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

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Discussion Overview

The discussion revolves around the behavior of light emitted from a car moving towards or away from an observer, specifically focusing on whether the speed of light remains constant at c in both scenarios. The scope includes conceptual understanding of light speed in relation to relative motion and implications of relativistic effects.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether the speed of light would be c or less than c when a car traveling away from the observer turns on its lights.
  • Several participants assert that the speed of light is always c, regardless of the car's motion, even at speeds approaching light speed.
  • Another participant elaborates that while the speed of light remains c, the observed frequency of the light changes due to the car's motion, leading to blue-shifting when moving towards the observer and red-shifting when moving away.
  • There is a mention of the Lorentz transform and its implications for measurements of time and space, suggesting that these quantities are not constant but vary with motion.

Areas of Agreement / Disagreement

Participants generally agree that the speed of light remains c regardless of the car's motion. However, there is some debate regarding the implications of this on the observed frequency of light and the interpretation of relativistic effects.

Contextual Notes

Some assumptions about the nature of light and motion may not be fully articulated, and the discussion touches on complex concepts such as time dilation and spatial contraction without resolving the intricacies involved.

Who May Find This Useful

This discussion may be of interest to those exploring concepts in relativity, the behavior of light in different frames of reference, and the implications of motion on observed phenomena.

nitai108
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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!
 
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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.
 
Bloodthunder said:
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?
 
Yeap.
 
Thanks!
 
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.
 

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