You don't know ice. Neither do I, apparently | Hacker News Reader

You don't know ice. Neither do I, apparently

en.wikipedia.org

13 pointswetzeljohn11 comments

This article becomes especially interesting if you've read Kurt Vonnegut's Cat's Cradle.

http://en.wikipedia.org/wiki/Cat's_Cradle

http://en.wikipedia.org/wiki/Ice_nine (fictional material within Cat's Cradle)

Another fun ice fact is that hot water freezes faster than cold water: http://math.ucr.edu/home/baez/physics/General/hot_water.html

in some poorly-understood conditions

This factoid gets trotted about without ever noting the (tiny) magnitude of the effect, it just plants a (false) idea in the readers mind that you can get ice faster by microwaving water first.

I remember looking at this ages ago (I browse my share of wikipedia)

trying to work out why you couldn't use ice as a submarine hull. I mean the deeper you go the more freezes on it and the thicker it gets?

inb4 it floats, so does air

There is an extremely tough material made out of frozen water and sawdust called Pykrete: https://en.wikipedia.org/wiki/Pykrete

There were some plans to make ships out of it and it seems that mythbusters did an episode on it which I haven't seen: https://en.wikipedia.org/wiki/MythBusters_(2009_season)#Epis...

It's possibly that episode that triggered the submarine thought!

Ah, I didn't notice at first that information about the original Project Habakkuk is linked to higher up in the Ice article: http://en.wikipedia.org/wiki/Project_Habbakuk

Thinking about it now, I wonder if a better form of pykrete could be made with a more modern expanding/insulating material than wood pulp…

> I mean the deeper you go the more freezes on it and the thicker it gets?

As the article makes a point of mentioning, unlike nearly all materials, added pressure is more likely to melt ice than cause it to freeze, at least at the pressures and temperatures we're considering.

The pressure of water at 10000m (basically the deepest the oceans go) is ~100 MPa. Look at the liquid part of the phase diagram between 100 kPa and 100 MPa. See how it abnormally extends left as pressure increases to ~200 MPa?

No, I see that I mean if you have a cooling system of some kind you should see layers like in hail where more and more water freezes around it?

The only problem with that is you can't think of cold as something you can generate. Cold is the absence of heat, and so the only way to make it in a place where there is already heat is to move the heat somewhere else.

If you keep it inside the vessel, then you're faced with containing a zone of steadily increasing heat (and thus steadily decreasing efficiency of your heat pump). If you try to dissipate it outside of the vessel, you run into further engineering problems (the heat conduit has to pass through the hull at some point, which creates a weak spot for pressure and a potential heat leak to the rest of your hull).

Mods, please fix title.

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