Each year, literary agent and science salonista John Brockman poses a question about science and gets a slew of answers from scientists, writers, and other folks. This year’s question is

WHAT IS YOUR FAVORITE DEEP, ELEGANT, OR BEAUTIFUL EXPLANATION?

Brockman got 187 responses, totaling some 126,700 words. A book, you say! Well, if this year is like previous ones, this year’s answers will indeed become a book. But in the meantime, you can browse the answers for yourself, perhaps plucking out those of your favorite people. (Fellow Discover blogger cosmologist Sean Carroll chooses Einstein’s explanation of gravity, for example.)

I found this year’s question particularly thought-provoking. Why is it that we call an equation or a theory “beautiful”? They don’t have pretty hazel eyes. They aren’t desert landscapes. I’m not sure of the answer. Scientific explanations seem to be beautiful if they give sense to confusing complexity in a very short space. Or maybe we just like the feeling we get when we consider how our puny human brains can interpret the universe.

For a lot of physicists, the beauty of an equation seems to be a good hint that it’s probably true. But I’m always a bit suspicious of beauty as a guide to the natural world. A number of contributors selected Darwin’s theory of evolution as their favorite explanation, and there’s no doubt that’s both beautiful and true. But there have been some wonderfully beautiful accounts of the natural world that have proven awesomely wrong. I was reminded of this fact while working on a new version of my evolution textbook (this one’s for biology majors). I was re-researching how scientists first came to appreciate the vast age of our planet, and realized it was a bit more complicated than I had previously appreciated. So that’s what I chose as my answer, which I’m reprinting here in full:

A Hot Young Earth: Unquestionably Beautiful and Stunningly Wrong

Around 4.567 billion years ago, a giant cloud of dust collapsed in on itself. At the center of the cloud our Sun began to burn, while the outlying dust grains began to stick together as they orbited the new star. Within a million years, those clumps of dust had become protoplanets. Within about 50 million years, our own planet had already reached about half its current size. As more protoplanets crashed into Earth, it continued to grow. All told, it may have taken another fifty million years to reach its full size—a time during which a Mars-sized planet crashed into it, leaving behind a token of its visit: our Moon.

The formation of the Earth commands our greatest powers of imagination. It is primordially magnificent. But elegant is not the word I’d use to describe the explanation I just sketched out. Scientists did not derive it from first principles. There is no equivalent of E=mc2 that predicts how the complex violence of the early Solar System produced a watery planet that could support life.

In fact, the only reason that we now know so much about how the Earth formed is because geologists freed themselves from a seductively elegant explanation that was foisted on them 150 years ago. It was unquestionably beautiful, and stunningly wrong.

The explanation was the work of one of the greatest physicists of the nineteenth century, William Thompson (a k a Lord Kelvin). Kelvin’s accomplishments ranged from the concrete (figuring out how to lay a telegraph cable from Europe to America) to the abstract (the first and second laws of thermodynamics). Kelvin spent much of his career writing equations that could let him calculate how fast hot things got cold. Kelvin realized that he could use these equations to estimate how old the Earth is. “The mathematical theory on which these estimates are founded is very simple,” Kelvin declared when he unveiled it in 1862.

At the time, scientists generally agreed that the Earth had started out as a ball of molten rock and had been cooling ever since. Such a birth would explain why rocks are hot at the bottom of mine shafts: the surface of the Earth was the first part to cool, and ever since, the remaining heat inside the planet has been flowing out into space. Kelvin reasoned that over time, the planet should steadily grow cooler. He used his equations to calculate how long it should take for a molten sphere of rock to cool to Earth’s current temperature, with its observed rate of heat flow. His verdict was a brief 98 million years.

Geologists howled in protest. They didn’t know how old the Earth was, but they thought in billions of years, not millions. Charles Darwin—who was a geologist first and then a biologist later—estimated that it had taken 300 million years for a valley in England to erode into its current shape. The Earth itself, Darwin argued, was far older. And later, when Darwin published his theory of evolution, he took it for granted that the Earth was inconceivably old. That luxury of time provided room for evolution to work slowly and imperceptibly.

