What Is an Eclipse?

[gentle music] Okay, so an eclipse happens when one object in space blocks light from reaching another object, creating a shadow.

[upbeat music] The kind I saw in 2017 was a solar eclipse.

A solar eclipse happens when the Moon moves between the Earth and the Sun.

So if you were to look at it from the side, you would see the Sun, and then the Moon, and then the Earth perfectly lined up.

The Moon blocks some of the sunlight and casts a shadow onto Earth.

[whoosh] If you go outside on a sunny day and move your hand in front of the sun so that it's not getting in your eyes, that's kind of what happens with a solar eclipse.

It's as if you are the Earth, your hand is the Moon, and the Sun is the Sun.

[laughs] If you place your hand just right, then your hand, or the Moon, can completely cover the bright face of the Sun.

That is a total solar eclipse.

But wait, isn't the Sun way bigger than the Moon? How could the Moon cover the Sun? Well, it's true that the Moon is much, much, much, much smaller than the Sun.

In fact, you could fit 64 million Moons inside of the Sun.

But there's one important piece of the puzzle that we haven't discussed yet.

Do you know what it is? Yep, the Moon is way closer to us.

So even though it's much smaller than the Sun, since the Sun is so far away, they appear about the same size in the sky.

Have you ever noticed that? You know how when you see someone who is standing really, really far away from you, it makes them look really small? Well, imagine if instead of a regular-sized person standing that far away, let's imagine that person was a giant.

If a giant is standing that far away, they could actually look like the same size as a regular-sized person standing close to you.

That's what's happening with the Sun and the Moon in the sky.

The Moon is much smaller than the Sun, but since the Sun is so much farther away, it looks a lot smaller than it really is.

[gentle music] And that means that on the rare occasion when they line up perfectly in the sky, the Moon can cover the Sun.

[whoosh] [explosion] And that is what made it so dark that day in my backyard.