Question

How long would it take a message sent as radio waves from earth to reach mars when farthest from earth (401 million km apart)?

Answer 1

The radio waves travel at speed of light:

`c=3 \cdot 10^8 m/s`

The distance of Mars from Earth when it is at the farthest point is:

`S=401 mil. km = 4.01 \cdot 10^(11) km`

And since the motion of the radio waves is a uniform motion, we can use the basic relationship between velocity, space and time to find the time the waves take to reach Mars:

`t= (S)/(v)= (4.01 \cdot 10^(11) m)/(3 \cdot 10^8 m/s)=1337 s`