Relativity of Simultaneity (1 Viewer)

[Minai]

I was just reading over my notes and I got confused about something (Im either stupid or my notes are not clear enough)
but anyway, if a train was travelling at C, and the person in it is looking into a mirror, do they see their reflection or not?

 

[superhubert]

light is a constant for all observers, so in the train light still travels at 3 10^8ms, so there would be no difference to looking in a mirron at o ms

 

[Ronnie]

hmmm I know that if you looked at light.... you'd be able to see a changing changing electric and magnetic field ...... but I'm not sure wether you'd be able to see your own reflection or not!

errrr BlackJack? SpiceGirl? a lil help here?!?!?

 

[superhubert]

you could never see a changing magnetic and electric field not just because both forms of radiation are invisible, but because you can never travel at the same speed as a photon of light because no matter how fast you go, light will always travel at 3 10^8ms relative to YOU!

 

[superhubert]

although you're travelling away from the light source at c, realtive to you light still behaves under normal conditions at c, thus reflection refraction etc are all normal. this means you would see your image as normal. but an observer in another frame of reference v=o, wouldn't see an image even if they were in the correct line of sight. this is because relative to them the person and mirror are travelling at the same speed as light and no image could be seen. there are many theories as to what would be seen.. some believe that a pure or absolute blackness would bee seen, others believe that because they travell at c, time must completely stand still for the outside observer, (hence the theories of time travel at speeds in excess of c) and a 'hole' in the space-time continuum would be incurred. but until it is proven if light has mass and thus if speeds of c are achievable, it is all theory (relativity THEORY, thought experiments/gedunken)
don't ya just lov relativity?

 

[BlackJack]

...it doesn't look like you'll need me here... Ditto suprehubert's answer.

One theory at speed c says because of doppler shift you won't be able to be almost all of the light that reaches you because it's either be doppler shifted to gamma specturm or IF spectrum...there'd be no light reach you from behind, but you wiill 'see' v. distorted images.... yadda... yadda.. yadda..

 

[McLake]

Couldn't you see into the past? (ie when ever light last hit it)

 

[SgtSlick]

It all comes back to the belief in the aether model....

IF the either model was correct, light could go no faster than the train, therefore it would never catch up with the mirror to return as a reflection. The principle of relativity would be violated because to have your reflection dissapear is one way to detect motion (remember in a n inertial frame opf reference there is no way to detect motion)

If the aether model was incorrect, then the principle of relativity must not be violated and hence you would see your reflection as normal as light is travelling at 3x10^8 ms away from u. But to an observer outside the train the light would appear to be travelling at twice its normal speed in order to reach the mirror!

Einstein was sure that the aether model was incorrect and that therefore the person on the train witnesses a different time and distance for the path of the light to the person outside. SO light stays at C and yes, u can see your reflection.

 

[kate@bangas]

there were three possible outcomes from this experiment

1.Some beleived that the passanger in the train would not be able to see their reflection as the light rays cannot catch up with the mirror to form a reflection. This agravated the physics of the time as relativity stated there is no test you can do to distinguish an inertial frame of reference3 from rest.
2. Others believed that the passanger would see the reflection, but an observer on the side of the track would observe the image travelling at twice the speed of light. This contradicted Einsteins first postulation that the speed of light is constant irrespective of the observers frame of reference.
3. Einstein, who is thought to have made the correst assumptioooooooon, said that the traveller would be able to se his/her reflection, and the person on the side of the track would also see the reflection, but time would move differently for both observers.

 

[silent bob]

The way i see it is, because of the whole, infinate time, infinate mass bull we can never reach the speed of light so why bother thinkin bout it, it just confuses me....i need my confusion resourses for other physics things such as the entire ideas core...WTF?!?!?! *NEEDS MORE TIME DAMN IT!*

 

[superhubert]

but if light is proved to have mass then an infinite mass wouldn'd occur at c, thus it still could be possible to travell at this speed.....

