The Captain wrote:
<Anyone know what
<has happened to the total mass of "the planet earth" over it's
<lifetime. Has it changed and if so how would that affect it's orbit of
<the sun.
AFAIR from my planetary science lectures.
According to the theory of planetary accretion, which is the most widely
accepted and taught interpretation, the earth started out as lumps of rock
whizzing around in space and crashing together. When they had slowed down
enough to crash without vaporising (<100m/s), they started to stick
together. Thus were formed the first planetesimals. Then they started
banging together and sticking to form planetoids (Ha, throws in option for a
boring argument about nomenclature, which scientists love.;-)) Process
continued, with the chunks increasing in size and the collisions in energy,
melting whole moon sized bits and knocking some planets off their vertical
axis of rotation (Uranus' axis is +/-parallel to its orbit for instance).
This "Heavy Bombardment Period" continued until about 3.9 Ga (3,900,000,000
years ago) and at that point in general terms the mass of the earth
stabilised. It is a largely closed system, remembering that the atmosphere
is actually the outer gas layer of the planet, not a separate entity; small
losses to outer space are probably accounted for by incoming debris.
Dunno about derelict satellites and other space junk though, and shooting
our rubbish off into space, to dump it in black holes and the like would not
be a good idea in the long term (millions of years)
As the solar system works in a similar way to a planet in terms of
differentiation of materials I would suggest that changing density would
have more impact than a change of mass alone. If we found a way to extract
the nickel iron from the planets core and used it to build a scaffolding
superstructure over the whole planet then we might expect to be relegated to
an area nearer the gas giants.
Of course if the universe was constructed in seven days, or the earth was
made from the genitals of someone's father or floats around space on the
back of a giant turtle, then none of this is true and you are probably a
figment of my imagination anyway and I therefore have no idea why I am
writing all this (:-)
Caroline
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