How is earths tilt maintained?

Answer 1

In the short term, nothing changes the Earth's tilt much.

The Earth's tilt is fixed at about 23.5 degrees, except for very small variations.

Earthquakes and other things can have minute effects.

However, scientists believe that the tilt does change by a degree or more, over millions of years. These changes are because of the effects of gravitation within the solar system.

The ecliptic is the plane of the Earth's orbit around the Sun. The orbital planes of most of the other planets are fairly close to the ecliptic; that's probably because our solar system was formed from a rotating disk of gas and dust when gravity caused it to collapse. We would expect some differences, but probably not great differences, in this "accretion" model.

Each of the planets spin on their axes. The spin speed and the axis of spin were determined when the planets formed, or shortly thereafter. One thing that might change the spin axis of a planet would be if it collided with another planet or nearly-planet-sized body. If the collision weren't perfectly "head on", then there would be some, perhaps a LOT, of spin imparted to the combined body. It may be coincidence, but we believe that the pre-Earth collided with another planet perhaps nearly the size of Mars shortly after the formation of the solar system. The planetary cores would have merged, and we believe that much of the mass blasted off the Earth might have coalesced to form the Moon. This would explain the unusually large iron core of the Earth as opposed to other planets, the existence of the Moon, and might have contributed to the direction and speed of the Earth's rotation.

For the last 4+ billion years, the only thing affecting the Earth's spin has been the gravitational and tidal interactions with the Moon. The Earth's rotation is slowing down, VERY slightly; in a few (hundred?) million years, the day may be 25 hours long. The rotational energy of the spinning Earth is being transferred, EVER so slowly, to the orbital altitude of the Moon. The Moon is receding from the Earth. Eventually, the Earth will become tidally locked with the Moon, and the two with spin forever facing each other. This may require another billion years or so, so it isn't anything that we or our human ancestors will need to worry about.

And when that time comes, we'll probably have other things to worry about - like the expanding Sun. We'll want to pick up the Earth and move it outward a bit; perhaps we'll grab Mars along the way, and give ourselves an extra-large Moon2 to go along with the original Moon.

Answer 2

We're not quite sure what the question means by "earth's tilt" or "stay the same".

The axis of the earth's rotation is inclined about 67.5 degrees to the plane of

the earth's orbit, and that doesn't change. Over the course of a human lifetime,

or several human lifetimes, the pole of earth's axis remains pointed toward the

same spot in the sky, presently quite close to the star Polaris. Over a period of

26,000 years, the pole describes a circle in the sky, but the axis remain inclined

to the plane of the orbit by the same 67.5 degrees.

So we must take issue with the premise of the question, and say that the earth's

"tilt" really does "stay the same".

Answer 3

Inertia.