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Consider the twins paradox with a slight variation:

Twins A and B are in separate space ships both capable of going at the speed of light instantly (i.e. without any acceleration). Both ships are stationary relative to each other in intergalactic space facing in opposite directions. They synchronize their clocks.

Then Twin A sees ship B zooms off to the "right" at the speed of light, and ship B travels a round trip of 8 years. Twin A sees ship B recede away from him at the speed of light (in fact, ship A just disappears).

When ship B returns, Twin B's clock will show he has been gone 8 years. But from Twin B's perspective, it's ship A that zooms off to the "left" at the speed of light, does an 8 light year round trip, and according to Twin A's clock, he has also been gone 8 years.

So they both would agree that one has been away from the other 8 years, and both have aged the same amount of time.

It would seem clocks do not actually run slower as they move closer to the speed of light. So is time dilatation just an illusion?

John Rennie
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Peter
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1 Answers1

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There is no frame of reference that has speed c relative to any other frame of reference. This is well known in Special Relativity.

Thus, if it were the case that either spaceship were at speed c in some frame of reference, there is no "synchronizing clocks", there is no "spaceship A sees..." or "spaceship B sees..." because there is no frame of reference in which spaceship A or B is at rest.

This 'question' follows a common pattern: (1) stipulate something that is impossible according to some theory is the case and then (2) purport to conclude something about the theory such as "time dilation is an illusion".

Alfred Centauri
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