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A solar eclipse occurs when the
moon moves between the Earth and

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the sun, blocks the sun’s light,
and casts a shadow on the Earth.

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When the moon completely covers
the bright disk of the sun,

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that’s a total solar eclipse,
and it happens roughly every

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year and a half somewhere on
Earth. A partial solar eclipse

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is more common, happening at
least twice a year. A lunar

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eclipse, on the other hand, is
where the moon moves behind the

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Earth, so it’s now the Earth
blocking the sun’s light on the

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moon, creating a shadow on it
with a red tint. The easy way to

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remember the difference is to
remember what gets darker. With

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a solar eclipse, the sun gets
darker, and during a lunar

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eclipse, the moon does. A solar
eclipse is a rare event that not

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many get to see, because the
moon’s shadow is relatively

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small. This limits the locations
on Earth that get to see it. You

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have to be on the sunny side of
the planet, and you have to be

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in the path of the moon’s
shadow. So, if you find your

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area in the path of totality one
year, you’ve hit the jackpot,

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because on average, that same
spot on Earth will only get to

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see a solar eclipse every three
hundred seventy-five years!

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During a solar eclipse, the moon
casts a shadow with two parts:

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the umbra and penumbra. The
moon’s umbra is the part of the
moon’s

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shadow where the entire sun is
blocked by the moon. In space,

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it’s a cone extending some four
hundred thousand kilometers

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behind the moon. It’s when the
small end of this cone hits the

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Earth that we experience a total
solar eclipse. Most eclipse maps

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depicting the path will show
you a circle representing the

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shadow of the moon, but in
actuality, the true shape of the

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umbra is more like an irregular
polygon with slightly curved

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edges. This is because the moon
isn’t a perfect circle – it has

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mountains and valleys on its
surface, which all affect the

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passing sunlight and subsequent
shape of its shadow. And

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scientists now have a greater
understanding of the shape of

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the moon’s surface, thanks to
NASA’s Lunar Reconnaissance

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Orbiter. The unprecedented level
of detail from the topographic

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maps, photos, and other datasets
has allowed us to more precisely

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pinpoint the regions on Earth
falling within the path of

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totality of a solar eclipse. So
if you get the chance to witness

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a solar eclipse, always remember
that our little moon plays a

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role that's quite large.

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[beeping]