Precession vs obliquity?

deereidy

Hello, I'm sorry if this has been asked before, or if this is the wrong forum to post this in, but it seemed the only one that seemed appropriate. I am trying to understand the difference between precession and obliquity in regard to orbital forcing,but they sound like different descriptions of the same thing. As I understand it, obliquity is the actual tilt of the Earth relative to its orbit around the sun, causing the seasons. However, the definition for precession is "the orientation of the Earth's axis". I really can't see the difference between either of these, they both just sound like they are describing the tilt of the Earth's axis. Can anyone explain the difference?

Turtwig

The first thing I'd recommend is that you read up on the physics of gyroscopes. It was reading Feynmans lectures, that I finally grasped the basics (at least I think I have.) But there's probably another more modern user friendly source out there.

Precession entails the change in the orientation of the Earth's axis of rotation.

Obliquity is a measure of the angle of between the Earth's axis of rotation and a line that is perpendicular to the earth's orbital plane. Obliquity tends to remain constant as the planet precesses, but not always.


Animations that sort of illustrates both.

They sound deceptively simple. So don't worry if you're having trouble getting your head around them, it takes time.:)
Watch the entire video for a pretty good illustration.