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Maxwell's Demon Soon A Reality?
DMiax writes "Reuters reports that a group of scientists from University of Edimburgh may have realized a nanomolecular engine - a Maxwell's Demon. The device selects and traps other molecules based on their direction of motion. Physicist James Maxwell first imagined the nano-scale device in 1867, and the research team cites him as the basis for their understanding of how lights, heat, and molecules interact. The device is powered by light, and may spur advances in nano-scale technology to new heights in coming years."
The Wikipedia article goes to great lengths to explain how the demon can't violate the 2nd law -- that it must delete information, which increases entropy. Okay. But what keeps it from violating the 1st law: that energy is conserved?
Apology to Ubuntu forum.
Maxwell's Demon was a thought experiment about the possibility of violating the second law of thermodynamics, not a thought experiment about sorting molecules. The idea was that the entropy of the system could be decreased by the demon selectively moving fast molecules from one side of the box to the other, thereby concentrating heat.
This tech is certainly a mechanism for such sorting, but it's powered by external light, so the entropy of the system has not decreased and the second law isn't violated. So, while it's mechanically similar to Maxwell's Demon, it's dissimilar in concept (or should I say, "in spirit" - we're talking about demons, after all).
Of course, TFA doesn't have Leigh claiming that they've come up with Maxwell's Demon, just that he "credits Maxwell for establishing the fundamentals for understanding how light, heat and molecules behave."
None of this is to say that this isn't an impressive feat, and of obvious value in terms of furthering the science/technology of nanomachines, but calling it Maxwell's Demon is missing the whole point of the original thought experiment.
[this text added to waste time between hitting reply and submit]
Reality has a conservative bias: it conserves mass, energy, momentum...
"Journalist misses whole point of Maxwells demon, news at 11"
"Physics is to math as sex is to masturbation." -R. Feynman
is what I call a Maxwell's Demon
.. that the point of the Maxwell's Daemon was to illustrate a hypothetical 'perpetual motion' machine which would generate gradients with no energy input.
In the classical example, the Daemon sits at a gate between two chambers, where both are filled with particles of random velocities. When a slow particle approaches from the left or a fast one from the right, the Daemon keeps the gate shut. When a fast one approaches from the left or a slow from the right, however, the Daemon opens the gate and lets the particle pass, thus passively generating a gradient of slow/fast particles.
As to its 'energy from nothing' nature, it's been shown that the actual switching could occur with zero energy use, but (I believe) the act of resetting the Daemon's velocity measurement device would require some energy.
Long story short, the reason that the idea of a Maxwell's Daemon is important is not because it's a nanomechanical switch, but because it was thought to be an anti-entropic system with no energy use. The actual action that the Daemon was performing is quite irrelevant, and so I take offense at the title of this story. That's all.
Is this article written for scientific morons?
"it does not need energy because it is powered by light."
As I understand it, the object the demon works on has to be isolated from the universe. If this 'demon' is powered by light, its not isolated, because outside influences are acting on it.
I think maxwell's thought experiment still stands, thanks come again.
So far, the biggest impact of nanotechnology on society is that society is full of geeks who swoon at the idea of nanotechnology being the future. Why are so many nerds just dying for the nanotechnology future to get here? What's wrong with the present?
I thought the inspiration for nanotechnology came from Sci-Fi books and Star Trek. Now Harry Potter is the big inspiration?
Today, I see this Opinion Center with Intel under it. I check my Preferences to see if I can select other Opinion Centers or turn it off. I can't. So I go and take a look. It's a paid advertiser section. That's fine, but please label it for what it is, a Paid Sponsor Section. It's not an opinion center.
Mabye there's a place to make a comment or complaint about this, but it wasn't obvious so I posted it here.
"You'll get nothing, and you'll like it!"
The reason that such a demon cannot be created is that the very act of making an observation (of a gas molecule's trajectory, for instance), requires the usage of energy. And on the scale we're talking about, that usage of energy is exactly the 'work' you are doing to raise the temperature of the gas in sorting the molecules. Thus no such thing as a maxwell demon can be made, and thermodynamics is intact.
This most recent report, as stated, requires an input of energy to move/sort molecules. Thus it doesn't violate thermodynamics and it's not really a Maxwell Demon. The article seems a bit confused on this issue, stating:
I would content that the light is an input of energy, and thus saying "it does not need energy" is rather silly.
In any case, the actual research (see David Leigh's page) is about photo-activated molecular shuttles: molecules that switch between well-defined states with input of light. You can thus trap or move other molecules using light. Certainly one step towards the much-anticipated "nanotechnology" but not quite the fine control of molecular positions one would imagine when using the term "Maxwell Demon."
