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Video transcript

I've talked a lot about precession and the changes in the inclination of Earth's orbit but I haven't told you why they are happening and I'm not going to go into the physics of it it's a little bit beyond this discussion right over here but they really a byproduct of the earth and Suns interactions with earth and with the fact that earth is not a perfect sphere so if I draw earth so this is my little drawing of Earth and let me put the poles over here North Pole and South Pole it actually turns out that Earth is fatter than it is taller so if you were to measure Earth's or its diameter along the equator its diameter around along the equator it is 43 kilometers or about 2743 kilometers which is approximately 27 miles longer longer than if you were to measure its diameter from pole to pole so longer than the pole to pole diameter and the fact that Earth has this equatorial bulge that it's not a perfect sphere and once again I'm not going to go into the math here it's the interactions between that I guess you could call it that one asymmetry of the earth it's that interaction between that and the the pull of gravity between the earth and the Sun and the moon that causes these long-term cycles these long-term but this this this this this axial precession and other other I guess less noticeable changes in Earth's orbit and as we'll see in the next video these aren't the only types of changes in orbits we have we also have changes in actual the actual ellipse that Earth's orbit has actually rotates over time but that's due more to interactions with Earth's orbit and the orbit of other planets in our solar system and once again it's one of those things that happen over thousands and thousands of years so all of these changes there because earth isn't completely set symmetrical more fat than it is tall those interactions between the gravity of the earth of the Sun and the moon and Earth's orbit as a whole changes because of interactions with other objects inside of our solar system