I know what you’re thinking: “Gee, Sean, here it is your birthday, and me with no way to send you a present.” But that’s not true! Because I would consider it a wonderful present if you could send $10 to, for example:

Ms. V’s classroom in Louisiana, where junior-high students in a high-poverty area need some calculators to help in their science classes.

Ms. H’s classroom in Oklahoma, whose kindergarten students need some white boards to fit group lessons into their crowded room.

Ms. W’s classroom in New York City, where young children with autism need basic learning aids to help them tackle math.

Or any one of various other worthy classrooms. And don’t feel constrained by that $10 suggestion — there’s plenty more room for larger donations! It’s like you’re giving me a present, and you benefit yourself from the feeling that you are doing something awesome.

In return: actual bloggy content on its way this week.

A few weeks ago we were a bit startled to find a “Science Saturday” episode of BH.tv featuring Paul Nelson, an honest-to-God young-Earth creationist. Not really what most of us like to think of as “science.” So there were emails back and forth trying to figure out what went on. David Killoren, who is the person in charge of the Science Saturday dialogues, is an extremely reasonable guy; we had slightly different perspectives on the matter, but in the end he appreciated the discomfort of the scientists, and we agreed to classify that dialogue as a “failed experiment,” not something that would be a regular feature.

So last week we were startled once again, this time by the sight of a dialogue between John McWhorter and Michael Behe. Behe, some of you undoubtedly know, is a leading proponent of Intelligent Design, and chief promulgator of the idea of “irreducible complexity.” The idea is that you can just look at something and know it was “designed,” because changing any bit of it would render the thing useless — so it couldn’t have arisen via a series of incremental steps that were all individually beneficial to the purpose of the object. The classic example was a mousetrap — until someone shows how a mousetrap is, in fact, reducibly complex. Then you change your choice of classic example. Behe had his butt handed to him during his testimony at the Kitzmiller vs. Dover trial over teaching intelligent design in schools; but embarrassment is not an arrow in the ID quiver, and he hasn’t been keeping quiet since then.

John McWhorter is not a biologist — he’s apparently a linguist, who writes a lot about race. In any event, the dialogue was hardly a grilling — McWhorter’s opening words are:

Michael Behe, I am so glad to meet you, and thank you for agreeing to do this. This is one of the rare times that I have initiated a Bloggingheads pairing, and it’s because I just read your book The Edge of Evolution from 2007, and I found it absolutely shattering. I mean, this is a very important book, and yet I sense, from the reputation or the reception of your book from ten-plus years ago, Darwin’s Black Box, that it may be hard to get a lot of people to understand why the book is so important.

I couldn’t listen to too much after that. McWhorter goes on to explain that he doesn’t see how skunks could have evolved, and what more evidence do you need than that? (Another proof that belongs in the list, as Jeff Harvey points out: “A linguist doesn’t understand skunks. Therefore, God exists.”) Those of us who have participated in Bloggingheads dialogues before have come to expect a slightly more elevated brand of discourse than this.

Then, to make things more bizarre, the dialogue suddenly disappeared from the site. I still have very little understanding why that happened. The reason given was that it was removed at McWhorter’s behest, because he didn’t think it represented him, Behe, or BH.tv very well. I’m sure that is the reason it was removed, although I have no idea what McWhorter was thinking — either when he proposed the dialogue, or while he was doing it, or when he asked that it be taken down. Certainly none of we scientists who were disturbed that the dialogue existed in the first place ever asked that it be removed. That feeds right into the persecution complex of the creationists, who like nothing more than to complain about how they are oppressed by the system. And, on cue, Behe popped up to compare Bloggingheads to Stalinist Russia. But now the dialogue is back up again — so I suppose old comrades can be rehabilitated, after all.

But, while none of the scientists involved with BH.tv was calling for the dialogue to be removed, we were a little perturbed at the appearance of an ID proponent so quickly after we thought we understood that the previous example had been judged a failed experiment. So more emails went back and forth, and this morning we had a conference call with Bob Wright, founder of BH.tv. To be honest, I went in expecting to exchange a few formalities and clear the air and we could all get on with our lives; but by the time it was over we agreed that we were disagreeing, and personally I didn’t want to be associated with the site any more. I don’t want to speak for anyone else; I know that Carl Zimmer was also very bothered by the whole thing, hopefully he will chime in.

