I have just learnt that a solstice and equinox are different by definition.
From what I understand, a solstice is when the rays of the sun are parallel to the equator, but I can't quite understand how an equinox is defined?
Some more mathematical explanations would be super helpful, and maybe even a diagram if possible?
I imagine this might have links to polar coordinates?
Solstice (or solstitium) is latin for "sun (level) ending", i.e. the day of maximal or minimal height of the sun path, so it comes in summer or winter.
Equinox is latin for equal night, i.e. where day and night have same lengths, so it comes in spring or autumn.
--- rk