How eclipses work
The Sun is about 400 times wider than the Moon but also about 400 times farther away, so the two look almost the same size in our sky. That coincidence lets the Moon cover the Sun neatly. There is a new moon every month, but the Moon's orbit is tilted about 5 degrees to Earth's orbital plane, so an eclipse happens only when new moon falls near one of the two crossing points, or nodes. A total eclipse is seen along a narrow strip, usually 100–200 km wide, swept by the Moon's dark umbra; a partial eclipse is seen across the much wider penumbra. When the Moon is near its farthest point and looks smaller, it cannot cover the Sun completely and an annular eclipse results. A lunar eclipse is the reverse: Earth's shadow falls on the Moon.
| Type | What you see |
|---|---|
| Total | Moon covers the Sun completely; corona visible |
| Partial | Only part of the Sun is covered |
| Annular | Moon appears smaller, leaving a ring of fire |
| Hybrid | Shifts between total and annular along the path |
Eclipses in history
Eclipses were long read as omens for rulers; Chinese, Babylonian and Korean court astronomers recorded them carefully, and these records now help scientists measure the slowing of Earth's rotation. Tradition says Thales of Miletus predicted the eclipse of 585 BC. The most dramatic eclipse in the history of science was on 29 May 1919: expeditions led by Arthur Eddington measured how much starlight bent near the Sun and announced agreement with Einstein's general theory of relativity, making Einstein a global celebrity overnight. Helium was first detected in the spectrum of solar prominences during the eclipse of 1868.
Safe viewing and upcoming eclipses
Looking at the Sun with the naked eye, sunglasses or smoked film can damage the retina. Use eclipse glasses or solar viewers meeting ISO 12312-2, and fit a proper solar filter to the front of any telescope or binoculars. Only during totality, the brief moment the Sun is completely covered, is it safe to look directly and see the corona. Upcoming total eclipses include 12 August 2026 (Greenland, Iceland, Spain), 2 August 2027 (Spain, North Africa, the Middle East, with up to 6 minutes of totality) and 22 July 2028 (Australia, New Zealand).
FAQ
- Why isn't there a solar eclipse every month?
- Because the Moon's orbit is tilted about 5 degrees to Earth's, so at most new moons the Moon passes above or below the Sun in our sky.
- How long does a total solar eclipse last?
- Totality lasts at most about 7.5 minutes and usually 2–4 minutes. The whole event, including the partial phases, takes two to three hours.
Sources reviewed: 2026-10-26
References
- Espenak, F., & Meeus, J. (2006). Five Millennium Canon of Solar Eclipses: −1999 to +3000. NASA Technical Publication TP-2006-214141.
- Dyson, F. W., Eddington, A. S., & Davidson, C. (1920). A determination of the deflection of light by the Sun's gravitational field. Phil. Trans. R. Soc. A, 220, 291–333.
- Stephenson, F. R. (1997). Historical Eclipses and Earth's Rotation. Cambridge University Press.
- American Astronomical Society. (2024). How to View a Solar Eclipse Safely.
- Einstein, A. (1916). Die Grundlage der allgemeinen Relativitätstheorie. Annalen der Physik, 354(7), 769–822.
- Lockyer, J. N. (1868). Notice of an observation of the spectrum of a solar prominence. Proceedings of the Royal Society of London, 17, 91–92.
- Stephenson, F. R., Morrison, L. V., & Hohenkerk, C. Y. (2016). Measurement of the Earth's rotation: 720 BC to AD 2015. Proc. R. Soc. A, 472, 20160404.
- Steele, J. M. (2000). Observations and Predictions of Eclipse Times by Early Astronomers. Kluwer.