# Explained: astronaut's movement causes lunar flag to wave in Apollo 15 footage

#### Antithesis

##### New Member
This popular Joe Rogan video shows a lunar flag wave as an astronaut crosses the screen. Loop of the segment in question:

The key observation is that the flag begins to move before the astronaut crosses in front:

If the flag's movement were the result of an air current caused by an astronaut actor in an earth-based studio, then the flag wouldn't move before the astronaut reaches it.

The flag's behavior is that of static electrical repulsion. The flag is repulsed by the astronaut.

Dragging your feet across a shaggy carpet results in a buildup of static electrical charge, called triboelectric charge. It works best when the air is dry because dry air is a better insulator than humid air. An even better insulator is no air, and an even better shaggy carpet is the surface of the moon:
On the Moon and on Mars, conditions are ideal for triboelectric charging. The soil is drier than desert sand on Earth. That makes it an excellent electrical insulator. Moreover, the soil and most materials used in spacesuits and spacecraft (e.g., aluminized mylar, neoprene-coated nylon, Dacron, urethane-coated nylon, tricot, and stainless steel) are completely unlike each other. When astronauts walk or rovers roll across the ground, their boots or wheels gather electrons as they rub through the gravel and dust. Because the soil is insulating, providing no path to ground, a space suit or rover can build up tremendous triboelectric charge, whose magnitude is yet unknown.
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But in order for the flag to be repulsed by the astronaut, the flag would have to be charged, too. So how did the flag become charged? To address that question, let us begin with this 40-second demonstration (10:40 to 11:20):

1. He rubs the glass rod, generating an electric charge on the rod.
2. He repeatedly touches the balloon, transferring charge to the balloon.
3. He rubs the glass rod again, charging the rod again.
4. The balloon is repelled by the rod.

Compare this to the full video of the astronauts: