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  #71  
Old July 11th, 2009, 12:34 AM
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Originally Posted by Icosahedron View Post
Arthur: The crux of my argument (about nanite goo not bottoming out) is to question whether nanoscale machines would need the equivalent energy to raise a meter scale object by 50 degrees, or whether the energy needed to break enough bonds in enough time is many orders of magnitude smaller than this.
Assuming 100% efficiency, the minimum energy required to break a molecular bond is exactly equal to the energy required to raise that substance from its current temperature to its melting point. (That's the definition of melting, the current energy state is high enough to allow the bonds to be broken - as opposed to a solid). The absolute minimum energy required to disassemble a 1 ton block of iron would be equal to the energy required to raise it to the melting point. Assemblers would need to remove that same amount of energy as waste heat as they convert a liquid to a solid.

Try melting carbon.
That's a heck of a lot of energy per molecule times a heck of a lot of molecules.

Slow or Hot are the only choices.
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  #72  
Old July 11th, 2009, 03:50 AM
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I agree slow or hot are the only choices, but it's not clear to me that keeping the machines within their max operating temperature will necessarily result in timescales that are untenably slow.

I can evaporate the 1D6 on my desk with a weapons grade laser in a nanosecond, I can dissolve it in acid in ten seconds. (which is breaking bonds and disposing of the resultant heat without raising itself to carbon-arc temperatures) Is it a problem if grey goo takes thirty seconds to dissemble it?

Right now, on the basis of the arguments raised so far, I have no idea whether it would take thirty seconds or thrirty years to do the job, so from my POV it's very firmly 'case not proven', and personally I'm inclined to think thirty seconds would be nearer the mark.
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  #73  
Old July 11th, 2009, 04:21 AM
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They'll be slower, typically by a couple orders of magnitude, than a robot of human scale doing the same task, simply because it can wick the heat away faster, further, and easier.

Note that very few structures in nature grow more than a cm or so per day. Most don't even hit 1mm per day.
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  #74  
Old July 11th, 2009, 05:33 AM
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Originally Posted by Icosahedron View Post
A billion nanites is a very, very small number. The average splodge of goo would probably contain billions of billions at least.

Icosahedron,

Okay, let's use my previous example with a billion billion nanites all making a billion operations per second over the same 167.28 hour period. You know have a whopping 19.92 kilograms of carbon after one week's work.

Don't spend it all in one place.

I'm really surprised you didn't blink about the billion operations per second per nanite statistic, that's several orders of magnitude above most proposed operational speeds. Each of the nanites in my example need to "pick & place" a carbon atoms a billion times per second.


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Last edited by Whipsnade; July 11th, 2009 at 05:34 AM.. Reason: spelling
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  #75  
Old July 11th, 2009, 04:12 PM
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Quote:
Originally Posted by Icosahedron View Post
I agree slow or hot are the only choices, but it's not clear to me that keeping the machines within their max operating temperature will necessarily result in timescales that are untenably slow.

I can evaporate the 1D6 on my desk with a weapons grade laser in a nanosecond, I can dissolve it in acid in ten seconds. (which is breaking bonds and disposing of the resultant heat without raising itself to carbon-arc temperatures) Is it a problem if grey goo takes thirty seconds to dissemble it?

Right now, on the basis of the arguments raised so far, I have no idea whether it would take thirty seconds or thrirty years to do the job, so from my POV it's very firmly 'case not proven', and personally I'm inclined to think thirty seconds would be nearer the mark.
Lasers and Acid are bad analogies. In the case of the laser, how large was the laser required to evaporate your die? Now start scaling the operating temperature using my first analysis and a nanolaser will operate at sun+ temperatures. Acid stores the energy in a chemical form and consumes itself in the process. Are your nanomachines designed to break one bond and consume themselves in the process?

The speed will be proportional to energy density which will be proportional to temperature. Living processes are the only nanomachines that we know of and they operate in a very narrow temperature range (around 20 deg C). If your man-made nanomachines can operate at 10x the temperature of organic life forms (around 200 deg C), then they will be 10 times as fast as a tree growing or a bone heals or grass decomposes. If your man-made nanomachines can operate at 100x the temperature of organic life forms (around 2000 deg C), then they will be 100 times as fast as a tree growing or a bone heals or grass decomposes.

So far, billions of years of trial and error have not produced any molecular machines that operate much above 100 degrees C, so good luck.

[as a quick aside, the temperatures given are for order of magnitude approximation only. Accurate temperatures involve degrees K, the amount that the energy exceeds ambient temperature and the efficiency of the machine. I sure don't want to get into that level of detail.]
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  #76  
Old July 11th, 2009, 04:21 PM
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I won't dispute that grey goo style nanotechnology is theoretically impossible. The arguments sound reasonable to me and my knowledge of physics is too meager for me to argue against it.

But for purposes of a reasonably-hard-but-not-fanatic SF game, is there any game reason why grey goo shouldn't work? Not in the Third Imperium, of course, because the TL is too low, but why shouldn't the Ancients have figured out a workaround? Something to do with nano-sized subspace heat sinks, perhaps?

