arghman said:
interesting.
I have a question (slightly different topic): how come the moon seems to have a different orbit (w. respect to the earth) than the sun? I've noticed it seems to go much higher overhead in the sky than the sun does.
You might check out an explanation on
this web page among other similar pages. Of course the orbits are quite different. What you are referring to is the apparent path of each in the sky.
The simple answer is that the moon indeed does follow the same apparent path as the sun (an imaginary circle called the "ecliptic"), offset by about 5 degrees. The moon actually follows the same relative path (+/-5 degrees) as the sun does at some different time of year across the sky. Start in simplified mode by thinking of drawing the orbits of the planets about the sun, and the moons about the planets, as circles on a flat piece of paper. Now realize that some of those circles have a slight tilt relative to the flat paper, like a plate tipped up on one end (5 degrees for the moon). In addition, each of the planets (and moons) spins like a top, with some tilt relative to the flat paper (23.5 degrees for the earth).
As to why the moon is high when the sun is low, that has to do with the angular tilt of the poles of the earth (23.5 degrees) relative to the orbit plane of the earth about the sun - which of course is what causes our seasons. Due to that tilt, when the noon sun is in the winter sky, the daytime ecliptic is relatively low on the horizon for us - the sun is low in the south at noon as seen from our mid-north latitude location. Viewing the tilt from the other side 6 months later, which would be the sun's summertime position on the ecliptic, the sun is high up in the sky at noon. As the earth orbits the sun in the course of a year, the sun's position appears to us to be slowly sliding along this tilted ecliptic circle. Therefore the sun follows a slightly different path across our sky each day.
So... if the sun is in it's winter (low) position on the ecliptic, the moon at some other ecliptic position will be higher. Vice-versa for summer. They will follow different paths on the same day.
During winter, the full moon (by definition on the opposite side of the earth from the sun) will be in the same place along the ecliptic as the summer sun (+/- 5 degrees). The full moon can be extremely high overhead in winter. The moon follows the same relative path as the sun does at some different time of year across the sky. If the moon did not have its own 5 degree offset from the ecliptic, we would have one solar and one lunar eclipse each month.
