Let us start with a puzzle. A solar eclipse happens at the new moon, when the Moon moves between Earth and the Sun. You may have heard that an eclipse happens every month. In fact, most months there is none. Here is why not. The Moon's orbit around Earth is tilted by about five degrees. Most months the new moon passes above or below the Sun. Its shadow misses Earth, so there is no solar eclipse.

The Moon's shadow has a dark center called the umbra. It also has a lighter outer part called the penumbra. To see a total solar eclipse you must be inside the Moon's darkest shadow, the umbra. People standing in the Moon's penumbra see a partial solar eclipse. In a partial solar eclipse, the Moon covers only part of the Sun. A solar eclipse can be seen from only a small part of Earth at a time.

In a total solar eclipse, the Moon passes between the Sun and Earth. It blocks the face of the Sun. During a total solar eclipse, the daytime sky gets dark, as if it were dawn or dusk. The Sun is about 400 times wider than the Moon. But it is also about 400 times farther away, so they look about the same size in the sky. On Earth, the narrow line where a total solar eclipse can be seen is called the path of totality.

There are four types of solar eclipse: total, partial, hybrid and annular. In an annular solar eclipse the Moon is too far from Earth to cover the whole Sun. So it looks smaller than the Sun. Eclipses are very useful to scientists, as well as beautiful. The corona is the Sun's outer atmosphere. We cannot normally see it because the Sun's bright surface is in the way. But it shows in a total eclipse.

Now turn to the Moon, which has eclipses too. In a lunar eclipse, Earth's shadow falls on the Moon. A lunar eclipse happens at the full moon. A solar eclipse happens at the new moon, when the Moon moves between Earth and the Sun. You may have heard that the Moon goes completely dark in a lunar eclipse. In fact, the Moon in a total lunar eclipse often looks a dull red or orange.

Here is how to watch with care. Never look straight at the Sun without proper eye protection, even during a partial eclipse. Regular sunglasses are not safe for looking at the Sun. Eclipse glasses are special glasses made for looking at the Sun safely. A grown-up can give you a pair. A pinhole projector lets you watch an eclipse as a shadow picture. You do not look at the Sun through the hole.

Words to know

• umbra: dark center
• penumbra: lighter outer part
• corona: Sun's outer atmosphere
• annular: Moon looks smaller