Having a Blast On the Moon

Chesterton said:

Just a trivial question: If you can stand on the moon and not hear a person right next to you speaking because there's no air, could you also stand right next to a large explosion and not feel any blast wave (if "blast wave" is the right term)? (And hypothetically disregarding shrapnel.)

Click to expand...

If enough energy was released, it could knock you down --- or worse.

There's a Twilight Zone episode where Burgess Meredeth goes inside of a bank vault, and while he's in there, an atom bomb goes off nearby.

The first thing that happens, from his perspective, is the lights flicker, followed by a book sliding across the floor, then the book opens and pages flip, then he hears a blast.

Two things, I think:

1) You'd feel the vibrations thru the ground. So, yes, you'd notice it. And, it would likely be significant.

2) While space is essentially a void, it is not 100% void. A large enough explosion would perhaps impel particles such that you could hypotehtically detect the explosion because of those particles. However, such an explosion would probably also be so large that the other effects would overwhelm any minimal resulting "blast wave".

However, I'm no physicist...

Chesterton said:

Just a trivial question: If you can stand on the moon and not hear a person right next to you speaking because there's no air, could you also stand right next to a large explosion and not feel any blast wave (if "blast wave" is the right term)? (And hypothetically disregarding shrapnel.)

Click to expand...

No, because the blast would propel matter at you: besides shrapnel (the casing of the explosive), the actual explosion itself is made of matter, and it would expand outward. That's what an explosion is: the rapid decompression of a dense interior into a less dense exterior.

You could also think of it as the explosion creating a sort of temporary atmosphere through which the shockwave travels.

Chesterton said:

What matter is the explosion made of?

Click to expand...

Most explosions we see are as far as I know; rapidly expanding gases.

Many explosions require oxygen so that might be a problem on the moon, however I think certain explosive substances also have their own component that adds ogygen to the process when ignited as to help it burn better. Sort of.
Someone with more knowledge on the subject could probably clarify this better.

Another question: I'm on the moon and I turn on an electric fan. If I put a feather in front of the fan, would the feather move at all?

Click to expand...

I would have to say no.
The Moon does have some atmosphere but it's extremely thin.

- Ectezus

Chesterton said:

What matter is the explosion made of?

Click to expand...

Depends on what the explosive is made of; TNT and nuclear fission both release different products. But they both release expel matter.

Chesterton said:

Another question: I'm on the moon and I turn on an electric fan. If I put a feather in front of the fan, would the feather move at all?

Click to expand...

No: fans work by creating a pressure gradient, thereby causing air to flow from the back to the front. Since there is no air, there can be no air flow. Since there is no air flow, the feather won't move.

Unless, of course, you dropped it. Then it would fall to the ground as fast as a cannon ball (thank you, Galileo).
But with no atmosphere, the fan doesn't do anything.

So to sum up the difference:
A fan tries to use air to create an effect, but since there is no air, there is no effect.
But an explosion doesn't use the non-present air, it creates its own effect by expanding the gases in the explosion device itself which can propagate without air and thus still reach/hurt you. (No shockwave because of the blast though, just the radius of the expanding gases and heat I think)

There will be a difference in explosions compared here on Earth of course.
I would assume no mushroomcloud effects since the hot air won't try to get up without an atmosphere?
What about a nuclear explosion in space for example. It's never been done before but I would assume that it's a perfect spherical explosion where the giant 'ball of fire' stays in the center rather than going up (and of course no sucking up debris).

- Ectezus

Chesterton said:

Wow, that's weird to visualize.

Click to expand...

It's even weirder to see-
YouTube - Feather & Hammer Drop on Moon

On earth, if you fire a bullet from, say, a .44 Magnum* --- while at the same time dropping, say, a penny from your other hand --- both will hit the ground at the same time.

* Parallel to the earth.

AV1611VET said:

On earth, if you fire a bullet from, say, a .44 Magnum* --- while at the same time dropping, say, a penny from your other hand --- both will hit the ground at the same time.

* Perpendicular to the earth.

Click to expand...

For a second there I thought you mean perpendicular to the surface of the Earth (that is, straight up). Hopefully you mean something like 'towards the horizon'...

Wiccan_Child said:

For a second there I thought you mean perpendicular to the surface of the Earth (that is, straight up). Hopefully you mean something like 'towards the horizon'...

Click to expand...

--- oops!

corvus_corax said:

It's even weirder to see-
YouTube - Feather & Hammer Drop on Moon

Click to expand...

im disgusted at those that continue this moon Hoax, it is clear that they are in a specially created sound stage that has been set up with a vacuum.