Locklin on science

30 open questions in physics and astronomy

Posted in Open problems, physics, physics anomalies by Scott Locklin on August 2, 2012

A friend of mine asked me if I thought there were actual open questions in physics, ones that individuals or small groups could make a contribution to (as opposed to things like the Higgs boson which require 4000 people and billions of dollars to suss out). Here is a list I came up with. I don’t think it is definitive, and for all I know, some of these problems may no longer be open questions as of today, but I didn’t find anything better on the internets. It may be of interest to young researchers wishing to make a real contribution to human knowledge. Or maybe it’s just something to bullshit about.

Unlike other such lists, there are no silly cosmological or quantum gravitic types of questions on it. I think these are unanswerable questions, and not presently solvable by Baconian science. Essentially, such questions are metaphysical. They can’t presently be solved even in concept by making observations about reality. We’d still like to know the answers to such questions as how to unify gravity with the other forces, but it’s effectively a sort of mathematical philosophic enquiry, rather than normative science.

The other aspect of my “open questions” is they could conceivably be solved by an individual or a small team. I had to use my judgement on that, such as it is. I think these are all interesting and worthy mysteries; ones which could be of great import to the human race. I suppose they vary quite a bit in importance, but all of ’em are interesting.

  1. High Tc superconductors: they cost nothing, and liquid nitrogen is cheap. Nobody knows how they work, or if they could make one at room temperature. The consequences would be tremendous if we could! IMO, every barnyard physicist who is worth two shits should have some perskovites and liquid nitrogen kicking around the lab, just for fiddlin’ with.
  2. Turbulence and Navier-stokes is still little understood: this is pencil and paper physics which stumped Heisenberg. If you think liquids are important, this is huge.
  3. Why is life chiral? When you make amino acids using chemistry, it isn’t chiral. How come life is chiral?
  4. Quantum mechanics is still mysterious, particularly in the classical limit: pencil and paper contributions and relatively cheap (though carefully done) experiments are possible. This is one of the biggest open questions for it’s philosophical and technological (quantum computing?) implications.
  5. Cosmic ray physics still has plenty of unusual phenomena. Detectors are cheap. You do have to wait for things to happen. What’s up with the giant cosmic rays for example?
  6. Solid to glass phase transitions are poorly understood and very interesting.
  7.   Fractional quantum Hall effect: simple and cheap experiments, and pencil and paper theory which could help us understand lots of other things in nature.
  8.   Catalysis is fairly mysterious and potentially revolutionary for novel technologies. The models I have seen are pretty hand-wavey, and not very useful for inventing new catalysts or predicting the properties of old ones.
  9.  Entropy and the arrow of time; this is at least as important as Ernst Mach’s philosophical ideas on relativistic things, which eventually helped lead to relativistic physics. Pencil and paper and thought experiments will suffice here. This is a very important philosophical question. Probably more important than understanding quantum mechanics.
  10.   What is life? Nobody knows.
  11.   How do brains work?
  12.   Properties of metallic hydrogen -I think you can do these experiments in diamond anvils. Or you could send a lab to Jupiter.
  13.   Is there a physics analogue for solving NP-hard problems? OK, this is cheating and stealing from computer science, but there may be physical algorithms you could use as proofs here, just like certain spectra could theoretically calculate Reimann’s Zeta. I’m not the only one to have looked in physical systems for answers here.
  14.   Is there a knowable physics of granular materials? How do singing sands work?
  15.   How does non-equilibrium thermodynamics work? We know there is order here; you can see the order with your eyes, but we don’t know what the rules are. This is potentially bigger than understanding quantum mechanics.
  16.   Are there more new weird properties of matter? We keep discovering poorly understood stuff like high Tc superconductors and the fractional quantum Hall effect. Material science is vast and potentially technologically revolutionary.
  17.   How does water work? The large heat capacity of water is an enormous physical mystery. Water should be vapor at STP. It ain’t.  People wave their hands and talk about hydrogen bonding, but hand waving doesn’t do much. This is also potentially huge. It’s freaking water: doesn’t get much cheaper than a jar of water.
  18.   WTF is going on inside the earth? Whence comes the magnetic field? Why doesn’t Venus have one? Why is it so damn hot in there? Yes, I know there are theories: they don’t even pass a sniff test.
  19.   What is the story with the Pioneer anomaly? If it’s accurate and not from something silly like an outgassing thumb print, this could throw everything we know about physics and astronomy into utter chaos. There is a way of answering this which would cost a half billion or so; shoot something into interstellar space on purpose and see what happens in 20-40 years. This is arguably far more important than anything in particle physics. The “flyby anomalies” turned out to be dipshits not understanding special relativity… I’m assuming that dipshits have done enough special relativity on Pioneer to rule this out. Otherwise: undergraduates: get to work! Edit add: I thought the flyby anomaly was resolved with SR, but googling further; it ain’t!
  20. The atmosphere is filled with anomalies: ball lightning, sprites, ELVES, blue jets, TIGERs, green flashes & etc. I have a fat book by William Corliss catalogueing mysteries from the 60s; there are even more now.
  21. There was a gamma ray burst where the high energy gamma rays got here before the low energy ones. Looks like highly anomalous physics.
  22. GEO600 has produced some bizarro gravity results.
  23. Corona physics makes no sense. Why is the corona hotter than the sun’s surface?
  24. What are diffuse interstellar bands? Nobody has a clue as to what is absorbing light at those wavelengths, yet … I’m supposed to believe the standard model explains everything? Chyeah, right.
  25. Is dark matter real, or is it the same thing that makes orbital mechanics fuck up? Something is weirding up the rotations of galaxies. I’m very tempted to put this in with the Pioneer anomaly and say, “gravity is largely untested using experiments; we should change this.”
  26. Horizon problem;  why does the universe look homogeneous? It shouldn’t be.
  27. For that matter, why is cosmic microwave background anisotropic, when everything else is isotropic?
  28. What are magnetars?
  29. Long delayed echos? This is a seemingly science fictional level of WTF. I recall some science fiction type speculated this was a sign of alien intelligence in the Solar System.
  30. Why is there more matter than antimatter? I threw that one in for high energy types. You already have a result: if you’re so smart -figure it out.