It’s important to understand exactly what the objections are. (Again, speaking only for myself; others may object on different grounds.) It’s too easy to guess at what someone else is thinking, then argue against that, rather than work to understand where they are coming from. I tried to lay out my own thinking in the Grid of Disputation post. Namely: if BH.tv has something unique and special going for it, it’s the idea that it’s not just a shouting match, or mindless entertainment. It’s a place we can go to hear people with very different perspectives talk about issues about which they may strongly disagree, but with a presumption that both people are worth listening to. If the issue at hand is one with which I’m sufficiently familiar, I can judge for myself whether I think the speakers are respectable; but if it’s not, I have to go by my experience with other dialogues on the site.

What I objected to about the creationists was that they were not worthy opponents with whom I disagree; they’re just crackpots. Go to a biology conference, read a biology journal, spend time in a biology department; nobody is arguing about the possibility that an ill-specified supernatural “designer” is interfering at whim with the course of evolution. It’s not a serious idea. It may be out there in the public sphere as an idea that garners attention — but, as we all know, that holds true for all sorts of non-serious ideas. If I’m going to spend an hour of my life listening to two people have a discussion with each other, I want some confidence that they’re both serious people. Likewise, if I’m going to spend my own time and lend my own credibility to such an enterprise, I want to believe that serious discussions between respectable interlocutors are what the site is all about.

Here’s the distinction I want to draw, which might admittedly be a very fine line. If someone wants to talk about ID as a socio/religio/political phenomenon worth of study by anthropologists and sociologists, that’s fine. (Presumably the right people to have that discussion are anthropologists or sociologists or historians/philosophers of science, not biochemists who have wandered into looney land.) If someone wants to talk to someone who believes in ID about something that person has respectable thoughts about, that would also be fine with me. If you want to talk to a theologian about theology, or a politician about politics, or an artist about art, the fact that such a person has ID sympathies doesn’t bother me in the least.

But if you present a discussion about the scientific merits of ID, with someone who actually believes that such merits exist — then you are wasting my time and giving up on the goal of having a worthwhile intellectual discussion. Which is fine, if that’s what you want to do. But it’s not an endeavor with which I want to be associated. At the end of our conversations, I understood that my opinions about these matters were very different from those of the powers that be at BH.tv.

I understand that there are considerations that go beyond high-falutin’ concerns of intellectual respectability. There is a business model to consider, and one wants to maintain the viability of the enterprise while also having some sort of standards, and that can be a very difficult compromise to negotiate. Bob suggested the analogy of a TV network — would you refuse to be interviewed by a certain network until they would guarantee to never interview a creationist? (No.) But to me, the case of BH.tv is much more analogous to a particular TV show than to an entire network — it’s NOVA, not PBS, and the different dialogues are like different episodes. There is a certain common identity to things that BH.tv does, in a way that simply isn’t comparable to the wide portfolio of a TV network. Appearing for an hour-long dialogue creates connection with a brand in a way that being interviewed for 30 seconds on a TV news spot simply does not. If there were a TV show that wanted me on, but I had doubts about their seriousness, I would certainly decline (and I have).

And heck, we all have a business model. I’d like to sell some books, and I was really looking forward to doing a BH.tv dialogue with George Johnson when my book came out — it would have been a lot of fun, and perhaps even educational. But at the end of the day, I’m in charge of defending my own integrity; life is short, and I have to focus on efforts I can get completely behind without feeling compromised.

Having said all that, I’m very happy to admit that there’s nothing cut-and-dried about any of these issues, and I have a great deal of sympathy for anyone who feels differently and wants to continue contributing to BH.tv. The site provides a lot of high-quality intellectual food for thought, and I wish it well into the future. These decisions are necessarily personal. A few years ago I declined an invitation to a conference sponsored by the Templeton foundation, because I didn’t want to be seen as supporting (even indirectly) their attempts to blur the lines between science and religion. But even at the time I admitted that it wasn’t an easy choice, and couldn’t blame anyone who decided to go. Subsequently, I’ve participated in a number of things — the World Science Festival, the Foundational Questions Institute, and BH.tv itself — that receive money from Templeton. To me, there is a difference between taking the money directly, and having it “laundered” through an organization that I think is otherwise worthwhile. Not everyone agrees; Harry Kroto has expressed deep disappointment that I would sully myself in this manner. And that’s understandable, too; we all have to look at ourselves in the mirror each morning.