Kelvin didn’t care. His explanation was so elegant, so beautiful, so simple that it had to be right. It didn’t matter how much trouble it caused for other scientists who would ignore thermodynamics. In fact, Kelvin made even more trouble for geologists when he took another look at his equations. He decided his first estimate had been too generous. The Earth might be only 10 million years old.

It turned out that Kelvin was wrong, but not because his equations were ugly or inelegant. They were flawless. The problem lay in the model of the Earth to which Kelvins applied his equations.

The story of Kelvin’s refutation got a bit garbled in later years. Many people (myself included) have mistakenly claimed that his error stemmed from his ignorance of radioactivity. Radioactivity was only discovered in the early 1900s as physicists worked out quantum physics. The physicist Ernst Rutherford declared that the heat released as radioactive atom broke down inside the Earth kept it warmer than it would be otherwise. Thus a hot Earth did not have to be a young Earth.

It’s true that radioactivity does give off heat, but there isn’t enough inside the planet is to account for the heat flowing out of it. Instead, Kelvin’s real mistake was assuming that the Earth was just a solid ball of rock. In reality, the rock flows like syrup, its heat lifting it up towards the crust, where it cools and then sinks back into the depths once more. This stirring of the Earth is what causes earthquakes, drives old crust down into the depths of the planet, and creates fresh crust at ocean ridges. It also drives heat up into the crust at a much greater rate than Kelvin envisioned.

That’s not to say that radioactivity didn’t have its own part to play in showing that Kelvin was wrong. Physicists realized that the tick-tock of radioactive decay created a clock that they could use to estimate the age of rocks with exquisite precision. Thus we can now say that the Earth is not just billions of years old, but 4.567 billion.

Elegance unquestionably plays a big part in the advancement of science. The mathematical simplicity of quantum physics is lovely to behold. But in the hands of geologists, quantum physics has brought to light the glorious, messy, and very inelegant history of our planet.

[Post-script: Thanks to responses from readers, I can see how this essay is confusing. I added some passages from the papers I cite below down in the comment thread, which I hope can clear things up a bit.]

[Update: For an up-to-date review of the age and formation of the Earth, see this paper [abstract, free pdf] For a great look at Kelvin’s work, see this piece in American Scientist or the more technical paper on which it was based (free pdf).]

[Image: Photo by Hawaiian Sea - http://flic.kr/p/8AyKnC via Creative Commons]

Drew Berry is one of the great movie-makers of the molecular world. He makes gorgeous computer visualizations of DNA, proteins, and the various goings-on inside the cell. Last night I spent a little time watching a new TEDx talk of his just posted online. My first thought was, “Why didn’t I get to see these movies when I was learning about biology as a kid? Life is unfair.” Compared to the flat cartoons of textbooks, or even the crude animations in documentaries of yore, Berry’s work seems to come from some advanced alien civilization.

In case you haven’t seen Berry’s work before, I’ve embedded his lecture here. (You may have heard about him when he got a recent Macarthur “genius” grant.) If you have seen his stuff before, I’d suggest you watch this anyway. And this time, don’t just watch. Listen.

When I first saw Berry’s work a while back, I was immediately gob-smacked. But as I watched his synchronized swimming of molecules a while longer, I realized after a while that I didn’t understand a lot of what was going on. I didn’t know the names of the molecules I was looking at, and, more importantly, I couldn’t tell what a lot of them were doing. The only sense I could make of it all derived from what I already knew.

Berry’s TEDx talk is more satisfying because it’s a talk. You look at the mesmerizing images, and Berry explains what you’re seeing. What’s really interesting is how he–no doubt unconsciously–uses words that switch on the mental eye. When he zooms in on a chromosome, he points out structures passing through it that look “like whiskers,” which act as the “scaffolding” for the cell (the microtubules). He then zooms into the place where the chromosome and microtubule meet, the kinetochore. What you see looks like a supercomputer’s acid trip. But you can make sense of what you see because Berry uses metaphors. He calls it a “signal broadcasting system.” Now all the molecules jittering around aren’t totally random. We can see how molecules come together to make life possible.

