Couldn’t resist posting this photograph of the crescent Venus snuggling up to the crescent Moon. Taken by Ivan Eder, Budapest; posted on Facebook by Stars and Constellations; pointed to by Nick Suntzeff. (Update: Peter Simpkin points out that the original can be found here.)
Remember Pluto, erstwhile member of the Sun’s retinue of planets? For an object that lacks the dynamical oomph to have cleared its neighborhood, this little dwarf planet sure has accrued an impressive number of satellites. Five of them have been discovered to date, but only three — Charon, Hydra, and Nix — have been given names. The others, laboring under the uninspiring temporary designations P4 and P5, have yet to undergo their official naming ceremonies. So this is your chance to weigh in!
Not officially, of course. The Nomenclature Working Groups of the International Astronomical Union are unlikely to hand the keys to the Solar System over to the unwashed masses, just so they can end up with celestial objects named “Gaga” and “The Situation.” But they will be consulting with the Hubble Space Telescope discovery team, led by Mark Showalter of the SETI institute. And Showalter has thrown the question open to public input (via 80beats). He is asking folks to vote on a variety of possible names, all drawn from underworld mythology. Your vote won’t be binding on anyone, but who knows? If Alecto storms to the lead, the IAU might just decide that a “hideous, snake-haired monster” is just what the Solar System needs.
Help Populate the (Solar System’s) Underworld Read More »
This new video has been bouncing around the blogs and Twitter feeds I read: excerpts from internal (i.e., non-public) talks at the CMS collaboration, as they revealed to themselves the new Higgs results from this summer. When you started hearing rumors last June, it was from these meetings that they emerged.
First we see two talks at internal collaboration meetings, by Mingming Yang on June 15 and by Andre David on June 28, then some of Joe Incandela’s public announcement on July 4 (along with Fabiola Gianotti’s talk about the ATLAS results, of course). In the first talk the significance was poking past four sigma, but not yet reaching five sigma, which took a bit more work (and data).
You might expect a lot of whooping and hollering on the part of the experimenters as they see how good their data is, but for the most part they are pretty quiet. It’s not because they don’t recognize the importance of the moment — it’s because their brains are working at full capacity, taking in the information on the slides and trying to understand exactly what it means.
The first talk is advertised as “unblinding,” when they first look at the results that they have intentionally hidden from themselves to prevent cheating. That seems like a tiny exaggeration, unless they’ve written a script that takes the data, turns it into a pretty plot, and uploads and captions that plot on a PowerPoint slide without any human being seeing it. (I suppose it’s possible…) But this is when most of the collaboration first heard the news, which is an historic moment by any measure.
Unblinding the Higgs Read More »
I’m currently working hard to finish a paper on the Everett (Many-Worlds) approach to quantum mechanics, collaborating with Charles (“Chip”) Sebens from the University of Michigan. It’s an area that lies at the intersection of “foundations of quantum mechanics” and “philosophy of physics,” and neither of those is really my expertise — but I’m trying to learn! More when the paper comes out, hopefully quite soon.
Meanwhile, I end up posting a lot of videos rather than really blogging, until the larger crush of work is lifted a bit. While I was in Nottingham I had the pleasure of sitting down to record for their series of Sixty Symbols videos, which is a terrific series that I’m happy to recommend. Here’s me chatting about the different approaches to quantum mechanics.
Forthcoming: me chatting about the Higgs boson, and me chatting about the arrow of time. My time in England involved a lot of chatting, it’s true.
Sixty Symbols on Quantum Mechanics Read More »
A highlight of my recently-completed visit to England was the honor of giving a public lecture at the Royal Institution of Great Britain in London. It’s an honor to give public talks anywhere, of course — I always enjoy seeing people who are not professional scientists nevertheless decide that the best way they can spend a Tuesday evening is to hear a physicist lecture about the Higgs boson and the Large Hadron Collider. But the RI is special. Its leadership in bringing science to a wide audience dates back to 1825, when Michael Faraday inaugurated the famous Christmas Lectures. The lecture hall where I was speaking is the same one where Faraday spoke, happily with more comfortable seats and better audio-visual equipment. The connection was especially appropriate, as the hidden message (not so hidden by the end, really) of my talk was that we need to think about the world in terms of fields rather than particles, and it was Faraday who introduced the concept of an electric field.
Sadly, almost as soon as I left the RI announced that it is in serious financial difficulty. (I don’t think it was my fault — we had a nearly-full house for the lecture.) Their historic building in the tony Mayfair district of London, where the popularity of their events in the nineteenth century led Albemarle Street to become the first one-way street in the city, is now up for sale. Scientists and science lovers are in an uproar, and hope to save the RI building from being sold to an unsympathetic landlord, but it’s unclear whether that’s a feasible scenario. While it’s true that there are many more outlets for good science communication now than in Faraday’s time (I’m sure he would have been an enthusiastic blogger, but the technology wasn’t quite ready yet), it would certainly be a shame to lose or substantially alter such an historic and effective institution.
