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For centuries, most people assumed the Sun traveled around Earth. It seemed like an obvious fact, proven by every sunrise and sunset.
Then, in 1543, the Polish astronomer Nicolaus Copernicus declared that the Earth actually revolves around the Sun! As Earth turns, it spins on its axis. This creates the illusion that the Sun rises in the east and falls in the west.
This shocking idea took a while to catch on. Once it did, though, scientists could finally explain why things like seasons and eclipses occurred.
▲ Nobody is sure why Stonehenge was built in southern England around 2500 B.C. We do know that the huge stones line up perfectly to mark the sunrise on the solstices and equinoxes. Because of that, some scholars believe Stonehenge may have been a temple devoted to Sun worship.
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Was Copernicus the first to say that Earth revolves around the Sun?
No. As early as 260 B.C., the Greek astronomer Aristarchus argued that Earth goes around the Sun. However, his theory never became popular.
Earth’s Seasons
We have seasons because Earth spins with a 23-degree tilt. Therefore, at various times during the year, some places get more sunlight than others. When the North Pole slants toward the Sun, the planet’s northern half (or hemisphere) enjoys the warmth of summer. When the South Pole slants toward the Sun, it’s summer below the equator. Spring begins when a pole starts to slant toward the Sun. Fall begins when a pole starts to slant away.
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When does the Sun shine at midnight?
Near the Northern Hemisphere’s summer solstice, the Sun shines all night at the North Pole. In fact, the Sun remains visible for six months (from March until September). Near the Northern Hemisphere’s winter solstice, the North Pole is dark for six months. In that time, the Sun shines continuously at the South Pole.
Solar Eclipses
A solar eclipse happens when the Moon blocks the Sun’s light over a part of Earth. How can something 400 times smaller than the Sun block out its rays? By a coincidence, the Moon is 400 times closer to Earth than the Sun. So it appears to fit right over the Sun, like a glove.
▲ Annular Eclipse
When the Moon is at a far point in its orbit, it can’t totally block out the Sun. That leaves an annulus, or ring, that’s brighter than a corona.
▲ Total Solar Eclipse
The Moon blocks out the entire Sun, except for a faint halo of light called a corona.
▲ Partial Solar Eclipse
The Moon doesn’t block the entire Sun.
During a solar eclipse, the shadow the Moon casts on Earth is very narrow. It’s no more than 168 miles wide. So even though about three total solar eclipses occur every four years, few people in any one place see them. Only eight will be visible from the continental U.S. during the twenty-first century. ▼
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Why do we use the word solar to describe things about the Sun, like solar heat, solar system?
It comes from the Latin word for Sun, which is sol.
Sun Facts
Temperature
About 10,000 degrees Fahrenheit on the surface and about 27 million degrees at its core
