Learn About Eclipses
Everything you need to know about solar and lunar eclipses, from the science behind them to their historical significance.
Types of Eclipses
Total Solar Eclipse
The moon completely covers the sun, revealing the sun's corona. Occurs when the moon passes between Earth and the sun during a new moon phase, and the moon's shadow falls on Earth's surface.
Viewing: Safe to view with naked eye ONLY during totality. Eclipse glasses required before and after.
Annular Solar Eclipse
The moon covers the sun's center, leaving a bright ring or "ring of fire" visible. Occurs when the moon is at or near its farthest point from Earth, appearing smaller than the sun.
Viewing: Eclipse glasses required at all times - NEVER safe to view with naked eye.
Partial Solar Eclipse
The moon partially covers the sun, creating a "bite" taken out of the solar disc. Visible from locations where the moon's penumbra (outer shadow) falls on Earth.
Viewing: Eclipse glasses required at all times.
Total Lunar Eclipse
Earth passes between the sun and moon, casting its shadow on the moon. The moon often appears red or copper-colored during totality, known as a "blood moon," due to sunlight refracting through Earth's atmosphere.
Viewing: Completely safe to view with naked eye.
Why Do Eclipses Happen?
Eclipses occur due to the precise alignment of the Sun, Moon, and Earth. Despite the Sun being 400 times larger than the Moon, it's also about 400 times farther away, making them appear nearly the same size in our sky. This cosmic coincidence makes total solar eclipses possible.
The Moon's orbit around Earth is tilted about 5 degrees relative to Earth's orbit around the Sun. This means eclipses only occur when the Moon crosses the plane of Earth's orbit (called the ecliptic) during a new moon (solar eclipse) or full moon (lunar eclipse).
This alignment happens roughly every 6 months, creating "eclipse seasons" when solar and lunar eclipses can occur within about two weeks of each other.
Famous Historical Eclipses
May 28, 585 BCE - "Eclipse of Thales"
Predicted by Greek philosopher Thales, this eclipse reportedly stopped a battle between the Lydians and Medes. It's one of the earliest recorded predictions of an eclipse.
May 29, 1919 - Einstein's Theory Confirmed
Observations during this total solar eclipse provided the first confirmation of Einstein's theory of general relativity, showing that light from distant stars was bent by the Sun's gravity.
August 21, 2017 - "Great American Eclipse"
The first total solar eclipse to cross the entire continental United States in 99 years. Millions traveled to the path of totality, making it one of the most-watched eclipses in history.
The Saros Cycle
Ancient astronomers discovered that eclipses repeat in a cycle called the Saros, which lasts approximately 18 years, 11 days, and 8 hours. After one Saros period, the Sun, Moon, and Earth return to approximately the same relative geometry, and a nearly identical eclipse occurs.
However, each successive eclipse in a Saros series occurs about 120 degrees west in longitude due to the extra 8 hours of Earth's rotation. After about 70-80 cycles (1,200-1,500 years), the series ends as the Moon's shadow misses Earth entirely.
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