Silly speed of light question..

Silly speed of light question..

Author
Discussion

Dakkon

7,821 posts

215 months

Monday 25th October 2004
quotequote all
You have to consider microwaves as well, they travel at the speed of light, but as they are a wave, at some points they must be travelling faster than light and at other points slower

fish

3,892 posts

244 months

Monday 25th October 2004
quotequote all
Just to spoil the fun. My understnading is as follows;

Nothing odd would happen at all the lights would shine normally. That is because everything is relative. The light from your lights will travel away from the car at light speed as relative to the car lights the car is not moving. When we sit at our desk we say we are stationary, were not, we're traveling through space at thousands of miles an hour, same situation.

Speed is only a relative measure. For all we know we could ie the whole Galaxy be traveling above light speed anyway.

Jnr

483 posts

213 months

Monday 25th October 2004
quotequote all
fish said:
Just to spoil the fun. My understnading is as follows;

Nothing odd would happen at all the lights would shine normally. That is because everything is relative. The light from your lights will travel away from the car at light speed as relative to the car lights the car is not moving. When we sit at our desk we say we are stationary, were not, we're traveling through space at thousands of miles an hour, same situation.

Speed is only a relative measure. For all we know we could ie the whole Galaxy be traveling above light speed anyway.


I agree everything is relative.....

swilly

9,699 posts

236 months

Monday 25th October 2004
quotequote all
Jnr said:

fish said:
Just to spoil the fun. My understnading is as follows;

Nothing odd would happen at all the lights would shine normally. That is because everything is relative. The light from your lights will travel away from the car at light speed as relative to the car lights the car is not moving. When we sit at our desk we say we are stationary, were not, we're traveling through space at thousands of miles an hour, same situation.

Speed is only a relative measure. For all we know we could ie the whole Galaxy be traveling above light speed anyway.



I agree everything is relative.....


No its not. Once the photon is emitted it is independent of the vehicle. Inorder for any light to be seen it would have to accelerate away from the vehicle to the viewer. It would not.

Both the photon and the vehicle will be travelling at light speed, hence there will simply be a build up of photons at/within the head light.

You would not see anything if you could view from the front of the vehicle, as no light would reach you to facillitate your viewing.

The most important question to be asked though is...........

Why the fruck would you want to turn your headlights on a light speed anyway? so you can see where you are going

ATG

17,532 posts

234 months

Monday 25th October 2004
quotequote all
fish said:
Just to spoil the fun. My understnading is as follows;

Nothing odd would happen at all the lights would shine normally. That is because everything is relative. The light from your lights will travel away from the car at light speed as relative to the car lights the car is not moving. When we sit at our desk we say we are stationary, were not, we're traveling through space at thousands of miles an hour, same situation.

Speed is only a relative measure. For all we know we could ie the whole Galaxy be traveling above light speed anyway.


Yup. Exactly. This is the central idea of the relativistic theories. In fact the observation that this is what happens in practice (Mickleson Morley experiment) was the key experiment that got the ball rolling and led Einstein to construct a model of space and time in which anything travelling at the speed of light _always_ appears to be travelling at the speed of light, regardless of the speed at which the observer is travelling.

Alex

9,969 posts

246 months

Monday 25th October 2004
quotequote all
Fish is correct, the speed of light is relative to the observer. Assuming you could travel in a vehicle at the speed of light (you can't), if you turned your lights on, the would appear to work normally from your point of view. That does not mean however, that the light from your headlamps is travelling at twice the speed of light when viewed by an independent observer.

ThatPhilBrettGuy

11,804 posts

202 months

Monday 25th October 2004
quotequote all
I told you all that you'd regret talking about this earlier on but as we still seem to be going...
Jnr said:

I agree everything is relative.....

swilly said:

No its not. Once the photon is emitted it is independent of the vehicle. Inorder for any light to be seen it would have to accelerate away from the vehicle to the viewer. It would not.

Yes it is. You're forgetting (or didn't know about) the time element in all this....
swilly said:

Both the photon and the vehicle will be traveling at light speed, hence there will simply be a build up of photons at/within the head light.

No there won't.

There's just no point in using simple logic to say what's going on, which most people are doing (which is understandable). But it just doesn't work. Look, I'm not having a go at anyone here and it IS an interesting subject, but some basic knowledge of the Theory of Relativity is needed here, and that's going to be generating headaches all round.

Read this http://www2.slac.stanford.edu/vvc/theory/relativity.html with strong coffee available.

Cheers

Phil

MilnerR

8,272 posts

220 months

Monday 25th October 2004
quotequote all
Using relativity arguments while logical is not completely valid. Consider the fact that if you stand in a clear space and spin around at a rate of 1 revolution every two seconds with the moon on the horizon; the moon will be rotating around your head at aproximately 4 times the speed of light. The moon is 385000km away so therefore each orbit around your head the moon is traveling at 1.21 million km/s (relative to your head)! This sounds stupid but according to general relativity all co-ordinate systems are equally valid including revolving ones.
Don't know what this proves other than physicists have to be the most anally retentive pedants on earth!

simpo two

74,341 posts

227 months

Monday 25th October 2004
quotequote all
ThatPhilBrettGuy said:
Read this http://www2.slac.stanford.edu/vvc/theory/relativity.html with strong coffee available.

