The physics of why hot water sometimes freezes faster than cold water - <AUTHOR> https://www.smithsonianmag.com/smart-news/new-experiment-shows-why-sometimes-hot-water-cools-faster-cold-water-180975543/ <comment><USER2> Arxiv link to the actual paper: [https://arxiv.org/abs/2008.02373](https://arxiv.org/abs/2008.02373)

Looking at the actual graphs, what is presented appears at first blush to be a bistable system prepared in its higher-energy stable state. (Or at least, prepared in a way that several of its constituent subsystems "fall into" that state.) Transitions to the lower-energy stable state require overcoming a barrier, and jumping over that barrier is of course faster at higher temperatures. At lower temperatures you essentially have a slow internal self- heating from the periodical jumps of subsystems through this forbidden region by thermal excitations, not unlike phosphorescence having to tunnel through an energetically forbidden region; this self-heating prevents the thing from cooling down fast enough.

Actual applicability to water is kind of harder to evaluate. I've long thought that you could indeed have an Mpemba effect caused by persistent induced convective currents in a fluid: so a hotter thing placed into a fridge might create a more dramatic internal flow as its outer boundary layer cools and changes in density, the convective current would certainly increase the slope of the hotter cooling system beyond the naive temperature scaling, and might then persist as a physical difference even after the two systems arrive at the same temperature, leading to a faster cooling speed of the convective system that "started out hotter". But I mean I have never really done experiments to confirm that sort of thing.

<comment><USER3> You've put into scientific terms what I can't cause it's been too long since I've done any physics.

In layman terms, the molecules in hot water are bouncing around more and thus easier to form crystal structures because of the higher-energy state. Molecules at room temperature have to be forced into crystal structures which takes longer.

<comment><USER4> A little more explanation is required, since the boiling pot still needs to pass through room temperature on its way to freezing, and it's not clear how at that point it has a head start on the other room temperature pot.

<comment><USER5> Especially since there is no such thing as water memory.

<comment><USER6> I wonder how many kids watching frozen 2 will subconsciously accept "water has memory" as a fact and believe it in 20 years time, being unable to source why they think it, just something "they know"

<comment><USER7> That's something people have believed basically forever. The most modern example would be homeopathy, which is explicitly based on the idea that water has memory and significantly predates Frozen 2.

So, the answer to your question is "a really large number", but it's not obvious that Frozen 2 would have influenced them.

<comment><USER8> It would be more correct to say that homeopathy _became_ explicitly based on water memory after atomic theory and the size of atoms achieved mainstream acceptance. And while Dalton and Avogadro had certainly made convincing arguments based on chemistry in the early 19th century, and thermodynamicists like Boltzman had models of heat and heat transfer that seemed to depend on particles, it wasn't until after Einstein's paper on Brownian motion and Rutherford's interpretation of the Geiger-Marsden experiment that homeopathic dilution just being dilution became an unsustainable notion.

It was always a silly notion, especially when numbers like 30C - a dilution of one part in 10^60, or one molecule of the target substance in 3 × 10^34kg of water, _after_ you understand what molecules are - were being thrown around, but there was at least a plausible explanation before, say, WW1.

</comment></comment></comment></comment></comment></comment></comment><comment><USER9> Once upon a generation ago, I worked at an ice rink. "Cleaning the ice" using an ice resurfacer involves cutting the top 1/16" of ice off and laying down new water. Hot water is preferred because it freezes faster and produces a denser sheet of ice; a denser sheet of ice is going to be better for skating.

It's nice to see more papers on it.

<comment><USER10> Hot water and is preferred because it has less gasses dissolved and this way it produces clear ice. Also cold water could freeze too quickly, if the rink is very cold, before it has time to spread evenly.

I am pretty sure any tiny time difference, if it exists, would not be worth the hassle of supplying hot water.

<comment><USER11> > Hot water is preferred because it has less gasses dissolved

true, but while the temperature decreases the air dissolves back in.

