June:
Actually, this is not quite correct. The Earth forms and then over a period of time, gets bombarded by comets (which is where the most likely came from). Now, as far as mass being added by the living things actually that's not the case. All of the mass in your body and in the bodies of other living things was already present on the planet. Here is where the conservation of energy comes in. Right now, chances are, one of the oxygen atoms you've just inhaled was breathed by a Caesar, or some Roman slave from the time of Caesar. All of the activity you've spoken of--comets and asteroid collisions notwithstanding--redistribute the mass of the planet without actually adding or reducing the total mass.
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Originally Posted by June
Dear Giver of Science Wood, (Hah!)
Okay, secondary to worrying about the sun exploding in my lifetime, is this 'nother thing.
So, the earth gets formed and begins cooling, and then condensation occurs and eventually, we get a weather system that creates rain, then over time, the oceans get filled up and the original land masses begin tearing apart slowly and clusters of cells begin evolving into different species. Yadda, yadda.
The original earth mass gets added on to. Millions of years of vegetation and decay, birth and death of humans, animals and plant matter -- All of this 'stuff' adds to the total weight of the earth, right?
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Strictly speaking, we should talk about the *mass* of the Earth and not its weight. The weight of an object is a function of the gravitational field the object is in. So if you are, say, 180 lbs on Earth on the Moon you would weight just 30 lbs. So in order to talk about the weight of the Earth we would have to know what gravitational field we're talking about. The mass of the Earth, however, is more or less a constant. We gain trivial amounts of mass from dust blown at us by the solar winds and we gain slightly more (but still trivial) amounts of mass from asteroid impacts (large ones actually cause us to lose mass).
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But, my real question is: Could we at some point create so much flotsam and jetsam here that it actually will slow down our rotation, creating longer days and nights or other more catastrophic events?
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Actually, the Earth IS slowing down but not because of its mass. Remember that any body in motion will continue in motion unless acted upon by another force. The Earth's rotation is slowing down but not because of OUR mass but because of the mass of the Moon. Some of the energy of Earth's rotation is transferred to the Moon. There is also friction from space dust.
It will take a few billion more years before a day on the planet gets appreciably longer though.
Cheers
Aj