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From a modern perspective the relation of the time axis to the x axis is roughly the same as the relation between the x axis and the y axis. Saying that two eve
by jules 9y ago
From a modern perspective the relation of the time axis to the x axis is roughly the same as the relation between the x axis and the y axis. Saying that two events happened at the same x coordinate (delta x is 0) is a statement that depends on the observer. Another observer who is rotated with respect to the first will see the events at different x coordinate (delta x is not 0), because some of the x axis has been rotated into the y axis. Similarly, saying that two events happened at the same t coordinate (delta t is 0) depends on the observer. Another observer who is moving with respect to the first will see the events at different t coordinate (delta t is not 0), because some of the t axis has been "rotated" into the x axis.
This notion of "rotation" only differs from ordinary rotation by a minus sign. If you rotate the xy plane around the origin then points move in a circle x^2 + y^2 = const. If you rotate in the xt plane then points move in a hyperbola x^2 - t^2 = const.
Physically you "rotate" in the xt plane by accelerating in the x direction. This causes points to move along that hyperbola, which means that some delta x manifests as delta t and vice versa. We don't see that in ordinary life because we only move with respect to one another at incredibly low speeds, which corresponds to very small "rotations".
Imagine a world where all creatures are facing along the x axis with only very small deviations. These creatures may think that the x coordinate has physical meaning independent of the y and z axes. They might think that there is something special about their x axis. Similarly, we are all moving with roughly the same velocity through the universe. We initially thought that there was something special about our velocity, namely, we thought that we were at rest with respect to the aether.
- quadcore 9y agoedited 10 thousand times Very good explanation, thanks for your time. Still something that's unclear to me. Let say I'm observing a star moving away from me at speed of light. Will I see the star? If yes, it means that, those photon-things, have a property which I haven't. Some "move at speed of light" type of property. So now, we have two points on a line, the "value" of a photon (speed of light) and my "value" (speed x), do we? What about that? We cant call that speed because we are saying speed is relative. How do you call that property then? And what is the other bound? Cant be x right? Or another solution is that, light depends on the observer. Ok got it. 100% got it. Light both has a speed (speed being always dependent from the observer) and both has a property I havent. The key is that light has a special property I havent, but it isnt about speed. Am I correct?
- deleted 9y ago[deleted]
- jules 9y agoYou can't move with the speed of light. If you move at 99% of the speed of light away from the star you do see the star but it will look red because the light waves get stretched out. Photons indeed have the special property that they move at the speed of light. This speed is special. If A is moving relative to B and they both measure the speed of the same light ray they both measure the same speed. This is not the case if they measure a particle C going at less than the speed of light. In some sense the speed of light acts like an infinite speed in the sense that "c plus v = c" just like "infinity+x = infinity". But the plus in this equation is relativistic velocity addition: v plus w = (v + w)/(1 + vw/c^2) where c is the speed of light. You can see that if you set w=c you get v plus c = (v + c)/(1 + vc/c^2) = (v + c)/(1 + v/c) = c(v + c)/(v + c) = c. The speed of light has this property but the speed is definitely finite approximately 300,000,000 m/s.
- deleted 9y ago[deleted]
- quadcore 9y agoIf you move at 99% of the speed of light away from the star What is the light ray speed I measure in that case? 1% speed of light?
- Viliam1234 9y agoThe speed of light ray (in vacuum) is always 100%. Other things keep changing in a way that keeps the speed of light constant from everyone's perspective.
- quadcore 9y agoThank you that helps. Question: if I move away from A near speed of light, will I be seen moving near speed of light in all other frames?