Moreno
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Posts posted by Moreno
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7 minutes ago, Bender said:
Creating a temperature/pressure difference is decreasing entropy, and that is exactly what the demon is doing.
I don't know. I think demon would decrease entropy if he increase temperature/pressure differences in comparison to some initial state. If he just starts from some initial non-equilibrium state (created not by him) and keeps this state unchanged, where do you see entropy decrease?
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1 hour ago, Bender said:
But the second law of thermodynamics dictates that decreasing the entropy (increasing enthalpy ) of a system requires more energy than the decrease in entropy.
So you just demonstrated that to be able to violate the laws of thermodynamics, you need a demon which violates the laws of thermodynamics.
But that's a point. The demon doesn't decrease entropy. It just prevents it grow, so basically keeps it at the same level.
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2 hours ago, Bender said:
Doesn't really matter. The key question is where the demon gets its energy.
I've already said. It may use some part of energy produced by the turbine.
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14 minutes ago, Bender said:
Where does the demon get its energy to perform the sorting?
I simply used your terminology. Feel free to replace "energy" with "power" which is indeed more appropriate.
I think word "energy" may be appropriate here as well, if we are trying to describe heat exchange between gas molecules and those atoms/molecules the turbine made of at the atomic level.
20 minutes ago, Bender said:Where does the demon get its energy to perform the sorting?
It may draw part of the turbine's energy.
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1 hour ago, Bender said:
I'll ignore the fact that the Earth is far from a closed system, and that it is quite unusual to talk about a closed system that includes everything.
Instead, let's focus on the turbine. You say that all the energy transferred to the turbine is transferred back to the gas. How much energy is left in the turbine after it transfers all its energy?
In other words. If I give you all my money, how much money do I have left to give Jack?
To a larger extent Earth exist in thermodynamic equilibrium with Sun as it radiates as much energy into space as it receives from Sun. We may ignore here the space rays or similar phenomena.
But let imagine for simplicity that entire Earth is surrounded from space with shield completely restricting for any radiation to come in and out. And all Earth is divided in two containers separated by molecular membrane with a demon who allows fast or slow molecules to come from one container to another, sorting them at will. All humans may live in one of part of the container together with their factories, cars, houses and entire civilization. Let say another part of container is completely uninhabitable. The air pressure in inhabitable part of container is constant and is always 10 times higher than in uninhabitable part. Air is allowed to travel from one part of container to another part through a turbine and this huge turbine powers entire human civilization. Demon allows molecules return to high pressure container by opening molecular membranes when needed. In this way the constant air pressure is supported in both part of containers and entropy never changes. Entropy would diminish if pressure difference between both containers grow larger at some point, but this is not a case as demon constantly preserves the same amount of molecules in each particular part of container. As entropy of entire system never changes, I assume will neither change its ability to perform a useful work. So, factories, cars, computers, trains will keep going forever and ever. Entropy growth = amount of useful work diminishes. Entropy never change = no useful degradation.
Turbine is not going to transfer all the energy at any given point. Turbines work smoothly.
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21 hours ago, Essay said:
Great source! Searching that led to this (Trinity College Dublin) PDF of a university class on the topic of "Planetary interiors." Sources include "Thermodynamics of the Earth and Planets," such as the graph of “Radioactive heating of Earth since formation,” on page 27.
Pages 21-27 cover "Heating of the planets," which then leads into the section on “Cooling of the Planets,” starting on page 28 (of 47).
I did not know about the significant "Heat of Differentiation" involved with planetary formation, but it makes sense.
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"For Earth think still some remnant heat of formation. For smaller planets, heat of formation may have been dissipated as quickly as planet formed."
One more argument against Pluto preserved lot of formational heat.
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8 hours ago, Bender said:
But it's a closed system where the turbine transfers all its energy to the gas atoms (I suppose you mean gas molecules). How can it transfer energy outside the system (do work) if it has already transfered all its energy to the gas?
Suppose we each have 50 euro. I give you 50 euro and you give me 50 euro and then you give Jack 10 euro. Now our total has decreased to 90 instead of 100 euro.
