Science

Snowmass Young Physicists Survey

Modern experimental particle physics is a high-budget, long-time-scale operation, which requires a great deal of planning. Fortunately there is a process in place, dubbed Snowmass after the scenic location in Colorado where meetings were traditionally held. (Funding agencies subsequently decided that it was unseemly for scientists to hold meetings in places that sound like vacation resorts, so this year “Snowmass” is in Minneapolis.)

Any field depends on the engagement and interest of its younger members, so it’s great to know there is a Snowmass Young Physicist Movement. And if you’re a young high-energy physicist, they would like your input. Below is the message from organizer Marcelle Soares-Santos, but the short version is that they’re asking people to complete this brief survey. Every bit of information helps.

Dear all,

The Snowmass process which is ongoing through this summer encompasses a series of studies carried out by the high energy physics community with the goal to establish a coherent long term plan for the field in all of its Frontiers — Cosmic, Energy and Intensity.

The young scientists forum at Snowmass is organizing a survey to obtain a snapshot of views, concerns and aspirations of our scientists, specially those at the early stage of their careers. We are reaching out to students, postdocs and faculty asking that you contribute by completing the survey and forwarding this message to your colleagues.

The link to the survey is: http://tinyurl.com/snowmassyoung

The estimated time to complete the survey is 5 to 10 minutes. You will note that the survey also includes questions for those who left academia, so if you can help us reach more people from that demographic group, that will be much appreciated too.

Thank you very much for your participation!

Cheers,
Marcelle Soares-Santos
On behalf of the Snowmass Young group.

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The Realm of the Nebulae

41CF7V31PmL._SY300_ Edwin Hubble never really liked the word “galaxy.” He was the one, of course, who was most responsible for making the word an important one, by showing that (at least some of) the fuzzy patches in the sky called “nebulae” were actually collections of billions of stars in their own right, far outside our Milky Way. (That was his second-most important discovery, after the distance-redshift relationship that reveals the expansion of the universe.) It’s possible that Hubble didn’t want to do any favors for Harlow Shapley, his rival, who coined the term “galaxy.” But for whatever reason, when in the 1930’s he gave a series of prestigious lectures at Yale which he later turned into a book, Hubble’s chosen title was The Realm of the Nebulae. Near the end of his introductory chapter, he sniffs, “The term nebulae offers the values of tradition; the term galaxies, the glamour of romance.”

In the court of popular opinion, romance will usually be a heavy favorite over tradition, and these days we use “galaxies” to refer to large collections of stars, gas, dust, and dark matter. But Hubble’s book became a classic, and is a great treat to read these many decades later. Cosmology has marched on quite a bit, of course, but the insights Hubble offers into the practice of doing science are timeless. The guy was a smart cookie, and a better-than-decent writer, to boot.

So it’s great to have a new edition of the book recently published by Yale University Press. Precisely because science has been advancing in the intervening years, publishers have found it useful to commission new prefaces to keep the reader updated on cosmological progress, and these prefaces (or Forewords, I can never tell the difference) have been accumulating over time, all of them contained in the new version. There’s one by Allan Sandage, from 1958; another by James Gunn, from 1981; and now our Golden Age of Cosmology requires not one but two new contributions, one by Robert Kirshner and one by me. Given the extraordinarily high quality of my companion contributors to the front of the volume, I tried hard to make my offering both interesting and useful. Readers can judge that for themselves, but it’s certainly an honor to be in such esteemed company.

Hubble was an unforgiving empiricist; he didn’t worry too much about the theoretical implications of his discoveries, preferring to leave that to others. But he knew about them, and his last chapter discusses the different world models to emerge from Einstein’s general relativity, and the implication that we will only ever be able to observe a small part of the much larger universe.

Thus the explorations of space end on a note of uncertainty. And necessarily so. We are, by definition, at the very center of the observable region. We know our immediate neighborhood rather intimately. With increasing distance, our knowledge fades, and fades rapidly. Eventually, we reach the dim boundary — the utmost limits of our telescopes. There, we measure shadows, and we search among ghostly errors of measurement for landmarks that are scarcely more substantial.

