Speed of light

[Alter-Fox]

since A is c-1 and is going 1mph faster, that would mean the speed of light would only be 2mph from B's perspective

This is how I understand it.

Time dilation (time slowing down as you speed up) is related to the speed of light so that no matter how fast you move, the speed of light appears the same (because light is not affected by time dilation).

Also, if you were moving at the speed of light, you would be frozen in time.

From Earth's perspective, B only has 2mph to go to reach the speed of light. A is already halfway there as it only has 1mph to go instead of 2mph.
If B is stationary, the speed of light still appears to be the speed of light. If A is already halfway there, A is going half the speed of light.

I'm not sure what to say about this. It seems to make perfect sense but also make no sense depending on how I think about it.
I have a friend who's taking physics in university. I'll show this to him and see what he thinks.

[Foil]

So, what I'm asking is if B saw itself as stationary, what speed would A appear to be going? It can't be 1mph, otherwise the speed of light is only 2mph.

Spaceboy, I believe you're still thinking too linearly about relative velocities. You're treating it as a set of linear equations with c as a constant, but that's not how it works.

A and B see a 1mph relative velocity between them. That looks pretty much like 1mph to both.

Earth, on the other hand, sees relative velocities of c-1 and c-2 to A and B. The relativistic effects are pretty heavy there, so I think you're correct that the apparent difference in velocity (1mph between A and B) is skewed by relativistic speed, but it's not quite the "half the difference = half the speed of light" equation, either.

What may help is working out the Minkowski Diagram for each of the reference frames.

[S13driftAZ]

Keep debating!

Man, this crap is cool. but I cant even comprehend the definition of paradox.. i still like physics though

[Spaceboy]

So, what I'm asking is if B saw itself as stationary, what speed would A appear to be going? It can't be 1mph, otherwise the speed of light is only 2mph.

Spaceboy, I believe you're still thinking too linearly about relative velocities. You're treating it as a set of linear equations with c as a constant, but that's not how it works.

A and B see a 1mph relative velocity between them. That looks pretty much like 1mph to both.

Earth, on the other hand, sees relative velocities of c-1 and c-2 to A and B. The relativistic effects are pretty heavy there, so I think you're correct that the apparent difference in velocity (1mph between A and B) is skewed by relativistic speed, but it's not quite the "half the difference = half the speed of light" equation, either.

What may help is working out the Minkowski Diagram for each of the reference frames.

I've read that link a few times and havent really grasped it yet, though I havent looked it up elsewhere.

Also I did say it would be half the speed of light if it was linear, but that I'm sure it isn't...

I'm sure it's somewhere along those lines, but the answer would only be half the speed of light assuming relativity is linear, which I'm sure it is not.

So at the same time I doubt it's anywhere near 1mph.

[Thenior]

...Even though you are going 99mph, the speed of light still appears to be going 100mph.

This is because your time has slowed down, so it appears everything around you has sped up.

I realize that this is sort of focusing early in the topic, but that doesn't make sense.

You are going VERY fast, to the point that time is beginning to slow down. That doesn't mean that everything around you speeds up. Your going so fast, everything around appears to slows down.

Right? Or should I just shut up...

[Spaceboy]

You are slowing down. If you were to accelerate to near c and you had a twin on Earth, when you come back that twin could easily be 50 years older than you.

Imagine you and the twin facing eachother, yet you age as if you're going light speed and your twin ages as if he is staying on Earth:
You would see your twin aging rapidly. The entire world that twin lives on is aging as rapidly as he is...
Since your time is slowing down it appears as if the universe is speeding up.

[Thenior]

Bare with me, I am trying to follow. Let me know if I am taking this too far off track.

I'm the type that has to read it like 10 times before I finally get it.

If I speed up, that makes time slow down for me. So speed/time have an inverse relationship?

So if Twin A speeds up, his time slows down. Twin A's Time is Twin B's - X. From Twin A's perspective, it appears Twin B is Twin A's time + X.


Got it.