[ELI5] How do we predict solar and lunar eclipse?
In: Mathematics
In modern times it’s orbital mechanics and geometry. We can predict where the Sun, Earth, and Moon are going to be relative to each other and draw lines from a potential viewer to the sun and moon to figure out what people would see with things in that position.
The moon orbits the earth about once a month. So if the earth moon and sun were all orbiting in the same plane you’d expect one solar and one lunar eclipse every month. Unfortunately they don’t orbit in the same plane, so there’s only an opportunity for an eclipse twice a year, when the intersection of these two planes (earth around sun, and moon around earth) aligns with the earth and sun. Though even this isn’t quite enough, because you also have to have a new moon when this happens to get a solar eclipse, or a full moon to get a lunar eclipse. And depending on how far away the moon is from the Earth, and how well it’s aligned, you might not get a total eclipse.
In ancient times they didn’t understand the orbital mechanics, but they did notice the patterns, see “antikythera mechanism”
Latest Answers