The search will continue. Not until the empirical resources are exhausted, need we pass onto the dreamy realms of speculation.

Fortunately, and contrary to the metaphorical implication, the dreamy realms of speculation aren’t a location where we have to remain once we arrive. Progress in science requires cooperation between speculation and observation. The dreamy realms are an important place to visit, even if Hubble wouldn’t have wanted to live there.

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Closer to Truth

A couple of years ago at the Setting Time Aright conference, I sat down for an interview with Robert Kuhn, who has a program called Closer to Truth. Time passed, as it will, and I never knew what happened to the interview. But apparently it’s up on the web now, freely available to anyone wishing to click (although apparently not embeddable).

So go here if you want to see some short clips of me sitting in a dark, atmospheric setting, declaiming earnestly about various profound topics, from atheism to infinity.

Oh, and I suppose it’s possible you might want to hear other people as well. They’re all here — there are some great people, from Nima Arkani-Hamed to Marvin Minsky. (More than a few clunkers, as well, but you get what you pay for.)

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CP Violation and the Information/Anti-Information Asymmetry

Do a physics experiment. Now take that experiment, change all the particles to antiparticles, and reflect the entire apparatus around some fixed plane. If you get an equivalent result, we say that the experiment preserves charge/parity symmetry, or CP for short. Most mid-century physicists originally assumed that CP would be a good symmetry of nature — switching matter with antimatter also requires switching left with right, but why should left-handed particles behave any differently than right-handed antiparticles? But in the 1960’s Cronin and Fitch showed that it was violated by the decays of neutral kaons, for which they picked up a Nobel Prize in 1980.

Since then, studying CP violation has been a fruitful pursuit for particle physicists. The decay of various quarks into each other generically violates CP (as shown by Kobayashi and Maskawa, Nobel 2008), so searching for CP violation gives us a lot of leverage when we try to map out the dynamics of particles in the Standard Model. Which is why it was big news today when CERN announced that the LHCb experiment has observed CP violation in a brand-new system, decays of the Bs meson. (Here’s the paper.) It’s only the fourth known particle to have CP-violating decays, joining the kaon, the D meson, and the regular B meson. (The subscript s means there is a strange quark involved.) A brand-new way to study a mysterious subatomic process, learn more about the Standard Model, and launch an ambitious search for new physics! Should be enough to get anyone excited.

But it’s not, of course — there are people out there who stubbornly resist the charms of precision electroweak particle physics. So it’s traditional to make an appeal to something nominally more sexy: the matter/antimatter asymmetry of the universe.

I’ve complained about this before, to little avail. The logic is as irresistible as it is faulty: the process of baryogenesis, by which matter came to dominate over antimatter, requires that there be CP violation in the early universe; we are studying CP violation here in the late universe; obviously, what we’re doing helps us understand the matter/antimatter asymmetry. But that’s only true if the kind of CP violation we are studying is actually somehow related to baryogenesis. Which, most experts believe, it is not.

Here’s a piece in Symmetry Breaking which makes the case against itself quite clearly. It starts with:

When the universe was less than a minute old, a tiny difference in the behavior of matter and antimatter led to the matter-dominated existence we experience today. Today, particle physicists on CERN’s LHCb collaboration announced that, for the first time, they have observed particles called strange beauty mesons, or B0s, contributing to this imbalance.

That seems pretty unambiguous: they are saying that physicists have observed a process that contributed to the matter/antimatter asymmetry. It’s only at the end of the article that they admit you’ve been duped:

However, the Standard Model predicts only a tiny portion of the amount of CP violation needed to explain the huge deficit of antimatter in the universe. While these results help scientists understand the mechanics of CP violation, the case of the missing antimatter remains unsolved. “We expected a certain amount of CP violation to be found in the strange beauty system,” says Pierluigi Campana, the LHCb spokesperson. “But finding the missing fraction of CP violation in the early universe will be new physics, which the Standard Model can’t predict.”

