Shishu Sansaar | Science
See also List of Eclipses | Eclipses | Solar Eclipse
Eclipse means hiding. So when the Moon is hiding from Earth, it is called Lunar Eclipse.
* Moon appears in
the same location about 50 minutes later each night
Vice versa, a Lunar Eclipse always occurs on Full Moon and when the earth comes in between the Sun and the Moon. Moon revolves around the earth in 29.5 days, and this duration is called a month. The "month" word is derived from the 29.5 day period.
Why do we not have the Lunar Eclipse every Full Moon? In fact the Moon's orbit is 5 degree tilted from the orbit of the earth around the Sun. This means that Moon spends its most of the time either above or below of the earth orbit plane. To have a Lunar Eclipse, plane of earth's orbit around the Sun is important, because Earth's shadows lie exactly in the same plane. During the Full Moon day, it passes either above or the below the Earth's shadows so it misses them entirely. But 2-4 times each year, the Moon passes through some portion of the Earth's shadows, and a Lunar Eclipse occurs. It may be Penumbral (this is for academic interest only and they are 35% of all the Lunar Eclipses and are difficult to see), partial or total.
When a Lunar Eclipse occurs, everyone who is on the night side of the Earth can see it. During the total Lunar Eclipse, the Earth blocks the sunlight completely reaching to the Moon, but still some indirect sunlight manages to reach the Moon and illuminates it. This light is deep red or orange in color and is much dimmer than pure white sunlight. Earth's atmosphere also helps to reach there. The total Eclipse is so interesting and beautiful to see because of this light only. If Earth had no atmosphere, the Moon should have been totally black on this total eclipse day. The colors depend on the earth's atmosphere. If there is lots of dust in the atmosphere, the Moon should look dark.
An Eclipse of the Moon can only take place on Full Moon, and only if the Moon passes through some portion of Earth's shadow. The shadow is actually composed of two cone-shaped parts, one nested inside the other. The outer shadow or penumbra is a zone where Earth blocks some (but not all) of the Sun's rays. In contrast, the inner shadow or umbra is a region where Earth blocks all direct sunlight from reaching the Moon.
If only part of the Moon passes through the umbra, a partial Eclipse is seen. However, if the entire Moon passes through the umbral shadow, then a total Eclipse of the Moon occurs.
Unlike Solar Eclipses, Lunar Eclipses are safe to watch, you don't need even the telescope. Lunar eclipse photography is interesting. Go to these sites for more information -
Some Facts About Lunar Eclipse
(1) The cause of Lunar Eclipse is simple - The Moon is a shiny beacon because it reflects sunlight, it has no light of its own. On the other side, the Earth always casts its shadow in the space and every now and then something aligns to it. When the Moon aligns in such a way that the shadow of the Earth falls on it, on whatever part it falls remains un-shiny and dark. If, anytime the Moon is so aligned that the Earth's shadow coves it fully, it is called Total Lunar Eclipse. Lunar Eclipse can occur only on Full Moon's day, that time each month hen the Moon is directly opposite to the Earth in relation to the Sun.
(2) Why doesn't it occur each month? - Now you will ask if it occurs on Full Moon's Day then Full Moon come every month, then why doesn't it occur every month? In fact eclipses are a rear event, because the plane in which the Moon orbits around Earth is tilted 5 deg, compared to the plane of Earth's travels around the Sun. These planes, as astronomers call them, ecliptic (ecliptic word has stemmed out of Eclipse).
The geometry of any Eclipse - the relative position of the Sun, Earth and Moon, is eventually repeated during a complex set of cycles; that each cycle lasts for just more than 18 years. This Eclipse cycle is the background of occurring Eclipse. The astronomers have figured it out, and so they can predict the day and time long before its occurrence.
(3) It is really strange that Lunar Eclipses are less frequent than its counterpart Solar Eclipse. Solar Eclipses are fairly numerous, generally 2-5 per year, but the area covered on the ground is covered is very less - a few tens of miles, that is why Lunar Eclipse is rarely in the path of Solar Eclipse. In any given location on Earth, a total Solar Eclipse happens only once in 360 years. While Lunar Eclipses happen less frequent, but the total Lunar eclipses can be seen from everywhere, because they happen at nighttime and night is always around half the globe. Any given location can see up to three Lunar Eclipses per year - as last happened in 1982; and in some years there are none as in both 2005 and 2006.
(4) It is interesting to note that the Lunar Eclipse can be seen even from the Moon itself. If you were there on the Moon, facing Earth, the Earth would black out the Sun, but the Sun's light would not completely disappear. Earth would be ringed by the light scattered through te atmosphere. Understand it in this way that - the Sun would be hidden behind a dark Earth outlined by a brilliant red ring consisting of all the world's sunrises and sunsets.
(5) How people take
the Eclipse? - For ancient people eclipses were the signs of God's wrath that
were the precursors of the famines and diseases.
(6) Timings of Eclipses - Columbus knew that Eclipses do not take for ever. Astronomers say that no Eclipse can last more than 3 hours and 40 minutes. Totality (when the Moon has totally immersed behind the shadow of the Earth) cannot run more than 1 hour and 40 minutes. The period of totality of Moon Eclipse of 27th October 2004 was 1 hour and 22 minutes, the period of totality of the Moon Eclipse of 8th November 2003 was only 25 minutes. Why is such a difference?
Earth's shadow is cone-shaped. So imagine a slice of it - a two-dimensional circle through which the Moon can pass. Longer stretches of the shadow means the Moon is passing the center of the circle. Shorter total eclipse occurs when the Moon path is nearer to the top or the bottom of the shadow.
(7) One Day the Moon Eclipse Won't Occur - Currently the Mon is moving away from Earth about 1.6 inches (4 cms) every year. We happen to stand on this planet until the Moon appears as the same size as of the Sun. The Moon's actual diameter is much less than the Sun, but it is much closer to us. That is why, a total Lunar Eclipse won't be geometrically possible, just as it was not possible in the distant past when Moon was nearer to us.
Created by Sushma Gupta on January 15, 2002
Modified on 09/23/13