Earth as a Control Volume
Earth as a Control Volume
(OP)
Hello all, I wasn't sure where to put this, but I think history has the most bearing.
Taking the Earth as a control volume, say a sphere 2 miles off of sea level - are we losing or gaining?
Input I could see as solar energy, meteor(ites), comets, dust etc.
Output I see as satellites, spaceships, and all hydrogen/helium we "create" from other compounds.
What does everybody think, will we run out of "stuff"? (not on an entropic basis, just in terms of throwing things off-planet)
Taking the Earth as a control volume, say a sphere 2 miles off of sea level - are we losing or gaining?
Input I could see as solar energy, meteor(ites), comets, dust etc.
Output I see as satellites, spaceships, and all hydrogen/helium we "create" from other compounds.
What does everybody think, will we run out of "stuff"? (not on an entropic basis, just in terms of throwing things off-planet)





RE: Earth as a Control Volume
The mass of Earth is estimated at 6×1024 kg.
It is estimated that 1,000,000 kg of micrometeorites fall on Earth every day, and they appear to be falling at the same rate for, say, some 5 billions years; the total mass addition would be:
ie, less than one millionth of Earth's mass, it is logical to assume the micrometeorites' contribution to Earth's mass is, in fact, insignificant.
RE: Earth as a Control Volume
RE: Earth as a Control Volume
Let's say it's 10^9 kg loss per day (which it's not). Over the lifetime of yourself, your children and your grandchildren, say 150 yrs, that amounts to less than 1 billionth of 1% of the Earth's mass.
TTFN
RE: Earth as a Control Volume
RE: Earth as a Control Volume
TTFN
RE: Earth as a Control Volume
Just my 2.5 cents
Go Mechanical Engineering
Tobalcane
RE: Earth as a Control Volume
actually this thread is a good initiation point for global warming. the key question (IMHO) is how much is the global weather being affected by human activities ? if we're causing the changes (which i personally doubt) then we should be able to affect change. if the system is so large that the human contribution is tiny (trivial) then we're going where the system is taking us (like the flea on the dog) even if we don't like it.
thoughts ?
RE: Earth as a Control Volume
Have you noticed that London no longer has "killer" fog? It turns out that London started to not have heavy fog, once people stopped using wood for heating and cooking.
The earth's atmosphere is a highly non-linear, positive-feedback system. Small perturbances get rapidly magnified. The growth of a hurricane would be impossible in a linear system. Yet, we can see both non-linearity and positive feedback in a hurricane system.
Likewise, while our contributions might appear small, they alter the balance and the disturbance gets amplified. Ozone destruction has at least slowed, once we stopped using the worst of the chlorocarbons. Once we reduce or at least stop the growth of our contributions of greenhouse gases, there's some hope that global warming will at least slow down.
Benoit's origination of chaos theory arose from the observation that a less than 1 ppm change in atmospheric variables would radically alter climate outcomes, over a very short time scale. Over larger time scales, even a less than 1 ppb change would affect the net outcome.
TTFN
RE: Earth as a Control Volume
rmw
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RE: Earth as a Control Volume
Don't think so.
The fogs were caused by burning coal in open grates.
Cured by changing to burning smokeless fuel briquettes.
Which moved the pollution from London to the mining areas where the smokeless fuel was produced.
In stinking plants like the Phurnacite one in Aberdare...