Why do you think it suppose to transfer energy outside the system in order to do the work? Principally we can imaging that closed system is entire Earth, and we all live inside one part of container. And huge, huge turbine located within this closed system and powers all the power grids on Earth. Heat energy has nowhere to go outside the system, so it totally conserved within it.
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I've read claims that heat pumps which are based on adsorption process are more efficient. Is it true? If yes, does it apply to any outside temperatures?
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1 hour ago, Bender said:
Then what is the point of the turbine?
To rotate and perform useful work.
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1 hour ago, Bender said:
But the average speed of the atoms decreases because some of them bounce off the turbine, slowing down.
Not necessarily, if the turbine is the part of the closed system. Then total heat energy that gas atoms transfer to turbine will be equal to total energy the turbine transfers back to the gas atoms.
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On 3/6/2018 at 8:02 AM, Strange said:
It appears you are contradicting yourself: why bring up radioactivity as a "cheap and easy" source of energy if it isn't?
It is also untrue. Nuclear power has one of the the best safety records and is one of the least polluting forms of energy generation. Which is why a low-carbon economy will depend on it for quite some time.
In any case Uranium is non replenishable. And will start to get scarce soon.
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It is assumed that classical Maxwell's demon suppose to work in cycles. So, it starts from equilibrium system, then make it non equilibrium by sorting fast and slow atoms, and reduces its entropy in this way, then system performs some useful work and when it does entropy increases and system returns to equilibrium state again. Then demon starts his work again... The common objection against it is that: "entropy of the system cannot spontaneously decrease".
But let imagine that demon never decreases entropy and entropy constantly stays at the same level. And the system never comes to equilibrium. For example, let imagine we have a container separated by atomic membrane through which individual atoms can pass and demon can sort fast and slow atoms. Gas pressure in the part A of the container is initially 10 times higher than in the part B. Gas atoms are allowed to pass prom part A to part B through a rotating turbine and perform a useful work. But once one additional atom passes from part A to part B, the demon opens a membrane and allows a fast atom from container B return to container A. So, in this way pressure and temperature in each individual part of container never changes. Possibly, in this way we are going to obtain an ideally reversible process.
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On 3/3/2018 at 1:49 AM, Frank said:
There are heat pumps that run off of fuels (natural gas) from whispergen, honda and others, but they all have their issues - noise, vibration, oil changes, expense or efficiency...
Do they have moving parts? If not, then where noise and vibration come from? How their efficiencies and power is compared to electrical heat pumps? If they are less efficient, then why?
What can be done to increase heat pump efficiencies radically at lower temperatures? For example, could use of propane instead of Freon be helpful?
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12 hours ago, swansont said:
IOW, the uncertainty is large, so we can't be sure. But that means there is no definitive evidence of some other source.
What about neutrino radiation and heat flux mismatch?
10 hours ago, Moontanman said:Dr. Herndon likes to term this beast the "georeactor".
Think of the early Earth as having been like a spherical steel hearth. A hot ball of liquid elements freshly formed out of the primordial disc surrounding our sun. The densest metals sinking down by force of gravity while lighter materials "floated" outwards. Uranium is very dense. At about 19 grams per cubic centimeter, it is 1.6 times more dense than lead at the Earth's surface. But deep within our planet density depends only on atomic number and atomic mass. Uranium, having the greatest atomic number and atomic mass, would be the most dense substance in our planet and will ultimately end up at the center of the Earth. The implications of this relatively new georeactor hypothesis are far reaching indeed. Not only does it threaten to change the way we view our own Earth and planetary formation in general but the very origin of the stars might need to be rewritten.
The mainstream hypothesis suggest otherwise:
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- Uranium 235, with a half-life of 0.703 billion years,
- Potassium 40, with a half-life of 1.277 billion years,
- Uranium 238, with a half-life of 4.468 billion years, and
- Thorium 232, with a half-life of 14.056 billion years.
- The consensus view amongst geochemists is that there is very little, if any, of any of these isotopes in the Earth's core. Potassium, thorium, and uranium are chemically active. They readily oxidize. In fact, they readily combine chemically with lots other elements -- but not iron. They are strongly lithophilic elements. Moreover, all three are "incompatible" elements. In a partial melt, they have a strong affinity to stay in the molten state. This means that relative to solar system abundances, all three of these elements should be strongly enhanced in the Earth's crust, slightly depleted in the Earth's mantle, and strongly depleted in the Earth's core.
https://earthscience.stackexchange.com/questions/4798/what-percent-of-the-earths-core-is-uranium
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I will look for more reliable link if you want.
