What are Lunar or Moon Eclipses and When do they Occur?
Eclipse is partial or total obstruction of light from a celestial body as it passes through shadow of another celestial body.
A lunar eclipse occurs when the Moon passes behind the Earth and the Earth blocks out the sunlight. Again, remember that an eclipse happens when an object passes through another object's shadow. This shadow consists of two parts: an umbra which is the region of total shadow and the penumbra which is the outer region of partial shadow.
(See: Following Image - Lunar Eclipse Anatomy)
(See: Following Image - Lunar Eclipse Anatomy)
A lunar eclipse does not occur at every full Moon because the Moon’s orbit is tipped 5 degrees to the Earth’s orbit around the sun. This means the moon passes either above or below the Earth’s shadow most of the time.
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| This is Why Eclipse Doesn't Occur Every New Moon (Solar) or Full Moon (Lunar) |
Important Facts on Lunar Eclipse:
- The word eclipse comes from the Greek word meaning downfall.
- There are three types of lunar eclipse: Partial Lunar Eclipse, Penumbral Lunar Eclipse and Total Lunar Eclipse.
- There are about two lunar eclipses each year – there can never be more than three lunar eclipses in a year.
- A lunar eclipse usually lasts for a few hours whereas a solar eclipse typically only lasts for a few minutes. Some lunar eclipse can last up to 3 hour.
- A lunar eclipse can be viewed from anywhere on the night side of the Earth. So, more people on Earth can view a lunar eclipse than a solar eclipse.
- A selenelion or selenelion eclipse occurs when both the Sun and the eclipsed Moon can be seen at the same time. This is sometimes known as a horizontal eclipse because both bodies will appear just above the horizon at nearly opposite points in the sky. This type of eclipse can only occur just before sunset or just after sunrise.
- Lunar and solar eclipses are closely related to each other – when there is a solar eclipse, a lunar eclipse will have occurred 2 weeks beforehand, or it will occur two weeks afterwards.
- The appearance or darkness of the Moon varies during a total lunar eclipse due to the variation in the composition of Earth's atmosphere. The Danjon Scale is a scale used to describe the darkness of a total lunar eclipse. The Danjon Scale has 5 points that range from 0 (Moon appears almost invisible) to 4 (very bright yellowish orange).
- The cycle of eclipses repeats every 18.6 years called the saros.
Interesting Story of Christopher Columbus and the Lunar Eclipse
About 500 years ago, Christopher Columbus was on his fourth voyage to the New World. His earlier voyages were the stuff of legends. Unfortunately there's an end to every good luck streak and on this voyage, bad luck would strike in the form of worms. In the days of wooden boats, worms would attack and bore holes in the wood which eventually would cause leaking and ultimately sinking if repairs were not made. Columbus had no choice but to beach his leaky ship on St. Anne's Bay, Jamaica, and make repairs. Chris and his sailors spent over a year there, most of it waiting for his lieutenant's ship to come and help him.
The local Jamaican natives were quite fascinated with Columbus and his men and were very nice to them. They provided Columbus and his sailors with food and other supplies and helped them build shelters. In fact, the Natives treated Columubs better than his own men treated him. The sailor's on this voyage were a pretty rough bunch and had repeatedly argued with Columbus, coming close to mutiny on several occasions. Unfortunately, the sailors gave no better treatment to the Jamaicans, and took advantage of them whenever they could, even cheating and stealing from the Natives.
The local Jamaican natives were quite fascinated with Columbus and his men and were very nice to them. They provided Columbus and his sailors with food and other supplies and helped them build shelters. In fact, the Natives treated Columubs better than his own men treated him. The sailor's on this voyage were a pretty rough bunch and had repeatedly argued with Columbus, coming close to mutiny on several occasions. Unfortunately, the sailors gave no better treatment to the Jamaicans, and took advantage of them whenever they could, even cheating and stealing from the Natives.
Columbus opened the meeting with a somber announcement, "The Almighty was unhappy, He didn't like the way the natives were treating Columbus and his sailors. The Almighty would now show his disapproval by removing the Moon from the sky." One can only imagine the natives sniggering over this announcement. No one, in their opinion, could control the sky. Shortly thereafter, the full moon began to appear over the eastern horizon. As the Sun set, the full moon rose, and the sniggering probably continued.
Eventually the Natives grew tired of being treated so badly and decided to make a point and cut off the food supply to Columbus and his crew. The sailors were more than willing to try and fight with the natives to get what they wanted and they even argued with Columbus about it. But Chris thought there was a better way to deal with these issues and he asked the native chiefs to attend a meeting with him just before sunset on February 29, 1504.
And then, ever so subtly, the moon began to change. Sniggers were replaced by an uneasiness. The Moon began to dim and turn a blood red colour. Soon all eyes were riveted on the dimming orb. Clearly, as it rose, there was something wrong. Not only was the Moon the colour of blood, by the time the lunar disk was completely above the horizon, the lower half of the Moon was missing!
The natives pleaded with Columbus to return the Moon to its former self. They promised food and anything else Columbus or his men wanted. They begged for forgiveness With high drama, old Chris told the natives he would just nip inside and seek a bit of counsel with the Almighty and see if he was in the forgiving mood. In this particular case, "the Almighty" was most likely an hourglass clever Chris was using to time the 48 minute duration of totality.
Over the next few hours, little by little the Moon became harder and harder to spot. A dim red orb hung in the sky where once the brilliant Moon had bathed them in moonlight. It looked as if the Moon had been reduced to a dim ghost of its former self.
Supposedly, the natives were terrified. It is doubtful that they had never observed a lunar eclipse before, but they likely believed the gods controlled such events, and now, here was a mere human who could not only communicate with the gods but could predict his actions as well! Clearly they were frightened by this display of power.
Strolling casually back out from his ship, Columbus reappeared just before totality ended and announced that the Almighty Power was indeed in a forgiving mood and if the natives would thusly promise to provide food for Columbus and his crew, the Almighty Power would have the Moon reappear. Of course the Natives agreed and with much nodding, smiling and posturing, the deal was sealed and quite soon thereafter, the Moon was its former brilliant self.
Thereafter, it is doubtful that Columbus had much trouble with the Natives. He probably even gained a bit more respect from his sailors but one thing is for sure, Columbus did have a good bit of knowledge from Persian, Greek, Islamic and European science. He reportedly had an almanac which he used to schedule the meeting with the Natives based on eclipse times!
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