How is it determined that the Earth is tilted on its axis by 23.5 degrees?
In: Planetary Science
It is relative to the sun and they have measured where the sun’s rays land at each solstice.
Its rotation is tilted that much relative to its orbit. It’s a pretty easy one to measure. Dangle a weight on a string so you know it’s perfectly plumb and track its shadow day to day over the course of a year. The most it ever leans is when the planet is tipped away/towards the sun the most and it leans at the same angle. Replace the plumb bob with some giant stone monoliths, start lining up other celestial bodies and boom you’re a paleolithic.
The earth’s orbit is a flat circle. If the earth were not tilted, then the sun would always be directly overhead at noon on the equator, every single day, because the equator would line up exactly with our orbit. It’s not…the latitude that gets the sun directly overhead changes each day, moving north up to the June solstice and then south down to the December solstice. The maximum latitude it reaches on these solstices is 23.5 degrees. We call these latitudes the *tropics*.
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