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6 hours ago, Area54 said:
I have to assume you have me on Ignore, since you are ignoring every one of my references to the conversion of kinetic energy to thermal energy during the accretion process. Is there a reasn for this? An inconvenient truth, perhaps.
Why do you expect I suppose to argue with you? Do you think I'm an expert to prove if you are right or wrong? You expressed your opinion so I'm OK with this. If other users don't then they can contribute.
7 hours ago, swansont said:Citation?
The new measurements suggest radioactive decay provides more than half of Earth's total heat, estimated at roughly 44 terawatts based on temperatures found at the bottom of deep boreholes into the planet's crust. The rest is leftover from Earth's formation or other causes yet unknown, according to the scientists involved.
On 3/6/2018 at 6:16 AM, Area54 said:I suggest that describing hypotheses based upon sound analysis of validated data as fortune telling is an emotional characterisation that does nothing to help a serious discussion of some interesting observations.
You say "some theories suggest it does have only a tiny rocky core. The rest is the ice." I suggest rather than basing our speculations on oudated "theories" we work with something current. For example, W.B.McKinnon et al, "Origin of the Pluto-Charon system: constraints from the New Horizons flyby" Icarus 287 (2017). They note that:
New Horizon’s accurate determination of the sizes and densities of Pluto and Charon now permit precise internal models of both bodies to be constructed. Assuming differentiated rock-ice structures, we find that Pluto is close to 2/3 solar-composition anhydrous rock by mass and Charon 3/5 solar-composition anhy-drous rock by mass.
That eliminates your concern over minimal quantiites of radioactive elements.
Next, you do not need to raise the temperature from -233 C. Why would you? It doesn't start at such a temperature. You appear to be completely ignoring the conversion of kinetic to thermal energy during the accretion process. Why are you ignoring that?
Well, you believe, it seems, that all heat produced inside of Pluto is caused by radioactivity. Then without radioactivity temperature inside of Pluto would be equal to that on the surface. It would loose any primordial heat long age. So, what I meant is that it suppose to bring temperature of entire planet from -230 to 0 if we assume that radioactive elements are distributed more or less evenly. And create a subsurface ocean.
Even if the core is 2/3 of entire Pluto by mass, it doesn't make much difference as entire planet is tiny. Also, 2/3 by mass is even much less than that by volume, taking density in account.
Presently, the geologists believe that radioactive decay takes places in Earth mantle and crust, not much (if any) in the core. Do you need any links for this? I don't know if the same thing is applicable to Pluto, but still you argument have to be taken cautiously.
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18 hours ago, swansont said:
This is a pretty careless observation.
150 years ago people didn't know anything about how the atom was put together, much less the nucleus. The scale of our knowledge of the world was limited to the literally microscopic. And yet, there was evidence that something else was there — thermodynamics couldn't account for the geologic observations about the age of the earth, for example. If there's a new, exploitable source of energy out there, it is going to be outside of the parameter space we've investigated, and must be limited in extent, because we have no hints that anything is there.
"This" is still here. Researchers claim that radioactivity can explain only 55-75% of geothermal heat. Are they wrong? If not then what about the rest?
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30 minutes ago, Strange said:
But that's the point: that is NOT an easy or cheap source of energy to exploit. The fuel is difficult to obtain, it is dangerous, it is expensive to build and run reactors, it is even more difficult to decommission them, etc.
Radioactivity is outstanding for pollution and safety problem, so people can only hope that by token they will succeed much more next time.
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4 minutes ago, Strange said:
I don't see how this is going to happen. If there were such an easily available source of energy, we would have discovered it by now. We have taken the low hanging fruit: burning wood, burning fossil fuels, wind and water power, and a few others. We are now exploiting the more technologically complex: solar, fission, fusion, etc. And we are using advanced technology to make some of the older sources (e.g. wind) more efficient.
To imagine that, somehow, we will stumble across something that is cheap and easy to use, which we have somehow missed for thousands of years, seems ... naive.
The same thing people would say about radioactivity 150 years ago.
