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Science and Technology "Somewhere, something incredible is waiting to be known." - Carl Sagan.

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Old December 4 2011, 06:11 PM   #16
YellowSubmarine
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Re: Most liveable alien worlds ranked

There's some evidence for volcanism (which was a surprise to me), but it's probably far less geologically active than the Earth.

Any way, the point is not to have energy as an absolute value, but to have energy that you can use. Useful energy input. You can't extract energy from heat. For example, you'd be unable to set a colony inside the sun due to the lack of extractable energy. If you had energy, you could use it to cool down the colony enough so you can safely stay inside the sun. But you simply can't find the energy to use to cool your colony down, which is why you can't have a colony inside the sun.

Venus is a less extreme example of that.

(Well, you could run a fission reactor on Venus or a fusion reactor on the Sun, so it's not completely out of the question, but beside that, nothing.)
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Old December 4 2011, 06:18 PM   #17
Deckerd
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Re: Most liveable alien worlds ranked

Why can't you use extract energy from heat? Run that by me again? Ignoring your Sun comments which are silly.
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Old December 4 2011, 06:22 PM   #18
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Re: Most liveable alien worlds ranked

Devices that extract energy from heat are otherwise known as perpetual motion machines of the second kind. I do hope and believe we will make such at some point in the future (otherwise we are doomed), but we certainly can't make them now.
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Old December 4 2011, 06:29 PM   #19
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Re: Most liveable alien worlds ranked

So any settlement on Venus would necessarily have to take a lot of water and the means for producing more water. And if they apply the atmospheric heat to that water in, oh I don't know, off the top of my head, a pressure vessel; they wouldn't be able to make any use of that whatsoever. Uhuh.
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Old December 4 2011, 06:35 PM   #20
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Re: Most liveable alien worlds ranked

I have no idea what you're suggesting, but they could apply the atmospheric heat once, after that they'd need to find ways to cool it down. But perhaps you could build a perpetual motion machine – you extract energy from the initial heating and use it to cool the water down after that.

What's a pressure vessel and what does it do?
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Old December 4 2011, 06:49 PM   #21
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Re: Most liveable alien worlds ranked

You mean like a vapour compression refigerator?
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Old December 4 2011, 07:04 PM   #22
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Re: Most liveable alien worlds ranked

No, like a steam engine providing electricity for the vapour compression refrigerator. Since I don't know what a pressure vessel is and how it makes energy, and you didn't tell me, I replaced it with a steam engine because I know it.

So, cold water gets heated, the steam is used to drive a rotor, which is converted to electricity, which is used to power the vapour compressed refrigerator, which cools the water back down. Classical perpetual motion machine. If this worked, we wouldn't go through all the trouble to use solar, nuclear, coal and wind energy.
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Old December 4 2011, 07:09 PM   #23
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Re: Most liveable alien worlds ranked

So what you're saying is heat can't be used as a source of energy.
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Old December 4 2011, 07:14 PM   #24
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Re: Most liveable alien worlds ranked

That's what the second law of thermodynamics states. If you could make energy from heat your PC would use no electricity – you would use the heat generated by the CPU to power up the PC. And the heat generated by the EM radiation coming from the monitor. In the winter, you'd extract heat from the outside (reducing the temperature there) to make electricity and subsequently heat your home, again without any electricity.
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Old December 4 2011, 07:18 PM   #25
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Re: Most liveable alien worlds ranked

How would you power up the CPU to make heat?
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Old December 4 2011, 07:23 PM   #26
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Re: Most liveable alien worlds ranked

You'd make energy from the heat and power it? Except for a little bit of EM radiation, all the energy the CPU uses is released back as heat. If you could turn that heat back into useful energy, you wouldn't need any additional energy to power up that CPU.
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Old December 4 2011, 07:29 PM   #27
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Re: Most liveable alien worlds ranked

I think your example is a bit ad hoc. However you win the heat argument. But then. There's an awful lot more powerful wind on Venus than there is on Mars ...
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Old December 4 2011, 07:45 PM   #28
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Re: Most liveable alien worlds ranked

Rather Venus than Mars, which will remain useless. Too little gravitation to keep a substantial atmosphere, not much to make it from in the first place, too little water and nothing to extract more from, no magnetic field. Life on Mars will take place indoors only. One technology to clean Venus' atmosphere from C02 and thereby removing the greenhouse problem which isn't SF already exists, "artifical trees". We might possibly see millions of them soon here on Earth to fight our CO2 problem. There isn't much water vapor in % in it's atmosphere, but the value has to be multiplied by about 100, that's how much denser Venus' atmosphere is at the surface than Earth's. Enough to cover much of the planet with shallow oceans, it's whole landscape is as amazing and hilly as the American Midwest. The oxygination could reduce the surface pressure to 3 bar; dissolving nitrogen in liqid water, and binding oxygen in all sorts of stable compounds naturally would reduce it further. Still, the long solar day, and maybe because of it weak magnetic field remain.
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Old December 4 2011, 07:46 PM   #29
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Re: Most liveable alien worlds ranked

I stand corrected for the surface winds. After checking, they are more powerful/faster than what I expected. They are very slow, but still quite powerful. You could set up a hardened wind power plant there, though I'm not sure how big it will have to be to produce any significant energy.

The idea about a surface Venusian colony is quite fascinating, because of how crazy it is when I picture it – think about wind turbines going on for miles and miles powering up a small colony at the middle, creating a small paradise in the middle of hell.

Still, the cloud tops and Mars are better choices...
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Old December 4 2011, 07:58 PM   #30
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Re: Most liveable alien worlds ranked

The only way Venus could be colonised is underground, IMO. You need to protect little squashy bodies from the atmosphere with something more substantial than man-made structures.
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