So, on we go, weaving our own uncertain ways through the briars of temptation and the unclear paths of right and wrong. Or something like that. I have no doubt that BH.tv will continue to put up a lot of good stuff, and that they’ll find plenty of good scientists to take my place; meanwhile, I’ll continue to argue for increasing the emphasis on good-faith discourse between respectable opponents, and mourn the prevalence of crackpots and food fights. Keep hope alive!

Update: Bob Wright has left a comment here. (See also a comment by David Killoren here.) And at some point soon, a more official BH.tv editorial policy will appear here.

Bob is unhappy that I left out some of the points he made in our conversation, which is somewhat reflective of the fact that we were talking past each other. I was not looking for a “pledge” of anything at all. Rather, I was hoping — and completely expecting — to hear a statement somewhat along these lines: “Of course we all agree that when someone listens to a dialogue on BH.tv, they have a reasonable expectation that both speakers are non-crackpots.” But I don’t think we do agree on that. I am personally not interested in interrogating crackpots to understand their motives; they get more than enough attention as it is, and I’m more interested in discussions between reasonable people. That’s why, unlike some of the commenters, I wouldn’t feel especially different if it had been an expert biologist interrogating a creationist. Different folks have different feelings about this, and that’s why it’s good that we have a big internet.

following on from on our first effort, and covering different, and somewhat more controversial topics.

Hope you enjoy it.

We’ll post a link to the new episode when it comes out tomorrow. At one stage Sean and I discuss the initial conditions for inflation, and in doing so we were led into the issues of eternal inflation, entropy and the arrow of time (I guess he’s written some sort of extended blog post about it). Leading up to this, however, I brought up the question of what it means to require a sufficiently large, smooth, potential energy dominated patch of the universe in order for inflation to begin. I referred to a paper I wrote many years ago with Tanmay Vachaspati and I thought that it might be useful to describe that work here. I’ve done this before, over at Orange Quark, but it can’t hurt to have a version here also. This will be a little more technical than usual, but far less technical than the actual paper (hopefully).

As I first learned about inflation, the idea can be summarized as the following: the universe is born and one can say very little about it since quantum gravity (whatever that is) is undoubtedly important at extremely early times. However, after some time (approximately the Planck time), the semi-classical universe emerges, and we can begin to analyze meaningfully such things as the dynamics of field theories, and the response of gravity to them. There is no a priori reason for the universe to be homogeneous at this epoch. However, local, causal particle dynamics can act to homogenize patches of the universe. After some time, a small patch becomes homogeneous and dominated by the vacuum energy of a scalar field. This patch then undergoes inflation – a quasi-exponential period of expansion in which the original small patch expands to a size many orders of magnitude larger than the observable universe today. This expansion explains the flatness of the universe, and its homogeneity on large scales today.

Now, there are a number of models of inflation in which the above story is modified (in particular, chaotic inflation), and I’ll get back to them later. For now let me focus on this claim of homogeneity in the theories I described above.

Why does inflation, as described, “solve” the homogeneity (or horizon) problem? Clearly, the idea is that the homogeneity of the initial pre-inflationary patch, explained by causal physics, is translated into the homogeneity of the larger space after the exponential expansion. At the risk of being pedantic, this can only be true if the original patch is made homogeneous by causal processes, otherwise homogeneity would once again be an assumption, albeit a less severe one.

What did we do in our paper? We first imagined that the early universe, emerging from the Planck epoch, was not inflating. To make progress we’ll need a few definitions, which I’ll define below in a more blog-friendly way than in the paper.

