How to Measure the Speed of Light

A man in the 18 hundreds named fiz sent a beam of light further away. So instead of one mile, he sent it five miles. He was trying to measure longer time distance. If you arrange things just right, then light flies through between the teeth,. hits a mirror, comes back and then flies through the next tooth. And this is the way to measure how long it takes light to go there and back if you don't like the rotation speed of your gear.