Observing Light's Relative Speed

[Superstring]

From what I remember in school, it's like this:

*Light always goes the speed of light, no more, no less.

*Light is always observered as going the speed of light, relative to your speed, even if you're going half of the speed of light from behind this beam; you still observe that it is going the full speed of light away from you.

So let's say you're going half the speed of light behind a beam of light, just like I said, and someone else is standing by, observing as this beam of light passes by, followed by you. Doesn't that mean both people would be making two totally different observations? That doesn't mean there would be two different things happening for like, two people's different realities, does it? Such that there's one reality where the beam of light passed the stationary observer much sooner than the observer witnessed?

I can't think of what else could be implied under this law, except that maybe length and time dialation for the chasing observer affect things somehow..

[Snowflake]

*Light always goes the speed of light, no more, no less.The speed of light changes when it passes through a material of any kind.
Light is always observered as going the speed of light, relative to your speedNo, it's not. If you travel at the speed of light, relative to a photon also traveling the speed of light, that photon will not appear to be moving (relative to you).
That doesn't mean there would be two different things happening for like, two people's different realities, does it?The same thing is happening for both person's realities. It's just that one person has "no" velocity, and the other has a velocity which is 1/2 that of the speed of light. The observations will be different because they are in different relative frames.

[zhang_bob]

The speed of light changes when it passes through a material of any kind.
Then speeds back up or down.

[Superstring]

The speed of light changes when it passes through a material of any kind.

lol, I meant in a vacuum you son of a bitch :whyi: Good point though, that was a terribly incorrect thing to say.

[Snowflake]

Then speeds back up or down.Yes, I probably should've mentioned that, but my statement was still correct, as it implied what you said.

[zhang_bob]

Yes, I probably should've mentioned that, but my statement was still correct, as it implied what you said.
I have always wonder why and how it does that.

[Superstring]

It's just that one person has "no" velocity, and the other has a velocity which is 1/2 that of the speed of light. The observations will be different because they are in different relative frames.

Ohkay, I think I see now...yeah of course, the moving dude observes things happening in a faster time reference, so it still looks like the speed of light to him....righto! thanks Snowflake :soap:

[Superstring]

I have always wonder why and how it does that.

I think it has something to do with the existance of additional dimensions we can't see...

[zhang_bob]

I think it has something to do with the existance of additional dimensions we can't see...
So you think it to do with string theory?

[Xenophon]

No, it's not. If you travel at the speed of light, relative to a photon also traveling the speed of light, that photon will not appear to be moving (relative to you).The same thing is happening for both person's realities. It's just that one person has "no" velocity, and the other has a velocity which is 1/2 that of the speed of light. The observations will be different because they are in different relative frames.
This is wrong. Light does always travel at the speed of light relative to an observer (in a vacuum), no matter what that observers velocity is, that is the whole point of the theory of relativity. This has some pretty phenomenal consequences.

I don't have time to figure out the equations right now, but basically time and distance will be different for the two observers. As a general rule with relativity just divide everything by sqrt(1 - v^2/c^2) and you will get the actual value that you want.

[Snowflake]

Light does always travel at the speed of light relative to an observer (in a vacuum), no matter what that observers velocity is, that is the whole point of the theory of relativity. This has some pretty phenomenal consequences.Did you read what I posted? I didn't say it did.

[Xenophon]

Did you read what I posted? I didn't say it did.
Obviously I don't understand what you are saying here then.


No, it's not. If you travel at the speed of light, relative to a photon also traveling the speed of light, that photon will not appear to be moving (relative to you).
If you are travelling at the speed of light relative to a photon, according to your reference frame, time will not elapse for the photon, and it would remain stationary, however you would then be travelling at the speed of light, and therefore the light would be travelling at the speed of light relative to you. I don't understand how you are getting around the fact that in a vacuum the difference in velocity between light and anything else will always be the speed of light.

[Snowflake]

If you are travelling at the speed of light relative to a photon,Maybe that is the problem. You are not traveling at the speed of light relative to the photon. Both you are the photon are traveling at the SAME speed, relative to you the photon would not appear to move.

[Xenophon]

Maybe that is the problem. You are not traveling at the speed of light relative to the photon. Both you are the photon are traveling at the SAME speed, relative to you the photon would not appear to move.
Dude, it just doesn't work that way. You CAN'T move at the same speed as a photon. That is what the theory of relativity is all about.

[Xenophon]

http://en.wikipedia.org/wiki/Speed_of_light#Physics

[Edmond Zedo]

The speed of light changes when it passes through a material of any kind.No, it's not. If you travel at the speed of light, relative to a photon also traveling the speed of light, that photon will not appear to be moving (relative to you).The same thing is happening for both person's realities. It's just that one person has "no" velocity, and the other has a velocity which is 1/2 that of the speed of light. The observations will be different because they are in different relative frames.
"I'm afraid it is you who are mistaken...about a great...many...things."

If you're traveling at the speed of light, all light still appears to be moving at the speed of light relative to you. Time likely passes regularly to you, but if you were to slow down to "normal" speed, you'd notice that some infinitlely large timespan had passed in the normal universe (Not sure of the precise theory/math on this one). Since, compared to Earth-time, say, time would've stopped for you. That's relativity.

[mr. treat]

Dude, it just doesn't work that way. You CAN'T move at the same speed as a photon. That is what the theory of relativity is all about.

he's speaking theoretically. if you were a photon observing another photon what would you see? you'd still see the other photon travelling at the speed of light, i think.

[Xenophon]

he's speaking theoretically. if you were a photon observing another photon what would you see? you'd still see the other photon travelling at the speed of light, i think.
Photons are wierd though. Essentially time doesn't pass for a photon, according to it's perspective it can go anywhere in the universe instantaneously.

If you know linear algebra, imagine everything has a velocity vector in four dimensional space-time with a constant magnitude of c. According to a body-fixed reference frame for any object, the velocity vector is heading completely in the time direction. However, if an object is moving relative to that frame, its velocity vector is rotated slightly from the time direction. Well, photons exist in a three-dimensional subspace of our four-dimensional vector space, the nullspace of that subspace is the time direction. So basically, the photons are stuck moving in physical space because they aren't allowed to move in time.

[Dunearhp]

he's speaking theoretically. if you were a photon observing another photon what would you see? you'd still see the other photon travelling at the speed of light, i think.

Only a massless particle like a photon is capable of travelling at the speed of light. As Xenophon has pointed out, from the photon's perspective, travel is instantaneous (time does not pass). In this state the photon can make no observations about other objects, determinations of speed are undefined.

[euterpenc]

Well realtive to my position, light has no speed (supposing I'm in a lightless room). Ha, take that physics, suck my nuts.

[Xenophon]

Well realtive to my position, light has no speed (supposing I'm in a lightless room). Ha, take that physics, suck my nuts.
Zeitgeist communicates with INTPcentral telepathically because his monitor doesn't emit light.

[Snowflake]

Well realtive to my position, light has no speed (supposing I'm in a lightless room). Ha, take that physics, suck my nuts.:rofl:

[Dunearhp]

Until we shine light on him, zeitgeist shall remain in an entangled dead/alive state.

[Google Monster]

He doesn't exist.