Constant speed of light (1 Viewer)

[Wohzazz]

Ok i have trouble comprehending Einstein's experiment and decide to ask you guys for help

"If i were travelling in a train at the speed of light and i held up a mirror, would i be able to see my reflection? If the aether model was right, light could go no faster than the train. I could never catch up with the mirror to return as a reflection. The principle of relativity is thus violated because seeing one's reflection disappear is a way to detect motion. On the other hand, if the principle of relativity was not violated, the reflection must be seen normally which mean that it is moving away from the mirror holder at 3^10^6 ms^-1 . However, this would mean an observer on the embarkment next to the train would see the light travelling at twice the normal speed."
quoted from Jacaranda Physics

 

[Xayma]

Well the first problem there is that the hypothetical train is travelling at the speed of light. This is discussing that if the speed of light is constant, both distance and time are relative to the observers.

 

[abdooooo!!!]

so you typed the whole thing out? what don't you understand? the whole thing?

 

[Wohzazz]

yes i typed up the whole thingbasicly don't get the whole thing-
btw, this is Einstein disproving of the aether theory and putting forward his theory of relativity

 

[Xayma]

With the aether theory time wasnt relative. However, with the theory of relativity they are. Einsteing was saying that for the speed of light to be constant in that situation time and distance must be relative. This was dissproving the aether theory while supporting his relativity theory.

 

[Wohzazz]

Yes i understand what you're saying Xayma, but can you explain the situation described above and how that fits together to prove that light is ultimately absolute?

 

[Xayma]

It doesn't. When relativity was proposed all experiments came to the conclusion that light moved at the same speed in all conditions (exluding the medium through which light travelled). Ie if you run with a torch the speed of your running doesnt add with the speed of light. So it was assumed that the speed of light is a constant. Einsetiens Theory of Relativity proposes that this is the only constant and all other things (distance, time, mass) etc are all relative.

 

[abdooooo!!!]

all E albert was saying is that time is not universal, but rather velocity is. hence special relativity came about due to that reason. light is how we perceive time...

edit: time is not universal ie compared to the crappy newtonian day physics.

 

[Wohzazz]

Well how did the theory of relavity come about? Didn't it come because Einstein disprove the aether theory, that light requires a medium to travel through and thus the speed of light is relative to that of aether. Apparenty, it was prove by reasoning with this simple situation of the train i described earlier.

 

[Xayma]

If my physics teacher didnt borrow my copy of "A brief history of time" I would of looked it up. Ill check the internet. Check out this site http://physicalworld.org/restless_universe/html/ru_4_21.html

 

[Wohzazz]

Ok lets have a look at the situation,

'If the aether model was right, light could go no faster than the train.' why?

"this would mean an observer on the embarkment next to the train would see the light travelling at twice the normal speed."
why?

 

[Wohzazz]

Originally posted by Xayma
If my physics teacher didnt borrow my copy of "A brief history of time" I would of looked it up. Ill check the internet.

the first i've seen, usually you borrow from them

 

[abdooooo!!!]

i told you time is not universal, velocity is. thats all it is. so light will always travel at the same velocity for everyone while time is different for everyone depending on this equation v= d/t.

edit: brief history in time is not that brief...

edit: so if aether was true this thoery E albert and others proposed would be wrong then.

 

[Xayma]

Look at the link I posted above http://physicalworld.org/restless_universe/html/ru_4_21.html

If the aether model was correct, then time was a constant. However, distance could be relative. Since the light could not travel faster then the train (since it will cover the same distance in the same time) it would not catch up to the mirror. However, seeing ones reflection disappear indicates that the mirror is moving away from you (or you from it) which indicates that then the mirror is moving faster then the speed of light, or you arent going as fast as the train. Hence for you to see the reflection requires the speed of light relative to an observer outside the train for the speed of light in the train to be moving twice as fast as the speed of light he is experiencing. *Hopefully makes sense

However, since the Michaelson-Morley experiment proved the speed of light to be constant, then the aether model could not be correct.

 

[abdooooo!!!]

Originally posted by Xayma
If the aether model was correct, then time was a constant. However, distance could be relative. Since the light could not travel faster then the train (since it will cover the same distance in the same time) it would not catch up to the mirror. However, seeing ones reflection disappear indicates that the mirror is moving away from you (or you from it) which indicates that then the mirror is moving faster then the speed of light, or you arent going as fast as the train.

sshhh... isn't that what i said. i think people are not reading my post.

i don't know what you don't understand Wohzazz, its perfectly clear in jarcaranda (shit book) why don't you understand? or are you just puzzled by the historical developments leading up to this principle.

 

[Xayma]

No you just said that only velocity is constant, you didnt explain it

 

[abdooooo!!!]

but thats all it is. jacaranda already explained the rest... gay aether. physics is the gayest science ever... most hated out of the 3 bio, chem, phy. nothing you learn is right. they just teach it, then after some time they teach something disprove what you've learnt. first light, then wave, then aether, then photons, then i don't whatever else they can make up.

 

[Xayma]

Physics makes perfect sense. Yep the 11 or 12 deminsions is perfectly fine. Physics is the most expansive science there is, it deals on the largest scale as well from the inwards of atoms to the connection between galaxies.

 

[Wohzazz]

I just don't understand the situation described, but i think its becoming a little clear now

I'm thinking for the aether theory, on the carriage, the light is not moving at all. So then there will no reflection on the mirror or a still picture despite the person moving, because light does cannot catch up with the mirror so all light remains as though it is stationary (moving with the train at the speed of light).
By what I understand doesn't comply with.
"The principle of relativity is thus violated because seeing one's reflection disappear is a way to detect motion." how do you see reflection disappear on the train if aether was true?

 

[zeropoint]

Originally posted by Xayma
If the aether model was correct, then time was a constant. However, distance could be relative.

No, the hypothetical aether theory supports Galilean relativity in which time and distance are absolute, and position and velocity are relative to the observer.

Since the light could not travel faster then the train (since it will cover the same distance in the same time) it would not catch up to the mirror. However, seeing ones reflection disappear indicates that the mirror is moving away from you (or you from it) which indicates that then the mirror is moving faster then the speed of light, or you arent going as fast as the train.

This all makes sense (at least in Galilean relativity) except when you say ``or you arent going as fast as the train''. If your velocity relative to the aether is less than the velocity of a train moving at the speed of light, you will observe reflections.