Author: Sean Carroll

A couple of the many couples getting married in Massachusetts today (Associated Press photos). Julie and Hillary Goodridge, lead plaintiffs in the case to allow same-sex couples to marry, getting their marriage license:

John Mirthes and Rick Reynolds chat with volunteer Sian Robertson as they wait to file their intent to marry:

I’m told that scenes like this are going to be the end of civilization as we know it. But with all the other images we’ve been seeing in the news lately, these made me feel good.

(Related: Career choices explained.)

Josh Marshall has an excerpt from a Washington Times excerpt from Bill Sammon’s new book, Misunderestimated: The President Battles Terrorism, John Kerry and the Bush Haters. Here is my own excerpt of Josh’s excerpt:

“I get the newspapers — the New York Times, The Washington Times, The Washington Post and USA Today — those are the four papers delivered,” he said. “I can scan a front page, and if there is a particular story of interest, I’ll skim it.”

…

“He does not dwell on the newspaper, but he reads the sports page every day,” Mr. Card said with a chuckle.

…

Mr. Bush thinks that immersing himself in voluminous, mostly liberal-leaning news coverage might cloud his thinking and even hinder his efforts to remain an optimistic leader.

Remember, this is a pro-Bush book, reprinted in a pro-Bush newspaper.

You want to know why liberals are really so angry? You can’t parody this guy! His reality exceeds our best attempts at humorous exaggeration.

I missed poem on your blog day. Here’s a belated entry by Kate Ryan, recent winner of the Ruth Lilly Prize.

THE OTHER SHOE

Oh if it were

only the other

shoe hanging

in space before

joining its mate.

If the undropped

didn’t congregate

with the undropped.

But nothing can

stop the mid-air

collusion of the

unpaired above us

acquiring density

and weight. We

feel it accumulate.

… here at the new & improved blogspot. At first it wouldn’t let me publish my last post, and now it’s repeating it over and over. Hopefully we’ll return to normal soon.

Some reactions to my list of misconceptions about cosmology. Chad Orzel at Uncertain Principles has misconceptions about quantum mechanics and thermodynamics. It’s a very good list, even if he does say that vacuum energy is useless. It’s useless in the sense that it cannot be made to do thermodynamic work (because the vacuum energy is spread absolutely uniformly), but in another sense it’s quite useful: it makes the universe accelerate, thereby giving cosmologists something deep to think about. (And occasionally get them a job.)

Chris C Mooney notes that a planetarium show at the Smithsonian doesn’t even mention the Big Bang, although it’s supposed to be a tour of the universe. So perhaps one of the sources of misconceptions is that we aren’t clear enough about what we actually do think people need to know? Right off the top of my head, here are some facts about cosmology I think every educated person should know:

• The universe is big. The Sun is a star, located in a galaxy with about a trillion other stars. There are a lot of other galaxies in the observable universe (about 100 billion), distributed evenly on large scales.
  

• It’s getting bigger. Very distant galaxies are moving away from each other.
  

• It’s old. If we trace the expansion backwards in time, everything crunches together about 14 billion years ago, at what we call the “Big Bang.”
  

• We don’t know how it started. The Big Bang itself lies outside our current understanding, although we do understand things very well at a time only about 1 second after the Bang. During or before that first second, we have good ideas but no direct empirical constraints.
  

• It’s dark and mysterious. Only five percent of our universe is “ordinary” matter; about 25% is some dark matter particle we haven’t yet discovered in the lab, and about 70% is a smoothly-distributed and nearly-unchanging dark energy.
  

• We don’t know how it will end. To predict the future would require a better understanding of what the dark energy is and how it will behave in the future. This is one of the things we’re trying to understand.

That’s not so many, for such a big universe. How do we get these into high school curricula?

We are happy to report that this blog is the first page to come up in a Google search for preposterous. Out of 275,000 pages, that’s not too shabby.

Sometimes you have to love NASA. It’s the only organization I know of (although I’m sure there are countless others) that measures the success of its research programs by how many column inches are devoted to them in newspapers worldwide. As a byproduct, they’ve become very good at getting out their message in interesting ways.

