Sorry, I have no idea how to build a cloud chamber, I’m just a theorist. But Samatha here can help you out (and be much more charming than I would be in the process).
How to Build a Cloud Chamber to Detect Cosmic Rays Read More »
Last week I had the pleasure of giving a seminar to the philosophy department at the University of North Carolina. Ordinarily I would have talked about the only really philosophical work I’ve done recently (or arguably ever), deriving the Born Rule in the Everett approach to quantum mechanics. But in this case I had just talked about that stuff the day before, at a gathering of local philosophers of science.
So instead I decided to use the opportunity to get some feedback on another idea I had been thinking about — our old friend, the claim that The Laws of Physics Underlying Everyday Life Are Completely Understood (also here, here). In particular, given that I was looking for feedback from a group of people that had expertise in philosophical matters, I homed in on the idea that quantum field theory has a unique property among physical theories: any successful QFT tells us very specifically what its domain of applicability is, allowing us to distinguish the regime where it should be accurate from the regime where we can’t make predictions.
The talk wasn’t recorded, but here are the slides. I recycled a couple of ones from previous talks, but mostly these were constructed from scratch.
The punchline of the talk was summarized in this diagram, showing different regimes of phenomena and the arrows indicating what they depend on:
There are really two arguments going on here, indicated by the red arrows with crosses through them. These two arrows, I claim, don’t exist. The physics of everyday life is not affected by dark matter or any new particles or forces, and its only dependence on the deeper level of fundamental physics (whether it be string theory or whatever) is through the intermediary of what Frank Wilczek has dubbed “The Core Theory” — the Standard Model plus general relativity. The first argument (no new important particles or forces) relies on basic features of quantum field theory, like crossing symmetry and the small number of species that go into making up ordinary matter. The second argument is more subtle, relying on the idea of effective field theory.
So how did it go over? I think people were properly skeptical and challenging, but for the most part they got the point, and thought it was interesting. (Anyone who was in the audience is welcome to chime in and correct me if that’s a misimpression.) Mostly, since this was a talk to philosophers rather than physicists, I spent my time doing a pedagogical introduction to quantum field theory, rather than diving directly into any contentious claims about it — and learning something new is always a good thing.
Quantum Field Theory and the Limits of Knowledge Read More »
I was very pleased to learn that I’m among this year’s recipients of a Guggenheim Fellowship. The Fellowships are mid-career awards, meant “to further the development of scholars and artists by assisting them to engage in research in any field of knowledge and creation in any of the arts, under the freest possible conditions and irrespective of race, color, or creed.” This year 173 Fellowships were awarded, chosen from 3,100 applications. About half of the winners are in the creative arts, and the majority of those remaining are in the humanities and social sciences, leaving eighteen slots for natural scientists. Only two physicists were chosen, so it’s up to Philip Phillips and me to uphold the honor of our discipline.
The Guggenheim application includes a “Career Narrative” as well as a separate research proposal. I don’t like to share my research proposals around, mostly because I’m a theoretical physicist and what I actually end up doing rarely bears much resemblance to what I had previously planned to do. But I thought I could post my career narrative, if only on the chance that it might be useful to future fellowship applicants (or young students embarking on their own research careers). Be warned that it’s more personal than most things I write on the blog here, not to mention that it’s beastly long. Also, keep in mind that the purpose of the document was to convince people to give me money — as such, it falls pretty heavily on the side of grandiosity and self-justification. Be assured that in real life I remain meek and humble.
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A Personal Narrative Read More »
Now that we’ve figured out the existence of God and the reality of time, let’s get down to the important issues: please stop putting aioli on hot dogs.
Recently, a casual restaurant called the Dog Haus opened right on the street I drive down on my way to and from work. It’s a pretty simple concept: fancy hot dogs and sausages. As restaurant concepts go, this is right in my wheelhouse, combining two things I love very much: (1) fanciness, and (2) hot dogs. I am precisely the target audience for this establishment. I would not be surprised if some marketer had shown a picture of me in his PowerPoint presentation to the Dog Haus board meeting at one point.
However, upon actually eating at the Dog Haus a couple of times, my overall impression was one of grave disappointment. I had sampled a couple of their suggested special items — things like “Das Brat,” which comes with bratwurst, whole grain mustard aioli, white american cheese, caramelized onions, and sauerkraut. In each case, the offering came across as too bland and goopy to really qualify as anything special. I have had hot dogs at baseball stadiums that brought me greater pleasure.
