 A solar eclipse occurs when the
moon moves between the Earth and
the sun, blocks the sun’s light,
and casts a shadow on the Earth.
When the moon completely covers
the bright disk of the sun,
that’s a total solar eclipse,
and it happens roughly every
year and a half somewhere on
Earth. A partial solar eclipse
is more common, happening at
least twice a year. A lunar
eclipse, on the other hand, is
where the moon moves behind the
Earth, so it’s now the Earth
blocking the sun’s light on the
moon, creating a shadow on it
with a red tint. The easy way to
remember the difference is to
remember what gets darker. With
a solar eclipse, the sun gets
darker, and during a lunar
eclipse, the moon does. A solar
eclipse is a rare event that not
many get to see, because the
moon’s shadow is relatively
small. This limits the locations
on Earth that get to see it. You
have to be on the sunny side of
the planet, and you have to be
in the path of the moon’s
shadow. So, if you find your
area in the path of totality one
year, you’ve hit the jackpot,
because on average, that same
spot on Earth will only get to
see a solar eclipse every three
hundred seventy-five years!
During a solar eclipse, the moon
casts a shadow with two parts:
the umbra and penumbra. The
moon’s umbra is the part of the
moon’s
shadow where the entire sun is
blocked by the moon. In space,
it’s a cone extending some four
hundred thousand kilometers
behind the moon. It’s when the
small end of this cone hits the
Earth that we experience a total
solar eclipse. Most eclipse maps
depicting the path will show
you a circle representing the
shadow of the moon, but in
actuality, the true shape of the
umbra is more like an irregular
polygon with slightly curved
edges. This is because the moon
isn’t a perfect circle – it has
mountains and valleys on its
surface, which all affect the
passing sunlight and subsequent
shape of its shadow. And
scientists now have a greater
understanding of the shape of
the moon’s surface, thanks to
NASA’s Lunar Reconnaissance
Orbiter. The unprecedented level
of detail from the topographic
maps, photos, and other datasets
has allowed us to more precisely
pinpoint the regions on Earth
falling within the path of
totality of a solar eclipse. So
if you get the chance to witness
a solar eclipse, always remember
that our little moon plays a
role that's quite large.
[beeping]