There’s no question that people like Berry are going to be making the movies that fill our heads in our future when we think about what’s going on in our bodies. But those movies will need good soundtracks.

I’ve written a few times here about the battle over a virus called XMRV, and its supposed link to chronic fatigue system. I just wanted to point this morning to a few articles by some fine writers about the latest twist: the paper that first claimed a link has been completely retracted.

Ivan Oransky in Reuters

Jon Cohen in Science

Ewen Callaway in Nature

[Image: Wikipedia]

Eric Michael Johnson, an historian of science, is also the writer behind an excellent blog, “The Primate Diaries.” The other day he gave me a call to talk about science writing. He put together a two-part Q&A that he published today (part one and part two) that ranges from the science writing in Moby Dick to the microscopic virtues of Twitter. I was particularly flattered to get a portrait done by Nathaniel Gold. Check it out!

For the third year in a row I had the pleasure of serving as a judge for the Imagine Science Film Festival. Along with fellow judged neuroscientists David Eagelman and Darcy Kelley and documentary filmmaker Robb Moss, I watched a slew of short films that touched in one way or another on science. The awards were just announced, and so I thought I’d hunt around for some online sites where you can watch them, either as previews or in their entirety. Here’s what I found: (more…)

If you haven’t been tracking the arsenic life saga closely over the past ten months, check out Tom Clynes’s big feature at Popular Science. It focuses on the travails of Felisa Wolfe-Simon, the lead author on the paper, who has gone from the Olympian heights of TED talks to getting “evicted” from the lab where she’s worked for the past couple years. (Her word.)

For those of us who’ve been tracking the story for a while, that last fact popped out. Wolfe-Simon had been working in the lab of her co-author Ronald Oremland, but that’s now over. Let’s recall that her senior colleagues dubbed the intriguing microbe she studied GFAJ-1, for “Get Felicia A Job.”

It’s a good article. I won’t be forgetting the opening scene anytime soon, when Wolfe-Simon is ambivalently posing for a television crew, and she sinks into the mud of Mono Lake, where she first encountered GFAJ-1.

But I do share some of the reservations that science writer David Dobbs expresses over at his blog Neuron Culture. As a genre, the profile is one of the most addictive and enjoyable of all. It doesn’t matter if the profile is of a hero or a scoundrel; the story is good as long as it’s full of human nature in all its extremes. But profiles of scientists are tricky, because science transcends any single individual scientist. To do the science justice, you may need to pull the spotlight away and get into the less human stuff, like chemical reactions and pH levels.

The story thus focuses mainly on Wolfe-Simon, with scientific critics effectively reduced to mean chair-throwers, their scientific objections dispatched in a couple lines. People and events are relevant insofar as they affect Wolfe-Simon. And in the process, Clynes writes some mystifying stuff:

What made the level of criticism so extraordinary is that the paper, in itself, is not so flawed that it should not have been published. The argument was compelling, the conclusions were measured, the data was thorough, and the paper made it through the same peer-review process as other articles in Science.

And Clynes has us believe that this barrage of extraordinary, brutal criticism (or perhaps questions from journalists) forced Wolf-Simon and her colleagues to go into witness protection:

Overwhelmed with questions from the media, Wolfe-Simon went underground. Guided by NASA’s PR team, she and Oremland and the paper’s other co-authors began citing NASA spokesperson Dwayne Brown’s position that the authors would not be responding to individual criticisms. The agency, Brown said, didn’t feel it appropriate to debate science using the media and bloggers. Discourse should occur in scientific publications.

“I wasn’t hiding, but I didn’t want to get involved in a Jerry Springer situation, with people throwing chairs,” Oremland says. “There are hundreds of blogs some viable and some off the wall, and they all want an immediate response. To try to engage in scientific commentary that way seems like a descent into madness.”

