[fennecfoxen]

Gray goo is only an existential threat to civilization if you have magical nanomachines that can metabolize useful energy out of concrete, sand, glass, and dirt, in an exothermic reaction. Also, it would help a lot if these fragile little machines are also magically immune to excessive heat, and if you ignore them facing down bacteria and other life forms.

While you work on these problems I’ll be over here worried about the pollution-like side effects of ordinary endothermic nanomachines.

[clSTophEjUdRanu]

Bacteria already tries to do this. Leads me to believe it's impossible.

[SAI_Peregrinus]

Bacteria are the biggest argument against grey goo. They already are, they already exist, and they're already everywhere, yet things other than bacteria still exist. They've had several billion years of evolution to work on it too.

They're probably in local maxima, not in any global maximum, but it's also likely that there is no single global maximum given how different the requirements are for using different energy sources.

[Symmetry]

The thing I would worry about it replicators that use stronger chemical bonds than bacteria do and can eat bacteria but can't be eaten by bacteria. They would probably have to reproduce much more slowly due to higher energy requirements but if they end up eating everything in the long run it might not matter.

[DagAgren]

If using stronger chemical bonds was advantageous, bacteria probably would be doing it already.

The weak bonds is what complex chemistry and thus complex functionality possible. Stronger bonds is dead matter, and dead matter does not compete.

[philipkglass]

Incorporating fluorine in a molecule offers additional flexibility over the more common chlorine and bromine compounds commonly found in natural products. For example, the fluoroquinolone antibiotics are distinguished by their introduction of fluorine, yielding compounds more effective than found in nature.

There are a few fluorinated natural products made by wild organisms, but they are very rare considering the elemental abundance of fluorine on Earth and the high utility found for fluorine in pharmaceutical development:

https://www.ncbi.nlm.nih.gov/pubmed/23034231

The strong bonds formed by fluorine, and its formation of insoluble compounds with alkaline earth metals, probably explains the rarity of natural fluorinated products. The fluorinated natural products are no more "dead matter" than other poisons evolved by plants against herbivores, but it's hard to evolve out of local minima that exclude fluorinated compounds.

[carapace]

I suspect that multi-cellular life is the art form of unicellular life.

We are art made by microbes. (I like to think.)

[gHosts]

Arguably you're just a great big pile of grey goo.

ie. It's not an argument against grey goo, it's an argument the grey goo catastrophe rules everywhere and has done so for eons.

[pmoriarty]

"Bacteria already tries to do this. Leads me to believe it's impossible."

This is like saying "no bird can fly faster than the speed of sound therefore flying faster than the speed of sound is impossible."

[DagAgren]

Not really. Flying faster than the speed of sound without complex supporting industry is not possible. Flying faster than the speed of sound is not sustainable, it is something we have to work very hard to achieve, and the second we stopped trying very hard to do it, it would cease to happen.

Grey goo, on the other hand, has to be self-sufficient and sustainable to exist.

[ben_w]

On the other other hand, something only needs to be able to eat us to be a threat. A slightly better bacteria could count.

I wouldn’t call that “grey goo”, but the threat model is a spectrum not a Boolean.

[isaacgreyed]

I would suggest a bird would gain very little from going so fast

[mr_toad]

Your immune system has to actively defend against bacteria and fungi that would quite happily eat you.

Without any immune system you’d rot like a corpse.

[ASalazarMX]

In their defense, they're competing with organized (colored?) goo like us. We take many resources that would be gray goo otherwise.

[nnq]

You don't need to "metabolize useful energy out of concrete, sand, glass, and dirt" to have a nightmare scenario...

Anything that can metabolize lots of kinds of multicellular living matter could can do insane amounts of damage even if it's not a pathogen... for example agriculture is quite frail and we depend on it!

[fennecfoxen]

That's not really grey goo, in the typical use of the term; that's just a novel agricultural pest.

[freyir]

a hypothetical global catastrophic scenario involving molecular nanotechnology in which out-of-control self-replicating machines consume all biomass on Earth while building more of themselves

It’s right there in the first sentence. Nothing about eating concrete or sand.

[m3kw9]

Can’t create atoms out of thin air, maybe you can but that isn’t enough to replicate rapidly

[knodi123]

I'm fairly confident that gray goo, as described in dystopian sci fi, is impossible due to some of the consequences of entropy and its inevitable increase.

That is, the tinier a machine, the more susceptible it is to breaking down due to wear and tear. And the more energetic a machine, ditto. So incredibly tiny, incredibly energetic machines, would have a minuscule lifespan.

And that's not even touching on the issues of power supply and storage.

I think AI is a much more existential threat than gray goo.

[NotSammyHagar]

I don't know. Imagine a virus that is 100% lethal to humans. The flu and other virii are in a sense a kind of living organism focused grey goo because there's nothing that stops a new virus from evolving and killing all living members of a species, what's left rots. There probably exists something that could kill all of us and we'd be rotten meat after we are dead. A virus uses our metabolic energy to make new copies of it and doesn't kill us immediately so that we can spread it.