That’s the point: baryogenesis requires CP violation, and the Standard Model has CP violation, but almost everyone agrees that the Standard Model by itself can’t possibly explain baryogenesis. But it can explain the new results from LHCb. Chances are extremely high that the CP violation observed at CERN has nothing at all to do with the asymmetry of matter and antimatter. But who wants an inconvenient fact to get in the way of a good story?

What’s going on here is exactly the same bait-and-switch syndrome that’s responsible for the “God Particle” name, or selling a cosmology book by pretending it’s about why there is something rather than nothing, or mixing up time-reversal violation with the arrow of time. I got in trouble for complaining about that last one, too, with folks who thought I was denigrating a good piece of experimental science. But it’s quite the opposite: I’m saying that the truth is interesting enough, there’s no need to try to sell it via dubious connections with something that supposedly is more marketable!

The Higgs boson, modern cosmology, time-reversal invariance, CP violation — these are really interesting topics. It’s our duty to sell them and explain them at the same time; not do the former at the cost of the latter. It doesn’t do any good if people think that what we do is interesting, but only because we’ve misled them about what that actually is. The good folks at LHCb have every reason to be extremely proud that they’ve discovered a new system that violates CP, and launched a new way to study Standard Model physics and hopefully look for phenomena that stretch beyond that. They don’t need to hitch their wagon to the baryogenesis star.

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Frogs See Photons

Arrgh, I have really wanted to hop back on the blogging bandwagon, but this travel/work reality has made it tough. Next week, though, I plan to be blogging like a banshee. If banshees could blog. And if, when they did blog, they did so frequently and with enthusiasm.

Just got back from the North Carolina Science Festival in Charlotte, where I talked about the Higgs boson. You can find some live-tweeting of the event by searching the hashtag #HiggsTalk. Among all the deep and inspirational points I tried to make, one seemed to create the biggest impression: frogs can see individual photons.

This is an example I got from David Deutsch’s book The Fabric of Reality. It’s an attempt to connect our underlying fundamental description of the world, which is in terms of fields, to what we see when we make a quantum observation, which is in terms of particles — at least if we look closely enough. Deutsch’s point is that human vision is a bit too crude to detect just one photon at a time, but frogs (and presumably other animals) are sensitive enough to see single photons.

Such a fun and quirky fact naturally raised the skeptical instincts of some folks in the room, and to the internet they all went. Is it actually true?

Turns out, to the extent that a few minutes of googling around can reveal, it’s not an easy question to answer. It’s certainly true that the photoreceptors in a frog’s eye are sensitive enough to trigger on individual photons — indeed, researchers are using frog’s eyes to help fashion hybrid light-detector technology. But on the other hand, human photoreceptors are also sensitive enough to trigger on individual photons — and yet, we don’t as a matter of fact actually see photons one at a time. The presumption is that we would be seeing too much noise if our brains actually responded to such low levels of light; in practice, it seems to take several dozen photons before a human will say they see something.

So maybe the same is true for frogs? I wasn’t able to find a definitive-sounding word on the subject, but there is good reason to believe that frogs are at least much more sensitive than we are. The point is that noise we filter out is roughly proportional to body temperature. In a warm-blooded creature, simple thermal motions are constantly jostling the rhodopsin molecules in the eye, which could mimic the act of seeing something. A cold-blooded frog isn’t as susceptible to this problem, so its vision can be usefully much more efficient at low light levels.

Of course none of this matters to the actual point being made in my lecture, which is that light is really a vibration in the electromagnetic field, but careful observations (be they by frogs or artificial photodetectors) reveal individual energy packets call photons. It’s not that the field is “made of” photons, it’s that what we see when we perform measurements in a world governed by quantum mechanics is different from what the world is “actually made of,” to the extent that it’s okay to think about such a concept. Which, with all due respect to my croaky amphibious friends, is more amazing to me than all the eyeballs in the world.

