Car traveling away from you and turns the lights on, speed of light

[nitai108]

If a car is traveling towards you and turns on the lights the speed of light would be c, but if the car was traveling away from you and turned the lights on would the speed of light be c or less than c?
I've tried to search this question, but it's not easy to describe in a search engine!

 

[Bloodthunder]

The speed of light is always c. Regardless if the car is moving towards you or moving away from you, even if the car is moving at 99.9999999...% of the speed of light.

 

[nitai108]

The speed of light is always c. Regardless if the car is moving towards you or moving away from you, even if the car is moving at 99.9999999...% of the speed of light.

Because light can only slow down if it passes through objects (such as air or glass) but in the vacuum it's always c, right?

 

[Bloodthunder]

Yeap.

 

[nitai108]

Thanks!

 

[Blibbler]

C is a fundamental constant of the universe and is always measured as having the same value> If your car turns its lights on and moves towards you at near lightspeed then it wil be moving nearly as fast as the light it is emitting and the light will be dramatically blue-shifted as more wave crests reach you per second than if it were standing still relative to you. If it were moving away from you then its light would be red-shifted but in both cases it would be traveling at c.

What this tells us is that neither metres nor seconds are constants, but change according to the Lorentz transform which describes time dilation and spatial contraction due to motion, a fact which is often mis-ascribed to Einstein.