SRL Archive - NOTA

So, there's no science board that I can find, so this is the next best place.


Anyway,

As you guys know, if you're say, 1 lightyear away from Earth, everything you see from earth happened 1 year ago.

What do you see if you travel at the speed of light from Earth?



I was riding in the car talking about things like this with my mom and this question popped in my head, and she said to stop talking about that stuff, it makes her head hurt.


So, any ideas guys?

if youre looking at earth while travelling at the speed of light away from earth, it will look as if time is frozen, whereas if youre looking in the direction youre moving, it will be as if time is going much faster than it actually did/is doing because youre catching up with all the visible light thats on its way to earth.

at least thats my opinion

From: bolshak25
if youre looking at earth while travelling at the speed of light away from earth, it will look as if time is frozen, whereas if youre looking in the direction youre moving, it will be as if time is going much faster than it actually did/is doing because youre catching up with all the visible light thats on its way to earth.

at least thats my opinion

So, it'll be like time stopped on earth? (I'm simplifying if alot here, too.)

From: Vinyl Scratch
So, it'll be like time stopped on earth? (I'm simplifying if alot here, too.)

This is a physics question and the answer to your question is a topic called Special Relativity: http://en.wikipedia.org/wiki/Special_relativity

Another interesting topic for you might be: http://en.wikipedia.org/wiki/General_relativity


Before I hurt a brain or two (yours and mines) explaining, I think it'd be easier to just read the above first (Special relativity). I had to learn that in physics class. :l You can see that it's quite a LONG topic..

We also got to watch Lene Hau do her "Slowing down the speed of light" experiment for our quantum physics class. Pretty cool. You should youtube it. It's going to be used in quantum CPU's eventually. Also relates to your question as well.


God.. I feel like such a nerd sometimes :(

From: Vinyl Scratch
So, it'll be like time stopped on earth? (I'm simplifying if alot here, too.)

I think so, yeah. Not that you'd be able to see though, you'd be much too far away ;)

From: Brandon
This is a physics question and the answer to your question is a topic called Special Relativity: http://en.wikipedia.org/wiki/Special_relativity

Another interesting topic for you might be: http://en.wikipedia.org/wiki/General_relativity


Before I hurt a brain or two (yours and mines) explaining, I think it'd be easier to just read the above first (Special relativity). I had to learn that in physics class. :l You can see that it's quite a LONG topic..

We also got to watch Lene Hau do her "Slowing down the speed of light" experiment for our quantum physics class. Pretty cool. You should youtube it. It's going to be used in quantum CPU's eventually. Also relates to your question as well.


God.. I feel like such a nerd sometimes :(

You weren't lying when you said it was a long read. I still haven't gotten through very much, but what I have read is really cool, thanks for sharing these links.

From: BMWxi
I think so, yeah. Not that you'd be able to see though, you'd be much too far away ;)

Well, not if you used a telescope!

i dont know much but here goes.

way i see it, if you are moving at the speed of light, there is light still ahead of you, and light behind you. surely everything would be the same?

Your mom had the right idea. Stop talking about these things, it will end badly for you. I live in a bunker.

It would look quite fancy because of the lorentz contraction.

If a spaceship was traveling near the speed of light, the slower the time will flow inside the spaceship.

If a spaceship was traveling at the speed of light then time in the spaceship would stop altogether.

Although no matter how fast the spaceship is traveling the occupants in the spaceship will never notice that time is slowing down for them.

From: Soviet Union
If a spaceship was traveling near the speed of light, the slower the time will flow inside the spaceship.

If a spaceship was traveling at the speed of light then time in the spaceship would stop altogether.

Although no matter how fast the spaceship is traveling the occupants in the spaceship will never notice that time is slowing down for them.

Another thing to add is that you don't age the same in space as on earth

if YOU travel at the speed of light you will probably see nothing at all, everything is going to quickly. I dunno lol :p

From: Vinyl Scratch
So, there's no science board that I can find, so this is the next best place.


Anyway,

As you guys know, if you're say, 1 lightyear away from Earth, everything you see from earth happened 1 year ago.

What do you see if you travel at the speed of light from Earth?



I was riding in the car talking about things like this with my mom and this question popped in my head, and she said to stop talking about that stuff, it makes her head hurt.


