The Sun is much bigger than the Moon and Earth, so each of them casts all three kinds of shadow: umbra, penumbra and antumbra. The Moon's shadow has a dark center called the umbra and a lighter outer part called the penumbra. As the Moon's shadow stretches away from the Moon, the umbra narrows, so on Earth it covers only a small area compared with the penumbra. In an annular eclipse, the part of the Moon's shadow beyond the end of the umbra is the antumbra; people inside it see a ring of Sun. 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 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. You may have heard that the Moon is too small to cover the Sun. In fact, 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. In an annular solar eclipse the Moon is too far from Earth to cover the whole Sun, so it looks smaller than the Sun. On Earth, the narrow line where a total solar eclipse can be seen is called the path of totality, and a solar eclipse can be seen from only a small part of Earth at a time.

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, the Moon's orbit around Earth is tilted by about five degrees, and it crosses the plane of Earth's orbit at two points called nodes. Most months the new moon passes above or below the Sun, so its shadow misses Earth and there is no solar eclipse. An eclipse season lasts about 35 days and comes again just short of six months later. 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. During totality, some stars and planets become visible and the air temperature drops. Baily's beads are bright spots of sunlight that stream through valleys along the Moon's rough edge just before and after totality. The diamond ring effect looks like a bright gem on a ring around the Moon, at the first and last glimpse of the Sun. 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 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. Eclipses are very useful to scientists, as well as beautiful, and helium was first seen during the total solar eclipse of 1868 in India. 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 April 8, 2024 total solar eclipse had its longest totality, 4 minutes 28 seconds, at Nazas, Durango, Mexico, and it lasted longer than the one in 2017 because the Moon was closer to Earth in 2024.

In a lunar eclipse, Earth's shadow falls on the Moon, and a lunar eclipse happens at the full moon. The Moon has no light of its own, and it shines because its surface reflects sunlight. There are three types of lunar eclipse: total, partial and penumbral. 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. Eclipses of the Moon can be seen by far more people than eclipses of the Sun, because everyone on the night side of Earth can see them. Seen from the Moon, a total lunar eclipse would show every sunrise and sunset happening on Earth at that moment.

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, and regular sunglasses are not safe for looking at the Sun. Do not use adjustable or auto-darkening welding helmets to look at the Sun. Safe eclipse glasses meet the ISO 12312-2 standard, which does not cover ordinary sunglasses, and 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.

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 that day was forecast to last less than two minutes for most people in the path. As of November 2026, the next total solar eclipse that can be seen from the contiguous United States is on August 23, 2044. As of November 2026, an annular solar eclipse is due on February 6, 2027, visible in parts of South America and Africa. As of November 2026, a total solar eclipse is due on August 2, 2027, visible in southern Spain and North Africa, and it is expected to last as long as 6 minutes 23 seconds. As of November 2026, the next total solar eclipse after August 2, 2027 is on July 22, 2028. For each total or annular eclipse in the list, put your eclipse glasses on before you look up at the Sun.

Words to know

• antumbra: shadow beyond umbra
• nodes: orbit crossing points
• penumbral: faint shadow type
• corona: Sun's outer atmosphere