An amateur scientist directs a radio signal pulse at Mars, which is 1.5 x 10m away at the time. Then, 800 seconds later, while peering through a telescope, she observes an explosion on Mars. Could the explosion somehow have been caused by her act of sending the radio pulse?

No.

Explanation:

A radio wave is an electromagnetic wave and all electromagnetic waves move at the speed of light, 3 * 10^8 m/s.

We can find the time it will take for the signal to get to Mars from Earth:

Time = distance/speed

Time = (1.5 * 10^11)/(3 * 10^8)

Time = 500 secs

Hence, it would be impossible for the explosion (which occurs 300 secs later) to have been caused by her radio signal pulse.

momentum of soft ball three times less than baskey ball