So, any ideas guys?

Yes, the outer edges of the universe actually travel faster than light, because of this, we'll never see them.

So if you have an object A that is not expanding (everything is moving, but lets pretend this isn't) and object B which is moving as fast as light.. and L which is light

A LB

A     LB
A         LB
A             LB

This is how it would appear
if the light, from the object, was going away at the same speed

now if something is going lets say.. 90% of the speed of light

A     LB
A         L B
A                 L     B
A                      L          B
A                      L                    B
A                    L                             B

eventually light is going to start making its way, and get here

the further light gets away from that object, the sooner it will get to us.. because light lets say is as fast as100mph for easy math


if it's going 100 mph -> way, then it'll be stationary in my shitty 2D diagram

if it's going 200mph -> way it's going to keep getting further and further from the object A, and it'll never be seen

if it's going 90Mph -> way that means, that it'll slowly get further from object B, and slowly stop going -> as fast, eventually, it will not be in the gravity of the object B, and it will start going.. 80 mph -> and then 50 mph -> as it gets less and less out of the pull, it'll eventually be going its 'light speed' toward object A which is <- way

From: grats

if it's going 90Mph -> way that means, that it'll slowly get further from object B, and slowly stop going -> as fast, eventually, it will not be in the gravity of the object B, and it will start going.. 80 mph -> and then 50 mph -> as it gets less and less out of the pull, it'll eventually be going its 'light speed' toward object A which is <- way

Wait what? Are you saying that gravity slows down light?

From: Brandon
Wait what? Are you saying that gravity slows down light?

They proved it bends light many years ago

it's in a big field of 'debris' that is moving right.. while it is moving in all directions basically.. so the part that is going left, would naturally go slower than the part that is 'going with the flow'
nom'sayin?

trying to find some huge ted talks or Neil deGrasse Tyson vid I watched about it for like 3 hours

From: grats
They proved it bends light many years ago

it's in a big field of 'debris' that is moving right.. while it is moving in all directions basically.. so the part that is going left, would naturally go slower than the part that is 'going with the flow'
nom'sayin?

trying to find some huge ted talks or Neil deGrasse Tyson vid I watched about it for like 3 hours

:S Light bends/refracts/w.e. but it doesn't slow down due to gravity ever. It has no mass and gravity only acts on objects with mass. It only affects light because it has a momentum. It bends the light because of a warp in space/time. Some crap like that. Well that's as much as I learned :S
Only few things slow it down and one is the Bose-Einstein Condensate.

From: Brandon
:S Light bends/refracts/w.e. but it doesn't slow down due to gravity ever. It has no mass and gravity only acts on objects with mass. It only affects light because it has a momentum. It bends the light because of a warp in space/time. Some crap like that. Well that's as much as I learned :S
Only few things slow it down and one is the Bose-Einstein Condensate.

I will defend this to a point. From what I understand light is never slowed down due to gravity and a high gravity will merely curve it. Bending it towards the source due to a warp in space/time would successfully coincide with how gravity has also been proven to affect time (Ie: higher gravitational pulls cause time to essentially occur slower than lower gravitational pulls).

However, I won't necessarily say that light has no mass either simply because we can't fully prove that it has no mass, merely that it must be below a certain threshold (last number with certainty I'm away of is less than 4*10^-48). Light is simply photons, photons have a certain amount of energy to them and based on how Solar energy works (photons hit the panel and bounce some electrons with the electrons resulting in energy), I would assume that photons actually due have a mass to them (energy implies mass and the ability to affect something with a mass also implies mass).

From: Brandon
:S Light bends/refracts/w.e. but it doesn't slow down due to gravity ever. It has no mass and gravity only acts on objects with mass. It only affects light because it has a momentum. It bends the light because of a warp in space/time. Some crap like that. Well that's as much as I learned :S
Only few things slow it down and one is the Bose-Einstein Condensate.

http://en.wikipedia.org/wiki/Slow_light

first link on google, yea, it can be slowed though

and yea, if you squirt a water gun left while you're traveling 200 miles per hour right, the water isn't go left.. it'll end up right compared to the position of where it was first squirted

I never really said anything about gravity slowing down or doing anything with light in my original post.. I was making a point that everything is expanding away from each other, and the outer edges of the universe expand away from us, faster than the speed of light.. therefore, the light won't reach us

From: Kevin
energy implies mass and the ability to affect something with a mass also implies mass.

