According to the Indian Express, there are only 2-5 solar eclipses per year, and only 1 total solar eclipse every 1.5 years. However, that is the number for the entire Earth. If we only count at any single location (for example, a specific city), the Royal Greenwich Museum says the probability drops sharply to 1 in 400 years. Why is this eclipse so rare?
How does a solar eclipse happen?
A solar eclipse occurs when the Moon moves between the Earth and the Sun. The Moon blocks some or all of the Sun's light, casting a large shadow over some parts of Earth.
There are four different types of solar eclipses, including total solar eclipses, annular solar eclipses, partial solar eclipses, and hybrid solar eclipses.
A solar eclipse occurs when the Moon passes between the Earth and the Sun, forming a straight line between the three celestial bodies. (Photo: Times Now)
When the Moon completely covers the Sun, the areas in the center of the Moon's shadow at that moment witness a total solar eclipse. The sky darkens and those in the area of totality can only catch a glimpse of the Sun's outer ring or corona - which is not visible under normal conditions.
When the Moon blocks the Sun but is far from Earth, an annular solar eclipse occurs. In this scenario, only the center of the Sun is obscured, leaving the periphery, which resembles a ring of fire, unobstructed.
A partial solar eclipse occurs when the Moon covers part of the Sun, causing it to appear as a crescent. In both partial and annular solar eclipses, areas outside the area covered by the Moon's shadow (umbra) (the darkest part of the Moon's shadow) will see a partial eclipse. Partial solar eclipses are the most common type of solar eclipse.
A hybrid eclipse — the rarest type of eclipse — occurs when the eclipse switches between annular and total as the Moon's shadow moves across the globe. In this case, some parts of the world see a total eclipse, while others see an annular eclipse.
How rare is a solar eclipse?
Solar eclipses only occur during a new moon (the first or last day of a lunar month) — when the Moon and the Sun are aligned on the same side of the Earth. New moons occur about every 29.5 days because that's how long it takes the Moon to orbit the Earth. However, solar eclipses don't occur every month, but only two to five times a year. But why?
That's because the Moon doesn't orbit the Earth in the same plane that Earth orbits the Sun. In fact, the Moon is tilted about 5 degrees relative to Earth's ecliptic plane. As a result, most of the time the Moon is between the Sun and Earth, and its shadow is either too high or too low to fall on Earth.
The intersection of the plane along which the Moon orbits the Earth and the plane along which the Earth orbits the Sun is called a "node." When a new moon falls on one of these nodes, a solar eclipse can occur. (Photo: Cosmos Blog)
In other words, if you think of the Earth's orbit around the Sun as one disk and the Moon's orbit around the Earth as another disk, there is an angle of 5 degrees between the two disks. However, there is still a straight line that intersects the two planes created by these two disks. Whenever a new moon crosses this line, there is a chance of a solar eclipse.
Why is this year's total solar eclipse so rare?
While there may be 2 to 5 solar eclipses per year, a total solar eclipse only occurs about once every 18 months. As mentioned earlier, a particular location on Earth experiences a total solar eclipse only once every 400 years.
This is because a total solar eclipse can only be seen if one is standing within the Moon's umbra, while a partial eclipse is only visible if one is standing within the penumbra. The umbra is very small, covering only a small portion of the Earth's surface. In fact, the entire path of the umbra during a solar eclipse will cover less than 1% of the Earth's surface. This is why only a very small number of people can see a total solar eclipse each time it occurs.
The path of a total solar eclipse covers only a very small area of the Earth's surface. (Photo: CTV News).
Not to mention that about 70% of the Earth's surface is underwater and half of its land area is considered uninhabited. Therefore, this total solar eclipse (covering an area home to more than 30 million people) is extremely rare.
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