How Good is Your Theory? Open Thread I

He was a dreamer, a thinker, a speculative philosopher… or, as his wife would have it, an idiot. –Douglas Adams

When I started writing about science online in January of 2008, I put the word out that I would accept questions from my readers. After all, I knew that there was a lot of misinformation out there, as well as the more insidious “technically correct but misleading” information about science.

In particular, I want to get the actual information that we know out there. As far as what I can contribute, I’m confident that I can add an expert voice for my specialties (physics, astronomy, and cosmology). What started as a manageable two or three messages a week has escalated into…

Well, let’s just say I’ve learned that many of you are really interested in this stuff, which is awesome. And most of the messages I get ask me to take a look at a new idea, paper, or article, and to evaluate how good it is. This is a great idea, and I’d like to do this, and I’d like to give many of you the opportunity to weigh in.

So we’re going to try something new here: an open thread. There are lots of ideas, papers, and news reports out there, and nearly all of them are reported as the next big breakthrough. Are they really? I’m going to choose a convenient way to rank the scientific ideas that we encounter.

What do I mean by each of these four categories? Let’s go through them one-by-one:

  1. Scientific Law: This is really an elite category, reserved for the most thoroughly tested, rock-solid theories and ideas that we have. These are theories that have stood the test of time, as well, making many new predictions that have all been confirmed experimentally and observationally, where there’s practically no room for dispute other than making extensions or variations to the law itself.
  2. Validated: This is for theories and ideas that do have lots of supporting evidence, but aren’t as solid as scientific law. Perhaps they’re lacking confirmation of a crucial part or two, or perhaps their predictions are too uncertain, or perhaps they simply haven’t been tested well-enough to be sure. We believe the observations and evidence, but the explanation, although valid, isn’t necessarily the only (or best) possible explanation.
  3. Speculative: This is, by far, the most common type of theoretical idea that gets reported. Sometimes it’s testable, in which case it can either be validated or ruled out. Other times, it’s not testable at all, meaning that it’ll remain speculative until it can be tested, if that ever happens. There are many differences of opinion over which speculative ideas are compelling and which ones are rubbish, but I greatly prefer the ones that can be tested, in principle and in practice. (See the Douglas Adams quote at the top.)
  4. Ruled Out: This is the counterpart of the left-side of the spectrum. To test a speculative theory and come up with an observation or result contrary to your theory’s prediction helps put you in this category. A ruled out idea can always be modified and revived, which should knock it back toward the speculative category, where it can hopefully be tested.

You’ll notice that this isn’t a strict categorization; rather, this is a spectrum. So let’s take a look at our first piece (which at least four of you have written to me about), the idea that dark matter may be accumulating in the Sun, and altering the way the Sun emits heat.

You can go read the Wired link above for the optimist’s take on it, but I know too much to fall for it. This is a speculative idea at best. First off, the thing they’re trying to explain — the problem of heat transfer in the Sun — is a very difficult problem to tackle. The “known physics” does a very adequate job of explaining what we observe, and the difference between what the theory predicts and what we observe is smaller than the uncertainty in the theory!

In other words, there’s no motivation for this exotic explanation. But second off — and this is even worse — the type of dark matter that is required to cause this effect in the Sun is almost completely ruled out! If dark matter were as light as the authors contend, we’d expect to find evidence for it from electron-positron colliders.

And since we don’t find that evidence, it means the interactions are weak. How weak? So weak that there’s only a small range left where they can affect heat transfer in the Sun without conflicting with the data from colliders.

So where would I put this idea on our spectrum? I’d place it to the right of speculative, because it’s almost ruled out at this point. Here’s a graph with my placement of some other theories as well.

If and when we can directly detect the particle behind dark matter, I’ll promote it to Scientific Law. If we can narrow down inflation to being a particular model or due to a particular mechanism, I’ll push it over the line, away from Speculative, past Validated and towards Scientific Law. And until we find a reasonable way to test against it, extra dimensions are going to remain stuck in the Speculative category. (And for those of you wondering, Erik Verlinde’s theory is stuck in the speculative category, too, at least for right now.)

So, here’s your big chance. What ideas, theories, reports, or stories are out there that you want more information about? What craziness have you heard that you need a more solid take on? Or, what good, valid science is out there that people still don’t believe? Let’s hear from you!