Eclipses
When the Moon blocks the Sun, and Earth shadows the Moon
Solar and lunar eclipses explained: why the Moon turns blood red, why we do not get eclipses every month, and a live list of the next eclipses you can see from your place.
NASA Glenn Research Center (GRC-2024-C-02616), Cleveland, Ohio, 8 Apr 2024. Public domain.
Two kinds of eclipse
Solar eclipse: the Moon in front of the Sun
At new moon the Moon sometimes passes exactly between the Sun and Earth. Its shadow falls on a narrow strip of Earth. Inside the dark central shadow (the umbra) the Sun is completely covered and day turns to twilight for a few minutes. Outside it, people see a partial eclipse: a "bite" taken out of the Sun.
It works because of a lucky coincidence. The Sun is about 400 times wider than the Moon but also about 400 times farther away, so both look almost the same size in our sky.
- Total: the Moon covers the whole Sun and the pearly corona appears. Totality never lasts more than about 7.5 minutes at one place.
- Annular ("ring of fire"): the Moon is near the far point of its orbit and looks slightly too small, leaving a bright ring.
- Partial: the Moon covers only part of the Sun.
- Hybrid: rare eclipses that are annular in some places and total in others.
Lunar eclipse: the Moon in Earth's shadow
At full moon the Moon sometimes passes through the shadow that Earth casts into space. Everyone on the night side of Earth can see it at the same time, and it is completely safe to watch with your eyes, binoculars or a telescope.
- Penumbral: the Moon passes through Earth's faint outer shadow. Many people do not notice anything.
- Partial: part of the Moon enters the dark inner shadow (umbra) and looks as if a dark bite is missing.
- Total: the whole Moon is inside the umbra. Totality can last more than an hour and a half.
Play with the shadows
The Moon's orbit is tilted about 5° to the plane of Earth's orbit. It crosses that plane at two points called nodes. Move the Moon around its orbit and turn the nodes, or press play to run a whole year.
Why isn't there an eclipse every month?
If the Moon orbited in exactly the same plane as Earth goes around the Sun, we would get a solar eclipse at every new moon and a lunar eclipse at every full moon. But the Moon's orbit is tilted by about 5.1°. Most months the new Moon passes a little above or below the Sun, and the full Moon slips above or below Earth's shadow.
An eclipse can only happen when a new or full moon falls close to one of the two nodes, where the Moon's orbit crosses Earth's orbital plane. That lines up for a few weeks roughly every six months (about every 173 days). These windows are called eclipse seasons. Each one brings at least one solar and one lunar eclipse, often two of one kind.
- Every year has at least 2 solar eclipses somewhere on Earth, and between 4 and 7 eclipses in total.
- The nodes slowly turn backwards, once every 18.6 years, so eclipse seasons arrive about 19 days earlier each year.
- Eclipses repeat in families: after one saros of 18 years, 11 days and 8 hours, Sun, Earth and Moon return to nearly the same geometry and a very similar eclipse happens again, a third of the way around the world.
Why a blood moon is red
Even fully inside Earth's shadow, the Moon does not go black. Sunlight still reaches it by bending (refracting) through Earth's atmosphere, around the edge of our planet.
On the way, air scatters away most of the blue light (the same reason the sky is blue). The reds and oranges get through. In effect, the eclipsed Moon is lit by every sunrise and sunset on Earth at once.
How dark and how red depends on our atmosphere. After big volcanic eruptions, dust high in the air can make eclipses very dark, almost brown. Astronomers rate them on the Danjon scale from L0 (very dark, the Moon almost invisible) to L4 (bright copper-orange).
Next eclipses from your place
Computed live in your browser with the open-source Astronomy Engine. Pick a place to see which eclipses you can actually see, and when.
Lunar eclipses
Solar eclipses visible here
Every solar eclipse on Earth
Dates in UTC. Only places near the central line of a total or annular eclipse see the full show.
At a glance: the next eclipses worldwide
- Solar, 6 Feb 2027: annular ("ring of fire") eclipse across southern South America, the South Atlantic and West Africa.
- Lunar, 20 Feb 2027: penumbral eclipse, a faint shading of the full Moon.
