Why solar
eclipses ?
Why will you only see
one or two in your lifetime?
While the sun is about 400 times larger than the moon, it is also conveniently about 400 times farther from Earth. This natural coincidence results in the discs of the two celestial bodies having nearly identical apparent dimensions when viewed from Earth, allowing us to experience perfectly total solar eclipses.
The moon is Earth's natural satellite, orbiting around it and completing one full orbit in about 27 days. Regularly, the moon positions itself between the earth and the sun, marking the time of the new moon. As the earth is also in motion, orbiting around the sun, it takes about 29 days for the moon to return between Earth and the sun. When the alignment is perfect, the moon's shadow is cast upon Earth's surface, creating the opportunity to witness a total solar eclipse.
Earth to Sun distance
between 147 and 152 million km
Sun's diameter
1,392,684 km
Moon to Earth distance
between 363,104 km and 405,696 km
Moon's diameter
3,474 km
Why so few total solar eclipses?
As the moon comes between the sun and the earth roughly every 29 days, one might anticipate witnessing an eclipse each time. However, the moon's orbit is inclined by about 5 degrees, making the alignment insufficient most of the time.
There are only two periods in the year when conditions align for the observation of a solar eclipse. It can occur a maximum of 5 times in a year, but such occurrences are extremely rare. In most years, only 2 eclipses happen, and at times, they are merely partial (with only the penumbra of the Moon reaching the Earth). Total eclipses, therefore, are even more exceptional.
Why can't I see all the solar eclipses?
Total solar eclipses aren't as uncommon over a human lifetime. In the 21st century alone, there will be a total of 68 of them. However, when a total eclipse occurs, it's not visible everywhere on Earth. It's confined to a narrow band, roughly 200 kilometers at most (124 miles) in width, and each time at different locations around the globe (sometimes in the middle of oceans). The probability of this path passing through your specific location or country multiple times in your lifetime is consequently quite low.
21th century eclipse count.
total
68
annular
73
partial
77
hybrid
7
Simulation of the total eclipse on April 8th, 2024: Only a small portion of the globe is covered by the Moon's umbral shadow.
What if...?
...the Moon was smaller
or farther from Earth.
There would never be total eclipses, only annular or partial eclipses. We wouldn't be able to easily admire the solar corona, chromosphere, prominences, and the "diamond ring" effect.
...The moon was larger
or closer to earth.
Total solar eclipses would occur more frequently and last longer. However, the diamond ring effect would be absent, and prominences would only be visible for a brief period during the 2nd and 3rd contacts. The bright region of the lower corona would also remain unobservable.
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