In theory, someone could build a high powered laser on Earth and use it to burn advertisements into the Moonโs surface. Whatโs stopping someone, or is it impossible/illegal?
It’s not impossible, but it is highly impractical. First, a laser like that is not something we could currently build, but if we did it would require absolutely insane amounts of power.
Just as a rough calc, to burn an ad into the moon using a laser that could produce deep and contrasty enough lines to be visible from earth (say something box-shaped and 2,000 miles x 1,000 miles) would require about 10^21 Joules of energy on Earth. Maybe 10^19 of that would reach the moon due to atmospheric absorption and dissipation.
That’s about 277,778 TWh, or around sixty-three years of total U.S. electricity generation. Not even including the cost of the laser itself (which would be hundreds of billions to trillions), that much electricity would run you about $40 trillion in 2026 dollars. US GDP is about $31 trillion per annum.
So that’s why ain’t nobody carving anything on the moon with lasers. It’d likely be cheaper to send astronauts with excavators and such.