What makes ice clear is directional freezing, the sheet freezes from below, pushing the gases up. You can try that in your freezer by putting in it a styrofoam box full of water. Just in this case it will freeze from the top and push the gases downwards. The upper layer will be crystal clear.

<comment><USER10> I did this experiment many times, myself. If you start with boiled water you will get much thinner layer with bubbles.

Air actually takes a bit of time to diffuse into water if it isn't getting mixed with air (that's why your fish tank needs air to be actively mixed with water). Starting with thin layer of water that was recently hot gives not enough time for any significant amount of air to dissolve.

I work with electronics. I use electronic water for parts cleaning. Electronic water is pure water, distilled, deionized, degassed (no oxygen in it) so it does not oxidise copper traces. It does go bad (bad meaning gets oxygen dissolved) when opened, but think more like hours or even days if proper precautions are taken (don't shake or stir once the container is opened).

<comment><USER12> Does it taste any different than normal tap water?

<comment><USER10> It has awful taste close to regular distilled water. Mineral profile greatly influences water taste.

</comment></comment></comment></comment></comment></comment><comment><USER13> Somehow this article provides no explanation at all of how this actually happens. Perhaps the research being reported doesn't really have an explanation either, it's just more demonstration under more controlled conditions?

Or the explanation as it were is just "abstract" and "geometrical", basically just mathematical?

Very odd phenomenon.

<comment><USER14> The fact is, you do need to get rid of more heat when using hot water.

Ergo, some sort of self-reinforcing feedback loop must appear when you use hot water, that sucks heat out of it faster. If you use cold water, the "turbocharged" mechanism does not operate for some reason, and heat is lost at a lower rate.

I've no idea what that mechanism is. It's nonlinear behavior for sure.

<comment><USER15> A hypothesis I've heard is that the hot water is more likely to produce currents inside the water, as there's more of a temperature difference between the inner water and the water right at the edge. These currents then cause the water to cool more uniformly as opposed to outside-in. I believe the person I heard this from tested this by adding baffling to the container to prevent currents, but I'm not sure what the results of that experiment were.

<comment><USER16> That's baffling, jakear.

<comment><USER14> Cell convection is relatively common.

For example, this is why large amateur telescopes perform worse for about an hour after they're brought outside: the mirror is "hot" compared to the air, so a network of toroidal convection cells (spinning doughnuts of air) forms on its surface, ever so slightly messing with the rays of light.

There's actually an attractor for some of these networks (speaking in general), where they form hexagonal cells. Of course, in most cases, it's more disorderly than that.

I'm not sure how a turbocharged network could form, but I'm looking forward to learn more on this topic.

<comment><USER15> I think they were making fun of my spelling, but I'm not sure because I don't know if I was wrong.

<comment><USER14> Oh, I see. I think it was just a simple play on words.

<comment><USER16> Yes! Just word play. There's nothing wrong with Jakear's spelling or his comment, which was informative.

Next time I will smile :-)

</comment></comment></comment></comment></comment></comment></comment></comment><comment><USER17> I have a vivid memory of being taught this in 2nd grade, probably because it seemed (and still seems) extremely counterintuitive. I think the intuition given was that hot water is less dense than cold water, so the coldness can more easily permeate through the liquid (I imagine a vein-like pattern). Something like that.

At least according to Wikipedia, it seems that it's a bit more complex: [https://en.m.wikipedia.org/wiki/Mpemba_effect](https://en.m.wikipedia.org/wiki/Mpemba_effect)

Anyways, I've been repeating this fact for 2.5 decades, so shout out to my teacher for blowing my young mind.

<comment><USER18> Cold is not something that can penetrate.

Cold is merely a relatively low amount of heat energy per unit of mass.

When something cools heat energy is conducted/convected/radiated away from an object causing it to have a lower amount of heat energy per unit mass.

