Winter Solstice - Shortest Day of the Year

https://www.timeanddate.com/calendar/winter-solstice.html

What causes the seasons?

https://www.metoffice.gov.uk/learning/seasons

https://www.shutterstock.com/zh/image-vector/illustration-winter-solstice-on-december-21-158711057

Weird Science: Antarctic Midnight Sun Disproves Flat Earth Theory, but Did It Just Kill The Globe Earth Fact?

https://busy.org/@bullishmoney/weird-science-antarctic-midnight-sun-disproves-flat-earth-theory-but-did-it-just-kill-the-globe-earth-fact

How Sundials Work

http://sundialsoc.org.uk/discussions/how-do-sundials-work/5/

Illumination of Earth by Sun at the southern solstice.

https://en.wiktionary.org/wiki/solstice#/media/File:Earth-lighting-winter-solstice_EN.png