What determines the path of our moon in the sky?

Question

We are all aware that like the sun, the moon rises in the east and sets in the west. I note that sometimes it takes the path of the winter sun (low across the southern sky) and sometimes high in the sky (like the summer sun). What are the dynamics of this and how long does it take for it to go from its southernmost path to its northernmost path?

Answer 1

The moon orbits along the ecliptic (the plane that the Earth and other planets follow around the Sun), but the Earth is tilted at an angle from the ecliptic and turns while the moon makes its 29.5 day orbit around the Earth.

Check out the diagram at the link to see how this causes the moon's observed location in the sky to change with the seasons.

Answer 2

When the moon is full, it is on the opposite side of the earth from the sun. Its apparent path across the sky as the earth rotates is then similar to the sun's six months earlier or later. The last full moon (December 23, 2007) was high in the sky like the summer sun, because the sun's path was low across the southern sky last week. The new moon is close to the sun and follows a similar path to the sun's. We don't generally see the new moon, but a few days before or after, we can spot the moon rising or setting near where the sun rises or sets. Next month's new moon will be an anular solar eclipse, so the path across the sky will be almost identical to the sun's. Unfortunately, I'd have to go to Australia or thereabouts to see the eclipse.

If you keep paying attention to the paths of the sun and moon as you have, you can work out how the moon's path varies over an entire year's worth of the sun's variation as it goes through its phases from one new moon to the next.

Answer 3

Hi FG!

The moon's movements are easy to understand!

The moon follows roughly the same path around the sky as the sun does. Since the moon moves more than 13 times faster in its apparent motion than the sun does, however, it goes through all four seasons in less than four weeks.

Where it takes the sun three months to pass through a season, the moon does it in under a week.

When the moon is in the "summer" part of its orbit, the moon is high in the sky. Two weeks later, when it is in the "winter" part, the moon is low in the sky.

This very rapid passage through the "seasons," less than a week for each one, causes some fascinating effects. If it is winter according to the sun (as is the case right now in the Northern Hemisphere), but the moon is heading toward "spring," the waxing crescent moon will stay out far into the evening, and you'll see clearly the "new moon in the old moon's arms." Watch starting on January 10th and January 11th, and see how late the thin crescent of moon stays up, already 2 1/2 hours after the sun on the 10th.

You've heard of the Harvest Moon in September? It is caused by the moon, in it's "early spring" position, moving rapidly northward. Night after night, it rises only about 25 minutes later each evening, and you can see the Last Quarter rising in the sky before midnight, even though we're on Daylight Saving Time.

By contrast in winter, when the full moon is starting out from its "summer" position and heading southward (for us in the Northern Hemisphere), as it is right now and will be again starting January 23rd, each evening the moon rises 70 minutes later, nearly three times more than in September, compared with the night before. In only a few days, the moon has disappeared from the evening sky altogether.

Answer 4

It must be because the plane of the moon's orbit is fixed in space while we change our viewing position relative to it somehow. Right now I'm having a tough time imagining this in my head ... the earth's axis is also fixed in space, so where's the shift in perspective coming from? It must be that the night side of the planet becomes the "other side" in a sense when we go from summer to winter, I'm guessing.

Hmm .. I have to think about this some more.

I know the moon always rides high in winter and low in the summer (at least here in Minnesota).

Answer 5

The Moon circumnavigates the Earth in 28 days, from the West to the East. Note, it does not rise in the East.

The gravity of the Earth keeps the Moon in orbit, but the moon is slowly moving away from us due to is constant circumnavigation (constant spinning).

The Moon affects the tide and gently tugs at the Earth crust as it goes around us. Note, earthquakes are more frequent in areas just behind the Moon's path.

Answer 6

Hi. It takes two weeks or so. It has different illuminations at the peaks of its orbital period. There was a question from a week or so ago about this. http://answers.yahoo.com/question/index;_ylt=AhShhrt41VKE6EDSL.F4JLzsy6IX;_ylv=3?qid=20071220113634AA4vyhH

Answer 7

gravity between the earth & the sun determines it's path & keeps it in its orbit

Answer 8

The orbit is constant and we rotate under neath it. spin a gyro it will stand still. The space craft uses it for navigation.

Answer 9

Gravity is the simple answer, im sure nasa's website has something more specific.