Let’s focus on spherically symmetric space-times and pick an origin. Then examine spherical surfaces centered on this origin. Such surfaces can be divided into three categories in the following way. Imagine sitting on such a surface with two flashlights, both pointing radially and close together. The flashlights can both be pointing outwards (away from the origin), or both pointing inwards (towards the origin). The categories are then:

1. NORMAL: When the flashlights point inwards, the rays converge to the origin. When they point outwards, the rays diverge away from the origin. This is how regular parts of space-time behave; for example, points in our universe closer to us than the horizon.
2. TRAPPED: When the flashlights point inwards, the rays converge to the origin. When they point outwards, the rays still converge to the origin. Such surfaces can be found inside the horizon of a black hole.
3. ANTI-TRAPPED: When the flashlights point inwards, the rays nevertheless diverge away from the origin. When they point outwards, the rays diverge away from the origin. Such surfaces can be found, for example, beyond the horizon in our universe.

Now, back to what our paper showed. If the universe is not born inflating, then we want to imagine that, at some later time, local, causal particle dynamics yield a patch that is homogeneous and vacuum-dominated, and thus begins to inflate. The fundamental question for us was; how small can this patch be?

The main tool we used is called the Raychaudhuri equation. It describes the rate of change of divergence of close by pairs of light rays, as I described above. The equation is a little complicated but, by considering the types of light rays I mentioned above (perpendicular to spherical surfaces), and by making two further assumptions: that the Einstein equations are satisfied, and that the weak energy condition holds (matter isn’t too weird), the most important consequence of the Raychaudhuri equation can be stated as: Light rays pointing inwards cannot emanate from a normal surface and cross an anti-trapped one.

What does this mean? Well, if the original inflating patch is smaller than the Hubble size of the background space-time, then, it can be shown that light rays violating the above statement must exist. Thus, we conclude that the size of the initial inflating patch is at least as large as the Hubble size of the background space-time. But this size is large compared to typical particle physics processes that can act to homogenize a region (actually, if the background space-time is radiation-dominated FRW, the Hubble size IS the causal horizon). Thus, in this simple context it is hard to see how such an initially homogeneous inflating patch might form. This was our main result.

However, one of the things Sean and I discussed on blogginheads.tv was eternal inflation – the idea, supported by careful calculations in some models, that it is possible that inflation, if it begins in one patch of the universe, gives rise to an infinite expanding space, which produces an infinite number of regions of the universe that look like ours. This provides a very different was to think about the probability for inflation beginning, and seems to provide a possible way around the problem we pointed out. Furthermore, it may provide a way to seek answers to some of the other big questions of the earliest times in the universe – many of which depend on a full understanding of the issue of initial conditions.

I’m sure you’ll be able to find a relevant book if you’re interested in learning more.

So it’s great that Chad Orzel has done a series of short interviews with scientists outside academia, and is gradually blogging the results. It’s a nice little bit of informal sociology of the field, and a useful resource for anyone who might be contemplating such a career path themselves.

Chad, as you probably know, has also written a book that will be coming out later this year. And he’s supposed to be doing scientific research, and keeps up an active blog! How is that possible?

You may have heard that I have a book coming out — pushed back to January, unfortunately. I haven’t shown any hesitation in blogging about substantive questions related to the topic of the book, nor do I see any reason to. And once it comes out I do want to do some sort of book club so that people can ask questions and have a conversation about what’s in the various chapters. So there will be no shortage of book-related stuff here on the blog.

But there is a whole ‘nother level of bookish miscellany — admiring the illustrations, having blurbs come in for the back cover, setting up public talks, and all that. Now we’re pretty much into baby-picture territory; it might not be completely safe to assume that everyone else is as fascinated by all this as I am. But you don’t want to deprive those who are, right? So I’m sending all that stuff here:

• From Eternity to Here Facebook page.

That will shield you from the worst of my enthusiasms. A bit, anyway.

Not that I’m at all sure that this is the right thing to do. Back in my day, we didn’t have all these fancy social networks to play around in; you had your blog, and that was it. Now there’s been a bit of proliferation, and there’s no question that it’s changing the landscape. It can obviously be annoying to try to follow too many things at once, but on the other hand it’s nice to have more appropriate tools for distinct tasks. In the old days, I wouldn’t think much of writing a blog post with an amusing link and little else. Now I will just put that on my Twitter feed. So there are fewer blog posts overall, but the average amount of substance per post is higher. Is this an improvement? Not really sure.

