What Is a Solar Eclipse?

Kate Russo's life changed on August 11, 1999, while traveling in France. It was the first time she saw the sun disappear behind the moon. This total solar eclipse was such an amazing sight that Kate decided to spend her life studying, writing about, and chasing solar eclipses around the world.

The sun doesn't really disappear during a total solar eclipse. It just looks like it does. During a solar eclipse, the sun, moon, and earth line up, and the moon casts a shadow on a part of the earth. The dark round shape of the moon passes over the brightness of the sun. The sun seems to grow smaller until it is black, surrounded by a halo of light. On earth, everything in the shadow of the moon goes dark for a few minutes. Then, the sun begins to emerge as the moon moves away.

Solar eclipses happen often, but the chances of seeing an eclipse more than once in the same location occurs only every three hundred to four hundred years. And they are not always viewable over land. Sometimes eclipses can only be seen over the ocean or in areas where few people live. But that doesn't stop an eclipse chaser like Kate Russo, who once traveled by boat far into the Pacific Ocean just to see an eclipse. Eclipse chasers are also known as umbraphiles (say: UM-­bruh-­files), which means "shadow lovers."

Scientists can predict when eclipses will happen. So umbraphiles know where and when to watch them. They plan trips to be in the right place at the right time to get the best view. They visit islands and climb up mountains. They go to the hot desert and the freezing Arctic. If an eclipse occurs over the ocean, they take cruise ships. If bad weather is predicted, they take airplanes to see the sky from above the clouds.

Why are umbraphiles willing to travel so far for an experience that lasts only a few minutes? Because they like the way it makes them feel! Eclipse chasers have described watching these events as magical and mysterious, beautiful, powerful, and exciting. It gives them goose bumps. Umbraphiles may bring along special cameras and viewing equipment. But they also treat the eclipse as a celebration. People from all over the world meet up and share in the event. Some have traditions: One viewer always wears orange pants. Another brings a special flag. And another brings along the same teddy bear! The experience can be simply awesome.

You don't have to be an umbraphile to enjoy watching an eclipse. You might live close enough to the path of one. And you might be able to travel to see one. Some communities host eclipse parties when they are in the eclipse's path. They gather in backyards, schools, parks, campgrounds, beaches, and stadiums. And almost everyone can watch an eclipse over live streams on their computers or television.

Through experiments and observations, scientists learn more about the sun, the moon, and the earth itself by watching solar eclipses. Nonscientists come together to wonder about space and to try to observe all the fascinating ways the solar system moves, too. Solar eclipses are a thrill to see.
 
Chapter 1
History of Eclipses
 
Thousands of years ago, people wondered about many things they saw in the sky. They did not have telescopes, spacecraft, or other technologies that we have today. They could not use science to explain what they saw. They used stories instead.

The sun is important for life. It gives light and heat. It helps plants grow. Imagine how scary it would have been if the sun suddenly seemed to disappear! All over the world, ancient cultures created legends to explain eclipses. They told of monsters stealing the sun's light. In ancient Chinese stories, a dragon devoured the sun. In India, the demon Rahu swallowed it. Egyptians thought that a serpent from the Nile River leaped into the sky and swallowed their sun god, Ra. There are stories that describe wolves, birds, bears, and other creatures eating the sun. To scare these enemies away, people made noise by yelling and banging on drums. They shot arrows and threw stones into the sky. Today, we know that eclipses are caused by the way the sun, earth, and moon move. But in the past, people saw eclipses as dangerous, and they worried for their lives.

Some cultures thought that eclipses were punishment from their gods. They thought the fog, dew, or rain after an eclipse would bring sickness. So they covered their wells, stayed inside, and did not drink water for days. During a battle between two kingdoms, near what is now Turkey, an eclipse darkened the sky. The soldiers put down their weapons, and the kings signed a treaty to end the war. To them, the eclipse seemed to be far more of a threat than any amount of fighting.

Other cultures had more romantic ideas. In Germany, they believed that the sun and the moon were married. Since the sun came out during the day, and the moon at night, the eclipse was the only time they could be together.