What Can Frogs See That We Can't?

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Goddamn Particle

Hey, did you hear that Planck released its results today? The universe remains preposterous, if still pretty awesome. And it might be lopsided, which is intriguing.

Planck says that dark matter makes up 26% of the universe, while the best-fit WMAP number from a few years ago was 23%. This led me to joke on Twitter that we needed a model in which the dark matter density was rapidly increasing. Just a joke, people!

I hope to say something more substantive soon, but in the meantime there’s plenty of good stuff around the web; at the risk of leaving many people out, see Ethan Siegel, or Jester, or simply refuse to see the universe through anyone’s filter but your own and read the original papers. (An even thirty of them, helpfully indexed by the ultramodern system of Roman numerals.)

Meanwhile, our old friend the Higgs boson has not gone away. Here’s the second of the videos I did for Sixty Symbols while visiting the UK (after the first one I did on quantum mechanics).

Talking about the Higgs Boson - Sixty Symbols

The comments on the YouTube page are nicer than average. Maybe it’s the British temperament.

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Cosmology Results from Planck Tomorrow

The Planck satellite, a European cosmic microwave background observatory, was launched in 2009 and is finally ready to release its first set of cosmology results. (It has already released findings on galaxies and dust and so forth — what early-universe cosmologists call “foregrounds” and others call “my life’s work.”) They will be showing us the highest-precision all-sky map of the microwave background ever made. The announcement starts at 10 a.m. Paris time, which works out to 2 a.m. Los Angeles time. Don’t expect me to be live-blogging.

So what should we be looking for? Typically an experiment like this isn’t just a fishing expedition; scientists have a pretty clear idea of what questions they would like answered, and what discoveries they might be able to make. Nature is always capable of surprising us, of course. There are some very useful posts on this question by Renee Hlozek and Shaun Hotchkiss. (I hope everyone reading those posts will take a moment to appreciate how wonderful it is that we live in an era where real experts can chime in directly on important scientific questions.)

A CMB map contains an enormous amount of information, especially if you are measuring the polarization as well as the temperature at each point. My understanding is that this edition of the Planck results will not include polarization, but that will be coming some day down the road. (And Max Tegmark’s $100 is safe for another few months.) Nevertheless, a lot of the interesting information boils down to the “power spectrum,” which tells us how strongly the temperature varies on different angular scales. Of course, there are a few observables that go beyond the power spectrum, and those are some of the most interesting ones.

Here are some of the major things cosmologists might want to learn from the CMB temperature anisotropies:

  • Did the original perturbations we inherited from the early universe have the same amplitude on all scales, or were the slightly different?
  • What are the best fits for cosmological parameters such as the density of dark matter and dark energy, the numbers and masses of neutrinos, and the Hubble constant? Or even spatial curvature?
  • Are there persistent “anomalies” that can’t be easily accounted for by a simple theory of primordial perturbations? For example, do the anisotropies somehow define a preferred axis in space?
  • Are the perturbations completely random — “Gaussian” — or are there hints of primordial non-Gaussianity, which might help pin down specific models of inflation?

I suspect it would be wise to keep expectations low for Earth-shattering (or universe-shattering) discoveries here, although I’d certainly welcome a surprise. The amplitude of the primordial perturbations has already been nailed down fairly well, by the Atacama Cosmology Telescope as well as by the South Pole Telescope that I blogged about. From Renee’s post, here is a graph of the data from the WMAP satellite as well as ACT and SPT, which as you can see are pretty compatible with each other as well as with the theoretical prediction. We might get a more definite finding that the amplitudes aren’t strictly the same at all scales, which would be good news for proponents of inflation.

wmap9+spt+act

We definitely hope to get more precise measurements of cosmological parameters, especially the number of neutrino species and their masses. Evidence from particle physics experiments here on the ground is inconclusive when it comes to the number of neutrino species — very recent results from the MiniBooNE experiment seem to point in the direction of sterile neutrinos that don’t feel the weak interactions. If such neutrinos are produced in the early universe, they could have an effect on the CMB anisotropies. Obviously any definitive statement that there were more than three kinds of neutrinos would be huge news. The other hope for groundbreaking news would be the discovery of nonzero spatial curvature, but nobody really expects that.