<comment><USER17> Admittedly, my understanding of thermodynamics has not progressed much beyond the 2nd grade level (aside from a class on PDEs giving me at least some enhanced intuition). My takeaway from the PDE class was that anything beyond a simple textbook problem needs to be simulated and/or observed experimentally, rather than solved for analytically.

But other things being equal, wouldn't cold air permeate a less dense barrier (say a layer of insulation in a home) more easily than a dense barrier? Just as water (or cold air) would permeate soil more readily than rock.

<comment><USER18> Cold AIR permeates. That is correct. But there is no physical concept of COLD. The physical concept that exists is heat energy. Temperature is defined as the amount of heat energy per unit of matter. When something gets colder the physical process happening is that heat energy is leaving the thing and being transferred somewhere else/being converted to another form of energy.

So when cold air comes into a house heat energy is transferred from e.g. the material that makes up the wall into the air warming the air and cooling the walls. The cold air is replacing warm air which moves out of the building.

</comment></comment></comment></comment><comment><USER19> All the talk in the comments about dissolved oxygen brings back a few memories of student lab work that went wrong. I was given a freeze-pump-thaw protocol to follow in order to remove oxygen from a copolymer solution. Basically we used liquid nitrogen to freeze the mixture, then used a vacuum pump to remove the gases above the mixture. When we thawed the mixture, the dissolved oxygen would escape, in order to equilibrate with the amount above the surface. I repeated this for a few cycles. It was all done with sealed glassware.

Unfortunately, the glassware kept cracking during the thaw stage. This went on for a couple of months, till finally my supervisor reviewed the procedure, and realised that, whether cracking occurred, depended upon the relative concentrations of the two polymers. If I recall correctly, the problem occurred when the polymer with the lower freezing point (which, thereby, thawed first) was present at a lower concentration. It was basically trapped inside the other still-frozen polymer, and expanding, as it thawed ... till crack!

The solution was surprisingly simple. Change the method. Bubble nitrogen through the mixture to drive out (sparge) the oxygen. Replacing the oxygen with nitrogen was beneficial, as nitrogen didn't interfere with the copolymerisation reaction.

The main problem was that I had lost two months of experimental time, and this was just the start of a series of experiments and instrumental analyses. It was now Easter and the deadline to hand in my student thesis was early December.

Please don't believe anyone who says students have an easy life.

</comment><comment><USER20> I read the whole article and couldn't understand how or why this happens. Is the reason behind this unknown?

<comment><USER21> My high school chemistry teacher simplified it down to the greater "rate of change" of temperature dropping, for the hot water, causes it to end up freezing faster than the cold water.

<comment><USER22> The rate of change would slow down as it approached the colder temperature though, would it not?

</comment></comment></comment><comment><USER23> Just a few days short of 35 years ago, this came up in "The Straight Dope" [1].

[1] [https://www.straightdope.com/columns/read/422/which- freezes-...](https://www.straightdope.com/columns/read/422/which-freezes- faster-hot-water-or-cold-water/)

<comment><USER24> Random tangent: TIL that The Straight Dope predates the web and was originally a newspaper column.

<comment><USER25> Well I'm officially old because I:

1) didn't know Cecil Adams still existed.

2) still remember looking forward to the Straight Dope in my weekly alt-paper.

</comment></comment></comment><comment> m-i-l This was known by many Antarctic scientists before 1963. I remember my dad telling me you could throw boiling water into the air and it would freeze into millions of tiny ice crystals before reaching the ground, but that the same wasn't true of cold water. I think he said it was due to thermal inertia.

<comment><USER26> That sounds like a totally DIFFERENT effect, almost certainly caused by droplet size.

<comment><USER27> It could be the same.

I always learned the explanation as: 1\. Cool to freezing via evaporation. Because this goes as T^4, the time difference is negligible to reach 0°C. But...hot water loses more volume. 2\. Freeze, bit now you need less energy to freeze less material.

I did this at home, and the simple check worked: volume was lower in the frozen hot water.

This explanation might be wrong! But it works out in simple tests and mathematically.