But I persevered, out of a conviction that I should like this kind of place. Finally I decided to forgo the suggested menu offerings and just get a plain dog and put on the condiments myself.
It was heavenly. Spicy, crisp, lively, and served on an amazing Hawaiian bread bun. The hot dog I had been waiting for all my life.
It took me a while, but I eventually sussed out why I could take the Dog Haus raw ingredients and create something special, but was turned off by all of their pre-suggested menu items. Namely: the suggestions they put forward were far too likely to feature an innocent sausage drowned in “aioli.”
It’s not just the Dog Haus. I’ve been to a disturbing number of upscale burger joints that seem to think that aioli is what one puts on cheeseburgers. (Not to mention “brioche buns” — don’t get me started.)
It is not. Traditionally, on burgers one puts ketchup, and on hot dogs and sausages one puts mustard, in addition to whatever other creative accoutrements one is inspired to add. But not aioli, a garlicky kind of mayonnaise meant for eggs or fish or something else light and delicate.
I am here to inform the gourmet chefs of the world that hot dogs and hamburgers are not light and delicate foodstuffs. They are robust, coarse, energetic foods, and they require condiments that can stand up to the challenge. Something with a kick, with some life in it — not a greasy white emulsion of oil globules.
It’s not hard to see why such an obvious mistake is being made. You want to brand your dogs and burgers — traditionally classified as simple peasant fare — as something upscale and sophisticated. Mustard and ketchup are the antithesis of upscale sophistication, so you peer into your list of French condiments and see what comes up. (Whatever appears first in alphabetical order, apparently.)
The solution is equally obvious: better-quality mustard and ketchup. The Dog Haus even has such things, which explains why it’s not hard to build a memorable dog all by yourself, if you don’t make the mistake of letting them do it for you.
I will close with a picture of Joël Robuchon, one of the greatest chefs of our age, eating at In-And-Out Burger. I bet he was sad that “animal-style” burgers involve Thousand Island dressing.
The idea that time isn’t “real” is an ancient one — if we’re allowed to refer to things as “ancient” under the supposition that time isn’t real. You will recall the humorous debate we had at our Setting Time Aright conference a few years ago, in which Julian Barbour (the world’s most famous living exponent of the view that time isn’t real) and Tim Maudlin (who believes strongly that time is real, and central) were game enough to argue each other’s position, rather than their own. Confusingly, they were both quite convincing.
The subject has come up once again with two new books by Lee Smolin: Time Reborn, all by himself, and The Singular Universe and the Reality of Time, with philosopher Roberto Mangabeira Unger. This new attention prompted me to write a short essay for Smithsonian magazine, laying out the different possibilities.
Personally I think that the whole issue is being framed in a slightly misleading way. (Indeed, this mistaken framing caused me to believe at first that Lee and I were in agreement, until his book actually came out.) The stance of Maudlin and Smolin and others isn’t merely that time is “real,” in the sense that it exists and plays a useful role in how we talk about the world. They want to say something more: that the passage of time is real. That is, that time is more than simply a label on different moments in the history of the universe, all of which are independently pretty much equal. They want to attribute “reality” to the idea of the universe coming into being, moment by moment.
Such a picture — corresponding roughly to the “possibilism” option in the picture above, although I won’t vouch that any of these people would describe their own views that way — is to be contrasted with the “eternalist” picture of the universe that has been growing in popularity ever since Laplace introduced his Demon. This is the view, in the eyes of many, that is straightforwardly suggested by our best understanding of the laws of physics, which don’t seem to play favorites among different moments of time.
According to eternalism, the apparent “flow” of time from past to future is indeed an illusion, even if the time coordinate in our equations is perfectly real. There is an apparent asymmetry between the past and future (many such asymmetries, really), but that can be traced to the simple fact that the entropy of the universe was very low near the Big Bang — the Past Hypothesis. That’s an empirical feature of the configuration of stuff in the universe, not a defining property of the nature of time itself.
Personally, I find the eternalist block-universe view to be perfectly acceptable, so I think that these folks are working hard to tackle a problem that has already been solved. There are more than enough problems that haven’t been solved to occupy my life for the rest of its natural span of time (as it were), so I’m going to concentrate on those. But who knows? If someone could follow this trail and be led to a truly revolutionary and successful picture of how the universe works, that would be pretty awesome.
The Reality of Time Read More »