Travel Faster than Light? Opposite Direction Objects

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SUMMARY

The discussion centers on the relativistic effects of two objects traveling at nearly the speed of light in opposite directions. It is established that no object can exceed the speed of light, but from the perspective of one object, the other appears to approach at a velocity calculated using the relativistic velocity addition formula: $$u'=\frac {u-v}{1-uv/c^2}$$. This formula demonstrates that while velocities do not add linearly at relativistic speeds, each object perceives itself as stationary, observing the other approaching at near light speed. The discussion clarifies that for everyday speeds, the formula simplifies to Newtonian expectations.

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  • Understanding of special relativity principles
  • Familiarity with the concept of relativistic velocity addition
  • Basic knowledge of the speed of light as a universal constant
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I know that no object can travel faster than the speed of light, but if two objects travel in the opposite direction, both at almost the speed of light, then would one object be traveling faster than the speed of light relative to the other?
 
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Velocities do not add linearly. If the two objects are moving near light speed with respect to you, you will see the distance between them falling at slightly less than 2c. However, each object will condider itself at rest, and see you and the other object approaching at near c (the other object slightly faster than you).

If, in your frame, the two objects are doing velocities u and v then the one doing v will see the other doing $$u'=\frac {u-v}{1-uv/c^2} $$Remember that your objects are going in opposite directions so one has a negative velocity. Note that for everyday speeds, ##uv/c^2## is tiny and the formula above becomes ##u'\simeq u-v##, which is what you expect from Newtonian physics.
 

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