As far as anomalies are concerned, Planck has a very different scanning strategy than WMAP had, so it’s possible that it will squelch some people’s favorite anomalies. But there is the problem of cosmic variance (in the original sense) — on very large scales, there is a limited number of modes we can measure, since we only get one universe. If large-scale fluctuations just happen to be statistically anomalous, it might be very difficult to ever decide whether it’s an accident or the sign of new physics.

The search for non-Gaussianities (correlations between fluctuations on different scales) is possibly the most interesting thing we should be looking at in the current release. If inflation is right, you may or may not see deviations from perfectly Gaussian behavior, depending on the kind of inflation we’re talking about. Roughly speaking, we expect perturbations to be Gaussian in simple models of inflation with ordinary dynamics of a single scalar field, but adding bells and whistles to your inflationary model can introduce some non-Gaussianities. So it’s not really evidence for or against inflation, but limits the model space if inflation is the right answer.

Let’s offer early congratulations to the Planck team, who have certainly worked incredibly hard to get to this point.

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More Messy Dark Matter

Longtime readers know that I’m fascinated by the possibility that dark matter is “interesting.” Of course dark matter is by its very nature interesting, but I’m referring to the idea that the dark matter isn’t simply a single neutral particle with a negligible rate of interaction in the current universe, but rather a set of one or more kinds of particles with some noticeable forces acting between them. Friends of mine and I have investigated the idea of dark photons — dark matter being charged under a new “dark force” resembling ordinary electromagnetism. The next obvious step is dark atoms — two different kinds of charged dark particles that can join together in atom-like bound states. These ideas, it turns out, are fairly compatible with what we know about the dynamics of dark matter in the real universe.

Now a new paper by JiJi Fan, Andrey Katz, Lisa Randall, and Matthew Reece examines the particle physics and astrophysical consequences of a somewhat more elaborate version of this idea, which they call “Partially Interacting Dark Matter.” The idea is that most of the dark matter is vanilla and boring, but some fraction of it is atom-like. This has interesting implications for galaxies and small-scale structure. Here’s the abstract:

Double-Disk Dark Matter
JiJi Fan, Andrey Katz, Lisa Randall, Matthew Reece

Based on observational tests and constraints on halo structure, dark matter is generally taken to be cold and essentially collisionless. On the other hand, given the large number of particles and forces in the visible world, a more complex dark sector could be a reasonable or even likely possibility. This hypothesis leads to testable consequences, perhaps portending the discovery of a rich hidden world neighboring our own. We consider a scenario that readily satisfies current bounds that we call Partially Interacting Dark Matter (PIDM). This scenario contains self-interacting dark matter, but it is not the dominant component. Even if PIDM contains only a fraction of the net dark matter density, comparable to the baryonic fraction, the subdominant component’s interactions can lead to interesting and potentially observable consequences. Our primary focus will be the special case of Double-Disk Dark Matter (DDDM), in which self-interactions allow the dark matter to lose enough energy to lead to dynamics similar to those in the baryonic sector. We explore a simple model in which DDDM can cool efficiently and form a disk within galaxies, and we evaluate some of the possible observational signatures. The most prominent signal of such a scenario could be an enhanced indirect detection signature with a distinctive spatial distribution. Even though subdominant, the enhanced density at the center of the galaxy and possibly throughout the plane of the galaxy can lead to large boost factors, and could even explain a signature as large as the 130 GeV Fermi line. Such scenarios also predict additional dark radiation degrees of freedom that could soon be detectable and would influence the interpretation of future data, such as that from Planck and from the Gaia satellite. We consider this to be the first step toward exploring a rich array of new possibilities for dark matter dynamics.