Pity the researchers weren't able to create Maxwell's lesser-known "Angel", a device that -- using no power at all -- sits on a barrier and sorts molecules based on their goodness. All matter composed of "charm", "up" and "top" quarks collect on one side, whereas matter composed of the hateful 'strange', 'down', and 'bottom' quarks collect on the other.
This would totally change the world in the short term by finally providing a means to mass-produce holy water, and eventually even purifying the entire world of 'evil' particles (ie collect all the hateful particles together, send them up on the 'space elevator to heaven' and launch into the void).
Pretty much, yes. The idea of Maxwell's Demon was to violate the second law of thermodynamics - once you include an external power source, its entropy increase has to be included in the system, and now you've just got a heat pump. Doing it on the nanoscale is Really Neat(tm), but it's not Maxwell's Demon.
But then, TFA doesn't have Leigh saying that it is Maxwell's Demon, just that he credits Maxwell with furthering science.
Reality has a conservative bias: it conserves mass, energy, momentum...
Most of the Maxwell's Demon experiments deal with particles which are assumed to be infinitely small and particles which are one iota larger than infinitely small.
Consider Maxwell's Demon operating on entire galaxies at a time. An infinitely large mass (typified as a black hole) has a much larger gravitational field than a mass which is one iota less than infinitely large. If Maxwell's Demon were a gravitational capacitor (ie. its effect is only realized when the gravitional field resulting from a mass exceeds a certain level but exhibits no behavior up to one iota less than that gravitational field) then the Demon could, possibly, move out of the way and selectively allow the object of infinite mass (eg. a black hole) to pass while reflecting all objects of lesser mass.
I first proposed a similar theory years ago when working for Abbott Laboratories.
the NPG electrode was replaced with carbon blac
Forget thermodynamics, is the command to start the demon /etc/init.d/maxwell start?
I notice there wasn't a schematic or diagram of the engine, but I scoured the web and managed to find one.
Here it is:
.
liqbase
This catches molecules instead of sorting them. It should be called Maxwell's cup.
God spoke to me.
That's right. Maxwell's demon is a demon. A supernatural being not subject to the laws of physics. He can arbitrarily effect the system without being affected by it. Thus there is no widening of the sytem by his introduction and no feedback effects from his actions. That's the whole point of him.
Maxwell's demon could sort a mixed bag of apples and oranges into two bags of apples only and oranges only while preserving an apples and oranges system.
If you sort a bag of apples and oranges the system is one of apples and oranges and you. I presume you are not a demon; despite what I may have heard.
KFG
I am currently working towards a PhD in this subject. I think that the first thing to realize is that he has not yet made a motor. He has molecular ratchet as proof of concept towards a molecular motor.
d f/nature05452.pdf
In layman's terms this is how the ratchet works. First, the molecule is essentially a dumbbell with a ring around it. The ring can move freely back and forth across the dumbbell, but prefers to be at either end. The dumbbell can be bent only near one end, which prevents the ring from moving. The ring catalyzes the transition from bent to strait, to allow motion. The thing is, is that the ring needs to be next to the bend for a significant amount of time to unbend the dumbbell.
So, when the ring is next to the bend, it can straiten it temporally to move across. When it is far away, it can no longer move across the bend, and since the second binding site is far away from the bend, it is stuck there. If you have two dumbbells looped end-to-end with one ring, then you would have a molecular motor. The ring is acting as "Maxwell's Daemon" to allow movement across the system.
Here's a link to the actual journal article if you care to read: http://www.nature.com/nature/journal/v445/n7127/p
I think we're seeing Cowboy Neal's Demon, a software utility that moves links about on a page to create infinite money for the developer.
Of course, such a thing can never happen in real life, so it's all theoretical.
"Lisa! In this house we obey the law of thermodymanics" - Homer Simpson.
Obviously, the article irresistably leads to a discussion of Maxwell's Demon, and how this machine highlights the thermodynamic principles that were uncovered during the examination of that wonderfully subtle and insightful thought experiment. But it definitely doesn't mean that Maxwell's Demon may be a reality than machines that exploit relativistic effects suggest that we'll be able to ride around on beams of light, as in Einstein's thought experiment. Or that we'll be able to create superpositions of alive cats and dead cats (the hot new Valentine's gift for 2007 -- all the furriness and half the upkeep!)
As long as there's still some hope that the cat may be alive, it will exist in a superposition such that the living-cat component has some non-zero weight, which we will call XL.
Poser!!!! ;-)
It's all a matter of being extremely nearsighted.
Well, I got to go back to my sorting.