Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: chris on 25/03/2011 08:51:39

Title: Why was the moon closer to the Earth recently?
Post by: chris on 25/03/2011 08:51:39

Is the orbit of the moon not circular? Why should it come closer to the Earth at times?

Chris

Title: Why was the moon closer to the Earth recently?
Post by: Phractality on 25/03/2011 09:13:59

The orbit is elliptial. It has a close approach to Earth every month. The odd thing about this month is that the close approach coincided with the full moon.

Title: Why was the moon closer to the Earth recently?
Post by: Pikaia on 25/03/2011 09:39:43

The orbit of the moon is not a simple ellipse because of the Sun's gravity.

When the Moon is new it is closer to the Sun than the Earth, so the Sun pulls it more strongly than it pulls the Earth. This difference means that the Moon's orbit is extremely complicated. A further complication is the Earth's equatorial bulge. The result is that the direction of perigee moves around the Earth, and the distance at perigee also varies - between 1960 and 2040 the perigee varies from 356445km to 370354km.

Title: Why was the moon closer to the Earth recently?
Post by: chris on 26/03/2011 14:32:29

Thank you - very clearly explained.

Chris