Category Archives: Physics

A Cold (War) Light

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Weapons-Grade Private Enterprise

In 1991, the Cold War ended without making the world immediately safer. The Soviet Union had split up: Russia was dead broke, and much of its nuclear arsenal was split among the newly-independent countries of Belarus, Kazakhstan, and Ukraine, which were also broke. The reasonable fear was that the nuclear stuff and the nuclear scientists would go to the highest bidder. True, countries were negotiating how to get rid of nukes and the stuff of which nukes are made, but international negotiation is slow and international bidding likely to be much faster.

That fall of 1991, Neff wondered whether Russia could un-enrich its weapons-grade uranium, sell it to the U.S., and the U.S. would pay in dollars and use the un-enriched uranium to fuel its civilian nuclear reactors.

Interesting bit of swords-to-ploughshares history.

Getting Ahead of Getting Ahead of Yourself

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When Science Gets Ahead Of Itself

Science certainly can get ahead of itself, but I don’t think the author chose a particularly good example of it. The beginning of this article is mostly fine — the history is laid out, and the whole idea of “science requires confirmation, and Planck didn’t confirm BICEP2, so that’s just too bad” is spot on.

It’s this:

The BICEP2 results were announced in a press conference before they had gone through the referee process. That meant the hard-core examination of the data and their analysis had not yet been subject to a peer review by someone (or a bunch of someones) who was not part of the team. It would have been the referee’s job to be merciless in his or her criticism, catch potential problems and, hopefully, make the paper better. Peer review is an awesome process and it’s one critical reason behind science’s powerful capacity for finding the true voice of the world.

Scientists often complain about how the media blow science stories out of proportion or get the details of those stories wrong. But in this case, by press-releasing their results before this full scientific process was completed, the international media machine was engaged by the scientists themselves.
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And while, of course, everyone was careful to include “if these results are confirmed,” the point is — within weeks — people were already noticing problems with dust and the BICEP2 results related to dust.

I think there’s a fairly significant sin of omission here.

Here’s a hint: all these people who “were already noticing problems with dust and the BICEP2 results related to dust” — where did they get the detailed information required to notice these problems? The press release? No, there was a preprint uploaded to arXiv on the same day the press release was issued.

So what would have been different without the press release? Not a lot, I think. Scientists would have latched on to the results pretty quickly, and there would have been blogging and tweeting and other communication that doesn’t involve the traditional media, who might have taken a tad longer to pick up on the story. From a science perspective, though, the impact is that maybe the science discussion gets started a day later and accelerates a little more slowly. Otherwise, Clarice, the press release is INcidental. I think it only mattered to the mainstream press and scientists outside of the field who were not in a position to add anything to the discussion, and served to reduce confusion and inaccuracy in some articles (a positive, not a negative). Such as [ahem] avoiding saying “gravity waves” instead of “gravitational waves”.

The advent of arXiv is a huge difference between the actions of Pons and Fleischmann of cold-fusion infamy, who also issued a press release before peer-review. The difference is that now there is a preprint server, widely used, where physicists upload papers before peer-review and publication. Making a preprint widely available has become common practice. I can’t believe the objection is to structured discussion or dissemination of work among/between scientists before formal peer review, because that would include not only preprints, but any kind of conference or colloquium presentation that occurred before publication — those are not peer-reviewed either. That would be a rather radical objection, and I don’t think that was the intent — it’s not what I take away from the article.

If there’s a possible criticism here, it’s perhaps that the paper’s authors needed to temper their predictions based on criticism, but I don’t really have the expertise to go through and find and comprehend whatever changes they made between the original submission and the final, published article. (Oh, did I mention that the paper actually made it through peer review? Yes, it was published in June.) So perhaps they did. Whatever objections were present didn’t stop publication, nor is it clear that they should have. In fact, I think it’s likely that the widespread discussion meant that reviewers had access to more objections and discussion that took place in public than if there had been no preprint and press release. Remember, peer review isn’t a guarantee of correctness. It always comes down to verification, and more verification.

As a scientist who spends a lot of time explaining science to the public, I just wish the BICEP2 press-released team had waited. I wish they’d have let the usual scientific process run its course before they made such a grand announcement. If they had, odds are, it would have been clear that no such announcement was warranted — at least not yet — and we’d all be better off.

And I think the process did run its course, quite properly, and eliminating a press release would have changed nothing of importance. I think the author needs to metaphorically pick up the flag here. Incidental contact, no foul.

The Price of a Spherical Cow

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The Value of Idealized Models

I’m going to take some exception to something, again.

Superficially, it might seem like a good thing if our theoretical models can match real-world data. But is it? If I succeed in making a computer spit out accurate numbers from a model that is too complex for my meagre mortal mind to disentangle, can I claim to have learnt anything about the world?

In terms of improving our understanding and ability to develop new ideas and innovations, making a computer produce the same data as an experiment has little value.

I agree with that. You could also take the example that you can model any data set with a polynomial of sufficient order — that would tell you little or nothing about the actual mathematical function in play for your data (think epicycles — arbitrarily good agreement of planet positions, no insight into gravity). But I think the mistake here is extrapolating this class of models — ones that are too complex to comprehend or are otherwise not descriptive of the interactions taking place — and concluding that all precise and accurate models are bad (which is the vibe I’m getting here). It’s not the case — the whole goal of many physicists is to get models that match experiment to the highest degree possible and that we also understand the details. I think the author is cherry-picking the drawbacks of good models to make his point.

