I did not know this:
The combined gravitational pull of the Sun, Saturn, Jupiter and other planets cause the shape of the Earth’s orbit to vary from its most elliptical to almost circular on a 110,000 year time scale.
Via Come Rain Or Shine.

Have a look at Milankovic Cycles if you’re interested in all the regular wobbles in Earth’s orbit.

@yorrike 😀 The same page on the course talked about them. Its all a bit mind-blowing really.