General Relativity actually states that no particle with mass can be accelerated from below the speed of light to the speed of light.
It does NOT actually say that nothing can travel AT the speed of light or above it.
The equations state that it would take infinite energy to accelerate any mass to the speed of light.
Massless particles, such as photons, MUST travel at the speed of light, by virtue of being massless.
Any particles traveling faster than light, such as Tachyons, would require an infinite mount of energy to slow them down to the speed of light. As they lose energy they get faster.
This brings you into the realms of spacelike and timelike curves and the interchangeability of space and time in Einsteins 4 dimensional Spacetime.
Quantum Entanglement, as Robbo says, is one aspect where information appears to travel instantaneously and was described by Einstein as 'spooky action at a distance'. One explanation for this is due to the action of Advance and Retarded waves that travel forwards and backwards in time to exchange the information required to explain how one Entangled particle instantaneously knows the state of the other, once measured by an observer.
The beauty and non-intuitive nature of the Quantum world is displayed in the simple two slits experiment, showing that wave/particle duality is undoubtedly true, and the more and more complex variations over the years. The cleverest so far has been the use of a clever set up of prisms to allow a single photon to interact with itself and show it can act as both particle AND wave in the same experiment. Using the Quantum Tunnelling effect it would seem to split into two and interfere with itself at the detector.
@Robbo, sounds like you are as fascinated by this as me. Did you see the fairly recent claim that they think they may have a way around the Heisenberg Uncertainty Principle by utilising Entanglement? Can't remember the details exactly but it was something along the lines of Entangling a particle with more than one other particle and measuring position and velocity separately of the two Entangled particles. This would then enable both aspects to be deduced of the original particle, without actually observing it itself. Both values would be as exact as possible and thus violate HUP by virtue of knowing both to a finer limit than it allows.
Hi Reb, I think I'm right in remembering you are a physicist of some kind and well able to have pertinent views and opinions on such a subject and so I'll try to keep my comments as precise as I possibly can but please feel free to enlighten any ignorance I might display.
I think when you talk about the photon necessarily moving at C because it is massless is slightly misleading because I always thought the restmass was zero but it acquired mass by virtue of it going so fact?
As for being fascinated by all this?
Yes, I am because I have always tried to reconcile the sometimes [and maybe predictable contradiction] disparate worlds of science and religion.
I have always been confused about something and I've scoured the net and not found an answer to this the following problem; most scientists always condemn infinite regression as a reason why there cannot be a god ... I can't subscribe to this; I appreciate their thought process and can acknowledge the logic but we are talking about [if in fact you believe there to be] a god here and just because us pathetic humans cannot reconcile the notion of infinite regression when considering the birth of the universe and the consequential question of then who created god is grounds for denial?
Scientists use this logical conundrum as some sort of proof there is no god .. to me, this is completely illogical and there's an arrogant presumption here that humans are always able to understand this universe when in fact, this is just one case where we cannot always understand the nature of god.
You are obviously well aware of the hierarchical notion that a creator [of whatever you like but in this case the universe] must always be more complex than the creation .. a computer is a great example or indeed any creation of us humans.
With that in mind, I think to assume we can conclude the non-existence of a god on the basis of a negative [the fact we cannot come up with god's creator] is such an unreasonable position to adopt.
Reb, your views or maybe you can tell me where I'm wrong, either will be appreciated.