If I want to learn how an amoeba (or anything) works, by theoretical modelling, I need to leave things out of the model. Only then will I discover whether those features were important and, if so, for what.

Again, this is true as far as it goes, but only addresses one path to understanding. You can add things on to a simple model, too, or have sufficiently different effects that you know which part is contributing. Again — overselling. There are a lot of models that are built up over time as we get better data; not everyone goes in with all the potential pieces available and have to do such pruning.

Atomic physics has a model of the Hydrogen atom, and there is a basic model that predicts the gross energy-level structure; similar to the Bohr model, but even better because it gets other details correct that the Bohr model lacks. (IOW the Bohr model isn’t better because it’s simple. Simple doesn’t trump being wrong, but that’s not really my point). The simple QM model doesn’t quite work. We can add in corrections to the simple QM model and account for relativistic effect and spin-orbit interactions and this accounts for what we call the fine structure, which shifts the energy states. When we include the detail that the nucleus has a magnetic moment that affects the electrons and bingo, we get the smaller hyperfine splitting. Add some QED into the mix and you explain the Lamb shift which lifts the degeneracy of two of the levels of the first excited state.

There’s also the problem that if your model is too simple for the problem, then you have no idea if the basic idea is right, because none of the data will match up. You have to be able to construct experiments where your model is at least approximately right for reasonable hope in confirming its correctness.

There is incredible value in simple models. But the value doesn’t automatically diminish if you add some well-understood, higher-order corrections.

(The spherical cow joke is in the link. Point-cow joke and cartoon here)

It Shows

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So You’re Not a Physicist …

I’m a tad conflicted here. On the one hand, there’s technical accuracy. On the other, there’s poetic license, and on the third hand there’s “Meh”.

I do think there is a danger in this. People will end up perceive the wrong idea of a physics concept if their exposure is a bad analogy. Take “Quantum Leap” (please!). If your only exposure to the term came in metaphors and analogies in popular works, you’d probably think that “quantum” means “big”, rather than its correct meaning of “discrete”. (That is, not being quantum means being continuous. Not small.) That’s just one more misconception that science teachers and communicators have to tear down before you can get to the juicy science underneath.

Looking at this from another perspective, I think there are a few folks who balk at English in general being applied with imprecision — the ones who point out that rain on your wedding day isn’t ironic, for example. That group counts the New York Times (different columnist, though) among its members.

Accuracy and precision in communication is important. So why give physics metaphors a pass?

Combing the Sky … for a Good Explanation

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Finding Extrasolar Planets with Lasers

This ought to be better, and the fact that it isn’t reflects very poorly on the writer, and on the Planetary Society for not demanding better.

I find this particularly annoying because it has this “all these big words! Optical physics is Hard!” vibe to it. It would be easy enough to do the same thing with the astronomy side, cracking wise about stellar classifications and the like, but they would never consider doing that, because that’s their business. When it comes to physics, though, they have no qualms about dropping into Barbie mode, and I find that really annoying.

The hard is what makes it great.

Anyway, I agree — glossing over some interesting physics because it’s outside your area of expertise is one thing, but passing it off as magical gizmos is just lazy. I am biased, though — I’m an atomic physics guy, I’ver seen talks by both Ron Walsworth and Dave Phillips on the Astro-Comb and it’s pretty cool, and frequency combs are why I am of Nobel blood (via Ted Hänsch).

And even if you don’t want to (or can’t) write up something less awful than this hand-waving, here’s a radical idea: it’s the internet, so link to someone with a better explanation! I know, that’s blasphemy for a commercial publication — thou shalt not link outside your own ecosystem — but this is the Planetary Society (it’s a “dot org” not a “dot com”) so I’d think they’d be more concerned with getting good info out and less about external links at the tail end of an article.

It Don't Mean a Thing …

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King of the swingers: photographer builds giant pendulum to make amazing art

The [2D] swings combine with each other to create swirling designs called Lissajous figures.

The patterns are so stunning that machines like Blackburn’s Y-shaped pendulum were made commercially in the Victorian era. They became known as “harmonographs”, since the variation in images results from the variation in harmonies between the different swings.

MAD is not a Viable Strategy

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How anti-vaccination is like a nuclear bomb

How quickly the disease spreads, if it spreads at all, depends on the number of people vaccinated. Again, we find very simple math: if, on average, an infected person encounters less than one unvaccinated person while he/she is contagious, the disease will die out. If, however, an infected person encounters more than one unvaccinated person while he/she is contagious, the disease will multiply: each new infected person infects new ones.

A fairly decent analogy (even if I have a terminology nit: induced reactions are not decays)

Ready, Set, Go!

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Special relativity aces time trial

The scientists made the moving clock by accelerating lithium ions to one-third the speed of light. Then they measured a set of transitions within the lithium as electrons hopped between various energy levels. The frequency of the transitions served as the ‘ticking’ of the clock. Transitions within lithium ions that were not moving served as the stationary clock.

On the one hand, very cool-sounding experiment. On the other, [yawn], Einstein wins again. Cool experiment wins, though. This blurb makes it sound like maybe they were doing spectroscopy and seeing the shift in the resonance, much like in the Pound-Rebka experiment which confirmed gravitational time dilation. I have to go get the paper at work and read it.