In a total solar eclipse, the Moon passes between the Sun and Earth and blocks the face of the Sun. During a total solar eclipse, the daytime sky gets dark, as if it were dawn or dusk. A solar eclipse happens at the new moon, when the Moon moves between Earth and the Sun. 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. On Earth, the narrow line where a total solar eclipse can be seen is called the path of totality. On average, a total solar eclipse happens somewhere on Earth every one or two years.

Totality at one place lasts from about 10 seconds to about seven and a half minutes at most. The April 8, 2024 total solar eclipse had its longest totality, 4 minutes 28 seconds, at Nazas, Durango, Mexico. The total solar eclipse of April 2024 lasted longer than the one in 2017 because the Moon was closer to Earth in 2024. The Sun is about 400 times wider than the Moon but also about 400 times farther away, so they look about the same size in the sky. As of November 2026, the August 2, 2027 total solar eclipse is expected to last as long as 6 minutes 23 seconds.

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. A hybrid solar eclipse is a rare kind that shifts between annular and total along its path; fewer than 5% of solar eclipses are hybrid. In most places, a total, annular or hybrid eclipse looks like a partial eclipse. 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.

The Moon has no light of its own. It shines because its surface reflects sunlight. In a lunar eclipse, Earth's shadow falls on the Moon. A lunar eclipse happens at the full moon. There are three types of lunar eclipse: total, partial and penumbral. The Moon's shadow has a dark center called the umbra and a lighter outer part called the penumbra. A penumbral lunar eclipse happens when the Moon's penumbra covers all or part of the Moon but the umbra misses it. In a lunar eclipse, sunlight bent by Earth's atmosphere reaches the Moon, and the Moon looks red. The Moon in a total lunar eclipse often looks a dull red or orange. Seen from the Moon, a total lunar eclipse would show every sunrise and sunset happening on Earth at that moment.

People have watched eclipses for a long time. The earliest writings showing that people paid official attention to eclipses are around 5,000 years old. Babylonian astronomers could predict lunar eclipses, and later solar eclipses, with fair accuracy. The total solar eclipse of August 21, 2017 crossed the United States from Oregon to South Carolina in a path about 70 miles wide. The path of totality of the August 12, 2026 total solar eclipse crossed Greenland, Iceland, the Atlantic Ocean and northern Spain, with a small part of Portugal. Fully eclipsed totality on August 12, 2026 was forecast to last less than two minutes for most people in the path.

Safe viewing starts with the right glasses. Here is what to know about eclipse glasses. Never look at the Sun, even in an eclipse, without eclipse glasses that a grown-up gives you. During a partial eclipse it is never safe to look straight at the Sun without proper eye protection. Eclipse glasses are special glasses made for looking at the Sun safely. Regular sunglasses are not safe for looking at the Sun. Safe eclipse glasses meet the ISO 12312-2 standard, which does not cover ordinary sunglasses. Some sellers put the ISO label on eclipse glasses that were never tested or certified.

Look at an eclipse glasses filter first: scratched, punctured or torn eclipse glasses should be thrown away. Put your eclipse glasses on before you look up at the Sun, and keep your eyeglasses on under them. Always watch children who are using eclipse glasses or other solar filters. A pinhole projector lets you watch an eclipse as a shadow picture, without looking at the Sun through the hole. Unlike a solar eclipse, a lunar eclipse is always safe to look at with your eyes alone. A solar eclipse is different: do not look straight at the Sun without proper eye protection.

Words to know

• penumbral: faint shadow type
• annular: Moon looks smaller
• hybrid: shifting eclipse kind
• corona: Sun's outer atmosphere