Eclipses are a marvel of our Solar System, and it’s only due to the precise alignment of the Sun-Earth-Moon system that they happen at all. This marvel of geometry is worth exploring to understand the different types of eclipses and how often they occur.
There are two types of eclipses: solar and lunar. Both rely on light from the Sun being blocked and casting a shadow, but what makes them different is where the human observer is positioned.
Total solar eclipses are the most stunning of eclipses. This is when the Moon completely covers the Sun and the world is plunged into near darkness. However, these events are rare, especially if you cannot travel to see one! In order for a total solar eclipse to happen, the Moon must be in its new moon phase and the observer must be in the path of totality, where the Moon blocks the entire Sun (not just part of it; that would be a partial solar eclipse!).
If the Moon orbits the Earth once per month, you might be wondering why there isn’t a total solar eclipse every month. Even if it’s only partial near you, surely somewhere on Earth there should be one every new moon. The problem is our three-body system isn’t perfect.
The Moon orbits the Earth at an angle; sometimes it’s a bit too high, other times a bit too low. So, at minimum, there should be at least two solar eclipses per year. However, the Moon isn’t always the same distance between the Earth and the Sun. Sometimes, even when it passes directly in front of the Sun, the Moon is too close to the Sun to block the entire disc, which creates an annular eclipse.
Lunar eclipses are very similar to solar eclipses, except the Earth is the one casting the shadow. These eclipses also last longer because the Earth casts a larger shadow. Total lunar eclipses are the ones that look the most visually interesting and, unlike total solar eclipses, are much easier to see! These eclipses happen during a full moon, when the Earth is blocking the Sun from the Moon. This shadow means that the only light hitting the Moon is from light bent by the atmosphere of the Earth, creating a red glow on the surface of the Moon. The exact color of the glow depends on how much dust and clouds are present in Earth’s atmosphere; the more dust, the darker the Moon appears.
The best part of lunar eclipses is that they can be seen by everyone on the night side of the Earth. As the Earth moves into position, you can see a partial eclipse happening if you look carefully, but once the full shadow covers the Moon, it’s a spectacular sight. Just like total solar eclipses, total lunar eclipses won’t happen every month because all three celestial bodies need to line up perfectly.
So, when is the next eclipse you can see? TimeandDate has a great webpage for finding the next solar or lunar eclipses, whether you want to travel or watch from the comfort of your backyard. In 2024, there will be a total solar eclipse visible from Bloomington, IN! Take the opportunity to witness this geometric marvel for yourself and think about the giant celestial bodies lining up perfectly around you.
If you are viewing a solar eclipse, remember to do it safely.
Edited by Ben Greulich and Evan Leake