# What happens if C is faster than the speed of light?

@DennisN - That was awesome! Thanks. Let me see if I have this straight then. So for them to know, they measure say 100 photons and get 70% head 30% tails. Then go measure the other sample from lab B and it should be something statistically close to 30% heads and 70% tails. Is that correct? I now see how this cannot be used for communication.

The last part I'm not understanding is wouldn't you have to measure both samples at exactly the same time to know they are entangled? I mean when I go back to Lab B to make the measurement, who's to say that the results don't come up exactly as with Lab A since the coins are rotating and would only represent the mirror at the exact moment the measurement is made...

mfb
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The last part I'm not understanding is wouldn't you have to measure both samples at exactly the same time to know they are entangled?
No. There is no time-dependence at the photons, it does not matter at which time you measure them.
In terms of the coin-example, one coin would have to stop as soon as you measure the other one (but you cannot see it stopping). Ok, as you can see the analogy does not work here any more.

Hi again, sday! I'm a little hesitant to continue the discussion here, since the original post is about the speed of light, and entanglement really belongs in Quantum Physics. My suggestion is you start a thread over there, and perhaps copy over the previous relevant posts to the new thread. I can do it, if you'd like to (yes/no?).

Quick replies to what you said; Section 1: Yes, that's essentially correct, but I guess the result would be closer to 50%/50% for Alice and 50%/50% for Bob. The strange thing is that (ideally) every A/B pair would show head/tail or tail/head. Section 2: AFAIK, ideally, time does not matter. After photon A is measured, what matters is if photon B gets disturbed by something else (environment) before it is measured. If so, the entanglement could be broken.

My analogy was just an attempt to give you a taste of it, it's not perfect . Furthermore, there are other people on the forum who knows much more than me about it, that's another reason why I suggest a new thread in the subforum Quantum Physics.

(Thanks mfb, I see you posted while I was writing my reply, I agree with what you said.)

... My suggestion is you start a thread over there, and perhaps copy over the previous relevant posts to the new thread. I can do it, if you'd like to (yes/no?)....
Done, thanks

atyy
Thanks atyy(& OmCheeto),

I see now that my question would have been better formed by asking what would happen to the physics if light is not massless.

My question is:-
Suppose for example that light is not massless & has a velocity of 0.5C....would the universe as we understand it through our math, theories, laws & observations still remain generally true?
This review gives limits on how big the photon mass could be, taking into account current data.
Photon and Graviton Mass Limits

Imagine if we lived on a two dimensional plane, and we had NO understanding whatsoever of a height dimension.
With that in mind:
What if a 3 Dimensional being put a ring (vertically) through our two dimensional plane? We would have NO way of knowing that it was actually a ring. Instead, we would see two separate "dots or lines" from each side if the ring that appear on our plane. To us as 2 dimensional beings, we would see two separate dots that would seem to have no connection BUT if we were to "move" one of the dots, the other one would move with it instantaneously! When is reality we may be moving the ring sideways, it would appear to us as two dimensional beings that the second dot (other side of the ring) was moving instantaneously even though on another dimension they are part of the same thing. We may describe what was happening as "information" moving faster than the speed of light, when in reality, the two dots are part of the same thing (the ring) just in a higher dimension.
Maybe nothing is faster than the speed of light and the transfer of information between to entangled atoms, is really an illusion, when they may actually be part of the same thing in a higher dimension?
Just a way I like to describe it to people who may be unfamiliar with QM.

mfb
Mentor
If you push one part of a ring, the other part does not begin to move within faster-than-light time. This is a common misconception about solid objects. The movement will propagate with the speed of sound. In everyday objects, this is so quickly that you do not notice the delay, but it is there.

Apart from that, your ring would probably ruin the complete 2-dimensional world by making it 3-dimensional.

If you start from the assumption that spacetime is symmetric in certain sensible ways (in particular, symmetry between different frames of reference), then you get either special relativity or Galilean relativity. In SR, there is some invariant speed, which we call c.
If we assume special relativity, then via the lorentz transform, the relative speed between any two objects has a maximum constant value. This value also happens to be the speed of light.

If you measure something faster then the maximum (ie c) then the geometry breaks down, special relativity breaks down, and so does much of physics for the past century.

Your right, hadn't thought of that in terms of this issue. In that case Relativity would still be violated. Good point.
Unless matter (and light) could propagate faster in another dimension that has a different set of laws...obviously thats just philosophical. Good point though!