On Feb 1, 10:16 am, Cathal Garvey <cathalgar...@gmail.com> wrote:
> Work can only be extracted from a gradient of energy, not merely energy
> itself.
...in a closed system using only chemistry. Terraforming another
planet is about as open and 'not strictly chemical' as any of our
systems currently get.
>
> Tidal, too, is not "ambient". Tides are pulled up and down by the
> momentum and gravity of the moon, which makes me whimsically wonder
> whether the harvesting the ultimate source of the energy (the momentum
> of the Moon) means that Tidal would actually gradually slow down the
> moon into a decaying orbit.
>
It depends on your definition of "ambient" and yes, slow the Earth's
rotation and eventually pull the Moon back. The question is how much
energy for how long, I think it's safe to whimsically say if we
focused on pulling the Moon back using the Oceans we're talking a
minimum of 10,000 yrs. probably closer to millions.
> To offer a simple example; you can extract work from a heat source by
> boiling water into steam, and extracting energy from the difference in
> pressure between the heated chamber and the outside, or between the
> heated chamber and a cooled chamber (where the steam condenses, creating
> a pressure-gradient).
> If you were to just put the turbine into the heated chamber, without a
> gradient, it wouldn't matter how much energy you poured into the system,
> you'd get no work done.
>
I realize we're talking about simple astrophysics, but I appreciate
the advanced thermodynamics lesson. You're taking the issue out of
context. If I wired a radio beacon to a wind turbine and set one on
the surface of Mars and floated the other on the atmosphere of Venus,
which one would I get more broadcasts from more frequently? Sure,
you'd have to engineer a balloon(ish) device to keep it afloat, but
that's easier than making it 90X more sensitive to "wind". Considering
we did the former and have yet to perform the latter...
> To offer another example; "ambient" energy can be analogised to water
> content. A vessel may be half full, or entirely full, but that doesn't
> affect how much energy it provides. Only when you start to pour the
> liquid does its embodied energy become useful; you capture the momentum
> of the falling liquid to generate energy. Sure, more water means more
> energy can be generated, but unless there's a gradient (somewhere for
> the water to fall), you can't generate any energy from it.
Once again, taking the systems under question out of context (liquid
water, hah!). If I have a cold glass with a sliver of ice at the
bottom and a 700 degree crock pot with 10X the amount of water in the
form of steam, which system has more potential energy to yield?
Think of it in more complex and less 'already solved' (maybe biased)
terms; you're in a -20 freezer with a jacket on, 4 liters of liquid
water, and a plant you want to keep alive. At the far end of the
freezer is an LED-like lamp that produces plenty of broad spectrum
light but doesn't heat the room appreciably. About 2/3 of the way
between you and the LED lamp is a solar panel/oven device that stays
at 700 degrees with a small pot of boiling water on top. About as far
from from you as you are from the heater is a mostly frozen glass
that's less than 1/3 full of water. Survive as long as you can. To me,
the answer is figure out how to regulate the heater, the plant, and
your own metabolism to last until the "LED lamp" goes out and ignore
the frozen glass of water.
> So, venus may be a lot hotter than Earth, but that on its own does not
> make it any more useful for generating energy, unless you can either A)
> Discover a potent gradient of energy within venus or B) Find a way to
> let energy escape venus, and then convert that energy gradient into a
> potential difference (voltage) for electrical generation.
>
> So, the question: Is venus known for having greater gradients of energy
> than Earth, or merely higher ambient energy?
When we're talking about interplanetary travel, what's the difference?
Are you as surprised as I am by alien invasion movies where the aliens
travel across the Universe only to get their asses handed to them by
humans who have "mastered" flight? Aliens couldn't be that stupid,
right?
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