26 Responses

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  1. Rod Carvalho said, on August 2, 2012 at 9:30 am

    > How do singing sands work?

    Looks like a group at Caltech solved that mystery: Solving the mystery of booming sand dunes (2007). Here is the abstract:

    Desert booming can be heard after a natural slumping event or during a sand avalanche generated by humans sliding down the slip face of a large dune. The sound is remarkable because it is composed of one dominant audible frequency (70 to 105 Hz) plus several higher harmonics. This study challenges earlier reports that the dunes’ frequency is a function of average grain size by demonstrating through extensive field measurements that the booming frequency results from a natural waveguide associated with the dune. The booming frequency is fixed by the depth of the surficial layer of dry loose sand that is sandwiched between two regions of higher compressional body wave velocity. This letter presents measurements of the booming frequencies, compressional wave velocities, depth of surficial layer, along with an analytical prediction of the frequency based on constructive interference of propagating waves generated by avalanching along the dune surface.

  2. sconzey said, on August 2, 2012 at 10:22 am

    It would be awesome if you could expand a little more on some of these, for instance, what is the problem with the hydrogen-bond explanation of the high specific heat capacity of water? It’s taught in British A-level chemistry classrooms so I kind of assumed it was a solved problem.

    • Scott Locklin said, on August 2, 2012 at 8:33 pm

      Everything is a solved problem to chemists! They claim to understand catalysts as well, but can’t make me a new one.

      • sconzey said, on August 3, 2012 at 9:03 am

        So is it that the enthalpy of the bond implied by the enthalpy of vapourisation is a lot greater than hydrogen bonds in other liquids?

        • Scott Locklin said, on August 3, 2012 at 11:59 pm

          Starting from purely statistical mechanical considerations, nobody understands the ordering principle which makes the specific heat of water as high as it is. Yeah, it’s almost certainly “hydrogen bonds” … but why doesn’t it behave more like other hydrogenic liquids?
          The chemistry way of understanding is to measure things and talk about enthalpies and such. The physics way is to measure things and wonder why the heat capacity is so damn high.

  3. Harlan Harris (@HarlanH) said, on August 2, 2012 at 1:13 pm

    “How do brains work”? Really? This is why people in other fields of the sciences scoff at mathematicians and physicists when they try to dabble in other fields. They say something pointless like “How does matter work?”. No individual or even small group is going to make revolutionary progress on brain function any more. The most fundamental open questions are in how transient things like perceptions are represented in firing patterns of cortical neurons, how the brain represents itself (aka, consciousness), and whether there’s a qualitative difference between human and non-human cognition and what that might be. None of those are at a level of representation that physicists bring any special insight or expertise to. (Neuroscientists are well aware of and make excellent use of dynamical systems theory, which did come from physics. But the idea that things like quantum effects have any real effect on brain function, for example, is ludicrous.) Please, make sense of water (#17) instead.

    • Scott Locklin said, on August 2, 2012 at 8:37 pm

      The idea that quantum effects or gravity has something to do with brains is kind of ludicrous. On the other hand, the idea that neuroscientists know much about how brains work is also kind of ludicrous. If they had any real insights, they’d be used in signal processing applications at the very least. The last time that happened, I think, was Hopfield (a physicist, FWIIW) who seems to be wrong, but at least his invention was useful in signal processing.