What the–?

I’ve seen this version of the arsenic life story before, and I can say (as one of the people mentioned in Clynes’s story) that it simply does not square with the facts. I really hope it doesn’t get set in people’s minds like concrete.

Let’s just run through the timeline, shall we?

Thursday, December 2: An eagerly anticipated NASA press conference, the publication of the paper in Science, front-page news in leading newspapers, with no articles I’m aware of dealing seriously with the critics.

[Update: Friday December 3: Chembark, a chemistry blogger, declares, "I am not convinced."  Jim Hu of Texas A&M writes, "Could there be arsenic-based backbone in the DNA? Maybe. But it would be extraordinary and so I would like to see better evidence." I for one missed these posts.]

Saturday, December 4: Rosie Redfield, a microbiologist with a blog she mainly uses for her class, expresses deep skepticism. It is the only such blog post I know of that presented a detailed criticism at this point in the timeline. [Update--I should say, the only blog post I was aware of.]

Sunday, December 5: Alex Bradley, another microbiologist, guest-blogs at We Beasties in a similar vein. The criticisms are harsh but deal in the scientific details of the paper.

The audience for both posts is small–an audience of fellow microbe junkies.

By Sunday afternoon, I think it’s time to write something. I’m wondering if Redfield and Bradley are saying what a lot of other scientists are thinking. I start getting in touch with leading experts in the areas that the paper touches on. In the next couple days they will get back to me, and just about all of them say the paper has serious problems, one simply declaring it should never have been published.

Naturally, it’s only fair to give the authors of the study a chance to respond. So on Sunday afternoon, I send links to the two blog posts above to Oremland and Wolfe-Simon. Oremland promptly writes back, “Sorry, but ‘nope.’”

I’m a bit surprised and email back to find out why. Here’s what I get:

It is one thing for scientists to “argue” collegially in the public media about diverse details of established notions, their own opinions, policy matters related to health/environment/science.

But when the scientists involved in a research finding published in scientific journal use the media to debate the questions or comments of others, they have crossed a sacred boundary.

Monday, December 6: Wolfe-Simon emails back at 12:42 AM, a few hours after I emailed her. She cc’s all her co-authors and administrators at NASA, including the director of the astrobiology program:

Mr. Zimmer,

I am aware that Dr. Ronald Oremland has replied to your inquiry. I am in full and complete agreement with Dr. Oremland’s position (and the content of his statements) and suggest that you honor the way scientific work must be conducted.

Any discourse will have to be peer-reviewed in the same manner as our paper was, and go through a vetting process so that all discussion is properly moderated. You can see many examples in the journals Science and Nature, the former being where our paper was published. This is a common practice not new to the scientific community. The items you are presenting do not represent the proper way to engage in a scientific discourse and we will not respond in this manner.

Regards,
Felisa

In the morning I get busy on my story. That evening, the CBC comes out with a story focused on Redfield’s complaint, relaying NASA’s statement that it’s not appropriate for scientists to debate each other in the media. I scratch my head and get back to work.

Tuesday, September 7: I publish a story in Slate about arsenic life, describing the detailed criticisms of a number of scientists (which I’ve posted in full on the Loom). I quote the no-comments of Oremland and Wolfe-Simon.

—Now, we can have a fine debate about whether journalists should ask scientists to respond to criticism from other scientists about their work. Oremland and Wolfe-Simon may truly believe that this crosses a sacred boundary. I say it doesn’t. It’s standard practice. Science, where the arsenic life paper was published, lets reporters get their hands on papers early, and reporters regularly seek out other scientists for comments on those papers before publishing their articles. If two scientists post their thoughts on public blogs, there is no difference in asking authors of a paper to respond to their critiques. Trying to make such a distinction is pointless.