 

[Ace-Pilot]

Or you could Just look in the mirror and you would be like

"Holy Crap, Ive gained Weight "

lets not forget mass dialtion ppl

 

[kaseita]

lol, but for all you know, you could just get denser, rather than fatter
of course you'd scream the moment you went on the scales
or the scales would at any rate

 

[superhubert]

its relativity ppl...you wouldn't feel any heavier because you're in the same frame or reference. it would just be everyone else telling you your fat!!!!(provided they can see you travelling at c)

 

[silent bob]

well...if mass dilation makes you seem fatter....then lenght contraction would make you seem thinner.....so really....you weigh more, but look thinner....damn! i gotta get me ass into outer space!!!!

 

[superhubert]

next time you get a speeding ticket tell the cops you were trying to look thinner and stay younger!!!

 

[silent bob]

LOL!
They'd probably give me the brethalyzer a couple more times just to make sure....Hey, now at least i know how one works...wow...i've learnt something! *steps back in awe*

 

[BlackJack]

I have a question though. Looking at time dilation...
At which speed do we get 'at rest'? We measured the clock travelling very fast around the earth in reference to our planet. They are right, the clock IS slower on the plane. But to the people on the plane they ALSO know the clock on the ground is faster, once they get back into the same frame as the first clock. How, if motion and rest cannot be defined from "inertial references"...?

Now we know, which one has a higher velocity, in absolute terms....

(note here, separate from this entire argument that there is another question: Are we are really in inertail references...)

BUT look at earth... it's spinning and hurtling through space like there's no tomorrow... wouldn't there be a speed "slower" than the earth, and thus have a faster clock than it?
We can ALSO empirically determine this, if we launch a space probe in all different directions off the planet and check the clocks...

If the Earth is still the fastest clock, then can we not say that the earth is at rest?

edit: more so, we can try to 'stop' a rocket in space... and have other rockets going in all different directions. Which clock(s) would be the fastest?

This might be where general relativity comes in...

 

[superhubert]

general relativity might have some answers. its for noninertial frames of reference. remember that general relativity is the revised edition, thus special relativity has its problems. there is no absolute time. "at rest" is a bad pronunciation thats come over time, t0 actually refers to absolute time, not at rest, and is defined as "the period of time in the frame of refernce that the event occurs." if you did your rocket experiment you would get different results because it isn't just matter that is expanding, but the space between it, like blowing up a baloon...so time would always be changing at an infinitly small reference frame. (provided that all space is expanding non uniformly) any ideas?

 

[SgtSlick]

Originally posted by BlackJack
I have a question though. Looking at time dilation...
At which speed do we get 'at rest'? We measured the clock travelling very fast around the earth in reference to our planet. They are right, the clock IS slower on the plane. But to the people on the plane they ALSO know the clock on the ground is faster, once they get back into the same frame as the first clock. How, if motion and rest cannot be defined from "inertial references"...?

Now we know, which one has a higher velocity, in absolute terms....

(note here, separate from this entire argument that there is another question: Are we are really in inertail references...)

BUT look at earth... it's spinning and hurtling through space like there's no tomorrow... wouldn't there be a speed "slower" than the earth, and thus have a faster clock than it?
We can ALSO empirically determine this, if we launch a space probe in all different directions off the planet and check the clocks...

If the Earth is still the fastest clock, then can we not say that the earth is at rest?

edit: more so, we can try to 'stop' a rocket in space... and have other rockets going in all different directions. Which clock(s) would be the fastest?

This might be where general relativity comes in...

In the words of Einstein himself:
"A thousand experiments may not prove me correct, but one experiment may prove me wrong"

See he knew that what he had developed was umm how do u say - a fluke! He knew he couldnt experimentally prove his work, problem is it seems like it might take someone of Einstein's ability again to actualy prove the Theory incorrect - think about that...

SgtSlick