For the curious, here is the talk I actually gave, complete with location-specific jokes.
The audience Q&A, a lively discussion moderated by Alok Jha, was recorded separately.
And for the impatient, here is a much more brief (7 minutes) interview that I did just ahead of time.
Standing in Faraday’s Shoes Read More »
Scientists don’t always agree with each other. Yes, I know; shocking but true. In cases of collegial disagreement, it’s often fun to quantify the extent of opinion by gathering a collection of experts and taking a poll. Inevitably some killjoy will loudly grumble that “scientific questions aren’t decided by voting!”, but that misses the point. A poll of scientists isn’t meant to decide questions, it’s meant to collect data — mapping out the territory of opinion among people who have spent time and effort thinking carefully about the relevant questions.
There’s been a bit of attention given recently to one such poll, carried out by Maximilian Schlosshauer, Johannes Kofler, and Anton Zeilinger at a quantum foundations meeting (see John Preskill at Quantum Frontiers, Swans on Tea). The pollsters asked a variety of questions, many frustratingly vague, which were patiently answered by the 33 participants.
This plot gives the money shot, as they say in Hollywood:
It’s a histogram of the audience’s “favorite” interpretation of quantum mechanics. As we see, among this expert collection of physicists, philosophers, and mathematicians, there is not much of a consensus. A 42% percent plurality votes for the “Copenhagen” interpretation, while the others are scattered over a handful of alternatives.
I’ll go out on a limb to suggest that the results of this poll should be very embarrassing to physicists. Not, I hasten to add, because Copenhagen came in first, although that’s also a perspective I might want to defend (I think Copenhagen is completely ill-defined, and shouldn’t be the favorite anything of any thoughtful person). The embarrassing thing is that we don’t have agreement.
Think about it — quantum mechanics has been around since the 1920’s at least, in a fairly settled form. John von Neumann laid out the mathematical structure in 1932. Subsequently, quantum mechanics has become the most important and best-tested part of modern physics. Without it, nothing makes sense. Every student who gets a degree in physics is supposed to learn QM above all else. There are a variety of experimental probes, all of which confirm the theory to spectacular precision.
And yet — we don’t understand it. Embarrassing. To all of us, as a field (not excepting myself).
I’m sitting in a bistro at the University of Nottingham, where I gave a talk yesterday about quantum mechanics. I put it this way: here in 2013, we don’t really know whether objective “wave function collapse” is part of reality (as the poll above demonstrates). We also don’t know whether, for example, supersymmetry is part of reality. Wave function collapse has been a looming problem for much longer, and is of much wider applicability, than the existence of supersymmetry. Yet the effort that is put into investigating the two questions is extremely disproportionate.
Not that we should be spending as much money trying to pinpoint a correct understanding of quantum mechanics as we do looking for supersymmetry, of course. The appropriate tools are very different. We won’t know whether supersymmetry is real without performing very costly experiments. For quantum mechanics, by contrast, all we really have to do (most people believe) is think about it in the right way. No elaborate experiments necessarily required (although they could help nudge us in the right direction, no doubt about that). But if anything, that makes the embarrassment more acute. All we have to do is wrap our brains around the issue, and yet we’ve failed to do so.
I’m optimistic that we will, however. And I suspect it will take a lot fewer than another eighty years. The advance of experimental techniques that push the quantum/classical boundary is forcing people to take these issues more seriously. I’d like to believe that in the 21st century we’ll finally develop a convincing and believable understanding of the greatest triumph of 20th-century physics.
The Most Embarrassing Graph in Modern Physics Read More »
Longtime readers know I feel strongly that it should be more widely appreciated that the laws underlying the physics of everyday life are completely understood. (If you need more convincing: here, here, here.) For purposes of one of my talks next week in Oxford, I thought it would be useful to actually summarize those laws on a slide. Here’s the most compact way I could think to do it, while retaining some useful information. (As Feynman has pointed out, every equation in the world can be written U=0, for some definition of U — but it might not be useful.) Click to embiggen.
This is the amplitude to undergo a transition from one configuration to another in the path-integral formalism of quantum mechanics, within the framework of quantum field theory, with field content and dynamics described by general relativity (for gravity) and the Standard Model of particle physics (for everything else). The notations in red are just meant to be suggestive, don’t take them too seriously. But we see all the parts of known microscopic physics there — all the particles and forces. (We don’t understand the full theory of quantum gravity, but we understand it perfectly well at the everyday level. An ultraviolet cutoff fixes problems with renormalization.) No experiment ever done here on Earth has contradicted this model.
Obviously, observations of the rest of the universe, in particular those that imply the existence of dark matter, can’t be accounted for in this model. Equally obviously, there’s plenty we don’t know about physics beyond the everyday, e.g. at the origin of the universe. Most blindingly obvious of all, the fact that we know the underlying microphysics doesn’t say anything at all about our knowledge of all the complex collective phenomena of macroscopic reality, so please don’t be the tiresome person who complains that I’m suggesting otherwise.
