# Light at speeds faster than the speed of light?

Ibix
I know Feynman was an accomplished mathematician, but he seemed to think in visualizations. Geometry and diagrams first, math proofs later.
I think Feynman always overlooked (edit: or "underplayed", perhaps) the fact that he was - well - Richard Feynman. He had pictures in his head that worked right because he understood the maths to the point that he didn't need to do it explicitly anymore. If you don't understand the maths, your pictures probably aren't pictures of the real world.

The problem is that you are imagining an inertial frame of reference that moves at the speed of light. However, the speed of light is constant in all inertial frames of reference. That means that in a frame moving at the speed of light, light is travelling at zero and 3x108m/s at the same time - which is nonsensical. The conclusion is that there is no such thing as an inertial reference frame moving at the speed of light. The infinities that pop up when you try to figure out what's going on in an inertial frame moving at the speed of light is the maths' way of telling you that you are doing something illegitimate.

Given that you can't have an inertial reference frame travelling at the speed of light, you can't really "reason your way through" it to what happens (or not) at hypothetical speeds greater than c. I think you'd need to develop a theory that does permit self-consistent descriptions of travel at the speed of light then show that it reduces to relativity somehow before you could reason like that.

Wes Tausend
Gold Member
Ibix,

That idea of a frame traveling at c, so therefore light cannot travel also at c, does appear in a FAQ here, but it seems contradictory in itself and I find it confusing and a bit useless for the moment, until I understand better. We do not regard a frame traveling at 1/2 c, or even 99.999%, as preventing light from still traveling at c as a problem, so why would any faster speed, including that of c, be precluded. "At what speed does this dire property changeover take place?", does not seem like an illogical question, at least in my present state of comprehension. I almost think the problem is the present math cannot easily deal with zero and infinities.

One of the reasons I mention my fondness for such a light-frame, is that I think I first read of it in one of Isaac Asimov's books, plus I believe Einstein himself imagined, "riding on a beam of light", in one of his thought experiments. This way of thinking does bring up harboring "dated views" though.

Rather than a theory, I worked out a different self-consistent way to solve the dilema over 35 years. It is not a theory because it contains no new math, but certainly rather uses basically the same math as standard GR and SR. Therefore it is technically only a conjecture. I actually joined here with the intention to finish resolving the nagging idea as either innovative or junk, since at that time such discussions were allowed. Meanwhile, I worked long hours until I retired and postponed resolution. Now this resource is gone with new rules (understandable). Furthermore, the local college astronomy instructor that I had discussed this with, passed away. Now I'm probably screwed unless I can ask the right questions here without violating rules. The easy part was solving the puzzle. The hard part is getting anyone to look long enough to realize the pieces began to form a useful picture. I have no credentials other than I am an excellent mechanic... and the universe is just another machine begging to be disassembled.

Thanks again. I see Nugatory has quoted my post and maybe that will help.

Wes
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PeterDonis
Mentor
2019 Award
That idea of a frame traveling at c, so therefore light cannot travel also at c, does appear in a FAQ here
That's not what the FAQ says, and it's not what Ibix was saying. The point is that, since light must travel at c in every frame, there can't be a frame in which light is at rest. So any thinking you do based on an implicit assumption of a "rest frame" for light is meaningless; such a thing can't exist.

Wes Tausend
Gold Member
That's not what the FAQ says, and it's not what Ibix was saying. The point is that, since light must travel at c in every frame, there can't be a frame in which light is at rest. So any thinking you do based on an implicit assumption of a "rest frame" for light is meaningless; such a thing can't exist.
Peter,

Thanks for your reply. I agree light must travel at c in every frame, at least relative to matter.

I think my understanding can wait. I've taken the OP's thread off subject and for that I apologise. Thanks all.

Wes
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PeterDonis
Mentor
2019 Award
And on that note, this thread is closed.