is light speed same allways

[agachak]

light speed is same allways right?light never goes faster then other light it is allways same so there is only one light that can be measured and its allways same speed and is evryhwhere its concept and realaty is constant

[elfmotat]

Locally, yes, it's always the same. However if you make your measurements over a large region of spacetime that is significantly curved, you may find that the measured speed of light will differ from the constant c.

[swansont]

Or if you are in a rotating frame of reference, you will get a different answer for c.

[ajb]

Or if you are in a rotating frame of reference, you will get a different answer for c.

 

 

Yes, so even in special relativity you can pick non-inertial frames and these will almost never give you the speed of light to be c.

[Cassandre]

light speed is same allways right?light never goes faster then other light it is allways same so there is only one light that can be measured and its allways same speed and is evryhwhere its concept and realaty is constant

To add a little to the comments of others, what you say is too general - even impossible.

At constant gravitational potential and relative to an inertial reference system, the return speed of light that is bounced off a mirror is always measured as c, independent of the motion of the source. And if we use the "Einstein synchronisation method" then this is also true for one-way light rays. For details see §1 of http://www.fourmilab.ch/etexts/einstein/specrel/www/

[Ophiolite]

I just wonder why people are obsessed with the speed of light, yet pay scant regard to the mass of the tau neutrino. Poor childhood diet?

[Cassandre]

I just wonder why people are obsessed with the speed of light, yet pay scant regard to the mass of the tau neutrino. Poor childhood diet?

Don't you wonder why people pay scant regard to the Lampyris noctiluca?

Everyone deals with light, few people encounter neutrinos (but sometimes glow worms).

[swansont]

Don't you wonder why people pay scant regard to the Lampyris noctiluca?

Everyone deals with light, few people encounter neutrinos (but sometimes glow worms).

 

On the contrary, people encounter neutrinos every day. They just ignore them. Weak.

[Cassandre]

On the contrary, people encounter neutrinos every day. They just ignore them. Weak.

Good one! Indeed I should have written "deal with", "experience" or "see".

[elfmotat]

Or if you are in a rotating frame of reference, you will get a different answer for c.

 

Right. If you were to set up a ring of photon detectors of radius [math]R[/math] around a (cylindrical) mirror, give the ring some angular velocity [math]\omega[/math], emit a photon towards the center and time how long it takes for the light to return to the ring, then you would measure the observed speed of light to be:

 

[math]c_{obs}=\frac{c}{\sqrt{1-(\omega R)^2/c^2}}[/math]

 

EDIT: I forgot to point out that the clock has to be moving with the ring. That's pretty much implied by "in a rotating frame of reference," but the distinction is important enough to be pointed out.

Edited February 19, 2013 by elfmotat