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edited 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 a
by quadcore 9y ago
edited 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?
- jules 9y agoWhat about another person walking around in your spaceship?
- quadcore 9y agoThank you. So the fact that you always see light at speed of light whatever is the frame, isnt because light is going at speed of light but because light is light. What's different between a photon and my spaceship is not so much that my spaceship cant reach a full 100% speed of light, but that youll always see a photon at speed of light because of some "magic" property which cause isnt speed. Is that correct?
- jules 9y agoIt is speed, the speed of light. Particles that have zero mass go at the speed of light. This is a property of the particle. That there is a maximum speed is a property of spacetime however. Even if there were no massless particles we could still discover special relativity, for example by noticing that when you speed up particles they can't get past a particular speed. In the large hadron collider they can speed up particles to 99.9999991% of the speed of light.