Two astronauts are standing on the surface of the Moon. Astronaut A claps their hands together loudly while Astronaut B watches from 5 metres away. Astronaut B will:

Answer: B. See the action of clapping instantly but will not hear the sound at all because sound requires a material medium to travel.

Sound is a mechanical wave, meaning it absolutely requires a material medium (like solid, liquid, or gas) to travel through because it relies on particles vibrating against each other. Since the Moon has no atmosphere (a vacuum), sound cannot propagate, meaning the astronauts cannot hear each other. Light, however, is an electromagnetic wave and travels effortlessly through a vacuum. Therefore, the astronaut will see the physical clap immediately but hear nothing.

Answering after opening this box earns no Practice Points.