</comment></comment></comment><comment><USER28> I'm not 100% sure it is the same phenomenon but growing up in a very cold climate where I had to park my car outside in high school I remember many times getting into the car where a half full Poland Spring plastic water bottle would sit with water. If I tapped the bottle - the entire thing would freeze in under a second. It looked amazing.

(I always thought it was a pressure thing - but not positive if that is what the article is describing or something more nuanced)

<comment><USER29> there is a similar inverse process for hot water as well... if you take a very very clean and perfectly smooth surfaced (on the inside) cup/glass and microwave it to just before the point of boiling, then drop anything into it (sugar, coffee, a teaspoon... pretty much anything) it will _very_ energetically, instantly boil.. often vertically... be careful performing this experiment.

Edit: here this will help explain it [https://www.animations.physics.unsw.edu.au/jw/superheating.h...](https://www.animations.physics.unsw.edu.au/jw/superheating.htm)

<comment><USER30> Why I never boil anything in a microwave.

Because as you say it explodes when you interact with it and are therefore are close to it rather than when it's sitting safely inside the microwave.

</comment></comment></comment><comment><USER31> If you put warm water in your ice try, you can get clearer ice near the surface, because the ice will freeze from the top surface instead of from all sides at once trapping bubbles of air with no where to go :D

<comment><USER32> That's interesting. But don't drink the hot water from the hot water tank. It can be dissolved with unhealthy minerals and chemicals. A few years ago, I had to replace a couple of hot water tanks. When I drained them, the last few gallons at the bottom of the tanks looked like yellow vomit, it was seriously disgusting.

<comment><USER33> Which makes me think ... always ask for "no ice" when you are at a bar or restaurant. Unless you know how they make it.

<comment><USER34> I think that's a pretty un-based fear. Almost certainly any restaurant, and especially a bar, will use a professional ice making machine. At the volumes if ice they go through, it wouldn't make sense to make it in any other way.

</comment></comment></comment></comment><comment><USER35> There has been some controversy about this for years, see for example:

[https://www.chemistryworld.com/news/mpemba-effect-in-hot- wat...](https://www.chemistryworld.com/news/mpemba-effect-in-hot-water-after- doubt-cast-on-its-existence/2500087.article)

[https://www.repository.cam.ac.uk/handle/1810/263847](https://www.repository.cam.ac.uk/handle/1810/263847)

This new paper may prove to be conclusive in supporting its existence, but as I'm not an expert I'll give it some time in peer review before coming to any conclusion.

</comment><comment><USER36> This might be a better link: [https://www.sciencenews.org/article/physics-new- experiment-h...](https://www.sciencenews.org/article/physics-new-experiment- hot-water-freeze-faster-cold-mpemba-effect)

Punchline seems to be that "hot" but out-of-equilibrium material cannot be summarized by a "temperature", providing many paths towards freezing (on the landscape of microstates), some of which could (efficiently) circumvent the "low temp" state.

</comment><comment><USER37> A marginally related question for the experts here: I love extremely cold water, juices and drinks, so I often keep them in the freezer in plastic bottles. Now, if I take out a bottle of something that is just about to freeze, as soon as I open the bottle, it almost immediately freezes although I am certainly not removing heat from it but actually doing the opposite by keeping it with my hands, not to mention the warmer environment in which it is now. I couldn't explain it in any other way than with the different pressure, that is, the water expands when it freezes, so the almost freezing liquid is already under higher internal pressure compared to the moment it was closed, but as soon as I open it the pressure drops abruptly, which would be enough to compensate for the higher temperature, de facto freezing the water.

Is this correct?

</comment><comment><USER38> This is one my favorite science stories. A tale of how truth eventually surfaces and holds in front of ridicule.

