Q:

do all the planets spin in the same direction? sorry for the last one, hadn’t read the conservation of angular momentum bit.

- Anonymous

- Anonymous

A:

Nope!

Earth's spin axis is tilted at about 22 degrees with respect to the ecliptic plane, but the spin and orbital angular momentum point 22 degrees from each other (and not almost opposite). Most planets follow this, with their spin axis pointing perpendicular to the orbital plane. But Uranaus is a standout. Its spin axis is about 90 degrees off, which means its spin axis lies almost in its orbital plane.

Tom

Earth's spin axis is tilted at about 22 degrees with respect to the ecliptic plane, but the spin and orbital angular momentum point 22 degrees from each other (and not almost opposite). Most planets follow this, with their spin axis pointing perpendicular to the orbital plane. But Uranaus is a standout. Its spin axis is about 90 degrees off, which means its spin axis lies almost in its orbital plane.

Tom

*(published on 10/22/2007)*

Q:

The overall shape of the orbits of most of the planets in the solar system is what?

- Anonymous

- Anonymous

A:

In the old-old days there were a variety of incorrect ideas about the shapes of planetary orbits. A breakthrough came in the early 17^{th} century when Johanes Kepler, using astronomic data supplied by Tycho Brahe, figured out that the orbits were oval shaped ellipses. Later on Newton derived the correct elliptical shape using the laws of motion he had developed along with the hypothesis that the force of gravity between two objects fell as 1/r^{2}, where r is the distance between them. In the 20^{th }century Einstein developed very small corrections to the elliptical orbits using the general theory of relativity.

See:

and for more more formation.

LeeH

See:

and for more more formation.

LeeH

*(published on 06/07/2009)*