This is by way of prelude to describing what I received in my mailbox yesterday: a WMAP beach ball (pictured at right). WMAP is the Wilkinson Microwave Background Anisotropy Probe, a satellite that has measured the tiny temperature fluctuations in the cosmic microwave background to unprecedented precision. The statistical properties of these fluctuations depend in interesting ways on the parameters describing our universe (such as the amount of dark matter and dark energy, or the overall geometry of space), so the WMAP results have provided a treasure trove of information for cosmologists. The cosmic microwave background radiation provides a picture of the universe when it first became transparent, at an age of about 379,000 years; it’s kind of amazing we can extrapolate our current theories back that far and come even close to the right answer, much less get things spot-on.

The beach ball is a playful public-relations gimmick, which I’m all in favor of. Other types of scientists could learn a lot about outreach from these folks.

I notice that I’m actually writing much less about politics in this blog than I originally expected to. Part of that is because there are few things I have to say that aren’t already being said more eloquently in some other blog. Another part is that the situation right now is so depressing and outrageous on multiple levels that there’s an overwhelming temptation to forget about light and just throw heat.

So instead you will get some warmed-over cosmology. In particular, I was asked a while back to come up with a list of “most prevalent misconceptions about cosmology.” I’m not sure among whom they should be prevalent; some of my colleagues have way-out ideas, but I’m not going to go about setting them all straight. Anyway, here was my suggested list of misconceptions. Comments welcome as to more misconceptions, although they have to be arguably prevalent — not just your own personal misconceptions, we could be here a long time.

• The universe is unchanging and infinitely old, or very young (thousands of years).
  These are basic misconceptions, but I think that most people actually don’t have them. At least, not the people who might be reading this list. The universe is about 14 billion years old. At least, that’s the time between the Big Bang and today.
• The Big Bang model is controversial, or inflation is an alternative.
  The BB model is completely accepted by the community. Inflation and other ideas extend the model, but the basic BB picture is secure. Three pillars of the model — the expansion of the universe, the cosmic microwave background, and primordial nucleosynthesis — make it hard to imagine any credible alternative. The idea of inflation in the early universe is an add-on to the Big Bang, not a replacement for it.
• The Big Bang is an explosion at a point in a pre-existing space.
  It’s not; all of space comes into existence at the BB.
• The universe has a center, or an edge, or something it is expanding into.
  The universe isn’t expanding into anything else, and as far as we know it’s quite homogeneous. Of course there is a point past which we can’t directly see, so we can’t say what goes on beyond there.
• The universe is expanding faster than the speed of light, or perhaps it used to be, and this seems to conflict with relativity.
  The expansion of the universe is not a “speed”, so this doesn’t even make sense. We associate a speed to distant galaxies, but that’s only an informal idea which works if they’re not too far away. The apparent recession velocity of very distant galaxies can be greater than the speed of light, but that doesn’t violate relativity, which only puts an upper limit on the relative velocity of two objects passing by each other.
• Cosmologists used to believe in dark matter, and now in dark energy, and how do they know there isn’t even more stuff out there?
  We believe in both dark matter and dark energy; the former seems to be made of particles that collect in galaxies and clusters, while the latter is evenly spread throughout space. The curvature of space puts limits on the total amount of energy, so we probably won’t discover important new components.
• Dark matter is just ordinary matter that we haven’t found yet.
  Evidence from both the cosmic microwave background and primordial nucleosynthesis gives tight bounds on how much ordinary matter there is. We compare this to the total amount inferred from gravitational effects, and come up well short. The dark matter must be some new kind of particle, not yet discovered in the lab.
• Scientists keep inventing new phenomena like dark matter and dark energy because they are desperate, or philosophically hidebound; these are just like epicycles or the aether, and will eventually go away.
  Well, maybe. But it’s important to emphasize that we have been forced into these ideas by the need to explain observational data, they’re not just cool ideas we’ve fallen for. The more data we to get, the more secure these ideas seem to become. Of course it’s possible we’re missing something big, but if so everyone would love to come up with the compelling alternative; there is no establishmentarian conspiracy to suppress other ideas.

Remember, these are misconceptions. I hope nobody reads the list without the preamble and thinks these are the “greatest discoveries of modern physics” or some such thing.

