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This blog is an exciting new venture of the NSS of IIT Madras to create a magazine, which would cover topics in the realm of Sciences and Social Sciences, an aid for the students of classes VIII-XII. Our vision is to complement the student's academics with creative, coherent and concise inputs while creating an awareness about socio-political issues.

Eclipses

Eclipse is a astronomical phenomenon that occurs when an astronomical object is temporarily obscured, either by passing into the shadow of another body or by having another body pass between it and the viewer.
Eclipse is a derived from a greek word and means "to abandon", "to darken"


We observe two types of eclipse:

SOLAR ECLIPSE

As seen from the Earth, a solar eclipse occurs when the Moon passes between the Sun and the Earth, and the Moon fully or partially blocks the Sun. This can happen only during a new moon, when the Sun and the Moon are in conjunction as seen from Earth.


LUNAR ECLIPSE

A lunar eclipse occurs when the Moon passes behind the Earth so that the Earth blocks the Sun's rays from striking the Moon. This can occur only when the Sun, Earth, and Moon are aligned exactly, or very closely so, with the Earth in the middle. Hence, a lunar eclipse can only occur the night of a full moon.

 
We will discuss both lunar and Solar eclipse in a bit detail below.
 UMBRA AND PENUMBRA:
If the light source is a point, then all objects will have one kind of shadow behind them. But if the light source is a sphere (like the sun), then every object has behind it a core shadow called as the umbra and a sort of side-way shadow called as the penumbra.


LUNAR ECLIPSE:

 

Lunar eclipse occurs when earth is between sun and the moon and earth’s shadow falls on the moon.
An eclipse of the Moon or lunar eclipse can only occur at Full Moon and only if the Moon passes through some portion of Earth's shadow. That shadow is actually composed of two cone-shaped components, one nested inside the other. The outer or penumbral shadow is a zone where the Earth blocks part but not all of the Sun's rays from reaching the Moon. In contrast, the inner or umbral shadow is a region where the Earth blocks all direct sunlight from reaching the Moon.     
There are three basic types of lunar eclipse:
  1. Penumbral Lunar Eclipse
  • The Moon passes through Earth's penumbral shadow.
  • These events are subtle and hard to observe.
  1. Partial Lunar Eclipse
  • A portion of the Moon passes through Earth's umbrae shadow.
  • These events are easy to see, even with the naked eye.
  1. Total Lunar Eclipse
  • The entire Moon passes through umbra of the Earth’s shadow.
  • These events are quite striking due to the Moon's vibrant red colour during the total phase.
Total Lunar Eclipse is the most fascinating phenomenon as the moon appears red and looks more beautiful. But how do you know how this happens?
-It is because of the air we breathe. If there would have been no atmosphere on the Earth then the moon would have appeared black.
But because of the atmosphere on the Earth the sunlight falling on earth gets scattered into its respective constituent colours among which red light scatters the least and falls on the moon.


SOLAR ECLIPSE:




Solar eclipse occurs when moon is in between sun and earth and moon’s shadow falls on the earth    
An eclipse of the Sun (or solar eclipse) can only occur at New Moon when the Moon passes between Earth and Sun. If the Moon's shadow happens to fall upon Earth's surface at that time, we see some portion of the Sun's disk covered or 'eclipsed' by the Moon. Since New Moon occurs every 29 1/2 days, you might think that we should have a solar eclipse about once a month. Unfortunately, this doesn't happen because the Moon's orbit around Earth is tilted 5 degrees to Earth's orbit around the Sun. As a result, the Moon's shadow usually misses Earth as it passes above or below our planet at New Moon. At least twice a year, the geometry lines up just right so that some part of the Moon's shadow falls on Earth's surface and an eclipse of the Sun is seen from that region.
There are three types of solar eclipse:


        1. Partial Solar Eclipse
When the Moon's penumbral shadow strikes Earth, we see a partial eclipse of the Sun from that region. Partial eclipses are dangerous to look at because the un-eclipsed part of the Sun is still very bright. You must use special filters or a home-made pinhole projector to safely watch a partial eclipse of the Sun.


                                              2.       Total Solar Eclipse

If the Moon's inner or umbral shadow sweeps across Earth's surface, then a total eclipse of the Sun is seen. The track of the Moon's umbral shadow across Earth is called the Path of Totality. It is typically 10,000 miles long but only about 100 miles wide. It covers less than 1% of Earth's entire surface area. In order to see the Sun become completely eclipsed by the Moon, you must be somewhere inside the narrow path of totality. The path of a total eclipse can cross any part of Earth.
        1. Annual Solar Eclipse

Sometimes Moon is not able to cover all the sun. If an eclipse occurs while the Moon is on the far side of its orbit, the Moon appears smaller than the Sun and can't completely cover it. Looking down from space, we would see that the Moon's umbral shadow is not long enough to reach Earth. Thus we see the annular solar eclipse. Annularity can last as long as a dozen minutes, but is more typically about half that length. Since the annular phase is so bright, the Sun's gorgeous corona remains hidden from view. But annular eclipses are still quite interesting to watch.



-         Article done by Akshay Nemande


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