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

If the moon and the Earth are attracted to each other by gravity, Why don't they smash into each other.
I know about perpetual falling like space ships have. But why don't space ships, or the moon fall straight down?

There are two schools of thought.

(1) Normally things in space move in a straight line unless they are attracted by another body, and this is what happens with the moon. The earth pulls the moon with a force governed by the formula F=GmM/r^2, and this causes the moon to accelerate towards earth. The vector product of this acceleration and the moon's velocity mean that the moon describes a circular path around the earth. If the moon went a bit quicker, the balance of forces would mean it moved slightly closer in, and vice versa.

(2) The earth is in fact flat and the moon is suspended on stout elastic from the sky. Aeroplanes fly by hooking onto wires suspended from the clouds, and space travel is an elaborate hoax. Also, things gain weight when burnt due to deposits of phlogiston from the fire.

The first theory is widely accepted by respectable physicists. Judging by their failure to spot the principle of the Infinite Improbability Drive, they rarely look beyond the obvious.

When I fall off a fence, why don't I describe a circular path around the earth?

Because when you're *on* a fence you're doing the same speed the Earth is doing. Once you "fall off" you lose speed and the gravity pulls you into the ground. You're just too close and too light to experience any real rotation (while actually it does happen, it's just too small to be noticed).

Snafu.

Probably because you only have time to say 'bloo...ouch!'

The reason is that the moon has tangential velocity; in other words, as it moves toward the earth it also moves perpendicular to the earth, and these two motions combined result in its circular motion around the earth.

AKA: the 'eternall fall'...that's how geo-synchronous satellites stay in orbit. They fall towards Earth, but Earth rotates away. (there's probably a very scientific term for this, but it's 1am and I really need some sleep).

ok i feel very small and dis.. dis.. disorientated right now, but i don't really know why. It's probably all this techno babel going on right now how do you recomemd i get over it.

Don't worry about it. The one thing you can't afford to have is a sense of perspective.

Not only that, but...

The moon is spiralling away from the Earth at something like a centimeter every year. We will all be killed in the anticlimax that occurs when the moon drifts away.

-N.

i totally agrea. I often feel sometimes that the world does not feel right, everything just seems out of place in a weird sort of way. It could be because i drink to much coke and i can't fall asleep at night, that honestly could be why. But still, i get this sinking feeling that the hole adding up of the situation needs more attention then it gets. If we honestly took out time each day and try figure out why this could be true we would all be alot happier, in a cool kind of way. Although i have just relealized that the world is very big and confusing place full of wide open spaces.

we really are dead right now. this is actually hell right now. and i am satan. free candy for all! Just IM me sometime at [email protected] for free skittles or whatever your little hearts desire.

I think that's just perfectly normal paranoia. Everyone has that.

the whole world is paranoid, back to studying!!!