Expert: Ed - 4/6/2010

Question
Hi Ed, the most current theory is that our moon coalesced from debris following a major collision between the Earth and another slightly smaller body. I can't see how this tremendous impact would have failed to knock the Earth out of its orbit. Can you explain? Thanks.

Answer
Paul, from what I can see, the impact that ultimately resulted in the coalescing of our moon was ENORMOUS, but not large enough to actually knock the Earth out of its orbit.  The impact would have altered the rotation of the Earth, probably helping to set our current rotational angle to the plane in which we orbit the sun.  But the theory still works, and it doesn't mean that a huge collision like that would have been enough to knock the Earth out of orbit.

This NASA website discusses the topic in detail.
http://solarsystem.nasa.gov/scitech/display.cfm?ST_ID=446

If you have more questions, please get back to me in a few days.  I am going to try to spend some more time re-familiarizing myself with this subject.

Keep looking up,
-Ed