Anyway, it's a self-contained impossibility. There aren't any unintended consequences involve. So what if you can dump a canister of goo on a scrapheap and get a spanking new Ancient war machine out of it? What are the odds you can figure out how to control it?


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  #77  
Old July 11th, 2009, 07:24 PM
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Originally Posted by rancke View Post
I won't dispute that grey goo style nanotechnology is theoretically impossible. The arguments sound reasonable to me and my knowledge of physics is too meager for me to argue against it.

But for purposes of a reasonably-hard-but-not-fanatic SF game, is there any game reason why grey goo shouldn't work? Not in the Third Imperium, of course, because the TL is too low, but why shouldn't the Ancients have figured out a workaround? Something to do with nano-sized subspace heat sinks, perhaps?
If something is impossible according to current scientific theory, then I would only put it in a Traveller game if it added a significant benefit to the campaign and if it was critical to replicate the setting (FTL drives meet this test).

I can't really see that grey goo meaningfully benefits a campaign. It's much like a ring with a dozen wishes in a D&D game IMHO and just as ill-advised.
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  #78  
Old July 11th, 2009, 08:00 PM
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It's much like a ring with a dozen wishes in a D&D game IMHO and just as ill-advised.
Probably be pretty safe in our group then

Seems we always wanted a ring of wishes but once we got one it was a long time before we used it (gotta be careful what you wish for, never know when a more important need will crop up, etc.). I think if one of us had dropped a Ring of Infinite Wishes in a game the finders would have never touched it, backed slowly away, and then run screaming from the imagined ref twists behind such an obvious trap.

Ditto for grey-goo I'd think...

"You found* it, YOU try it!"

"I'm not trying it! What if it tries to "fix" me?!"

"Well there's only a little and we don't know how much it will fix. Let's save it for a more important repair, we can fix this the old fashioned way."

* the only way I see grey-goo existing in my game would be an Ancient discovery, some limited (unknown quantity) applicator method, with no instructions and unknown capabilities...
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  #79  
Old July 11th, 2009, 11:12 PM
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Originally Posted by far-trader View Post

Ditto for grey-goo I'd think...

"You found* it, YOU try it!"

"I'm not trying it! What if it tries to "fix" me?!"

"Well there's only a little and we don't know how much it will fix. Let's save it for a more important repair, we can fix this the old fashioned way."

* the only way I see grey-goo existing in my game would be an Ancient discovery, some limited (unknown quantity) applicator method, with no instructions and unknown capabilities...
It'd be like handing a tube of cyanoacrylate to a 2 year old. Just imagine all the chaos unleashed because of some Ancient version of superglue. I think I might use this some time - it has potential. I can just imagine how many things can get stuck to a player in inconvenient and amusing ways.

"Hey, what's wrong with the air/raft? It won't move."

"Uh, I was trying to fix the chrome I bent last week 'cuz that stuff worked so great on the hull, and spilled some of 'That Stuff' on the fender and it sort of dripped onto the floor under the raft...."
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  #80  
Old July 12th, 2009, 09:50 AM
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Originally Posted by atpollard View Post
Lasers and Acid are bad analogies.
Probably so.

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In the case of the laser, how large was the laser required to evaporate your die? Now start scaling the operating temperature using my first analysis and a nanolaser will operate at sun+ temperatures. Acid stores the energy in a chemical form and consumes itself in the process. Are your nanomachines designed to break one bond and consume themselves in the process?
Not after a single bond, probably, but IIRC Drexleran nanites are expendable and self-replicating.

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The speed will be proportional to energy density which will be proportional to temperature. Living processes are the only nanomachines that we know of and they operate in a very narrow temperature range (around 20 deg C). If your man-made nanomachines can operate at 10x the temperature of organic life forms (around 200 deg C), then they will be 10 times as fast as a tree growing or a bone heals or grass decomposes. If your man-made nanomachines can operate at 100x the temperature of organic life forms (around 2000 deg C), then they will be 100 times as fast as a tree growing or a bone heals or grass decomposes.
Now that is a good layman-intelligible argument that I could use - cheers.

If the starting point is accurate.

Trees and bones don't grow at uniform speed (look at seedlings, birth and puberty - and just don't mention my damn dandelions - or roaches, or Ebola virus!). Normal organic growth rates are an optimum based on many factors and could be only a fraction of their theoretical maximum rate, but robots are gonna be designed to work near maximum all the time.

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So far, billions of years of trial and error have not produced any molecular machines that operate much above 100 degrees C, so good luck.
Yeah, but so far the machines have been made of hydrocarbons, not metal.

Quote:
[as a quick aside, the temperatures given are for order of magnitude approximation only. Accurate temperatures involve degrees K, the amount that the energy exceeds ambient temperature and the efficiency of the machine. I sure don't want to get into that level of detail.]
You 'n me both. Too much like hard work - I'm already failing to pick up Bill's billions.

Last edited by Icosahedron; July 12th, 2009 at 09:53 AM..
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