Explanation:
The Moon's measured
diameter is around 3,476 kilometers (2,160 miles).
But apparent
angular size,
or the angle covered by an object, can also
be important to
Moon enthusiasts.
Angular size depends on distance, the farther away an object is, the
smaller an angle it covers.
Since the Moon is 400,000 kilometers away, its angular size
is only about 1/2 degree,
a span easily covered by the tip of your finger held
at arms length, or a measuring tape held in the distance by a friend.
Of course the
Sun is much larger than the Moon, 400 times larger
in fact, but today the New Moon will just cover the Sun.
The total solar eclipse can be seen along a track
across northern Canada, the Arctic, Siberia, and northern China.
(A partial eclipse is visible from a broader region).
Solar eclipses
illustrate the happy coincidence that while the
Sun is 400 times the diameter of the Moon, it is also 400 times
farther away giving the Sun and Moon exactly
the same angular size.
Total Solar Eclipse:
Webcast from China
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