of nature known (to us) as space-time (or space/time) with the theoretical construct humans have devised in order to observe it, which conveniently carries the same title.
Alterother, Nov 05 2011
  
      
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