Shishu Sansaar | Science
See also List of Eclipses | Lunar Eclipse | Solar Eclipse
Eclipse means hiding. Thus in solar eclipse, the Sun is hidden from our eyes, and in the lunar eclipse the Moon is hidden from our eyes. What is the reason of their hiding on certain days? There are some facts about them which one should know ---
(1) Solar Eclipse is always on a New Moon day, and Lunar Eclipse is always on a Full Moon day.
(2) Both the Eclipses cannot be seen alike at all the places on the Earth.
(3) Since the Eclipses are the results of periodic motion of the Moon round the Earth, there are regularities in the timing of the Eclipses that give cycles to the related eclipses. These cycles can predict the future Eclipses.
(4) Although both Eclipses are with comparable frequencies, the Lunar Eclipse's frequency is more than the Solar one. It is because the darkened Moon can be seen from anywhere in the nighttime.
(5) A Lunar Eclipse can be seen by more people than the Solar Eclipse.
(6). A Lunar eclipse can last up to 3.5 hours, as opposed to the Solar Eclipse which may last only up to 7.5 minutes. So why the period of solar eclipse is lesser than lunar eclipse? Because of the speed at which Earth moves around the Sun. It is impossible for a Solar Eclipse to last more than 7 minutes and 58 seconds - in short more than ten minutes. So if the Eclipse time is told more - either it is wrongly reported, or it is not the Solar eclipse but the Lunar Eclipse. 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.
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) While the Moon is always in a new phase during a Solar Eclipse, a Solar Eclipse does not occur every time the Moon is in the new phase. This is because the orbit of the Moon is tilted relative to the Earth's orbit around the Sun. This tilt is only 5 degrees, but it is enough that the alignment of the Earth, Moon, and Sun only occurs about once in every six months. This holds true for the Lunar Eclipses as well. In fact, Lunar and Solar Eclipses generally occur together; that is, if the alignment is correct for a Lunar Eclipse during the full phase of the Moon, it will also be correct for a Solar Eclipse during the next new phase of the Moon.
(8) Unlike Solar Eclipses, Lunar Eclipses are safe to watch, you don't need even the telescope. Lunar eclipse photography is interesting.
As per the Ved, Rishi
Atri is probably the earliest astronomer who speaks about an Eclipse.
Created by Sushma Gupta on January 15, 2002
Modified on 09/23/13