Solar Eclipse 101 | National Geographic

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solar

eclipse

occurs when a new moon moves between the Earth and the sun, blocking some or all of the sun's rays from reaching the Earth. By cosmic happenstance, although the Sun is 400 times wider than the Moon, it is also 400 times farther away. Therefore, the two objects appear the same size in our sky. Astronomers can predict

eclipse

s because the Earth and Moon have very predictable orbits. Why then isn't there an eclipse every month? The Moon's orbit is typically tilted a few degrees north or south relative to Earth. When the Moon eclipses the Sun, it casts two types of shadows on Earth: a smaller, darker shadow, known as the umbra, and a larger shadow, known as the penumbra.

There are four types of

solar

eclipses. The first and most spectacular is a total eclipse, when the moon completely covers the surface of the sun. You can only see a total eclipse if you are standing within the threshold shadow. That is why the imaginary line created by this shadow as it travels across the Earth is known as the path of totality. People inside the penumbral shadow see only a partial eclipse, the second type. From this view, outside the path of totality, the Moon passes in front of the Sun off-center, without ever completely covering its surface. Third, an annular eclipse occurs when the Moon passes directly in front of the Sun.

However, unlike a total eclipse, the moon appears too small to completely cover the sun. The Moon's orbit is elliptical, so sometimes it is closer to Earth and sometimes farther away. Finally, a hybrid eclipse occurs when the Moon's position between the Earth and the Sun is so finely balanced that the curvature of the Earth plays a role. The Moon will be further away from some parts of Earth along the eclipse path, resulting in an annular eclipse. Elsewhere, the moon will be close enough to completely cover the sun, resulting in a total eclipse. While a total solar eclipse occurs somewhere on Earth every one to two years, any point on Earth experiences the event only once every 400 years. (high-pitched hum) (static crackles) We interrupt this video to make an important safety announcement.

Looking directly at the sun, even during an eclipse, can cause permanent eye damage. Fortunately, there are ways to enjoy an eclipse safely. The easiest way is to use certified eclipse viewing glasses, which are thousands of times darker in shade than typical sunglasses. You can also watch the eclipse indirectly by making a pinhole viewer. Simply make a small hole in a piece of cardboard. Hold the cardboard toward the sun, allowing the image of the sun to be projected onto a flat surface. Be sure to look only at the surface and not through the cardboard. Just before the moon completely covers the sun, the low valleys at the edge of the moon will be the only points through which sunlight will continue to pass.

These remaining bright rays of light, known as Baily beads, will disappear one after another. And finally, a single bead of light remains, known as the Diamond Ring, indicating that you are just seconds away from experiencing totality. Once the last bead disappears and the moon completely covers the surface of the sun, the view through your eclipse glasses will be completely black. Totality achieved. At this point, none of the sun's rays reach your eyes and this is the only time it is safe to remove your glasses. Remember to put your eclipse glasses back on before the sun's rays start to peek through again.

Any sunlight that hits your eyes, even for a few seconds, can cause serious damage. While an eclipse can last a few hours, totality typically occurs for less than three minutes. Animals and plants are also known to alter their behavior during a total eclipse. Songbirds may stop singing, crickets may start chirping, and flowers may even begin to close. We will not always be able to see total solar eclipses. The moon moves about an inch and a half away from Earth each year. It is estimated that in about a billion years the Moon will be too far from the Earth to completely cover the Sun. (elegant music)