Most investigations of dark matter indicate that it is spread much more tenuously through the universe than ordinary matter, which tends to clump together. The basic idea is illustrated in this artist’s conception of the dark matter halo associated with our Milky Way galaxy and its Magellanic Cloud satellites. (Update: oops, reading comprehension failure on my part. This is an artist’s conception of hot gas around the Milky Way, not dark matter, as Peter Edmonds pointed out on Twitter. But they look similar!)

halo-580x472

There is a straightforward explanation for this behavior: ordinary matter feels the electromagnetic interaction, so atoms can bump into each other and release energy by radiating photons, which lets them “cool” and settle down into relatively dense clumps (like galaxies and even stars). Standard dark matter particles have very weak interactions indeed, so when they fall into a gravitational potential well they just zip through the other side without cooling, giving the dark matter distribution a much puffier profile.

Here Fan et al. are suggesting that part of the dark matter could form atoms and cool, allowing it to clump more efficiently in the centers of galaxies. This could lead to more frequent dark-matter annihilations than we would otherwise expect, which might be suggested by some tantalizing observational results (although that’s fairly tentative).

It’s fun to think about, although we’re far away from drawing any firm conclusions at the moment. But we won’t know how to test these ideas observationally unless we work out their predictions theoretically. It’s a complicated universe, we need to be prepared.

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Science, Morality, Possible Worlds, Scientism, and Ways of Knowing

The relationship between science and morality popped up again on some of the blogs I regularly read, but real life getting in the way has prevented me from responding until now. Here’s Michael Shermer, Eric MacDonald, Massimo Pigliucci, and Jerry Coyne. I’ve spoken about this stuff more than anyone wants to hear (1, 2, 3, 4, 5, 6), but perhaps the wisdom that comes with advancing age has helped me boil the point down to the essence more effectively.

Morality will never be reduced to science, nor subsumed into the greater scientific project. It will increasingly make use of scientific discoveries, but it is fundamentally a separate endeavor; there will always be something necessary to get morality off the ground that simply isn’t part of science.

Here are some statements that are solidly part of science:

  • The universe is expanding.
  • Oxygen is delivered to the body by circulating blood.
  • The Sun will run out of nuclear fuel in several billion years.

What makes these statements scientific? I would say two things (admitting that we are glossing over many subtle points here, but trying to remain focused on the big picture).

  1. They could be false. That is, we can imagine possible worlds in which these statements were not true. We couldn’t decide on their truth just by thinking about them.
  2. They can, in principle if not in practice, be evaluated empirically — by doing the right experiments or collecting the right observations.

Of course we need to assume that all the appropriate definitions of the terms we are using have been established. Note that a statement doesn’t have to be true to be scientific; “The universe is contracting” is equally scientific as “The universe is expanding.” Finally, the “in principle if not in practice” is crucial. We can’t actually collect the data that shows directly that the Sun is out of nuclear fuel several billion years from now, at least not at the moment. But it is clear what form those data would take, and that’s all we really need. More realistically, the statement is implied by a theoretical superstructure that can itself be tested directly in the here-and-now.

Here are some statements that are not scientific.

  • 1+1=2.
  • Hamlet was really crazy, he wasn’t just faking it.
  • Chunky Monkey is the best possible ice cream.

The first statement kind of looks sciencey; it’s part of math. But you don’t need to do any experiments to evaluate whether it’s true. It can’t help but be true, once the terms are understood; there are no possible worlds out there in which 1+1=3, in the conventional definition of those symbols. So it’s math, or logic, or philosophy; but it’s not science.

The second statement is again not science because there is no data we could conceivably collect that would judge its truthfulness, but in a different way. You might think that we just need to collect more data about Hamlet’s mental state, but that’s going down the wrong path; there is no such data, because Hamlet is a fictional character. The words of the play are all the data that exist or ever will exist. You might also suggest that in principle we could collect data relevant to Shakespeare’s mental state, perhaps some notes of his establishing that he always thought Hamlet was just faking. But that only bears on the question “Did Shakespeare think of Hamlet as really crazy?” (which is scientific), not “Was Hamlet really crazy?” (not).

