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# I'm moving at 80% of the speed of the light (c=299,792,458 m/s)

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I'm moving at 80% of the speed of the light (c=299,792,458 m/s)

If I keep moving during 10 years, and if I were 24 years old when I started moving, how old would I be when I'll quit moving ?

HINT: THIS IS A TRICKY QUESTION ! The answer isn't 34 ! (that is the special relativity)

EinsteinJr  Apr 29, 2015

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If the 10 years is measured by a clock you take with you then you would think you were 10 years older (namely 34).  However, someone at rest would measure that 10 years as 10/√(1-0.82) years, or 16.67 years, so they might think you were just over 40.

If the 10 years is measured by someone at rest then you would think only 10*√(1-0.82)  years, or 6 years had passed, so you would think of yourself as only 30.

This is all a result of time dilation in special relativity (see the recent film, Interstellar, for a more dramatic demonstration!).

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Alan  Apr 29, 2015
Sort:

#1
+26625
+5

If the 10 years is measured by a clock you take with you then you would think you were 10 years older (namely 34).  However, someone at rest would measure that 10 years as 10/√(1-0.82) years, or 16.67 years, so they might think you were just over 40.

If the 10 years is measured by someone at rest then you would think only 10*√(1-0.82)  years, or 6 years had passed, so you would think of yourself as only 30.

This is all a result of time dilation in special relativity (see the recent film, Interstellar, for a more dramatic demonstration!).

.

Alan  Apr 29, 2015
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Thanks Alan, Special relativity is quite mind boggling.

Is "Interstellar" a really good movie?

Melody  Apr 30, 2015
#3
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You're absolutely right.

EinsteinJr  Apr 30, 2015

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