I’ve been doing this kind of thing for a long time, and I have never encountered a response like this one from the hundreds of scientists I’ve interviewed. And that includes scientists who work for or are sponsored by NASA, despite the claims that popped up that NASA policy forbids such open debate. In fact, the scientist who gave me the headline for my story–”This Paper Should Not Have Been Published”–is herself part of NASA’s astrobiology team. Did she say, “Mister, you’ve crossed a sacred boundary”? Nope. She wrote me a long, detailed explanation of why she thought the paper failed.

In other words, I’m pretty sure I’d win that debate.

But the story you get from Clyne and others is not that Oremland and Wolfe-Simon had some a priori policy never to deign to comment on criticism that weren’t published in a scientific journal. It’s that they were overwhelmed by Jerry Spinger-grade hordes of unseemly scientist bloggers and relentless journalists–so overwhelmed that they had to vanish. They were victims.

But for this version of events to be true, the hordes must have stormed their lab in a single day–at some point between Saturday, when Redfield posted her critique, and Sunday, when the scientists told me they wouldn’t comment for the story. As far as I can tell, there were just two blog critiques published during that time, and a CBC news article. If someone can point to any evidence of this alleged horde that I’ve somehow missed–perhaps the gnawed bones of some graduate student left in its trail–I’d love to see it.

Otherwise, this just seems like one of those stories that sounds good in hindsight. And if any good is going to come out of this strange saga, we should strive to get all its stories straight.

[Update: Clynes responds.]

I’ve devoted a few posts (here and here and here) to the saga of a disputed link between chronic fatigue syndrome and a virus called XMRV. This week marks the next chapter in the story, with more evidence that the original results were at least partly due to contamination and a partial retraction of the original paper. Two great writers at Science, Martin Enserink and Jon Cohen, have put together an epic telling of this affair, from the first reports two years ago to the latest developments. The magazine has wisely put the piece out in front of their paywall. Do read it.

As Enserink and Cohen note, this is not the final word. That will probably come early next year, when a larger study led by Ian Lipkin of Columbia. We’ll see then if the link is buried at last, or lives to see another day.

I learned that Google has retooled its invitation system for Google+. Instead of manually adding names into a message field, I can just drop a link into this post and offer 150 invitations. So if you want to dabble in this new experiment in social media and enforced non-pseudonymity, please click here.

Last month I contemplated the staggering diversity of microbes in my bellybutton–an experience made possible by my participation in a survey of microbiome diversity carried out by scientists at North Carolina State University. At the time, I thought I was quite the host. I was informed there were 53 species living in my navel, some of which had never been seen on skin before and some of which were altogether new to science. I was even informed that I was a “wonderland.”

Well, the project is moving forward at quite a clip, and the scientists are starting to push more of their data online. Here you can see the species from the first 60 volunteers they’ve studied. The lists are coded by number–I’m B944. I appear to have lost a species so I’m down to 52. And 52 is, I’m seeing, nothing to blog home about. So far, the diversity champion is the anonymous owner of bellybutton B1288. 107 species! Now that’s a wonderland….

Lucas Brouwers, one of the new bloggers at Scientific American’s snazzy new blog network, takes a look at an intriguing paper (free pdf). The authors of the paper in examined many different strains of E. coli and come to a remarkable conclusion: they’ve been splitting apart so far that they may soon no longer be a single species. Check it out. (And, if you have a lot of time to spare, check out the rest of Scientific American’s fine line-up of bloggers.)

[Note: Some folks don't like the phrase "chlorine-based life." I welcome suggestions in the comments for a better shorthand descriptor]

Last year, a team of NASA-funded scientists claimed to have found bacteria that could use arsenic to build their DNA, making them unlike any form of life known on Earth. That didn’t go over so well. (See my two pieces for Slate for a quick recap: #1, #2.)  One unfortunate side-effect of the hullabaloo over arsenic life was that people were distracted from all the other research that’s going on these days into weird biochemistry. Derek Lowe, a pharmaceutical chemist who writes the excellent blog In the Pipeline, draws our attention today to one such experiment, in which E. coli is evolving into a chlorine-based form of life.