The ice cream question is the one that is closest to the issue of morality. Again, one might suggest that all we need to do is collect neurological data relevant to the functioning of pleasure centers in the brain when one eats different kinds of ice cream, and decide which does the best job. But that’s the question “What effect do different flavors of ice cream have on the brain?” (which is scientific), not “What flavor of ice cream is the best?” (not). To answer the latter question, we would have to know how to translate “the best ice cream” into specific actions in human brains. We can (and do) discuss how that might be done, but deciding which translation is right is — you guessed it — not a scientific question. If I like creamy New-England-style ice cream, and you prefer something more gelato-y, neither one of us is wrong in the sense that it is wrong to say that the universe is contracting. Even if you collect data and show beyond a reasonable doubt that New York Super Fudge Chunk lights up my brain more effectively in every conceivable way than Chunky Monkey does, I’m still not “wrong” to prefer the latter. It’s a judgment, not a statement about empirically measurable features of reality. We can talk about how we should relate such judgments to reality — and we do! — but that talk doesn’t itself lie within the purview of science. It’s aesthetics, or taste, or philosophy.

And that’s okay. There are many kinds of questions, moral ones among them, that have a scientific component but cannot ultimately be reduced to science. Consider a statement of the form

  • We should work to maximize the well-being of conscious creatures.

This is not a scientific statement. To convince me otherwise would be straightforward enough. Simply delineate what the worlds would be like in which that statement is true, and the worlds in which it is not true, and then tell me what data we need to collect to decide which kind of world we live in. Obviously this is absurd. Science is relevant to morality, and we should ground our moral conversations on correct ideas about the physical world rather than incorrect ones, but deciding the truth of moral claims is always going to involve something other than simply doing science.

I don’t like using the word “scientism” to label the unfortunate desire on the part of some people to hope that every interesting question can be reduced to science, because the folks who do like using it are often people whose side I’m really not on. Nevertheless, there is a real mistake that can be sensibly labeled “scientism.” Likewise, I generally take the phrase “ways of knowing” as a sign that I can stop listening and start checking Twitter on my iPhone, no matter which side of the debate the speaker is on. Are mathematics, literary criticism, aesthetics, and morality “other ways of knowing”? It would be hard for me to care less. They are different areas of thinking and judging than science is, that’s for sure. If you really want to call them “ways of knowing,” you should work hard to make the distinctions clear — they are not ways of making statements about what happens in the world, which is an empirical endeavor.

Grumbling aside, it’s always a long-term good when smart people come from very different perspectives to hash out difficult issues in a changing intellectual landscape. There are real moral questions that confront us every day, and as a society we’re still burdened with a slapdash pre-rational way of answering them. I look forward to the day when there is a consensus theory of secular moral philosophy that forms a basis for democratic discourse, and we’re teaching fifth-graders how to cope with trolley problems.

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Brain-to-Brain Communication

Over at Nature, Ed Yong reports on a new study by Miguel Pais-Vieira and collaborators, in which mental activity in the brain of a rat living in Brazil is communicated directly to the brain of a rat living in North Carolina, which responds accordingly (sometimes; at least greater than by chance). Ed was able to find another researcher to give the mandatory curmudgeonly response, comparing the work to a “poor Hollywood science-fiction script.” To which the rest of us respond: we want to see that movie!

This isn’t my bailiwick, obviously, so check out Ed’s article or the original paper. The basic idea is that the Brazil rat sees a light, and presses a lever that it has been trained to when that light goes on. An implant records activity in the rat’s motor cortex (in charge of pressing levers), which is then encoded and sent to the North Carolina rat, which presses the corresponding lever itself. At least, about 64% of the time. Which is a pretty noisy signal, but a signal nonetheless.

Direct mental communication won’t be replacing email any time soon. But unlike our skeptical commentator, I think experiments like this are important. They prod people’s minds in the direction of thinking about what might someday be possible.

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