As physics advances forward, we will add to our understanding. This simple equation, however, will continue to be accurate in the everyday realm. It’s not like the Steady State cosmology or the plum-pudding model of the atom or the Ptolemaic solar system, which were simply incorrect and have been replaced. This theory is correct in its domain of applicability. It’s one of the proudest intellectual accomplishments we human beings can boast of.
Many people resist the implication that this theory is good enough to account for the physics underlying phenomena such as life, or consciousness. They could, in principle, be right, of course; but the only way that could happen is if our understanding of quantum field theory is completely wrong. When deciding between “life and the brain are complicated and I don’t understand them yet, but if we work harder I think we can do it” and “I understand consciousness well enough to conclude that it can’t possibly be explained within known physics,” it’s an easy choice for me.
Let me know if I’ve made any typos here, or have gone too far in trying to make things compact. For instance, can I get away without putting a “trace” around the gauge field kinetic term? I don’t want a notational shortcut to undermine my argument and leave the audience believing in God.
The World of Everyday Experience, In One Equation Read More »
Cara Santa Maria, science correspondent for the Huffington Post, does a series of videos there called Talk Nerdy To Me. See Martin Savage on physics and the simulation argument, Mark Jackson on cosmology and string theory, Mark’s PhD advisor Brian Greene on the multiverse, or a collection of interviews about Alan Turing.
The latest one features me talking about the arrow of time. Likely nothing you haven’t heard before, but it’s only five minutes! Could be a useful explainer for your friends who don’t understand why you keep mumbling about entropy under your breath. (People do that, right?)
Talking Nerdy About Time Read More »
Regulars from Cosmic Variance will be well acquainted with the idea of “firewalls” around black holes, from reading Joe Polchinski’s guest post on the subject. And then you heard more about them from John Preskill’s post at Quantum Frontiers. Or maybe George Musser’s post at Scientific American. Long story short: there is a believable claim on the market that, if you believe that information is preserved in the evaporation of black holes via Hawking radiation, an infalling observer should be incinerated by a wall of high-energy radiation when they cross the event horizon, in dramatic contradiction to everything classical general relativity would lead you to believe. Important stuff, if true. (“True” might mean “the argument is valid but one of the underlying assumptions is wrong, therefore teaching us something important about quantum gravity.)
Word is now finally leaking out into the more popular press, courtesy of my lovely wife Jennifer Ouellette’s article at Simons Science News, a new initiative from the Simons Foundation. It’s a great article, which I would say even if we were not notoriously nepotistic back-scratchers.
Here’s my attempt to squeeze the firewall argument down to its essence, for people who know a little quantum mechanics. If information escapes from a black hole, the radiation emitted at late times must share quantum entanglement with radiation that escaped at early times, in order to describe a pure quantum state (from which the black hole presumably formed). At the same time, to an observer near the event horizon, the local conditions are supposed to look almost like empty space — the quantum vacuum. But within that vacuum are virtual particles, some of which will eventually escape in the form of radiation and some of which will eventually fall into the black hole. In order for the state near the horizon to look like the vacuum, that outgoing radiation and the ingoing radiation must also be entangled. Therefore, it appears that the outgoing radiation is both entangled with the ingoing radiation, and with the radiation that escaped at earlier times. But that’s impossible; quantum mechanics won’t let degrees of freedom be separately (maximally) entangled with two different other sets of degrees of freedom. Entanglement is monogamous. A simple — but unpalatable — way out is to suggest that the state near the horizon is not a quiet state of maximal entanglement, but a noisy thermal state of high-energy radiation — a firewall.
It’s a slightly tricky business, as you expect it to be when we’re mixing up quantum mechanics with things happening in spacetime, in the absence of a once-and-for-all theory of quantum gravity. Probably most people who have thought about the issue don’t believe firewalls really exist (although some do), but in that either there’s a secret flaw in the argument, or one of our fundamental assumptions is out of whack. Maybe information is not conserved, or maybe it’s transferred faster than light, or maybe quantum mechanics doesn’t work quite the way we thought. The story should continue to be interesting no matter what happens.
Here’s the video from a talk I gave at Skepticon V last month. It’s basically a superposition of a Higgs-boson talk with the From Particles to People talk. How is such a feat even possible, you may ask? Well, it wasn’t easy.
Fortunately, this talk is only 50 minutes long; it’s not like sitting through 15 hours of Moving Naturalism Forward videos.
This is the talk, by the way, from which the little picture of me at the top right corner of the blog was taken. I like it because it appears that I am looking at each new blog post with skeptical bemusement.
Also, at one point I said “light years” when I meant “miles” (talking about Voyager). They may take my scientist card away for that one.
The Higgs Boson and the Meaning of Life Read More »