If an atomic bomb were detonated on the surface of the moon, how long would it be until we heard the explosion on Earth?

The detonation would not be heard on Earth, therefore we would wait infinitely for it.

This is because the sound is a mechanical wave, whose main characteristic is that it necessarily needs a medium to propagate; unlike electromagnetic waves that can propagate in vacuum.

After knowing this, we add the fact that the space that separates the Earth and the Moon is the vacuum, therefore, if an atomic bomb were detonated on the surface of the moon, this would not be heard on Earth.