(1)what keeps the earth spinning?
(2) is the fuel that keeps the earth fire burning below coming from the stored sun energy in plants and animals that have died .
(1) What would make it stop spinning? There’s no friction with space. The only thing slowing it down is the tidal force from the sun, and that’s pretty weak. Semi-related column:
What happens if the earth stops spinning?
(2) Huh?
(2) No. The “earth fire” is kept going by radioactive decay.
-
rotational inertia. An object in motion stays in motion unless acted on by another force. As Wikkit said, there is no other force. Or not much, at least.
-
3 sources of the heat inside the earth (note that it’s not “fire”, which implies a chemical process where something is burning)
from http://www.sciam.com/askexpert/geology/geology7/geology7.html
Not to forget the tidal effects of the moon as well.
Which is a greater force than tidal effects of the sun. IIRC, Astronomers estimate that when the Earth formed, a day was about 10 to 12 hours long.
Centuries ago, religious thinkers imagined that invisible angels kept the earth spinning. But they suffered from a misconception. They assumed that all spinning objects would naturally stop… therefore, whenever an object keeps spinning, something must be doing it. Wrong!
In fact, the rule is actually backwards: objects will keep spinning forever unless something stops them. The Earth is hovering in space, so there’s little to slow it down.
Today we think when the Earth formed, the incoming rocks weren’t just moving inwards. Instead they spiralled inwards, so they made the big blobby Earth spin as well.
As for #2, if it was decaying plants keeping things warm, then the hottest part would be just under the ground. We know that the center of the Earth is far hotter than the surface (the iron core is molten, except for the very center.)
Back around 1900 geologists thought that the Earth had been red hot when it first formed, and that it was cooling ever since. Decades later they found that this couldn’t be right, because the Earth is so old that the whole thing should have cooled off long ago. Today we know that the slight radioactivity of the rocks is generating heat. The heat has to travel through thousands of miles of rock before it can escape. Just a tiny, continuous amount of radioactive heating is enough to keep the center of the Earth red hot. (If the Sun suddenly went dark, the Earth’s surface wouldn’t cool to absolute zero. If I recall, I think it would hover around 10F on average.)
So is the iron core spinning at exactly the same rate as the crust? Do the tidal forces affect one or the other more?
The liquid parts are not moving uniformly, and in fact aren’t even simply rotating. The motion of the core is mostly what causes the magnetic field of the planet.
No.
The geologists thought that the Earth was old, based upon their studies and observed rates, but Kelvin estimated that the Earth couldn’t be that old–because of the high rate of heat loss at the surface. It would have cooled completely in a few million years. It turned out that radioactive elements are concentrated in the crust, and the heat loss from the interior is not as high as Kelvin thought it was. But most of the radioactive heating is near the surface.
Most of the deep internal heat is from energy left over from the formation of the Earth. There is some energy released as the inner core grows, also–I’m not sure why that Sciam link doesn’t mention that, it’s different from the frictional heating.