Reply to: 'Ere, where's the elephant then?

[SpontaneousOrder]

No, because gravity per se wouldn't do it if the earth had a fully solid crust

Not true. Tidal forces don't actually refer to tides - they just cause tides where the body being acted on isn't solid.
Two ball bearings in similar orbits in space would experience the same kind of tidal acceleration.

Whether actual tides increase the effect or not I'm not sure (although I would expect that it would have no positive effect - if anything a negative one). So I'm going to upgrade my 'sort of' to a 'mostly' at the very least :P

[Gibbon]

So when you say 'sort of' you mean 'yes - absolutely'.

No, because gravity per se wouldn't do it if the earth had a fully solid crust i.e. there would be no tidal drag, hence sort of.

[GlenW]

I'm not sure that flies' arseholes are located to the rear.

They're definitely not further forward than their head though.

[SpontaneousOrder]

That's due to gravity of other celestial bodies, which I don't think is what he was getting at

Sort of, it's mainly the moon, the sun has the tiniest effect. The moon's gravity causes the tide whose bulge causes the sphere's energy to dissipate through friction. This slowing down also decreases the gravitional pull of the earth on the moon so the moon is also slowly drifting away. When an earth day is as long as a lunar month (see note) there will be an equilibrium and no more tides, but that is billions of years away.

Note:- this is presently observerable, the ancients wisely named Monday after the moon as it seems to last as long as a lunar month.

So when you say 'sort of' you mean 'yes - absolutely'.

[VectraMan]

If you go round a roundabout with a helium balloon on a string, will it go out or in?

I put helium in my tyres as that makes the car lighter, and therefore can go round roundabouts faster.

[SpontaneousOrder]

And the last thing that goes through the fly's mind is its arsehole.

I'm not sure that flies' arseholes are located to the rear.

[tomtomagain]

Wrong !
If you are doing 60mph in a car and a fly is doing 1 mph in the opposite direction
the fly hits the windscreen.

Great. So now I've got to find a fly from somewhere.

Wrong !
The fly goes from 1 mph in one direction to 60 mph in the other, therefore at some point it is doing 0 mph.

That's at the moment it hits the windscreen, therefore at that moment the car is also doing 0 mph.

The car doesn't slow to zero. It slows down slightly as it absorbs the mass of the fly.

But because the car is more massive than the fly the car wins.

Now if you could find a car-sized fly from somewhere .....


I think this is just a re-wording of Zeno's paradox.

[Gibbon]

That's due to gravity of other celestial bodies, which I don't think is what he was getting at.

Sort of, it's mainly the moon, the sun has the tiniest effect. The moon's gravity causes the tide whose bulge causes the sphere's energy to dissipate through friction. This slowing down also decreases the gravitional pull of the earth on the moon so the moon is also slowly drifting away. When an earth day is as long as a lunar month (see note) there will be an equilibrium and no more tides, but that is billions of years away.

Note:- this is presently observerable, the ancients wisely named Monday after the moon as it seems to last as long as a lunar month.

[GlenW]

Wrong !

If you are doing 60mph in a car and a fly is doing 1 mph in the opposite direction
the fly hits the windscreen.
The fly goes from 1 mph in one direction to 60 mph in the other, therefore at some point it is doing 0 mph.

That's at the moment it hits the windscreen, therefore at that moment the car is also doing 0 mph.

And the last thing that goes through the fly's mind is its arsehole.

[EternalOptimist]

The same reason that if you drop a ball in a car that is travelling at 60 miles per hour it doesn't immediately fly to the back of the car and smash your window. Or if you jump up in the train a bit too fast you don't end up mashed on the wall behind you.

The ball is travelling at 60 miles per hour in the direction of the car. If it's dropped ... it's still travelling at 60MPH in the direction of the car ... so it lands on the same spot inside the car.

It's basic physics init

Wrong !

If you are doing 60mph in a car and a fly is doing 1 mph in the opposite direction
the fly hits the windscreen.
The fly goes from 1 mph in one direction to 60 mph in the other, therefore at some point it is doing 0 mph.

That's at the moment it hits the windscreen, therefore at that moment the car is also doing 0 mph.

[GlenW]

The good thing about "science" as opposed to "fairy-tales" is that you can test it.

I'm going to the nearest roundabout in the car with the kids and a ball.

I shall report back.

PS If you see a report in the news about some idiot killing himself in a car with a ball trying to prove that the Earth spins round just remember this: I died in the name of science.

If you go round a roundabout with a helium balloon on a string, will it go out or in?

[tomtomagain]

Except your car and train are travelling at constant speed. If you drop a ball in a car that's doing some hard cornering, the ball will fly sideways and smash your window. And as the earth spins we're all doing hard cornering.

The good thing about "science" as opposed to "fairy-tales" is that you can test it.

I'm going to the nearest roundabout in the car with the kids and a ball.

I shall report back.

PS If you see a report in the news about some idiot killing himself in a car with a ball trying to prove that the Earth spins round just remember this: I died in the name of science.

[SpontaneousOrder]

And as the earth spins we're all doing hard cornering.

No, we're not. Someone earlier said we're doing about 1000kph (as far as rotation is concerned). That's about 130 meters in a half second jump. How far do you think a 130 meter horizon drops?!!

[VectraMan]

The same reason that if you drop a ball in a car that is travelling at 60 miles per hour it doesn't immediately fly to the back of the car and smash your window. Or if you jump up in the train a bit too fast you don't end up mashed on the wall behind you.

The ball is travelling at 60 miles per hour in the direction of the car. If it's dropped ... it's still travelling at 60MPH in the direction of the car ... so it lands on the same spot inside the car.

It's basic physics init

Except your car and train are travelling at constant speed. If you drop a ball in a car that's doing some hard cornering, the ball will fly sideways and smash your window. And as the earth spins we're all doing hard cornering.

[tomtomagain]

If you jump in the air, why doesn't the earth revolve under you and you land in a different place?

The same reason that if you drop a ball in a car that is travelling at 60 miles per hour it doesn't immediately fly to the back of the car and smash your window. Or if you jump up in the train a bit too fast you don't end up mashed on the wall behind you.

The ball is travelling at 60 miles per hour in the direction of the car. If it's dropped ... it's still travelling at 60MPH in the direction of the car ... so it lands on the same spot inside the car.

It's basic physics init