A rocket travels from earth to the moon (distance measured from the earth 384000km) at a speed v = 0.8c.(adsbygoogle = window.adsbygoogle || []).push({});

(i) How long does it the trip take according to an observer on earth?

Just used straightforward Newtonian mechanics,

t = 384000*10^3/(0.8*3*10^8) = 1.6s.

(ii) How long does the trip take according to the astronaut?

Used the lorentz transformation,

t' = \gamma (t - u/c^2 x)

= (0.36)^(-1/2) * (1.6 - 0.8/c^2 * 384000*10^3)

= 0.96s

I believe this part is correct? Now the part I am stuck on is:

(iii) What is the earth-moon distance measured by an astronaut on the rocket?

Could someone please explain to me the principles behind the calculation? I am finding it difficult to get my head around SR!

Many thanks, James.

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# Homework Help: Special relativity problem

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