Although the moon passes between the sun and Earth each month, its orbit is tilted by five degrees, preventing Earth from experiencing a solar eclipse each month.

Every eclipse is preceded or followed by another eclipse, separated by about two weeks and alternating between solar and lunar types.

Over thousands of years, the frequency of solar eclipses is greatest around the Arctic and Antarctic Circles and lowest near the equator.

While the sun, moon, and stars rise and set from east to west due to Earth's rotation, the moon's eastward revolution around the Earth causes its shadow to move from west to east during a solar eclipse.

Solar eclipses are a cosmic coincidence because the moon is 400 times smaller than the sun but 400 times closer to Earth, allowing it to completely block sunlight.

Differences in the tilts of planetary orbits make perfect alignment impossible

Mercury deviates within 7 degrees of the ecliptic that marks the path of the sun, with the other planets varying from 3 degrees to approximately flat. Even an alignment within 1 degree between all eight planets is estimated to occur only once every 13.4 trillion years.

Because the half of Earth that faces the sun is larger than the area of the shadow cast by the moon during a solar eclipse, observers may experience a total, annular, or partial eclipse.

Blood moons only occur during total lunar eclipses, when the Earth blocks the sun, but its atmosphere lets redder parts of sunlight through to reflect off the lunar surface.

By identifying patterns in the periodic movements of the sun, moon, and Earth, ancient civilizations realized that identical eclipses repeat about once every 6,585 days, known as the saros cycle.

The moon is moving 3.8 centimeters farther away from Earth each year

Driven by tidal forces, the effect is minimal and slow, ensuring stable tidal patterns and lunar cycles. Earth's rotation slows down as the Moon gains orbital momentum, slowly lengthening the day over time.

Moon's visibility is determined by its declination, equivalent to Earth latitude

The Moon's declination varies between approximately +28.7 degrees and -28.7 degrees, ensuring it rises and sets between latitudes of approximately 61.3 degrees north and south. This means there are places on Earth where the Moon is never visible above the horizon and places where it temporarily does not set.

Why time ticks faster on the moon, which may need its own time zone

Because Earth exerts a stronger gravitational pull than the moon, it lags behind between 56 and 59 microseconds each day, or about one second every 46.5 years. This impacts essential synchronous operations of future electronic equipment on the lunar surface, which could be alleviated by a standardized conversion system between Earth and moon time zones.

Earth’s tilt and orbit cause the sun to create a figure-eight pattern

The shape—called an analemma—can be obtained by photographing the sun from the same location and time daily for a year. The Earth's eccentricity created the analemma's width, and its tilt shifts the sun's height in the sky over the seasons.

Just before and just after a total solar eclipse, sunlight can pass through uneven terrain on the lunar surface, producing disconnected bits of light around the moon called Baily's beads.

How lunisolar calendars work

Despite being called Lunar New Year, the Chinese calendar that the holiday is based on is actually lunisolar, or based on both the sun and the moon. Many religious holidays—including Easter, Ramadan, Chinese New Year, and Passover—do not have fixed dates according to the now-ubiquitous Gregorian calendar.

Changes in Earth's orbital cycles influence the timing of ice ages

These cycles include changes in Earth's orbit shape, tilt, and wobble, all of which alter how much solar energy different parts of Earth receive over time. Due to orbital eccentricity, summers in the Northern Hemisphere last about 4.5 days longer than winters.

While solar eclipses were considered ominous throughout history, multiple cultures explained the celestial event as the result of mythical creatures nearly consuming the sun.

How its uneven rotation produces the sun's 11-year cycle and flips its magnetic poles

While charged material rises and falls in the sun's convection zone, which induces magnetic fields, different latitudes rotate at different rates, making these fields increasingly turbulent. This builds to a critical point—the solar maximum—where magnetic field-driven events, such as solar flares, become more common before the field collapses and flips, restarting the cycle.

How the moon creates tides

Anyone who has visited large bodies of water virtually anywhere on Earth notices low and high tides occur at regular intervals, a process primarily driven by the moon’s gravitational pull. This explainer details how the motion of the Earth and Moon interact to create tides.

In the third century BCE, the Greek astronomer Aristarchus of Samos estimated the distance to the moon using geometry after measuring the length of Earth's shadow during a lunar eclipse.

See a lunar eclipse share the night sky with the Milky Way

Photos taken at the Cerro Tololo Inter-American Observatory in Chile in March 2025 captured a blood moon and the Milky Way galaxy within the same field of view. The moon appears red from the bluer parts of its reflected sunlight being scattered by Earth's atmosphere.

Just as squeezing a grape causes it to bulge, the moon's gravity exerts an overall pressure that displaces water toward the opposite sides of Earth's equator, producing tides.

Visualize the path of every solar eclipse from 1900 to 2099 and see what each looks like when observed from different locations on Earth.

Is the sun aligned with Stonehenge right now?

Twice a year, during the longest day and night, the sun’s path aligns ever so gently with the ruins of Stonehenge. During the summer solstice, viewers can see the sun’s rise crest the central heel stone. The winter solstice sees the sun set across the site’s altar stone. Use this interactive to tour the historic site and check its current skyscape.

Grasp the earth's orbit around the sun with this interactive

See why seasons exist with this interactive simulator. Toggle between different views of the earth in relation to the sun and watch as the earth's axis causes the sun to shine at different angles throughout the year, causing the weather to fluctuate and more. This simulator clarifies a process many take for granted.

View photographs of solar eclipses on Mars, Jupiter, and Saturn caused by the moons of these planets blocking sunlight.

Just as directly observing a solar eclipse without protective glasses can cause permanent eye damage, photographing an eclipse requires a specialized filter to prevent damaging your camera.

Why the sun's equator rotates once every 24.5 days, but the poles take over 34 days

Just like the Earth, linear speeds on the surface of the sun decrease from the equator to the poles. However, rotation time also appears to vary with depth, with the radiative zone beneath the convection zone rotating about once every 26.6 days. Measurement uncertainty has prevented measurement of the rotation of the solar core.

Astronomers can identify systems with pairs of orbiting stars by observing recurring dips in the system's brightness as the stars eclipse one another.

The majority of exoplanets—planets outside the solar system—have been discovered through mini-eclipses created when they pass in front of their host star and block some of its light from reaching Earth.

Enough sunlight hits Earth in just 90 minutes to power the planet for an entire year

Despite this, in 2023, only 5.1% of electricity in the US came from solar energy. Solar panel technology has nonetheless made significant advancements since the 19th century, largely due to NASA's efforts in the space race.