Thermostat

A new podcast! This one is the world-famous* “Thermostat” story, about my apartment broker, Carl Sagan, a pen, and David Bowie.

* My world, anyway.

The Story Collider

It’s been quiet around here.

…

Yep. Quiet.

I’d like to say that’s because I’ve been working on other projects, so it’s lucky for me that I have! I’ve been podcasting. Twice. Even better, another one is about to launch!

Introducing The Story Collider.

I’ve teamed up with Brian Wecht, from Princeton’s Institute for Advanced Study and Ninja Sex Party, to present evening of true stories. Researchers who think about statistical inference 24/7, comedians who haven’t thought about ecology since frog dissections in high school, and everyone in between will tell stories, live on stage, about the times when, for good or ill, science happened.

Our first show is May 13 at The Creek and The Cave in New York City. Check out our website or Facebook page for more info.

Bombs, Cancer, and Mariners

My second podcast is up at 365 Days of Astronomy. This one is darker, if you couldn’t tell from the title.

Broken Teeth and the Fate of the Universe

A new medium! I recorded the 365 Days of Astronomy Podcast for today, in which I describe how a broken tooth leads me to discover that The Universe is more terrifying and more exciting than I had imagined.

In the process of recording I discovered that

1. I love talking.
2. I hate hate hate hate hate hearing my own voice.

I’m also pretty sure those two points describe 99.9% of humanity. I’ll be doing one of these a month, so hopefully I’ll get over point 2, or at least reduce the number of hates. Luckily, the chance of me getting over point 1 is so insignificant as to be not worth thinking about.

Virtual No More

The Large Hadron Collider never felt real.

For several years I was a high-energy particle theorist. I wanted to know how to experimentally test wild questions: Are there tiny curled up extra dimensions? Where do the masses of the elementary particles come from? Which laboratory has the best cafeteria? The answer to all of those was supposedly going to be in Geneva, Switzerland — at CERN where the Large Hadron Collider, the LHC, was being built. The highest energy machine ever! It would answer all our questions! The on-site cafes serve wine!

But it was far away, five years and ten thousand miles when I started grad school, at the Stanford Linear Accelerator Center, in Menlo Park, California. It was sunny, and we had a collider. You can see it stretching away, an impossibly long building, as you drive northbound on I-280, about midway between San Jose and San Francisco. It was spectacularly real, but unfortunately didn’t produce data relevant to the questions I wanted answered.

Like all research groups, the theorists would go as a group to eat lunch in the SLAC cafeteria, where quality was a distinctly relative attribute. The salad bar was a disgrace to Northern California, but the SLAC-burger was passable. The conversation at the table rarely strayed from physics (as long as you count gossip about physicists in that category). The LHC would come often come up, and rarely with good news. The company responsible for the magnets was taking too long, or a failed test meant at least 6 months delay; the already distant collider receding farther away.

Colliders are machines that are built to find particles. There are the familiar ones like electrons and quarks and photons (atoms are made of those three types), but there are many others. New discoveries are generally new particles, or at least can be interpreted that way. Here’s one way it can get fuzzy: if there are tiny, curled up extra dimensions, then it’s possible that particles can spin around in them. But, due to the apparent absurdities of quantum mechanics, the smaller a circle that something spins in, the larger the energy it has to have. Energy is mass, which means particles spinning around an extra dimension are heavy. So what you do is this: you look for a very massive particle that otherwise behaves exactly like one of the particles we already know everything about, like a gluon, and you look for it in a collider. If you find it, you’ve found an extra dimension.

The LHC was a collider that existed for me as a phrase repeated in conversation, a line drawing in a design report, and most often as an option in a computer program. I’d be running my simulations on how to find a gluon spinning around an extra dimension and I’d set a switch in the program. Select collider: 1 for the Tevatron, 2 for the LHC.  We’d do our simulations with option 2 and look at the output and say: “The LHC will be able to find this particular kind of extra dimension”. But that couldn’t be true until the machine was on, so the sentence never carried the excitement it should have. If it was a Wednesday we might get a little more excited, since that was Burrito Day, but mostly there was the feeling of, “Well, now we know that, but it will be years before we can really test it. What’s next?”

The Tevatron felt real. I’d been to Fermilab, in Batavia, Illinois (only a few miles from Geneva, Illinois) and walked the two miles around the ring. Fermilab had the one cafeteria where you could get sushi. It was the sad little rolls in black plastic trays with that dob of wasabi and the tiny puddle of soy sauce, but it was sushi. The experimenters from the Tevatron detectors would often come through the theory offices with printouts of new data and we’d all gather round and fawn over the plots. There were beautiful lines with bumps and error-bars. Each bump is a particle, a part of nature; the ever-shrinking error-bars tracked our increasing certainty that they really were there. But when we selected option 1 the plots always told us the Tevatron wouldn’t be able to see the kinds of extra dimension that we thought might exist. There would be no bumps in their data corresponding to gluons spinning around in extra dimensions. It was real, but not helpful.

