Do shadows from other planets cause the phases of the Moon? Let's find out. Hey Deigo
you what do you think causes the phases of the Moon? It's gotta be the shadow
from Mars right? No it's got to be the shadow for Mercury. I'm so misunderstood.
Might the phases of the Moon be caused by Earth's shadow? Let's look at the phases
of the Moon as it orbits around the Earth over its twenty seven day period.
Note that the Sun is to the right and Earth's shadow will be represented by the
blue cone on the left. Here we see the first quarter and we see the Moon shadow
has appeared. But the Moon isn't even in Earth shadow yet. As we move towards
Earth's shadow we can see a full moon. If the Moon were in Earth's shadow we would
see it here. As the Moon continues going past Earth's shadow we see a shadow
growing as we approach third quarter. Finally, as the Moon comes between the
Sun and the Earth, we see that the Moon is opposite of the Earth's shadow. But
it's the side of the Moon that is completely dark to us. Therefore, the
phases of the Moon cannot be caused by Earth's shadow. if you still don't
totally understand the phases of the Moon try this for yourself. All you need
is a ball, like a baseball, to represent the Moon and a lamp to represent the Sun.
Your head will represent the Earth. Go into a dark room with your materials and
turn off all the lights. And don't forget the lamp. In order to do this, your Earth-
Moon- Sun system needs to be set up as so. Let's see if we can get the Earth's
shadow to create some of the Moon shadows. Here we are starting at a new
moon. Since the Moon has a slightly tilted orbit, the Moon should be below
eye level for the new moon. The side of the Moon facing you is entirely in the
shadow. Remember, your head represents the Earth. Where is your head's shadow? Is it
possible for your head's shadow to be on the Moon for this phase? Nope. Therefore,
the Earth's shadow could not cause a new moon. If we fast forward approximately
seven days we will see the Moon in first quarter. Look around and find your head's
shadow. Does it look like your head's shadow is falling on the Moon? We can
repeat this step one more time as we move to a full moon. Because of the
Moon's tilted orbit the Moon should be just above our eye line here. Let's take
a look and see where your head shadow is. Does it look like your shadow causes a
full moon? Finally, moving to the last stage we will
demonstrate the third quarter. The Moon has moved back to eye level and as we
can see Earth's shadow still isn't facing the Moon.
How many of the phases were caused by the shadow of your head? Through this
in-person exercise, it is apparent that the Earth's shadow could not possibly
cause the phases of the Moon. In summary, we've learned the phases of the Moon are
not caused by shadows from other celestial bodies. The shadows from
Mercury and Venus are too short to reach the Earth-Moon system. The shadows from
Mars and other outer planets are pointed in the wrong direction. The Moon is also
spherical, that is how it tests half a shadow onto the Moon.