I just read that whole "speed of light relative to the observer" thing and it brings up a lot of questions. Heres a mysterious question which doesn't really need to be answered either way this is answered the results imply that some crazy shits going on.

Lets say you have a train travelling at the speed of light . Hypothetically if someone in that train shone a laser pointer towards the front of the train the light won't just be suspended in one area in the carriage since it would only move at the same speed the trains going. The laser would hit the wall at the front of the train but obviously this makes no sense since an outside observer would measure the laser beam as going the exact same speed as the train.

What if you attached a big laser to the front of the train or better yet lets say the lasers shining from inside the train out the front window of the train. Lets say there was lots of mist so you could see the whole laser beam. Lets say the train conductor was looking out the front window. He should be able to see the laser beam since it will travel ahead of him at the speed of light relative. Would an outside observer see this laser beam?:confused::confused::confused:

Theoretically its impossible for the train conductor to see the laser beam but not the outside observer. ::confused:

Einstein's cows

:(:):rolleyes::eek::cool::cool::cool:Einstein's cows

eismien is a joke. 1 quadrillion miles from here?? 29484875856968569 light years.
EXPLAIN????
Take care BROTHER!!

But if the train was moving at the speed of light, would a forward-pointing light emitter even be able to project any light?

I think it's weirder to think what would light pointed backwards from the train look like to the external observer...

Yea thats a crazy thought. How fast would the light measure in the opposite direction of the train with the guy on the train measuring it. The train would be travelling away from the light at way more than the speed of light.

To an external observer it would just be the normal speed of light though.

Any time you have an observer moving the speed of light no descriptions make sense. Remember the two SR postulates -
1. The laws of physics work the same in all inertial reference frames.
2. All inertial reference frames measure the speed of light in a vacuum constant - c - whether the source is moving or not.

Because all observers locally measure the speed of light as c, there can be no inertial frame traveling at c - physics breaks down. Any questions on "the frame of reference of a photon" or what a photon "sees" are nonsensical because by the theory, the laws of physics don't hold (they don't qualify as reference frames).

Now if your train were going .999999c, that's a different story; all of your questions could easily be resolved.

ok, this is probably a simple question but what if one was on train moving at about the speed of a recently fired bullet, then some one stands on the back of the train and fires a bullet opposite the direction of the train. to a "stationary" observer would the bullet remain stationary and "float" in the air

ok, this is probably a simple question but what if one was on train moving at about the speed of a recently fired bullet, then some one stands on the back of the train and fires a bullet opposite the direction of the train. to a "stationary" observer would the bullet remain stationary and "float" in the air

No. If the bullet were fired exactly where the observer was standing, the bullet would basically appear in midair and fall to the ground. If there was no gravity, it would appear in midair and stay there.

Isn't the speed of light = energy, matter can't go the "speed of light" while being matter...?

Now if your train were going .999999c, that's a different story; all of your questions could easily be resolved.

Lets say the train in my example is travelling at .999C. The conducter watching the laser sees the laser travelling ahead of the train at the speed of light. The outside observer should also measure the laser travelling ahead at the speed of light but how can you explain that if the train is travelling just under the speed of light. The outside observer should see the laser beam advancing really slowly not instantly.

Einstein's theory of special relativity says that regardless both the observer and the train driver will see the laser light travelling at the speed of light, regardless of how fast the train goes. If you get your hands on the transformation of velocities formula, (dx/dt)', it should work itself out

Lets say the train in my example is travelling at .999C. The conducter watching the laser sees the laser travelling ahead of the train at the speed of light. The outside observer should also measure the laser travelling ahead at the speed of light but how can you explain that if the train is travelling just under the speed of light. The outside observer should see the laser beam advancing really slowly not instantly.

Why should you say that the train is moving and the guy standing on Earth is not? The guy on the train is incapable of carrying out any experiment to prove that he is in any sort of motion - he could play ping-pong, do jumping jacks, whatever and he would never be able to tell that he is in any sort of motion. He is at rest! He looks out the window and notices that the ground outside is moving past him at .999C. If he shoots a laser out of the front of the train, obviously it wouldn't move slower - he's at rest!

