Why did the friends start counting when they saw the flash of lightning? Why didn't they calculate the time it took the light to get to them?

At the speed of light, what’s the most time it takes to get between any two points on Earth?

 Use science terms from the dialogue to describe what light and sound have in common.

What can’t sound waves do in the vacuum of space (where there is no air), that light waves can?

Are radio waves more like light waves or sound waves? Explain your answer.