The gestation period of elephants is 630 days (21 months). Suppose we place a fr

Question

The gestation period of elephants is 630 days (21 months). Suppose we place a freshly impregnated elephant on a spaceship and launch it with speed v = 0.6c away from Earth.

a) at what distance from Earth (in the Earth Frame) will the elephant give birth? You can leave your answer in units of light days.

b)You monitor the elephant via radio (i.e. light signals sent from the spaceship back to earth). What time (in days) after launch will we hear the newborn calf?

c) If radio signals are sent from the spacecraft with a period of once per day, how frequently are they recieved on Earth? At what time do you recieve the 630th signal?

Explanation / Answer

a)T' = T/sqrt(1-v2/c2);

=T/sqrt(1-.36)

=T/sqrt(.64)

=T/.8

So, actual time = 630/.8 =787.5 days

So. distance = 0.6c * 787.5 *24*3600 m =.6 *787.5 =472.5 light days

b)Time = 787.5 days (calculated above )

c)24 hrs in space time is 24/.8 hrs in earth time = 30 hrs;

So, it is sent once in every 30 hours,

So, 630 th day call is sent after 18900 hrs

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