 |
 |
Receding Moon and Lunar Origin
Name: Sue
Status: other
Grade: other
Location: NV
Country: N/A
Date: N/A
Question:
If the moon is moving away from the earth at approximately
1.5 inches a year,and the earth is approximately 4.5 billion years
old. Then how far was the moon from the earth then? Would 4.5
billion years times 1.5 inches = miles from earth. The moon being
221,463 miles, how accurate would that be. The number of miles I
come up with is not even close. A mile being 63,360 inches. That
would make the moon part of the earth. When did the moon separate
from the earth?
Replies:
Hi, you have just nailed an important theory right on the head.
There is a very well supported theory that the current Earth and
Moon were produced from the collision of two planets in the early
development of the solar system. These two planets, let us call them
proto-Earth and proto-Moon collided, mixed, and then coalesced into
the current Earth and Moon, with the Moon steadily getting farther away.
Many different data support this theory. The fact as you have
pointed out that they are moving apart (unusual since gravity should
be bringing them together as is the case in other planet/moon
systems), the unusual similarity in composition of the two bodies,
the age of the rocks on both bodies, etc.
You have to imagine that the separation is not linear though. We can
expect that the Moon is receding but at a decreasing rate. So, your
calculations are not quite accurate, but it gets the point across.
Greg (Roberto Gregorius)
Canisius College
The assumption that the present "drift" in the Earth-to-Moon distance is
likely flawed. There are a number of phenomena (e.g. tidal drift, solar
effects to name just two of a much longer list) that can alter that
separation spacing. There is at least one theory that proposes that the Moon
was part of the Earth.
So it is important to using present day data extrapolated back millions of
years.
Vince Calder
Click here to return to the Astronomy Archives
| |
Update: June 2012
|
|
