Speed of Light Barrier

I read a good analogy in Brian Greene's Fabric of Space and Time. The analogy is only useful for drawing a helpful image, it isn't really analogous to reality.He likened space and time to a two dimensional space, with space being one orthogonal axis and time the other. Imagine you're moving at a constant speed. When you're moving parallel to the time axis you're not moving through space at all, and so you proceed through time at the normal rate. But the more your direction of motion becomes parallel to the space axis, in other words, the faster you move through space, the more slowly you move through time.Hope this is relevant, I didn't read the whole thread.--Percy

Your question could be asked about any of the fundamental constants, and in fact, the speed of light is thought to be a function of a more fundamental constant called the fine structure constant, probably already mentioned in this thread.Physicists working on the theory of everything are disturbed most by their inability to derive the fundamental constants from first principles. For the most part, the constants have to be measured and cannot be derived. The current best hope is that superstring theory provides the foundation for eventually doing this.My favorite question is, "Why something instead of nothing?" The question isn't original with me, I forget who asked it first.--Percy

You replied to Message 1, and there were 84 messages after that. Have you read the entire thread and still feel the same as what you posted here? Or are you trying to reset the discussion back to square one?--Pecy

Photons have no mass. For objects with mass m moving at velocity v relative to you, apply this equation to find the mass you'll measure: As you can see, the denominator of that equation becomes 0 for v==c, and so the mass you perceive will be infinite for objects traveling at the speed of light, and the impossibility of infinite mass explains why you'll never perceive any object with non-zero mass traveling at the speed of light. For one thing, it would take infinite energy to accelerate a mass, no matter now slight, to the speed of light.So obviously the only things that can travel at the speed of light must have no mass, and the photon fills the bill in this respect.--Percy

The universe is thought to be unbounded, so there's no such thing as objects at the boundary, but there are certainly objects at the boundary of our perception. The further away the object the faster it is receding from us due to the expansion of the intervening space. Objects far enough away are receding from us faster than the speed of light, but of course we cannot see them because the light will never reach us.But the portion of the recession velocity contributed by the expansion of space is not part of the velocity of the object. Imagine a broad rubber strip stretched between your hands and upon which ants are walking. Ants at opposite ends of the strip have a velocity relative to one another as they walk randomly about. When you begin moving your hands apart and stretching the rubber strip longer and longer so that the ants recede from one another, the velocity contributed by your stretching of the rubber strip is not part of the ants' velocity.The stretching of the rubber strip is analogous to the expansion of space, and that expansion is separate from the velocity of objects within that space.--Percy

Relativity theory is very mathematical. Physicists and cosmologists plug values into the relativity equations to make predictions, then they peer through telescopes or otherwise make measurements, and in this way they verify the predictions of relativity theory. This has been done over and over and over again with increasingly novel predictions. This kind of repeated confirmation is the hallmark of solid theory.Have you considered the possibility that you might be rejecting relativity prematurely? That perhaps a bit more study might be appropriate before drawing conclusions?--Percy

An ion drive would be limited solely by the amount of fuel it could carry, and if some kind of ramjet capability is possible then the sky's the limit, you could put as many 9's after the decimal place as you like.--Percy

Actually, the speed of light is always c. In a medium such as glass the photons are absorbed and re-emitted by the molecules, and the extra time this takes is responsible for the perceived lower speed. In between molecules the photons still travel at c.c is actually a measure of the fastest speed one part of the universe can influence another part. Two objects a light year apart cannot affect one another any sooner than a year. And for Tedrick's benefit, even if they're receding from one another, each will measure light from the other as traveling at c.--Percy

c is a constant of nature. One way we establish its value is by measuring the speed of light in a vacuum. The speed of light is also the same within a medium such as glass, but it is much more difficult to measure within a medium because the distance a single photon travels is minuscule before being absorbed. See Message 148.--Percy

Relativity has passed every test so far with flying colors. The evidence from reality has validated relativity to an incredible degree, and that's the actual fact of the matter at this point in time. If you think relativity is on shaky ground then you are not drawing your evidence from reality but rather from some source outside reality. It's always a fun challenge attempting a response to someone who expresses two opposite points of view in successive posts, apparently both agreeing and disagreeing with himself. First you say the equations of relativity are valid if you substitute the speed of sound (which is not a constant) for the speed of light c (which is a constant), then you say using the speed of sound is "insurmountable."Who knows what you were really trying to say, but we can easily do the substitution. I'll use the speed of sound in dry air at 1 atmospheric pressure and at a temperature of 20^oC, which is 343 m/s. So the mass of an object traveling at 1000 m/s is given by this equation: So using the speed of sound gives you an imaginary negative mass for a velocity of 1000 m/s. Since we can measure the mass of something traveling at 1000 m/s and know that it isn't negative and imaginary, we can conclude that relativity equations do not correspond to reality when we substitute the speed of sound for c. Actually, the speed of light falls out of the Maxwell equations: ε₀ is the electric constant, μ₀ is the magnetic constant. Maxwell's equations showed that c is a fundamental constant that is the upper bound on the speed of influence. In other words, no part of the universe can affect any other part of the universe faster than the speed of light.--PercyEdited by Percy, : Clarify a tiny part.Edited by Percy, : Another very minor clarification.

The maximum speed at which one part of the universe can affect another part of the universe, known as c, is woven into the fabric of our understanding of the universe. If c is wrong then much of our understanding of the universe is wrong. For this reason and this reason alone I believe the Cern findings will be found to be wrong.Historians of science are fond of noting that just before the dawn of the 20^th century scientists believed that the major advances in physics lay in the past and all that remained was tidying up a few loose ends, such as the spectrum of black body radiation. Perhaps we lay at the dawn of a similar era and the Cern findings and the elusiveness of the Higgs are hints of radically new physics soon to be discovered, as radical as relativity and quantum physics were a century ago.But I doubt it.--Percy