[https://en.m.wikipedia.org/wiki/Mpemba_effect](https://en.m.wikipedia.org/wiki/Mpemba_effect) See the section called "Mpemba's Observation"

</comment><comment><USER39> Perhaps it has to do with the increased turbulence in the hotter fluid? This would be a result of the higher saturated vapor pressure of the liquid leading to greater evaporation/boiling. Even as it cools down the higher temperature difference between the hot fluid and room temperature should produce a more turbulent boundary layer along the surface of the water.

The turbulence will reduce the thermal resistance associated with laminar surface air films on colder surfaces, which would normally be insulating surface, so you'd get a faster heat loss then with a more stagnant layer of cold water.

</comment><comment><USER40> Sometimes when we are so familiar with something, we forget how special it is.

Water is really amazing. It expands when it freezes. Hot water freezes faster than cold water. It dissolves almost anything, but not too fast.

</comment><comment><USER41> Suggested explanations

[https://en.wikipedia.org/wiki/Mpemba_effect#Suggested_explan...](https://en.wikipedia.org/wiki/Mpemba_effect#Suggested_explanations)

</comment><comment><USER42> We tried to replicate this for one of the kid's elementary school science fair project. We were unsuccessful, but the judges really liked it anyway.

</comment><comment><USER43> yes faster. but not earlier.

<comment><USER44> came here to say this. the headline for this finding is almost always misleading.

<comment><USER43> Yes, exactly.

</comment></comment></comment><comment><USER45> Emphasis on "sometimes".

<comment><USER46> Yeah but a reproducible sometimes is pretty amazing. Sounds like some interesting applications await.

</comment></comment><comment><USER47> I wonder if this is a right analogy. Imagine two cars one going fast, one slow. If driver of the fast car steps on the break harder than the driver of the slow car, he will stop faster. The temperature difference is similar to how fast you step on the break.

<comment><USER48> But cooling rate is proportional to the temperature difference (see Newton's law of cooling). Thus the hotter water may start cooling faster, once it reaches the initial temperature of the cooler water, it would cool at the same rate as the cooler water did initially. It then couldn't possibly reach freezing point earlier.

But in some conditions it does, which is the surprising result.

<comment><USER49> Hot water freezing faster in an ice cube tray is commonly reported, a bunch of reasons could explain it. Evaporation can reduce the volume of water, and the smaller volume freezes faster. A hot tray will settle into any ice build up in the freezer (which is common) increasing the rate of heat exchange. Hot water will create currents in the air and water (driven by the higher water temperature) which help the exchange. On the flip side lower temperature differences will often cause a stagnant layer that will reduce the temp exchange, much like sitting in a cold pool which gets better if you want a few seconds... until you move again.

The reported experiment reduces the variables by using glass instead of water, so there's no internal flow, but that doesn't stop the airflows generated in the air.

</comment></comment></comment><comment><USER50> > Hot Water Sometimes Freezes Faster Than Cold Water

No it doesn't.

Unless you want to word play between English and really specific small technical processes, perhaps.

What's interesting is it's an old urban legend the predates Usenet.

Usenet did kill the glass is a liquid legend though.

<comment><USER50> We all get the Mpemba effect is totally fake right?

You all own freezers so you can test it for yourself, it was found by a child making icecream so it will be easy!

And if you're the !first! to put it on Youtube that'd be cool.

Sciencium talks about it here if you want an ok run down and how it's not real - [https://www.youtube.com/watch?v=SkH2iX0rx8U](https://www.youtube.com/watch?v=SkH2iX0rx8U)</comment></comment>


Collateralized Loan Obligations Are Riskier Than Most Realize - <AUTHOR> https://www.bloomberg.com/opinion/articles/2019-03-03/collateralized-loan-obligations-are-riskier-than-most-realize <comment><USER2> In case you didn't see the movie: [https://www.youtube.com/watch?v=xbiDrzTd8fE](https://www.youtube.com/watch?v=xbiDrzTd8fE)</comment>


Show HN: Recipe Fiddle – Recipe book generator - <AUTHOR> https://recipefiddle.com/blog/

<comment><AUTHOR> Last year I collected, with permission, shy of two dozen recipes from /r/recipes and related subreddits.

