Solar Eclipse

Eclipse means hiding. Thus in solar eclipse, the Sun is hidden from our eyes, and in 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.

1. Solar eclipse is always on New Moon day, and lunar eclipse is always on Full Moon day.
2. Both the eclipses cannot be seen alike at all the places on the earth.
3. Since the solar eclipse 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 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 solar eclipse which may last up to 7.5 minutes
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 every six months. This holds true for 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.

Solar Eclipse

Solar eclipse always occurs on New Moon day, but it does not occur on every New Moon day. It occurs only when the Moon comes between the Sun and the earth and covers the Sun blocking the rays of the Sun reaching the earth and casts its shadow on the earth. In fact, two different cycles of the Moon affect the solar eclipse - one is its monthly cycle so the Sun is hidden from our eyes on New Moon day, and the other is gradual shift in orientation of the Moon's orbit. Only when these two are favorably combines then only can a solar eclipse occur.

Type of Solar Eclipse - There are mainly two types of solar eclipse - total, and partial. Partial eclipse may be of two types - one in which the Sun is hidden only partially, two in which the Sun is also hidden partially but its apparent diameter can be seen against the shadow fallen on it. This is called Annular eclipse. Any solar eclipse can of all the three types for different observers. 

Total solar eclipse is rare, so if you get an opportunity to look at it, never miss it, it is really interesting to see and experience a total solar eclipse. To see a total solar eclipse you have to be in the path of totality, and this path, sometimes 200 miles wide, never covers more than roughly 1/2% of the 1% area of the whole earth and often traverses upon seas or remote regions of the planet. Only fewer than 70 total solar eclipses occur in a century - this makes a chance for seeing a total solar eclipse for most of us only once in lifetime. 

DON'T FORGET TO USE SUNGLASSES WHILE LOOKING AT A SOLAR ECLIPSE

It is quite remarkable that the total eclipse occurs at all. The Sun whose size 400 times larger than that of the Moon, happens to be about 400 times as far away from the earth. This condition permits just barely cover up the Sun. In fact, if the Moon's diameter (2,160 miles or 3,476 Kilometers) were just 140 miles (224 Kilometers) shorter than this, it could have never caused the total solar eclipse.

When Does It Occur? - For a solar eclipse to occur, the New Moon must be close enough to the ecliptic plane so that its shadow can touch at least some parts of the earth.  When the New Moon appears within 18-3/4 days before or after the alignment of a node (nodes are the two points where the Moon's orbit intersects the plane of the Earth's orbit) a solar eclipse will take place. This creates a 37-1/2 day time gap for eclipses when the conditions are favorable for an eclipse to occur.

If the lunar nodes are stationary with respect to the stars, each node would be lined up between the earth and the Sun at the same time each year, the eclipses would have occurred at the same time each year - every six month. But this is not so, because the nodes of the lunar orbits shift their orientation gradually. Since the Moon's orbit is tilted 5 degree from the earth's orbit, normally it passes either below or above the line between the Sun and the earth. It is only about every 6 months the conditions are favorable for any eclipse.

This alignment happens 18.6 days sooner than if the nodes have not been shifting, creating the shorter eclipse year (normal eclipse year = 346.6 days). This phenomenon determines  the pattern of eclipses. This change makes it happen earlier and earlier than before.

How Often It Occurs? - The repetition of eclipses follows a very regular pattern in time. Partial phases of solar eclipse can be seen about every 2-1/2 years from any particular spot on the earth. The best estimate for total eclipses is that they recur at the same location about every 360 years on the average. But sometimes this average varies widely, for example, London has never seen total eclipse for 837 years (878 to 1715); while Angola coast witnessed almost 5 minutes total eclipse on June 21, 2001, and then on December 4, 2002 for 2 minutes.

There will be 18 solar eclipses between 1996 and 2020. The common perception that the eclipses are infrequent is because the observation of a total eclipse from a given point of the earth is not common, for example, it will be two decades before the next total solar eclipse will be visible in North America. The last total solar eclipse was on August 11, 1999.