No.
I'm sure you're referring to E = MC^2 when you say that energy implies mass. That only applies to objects at rest. We all know that light is never at rest.

The correct equation is: E^2 = (MC^2)^2 + (PC)^2 where P = momentum and M = 0. And you'll see that you can have Energy without mass. So yes light has no mass.

Anything travelling at the speed of light has to have no mass because it'd require an infinite amount of energy. Waves don't have to have mass and they can still affect particles and matter.

From: Kevin
I will defend this to a point. From what I understand light is never slowed down due to gravity and a high gravity will merely curve it. Bending it towards the source due to a warp in space/time would successfully coincide with how gravity has also been proven to affect time (Ie: higher gravitational pulls cause time to essentially occur slower than lower gravitational pulls).

However, I won't necessarily say that light has no mass either simply because we can't fully prove that it has no mass, merely that it must be below a certain threshold (last number with certainty I'm away of is less than 4*10^-48). Light is simply photons, photons have a certain amount of energy to them and based on how Solar energy works (photons hit the panel and bounce some electrons with the electrons resulting in energy), I would assume that photons actually due have a mass to them (energy implies mass and the ability to affect something with a mass also implies mass).

Thanks for sharing out such useful information about photons.. I am studying the nature of photons and will try to gather some more details..

Now since the person above me brought up this old thread, I would like to mention one thing:
Too see, visible light has to pass through the pupil. So if you are traveling away from earth at the speed of light and looking back on earth you wont see anything, it will be pitch black as no light will reach your eyes.

Right?

From: slacky
Now since the person above me brought up this old thread, I would like to mention one thing:
Too see, visible light has to pass through the pupil. So if you are traveling away from earth at the speed of light and looking back on earth you wont see anything, it will be pitch black as no light will reach your eyes.

No. When you are going at the speed of light, light is still going toward and away from you at the speed of light.

From: Wetish
No. When you are going at the speed of light, light is still going toward and away from you at the speed of light.

what about the speed of potatoes?!

From: hoodz
what about the speed of potatoes?!

They tend to stay put until people start pulling them out of the ground. Then they get up to about several hundred potatoes per hour. Then they stop moving again.

From: BMWxi
They tend to stay put until people start pulling them out of the ground. Then they get up to about several hundred potatoes per hour. Then they stop moving again.

that's insane!

From: Wetish
No. When you are going at the speed of light, light is still going toward and away from you at the speed of light.

You are telling me that a speed of light is somehow relative to me/the observer? Hmmk. That sounds very familiar, I think I've read that, some time ago.
- My memory is not what it once was :p

From: Wetish
No. When you are going at the speed of light, light is still going toward and away from you at the speed of light.

That should only be true if you have a light source alongside you. Light moves at the speed of light relative to the source. If you are moving half the speed of light away from a light source, then the light that reflects off of you will only reflect at the remaining half the speed of light, it won't suddenly get a boost in speed.

Edit: You also gain the advantage of seeing everything occur at half-speed relative to the original light source if you're travelling half the light of speed away (assuming you could somehow see that far/long).

From: Kevin
That should only be true if you have a light source alongside you. Light moves at the speed of light relative to the source. If you are moving half the speed of light away from a light source, then the light that reflects off of you will only reflect at the remaining half the speed of light, it won't suddenly get a boost in speed.

Edit: You also gain the advantage of seeing everything occur at half-speed relative to the original light source if you're travelling half the light of speed away (assuming you could somehow see that far/long).

Read up on http://en.wikipedia.org/wiki/Theory_of_relativity#Special_relativity

From: Wetish
Read up on http://en.wikipedia.org/wiki/Theory_of_relativity#Special_relativity

I apologize, my original statement:
That should only be true if you have a light source alongside you. Light moves at the speed of light relative to the source. If you are moving half the speed of light away from a light source, then the light that reflects off of you will only reflect at the remaining half the speed of light, it won't suddenly get a boost in speed.