Early astronomers tried to understand more about the moon and sun. About five thousand years ago, people built stone structures related to the objects they saw in the sky. Stonehenge is an arrangement of giant rocks in England. The stones are lined up to mark the movements of the sun and the moon. Another collection of large stones in Ireland, called Loughcrew Cairns, are carved with circle shapes that might be symbols of a solar eclipse. These early structures show that people were noticing patterns in the way the sun and moon traveled across the sky.

As ancient astronomers learned more about the sky and watched the way objects moved over periods of time, they could predict when eclipses would occur. The Babylonians wrote records of eclipses on clay tablets almost four thousand years ago. They noticed that eclipses seemed to happen during certain times of the year, and that they repeated every eighteen years. Ancient Greek, Chinese, and Maya people also recorded and predicted eclipses.

Recording Eclipses Through History
 
Scientists use computers to help them study eclipses and store information about them. But people all over the world have been recording information about eclipses for thousands of years, even before computers existed.

The earliest records of eclipses were pictures carved into rock, like the ones at Loughcrew Cairns in Ireland. These pictures are called petroglyphs. A petroglyph of a possible eclipse has also been found in New Mexico's Chaco Canyon.

In ancient China, observers wrote about eclipses by carving on animal bones. The Greeks wrote on long scrolls made from the papyrus plant. They also created a machine with bronze gears that helped them predict future positions of the sun and moon.

In Central America in the 1200s, the Maya wrote about eclipses in books made of tree fiber. These early astronomers recorded lots of information and predicted future eclipses. They even predicted an eclipse that happened more than seven hundred years later!
 
Over the centuries, astronomers continued to observe. They learned more about the sun, the moon, the earth, and the rest of the planets in our solar system. The invention of the telescope helped make faraway objects appear closer. Scientists developed spacecraft, called probes, to investigate the moon and the sun. High-­powered cameras were designed to take photographs in different types of light. Modern tools like these have taught us a lot about our universe and our solar system, including eclipses.
 
 
Chapter 2
All About the Sun
 
We live in the Milky Way galaxy, a pinwheel-­shaped collection of stars. The sun is one of these billions of stars. Some stars have planets that orbit, or move in a path, around them. Our sun has eight large planets that orbit it. These are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Smaller planets, rocks called asteroids, and chunks of dust and ice called comets also orbit the sun. The sun and all these objects make up our solar system.

Gravity is the pull of one object on another. The sun is the largest object in our solar system. It is more than one hundred times the size of earth. Because it is so large, it has lots of gravitational pull. The gravity keeps the planets and other space objects in orbit around it.

The sun doesn't have a hard surface like earth. It is made up of the gases hydrogen and helium. Hydrogen burns in the center of the sun. It then turns into helium, which gives off light and heat. The temperature in the sun's center can reach more than twenty-­seven million degrees!

The photosphere is the part of the sun that people on earth see as a circle in the sky. It is cooler than the center. But it is the brightest part of the sun. Next comes a reddish layer called the chromosphere. Sometimes hot gases shoot out from the chromosphere. The final layer is the corona. The corona is the outer atmosphere of the sun. It is a mixture of gases and particles that are always speeding away from the sun. This creates a solar wind that spreads out into the whole solar system. People can't often see the chromosphere or corona because the photosphere is so bright.

The sun is about ninety-­three million miles from earth. Earth is the third planet from the sun. Life doesn't exist on the other planets. Some are too close to the sun, others too far away. Earth is just right. The sun is the source of that power (both heat and light) that supports plants, animals, and people.

It takes earth one year to orbit the sun. The earth is tilted as it orbits. This tilt causes seasons on earth. When the top half of earth is tilted closer to the sun, it has summer, and the bottom half of the earth has winter. When the bottom half is tilted closer, it has summer, and the top half has winter.

From earth, the sun seems to rise and set in the sky. That's because the earth is always rotating, or spinning, on its axis. The sun shines on only half of the earth at a time. It takes about twenty-­four hours for the earth to make one full turn. It is daytime on the side facing the sun. The other half of earth facing away is in shadow and has night. As the planet spins, the sun seems to travel across the sky during the day and disappear at night for those viewing it from earth.

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Excerpted from What Is a Solar Eclipse? by Dana Meachen Rau, Who HQ
All rights reserved by the original copyright owners. Excerpts are provided for display purposes only and may not be reproduced, reprinted or distributed without the written permission of the publisher.