alt Hacker NewsFrom TFA:
> 2.43 kilometers a second, or 1.51 miles a second, or 5,400 miles an hour, or 8,700 kilometers an hour.
> There is, of course, no air and no sound on the Moon, so a "Mach number" doesn't really make sense. But if there were air, the speed would be about Mach 7, seven times the speed of sound.
Replies
SecretDreams • today at 1:26 AM
How many Machs is the earth moving?
"If there were air". Air at which temperature though? Th sound of speed, and hence what Mach numbers mean, depends on the temperature of the air. The temperature air would have at the moon's surface? By day or by night? Or the air at Earth's surface? Or at some other altitude?