The key to understanding why light is the same in all inertial frames is that light doesn't travel through a medium - it's a fundamental force of the universe that travels through empty space. If the guy on the train honked a horn, the noise would seem to travel slower because he's moving with respect to the medium of sound (air). But consider two astronauts in a complete vacuum of space, moving towards each other at a constant velocity, and one shines a light at the other - why should either astronaut measure a different speed than c? There's no way to prove whether one or the other is "moving" (no such thing as "absolute rest"). The concept of the laws of physics being the same in inertial frames is so important that it even takes precedence over ideas like absolute time/length, or simultaneity.

Yea thats a crazy thought. How fast would the light measure in the opposite direction of the train with the guy on the train measuring it. The train would be travelling away from the light at way more than the speed of light.

No, he'd be moving from the light's point-of-origin, and since light isn't really kinetic like ordinary atomic matter, the light would still have radiated from the origin at the same speed as normal. The observer could not observe or measure it, because he would be, at the speed of light, already too far away from the origin-point of any photon to observe that photon, only the new point of origin, never the originated particles.

Lets say the train in my example is travelling at .999C. The conducter watching the laser sees the laser travelling ahead of the train at the speed of light. The outside observer should also measure the laser travelling ahead at the speed of light but how can you explain that if the train is travelling just under the speed of light. The outside observer should see the laser beam advancing really slowly not instantly.

nah

if you were the observer,
you'd see the train actually shrink in length, along the axis of travel.
you'd see time on a clock on the train pass by slower than on your own watch

but you wouldn't see light travel at a different speed as the conductor sees it travel

of course this assumes observer and train are moving relative to each other but im pretty sure this is implied in the question

But you did make a good choice to pick .999c over c. cause you need infinite energy to bring a massive object to light speed, and that doesn't happen

Not by how Einstein theorized. According to his theory someone travelling at extremely high velocity would age slower than an outside observer. I'm no physicist I have no idea how this works I just read it on that PBS article. I don't even understand how all time supposedly relies on light. I know that light is the energy source for all life on earth and all that shit but whats it got to do with time? If all the suns in the universe burnt out the clock would still tick wouldn't it.

Druidus: Good point that explains light traveling in the opposite direction.

it isn't just light that travels at c, all of the fundamental forces of the universe - electromagnetic force, the weak force, strong force, and gravitational force - all travel at c. it's the speed of fundamental interactions in all inertial frames. because these all travel at constant velocity in inertial frames, one requires a length/time transform inbetween inertial frames. consider again the thought experiment in my last post about the two astronauts in a vacuum - why should either measure light to be different speeds? and if they both measure light to be the same speed, how could they measure time the same way?

it's also worth mentioning that without these interactions (especially electromagnetic interactions) nothing would actually happen in the universe, so of course the speed of these interactions defines time.

dude you guys are nuts. Time doest actually exist, its just the way the human brain perceives the way things change around it. its hard to understand, like really hard.

It kinda does though because lets say nobody believes in time and I set an appointment up with someone and I just say be there. What are the odds of the person being there when I'm there? If we both have clocks and I give him the exact time theres a good chance he'll be there though.

yea but thats what im saying. time is a manmade illusion. like people dont get older their apperance just changes over what your mind believes is time. theres like a book that explains it way better than i could. but i dont remember it tho, when i do i'll post it, then you read it, then you mind goes "holy shit".

This thread blew my mind.

What if you were 1 lightyear away from earth and had a telescope powerful enough to see the people on earth would u see what was happening or what people were doing one year earlier

What if you were 1 lightyear away from earth and had a telescope powerful enough to see the people on earth would u see what was happening or what people were doing one year earlier

1 year earlier. The answer is in "1 lightyear", IIRC a lightyear is where it takes light 1 year to reach you.

This is like peeing in the wind.

You get all pissed off

Actually, if you pee into the wind, you get all pissed on. It's better to be pissed off than pissed on. Therefore, this is better than peeing into the wind.
Oh, And I never got back to explain the cows. Einstein had many dreams involving cows. One where they jump from being shocked by an electric fence and he has a discussion with a farmer about their reflexes.. Another where they are bouncing/running around at the speed of light and one talks to im. Those are the least obscure ones.

Simple answer to your question: Theres not that much train track :)

:D:D:D:D:D:D:D:D:D:

I"m eating some noodles.................................