13 Nov 2017

This Is What It Looks Like When Scientists Don’t Understand Something

Economics, Physics 19 Comments

Tyler Cowen linked to this Nature article, which I find unintentionally hilarious. The first sentence alone is magnificent: “Physicists are growing ever more frustrated in their hunt for dark matter — the massive but hard-to-detect substance that is thought to comprise 85% of the material Universe.”

I beseech you, please do not lecture me in the comments about how much more physicists know about cosmology than economists know about economic growth. I am not disputing that. (Here’s an earlier post I did on this stuff.) You would be hard-pressed to find someone on social media who mocks economists more than me. (Latest example: For a long time I didn’t know exactly what “total factor productivity” was supposed to be, but now I realize it means, “The portion of output that economists can’t explain.”)

19 Responses to “This Is What It Looks Like When Scientists Don’t Understand Something”

  1. Richie says:

    Dirt covers 85 percent of my floor; but when I sweep it, there’s nothing there.

  2. Stephen Dedalus says:

    Perhaps 85% of the material universe is actually composed of the ignorance of physicists?

  3. Tel says:

    I’m going to agree with you 100% on this one Bob… the whole search for dark matter is a waste of time and money.

    However, there have been cases in the past where scientists have found something “missing” and searched hard then finally filled in the gap. For example, the Periodic Table of Elements had gaps in it for many years while they got chased up, and one by one new elements were discovered. Pluto was discovered because Neptune’s orbit didn’t calculate out properly. I vaguely remember the neutrino got discovered when some mass equation didn’t quite balance out (don’t quote me on details, I’m too lazy to look it up). Read “The Cuckoo’s Egg” where the sysop discovers that his program for calculating computer time usage never got exactly the right answer (an excellent detective story).

    They are following a methodology that has worked before… but you can kind of see it isn’t going to work this time.

    Enter the electric universe: how big are the background electric and magnetic fields, how much do they weigh, and could they influence the expansion of galaxies, etc?

    Take two permanent horseshoe magnets that are stuck together. The fields are strong because the two magnets reinforce each other. Pull the magnets apart and it requires force to achieve that… energy is force times distance so by pulling them apart you have added energy to the system. The field is now weaker (it stretches and spreads out) but takes up a larger volume. As you pull them further apart the field continues to get weaker but only to a certain point, and the force gets very low so no additional energy is required to keep pulling them apart.

    So what happened to the energy you put into the system? Where has it gone? Energy has mass, so where did the mass go? Weird.

    Same thing works with an electric field if you start out with a positively charged object stuck to a negatively charged object and slowly pull them apart (also stretches out the field, and requires force to pull them apart). Field between the two objects gets weaker, but the energy needs to go somewhere.

    • guest says:

      “They are following a methodology that has worked before… but you can kind of see it isn’t going to work this time.”

      Remind me to quote this back to you the next time we talk about “extreme a priorism”.


  4. Harold says:

    This is what it looks like when scientists don’t understand something. They conjecture, construct testable hypotheses based on prior knowledge and then experiment to see if the hypothesis is correct. I don’t see what you find odd about this.

    Is is that the scientists don’t know what such a huge proportion of the universe is? If so, then it is pretty humbling. It shows there is a whole lot more to learn, but I think the days of claiming that physics is solved are behind us. It is fairly staggering that we know as much as we do about things millions of light years away.

    Can you explain what it is about this that you find hilarious?

    • Yancey Ward says:

      There is an assumption being made in that first sentence that is actually unsupported. Let me rewrite it for you:

      “Christians are growing ever more frustrated in their hunt for God — the massive but hard-to-detect force that is thought to have created the Universe.”

      Maybe physicists will find dark matter, but maybe they won’t. In the latter case, it may simply not exist.

      • Matt M says:

        Maybe God is made up of dark matter.

        • Tel says:

          God is highly energetic (therefore very heavy) and at the same time completely invisible. God holds the universe together.

          Seems like the Christians and the cosmologists must be looking for the same thing.

      • Scott H. says:

        So the funny part is that many contributors here don’t understand that the author understands there’s an unsupported assumption in the first sentence?

        • Craw says:

          They are misunderstanding the “thought to comprise” bit. You know and I know that it means conjectured but as yet unproven. The way Uranus was once conjectured, and thought to exist before it was actually directly observed. They think it means “that we knows comprises”.

  5. Harold says:

    Yancey, thank you for pointing out the sub-text. However, the scientists are trying to explain an observation about the behaviour if galaxies. The rotation is so fast that they would fly apart unless something is holding them together. The hypothesis is that this something is matter, since if this matter existed it would explain the observations of the galaxies without requiring anything else to be true – there are no other assumptions. It is dark because we cannot see it. The nature of this dark matter is elusive, and the scientists have not found out what form it takes, if it takes any form at all. But because there is no requirement for other things for which there is no evidence to be true this is a favored hypothesis. Hence the belief that there probably is sme form of dark matter – we have pretty good evidence for it.

