Hey times three bye times three
There are many theories and measurement for the speed of light. It is believed that light travels at 299,792 km per second. In the earlier day philosopher Aristotle believed that light didn't travel but happens instantaneously. Therefore, for Galileo and his assistant to be only 1km apart, I would have to agree with Aristotle theory of light traveling instantaneously.
I hope this helps.....
Explanation:
I took this in 9th grade so I know how to do this kind of stuff