I would but I'm currently working on a video script which is even harder!
NB The simplest way to travel vast distances at a 'speed' faster than light is to distort gravity so you can simply step to wherever you want to go. It's called warping the space-time continuum.

However I'm still working on the SGA (Simpo Gravitational Accumulator) which will allow me to do it...

ATG

17,532 posts

234 months

Monday 25th October 2004
quotequote all
MilnerR said:
This sounds stupid but according to general relativity all co-ordinate systems are equally valid including revolving ones.

<Anal retraction>It doesn't say that. It says that inertial frameworks aren't fundamental, they are only a useful derivation of the equivalence principle and general covariance. There is still a "special" type of motion even so. It is free fall. Reference frames in free fall become equivalent.<And relax>

havoc

25,447 posts

197 months

Monday 25th October 2004
quotequote all
If you were travelling at EXACTLY the speed of light, you'd be in trouble, because everything in front of you would have blue-shifted into the UV spectrum or beyond, so you'd be blind!!!

It's an unanswerable question at the moment - we can all speculate, but as even noble-prize winning physicists don't KNOW (and certainly don't agree)...

supraman2954

3,241 posts

201 months

Monday 25th October 2004
quotequote all
ThatPhilBrettGuy said:
swilly said:

Both the photon and the vehicle will be traveling at light speed, hence there will simply be a build up of photons at/within the head light.


No there won't.

Correct.
If the driver were to switch on the headlamps whilst travelling at the speed of light, according to a stationary observer at the side of the road, the headlamp switch WOULD STILL BE IN THE OFF POSITION!

if that doesn't confuse you, nothing will

paddym

198 posts

202 months

Monday 25th October 2004
quotequote all
wayne_uk said:
Right,your car is having a nice little trundle along at the speed of light ( trying to keep it car related here.. ) , you turn you lights on..

Does your lights go twice the speed of light,or don't they come on ?,or do they come on,but stay still..ie it the car does 5 mph slower will you see light travelling at 5mph ?


beer...,stop...,now....



All this brain hurting useful info ... and Waynes question is a trick ... your car is having a trundle ... so you are not in it -- so if you can see the car you can see the lights (probaly a TVR as they do have an electrical mind of thier own).

But then if you are in the car and it is a TVR, you may not see your lights but you'll see everybody else's in your rear view mirror

MilnerR

8,272 posts

220 months

Monday 25th October 2004
quotequote all
MilnerR said:
Don't know what this proves other than physicists have to be the most anally retentive pedants on earth!


ATG said:

MilnerR said:
This sounds stupid but according to general relativity all co-ordinate systems are equally valid including revolving ones.


<Anal retraction>It doesn't say that. It says that inertial frameworks aren't fundamental, they are only a useful derivation of the equivalence principle and general covariance. There is still a "special" type of motion even so. It is free fall. Reference frames in free fall become equivalent.<And relax>



QED

Thom

1,700 posts

209 months

Monday 25th October 2004
quotequote all
wayne_uk said:
Does your lights go twice the speed of light,or don't they come on ?,or do they come on,but stay still..ie it the car does 5 mph slower will you see light travelling at 5mph ?


Assuming the only direction of movement is in the length of the car.

If the car moves at the speed of light the light waves coming out of the bulb won't be "moving" at all in function to the car, i.e. it will be dark unless the distance between the driver's eyes and the light bulb is nil.

Now if the car moves faster than the speed of light then the light waves would be kept up by the rear of the light cluster, meaning some refraction could take place, but don't quote me on this

If the car moves a bit slower than the speed of light then you would see the light waves slowly coming out of the light bulbs.

fish

3,892 posts

244 months

Monday 25th October 2004
quotequote all
Just to confuse. Lets not forget all this talk of seeing things is again all relative. If you are travelling at light speed you won't see much as any light source will either be behind you and no light will get to you as relatively it is traveling at the same speed as you. Alternately you could be traveling at light speed relative to me the obeserver in convoy with your own sun traveling at light speed therfore to the traveller everything would appear normal.

Then you can ask well who is travelling at lightspeed, the traveller going right to left at light speed or are you the spectator actually going left to right at light speed and you just don't know it!!

This gets back to the origional it is all relative and for all we know we are already doing light speed, relative to an unknown spectator....

TheLemming

4,319 posts

227 months

Monday 25th October 2004
quotequote all
Been trying to recall the answer to this one, I read one a while back that seemed rather effective.

IIRC doesnt it have something to do with the time dilation experienced as one travels closer and closer to the speed of light?

ATG

17,532 posts

234 months

Monday 25th October 2004
quotequote all
TheLemming said:
Been trying to recall the answer to this one, I read one a while back that seemed rather effective.

IIRC doesnt it have something to do with the time dilation experienced as one travels closer and closer to the speed of light?


You don't experience anything odd. Inside your fast moving car everything is normal. When you look out the window at the people wizzing past you, they seem to be running in slow motion. As far as you are concerned their time is running very slowly.

However, when they watch you drive past them at enormous speed they think your time is running very slowly.

Which is odd.

groucho

12,134 posts

208 months

Monday 25th October 2004
quotequote all
Jnr said:

I agree everything is relative.....


And everybody is your relative.

Grouch.

lazyitus

19,892 posts

228 months

Monday 25th October 2004
quotequote all
IMO the lights would not come on.

They'd have smashed due to the wind rush created travelling at that speed.

The only prevention would be some CIBIE light covers, but then you would'nt see the lights anyway.