Anyone who has ever seen a total eclipse of the sun has been awed by the experience. During such an event day turns to night as the moon passes between the sun and the Earth, blocking the sun from the view of observers on Earth. This is called a solar eclipse. In general, an eclipse occurs whenever three objects in the sky line up in a row. The most familiar eclipses involve the sun, the moon, and the Earth, but they can involve other celestial bodies as well. In ancient times, solar eclipses inspired tremendous fear and wonder. People did not understand why the skies sometimes darkened in the middle of the day. They believed that the sun had abandoned the Earth. Thus the word eclipse, which comes from Greek words meaning “to leave,” was used to describe this event. Today, most people understand that an eclipse is simply a scientific event that can be explained. How eclipses occurPlanets and other celestial bodies are constantly moving through space. The Earth travels around the sun in a path known as its orbit. As the Earth is moving around the sun, the moon is making its own orbit around the Earth. The same thing occurs with the other planets. As these bodies keep moving, they sometimes cross each other's paths. An eclipse occurs when one body moves in front of another, partially hiding the first body from the view of an observer on a third body. In a solar eclipse the Earth, moon, and sun form a line with the sun at one end, the Earth at the other end, and the moon in the middle. When this occurs, some or all of the sun's light is blocked from reaching the Earth. When the three bodies line up with the Earth in the middle the event is known as a lunar eclipse because it affects the view of the moon. Scientists use two other terms to describe variations on this idea. One of these is occultation. When a small body such as a moon moves behind a much bigger body so that the smaller body seems to disappear altogether, this is called occultation. On the other hand, when a small body passes in front of a much bigger body this is known as a transit. Solar eclipses - During an eclipse of the sun, the shadow of the moon sweeps over the surface of the Earth. In the …
If the sun, Earth, and moon line up in a perfectly straight line, then the sun's light is blocked completely. This is called a total eclipse. As the moon moves in front of the sun, the sky grows gradually darker. Finally the moon moves into position, blocking out the sun's light completely. This moment is called totality. At this moment the moon appears as a perfectly round black circle with what appears to be a ring of fire around it. This ring is the sun's corona—the rays that surround the sun's body. Totality lasts for only a few minutes. The moon slowly moves out of position and the sun's body begins to peek out from behind. The sky gradually lightens, and soon everything looks as it did before the eclipse began. Total eclipses are spectacular, but it is unlikely that a person will view more than one in a lifetime. This is because eclipses, especially the moment of totality, are not visible from every point on Earth. After an eclipse is viewed at a given point, it could be as long as 400 years before another one appears over that same area. This explains why many people travel great distances to view an eclipse. A partial solar eclipse is similar in most ways to a total eclipse. The main difference is that in a partial eclipse, the moon does not completely block out the sun. Like total eclipses, partial solar eclipses are only visible from certain points on the Earth. Lunar eclipses - During a lunar eclipse the moon, revolving in its orbit around the Earth, passes through the shadow …
Lunar eclipses only occur when the moon is full. During a lunar eclipse, the sun, Earth, and moon once again line up. This time, however, the Earth is in the middle position between the moon and Sun. When this occurs, the Earth blocks the sun's light from reaching the moon. This causes the Earth's shadow to be cast onto the moon. The light of the moon that is normally visible is actually the reflection of the sun on the moon's surface. Thus it stands to reason that if something were to move into a position that blocked that light, its shadow would be cast onto the moon. As the moon moves into position in the Earth's shadow, the moonlight becomes increasingly dimmed. During a lunar eclipse the moon does not become completely dark. Instead, it takes on a glow that ranges in color from orange to copper to deep red. Like solar eclipses, lunar eclipses can be total or partial. Unlike solar eclipses, however, the difference between a total and partial lunar eclipse is not very great. Furthermore, lunar eclipses are visible from any point on Earth where the moon has risen above the horizon. If the moon is visible then the eclipse is visible. Safety when viewing an eclipseLooking directly at a solar eclipse is extremely dangerous and should never be attempted. The powerful rays from the eclipsing sun will burn the eyes, causing serious and permanent damage. Wearing sunglasses, or trying to view the event through exposed film or smoked glass is also dangerous, as these items offer no true protection. Solar eclipses should only be viewed through special devices that allow the viewer to see the event indirectly. Lunar eclipses are completely safe to view with the naked eye. History of observationBecause eclipses are a natural event, they have been occurring for as long as the universe has existed. However the earliest recorded mention of an eclipse dates only to about 2000 BC. Documents from Mesopotamia in the Middle East, ancient China, Greece, and Rome all mention eclipses of various kinds. In some cases the eclipses caused alarm. In others, the people saw the event as a good sign. An eclipse of the moon in June of the year 168 BC was one such case. The Romans were at that time at war with Macedonia. A document from the time says that this eclipse was seen as an omen, or sign of the eclipse of a king. The Romans thought the Macedonian king would be overtaken, therefore the eclipse encouraged the Romans and discouraged the Macedonians. Some observers in ancient times realized that eclipses were natural events. They studied the eclipses to learn about the movement of the moon, the sun, and other bodies in space. These observers were some of the earliest people to practice the science of astronomy. |