    Some have proposed that it is not extra matter but that gravity actually varies. Whilst this would explain the behaviour of the galaxies, it would require many other things to be true for which we currently have no other evidence; many more assumptions if you like. Hence these other hypotheses are less favored and not so actively pursued, although some choose to do so.

    But scientists know that something exists to explain the behaviour of the galaxies, because they observe the galaxies behaving this way. If it is not dark matter, then it is something else.

    • Stephen Dedalus says:

      “But scientists know that something exists to explain the behaviour of the galaxies…”

      How in the world would they “know” this? Perhaps their behavior is simply inexplicable.

      You would have to have already bought into some strong metaphysical assumptions, prior to any empirical evidence, to “know” this.

      • Harold says:

        “How in the world would they “know” this? Perhaps their behavior is simply inexplicable.”

        I did wonder about that phrasing but thought a lengthy disposition on the nature of truth and knowledge was not helpful. However…

        We cannot know anything, except as Descartes famously concluded, that we exist in some form to do thinking. The exact nature of our existence cannot be known with certainty.

        However, we usually talk of knowing things, even though this is technically impossible. We usually say we know the Earth is roughly spherical, although we cannot even know with certainty that the Earth exists at all. It is in this way of meaning that I talk of the scientist knowing that there is some reason for the behavior of the galaxies.

        We can question causality, perhaps things do just happen without a cause. There is certainly some discussion about quantum effects. However, in the macro world, causality has been a pretty good basis for understanding. I think that if your argument is based on abandoning this you are on shaky ground, even if technically possible.

        So what they know is that the observations about the galaxies can be explained by dark matter, but cannot be explained by an absence of dark matter and our current understanding of physics. Dark matter is therefore a strong candidate for being the real explanation. There are others, but these require more assumptions, and are therefore less good options to pursue.

        Perhaps a similar situation was Rutherford’s experiments on the atom. The understanding of the atom at that time was the “plum pudding” model. Helium nuclei fired at thin films should go straight through. He observed some bouncing back. “Aha!” he thought, I have an observation that cannot be explained by current model – I know that some nuclei bounce back, which could not happen if our model of the atom is correct.” He did not go on think “Ah, but how can I know there is a reason for this. Perhaps it is simply inexplicable. I shall go and have another cup of tea.”

        No, he looked for an explanation and found it in the nuclear theory if the atom.

        • Stephen Dedalus says:

          “However, in the macro world, causality has been a pretty good basis for understanding. I think that if your argument is based on abandoning this you are on shaky ground, even if technically possible.”

          You are using a circular argument for relying on induction: people like Hume and Popper showed this is completely groundless.

          Re Rutherford: Yes, I know this IS what scientists assume. I am challenging you to provide some ground for their doing so. (And again, “It worked in the past” is circular without some further premise.)

          • Harold says:

            There are no grounds as far as I am aware. We cannot know that everything will not blink out if existence next second, and we cannot know that we were not brought into existence last second with memories and everything. Gravity may suddenly start repelling. People say science is based on deductive reasoning, but at its heart is inductive reasoning.

            However, we mostly proceed as though the past existed, the future will continue to exist and the world is roughly as we perceive it.

            I am happy to acknowledge this is a working hypothesis. It is essential for us to make our way in the world, or what appears to be the world.

            If you want to question this working hypothesis then it makes sense to question everything, not just one specific piece of what we call knowledge.

            There are many more directly important consequences that should probably be dealt with first before we get onto behavior of distant galaxies.

          • Harold says:

            I have looked about and I believe the explanation you may be thinking of – correct me if I am wrong.

            Another possible explanation for the galaxies’ appearance is that they are indeed tearing themselves apart but have not yet had time to do so. There is no dark matter, gravity does not vary.

  6. Harold says:

    Perhaps a summary. The scientists are seeking to explain an observation (about galaxies). They spin too fast to be explained by the visible matter within them. This is a fairly specific problem. Can you point out the observation that you think the god-seekers are trying to explain?

  7. Mark says:

    My two favorite ministries that focus on creation are Answers in Genesis and Creation Ministries International. There are scientists at both that argue for and against dark matter, so it’s a very interesting subject. A few examples (and on the CMI stuff, check out the comments at the end of the articles.)




  8. bb. says:

    not unrelated, but some time ago I was surprised to find, that particle physicists apparently have their own version of p-hacking>

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