As I wrote in Microcosm, scientists have been contorting E. coli in all sorts of ways for years now to figure out what the limits of life are. Some researchers have rewritten its genetic code, for example, so that its DNA can encode proteins that include amino acids that are not used by any known organism.

Others have been tinkering with the DNA itself. In all living things, DNA is naturally composed of four compounds, adenine, cytosine, guanine, and thymine. Thymine, shown in the upper left panel here, is a ring of carbon and nitrogen atoms, with oxygen and hydrogens atoms dangling off the sides. Since the 1970s, some scientists have tried to swap thymine for other molecules, such as the one show to the lower left here. This compound is called 5-chlorouracil, the “chloro-” referring to the chlorine marked here in red. No natural DNA contains chlorine.

A team of German scientists recently published the details of an experiment that has taken them a long way towards E. coli that live only on chlorouracil. They didn’t simply sit down and type out a new sequence for E. coli’s genome–we just aren’t smart enough to make such predictions. Instead, they harnessed evolution. The scientists fed a population of E. coli chlorouracil, supplementing their dieet with a little thymine to keep them from starving to death. Bacteria that picked up mutations that allowed them to use some chlorouracil instead of thymine were favored by natural selection. They lowered the thymine levels to increase the pressure on the bacteria to evolve more.

After five months of this evolution, the E. coli underwent a noticeable change. For one thing, they changed shape. They started out in the normal capsule shapes in the top photo, turned into the worm-like shapes below, and then later became capsule-shaped again. The scientists also found that the bacteria were slurping up chlorouracil. Ninety percent of the thymine in their DNA was replaced by chlorouracil. As Lowe writes, the scientists found that the bacteria were still incorporating some thymine into their DNA through a pathway no one had discovered before (which just shows how marvelously mysterious E. coli remains after a century of intensive study). The scientists shut down this new pathway, and found that the bacteria still grew happily. But now they only had 1.5% thymine in their DNA.

This E. coli is different from ordinary E. coli, with over a thousand mutations that enable it to take up chlorouracil. But it is not quite yet off the grid. If it is fed thymine and no chlorouracil, it can switch back to a conventional way of life. So now we’ll see if scientists can further evolve the bacteria so that they can only live on chlorouracil, and starve on thymine.

I checked in with Steven Benner, a chemist who has raised a lot of concerns about the arsenic-life research last year. What did he think of the new research?

“It looks true,” he said.

Benner also pointed out that using chlorine in DNA is a pretty modest changed compared to what would have been required to substitute arsenic for phosphorus in the backbone of DNA. Swapping in chlorine doesn’t change how the compound reacts with other compounds, doesn’t change its size much, doesn’t change its stability much, and so on.

On the other hand, it appears to have the advantage of being real.

[Update: Rosie Redfield, an outspoken critic of the arsenic-life research, just got back to me with nice things to say as well:

"This looks quite solid to me (I read it quickly). The technology is nice, very appropriate for the project. No red flags at all."]

It’s been very gratifying to listen to the conversation that’s been triggered by my essay in this Sunday’s New York Times on scientific self-correction. Here, for example, is an essay on the nature of errors in science by physicist Marcelo Gleiser at National Public Radio. Cognitive scientist Jon Brock muses on how to get null results published.

I also got an email from Eliot Smith, the editor of the Journal of Personality and Social Psychology who accepted the controversial clairvoyance paper I described in my essay. I wrote that three teams of scientists failed to replicate the results and that all three studies were rejected by the journal because they don’t accept simple replication studies.

Mr. Zimmer

Your recent Times column stated the following:

Best regards,
Eliot Smith

I’ve passed on Smith’s message to my editor at the Times, and I’ll also take this opporunity here to apologize for the error.

I’m not sure how meaningful it is in the context of my essay, since my point was that policies against publishing replication studies get in the way of science’s self-correction. But a mistake is a mistake.