Archive for April, 2011

Science is all about replication of results, right?

Friday, April 29th, 2011

Remember that paper published a while ago claiming evidence of precognition? I didn’t say anything about it, because I didn’t have anything much to say. Extraordinary claims require extraordinary evidence, Bayesian priors, and all that. You’ve heard it all before.

Here’s the thing. The right thing to do in this situation, as everyone knows, is for other scientists to try to replicate the result. Well, some did just that, tried to replicate the result, and couldn’t. It’s nice to see the system working, isn’t it? Well, it would be nice, except that the journal that published the original paper rejected their article, because they don’t publish replications of previous work. Ben Goldacre’s got the goods.

This is a structural problem with the way science is funded, disseminated, and rewarded. Even though everyone agrees that replication is essential in situations like these, it’s practically impossible to get a grant to merely replicate previous work, or to publish the results once you’ve done it. I don’t know what to do about that.

By the way, I’ve said this before, but let me say it again. In case you don’t know about Ben Goldacre, the great Guardian science writer and blogger, you should. He’s a national treasure. (Not my nation, unfortunately, but a national treasure nonetheless.)

Safe Zone

Tuesday, April 19th, 2011

A couple of weeks ago, I finally got around to participating in one of the workshops for the University of Richmond’s Safe Zone program. For those who don’t know,

Safe Zone educates members of the University community about lesbian, gay, bisexual, and transgender (LGBT) issues to create a network of allies who, together with members of the LGBT community, work to create a community of safety and full inclusion for all its members.

I am now entitled to (and do!) display a sticker on my office door, letting people know that I’m “supportive and affirming of the LGBT community.” I urge UR faculty, staff, and students to do the same. Hard data are hard to come by, of course, but based on anecdotal information that seems credible to me, UR’s campus culture is not as comfortable a place for LGBT students as it could and should be. This is a little thing that each of us can do to show where we stand.

But I have to say that there’s one thing about this program that doesn’t feel quite right to me: the name “Safe Zone.” To be specific, the word “safe” seems to me to set the bar far too low.

It was clear from the workshop that the goal is to be active and committed advocates, whereas to me the word “safe” suggests merely promising to be harmless.

I don’t think this is a minor semantic quibble. I first encountered the term “Safe Zone” a number of years ago, when I was visiting another university and saw a few stickers on people’s office doors. My immediate conclusion was that that university must be a terrible place for the LGBT community, since it appeared that well over 90% of the offices on campus were “unsafe” for them.

I don’t think that the University of Richmond should be, inadvertently or otherwise, conveying a message that only a few places on campus are “safe” for LGBT community members. For one thing, I fervently hope and believe that that message is inaccurate. I know that there is a range of beliefs and attitudes about sexuality and gender issues, but at least in the parts of campus I know about (faculty and administrative offices, primarily), I think that a commitment to support of LGBT people is by far the norm.

More importantly, we should make clear that “safety” (at the very least!) for LGBT people is expected of all community members. Any faculty or staff member who makes LGBT students feel unsafe is guilty of professional misconduct. Walking around campus and seeing that a small fraction of offices are “safe” conveys precisely the opposite message, namely that we as an institution find “unsafeness” to be an acceptable and even normal state of affairs.

I’d like to suggest a simple name change. Those who have made the Safe Zone pledge should be called something affirmative, such as “allies” or some similar term. That seems to me to be better in every way: it’s more accurate, it conveys a more positive and supportive message, and it avoids the pitfall of defining “unsafeness” as the norm.

Just to make 100% sure there’s no confusion about this, let me repeat that I strongly support the Safe Zone program.  I think it’s a great thing to do, and if you’re a colleague or student of mine, I urge you to take part! I just think that a simple name change would make the program stronger.

Particle and wave?

Wednesday, April 13th, 2011

My friend Allen Downey (whose blog, Probably Overthinking It, has a bunch of good stuff on how to think about statistics and data) sent me a mini-rant a while back about the way people often write and talk about quantum physics. He asked me what I thought and suggested it’d be a good topic to write about here. I agree that it’s a good topic. I’ll give a bit of introduction, and then just quote Allen (with his permission).

