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The weight of our planet?

  1. Jul 28, 2010 #1
    Dear all,

    I am currently in a MSc program, in a different subject matter, and for some time I have had a ningeling thought, my question is...

    As an example, say planet earth weighed 100 tons, at its current state, what would the weight of been 100 years ago?

    Some of my associates are of the view that the diminished rain forest, the burning of fossil fules, the quantity of space equipment that have been sent, and the increse of the human population, will all have relevence to this question.

    I await any replies,

  2. jcsd
  3. Jul 28, 2010 #2


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    Staff: Mentor

    The earth's mass increases continuously due to space dust (meteors) constantly hitting it, but this is by tiny fractions of a percent per year.

    Any human factors to decrease that weight are minimal.
  4. Jul 28, 2010 #3
    The only thing that makes sense about influencing Earth weight that you mention is the space equipment sent to space.
    Burning fossil fuels just change the state of that matter, but the mass stays on Earth (i.e as smoot), plants use the air and water and some soil to grow up, but the mass was already there.
  5. Jul 28, 2010 #4


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    Gold Member

    Yah, everything except things being put into space don't contribute to a loss of mass. Diminished rain forests are turned into other things (the trees that is). Fossil fuels when burnt stay in the atmosphere and possibly come back down but they still are part of the Earth. It depends on where you consider the Earth to "end". If you consider everything from the center up to where the atmosphere starts, then fossil fuels converting to gasses and stuff being launched into space reduce the mass of the planet. However if you consider up to where the atmosphere ends, the gasses are still part of the planet.
  6. Jul 28, 2010 #5
    Weight, in the word, is a relative thing, depending on the gravity exerted by a particular object (say the earth...). Mass, however, would be a more accurate description of a particular object's "weight," like "rest mass." (I cannot define that yet for you, but give me a few months :P) Mass of earth does not change (at least in my eyes. I have limited education in this subject) even when fossil fuels are burned or trees are chopped down.

    The mass of the planet might be increasing from space dust, as russ had said, but the result would have been negligible. The earth is what is is (in the sense of mass), the earth one hundred years ago would be roughly the same (probably to a few decimal places). However, if you were to go back a few million years, or even a few BILLION years, the mass MIGHT be different, to the point where gravity would be different and time MIGHT be different.

    Like I said, I have little knowledge in this subject, but my speculation seems to be at least someone accurate...
  7. Jul 28, 2010 #6


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    Science Advisor

    The only stuff that leaves the atmosphere (non-deliberately) as far as I know, is helium gas. Which is produced by radioactive decay.
  8. Jul 28, 2010 #7
    The same should be true for hydrogen, shouldn't it? On the other hand there's some ten times as much helium, so He probably dominates the atmospheric escape.
  9. Jul 28, 2010 #8
    We probably receive 50000000 - 100000000kg worth of energy from the sun each year. I'm sure that adds up to something...

    Unless an equal or greater amount gets blown off by the sun...
  10. Jul 28, 2010 #9


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    Staff: Mentor

    If a near-equal amount wasn't re-radiated back into space, we'd be getting hotter: fast.

    Note, the earth receives about 18,000-25,000 tons (American) of space dust a year: http://www.talkorigins.org/faqs/moon-dust.html
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