LUNAR ECLIPSE: A GRAND CELESTIAL EVENT
Theory
A Lunar Eclipse is a rare celestial phenomenon that occurs when the Earth's shadow falls upon the Moon. This occurs when the Earth lies between the Sun and the Moon in a straight line. This happens only on a full-moon day. However, we don’t see a lunar eclipse on all full-moon days; because the three celestial bodies i.e. the Sun, the Earth and the Moon don’t always lie along a straight line although they remain along a single plane. This is due to the tilt of the Moon’s orbit with respect to the Earth’s orbit (called the Elliptic) by an angle of 5 degrees. Hence, we see a lunar eclipse on some special full-moon days. When these three bodies are aligned in a straight line, the lunar eclipse is visible. This makes a lunar eclipse a rare celestial event.
How a Lunar Eclipse is different from a Solar Eclipse
A lunar eclipse is different from a Solar eclipse in many ways. First, unlike a Solar Eclipse, the Moon never vanishes completely during the total Lunar Eclipse. This is because of the fact that some higher wavelength red rays from the Sun are bent in the Earth’s atmosphere due to refraction and are able to reach the Moon. Hence, during a total lunar eclipse, the Moon looks dimmer and redder. This Moon is popularly called the Blood Moon. Second, unlike a solar eclipse which is visible only to a particular belt on the Earth, a lunar eclipse is visible to all the places on Earth, provided that it is nighttime prevailing there. Thirdly, unlike a Solar eclipse, the eclipse of the Moon lasts for a much longer period because of the larger size of the Earth's shadow at the Moon's distance which makes the Moon take a considerable time to emerge from the Earth's shadow. Fourthly, a lunar eclipse begins by obstruction from the eastern side of the Moon unlike a solar eclipse which first obstructs the western part of the Moon.
Observation
Unlike a Solar eclipse, the eclipse of the Moon can be seen directly through the naked eye without having any optical aid. However, for the best viewing conditions, we should use binoculars or a telescope and move to an area away from bright lights.
Types of Lunar Eclipse:
There are primarily three types of lunar eclipses: the Penumbral eclipse, the Partial Eclipse and the Total Eclipse. In a Penumbral eclipse, the Moon passes through the Earth's penumbra, the lighter part of the Earth's shadow. The penumbra causes a subtle dimming of the lunar surface, which is only visible to the naked eye when about 70% of the Moon's diameter has immersed into Earth's penumbra. A Partial eclipse, on the other hand, occurs when a portion of the Moon enters the Earth's umbra, the darker part of the shadow. However, in a Total lunar eclipse, the Moon is totally engulfed in the umbral portion of the Earth's shadow. The Moon's average orbital speed is about 1.03 km/s which is a little more than its diameter per hour, so totality may last up to nearly 107 minutes. Nevertheless, the total time between the first and the last contacts of the Moon's limb with Earth's shadow is much longer and could last up to 236 minutes.
Myths and Legends
In our Indian mythology, it is believed that a hungry demon named Rahu swallows the Moon during a lunar eclipse. The Chinese believe that a dragon used to eat away the Moon during the eclipse. Some natives of the Pacific islands believe that wild animals like the wolf or the dog used to eat away the Moon in the sky during an eclipse. So they used to beat drums and shoot arrows at the sky to drive away these animals. The Incans believed that lunar eclipses occurred when a jaguar ate the moon, which is why a blood moon looks red. They also believed that once the jaguar finished eating the Moon, it could come down and devour all the animals on Earth, so they used to take spears and shout at the Moon to keep it away. The ancient Mesopotamians believed that a lunar eclipse occurs when the Moon was being attacked by seven demons. The seven demons were thought to be also attacking their king who represented the land. In order to prevent this attack on the king, the Mesopotamians made someone pretend to be the king so they would be attacked instead of the true king. After the lunar eclipse was over, the substitute king was made to disappear. However, the ancient Greeks correctly believed that the Earth casts a shadow on the Moon and, from its round shadow, they concluded that the Earth was round.
Eclipse in Culture
People used to observe penance and fasting during the eclipse as it is believed that the food cooked during the eclipse turns toxic which is unhygienic. Pregnant women are advised to stay indoors in the belief of the harmful impacts of the eclipsed rays on the unborn baby. People are also advised not to embark on distant journeys during the eclipse. Rituals of deities in temples are altered due to the eclipse. People used to take baths and offer puja in temples after the eclipse. Even, the Govt. of Odisha used to declare holiday for schools and colleges on the day of the eclipse. However, these practices have no scientific basis.
Grand celestial spectacles are not generally welcomed in our dogma-dominated society. What is really disturbing is the unchanging mindset of the people even in the light of the convincing scientific evidences put forward to explain these celestial phenomena. It is quite ridiculous to shut oneself indoors when a spectacular and rare natural event is unfolding up in our backyard. We can never shy away from such celestial challenges, but be a part of the drama. We should not only free ourselves from these bizarre beliefs, but also develop a sense of curiosity and scientific mindset to unravel the mystery of nature.
Education Officer
Regional Science Centre
Bhopal
Nicely depicted sir
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