The topic is the grandiose way in which people often play up the mysteriousness of quantum physics. For about as long as there’s been quantum physics, people have been saying pseudo-profound things about What It All Means. I tend to agree with Allen that the more woo-woo descriptions are annoying at best and misleading at worst. (I’ve grumbled about some before.)

Allen specifically refers to this quote from David Brooks:

A few of the physicists mention the concept of duality, the idea that it is possible to describe the same phenomenon truthfully from two different perspectives. The most famous duality in physics is the wave-particle duality. This one states that matter has both wave-like and particle-like properties. Stephon Alexander of Haverford says that these sorts of dualities are more common than you think, beyond, say the world of quantum physics.

Brooks is writing about the answers to the Edge’s 2011 Question, “What scientific concept would improve everybody’s cognitive toolkit?”  (This is not The Edge from U2; it’s the website edge.org, which annually asks a broad question like this to a bunch of scientists.)

With that context, here’s Allen:

Physicists who wax philosophic about wave-particle duality are a pet peeve of mine, especially when they say nonsensical things like “light is both a particle and a wave,” as if that were (a) true, (b) a useful way to describe the situation, and (c) somehow profound, mystical and inspiring.  But none of those are true.

It seems to me to be (a) clearer, (b) not profound, and (c) true to say instead that light is neither a (classical) particle nor a wave.  It’s something else.  If you model it as a particle, you will get things approximately right in some circumstances, and completely wrong in others.  If you model it as a wave, same thing, different circumstances.  And if you model it as (modern) particle, you get good answers in almost all circumstances, but it seems likely that we will find circumstances where that model fails too (if we haven’t already).

So none of that is an example of “describ[ing] the same phenomenon truthfully from two different perspectives.”  It’s just plain old model selection.

This is quite right. An electron is not a particle (as that term is generally understood), nor is it a wave. It’s an excitation of a quantum field. Practically nobody has much intuition for what “an excitation of a quantum field” means, so it’s useful to have alternative descriptions that are more intuitive, albeit imperfect. Sometimes an excitation of a quantum field behaves like a particle, and sometimes it behaves like a wave.

By the way, when I say it’s useful to have such descriptions, I don’t just mean when talking to laypeople — although that’s part of what I mean. Actual physicists use these description in our own minds all the time. That’s perfectly fine, as long as we know the limits of how far we can push them.

But to go from “electrons sometimes behave like particles, and sometimes like waves” to “an electron is both a particle and a wave” is to mistake the maps for the territory. Here’s an analogy. Sometimes we model the economy as a machine (“economic engines”, “driving the economy”, “tinkering”). Sometimes we model it as a living thing (“green shoots”). But nobody makes the mistake of thinking that the economy is some kind of cyborg.

Stephon Alexander, the physicist Brooks refers to, isn’t particularly guilty of this sin. He actually does a pretty good job explaining what he means by duality in his answer (scroll down on that page to get to him):

In physics one of the most beautiful yet underappreciated ideas is that of duality. A duality allows us to describe a physical phenomenon from two different perspectives; often a flash of creative insight is needed to find both. However the power of the duality goes beyond the apparent redundancy of description. After all, why do I need more than one way to describe the same thing? There are examples in physics where either description of the phenomena fails to capture its entirety. Properties of the system ‘beyond’ the individual descriptions ‘emerge’ …

Most of us know about the famous wave-particle duality in quantum mechanics, which allowes the photon (and the electron) to attain their magical properties to explain all of the wonders of atomic physics and chemical bonding. The duality states that matter (such as the electron) has both wave-like and particle like properties depending on the context. What’s weird is how quantum mechanics manifests the wave-particle duality. According to the traditional Copenhagen interpretation, the wave is a travelling oscillation of possibility that the electron can be realized omewhere as a particle.

There’s one major sin in this description: the word “magical.” Other than that, his description of what wave-particle duality actually means is just fine. One of the other respondents, Amanda Gefter, also writes about duality. She starts out OK, but then uses the notion as an egregiously silly metaphor for people disagreeing with each other. (Sadly, you can’t expect much from someone who works for New Scientist, which was once a good pop-science magazine but isn’t anymore.)