Yes, the Earth would have phases just like the
The interesting thing about this is
that the moon is tidally locked to the Earth.
What this means is that the moon rotates only once
on its axis in the time it takes to orbit the
Earth. One "day" on the moon is about 28 days on
Earth. A consequence of this is that if you stay
in one location on the moon, the Earth is always
in the same part of the sky. If you landed on the
"dark" side of the moon you would never see the
Earth at all. Wherever you are on the moon, the
sun would rise every fourteen days or so and set
about fourteen days later.
Ah, an excellent question. Your students aren't
old enough to remember the first photos from the
Apollo capsules as they orbited the moon and
captured a picture of an "earth rise", but clearly
they are thinking about the same
Yes, the earth has phases when
viewed from the moon. And yes, they are opposite
from those seen on earth. You can prove it with
two balls and a flashlight in a darkened room. Put
the flashlight on a table, and aim it at another
table with the two balls on it. Remember that the
moon orbits around the earth about every 28 days.
Put the moon farther away from the "sun"
flashlight than the earth, and look at it from
directly over the earth.
You should see the
moon mostly illuminated from this point of view
(like a full moon). Now, look at the "earth" from
over the moon. You should see only part of the
earth lit up, since it is closer to the sun. Now
you're seeing a "new earth" with the same
perspective as when you see a new moon.
reversing the position of the balls and changing
your viewpoint accordingly.
happens when the earth is directly in front of the
moon, blocking the light from the sun? And when
the moon blocks the sun's rays from reaching the
earth? What do we call these special
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