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(Ed) Nanomachines

hellaeon said:
http://news.ninemsn.com.au/article.aspx?id=224868

Can someone explain what is a 'molecular force' and how does it differ to say a force I excert with my strength or the force produced from driving a car at 60kph.

Thanking you.
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I'm not even close to a physicist but I'd say the difference is one is operating at the molecular level, the other isn't really per say. The force that makes your car move is a chemical process that works with a series of parts. Molecular force would be more simple? A nanomachine would be something entirely different and I imagine the levels of force required to manipulate atoms would be immense!

I'd like those machines in my body though that way it would be possible to live forever and to surpass our limited humanity. Shame, I probably won't live to see it or have the power to influence it.
 
With statements like the one below in it, I'd reserve judgement until reading a published paper.
As Maxwell had predicted long ago, it does not need energy because it is powered by light.
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They also talk about it being a molecular machine but also say it's one atom. So I'd guess this is a mangled bit of science reporting.

So it's hard to say what particular "molecular forces" might be at work here. But, in general, molecular forces are fundamentally different from the forces you mentioned. The differences are in the details of how the same forces work at small levels. The biggest differences is that at human sized levels at lot of random effects tend to average out. At nano scales the random events don't average out. Your muscles don't care if a few (few might be millions in this case) atoms aren't in the right place but a molecular device might fall apart if only one atom is out of place.
 
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I'm on a slow connection right now so I can't look to hard, but I can't find any other reports that seem to match this. Everything I find about David Leigh seems to be about the earlier "water drop mover" the article mentions, not about this new development.
 
Maxwell's Deamon was a thought experiment to violate the third law of thermodynamics:

the demon would only let faster molecules through in one direction and slower ones in the other.

I believe it was used in working out the theoretical energy cost of information processing... (Please don't quote me on that)_

Jim

If you want some *good* news coverage of nanotechnology I'd recommend the Materials Research Society email alerts:

http://www.mrs.org/s_mrs/index.asp

Jim
 
Don't recall Maxwell thinking of information processing, but one of the more recent proofs against Maxwell's Daemon was by Bennett who analyzed it in terms of the information processing costs of the "Daemon". He pointed out that the changing information state inside the Daemon was a hidden cost.
 
RecoveringYuppy said:
Don't recall Maxwell thinking of information processing, but one of the more recent proofs against Maxwell's Daemon was by Bennett who analyzed it in terms of the information processing costs of the "Daemon". He pointed out that the changing information state inside the Daemon was a hidden cost.
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Yup, thats what I meant, thanks for the clarification :blush:
 
I can't speak for the work being described by this article, but the article itself is pretty bad. It states, "As Maxwell had predicted long ago, it does not need energy because it is powered by light." That statement contradicts itself. Light IS a form of energy, so if it's using light for power, it does indeed need energy. That's highschool-level science, and if the journalist flubbed that, I wouldn't want to trust his characterization of anything else that was done.
 
Hunted this up which has links to several articles with more detail.

It's worth keeping in mind that according to the Fluctuation Theorem, the 2LOT is only an approximation that becomes more and more true the larger the system gets, but less and less true the smaller it gets. So even if the action of this particular molecule appears to violate the 2LOT, overall it is preserved and energy is conserved. This was very much the sort of thing that the OP for the recent thread on this very subject had in mind, I think.
 
hellaeon said:
Can someone explain what is a 'molecular force' and how does it differ to say a force I excert with my strength or the force produced from driving a car at 60kph.
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This is a rather complex subject, but I'll do my best to do it justice quickly.

At the most basic level, molecular forces do not differ from the force you produce by exerting your strength. Driving a car does not produce force; force is, however, exerted by the tires against the ground, producing motion of the car, and force is also exerted by the burning fuel-air mixture against the pistons, by the pistons against the connecting rods, by the connecting rods against the kingpins, by the kingpins against the crankshaft, by the crankshaft against the flywheel, and so on through the transmission and differential and axles and wheels to the tires.

The thing to keep in mind is that all of these forces are transmitted between atoms; and atoms are made of light, negative electrons, whirling (not really, but that's close enough for rough understanding) around the very heavy nucleus, made of heavy, positive protons and heavy, neutral neutrons. That means when two atoms come close to one another, they exert forces on one another because of their electrons pushing against one another due to them being the same charge. It's a little more complex than that, because the electrons can be pushed aside, or interact with one another, in various other ways; but essentially, it's all about the electrical forces acting between the atoms. And in that way, the forces in the car, the forces from your muscles, and the molecular forces mentioned in the articles are all the same basic thing.

That thing is the
1. electromagnetic force,
and it is separate and different from
2. gravity,
from
3. the force that keeps the protons in the nucleus, called the strong or color force,
and from
4. the force that makes some atoms radioactive, called the weak force.

These four forces are, as far as physicists can tell, the only forces there are. Every other force we know of is essentially one or more of these four acting in one way or another.

hellaeon said:
Thanking you.
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Sure. Hope that helped. Ask questions if you have more.
 
Thanks a lot people and thanks for the extra articles.
I have had a few dabbles with bits and pieces of atomic level physics and the like but not enough to recognise some of the flaws in the article. These things need to be read and re-read to reinforce. the article certainly sounded amazing and so thanks for a good analysis. Good to get to the crux. Your explanations have certainly helped what I want to read next
 
I have found a couple of links where I get pretty good coverage of these subjects (one is the UK institute of Physics) and the other the Materials research Society.

IOP link:
http://nanotechweb.org/articles/news/6/2/2?alert=1
Maxwell's demon tamed

2 February 2007
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The MRS email alert seemed particularly comprehensive:


You have to register but, if you are interested, it is probably worth it; here is their current sample:

http://www.mrs.org/s_mrs/doc.asp?CID=1803&DID=178230&css=print
http://www.mrs.org (I don't know if their sample address changes...)

Jim
 
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