[carapace]

You know there's a fusion generator in the sky.

[DagAgren]

And we already have microscopic machines that use it for power, and we know what they are capable of.

[101404]

There is Clarke's 3rd law though:

https://en.m.wikipedia.org/wiki/Clarke's_three_laws

[Filligree]

Clarke's third law is largely about fiction. It's a rule of thumb for writers, not a rule for reality.

In reality there are limits; there's no reason to think technology can improve indefinitely. We may still be far from those limits, as e.g. Drexler's books show, but fundamental rules such as "Effort requires energy input" are unlikely to ever change, and it's equally unlikely that most modern scientists would regard limit-tech as being magic.

As for the average guy on the street, he probably considers computers to be magic...

[Causality1]

Humanity has existed for a hundred thousand years and civilization for ten thousand and you think two hundred years of the scientific era has us within spitting distance of the end of knowledge? We can't even come up with models that consistently explain what little we're able to observe like gravity at all scales. As long as gaps like that exist we know we're wrong at a fundamental level. We could be as wrong as Newtonian physics or we could be as wrong as a bunch of Flatlanders. There will be limits, but they may be so far beyond our ken our current brains aren't even capable of understanding them.

[ben_w]

I think the argument isn’t that we’re in spitting distance of the end but that we can, if you will excuse the metaphor, recognise the distant peak of the mountain representing it.

Even extrapolating Moore’s Law’s exponential growth of x2 per 1.5 years would still take ~200 more years to reach the limits of computation — Improvements to particle accelerators aren’t anywhere near as rapid — so we have a long way to go before we reach the end of experiment even if we improve as fast as possible and have almost no surprises.

Not that I disagree with your general premise that some massive surprise could be waiting for us; I happen to think there is, and I get the impression that it’s totally unconventional in the physics community to say “at least one of GR and QM is wrong, but we don’t have any experiment that tells us which”.

[fennecfoxen]

> Not that I disagree with your general premise that some massive surprise could be waiting for us

I hazard that should we find such a surprise, it will be under somewhat extraordinary conditions not commonly found in nature, and quite likely ill-suited for power generation on the nanometer scale.

[ben_w]

Agreed.

I’m not a betting type, but if I had to take a bet I would expect it to be ~”and this is how the conditions of the Big Bang can be recreated and exploited to make something that looks like a star but which will exist forever. Also the interior of our fake star is now a new universe 50 billion light years across even though the outside circumference is ten light seconds.”

Not very useful for cell-scale engineering. Might count as “magic”, but the bigger-inside thing is a serious idea for making the Alcubierre drive less unphysical.

[goatlover]

We do have that kind of knowledge when it comes to thermodynamics and the limits of computation, though. And Newtonian physics was incomplete, not wrong.

[ekianjo]

> Any sufficiently advanced technology is indistinguishable from magic.

Any sufficiently advanced technology does not break the laws of physics anyway.

[101404]

Sure. But neither does the "spooky action at a distance". And we still can't explain it.

[goatlover]

We can if we ditch particles for fields as the fundamental building block.

[scrumbledober]

but that kinda hurts my brain though

[asdfasgasdgasdg]

While the law is interesting, it mostly applies to science fiction. We can't presume that said sufficiently advanced technology is physically possible -- in fact, the opposite seems decently likely.

[101404]

Not really. Just show your mobile to a guy from the 16th century and see what he thinks.

[fennecfoxen]

I'd like to think that we have a certain level of understanding of topics like the conservation of energy. We understand that it is possible in theory to liberate enormous amounts of energy from the rest-mass of ordinary matter. However, we also understand that, in general, matter is stable, and this liberation takes place either very slowly, or under extremely energetic conditions. We also understand that building microscopic structures capable of resisting extreme conditions is an extraordinarily difficult engineering problem. Nanostructures that could bring these conditions about? Even more so.

Our level of understanding seems, broadly, a better level of understanding than a 16th century layperson would have of topics like the existence of electromagnetic waves and electricity, let alone the batteries, semiconductors, and software applications of semiconductors which ties them together.

[lurquer]

He'll think more or less the same thing that 99% of people in the 21st century think.

That is, very few people know -- or care to know -- how their cell phone works. Those on this forum, of course, do. But, to the average man-on-the-street, its magic.

The difference is that a modern person knows that if they really wanted or needed to, they could find resources to explain how their phone works (beginning with electricity, electronics, programming, etc.)

The 16th century guy would be at a disadvantge for he'd correctly intuit pretty fast that nobody on the planet knows how it works and there is nowhere to get the info.

[asdfasgasdgasdg]

To be clear, I'm not saying that no magical-ish tech will ever exist in the future. I'm specifically doubting the physical possibility behind the imagined gray goo tech.