On Friday, April 27, 2018 at 6:20:03 PM UTC+1, palsing wrote:


Gerald does not understand that if someone were to be living on the 'back' side of the moon he would not even be aware of the Earth's existence, but he would nevertheless see the Sun and stars rise and set... and using the exact same logic as Earthbound scientists, would eventually determine that he was orbiting the Sun every year and rotated on his own axis every month or so...

The Earth turns in two distinct ways which is why an observer at the South Pole sees the Sun rise and set once each year on the Equinoxes whereas all other times the Sun is either in view or out of view.
An observer on the far side of the moon doesn't see the Earth rise, remain in view for half its orbit,set and then remain out of sight for the other half of its monthly orbit.


The surface rotation as a function of the Earth's orbital motion is uneven (the variable component of the Equation of Time) in response to variable orbital speed while this surface rotation turns parallel to the orbital plane and at right angles to the circle of illumination.

Of course in this era of total celestial sphere anarchy, a website sponsored by the space agency has a pivoting circle of illumination but anarchy can't be reasoned with -

https://apod.nasa.gov/apod/ap170319.html