The math and process we use to predict the time and location of solar eclipses
In: Planetary Science
The Moon orbits the Earth. From our perspective, this means it moves around us in a circle…it takes about 29 days to complete this circle.
The Earth orbits the Sun. From our perspective, this means the Sun appears to move around us in a circle…it takes about 365 days to complete this circle.
These two circles are tilted with respect to one another in the sky.
Because of this, the two circles also intersect at two points on opposite ends of the sky. So twice a month, the Moon crosses through the Sun’s path.
All you have to do is figure out when the Moon crosses the Sun’s path at the same time the Sun is there, and boom, you’ve got yourself a solar eclipse.
The future positions of the earth and moon are determined by using Newton’s law of gravitation. Essentially, if you know the current position and speed of all the planets in the solar system and the moon, you can use their position to determine how much each is pulling on every other via gravity. The sum of all the pulls a planet experiences, along with its current position and speed, determines where it will be a short time in the future. So, you predict where everything will be a short while in the future, and then you repeat the process again. Doing that, you can figure out where everything will be at any time in the future for a long while.
Once you know where the moon, sun, and earth will be in the future, you can determine when they will be aligned enough to create eclipses, who those eclipses will be visible to, for how long, etc.
Latest Answers