Any physicist knows the most common responses when you first tell someone what you do for a living — “I hated physics in high school” being the consensus pick for number one. Which is not inconsistent with the fact that people are fascinated by the actual physics that we do, whether it’s studying dark energy or the physics of crumpling paper. Our education system, for whatever reasons, tends to scare people away from science more than it draws them in.

Which is why the work of Project Exploration is so wonderful. Founded and run by Paul Sereno and Gabrielle Lyon, PE works to get children (especially girls and inner-city kids) interested in science by using one of the greatest draws we have: dinosaurs. Paul is an celebrated paleontologist who is our best living approximation to Indiana Jones; his wife Gabe is a professional educator who is really the soul of PE. In the short time they’ve been in operation, they’ve already made a tangible difference in a lot of people’s lives; as just one measure, almost all of the children who work with PE end up going to college, while it’s a good bet that almost none of them would have if it hadn’t been for the project.

Their latest brilliant idea is to display dinosaurs in a good approximation of their natural habitat — the Giants exhibition shows fossils and exhibits amidst the plant life at the Garfield Park Conservatory. It’s an impressive exhibit, very worth checking out if your’re in Chicago. I visited Saturday night for the Fourth Annual Dinosaur Dinner, a gala benefit for PE. It was great fun, including a benefit auction of items like a dinosaur-femur bench and a dinner with Paul and Gabe. (This is my new standard for success in life: when I can auction off dinner with myself in a reasonable expectation that someone other than my Mom would bid for it.)

Gabe is interested in expanding the purview of Project Exploration to include other types of science. We both think it would be fun next year to have a Dark Energy Dinner, where everyone comes dressed in black. Watch this space for updates to see if it will come to pass.

The other celebrity I got to meet at the dinner was Barak Obama, our Democratic nominee for US Senate from Illinois. In a thirty-second conversation, he came off as extremely intelligent and engaging (which is his job, I suppose). I mentioned that I had endorsed him on my blog, and he was curious about the blogging process — how much time it took, etc. It’s about time we get someone in government who has a UofC affiliation but is not a crazy neoconservative, so I’m rooting hard for him.

Nature has a feature known as “concepts essays,” in which they ask highly respected (or at least “willing”) scientists to write short reflective pieces about specific concept of importance to their field. The idea is to go slightly beyond a standard pedagogical introduction to a subject and allow for the kind of discussions that scientists might have around coffee but would never put into a journal article. (I.e. it’s an old-media version of a blog.)

I was invited to write such an essay about dark matter, which has now appeared. (That’s a pdf version on my site; there is an html version on the Nature site, but it’s not as pretty and might require registration.) I couldn’t help but mention dark energy as well, so in the final version the “concept” includes both dark matter and dark energy. (Here’s a very short intro to both subjects.)

The idiosyncratic angle I chose to take was to ask how interesting the dark sector could be — in particular, whether there could be interactions between dark matter particles (or dark matter and ordinary matter, or dark matter and dark energy) that might allow some sort of structures to form, even intelligent life. We might ask, for example, whether there could be some weakly-coupled massless abelian gauge boson that mediates interactions between dark matter particles: “dark light.”

As I say in the article, probably not. We don’t know as much as we would like about the distribution of dark matter, but we do know something, and it appears to be much more smoothly distributed than the ordinary matter in the universe. See for example this computer reconstruction of the dark matter density in a cluster of galaxies, using gravitational lensing. The simple explanation for this smoothness is that dark matter is probably collisionless. When atoms of ordinary matter bump together, they can emit light and cool, and this dissipation process allows the ordinary stuff to condense into the center of galaxies. But the interactions that give rise to dissipation are exactly those necessary for making structures and life. Of course, all we have are upper limits; it’s still possible that there is life out there in the dark matter, but characterized by much larger sizes and much longer timescales than anything in our experience. Perhaps a dark heartbeat takes millions of years to complete.

Now I am wondering whether the goofy illustration chosen by the editors to accompany the article (shown above) might feature the most dramatic decolletage ever to appear in a major scientific journal. Anyone have any other candidates?