A particle has a definite relationship between it’s energy and it’s momentum, and what relates them is its mass. The momentum can point in any direction, but it’s magnitude has to be a particular value, so the allowed momenta form a sphere, or rather a shell, in space — a ‘mass-shell’. Quantum mechanics allows particles to violate this relationship briefly, to not be quite real, their energy and momentum not quite matched. These ‘virtual’ particles are off their mass-shell, or just off-shell. They can’t venture away from the safety of the shell for long. Any virtual particle must soon either fade back into the vacuum or strike another particle in a way that pushes it on-shell.

Clearly, the LHC existed, but far off-shell. Scientists and engineers were spending a tremendous amount of time working on it. It was central to my own research, I thought about it every day in way or another; I made plot after plot of simulated data, and saw hundreds more from other people. We wanted to find extra dimensions! Or Supersymmetry, or anything new. But as the years went on and the delays kept coming it felt like it would always exist in a state of being built, not of actually working. It was a virtual machine, and not finding the right path to its mass-shell.

I left academia a bit over a year ago. I live in New York City, surrounded by spectacularly good restaurants. A couple days ago I woke up and poured myself a bowl of frosted mini-wheats only to find that the LHC had finally succeeded in colliding beams. The machine was functioning. After 25 years of planning and building — 7 years since I learned about it and started my personal wait — it’s on. Yet somehow even that wasn’t enough. That night I had store-bought hummus and crackers for dinner and stared at an event display from the ATLAS experiment, tracing out the paths of the debris from the collision. I wanted to think it was real, but I felt something was missing.

I eat my breakfast standing in the kitchen, reading news on my laptop. This morning I stood there and saw what I was missing. One of the experiments, LHCb, looked for a neutral pion. That’s a very common type of particle. Discovered in 1950, there can be hundreds of them in a single collision. They’re used for calibrating detectors and probing other particles. But the LHC, like all colliders at the energy frontier, has to start at the beginning. It has to show that it can re-discover all the particles that we know before it can find the ones we don’t. I’ve run out of cereal, so all I have this morning is coffee. I’m on my third cup when I find a plot of the search for the neutral pion. It looks just like the ones from the Tevatron. The error bars are big and the bump is a particle we’ve known about for 60 years, but there it is, an on-shell plot from an on-shell machine.

Tonight I’m going to walk a bit farther down the street from the grocery store, skip the cookies and hummus, and get take-out from Caracas, the city’s best arepa restaurant. Maybe I’ll open a bottle of Champagne and toast to the reality of the LHC, or maybe I’ll just smile a little for it and wait for the bumps we haven’t seen before.

What a strange word is multiverse

There is a word for everything that exists, for the sum total of all the atoms, mice, cities, forests, planets, galaxies, and galactic superclusters that exist, have ever existed, or will ever exist. That word is “universe”. It used to be “world”, but then the totality of everything got too big for the world and a new word was needed. It’s possible that a new word is needed again.

The word, if it is indeed needed, is “multiverse”. [1] It sounds like it means multiple totalities of everything, which wouldn’t make any sense. It doesn’t quite mean that; like world before it, the concept of a universe has become too small to contain everything. The world is what contains everything that we encounter, and — for almost all of us — our lives, beginning to end. It is also a ball of rock hurtling through empty space as it orbits the sun. There are other balls of rock hurtling through empty space orbiting the sun. There are even more balls of rock hurtling through space orbiting other suns. A world still contains us, but is too small to contain everything.

Our universe is a collection of stuff — mostly Dark Energy with some Dark Matter and a tiny bit of ‘ordinary’ matter thrown in for seasoning. The latter two are organized into web-like networks of galactic superclusters. There are also photons (light), neutrinos, black holes, and — very, very, very, very occasionally — a human. (There is some overlap in these categories.) In addition to all being in roughly the same place (give or take a few tens of billions of light-years), all of these things obey the same laws of physics.

So once upon a time, we took our previous concept of world and applied it to all the balls of rock flying through space. We did the same thing with “sun”. It was the ball of fire in the sky, the source of light and energy and life for all things. Our sun still is that, but any ball of gas shining through fusion and with planets orbiting it can now also be a sun.

