Why are most planetary orbits nearly circular?

Say the planetary orbital motion is due to the gravitational pull, then why is it that our earth and other planets have an elliptical orbit ? Aren't all the planets supposed to revolve in circular orbits

• Answer:

  No, planets are supposed to revolve in elliptical orbits. The circle is just the special, and unusual, case of an ellipse with an eccentricity of zero. Planets come about by the random accumulation of material, so their initial velocity is essentially unpredictable. In order to have a circular orbit, that initial velocity has to be *exactly* right, in both magnitude and direction to make a circle. If it is wrong, it either starts to fall in because it is going too slow, or starts to fly out because it is going too fast. But as it falls in, it gains speed and begins to fly out again. And as it flies out it loses speed and begins to fall in again. These two actions combine make it travel in an ellipse.