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

Ok, imagine you're in ancient egypt, watching the slaves push a block of stone up to a pyramid, why do they have to keep taking the roller away from the back of the block, and running round to the front with it?

The answers simple, as the roller rotates, it moves forward, a roller with a circumference of 2 feet will move forward two feet for every full rotation.

The block on top however is another thing, if you imagine that the roller is moving in an anticlockwise direction from your viewpoint, that means that it's moving from right to left as you are looking at it, however, if you look at the point at the very top of the roller, it's pushing the block forwards, in the same way as the bottom of the block is pushing the ground backwards.

The earth can't exactly move backwards, (unless the mass of the roller is a reasonable percentage of the mass of the earth, so the roller must move forward over the ground (2ft), the block on the top of the roller is being pushed forward by the movement of the roller itself, so it moves another 2ft forward in comparison with the roller, thus moving 4 ft in comparison with the ground.

Clear as mud isn't it

whisky

Oh, um...almost...oh yeah, I think I see, now how the hell did I get that answer?

Well you need the point anyway because you knew what your brain was doing, mine did a jump and didn't tell me why!

Whisky hinted at another possibility.
If the block is realy very large, the situation reverses. In that case the earth is rolled over the block, and the block does not move at all. So I say 0 feet.

.... true, but you are then talking one verrrrry big block

Sure, sun-size or something like that.

or 2 inches square, but made out of the same stuff neutron stars are made of, that should just about do the trick.

If the block is only 2 inches square, you'll need very small rollers. You won't be able to transfer a 2 inch block weighing thousands of tons smoothly from the top of one roller to the top of the next if the rollers have a circumference of 2 feet like Greebo said.

Wouldn't the high local gravitational field have a somewhat detrimental effect on the locks cylindrical shape?

Wouldn't the high local gravitational field have a somewhat detrimental effect on the logs cylindrical shape?

Yet another typo induced DP

, not to mention the effect it would have on the poor guy trying to push it.... In fact it would only work if he was flying, with power supplied by some kind of reactionless drive system.




Are we getting a little carried away here

Of course we are.
But he can be standing on the block, pushing the earth. Sort of Atlas or a big Sisyphus. In the last case, the earth does not come rolling back once in a while (I hope)

He/sh/it'll need pointshoes to stand in a 2 inch surface.


Dancer

Not really, standing on a two inch cube chunk of neutron star material would very quickly leave you spread around it, about one atom thick, and very dense.... (Well some of us are pretty dense to start with I know).... It could end up rather messy

Well done Whisky... you deserve this point... not only for getting it right with 4 feet... but.. for the outragously long explanation... ~grin~

Dancer

Well done...