here is a dumb question
 

so, the other day at work, we were sharing riddles and one guy asked this one:

if you fired a gun on the moon, how far would the bullet go.


his answer was nowhere. a gun wont fire on the moon, because you need oxygen for the combustion to take place, and the moon has no atmosphere, thus the gun wont fire.


to which I replied, that if the bullet makes a positive (ie airtight) seal with the shell casing, then the oxygen that is already in there would allow it to fire.


then I got to thinking, does gunpowder require oxygen in order to burn? I know that some elements/chemicals do not, but what about gunpowder?

Well...
 

combustion and burning paper aren't exactly the same thing. Yes paper requires oxygen to burn properly because paper itself doesn't conatin any oxygen.

The fuel used in pistol rounds does contain all the chemicals necessary to burn without external oxygen. When the round actually goes off the pressure inside is greater then the air pressure on the outside. So even if there were oxygen on the outside of the casing it wouldn't be able to enter and assist the powder in burning. So the fuel itself has to be combustible sans the surrounding environments oxygen. If the catridge relied on outside oxygen it would never burn fast enough to properly expel the round.
Yes a pistol would fire on the moon.

Also chemical rockets that space shuttles use rely on the same thing in order to burn in space and in the upper atmosphere. You don't see air intakes on shuttle boosters because the chemical fuel used has the whole package.

[EDIT]
I don't know the chemical reasoning though. Programmer, not physicist...
[/EDIT]

Already answered, but yes, the bullet will fire.

In chemistry terms, gunpowder contains an oxidizer (potassium nitrate or similar) that has oxygen chemically bound. When heated, the oxygen is released and used for the combustion process.

Gunpowder provides it's own oxygen, so it doesn't need any air in order to burn.

So a gun would fire on the moon. Assuming that ultralow temps wouldn't prevent the primer from firing.

The bullet would go as far as it was able to before the moons gravity pulled it back down. If it was going fast enough, it could escape the moons gravity (since there is no air resistance) and continue on into space forever (or until it hit something else).

The problem wouldn't be getting the gun to fire so much as it would be getting the bullet to stop.
If you missed what you were shooting at, it would go into low orbit around the moon.
Possibly even come back to kill you.

combustion of hydrocarbons requires oxygen (dunno the make up of gunpoweder but gasoline is a hydrocarbon). but if you could get past that it would keep going until it reaches our atmosphere and burn up i guess

EXTREMELY unlikely. It requires reams of calculations to get a ballistic object (the Apollo spacecraft) from the moon back to the earth. It also requires midcourse adjustments. The likelihood that you could just fire a gun randomly from the moon and get anywhere near the earth is extremely remote - by the time the bullet intersected earth's orbit (if it even did) the earth wouldn't be where it was when you fired the gun. - after all, the Apollo capsule travelled at 20,000 mph and still took 3 days to get there. A bullet doesn't even fire at 1,000mph ;)

I failed chemistry the first two go-rounds.. maybe I can answer that after the third time.. Third time's a charm, right?

The escape velocity of the moon is 2.37 km/sec. If you shoot towards earth it's a tad smaller at 2.28 km/sec. A typical Desert Eagle .440 has a muzzle velocity of 1600 fps or .487 km/sec. Not enough to escape or orbit. The bullet is coming back.

Don't forget the recoil...

you can get the gunpowder to burn but what about the primer? Will it burn w/out oxygen?

Primers are the same thing, its pressure sensitive explosive material(I think theyre airtight too, not sure on that) They contain enough oxygen to burn.

Desert Eagle .440? Cool. I thought they only made .50 and 9mm.

Sofa ;-)
 

The desert eagle comes in 3 flavors,
.357 magnum, .44 magnum, and .50 Action Express. The 9mm isn't "really" a desert eagle... some silly israeli made it I think. They always buy/make the cruddiest equipment and then go fight wars and win against all odds... it's insane.

Don't forget the Desert Eagle also comes in .41AE. ;)


Edit - And yes It also came in .440 CORBON.

I'm glad to read the posts, answered a question that i never thouhgt of.

well not only would the gun fire, if it didnt freeze over or anything like that but the bullet would travel 6 times farther than on earth because the gravitational pull is what limits bullet travel **** funny experiment you can try to prove this is if you drop a rock, and shoot a gun at the same time... both the bullet and the rock will hit the ground at the same time, just the bullet will travel very far, and the rock will smash your toe