- Lunar, 18 Jul and 17 Aug 2027: two faint penumbral eclipses.
- Solar, 2 Aug 2027: total eclipse, over six minutes long near Luxor, crossing southern Spain, North Africa, Egypt and Arabia.
- Lunar, 12 Jan 2028: partial eclipse.
- Solar, 26 Jan 2028: annular eclipse over northern South America, the Atlantic, Portugal and Spain.
- Lunar, 6 Jul 2028: partial eclipse.
- Solar, 22 Jul 2028: total eclipse across Australia (including Sydney) and New Zealand.
- Lunar, 31 Dec 2028: total eclipse, a blood moon to end the year.
Dates in UTC, computed with Astronomy Engine and matching NASA's eclipse catalogue. The live finder above shows times and visibility for your own place.
How to watch safely
- Use eclipse glasses that meet the ISO 12312-2 standard, with no scratches or holes.
- Or watch indirectly: a pinhole projector (a small hole in card) throws a tiny image of the crescent Sun on the ground. Gaps between tree leaves do the same.
- Only during the brief totality of a total eclipse is it safe to look without glasses. Put them back on as soon as the bright Sun starts to return.
- Lunar eclipses are completely safe. No filters needed.
Eclipses in history and science
- About 2,000 years ago: Babylonian astronomers had already noticed the saros cycle and could predict when eclipses were possible. The Greek Antikythera mechanism has an eclipse-prediction dial.
- 585 BC: according to the historian Herodotus, a solar eclipse stopped a battle between the Lydians and the Medes, who took it as a sign to make peace.
- 1868: astronomers studying the Sun's glowing edge during an eclipse found a new element. It was named helium, after the Greek word for Sun, decades before it was found on Earth.
- 1919: during a total eclipse, expeditions led by Arthur Eddington measured starlight bending around the Sun, backing Einstein's general theory of relativity.
- 2017 and 2024: total eclipses crossed North America and were watched by tens of millions of people.
- 2026: the Artemis II astronauts saw a solar eclipse from behind the Moon.
Total solar eclipses will not last forever. The Moon is drifting away by about 3.8 cm a year (see Tides & Earth), so it is slowly looking smaller. In several hundred million years it will be too small to cover the Sun completely, and only annular eclipses will remain.
Quick answers
How often do solar eclipses happen?
Somewhere on Earth, 2 to 5 times a year. But a total eclipse is only seen along a narrow path, so any one spot sees a total solar eclipse only about once every 375 years on average.
Is it safe to look at a lunar eclipse?
Yes. A lunar eclipse is just the Moon in Earth's shadow, dimmer than a normal full Moon. It is safe with your eyes, binoculars or a telescope.
Why is the Moon red during a total lunar eclipse?
Sunlight bends through Earth's atmosphere, which scatters away blue light and lets red light through. The Moon is lit by the light of all Earth's sunrises and sunsets at once.
Why don't eclipses happen every month?
The Moon's orbit is tilted about 5 degrees, so usually the new Moon passes above or below the Sun and the full Moon misses Earth's shadow. Eclipses only happen in two "eclipse seasons" a year, when the line-up is right.
What is the difference between a total and an annular eclipse?
In both, the Moon passes centrally across the Sun. If the Moon is close to Earth it looks big enough to cover the Sun completely (total). If it is far away it looks slightly smaller and leaves a ring of sunlight (annular).
Sources and credits
- NASA Science, Eclipses and eclipse safety.
- Fred Espenak and Jean Meeus, NASA Eclipse Web Site (Five Millennium Canon of eclipses).
- Astronomy Engine by Don Cross, github.com/cosinekitty/astronomy (MIT licence), used for the eclipse finder.
- Place search: Open-Meteo geocoding API (CC BY 4.0).
- NASA, Artemis II flyby and eclipse, April 2026.
- American Astronomical Society, Eclipse eye safety (ISO 12312-2 filters).
Photos credited to NASA, NOAA and other public-domain sources are used with thanks; BotBuhdy adds a small botbuhdy.com mark. Pictures labelled AI-generated illustration are artist-style illustrations made for this page, not photographs.