Over the last few years, I've built a web site that allows people to create recipe books automatically. The web site (now in beta!) separates recipe content from its presentation.

* [https://recipefiddle.com/book/examples/recipefiddle_reddit-r...](https://recipefiddle.com/book/examples/recipefiddle_reddit-recipes-svedish.pdf) \- book design 1

* [https://recipefiddle.com/book/examples/recipefiddle_sweet_tr...](https://recipefiddle.com/book/examples/recipefiddle_sweet_treats_cards.pdf) \- 3x5" card design

* [https://recipefiddle.com/book/examples/recipefiddle_reddit-r...](https://recipefiddle.com/book/examples/recipefiddle_reddit-recipes-modern-square.pdf) \- book design 2

I would like to learn what would make it useful for you. The two-minute tutorial ([https://www.youtube.com/watch?v=ktK_B0uKKUc&hd=1](https://www.youtube.com/watch?v=ktK_B0uKKUc&hd=1)) shows how it works. I look forward to your questions and comments.</comment>


Ask HN: Books/podcasts/blogs discussing Microsoft's culture change post Nadella? - <AUTHOR> Over the last few years, I'm quite blown away by the sort of change in MSFT's culture. While Satya Nadella wouldn't be the only factor, it has been under his leadership, but I cannot find insightful material on the same. <comment><USER2> Try Stratechery, written from a tech strategy perspective.

[https://stratechery.com/company/microsoft/](https://stratechery.com/company/microsoft/)

This article is a great starting point: [https://stratechery.com/2018/the-end- of-windows/](https://stratechery.com/2018/the-end-of-windows/)

</comment><comment><USER3> A good start would be Hit Refresh [1] written by Satya Nadella.

In this book he explain the issues he found in the company long before he was a CEO (basically, by the time he became the CEO, he knew what was not right).

[1]: [https://www.amazon.com/Hit-Refresh-Rediscover-Microsofts- Eve...](https://www.amazon.com/Hit-Refresh-Rediscover-Microsofts-Everyone- ebook/dp/B01HOT5SQA)</comment>


An Unsolicited Redesign of Time.com - <AUTHOR> http://codybrown.name/2013/03/an-unsolicited-redesign-of-time-com/

<comment><USER2> This is actually brilliant content marketing: clearly define the need (this TIME article misses a great opportunity) and then the solution (our app fixes this).

</comment><comment><USER3> impressive</comment>


Kakapo recovery technology - <AUTHOR> https://www.doc.govt.nz/our-work/kakapo-recovery/what-we-do/technology/ <comment><USER2> Doesn't mention the special kakapo mating-hat then?

For those not informed about this, there was an episode of the series "Last Chance to See" featuring the Kakapo. During the episode one of the few remaining males mounted and tried to mate with the head of one of the presenters.

An 'insider' told me a while later that the individual kakapo did this a lot, to the extent that in an effort to capture genetic material and possibly perform artificial insemination, they created a special hat with a lot of little plastic pouches that an unfortunate volunteer could wear ...

<comment><USER3> That hat never worked apparently, and is now in a museum. [https://twitter.com/jpdanner/status/1045843778722967552?s=21](https://twitter.com/jpdanner/status/1045843778722967552?s=21)

<comment><USER2> Ha!

Thanks, I heard about it from someone that worked there, never saw a picture though!

</comment></comment></comment><comment><USER4> For context:

 _The kakapo, also called owl parrot, is a species of large, flightless, nocturnal, ground-dwelling parrot of the super-family Strigopoidea, endemic to New Zealand.

...

The kakapo is critically endangered; the total known adult population is 213 living individuals, all of which are named and tagged, confined to four small islands off the coast of New Zealand that have been cleared of predators._

[https://en.wikipedia.org/wiki/Kakapo](https://en.wikipedia.org/wiki/Kakapo)

</comment><comment><USER5> The Kākāpō Files podcast ran during the breeding season this year and gives lots of details about the Kākāpō breeding and conservation efforts.

