Is Light's Speed Truly Constant in All Frames of Reference?

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SUMMARY

The discussion centers on the constancy of light's speed in different frames of reference, specifically addressing the misconception that an observer traveling at the speed of light could experience instantaneous travel. It is established that no observer can exist "on the light ray" due to the principles of relativity, as light does not have a rest frame. The conversation emphasizes that while light travels incredibly fast, it is not instantaneous, and this speed is finite as perceived in various inertial frames.

PREREQUISITES
  • Understanding of Einstein's theory of relativity
  • Familiarity with inertial frames of reference
  • Basic knowledge of the speed of light (c)
  • Concept of length contraction in special relativity
NEXT STEPS
  • Research the implications of Einstein's theory of relativity on time dilation
  • Study the concept of inertial frames and their significance in physics
  • Explore the relationship between speed and perception in relativistic physics
  • Investigate the differences between classical and quantum physics perspectives on light
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Students of physics, educators teaching relativity, and anyone interested in the fundamental principles of light and motion in the context of modern physics.

madhumadanan
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Dear PF i am new to this forum .

Just wanted to clear a doubt about relativity.

consider a inertial system on a light ray moving at c . If the light ray has to travel betwwen two points in space won't the observer on the light ray feel that the light has traveled almost instantly form the source to destination because of the length contraction observed . So how can light's speed be finite when it is almost instantaneous!:confused:

just tried to substitue the muon example with a light ray and got confused can anybody clarify that for me
 
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You can't have an observer "on the light ray", this isn't allowed in relativity because light always moves (at the speed of light) in every inertial frame. A light ray doesn't have a rest frame, which is the frame an observer "on the light ray" would have to be in. Hence, no such observer can exist.

madhumadanan said:
So how can light's speed be finite when it is almost instantaneous!

You answered your own question! Light is only "almost" instaneous because it moves very fast compared to our everyday experience.

Also, this is the quantum physics forum. If you have more questions about relativity, you should post in the relativity forum https://www.physicsforums.com/forumdisplay.php?f=70 . You will get a better response there.
 

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