00:00The mirrors on the moon. Let's start with what are arguably the most elegant pieces of evidence in
00:05spaceflight history, the lunar laser ranging retro reflectors. During the Apollo 11, 14 and 15
00:14missions, special mirror arrays were placed on the lunar surface. No electronics or power supply,
00:21just precisely aligned glass prisms. Their purpose is simple and brutally honest.
00:28You fire a laser pulse from earth to the moon. It hits the mirror and bounces back.
00:34The travel time is measured. Light travels there and back at the speed of light.
00:40The result? The earth-moon distance can still be determined to the millimeter to this day.
00:47And you can do that from home. Not even NASA exclusive. These measurements are carried out
00:53by observatories worldwide. In the US, in Europe, in Japan.
00:57Do it for 10 years
00:58I will show you more and be able直接 around the moon.
00:58Do it for those kinds of objects.
01:03Let's start with it.
