Heisenberg joke and why water is wet

I love hydrogen in large part because it is a quantum fluid. To explain what that means and how that leads to water being wet, let me begin with an old quantum physics joke.

Werner Heisenberg is speeding down a highway in his car when he’s stopped by a police officer. “Do you know how fast you were going?” asks the officer. “No idea” answers Heisenberg, “but I know exactly where I am.”

The joke relates to a phenomenon of quantum physics that states that the more precisely you can know the location of something, the less precisely you can infer the speed. Thus, the fact that Heisenberg knew precisely where he was implied that he could have no idea of the car’s speed. Of course, this uncertainty is mostly seen with small things like light and electrons –and a bit with hydrogen, but hardly at all with a car or with Dr. Heisenberg himself (and that’s why it’s funny).

This funky property is related to something you may have wondered about: why is water wet? That is, why does water cling to your hands or clothes while liquid teflon repels. Even further, you may have wondered why water is a liquid at normal conditions when H2S is a gas; H2S is a heavier analog, so if one of the two were a liquid, you’d think it was H2S.

Both phenomena are understood through hydrogen behaving as the quantum car above. Oxygen atoms are pretty small, and hydrogen atoms are light enough to start behaving in a quantum way. When a hydrogen atom attaches to an oxygen atom to form part of a water molecule, its location becomes fixed rather precisely. As a result, the hydrogen atom gains velocity (the hydrogen isn’t going anywhere with this velocity, and it’s sometimes called zero-point energy), but because of this velocity or energy, its bond to the oxygen becomes looser than it would be if you had heavier hydrogen. When the oxygen of another water molecule or of a cotton cellulose molecule comes close, the hydrogen starts to hop back and forth between the two oxygen atoms. This reduces the velocity of the hydrogen atom, and stabilizes the assemblage. There is now less kinetic energy (or zero-point energy) in the system, and this stability is seen as a bond that is caused not by electron sharing but by hydrogen sharing. We call the reasonably stable bond between molecules that share a hydrogen atom this way a “hydrogen bond.” (now you know).

The hydrogen bond is why water is a liquid and is the reason water is wet. The hydrogen atom jumping between water molecules stabilizes the liquid water more than it would stabilize liquid H2S. Since sulfur atoms are bigger than oxygen atoms, the advantage of hydrogen jumping is smaller. As a result, the heat of vaporization of water is higher than that of H2S, and water is a liquid at normal conditions while H2S is a gas.

Water sticks to cotton or your skin the same way, hydrogen atoms skip between the oxygen of water molecules and of these surfaces creating a bond. It is said to whet these surfaces, and the result is that water is found to be wet. Liquid teflon does not have hydrogen atoms that can jump so there is no band that could be made from that direction (there are some hydrogen atoms on the cotton that can jump to the teflon, but there is no advantage to bonding of this sort as there are only a few hydrogen atoms, and these already jump to other oxygens in the cotton. Thus, to jump to the teflon would mean breaking a bond with other oxygen atoms in the cotton — there would be no energy advantage. This then is just one of the reasons I love hydrogen: it’s a quantum-y material.

16 thoughts on “Heisenberg joke and why water is wet

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  2. Bret

    One of best explanations on hydrogen bonding I have read in a while. This image of hydrogen sharing will be helpful to anyone trying to understand things like: why DNA stays zipped, why RNA degrades quickly, how sunlight is harnessed by plants. Pretty much all biology comes down to hydrogen bonds.

    Reply
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  4. James

    The fact that you would take a bit of time or a lot and write a article about why water is wet just is ridiculous I think you should focus on better things in life than a simple joke. So, you need to take a break and relax if not there will be consequences I’ll give examples. Staying up at night to try and debunk jokes that don’t need to be debunked or even blanking out when in a conversation and the fist thing that comes to your mind is science jokes that you think need to be debunked. The joke is meant for people to wonder not look it up to find how it works so they can answer correct which can still happen. Just don’t get too carried away or people won’t like the joke any more.

    Reply
    1. R.E. Buxbaum Post author

      I find the quantum nature of hydrogen, and “why water is wet” as very interesting issues. They are related to the structure of life. It’s because to this that I ended up as an expert on hydrogen (some aspects) and water (some aspects).

      Reply
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  11. Ellen Dornan

    I heard Schrodinger was in the car also. The cop got so mad at Heisenberg’s wise-cracking that he made them both get out of the car while he searched it. When the officer popped the trunk, he asked, “Did you know there’s a dead cat in here?” to which Schrodinger replied, “I do now.”

    Reply
    1. R.E. Buxbaum Post author

      Thanks for commenting, Ellen. It’s definitely the second part of the joke. The reason I didn’t cite it is because I wasn’t sure people understood even the first half. Also, I think it’s sort-of-cute to explain science jokes in horrible detail. Is funny because ….

      Perhaps I’ll go into that part of the joke to show how this aspect of quantum mechanics allows you to make one of the coolest science fair projects ever: a small time machine. It turns out the cost of time machines goes up drastically as the size goes up. Not only thanks for commenting; thanks for reading!

      Reply
      1. Ellen Dornan

        Science jokes are the refuge of people like me who are intimidated by the consequences of what quantum mechanics really mean. Your discussion of why water is wet is mind-boggling and not funny; more like that awful feeling that if you think too hard about the world around you, you realize you don’t understand anything at all.

        Reply

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