Just about a year ago, a team of scientists reported that Betelgeuse—the bright red star in Orion’s shoulder—appears to have shrunk by about 15% since 1993. That would mean the diameter’s been shrinking at about 1200 miles an hour for all that time.

Such shrinkage—if it’s really happening (it’s hard to be sure)—could be the precursor to a supernova explosion, which would be way cool. The mathematician John Baez computes that a supernova Betelgeuse might be roughly as bright as the full moon, or maybe up to three times as bright.

Surprisingly, it took almost a year for this information to be widely reported on the Internet, but in the past few weeks, a number of sites have cropped up touting the upcoming supernova, and, as you might expect, a few prophecying doom. You can ignore the doomsayers; at a distance of 600 light years, Betelgeuse is too far away to hurt us.

Browsing the various science forums (such as Discover’s), I’m struck by how often the following simple question comes up: Given that Betelgeuse is 600 light years away, is it or is it not true that it would it would take 600 years for us to notice any explosion? Or to put this another way: If the sky lights up with a new moonlike object tomorrow night, does that mean the explosion took place 600 years ago?

A pretty good answer—and the one that’s being given on all those science forums—is “yes”. But that can’t be exactly right, at least not for all of us, because at any given moment some of us are sitting in our living rooms while others are driving on the Interstates. Relativity tells us that if we’re moving relative to each other, then we must disagree about the times of distant events.

How much do we have to disagree? By about a half an hour, if I’ve done my arithmetic right. If you, standing on a street corner, say the explosion took place at noon on June 9th of the year 1410, then the driver of the car who has just run over your toes at 70 miles per hour (heading in the general direction of Betelgeuse) must say the explosion took place at 11:30AM on the same day. A half hour is not a lot (though it’s more than the few fractions of a second most of my friends have guessed), but here at the Big Questions, we aim to be precise in every detail.

Edited to add: It’s clear from the comments that I should have been clearer about what I’m assuming. My assumption (which I’d thought I’d stated but now see that I didn’t) is that you (and your friend) see the explosion at the exact moment when he’s running over your toe. You then each calculate how long ago the explosion must have taken place. Your conclusions will differ by half an hour.

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Medpage Today reports that the revision has already been changed several times in response to these comments. These include several areas within the Sexual and Gender Identities categories, and modifications to the criteria for adjustment disorders and eating disorders.

By contrast, the American Physical Society is not asking the general public to weigh in on the prospects for supersymmetry, nor is the American Economic Association surveying the general public on the properties of dynamic stochastic general equilibria. So much for any pretense that psychiatry is a science.

Hat tip to Tom Amoroso, who called this to my attention though he might not endorse this commentary.

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What are the odds that humankind will survive long enough to colonize the Universe?

Katja Grace argues that the odds are low. Stripped of some nuance, her argument comes down to this:

1. The fact that we’re around suggests that intelligent life is likely to be common.
2. No other intelligent life appears to have colonized the Universe.
3. If they haven’t succeeded, why should we?

By coincidence number one, I discovered Katja’s post (via a ringing endorsement from Robin Hanson) just hours after I’d posted yesterday’s entry here on The Big Questions disputing point 1). Of course, if point 1) fails then so does the entire argument.

So in response to Katja’s and Robin’s posts, I think it’s worth quoting a book review from the astrobiologist Charley Lineweaver, who I also quoted yesterday. Here is Lineweaver commenting on the “convergentist hypothesis”—that is, the hypothesis that evolution tends to converge on something like human intelligence:

[The convergentist hypothesis] is an appealing idea, but it has failed a series of exhaustive tests. It disagrees with the best data we have. A series of long-duration, independent and thorough experiments in evolution were set up and left to run. The most straightforward interpretation of the results is that human-like intelligence is not a convergent feature of evolution. There is no “intelligence niche” toward which animal species have a penchant to approach. In the absence of humans, other species do not converge on human-like intelligence as a generic solution, or even a specific solution to life’s challenges. These tests have been universally ignored.

The names of these tests are South America, Australia, North America, Madagascar, and India…For landlocked species, these continents that drifted independently of each other for between 50 and 200 million years were crucial experiments for evolution.

The time scale for tripling the size of the human brain in Africa was about 2-3 million years, while the time scale of the experiments was 50-200 million years. Thus, the experimenters were conservative and ran the tests 10-100 times longer than was necessary.

…

Five continents and millions of species evolving over tens or hundreds of millions of years are yelling at us upwind against our vanity: “…Human intelligence is not a convergent feature of evolution.” Rather, it is a species-specific trait—like the beautiful yellow crest of a sulfur-crested cockatoo.

Now, by coincidence number two, I happen to have had lunch with Robin Hanson yesterday, and I ran this argument by him. Robin is unimpressed. He doubts that five experiments are enough to tell us very much about what might happen on 10²² planets. In Robin’s words, “all this shows us is that the likelihood of evolving intelligence is less than about one in six”. He’s willing to take those odds.

I am sympathetic to Lineweaver’s view that we should no more expect to find extraterrestrial intelligence than extraterrestrial basketball. I am extremely sympathetic to his view that after six experiments, we essentially know for sure that evolution has no tendency to produce intelligence consistently. But I’m also sympathetic to Robin’s view that in the vastness of the Universe, six experiments can’t tell us much about what we might find. What else am I missing?

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This diagram, lifted from a lively paper by the astrobiologist Charles Lineweaver, is the tree of life on earth. The “root” at the center is the last common ancestor of all life. Toward the bottom left, you’ll find the genus “Homo”, to which you and I belong, at the end of a twig representing animals. The two neighboring twigs, ending in Zea (i.e. corn) and Coprimus, represent plants and fungi, our two closest relatives.