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On 3/5/2018 at 2:32 AM, Essay said:
Possibly, or possibly not.
Either way, here and now there are many ways to leverage the forces around us to create and store energy. We could build houses to extract energy from the daily cycle of expansion and contraction the materials go through as temperatures change. They even have expansion/contraction joints in bridges, but those aren't designed as power capturing devices. Our shoes, with every step we take, could be charging up our devices. Maybe someday....
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Interesting ideas. Still there is no energy source discovered which would be cheap, safe, powerful and available everywhere. I think the quest for such an energy source will continue in this millennia. Fusion can be regarded as an almost inexhaustible, but is not safe enough at modern stage and is too alien to anything that can be encountered in Earth conditions. I think it would be nice to discover some new energy source which can happen naturally in the bowels of the planets and moons.
Regarding the farther exploration I think, it would be interesting to send a probe to Enceladus which would melt down the ice and make thorough exploration of the internal ocean, its chemical composition and make detailed 3-d map of the energy sources, to understand where energy come from. Also some new measurements and calculations on tidal forces in Saturn systems wouldn't be spare.
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16 minutes ago, J.C.MacSwell said:
Why not? In this hypothetical scenario empty space would effectively be at a temperature of 0 K. Your blackbody would tend to that.and have no reason to radiate further as it reached it. The reason you can't get anything to 0 K is that there is no 0 K space around to be utilized to allow it...your hypothetical does not exist.
Maybe it wouldn't be able to reach absolute zero due to Heisenberg uncertainty principle. There always going to be some quantum fluctuations in any body and maybe it will continue to radiate because of that.
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4 hours ago, Essay said:
edit: but with the expanding universe, I'm not sure how infinitely long you could do that.
Can we harness the very expansion of Universe? For example if we capture some light from stars that became violet shifted relative to us, doesn't it mean we harness it?
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17 minutes ago, Essay said:
If you can find something like gravity or an aether that is connected to that infinity, then sure ...it is part of your local system, but in reality....
All you need to do is tap into the unlimited supply of gravititational waves washing over us daily from every corner of the universe. It's already started (plus the new reports about how "scientists have detected gravitational waves from merging neutron stars"), but as with radio waves, it is hard to collect enough energy to be useful as a power source.
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edit: but with the expanding universe, I'm not sure how infinitely long you could do that.
We are still not in the state of "heat death". Possibly it means some forces in Universe reverse entropy.
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3 hours ago, Essay said:
And in the long run, whatever you extract from the system is going to weaken the system you extract it from.
Not necessarily if we regard entire universe as a system. If this is infinite, we can extract something from it infinitely.
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3 hours ago, Sensei said:
?? Mountain peaks with 3500 km?
Diameter of Pluto is ~2376 km..
A mistyping. Farther reads 3500 meters.
2 hours ago, Essay said:I don't see what any of those facts and figures mean, in terms of anomalous heat, but is anybody saying "never?"
Whatever discrepancies you might wonder about …there are enough ways to generate heat, between gravity and pressure and the Coriolis effects of rotation as well as chemistry and turbulence, to account for a lot of ways to imagine generating some extra heat—or at least retaining and recirculating some of the heat of formation. Just think about how complex are the thin handful of atmospheric and oceanic layers here on Earth—and the tectonic layers have their own complexities as well.
There is a lot of energy around to capture, here on Earth, but it’s tricky; just like it would be on any planet, it is hard to get a good return for your efforts and investment. And in the long run, whatever you extract from the system is going to weaken the system you extract it from. In a sustainable biosphere that is likely to become a problem, in the long run. But thinking about ways to become less dependent on fossil fuels (reservoirs of chemically stored sunlight), or to offset the negative consequences of their usage, is a worthy goal; so if that is what you’re doing, keep it up!
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Possibly. I remember a decades ago some researchers were in hunt of the "cold fusion" and some of them still are.
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Maxwell's demon and the second law of thermodynamics
in Classical Physics
Posted
Still, there is principal theoretical difference between entropy decrease and entropy unchanged. This is what ideal Carnot engine does:
https://physics.stackexchange.com/questions/214346/how-is-the-efficiency-of-a-heat-engine-related-to-the-entropy-produced-during-th