If the moon explodes, would we hear any sound?

Nope... just sounds of impacts from any moon debris....

it would actually depend on HOW the moon exploded, the magnitude, often when asteroids hit earth (say part of the exploding moon) they burn up on re entry, however they create MASSIVE pressure waves as they enter the earths atmosphe. this pressure waves are vibrations just like sound. however often would be so loud they would not be "sound" as would be measured like earthquakes on the rector scale

You know the answer - you just told us there is no air between the Earth and the moon, and you just told us that sound needs air.

No. We do have an atmosphere through which sound can travel in our atmosphere, but from the outer edges of the atmosphere to the Moon there are no air particles, so sound would not be emitted.

You'll have to tune in to FM 107.1 for surround sound stereo simulcast.

Of course you won't be able to hear through a vacuum. But you may feel Earthquakes from changing tidal forces or electrophonic sounds and sonic booms from debris entering Earth's atmosphere.

Normally no.

It depends, though, on how you plan to cause the explosion.

One could imagine a scenario where, from your secret hide-out from where you want to rule the world, you use a secret weapon that vaporizes the Moon using some sophisticated "magnetic ray". The strong magnetic disturbance could disprupt the Earth's ionosphere in such a way that it generates a compression wave in the atmosphere, which would be perceived as a sound. Since that sound would (more or less) match the visual disappearance of the Moon, the people would say that they "heard the explosion of the Moon" and would, presumably, pressure their political leaders to pay you the ransom you asked for.

In real life, the compression waves caused by the explosion would never reach Earth: no medium to carry them... unless the vaporization is so complete -- all the Moon's matter turns into a gas that expands rapidly due to the explosion -- that gasses expanding from the explosion contact the Earth's atmosphere just as the compression waves are still traveling within the gasses.

This would require quite an explosion and the sound would arrive well after the first chunks enter the atmosphere and bombard us to death.

No we wouldn't hear it. Of course the lumps of rock hurtling towards us part burning up in atmosphere and exploding on imact with the ground would definitely make a sound.

There is no air, but there is a very thin gas. Ultra-low frequency sounds might be generated in that, but their coupling into Earth's atmosphere would be very poor, because of the high energy of particles up there. Sort of like trying to hear a very quiet sound over the sound of wind or waves.

We *would* be able to hear sounds from any pieces of the Moon that reached Earth's atmosphere (and there would be many, if the moon broke up in some kind of catastrophe or explosion). Those sounds would be sonic booms and hissing etc from pieces in the atmosphere and explosion/shock wave/earthquake sounds from pieces reaching the surface.

You'd have to postulate a mechanism, energy source, distribution of debris by size and velocity, etc to make any more detailed calculations of interactions. For instance, a relatively low energy explosion might leave a great deal of rubble more or less in the Moon's orbit or in eccentric orbit around Earth, while a high-energy event might blast stuff every which way, with some significant amount reaching Earth or having secondary collisions in orbit with bits and pieces raining down.

Edit: BTW, all the Star-Wars-like pictures you might have in your mind are *way* off. Think about the size of a planet. Anything blasted away from a planet or moon so that it *looks* like an explosion is going to be moving thousands of kilometers a second... very unlikely scenario. In a real major collision, everything will look like it's in slow motion from here on Earth. Something that takes 10 seconds to move the diameter of the Moon away from the Moon in a collision is moving 350 km per second.

Yes, when the shock wave hits the earth. The shock wave would be bits of rock and dust. Even though vibrations don't become "sound" until they strike the eardrum, the vibrations can come from anywhere. For example, when you hear yourself talk, the vibrations are going from your vocal chords through your bones to your ears. If you're underwater you can hear sounds from vibrations that passed mostly through water. In this case the rock and dust would produce vibrations when they hit earth's atmosphere. It would probably sound like a million volcanoes going off at the same time.

Of course the space between the Earth and Moon is filled with interplanetary gas in the form of the solar wind. The solar wind can and does transmit low-frequency sound waves (longer wavelength than the mean-free-path for atoms). So there would be sound, but it would be below the threshold of hearing for humans (infrasound).

No, we wouldn't hear anything.

Physically, sound is just a deviation in density. You also don't necessarily need air (or any other gas) to propagate sound - any other material (e.g. such as rock or steel) would do, too.

Regards,
Michael.