Professor Lineweaver offers this diagram as an antidote to the superstition that evolution has some tendency to converge on intelligence; his criterion is that we ought not say that evolution “converges” toward some feature unless we observe that feature arising independently in at least two or more twigs. By that same criterion, evolution has no tendency even to converge on heads, which (says Dr. Lineweaver) are likely to be prerequisite for anything like human intelligence.

If human-like intelligence is a fluke, then presumably the ability to build radio telescopes is also a fluke, which stands as a cautionary note for those who expect to communicate with extraterrestrial civilizations.

Now it’s certainly true that if you magnify that animal twig to display separate branches for birds, dolphins and carnivores, you can fool yourself into thinking that intelligence has emerged independently along a multitude of pathways. After all, the last common ancestor of birds and men had a very small brain; after 310 million years of independent evolution, birds and men both have much larger brains. The last common ancestor of dolphins and men had a small brain; after 85 million years of independent evolution, both dolphins and men have much larger brains. But Dr. Lineweaver observes that the “independence” is illusory. By the time we and the dolphins went our separate ways, we were already endowed with highly similar biochemical neural pathways and constraints that left us both with (in Dr. Lineweaver’s words) a finite number of highly evolved “toggle switches” that could be successfully tinkered with.

Moreover, even if evolution were biased toward intelligence, there’s no reason to suppose that intelligence would be the sort we can communicate with across interstellar distances:

About 600 million years ago, two kinds of metazoans, protostomes and deuterostomes, diverged from each other. Both evolved independently for ~600 million years and were very successful. Today there are about a million species of protostomes and about 600,000 species of deuterostomes (of which we are one). We consider ourselves to be the smartest deuterostome. The most intelligent protostome is the octopus. After 600 million years of independent evolution and despite their big brains, octopi do not seem to be on the verge of building radio telescopes.

Doctor Lineweaver closes with an endorsement of the Search for ExtraTerrestrial Intelligence, on the grounds that it’s cheap and he might be wrong. Do you agree with him?

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You can watch the video interviews at BigThink, where, as always, I wish they would post transcripts; reading is faster than viewing and skimming is faster still. But if you’ve got the patience, some of these are fun.

What’s your (realistic or fanciful) scenario for the end of days?

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So I was delighted by recent news reports that beautiful women do indeed have more daughters. But I was stunned by the reported magnitude of the effect: According to one report, beautiful people are 36 percent more likely to have a daughter than a son!

If that’s true, it throws a whole new light on certain divorce statistics. On average, parents of daughters are more likely to divorce, and I’ve argued (here, here and here, citing research by Gordon Dahl and Enrico Morretti) that daughters probably cause divorce. But now we have a rival theory: Perhaps beauty causes both divorce and daughters.

It’s not hard to see how beauty might (on average) cause divorce; for example, it seems likely that the proverbial “trophy wives” are both disproportionately beautiful and disproportionately likely to be dumped when their beauty fades. So if the beautiful really have 36 percent more daughters, that’s plenty big enough to explain the daughter/divorce correlation.

But I don’t believe it. First, the “36 percent” number is just sloppy reporting. The actual number—which I found in the original paper by Satoshi Kanazawa of the London School of Economics—is 26 percent. (He’s also written a book on this and related research, which I have not read.)

Twenty-six percent is still huge. But it’s also probably spurious. For starters, the sample size is pretty small. Professor Kanazawa started with a sample of about 3000 women, rated from 1 to 5 on attractiveness. (I’ll tell you later where the ratings came from.) Of these women, about 350 were rated 5, and it’s true that these women had a great preponderance of daughters. But that’s a pretty small sample—small enough that there’s about a 5% chance the result is just a statistical fluke. (By contrast the
daughters/divorce study by Dahl and Moretti was based on a sample—drawn from census data—of 3 million.)

Worse yet, those women rated 4 (“attractive” as opposed to “very attractive”) had a great preponderance of sons. Sons were in fact much more common among both the “unattractive” 2’s and the “attractive” 4’s, while daughters were much more common among the 5’s. Among the 1’s and 3’s (“very unattractive” and “average”), the sex ratio is 50/50. Not much of a pattern there.

In fact, Professor Kanazawa’s strong result relies crucially on the fact that he lumped the 1’s, 2’s, 3’s and 4’s into a single category and compared them to the 5’s. If he had lumped the 4’s and 5’s together into a single category called “above average”, he’d have gotten a very different result.

In fact, there are a lot of ways to lump these data, and each way of lumping them gives you another shot at finding a statistical fluke. Given that the sample size makes flukes pretty likely to begin with, it’s not at all unlikely that the professor managed to stumble across one.

And there’s another problem. The sample consists of mothers who were interviewed about their families and then rated for attractiveness by the interviewer. It is not at all implausible to me that a mother talking about her daughter–or holding a little girl on her lap—might present, on average, a different appearance than a mother talking about her son. So the attractiveness ratings are contaminated from the get-go. I would have found this study a lot more convincing if the attractiveness ratings had been based on wedding photos, or other photos from before the children were born.

In fact, all of the mothers in the sample were between the ages of 18 and 28, which means that all the children in question were very young. I’ve watched enough toddlers in my life to believe that, on average, the mother of a two year old boy is going to look a little more haggard than the mother of a two year old girl—possibly enough to keep her out of that “very attractive” category. If Professor Kanazawa has discovered anything at all, I suspect it’s not that beauty causes girls but that boys can run you ragged.

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“Between the Folds” has its national television debut tomorrow night (Tuesday, December 8 on PBS; check your local listings for the time). Or check here for additional showings.

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