You have a lot of good questions! It seems like
you already have learned a lot about how the Moon,
Earth, and Sun move together to produce the
seasons, so understanding more how the Moon works
will be a snap.
To answer your first
question, the length of time the moon is visible
does change from season to season, just like it
does for the sun. In fact, the amount of time the
moon is visible is flipped compared to the sun, so
when the sun is visible for a long time, the moon
is visible for a short time, and when the moon is
visible for a long time, the sun is visible for a
The reason the moon varies at
all is for the same reason the sun varies, the
tilt of the Earth. As you probably have already
learned, when the Earth is tilted away from the
sun, the sun will appear close to the horizon, and
when the Earth is tilted towards the sun, then the
sun will appear high above the horizon.
you think about the Moon, you might realize that
the moon is brightest and most visible when it is
on the opposite side of the Earth from the Sun
because that is the side of the Earth in
nighttime. If the Sun and Moon are on opposite
sides, then when the Earth is tilted toward the
sun, then it must be tilted away from the Moon! So
just as the Sun wasn't visible for a long time
when the Earth was tilted away from it, the Moon
won't be visible for long when theEarth is tilted
away from it. This is why the Moon varies in the
amount of time visible opposite to the Sun.
Now onto your second question. You are right
that the Earth and the Moon are not orbiting in
the same plane, and I believe that a picture will
greatly help explain how their orbits differ.
diagram of the orbits is available at
diagram of the orbits .
It will helpful if
you can look at the picture alongside reading my
What the picture shows is that the
Earth lies in the Ecliptic Plane, but it is tilted
23.5 degrees with respect to the Ecliptic Plane.
That's the tilt that explains the changes in the
amount of time the Moon and Sun are visible. The
diagram also shows that the Moon's orbital plane
lies tilted at 5.15 degrees with respect to the
Ecliptic Plane, and the Moon is tilted at an angle
of 6.18degrees with respect to its orbital plane.
To show why this avoids a solar eclipse every
month it will be helpful to look at
orbital inclination .
If you pretend that
you are the sun, then the only time the Earth,
Moon, and Sun line up perfectly to create a solar
eclipse is when the Moon lies on the line pointing
at you. If you were instead sitting somewhere to
the left of the picture, then the Earth, Moon, and
Sun wouldn't every line up to create a solar
Wow! That was a lot of new
information. I hope you feel like you understand
more about the Moon, and keep up the questions!
No - the length of time that the moon is up does
not depend on the season.
The reason why the
Earth has different lengths of day is because its
axial tilt is fixed and not perpendicular to its
orbit. As a result, different parts of the Earth
get different amounts of sunlight during different
times in the orbit, creating seasons.
moon's "year" so-to-speak, is 28 days - the length
of time that it takes the moon to go one complete
revolution around the Earth. This would mean that
if the moon's orbit is different from the Earth's
axial tilt (which it inevitably must be, else
eclipses would be much more common), then the
moon's visibility would vary over the course of
the lunar orbital cycle. However, as I said, the
lunar orbital cycle is only 28 days, so over a
dozen of them fit in a single year.
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