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[Halnoth]

Very broadly speaking, bigger isn't more efficient, bigger can smash smaller things (whether by eating them or eating their food). Provided they have the energy to smash; bigger requires greater energy density.

Hm, now following Miuramir's idea with our cave system with its portals to the Plane of Fire, might there be the geater variety of underground life under volcanic glaciers? Greatest differential, after all.

He was talking about positive and negative planes. If such planes existed and you could tap into them then presumably you could generate something like an electric current. Which could potentially be used as an enegy source.

A heat gradient isn't the same thing. The heat could be used as an energy source directly.

[a52]

He was talking about positive and negative planes. If such planes existed and you could tap into them then presumably you could generate something like an electric current. Which could potentially be used as an enegy source.

No he wasn't (although conceivably such planes could exist, if planes existed at all). He explicitly mentioned Planes of Fire and Ice, and using a stirling engine (a heat engine) to take advantage of the two.

A heat gradient isn't the same thing. The heat could be used as an energy source directly.

Heat can't be used as an energy source by itself, only heat gradients can. The Earth has billions, probably trillions of joules of heat energy in its atmosphere, but we can't use it because there's nowhere cold to put it. Similarly, the sun would be just as useful (according to classical thermodynamics at least, not really if you consider modern notions of chemistry, relativity, and absolute zero) if it was considerably cooler than outer space rather than considerably hotter.

[Halnoth]

He was talking about positive and negative planes. If such planes existed and you could tap into them then presumably you could generate something like an electric current. Which could potentially be used as an enegy source.

No he wasn't (although conceivably such planes could exist, if planes existed at all). He explicitly mentioned Planes of Fire and Ice, and using a stirling engine (a heat engine) to take advantage of the two.

A heat gradient isn't the same thing. The heat could be used as an energy source directly.

Heat can't be used as an energy source by itself, only heat gradients can. The Earth has billions, probably trillions of joules of heat energy in its atmosphere, but we can't use it because there's nowhere cold to put it. Similarly, the sun would be just as useful (according to classical thermodynamics at least, not really if you consider modern notions of chemistry, relativity, and absolute zero) if it was considerably cooler than outer space rather than considerably hotter.

To the first, I reread it, we are both wrong. He talked about positive and negative planes in the exact same paragraph where he talked about the stirling engine.

The second is semantics. I understand what you are saying but the point is moot. An energy gradient can be described as a transfer of energy. The source of the energy is still the input (the highest concentration of heat). We are saying the same thing. Although I would disagree about the sun being just as useful as a heat sink instead of a heat source but you already stated why this situation would prove problematic.

As an aside, I find it interesting you would choose the atmosphere as your example. Heat energy in the atmosphere is transfered via wind. Humans have been utilizing wind power for quite some time. Granted humans aren't pulling heat energy directly from the air, but we certainly do convert some of the kinetic energy into a form we can more readily use (mechanical and electrical).

[Dozebôm Lolumzalìs]

A gradient isn't a transfer, it's a difference.

[Halnoth]

A gradient isn't a transfer, it's a difference.

Semantics

If you are talking about a heat gradient then you are talking about energy transfer

Regardless the original person I was responding to was suggesting that the biggest variety of life would exist under volcanic glaciers. Which is entirely possible if we are talking about magical systems but is not going to be true in a system that is closer to reality.

It isn't the difference of energy in the environment that matters so much as how much usuable energy exists for organisms to use.

[Dozebôm Lolumzalìs]

A gradient isn't a transfer, it's a difference.

Semantics

If you are talking about a heat gradient then you are talking about energy transfer

Regardless the original person I was responding to was suggesting that the biggest variety of life would exist under volcanic glaciers. Which is entirely possible if we are talking about magical systems but is not going to be true in a system that is closer to reality.

It isn't the difference of energy in the environment that matters so much as how much usuable energy exists for organisms to use.

It's not just semantics. Heat gradients describe a *static* phenomenon, while heat transfers describe a *process*. That's an important distinction - state vs evolution of that state.

[Putnam]

Semantics are usually pretty important in engineering

[Halnoth]

Semantics are usually pretty important in engineering

Fair point

[GoblinCookie]

As to your second question; it entirely depends on how you want to measure efficiency. In terms of energy efficiency then sure multicellular organisms are more efficient. However, there are definate draw backs to being multicellular, the biggest being reproduction. It is easier to split yourself in half to produce two than it is to grow a new organism. So, in terms of reproductive efficiency, single celled organisms are more efficient. This is partially why populations of single celled organisms can operate in more extreme environments.

However, in terms of survival, neither of the above parameters for measuring efficiency is appropriate on thier own. Many other factors need to be considered. For instance, total energy available for input into the ecosystem and total energy available at each trophic level would need to be examined to determine the likelihood of X populatIon existing.

I was talking about energy efficiency. 

[Pvt. Pirate]

the maps of the mines of moria that i found included air shafts.