Light Speed Separation: How Long?

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SUMMARY

The discussion centers on the impossibility of two objects moving away from each other at the speed of light and the implications for light travel time between them. It is established that no object can reach or exceed the speed of light, making the original question unanswerable in its literal form. If the objects are moving slightly below the speed of light, the time for light to travel between them can be calculated, but requires specific details about their speeds and initial distance.

PREREQUISITES
  • Understanding of Einstein's theory of relativity
  • Knowledge of the speed of light as a universal constant
  • Familiarity with basic physics concepts of motion and distance
  • Ability to apply mathematical principles to calculate time and distance
NEXT STEPS
  • Research Einstein's theory of relativity and its implications on speed limits in the universe
  • Study the concept of light speed and its effects on time dilation
  • Learn about relativistic velocity addition for objects moving near the speed of light
  • Explore mathematical models for calculating light travel time in varying conditions
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Students of physics, educators teaching relativity, and anyone interested in the fundamental principles of motion and light in the universe.

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If two objects move away from each other in opposite colinear directions at the speed of light. How long will it take for the light from one of the objects to reach the other?

I think the answer is never, but not sure.
 
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If you mean that each object is moving at exactly the speed of light, then your question starts out with a impossible situation, because nothing can travel at the speed of light (except light itself, of course). There is no way to answer this question in its literal form.

If each object is moving very slightly slower than the speed of light, then an answer is possible in principle, but you don't provide enough information to calculate it. The time it takes for light to travel from one object to the other depends on the speeds of both objects, and on how far apart they are when the first object emits the light.
 

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