A lot of bloggers have Twitter feeds where they link to every one of their blog posts, which seems backwards to me. (So I usually don’t subscribe to those folks — nothing personal.) I once asked (on Twitter) whether people thought that was a useful service, and I received strong opinions on either side — but then I noticed that everyone who was in favor of linking to every blog post on Twitter was a blogger who linked to every one of their blog posts on Twitter. So I resist. But then again, I synchronize my Twitter feed to my Facebook status updates, which is considered unforgivably gauche in some circles. So who am I to complain?

So — any other ideas? Who should BH.tv have on to talk about science? They need not be bloggers, although that’s always nice. They do need to be realistic — Richard Dawkins or Steven Weinberg would be great, but they have other outlets when they want to reach a wide audience. (Although it wouldn’t hurt to ask, I suppose.) Any suggestions?

Jerry Zucker and his wife Janet Zucker deserve a great deal of credit for turning the idea of the Exchange into a reality. More importantly, for a twelve-year-old such as I was at the time, The Kentucky Fried Movie was a major event in modern cinema. So I was pleased to see that the title of Jerry’s post (”I’d Like to Thank the National Academy”) was the same one that I had used when I gave a talk at the NAS annual meeting. Not that either one of us should be overly proud of that particular line.

Also, he gets away with saying stuff like this:

The really great thing about these scientists is that because their brains are exactly two-and-a-half times the size of the average person’s in the movie business (although in fairness, that also includes talent agents), they are actually more creative and therefore much better at coming up with science-related ideas for movies than our so-called “creative community.” I don’t mean to offend anyone but as much as I loved Slumdog Millionaire, it’s no Viagra. Often, science gets tacked on like wallpaper in a story, but when it’s really integrated into the narrative it can take things in surprising new directions. And thanks to the Exchange and the National Academy of Sciences, research just became much more fun.

That thing about the brain sizes is what they call “creative license.” But it’s deployed in the service of making a good point! Scientists are good at coming up with ideas, and it would be great if a closer relationship between science and Hollywood helped some of those fun ideas percolate into the wider culture. (My giant brain scoffs at giving specifics about how this will actually happen.)

• 3 Quarks Daily has announced a series of four annual prizes, for blog posts in Science, Arts & Literature, Politics, and Philosophy. Science is the first one up, and they’re asking for nominations — the deadline is soon (June 1) so head over there and make suggestions. The final winner will be chosen by a well-known person in the appropriate field; this year’s Science judge will be Stephen Pinker. You are of course welcome to suggest your favorite CV post, because we like the attention. But this would also be a great opportunity to give a boost to that lesser-known blog that you really like and think should get more attention. (There are a lot of good blogs out there.) And if you are someone with a blog, don’t feel shy about nominating a post of your own — most readers don’t keep a mental file of your best posts over the last year.
• The World Science Festival is happening in New York (the U.S.’s second most interesting city) from June 10 to 14. I’ll be there, speaking at two different events. On Friday June 12 there is the WSF Spotlight, which is an informal forum with short talks and a lot of discussion. Participants include Kristin Baldwin (cell biologist), Dominic Johnson (political scientist), Christopher McKay (solar system researcher), and Frank Wilczek (not sure what he does for a living). I believe alcoholic beverages will be available; it’s that kind of event. Then on Saturday June 13 I’ll be on a panel discussing Time Since Einstein, with David Albert, George Ellis, Michael Heller, John Hockenberry, Fotini Markopoulou-Kalamara, and Roger Penrose. (I predict already that insufficient time will be a popular complaint about the time panel.)
• In Second Life, I’m giving a talk tomorrow morning at 10 am Pacific, sponsored by the Meta Institute for Computational Astrophysics. It will be a colloquium-level talk about “Dark Forces,” concentrating on building models of interacting dark matter and dark energy. Second Lifers can beam right there thanks to this elegant and finely-crafted link: http://slurl.com/secondlife/StellaNova/76/200/32.
• Max Brockman (son of John, doyen of Edge) has edited a new collection of essays: What’s Next? Dispatches from the Future of Science. There’s an essay by me in there on “Our Place in an Unnatural Universe.” You should buy it, because it would be like reading a set of interesting blog posts, but on paper. And most of these folks don’t have blogs!