h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Right then, I have always wondered about this question=

The world spins round, so if you fired a rifle straight up into the air, would the bullet land next to you when it came down?

Or would it be a set distance away from you, as the world turned round a bit while the bullet was up in the air??
Smudger,

I suppose if you were stood on the North pole it'd land back in the barrel of the gun, assuming you didn't move the gun, as the pole is the axis on which the planet spins!!

Otherwise, don't know

The bullet would come down next to you.

You are moving due to the rotation of the Earth, but so is the bullet.

Sorry, missed the important bit there.

The air is also moving, due to the rotation of the Earth, and the bullet doesn't move laterally relative to the air. This is why we can be standing on a planet that is rotating very fast (~400mph at the equator I think, but that's half remembered and I can't be bothered to work it out) without experiencing ~400mph winds.

ah but, You are moving with the earth because you are in contact with it. And the rifle is in contact with you and the bullet in contact with the gun.
When the bullet leaves the gun it no longer has any link physical link to the earth. If there was no atmosphere, then the bullet would coninue to travel sideways (in the direction of the earths spin) at the same speed as when it was in the gun. But as it goes higher, it would have to travel further to match pace with the person on the ground. Since there is no external force on it to move it this way, it won't accelerate and thus will land some way behind you.
However, since we have an atmospher which causes friction then when the bullet leaves the gun it will experience this friction causing it to slow down (relative to the spin of the earth) Therefore when it comes back to earth it will be even further behind you.

Mind, if there was a gale blowing at the right speed and in the direction of the erths spin, then it wouldn't.

I saw something like this explained on television once. It doesn't matter where you stand; if you fire a gun into the air and keep the gun in the EXACT same spot, and ignore any outside forces like wind, spin on the bullet, or random birds or airplanes, the bullet will land back in the barrel. It's the same concept as throwing a ball in the air.

ah yes, true, erm.

Oh. I'm thinking on a much smaller scale here. Ictoan would be right if the bullet traveled really really far.

Really, really far would have to be something in excess on 18 miles straight up by which time the atmosphere would be so thin, its effect would be negligible.

The atmosphere exerts a horizontal force on the bullet by virtue of the fact that it is moving at the same speed as the Earths rotation. To have land anywhere else except from where it came from, another horizontal force has be applied to the bullet to counteract that of the atmosphere.

BTW the Earths rotational speed at the Equator is a little over 1000 mph.

Donald

I remember that during WWI, when they had these enormous guns, they had to calculate how far the earth rotated during the time the bullet was in the air, and adjust the aim accordingly. I think this means that the earth does move in relation to an object flung in the air a long way.

Err, I think someone has been exaggerating a bit there. There is no way an artillery shell is going to be effected by the earths rotation. The only natural phenomena that effect artillery is air speed, air pressure and humidity plus the altitude of the weapon firing the shell. Believe me, I spent 22 year sin the Army, ten of those years as a fire controller and the Earths rotation never came into the calculations.

The only weapon that was used in WWII where this might have been a consideration is the V2 rocket.

Donald

Well, possibly, but I was talking about the first World War. The Germans had this artilery piece that was nicknamed 'Big Bertha'. It was used to shell Paris from a distance of up to 120 km.

According to this site: Http://www.wncc.net/courses/aveh/lecture/lecmove.htm
The coriolis effect is the effect of the rotation of the earth on moving bodies. It is only noticeable on large scales, like hurricanes or very long range artillery.

The relatively high arch of the German artillery may be the cause that the coriolis effect is so large. From Encyclopedia Britannica: "Their unprecedented range of 75 mi (121 km) was achieved by sending the shells on a trajectory 12 mi (19 km) into the stratosphere."


(This reminds me of a plan Saddam reportedly had to build a supercannon to shell US cities.)

Hi Folks, Thanks for all your answers,I have read them all, but Im still not sure of correct answer?
I know that NASSA have to calculations when they have to re-enter the earths gravity force when returning to earth.

I knew about "Big Bertha" tha gun that could fire a shell across the Channel

I think the higher the bullet went the less atmospheric pressure would apply to it, even so, would it still land beside you?

I dont think so, but then again, I could be wrong
Smudger,

Please don't try it until you're sure.

Oh ho, so I was right then?
I really can't see how anyone would manage to fire a gun so far that it would in fact go high enough to land behind the person. Of course you could shoot one so far that it entered orbit, in which case there's no knowing where it would come down at all. At least not with some calculation. But for all intents and purposes people should be firing normal guns...or we could simplify it to a bow and arrow. Shooting an arrow would make it come down and hit you in the face. While this may be incredibly funny, it doesn't really mean much in accordance with this conversation.

*decides to stop talking*

Shagrath, We will just put it down to a "dont know" and call it quits

(I was starting to regret ever asking anyway)

I know for a fact that it doesnt work with an Air Rifle, coz I tried it years ago when I was a nipper
Smudger,

Yes, and that's most likely because of spin on the bullet or wind or whatever...

Challenge to someone: Find a way to actually try this out, without any wind or spin on the bullet (like in a large building), and see what happens...now I really want to know too...

Yea! Its bothering me too?
No doubt someone in the future will try it out, yet I dont know how they will manage it

I had just come back form adding more atricles from to my page, when I saw your post (good timing Eh!)

BYW, do you know anyone in the "invention world"?
Just asking, coz an American company I contacted a while ago, are now telling me they want £££££s and heaps of them
Smudger,

In an act of shameless self-promotion... I wrote this entry. A593273

H.

Well done H,
After reading all that, (some times twice to get my brain into gear) I now understnd the answer to my question

I have in fact treid that idea ao the water going down a sink. I did one time when we crossed the equator when I was in the Navy, and the water just went straight down!!
Smudger,