Two astronauts standing on the surface of the Moon cannot hear each other's voice directly even if they yell…
Two astronauts standing on the surface of the Moon cannot hear each other's voice directly even if they yell loudly. What is the primary reason for this?
The temperature on the Moon is too low for sound to travel
The gravity on the Moon is weaker than on Earth
There is no air or atmosphere on the Moon to propagate sound
Their space suits absorb all sound vibrations instantly
Solution
Sound requires a material medium (solid, liquid, or gas) to travel. Because the Moon has no atmosphere (vacuum), sound waves cannot propagate through the space between astronauts.