And just like that we can generalize the word universe as a region, or perhaps bubble, of space governed by a particular version of what we call the laws of physics. In other universes the laws might be slightly different — electric charges might attract and repel each other with a strength that is a bit stronger or a bit weaker; or protons might weigh slightly more or spacetime might bend more easily. Or, the laws might be very different. There might be a completely new force; say something like electromagnetism that only acts on electrons and not protons. Each universe would behave slightly, or drastically, different. Most would collapse a tiny fraction of a second after forming. Some will expand so fast galaxies and stars and planets will never have time to form. A tiny few will have the right conditions to support life.

Now, what’s weird is not that we can imagine such universes, but that there is a reasonable way they could all exist, and exist within the same “totality of everything” that we do, separated not by some mystical dimensional barrier, but simply by ordinary space. Incomprehensibly large tracts of space, but ordinary space none-the-less.

This is the crux of the multiverse theory, which has become quite popular recently. Through a string of apparently disconnected theoretical developments this picture of bubble universes spread throughout a much more vast space has gone from pure fantasy to quite conceivably real. (Note the qualifier in the previous sentence. Many of the pieces required by this theory have not been empirically verified.)

[1] I’d nominate “cosmos” in memory of Carl Sagan, but multiverse seems to have won for now.

Non-academic scientists

It sounds like an oxymoron to a lot of academics, but there are a lot of non-academic scientists. In fact, since there are far more degrees awarded than jobs available, then the majority of people with advanced science degrees must work outside of academia.

Over at Uncertain Principles, Chad Orzel has launched the Project for Non-Academic Science, where he’ll be interviewing people with jobs outside the academic rat-race. The first few posts are up, with more coming over the next few weeks.

Quantum unicorns and antimatter

An emotion is running high as around the world physicists are bracing themselves in anticipation of one of the biggest events of the decade. That emotion is dread, and what they’re bracing themselves against is an enormous flux of annoying questions, because the event is the release of the the movie version of Dan Brown’s Angels and Demons.

The worst part is that, no matter how bad the movie is, we’ll have to see it just to understand the questions.

Fortunately for me Luke McKinney has put together a run-down of the problems with the story at The Daily Galaxy.

The fact that antimatter can create huge explosions is accurate, a rarity in Dan Brown novels…The problem is, if your terrorist organisation has a kilogram of antimatter you’re invincible anyway – because you can fly past security checkpoints on your quantum unicorns and hypnotize targets using The Force.

Read the rest to find out how re-evolving dinosaurs fit in.

Two cultures and a bonk

Chirs Mooney and Sheril Kirshenbaum, among others, are organizing a conference on “The Two Cultures in the 21st Century”, in honor of the 50th anniversary of C.P. Snow’s famous lecture of (roughly) the same name. The two cultures in question are the sciences and the humanities. Snow began an exploration of why there is such a gulf in thinking between people with those backgrounds and what the consequences are. That’s not nearly as academic as it looks: poverty and social policy was the example he chose. Today that’s just as much an issue and we can add things like climate change to the list.

The conference should be fascinating, with speakers like E.O. Wilson, Ann Druyan, and Carl Zimmer. I’ll be there, and hopefully live-blogging.

In the meantime, Chris and Sheril are running a couple book readings to prepare. Chris is hosting a discussion of the “Two Cultures” essay itself. Sheril is leading one on Bonk, Mary Roach’s tour through the science of sex. Both should be a lot of fun.

Statistics and doctors

Here’s a paragraph from a recent Scientific American article on the interpretation of statistics:

…only about one out of every 10 women who test positive in screening actually has breast cancer. The other nine are falsely alarmed. Prior to training, most (60 percent) of the gynecologists answered 90 percent or 81 percent [chance that the woman actually has cancer], thus grossly overestimating the probability of cancer. Only 21 percent of physicians picked the best answer—one out of 10.

The context here is false positives; the chance that the test will indicate a problem even if there is no cancer. The false positive rate is small, but since mammograms are recommended as a routine screen there are vastly more healthy patients getting them than ones with cancer. The result is that even with a positive test, there’s only a 1 in 10 chance that the patient has cancer. (Which is, of course, why further tests are done at that point.) The same reasoning applies to any screening procedure.

Now for the scary part: read that paragraph again. It’s not just that only 21% of physicians could pick out the right answer; these were gynecologists being asked about one of the most common tests they perform. The fact that statistics are badly understood is routine, but professionals misunderstanding one of the central statistics of their discipline is both surprising and horrifying.

The authors of the Scientific American article advocate a different way of presenting the statistics. So instead of saying “1% of women have breast cancer”, they would recommend “10 out of every 1000 women have breast cancer”. This apparently had good results.

After learning to translate conditional probabilities into natural frequencies, 87 percent of the gynecologists understood that one in 10 is the best answer.

I’m not sure if I should be happy about this, or incredibly sad that 13% still couldn’t.