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Why are Lunar Eclipse more common than Solar Eclipse? Chapter from Light

  1. My thoughts; Eclipse can only occur at new moon and moon orbit is inclined at an angle of about 5 degrees to the earth's orbits so that only rarely does the new moon pass the exactly through the line between the earth and the sun and because Solar Eclipse occurs once a year while Lunar Eclipse occurs once a month
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Why are Lunar Eclipse more common than Solar Eclipse?

They aren't. Lunar eclipses and solar eclipses occur with almost equal frequency.


From http://eclipse.gsfc.nasa.gov/eclipse.html and pages within, there were / will be 11898 solar eclipses of all types and 12064 lunar eclipses of all types in the five millennia between 2000 BCE to 3000 CE. Lunar eclipses outnumber solar eclipses by less than 3% if you count eclipses of all types.

Of those 12064 lunar eclipses, 4237 were partial penumbral eclipses, in which at any one time only part of the Moon was in the Earth's penumbral shadow, and during the entirety of the event, none of the Moon entered the Earth's umbral shadow. These are extremely subtle eclipses, and because of this some people say they don't count as eclipses. If one discounts these partial penumbral lunar eclipses, then solar eclipses outnumber lunar eclipses by over 50%.

That's not quite fair because partial solar eclipses are also extremely subtle events. If one also discounts those partial solar eclipses, then solar eclipses (total, annular, and hybrid) slightly outnumber lunar eclipses (total and partial), but only by a mere 0.2%.

Another way to look at this is that lunar eclipses and solar eclipses occur with almost equal frequency.


However, for any one person, the odds of seeing a solar eclipse are rather small while the odds of seeing a lunar eclipse are quite large. One has to be willing and financially able to galavant around the globe to see solar eclipses. The path of totality of a solar eclipse covers but a tiny, tiny fraction of the Earth's surface. In comparison, about half of the Earth gets to see a total lunar eclipse.

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The apparent size of the moon (from Earth) is about the same as the sun's. Therefore the moon has to pass over the sun's path at the time of the new moon for there to be a solar eclipse.

The apparent size of Earth (from the moon) is much greater than that of the sun - because the Earth's diameter is about 4 times that of the moon, and hence the alignment of the sun and Earth does not need to be so precise compared to the conditions required for a solar eclipse.

That is why there are more lunar eclipses than solar eclipses. However it is not the case that there is a lunar eclipse every month, nor a solar eclipse every year.

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    $\begingroup$ There aren't more lunar eclipses than solar eclipses. They occur with more or less equal frequency. If you see a total lunar eclipse on some given night, there will be a total solar eclipse somewhere on the Earth 9 years and 5.5 days later, and vice versa. $\endgroup$ – David Hammen Feb 5 '16 at 10:31
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    $\begingroup$ I stand corrected, but I'm not sure where my argument falls down. $\endgroup$ – Dr Chuck Feb 5 '16 at 16:33
  • $\begingroup$ I didn't downvote, but your argument does fall down because solar eclipses and lunar eclipses occur with more or less the same frequency. The difference between the two is that while a lunar eclipse is visible from over half of the Earth, a solar eclipse is only visible from a tiny portion of the Earth. $\endgroup$ – David Hammen Feb 5 '16 at 17:26
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    $\begingroup$ Yes, I see that from the data, but I don't understand why it is so. I had expected that there would be more lunar eclipses simply because the earth's shadow about 16 times the area of the moon's shadow. $\endgroup$ – Dr Chuck Feb 5 '16 at 22:29

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