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.

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.

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

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

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.

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.

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

In 2025, the European Space Agency created the first artificial solar eclipse in space when one spacecraft cast a shadow onto another spacecraft to enable observations of the sun's outermost atmosphere.

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.

Eclipse glasses protect the eyes from overexposure to the sun's ultraviolet and infrared radiation, as a person's instinct to look away from the sun is diminished when it's partly blocked.

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.

Learn about the sun's corona, which is nonlethal despite a temperature of millions of degrees

The outermost layer of the sun's atmosphere is best seen during a solar eclipse, when the moon blocks the much brighter (and significantly cooler) solar surface. Despite the high-energy particles in the corona moving fast enough to escape the sun's gravity and gradually become solar wind, their density is too low to contribute meaningfully to the region's overall radiation.

Global eclipse tourism is a multibillion-dollar industry, with the 2024 total solar eclipse across North America estimated to have generated $6B in economic activity across regions along its path.

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

In 1676, Danish astronomer Ole Rømer determined that light did not travel instantaneously by observing a delay in the appearance of eclipses on Jupiter when it was farther from Earth.

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.

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

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.

The impacts of the solar maximum on Earth, from telecommunications to auroras

During the peak of the sun's 11-year cycle, plasma emissions stronger than the average stream of particles from the sun can compress and distort the Earth's magnetic field, allowing auroras to be seen farther from the poles. Distortions in the ionized layer of Earth's atmosphere can also alter the path of communication transmissions through the air. (Some readers may experience a paywall.)

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.

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.

The intensity of auroral activity approximately follows the sun's 11-year cycle

The density, speed, and temperature of material ejected by the sun are at their lowest at the start of each cycle, resulting in weaker interactions with Earth's magnetic field and muted, diffuse auroras. While the average solar wind speed is about 300 kilometers (186 miles) per second, the fastest winds can be more than three times faster.

Learn about solar neutrinos—about 70 billion of which pass through your thumbnail every second

About 100 quadrillion sextillion (10³⁸) of these elusive particles are created in the core every second, making up about 1% of the sun's total energy output. Because they seldom interact with normal matter, highly specialized equipment is needed to detect them, allowing scientists to probe what is happening in the solar core.

View historical records of solar observations and discoveries, from telescopes in the early 1600s revealing sunspots to NASA's Parker Solar Probe photographing the sun from within its outer corona in 2025.

How scientists study Earth's geocorona, the farthest portion of the planet's exosphere

Seen via ultraviolet radiation scattered by neutral hydrogen in the region, observations by the ESA/NASA Solar and Heliospheric Observatory indicate that the geocorona extends roughly 50 times Earth's diameter above its surface. At this distance, the geocorona extends beyond the Moon's orbit.

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.

Why it takes tens of thousands of years for light from the sun's core to reach its surface

Photons take about eight minutes to travel through empty space to Earth after leaving the sun's surface. However, traveling from the core to the surface involves these particles of light undergoing a random walk—scattering off charged particles deep in the sun like a pinball—causing a trip that is more than 200 times shorter to last as long as 170,000 years.

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

Scientists validated Albert Einstein's theory of gravity by measuring the apparent positions of stars via their starlight as it traveled near the sun on its way to Earth during a total solar eclipse.

If the sun disappeared, we would not know about it for 8 minutes and 20 seconds, at which point the Earth would suddenly move in a straight line on its way out of the solar system.

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.

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.