[https://www.rnz.co.nz/programmes/kakapo- files](https://www.rnz.co.nz/programmes/kakapo-files)

</comment><comment><USER3> I love kākāpō so much. They had a record breaking breeding season last year and it was an absolute joy to watch it play out in real-time on Twitter.

Follow [https://twitter.com/takapodigs](https://twitter.com/takapodigs) there - he works directly in their conservation and tweets a lot of photos.

</comment><comment><USER6> Ah yes, the Party Parrot!

</comment><comment><USER7> Perhaps the title should be the subtitle: " _We develop and use new technology to manage kākāpō._ "

Or the subsubtitle: " _Smart devices save time in the field and allow us to do more for kākāpō than ever before._ "

In case you are wondering how a kākāpō looks [https://en.wikipedia.org/wiki/Kakapo](https://en.wikipedia.org/wiki/Kakapo)</comment>


The Feeling of Power - <AUTHOR> http://downlode.org/Etext/power.html

<comment><USER2> A fine story. I've read it before, but it was good to read it again. If I were a school maths teacher, I'd love to give it to a class for a discussion.

</comment><comment><USER3> Thanks for sharing that story. I read a lot of stories from Asimov before, but I didn't know that one. What I don't get, though, is that the people in the future see a benefit in having humans doing the computations that are made by the computers. It sure makes sens for the humans to gain as much understanding as they can of the computers, but multiplications are much faster done by computers. I am missing something here?

<comment><USER4> I think it's not just about time. Computers are way faster than humans for multiplications and elementary arithmetic, but it doesn't "think". Computers are just doing some calculus, with less information on their environment than we get with our human brain. Computed missile guidance will in most cases fail if its target fires the right countermeasure, when a human guiding the missile would more likely avoid it and reach the goal.

Also, I do think that basic understanding of mathematics seriously enhances human intuition, which then helps develop better strategy.

<comment><USER3> For the problem you describe - computer missile guidance - I could imagine a program that analyzes when the missile reaches its target and when it doesn't as a function of some external parameters (weather, temperature, obstacles, etc.). It could detect when the target fires a counter measure (e.g a counter missile) and act accordingly: by doing some tweaks on the missile trajectory and the number of missiles fired at the same time, an ML algorithm could learn how to avoid various counter measures...

So, while it would obviously benefit to have some human brains overseeing the process, such a program could run almost autonomously most of the time. So we let the computer do the "ground work" while we focus on "high level tasks". Today the ground work is the basic calculations, tomorrow it will be part of what is done by humans today, such as adapting the trajectory of a missile as I just described above, the point is that the computing power should allow humans to focus on higher level tasks.

So I don't see how the backward movement described by Asimov can help with anything. Did he just want to warn the mankind against forgetting how calculation works?

<comment><USER4> While I agree that a program could be made to build sort of counter- countermeasure, I think that we are still not conscious of all the information we get from our environment thanks to our brain. And as we don't have this knowledge, we can't give it to our products, like this program.

Now, let's say that we have such a program, able to reach its target most of the time. In that case, people would still have to focus on higher level tasks as you said, like global offensive strategy. Even for this task, I think that a spirit forged with mathematics will certainly be more efficient, with better logics and intuition. But my opinion might be influenced by the fact that in France, our best military schools do have high maths expectations for the entry exam.

<comment><USER3> Well, the example of AI applied to ballistic is a bit particular as the environment - the place you are trying to bomb - will adapt to what you are doing, and thus some human intervention will always be needed, but for a more standard problem where the environment is not adaptive, say, the exploration of an unknown region, I guess an AI could be left all by itself to do some specific tasks. I think it's more relevant in the context of space exploration where sending humans is both more expensive and very risky (note: I have no idea if Curiosity is controlled by an AI or not).

Off topic: I'm French as well, and yeah, Polytechnique has a high level of expectation in maths.</comment></comment></comment></comment></comment>