Suppose Galileo and his assistant were 1 km apart when Galileo uncovered his lantern to try to measure the speed of light. How long would it have taken the light signal to reach his assistant?

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.