      • Harlan Harris (@HarlanH) said, on August 3, 2012 at 1:30 am

        No neuroscientist would claim to really deeply understand how the brain works, but they’ve ruled out a whole lot of options, and have some pretty good ideas about some aspects of it. And yes, Hopfield’s work is important in signal processing. But it’s not clear to me that the way a bunch of meat does signal processing would necessarily be relevant to how digital processors do it, as you imply. Certainly things we know the brain does, like signal integration and frequency-domain processing, are much more easily done in entirely different ways on chips. And, for what it’s worth, some important machine learning techniques (SVMs) do come of out artificial neural net research, which was originally inspired by brain architecture. But it’s not really like what brains do, and most modern ANN research is pretty far removed from brain architecture, simply because it’s just not that efficient.

        Thanks for the response!

        • Scott Locklin said, on August 3, 2012 at 1:57 am

          SVMs came from neural nets? That’s news to me. I thought they were more or less autochthonic, like random forests.

          Brains are weird; neuroscience needs all the help it can get.

          Regarding physicist contributions to biology, two words: Walter Gilbert. Two more: Francis Crick.

      • akkartik said, on August 9, 2012 at 4:43 pm

        But why is brain function a question for ‘physics and astronomy’?

        • Scott Locklin said, on August 9, 2012 at 6:32 pm

          Because we think it’s physical, that’s why! We can leave the astronomers out of this one, as with some of them other questions.

  4. Sisyphus said, on August 2, 2012 at 8:20 pm

    It looks like you forgot to mention dark energy. In fact, I have been struggling with the conceptual reasoning behind the need for it.

    Consider: The longer the distance of the observed object from us, the higher the red-shift and the measured resulting speed and acceleration – so far so good. However, the longer the distance, the older the observed object is in time from us, and consequently the closer the instance of observed speed is to the Big Bang – and, conversely, the close to us the object in space, the closer it is also in time and more distant in time from the big bang. It would make sense that objects would move more quickly when closer in time to the explosion that generated them and that they would eventually slow down due to gravity. Ergo, the expansion of the Universe is actually slowing down and not accelerating. Therefore, no need for dark energy and the gravity model works as previously understood.

    I would greatly appreciate your thought on the following thought experiment. Perhaps you can spot a flaw that I fail to see.

    • Scott Locklin said, on August 2, 2012 at 8:39 pm

      I’d feel a lot better about this sort of thing if astronomers could explain ordinary orbital mechanics.

      • Traherne said, on August 2, 2012 at 10:01 pm


        The people who laugh when physists or mathematicians invade their fields are idiots, generally speaking. Physicists routinely add value to other disciples. I don’t know what moron could think otherwise. For example, just look at Freeman Dyson’s latest results for IPD.

        • Harlan Harris (@HarlanH) said, on August 3, 2012 at 1:34 am

          IPD is math. I’m talking primarily about biological sciences. I’m not saying that mathematicians and physicists shouldn’t switch fields and do science. I am saying that they have a history of arrogance and embarrassing misunderstandings, and need to be humble when they do switch fields.

  5. JasonW said, on August 4, 2012 at 7:19 pm

    I thought the Pioneer anomaly was sorted? http://www.space.com/16648-pioneer-anomaly-spacecraft-mystery-solved.html

  6. Crocodile Chuck said, on August 6, 2012 at 9:17 pm

    Another: Is there abiotic oil within the Earth? (Thomas Gold)


  7. wrmckinney said, on December 8, 2012 at 4:41 pm

    A cursory look at the planets allows the conclusion that to have a magnetic field in a terrestrial planet requires heat, and rotation. While hot inside, Venus almost does not rotate. As for the heat of the Earth, 5 billion years is just not enough time for it to have cooled yet from the formation of the solar system.

    • Scott Locklin said, on December 9, 2012 at 4:11 am


  8. Things We Don't Know (@TWeDK) said, on January 21, 2013 at 12:18 pm

    Hi Scott, that’s quite a nice list you’ve got there, but I’m sure you’ll agree it’s just the tip of the iceberg. In fact, we’re setting up a website dedicated to compiling a much more comprehensive list, complete with links to (open source) papers, and interactive tools for scientists and the public. I’d love you chat to you about what we’re doing, if you’re interested. You can find our holding page & blog at http://www.thingswedontknow.com
    If you’d consider adding us to your blogroll, that would be almost as good 😉

  9. pucenoise said, on September 15, 2015 at 10:23 pm

    This seems like an impressive stab at the brain problem, although as a man of limited intellect I can’t decide if it’s typical physicist dreck or not (the author does do actual experiments and theory so I find that promising, people with a sense for experiments seem less likely to get lost in delusional fantasy unicorn theorist lala land):

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