Should be:
Light moves at the speed of light depending on the material/vacuum it travels through. If you are moving accelerating at half the speed of light away from a light source, then the light that reflects off of you will only reflect at the remaining half the speed of light, it won't suddenly get a boost in speed.

Light is a constant compared to all uniformly moving (non-accelerating) observers.

From: Kevin
If you are accelerating at half the speed of light away from a light source, then the light that reflects off of you will only reflect at the remaining half the speed of light, it won't suddenly get a boost in speed.

This is false. The speed of light is independent of the motion of the observer and the motion of the source of light. Whether you move half the speed of light AWAY from the source doesn't matter. Any light hitting you is still refracted at the speed of light. Not half because you move half..

Could possibly be doppler shifted though (blue light to red light, etc..) But that's the wave length and frequency changing.. not the speed.


Example:

If car 1 moves at 100km/h and a car 2 beside it moves the same velocity in the same direction (speed), then from car 1's point of view, car 2 isn't moving (subtract the velocities).

If car 1 moves at 100km/h and car 2 at half that in the same direction, then from car 1's point of view, car 2 is moving at 50km/h (subtract the velocities).

If car 1 moves at speed of light and car 2 follows behind it at half the speed (car 1 is moving AWAY from car 2 at twice the speed). How fast will car 1 be moving relative to car 2? The answer is the speed of light (even though car 2 is moving at half the speed). Car 1 will still be measure to be moving at the speed of light, from the perspective of car 2 (the following car). You'd expect it to be measured at half but it isn't so..

http://www.youtube.com/watch?v=hOz9L5zC8rg

From: Brandon
This is false. The speed of light is independent of the motion of the observer and the motion of the source of light. Whether you move half the speed of light AWAY from the source doesn't matter. Any light hitting you is still refracted at the speed of light. Not half because you move half..

Example:

If car 1 moves at 100km/h and a car 2 beside it moves the same velocity in the same direction (speed), then from car 1's point of view, car 2 isn't moving (subtract the velocities).

If car 1 moves at 100km/h and car 2 at half that in the same direction, then from car 1's point of view, car 2 is moving at 50km/h (subtract the velocities).

If car 1 moves at speed of light and car 2 follows behind it at half the speed (car 1 is moving AWAY from car 2 at twice the speed). How fast will car 1 be moving relative to car 2? The answer is the speed of light (even though car 2 is moving at half the speed). Car 1 will still be measure to be moving at the speed of light, from the perspective of car 2 (the following car). You'd expect it to be measured at half but it isn't so..

http://www.youtube.com/watch?v=hOz9L5zC8rg

I do not disagree with your example as they follow the laws of Special Relativity - however those models and laws are based on non-accelerating objects. The speed of light as a constant does not apply to accelerating forces, as defined by General Relativity: http://en.wikipedia.org/wiki/General_relativity#Light_deflection_and_gravitational_time_delay.

So far as my understanding of General Relativity goes (which could be wrong), it roughly boils down to the fact that an accelerating object has an increasing gravitational force, causing any given thing (including light) to have a change in speed and direction as it approaches it due to the gravitational forces.

From: Kevin
I do not disagree with your example as they follow the laws of Special Relativity - however those models and laws are based on non-accelerating objects. The speed of light as a constant does not apply to accelerating forces, as defined by General Relativity: http://en.wikipedia.org/wiki/General_relativity#Light_deflection_and_gravitational_time_delay.

So far as my understanding of General Relativity goes (which could be wrong), it roughly boils down to the fact that an accelerating object has an increasing gravitational force, causing any given thing (including light) to have a change in speed and direction as it approaches it due to the gravitational forces.

Which does not apply to your example or mine (afaict). You aren't bending light in any way. Time dilation is for the mass of objects and its effect on space-time dimension (path light travels along) and has nothing to do with you (the observer) being in motion.. Also, the reason it is slower is because it has a longer distance to travel seeing as it's path is no longer linear.


Anyway.. You are measuring locally.

The speed of light is always C for any local measurement made by any observer, regardless of whether the observer is accelerating. From your example, you are the observer and is moving. You aren't measuring the speed of light from the light source to another point B.


Here these guys are arguing the same thing: https://www.physicsforums.com/threads/speed-of-light-in-non-inertial-frames.422341/