Search Results for: hawking

Leave it to Umberto Eco to draw together the recurring themes of the humble blog before you. From Arts and Letters Daily, a link to a rumination by Eco on Stephen Hawking’s recantation of his previous stance that black hole evaporation destroys information. Eco uses the occasion of Hawking’s flip-flop to draw a distinction between science and idealistic philosophy. (Thanks to Norman Graf for the last link.)

It’s a distinction well worth drawing. One of the reasons why it’s hard to define “science” is that the nature of scientific theories keeps changing, with concurrent debates about what really counts as scientific (e.g., whether entities we can never in principle observe should be part of a respectable scientific theory). But the distinguishing feature of science is not the theories it produces, but the methodology it uses for getting there. Eco labels the crucial feature of this methodology “provando e riprovando,” Italian for “try and try again.” That is to say, we propose all sorts of ideas, not because we have convinced ourselves that they are right, but because we don’t know what is right and we’re searching through all of the possibilities. Ultimately, agreement with the data will be the deciding factor, and often we can be very surprised at what kinds of theories come out on top (quantum mechanics being the most notable example.)

This strategy is something that non-scientists have trouble really believing in, even those who rub up against science every day. For example, I have been heavily involved in studying models of dark energy, or more broadly why the universe is accelerating. One idea that received some attention is the possibility that Einstein was wrong, and we have to modify gravity on cosmological scales. In talking to journalists, they would often ask me to explain why my theory was better than the alternatives. I had to explain that I didn’t think it was better than the alternatives — it was interesting and provocative, and it had a chance of being correct, but I didn’t necessarily believe that it had a better chance than anything else. We don’t only propose ideas we are convinced are right; we propose lots of things and let the chips fall where they may.

Even scientists and other academics don’t always quite get the idea. I recall a talk given by an evolutionary psychologist, about the new center he was trying to found. The point of this center, according to his conception, was to demonstrate how important behaviors can find their explanations in the evolution of adaptive strategies. This is a terribly depressing mistake; the point of science is never to “demonstrate” anything, it’s to sift through the interesting alternatives and decide which works the best, keeping an open mind at all times. (There is some art, to be sure, in deciding which alternatives are even worth our attention, and at what point a question can be considered to be satisfactorily settled.) If the “physics envy” felt in other disciplines were directed toward this kind of open-minded methodology, rather than to the impressively quantitative final products of physics, the world would be a better place.

It’s not a coincidence, of course, that Eco also wrote the article on fascism that I commented about a sort while back. Nor is it a coincidence that scientists are especially riled up by the transgressions of the Bush administration (much more so than their general liberal tilt can explain). The distrust of indecision and ambiguity that is a hallmark of our current administration is an especially anti-scientific attitude. So you see, the science and politics posts here at Preposterous do share deep connections. Still no explanation for the posts about poker.

I am back from the wilds of Wyoming, having happily scampered through the Jurassic for a few days. A full report will be forthcoming. But first I wanted to thank Gretchen for filling in while I was gone; hopefully she will post again in the future.

A lot can happen in one short week, so I just wanted to hit some high points of the events you had to endure without me.

• The big news, my man Barack Obama hit a home run at the convention. I didn’t get a chance to see the speech, which I hear was not even broadcast by the networks. Also we were staying at a ranch owned by folks who were quite hospitable, but whose politics didn’t really align with mine. The first clue was the large painting of Jesus kneeling in front of the Liberty Bell. I must have missed that chapter in the Gospels. So Democratic-convention-watching wasn’t one of the scheduled activities.
• But actually, is the lack of coverage by the networks worth all of this hand-wringing? Don’t most people have cable TV by now, and don’t the cable networks cover the thing to death? I never understood why there was supposed to be a moral imperative for all three networks to provide essentially the exact same pictures. They could just rotate, like with the Olympics (without the dizzying rights fees).
• Despite the Dems having apparently stage-managed the convention quite skillfully, the free speech zones are a travesty. (Images found linked at Majikthise.) Their existence is a travesty on basic philosophical grounds, but their appearance is a disaster purely on craven political grounds. I mean, barbed wire?
• In one last bit of Hawkingiana, it’s worth pointing to this statement by John Preskill about the bet he won with Hawking (found linked at Michael Nielsen’s blog). Poor Preskill, who is a world-class theoretical physicist in his own right, but can only get in the newspapers by winning bets with Hawking.
• Francis Crick passed away. Most of what I know about Crick comes from reading The Double Helix, which I’m sure isn’t the most reliable source. More discussion at the Panda’s Thumb.
• Atrios unmasked! With his permission. (That’s the mysterious Atrios of Eschaton, for you scientists out there.)
  
• Finally, let’s give some props to Allen Iverson of my beloved Philadelphia 76ers, one of only two NBA stars (along with Tim Duncan) to fulfill his initial obligation to go to Greece as part of the Olympic team. Iverson has his issues, but he has always been treated far worse than he deserved, just because of his hairstyle and tattoos. Now he’s the co-captain of the Olympic team, which has to feel good.

I’m sure other interesting things “happened,” but if I wasn’t paying attention to them, how real can they be?

Enough talking about Hawking, I would think. There are a bunch more newspaper stories out there (including these from Newsday and the New York Times that were nice enough to quote me). Also, Juan Maldacena and I appeared together today on Odyssey, the program hosted by the very same Gretchen Helfrich who will soon be our official guest-blogger. No quid-pro-quo was involved, I promise. You are welcome to listen to the program if you have RealAudio.

Just to show you that scientists don’t always agree, two representative quotes. First, Leonard Susskind in the Times:

Until Stephen’s recent reversal, he was about the only person still getting it wrong.

Susskind is a string theorist who thinks that it’s already been figured out, nothing to see here, time to move on. Next, from my colleague Bob Wald:

Hawking is completely revising his prior belief that what goes into a black hole is washed out. Now he believes that anything emitted from a black hole can be identifiable back to its source. He’s running away from what we still believe.

Wald is a general-relativist, quite skeptical about the claimed mechanisms for getting the information out. This is the problem with thought-experiments; they’re not nearly so conclusive as actual experiment-experiments.

Imagine that your home is broken into by a group of physicists with mischief on their minds. They grab your collection of books and CD’s, but instead of just making off with them, they crunch them together to make a black hole. (Applied physicists, obviously.) In the old days, you might have been quite despondent, thinking that all of the information in your collection of music and literature had been lost forever. However, as we all know by now, almost thirty years ago Hawking showed that black holes don’t just sit there, they emit radiation, and in the process of emission they lose energy and eventually evaporate away completely (if you don’t keep putting extra energy in). So now you might think that you could be very clever, and recover the information that you thought was lost: just observe absolutely every particle emitted in the Hawking radiation, and use your knowledge of what came out of the black hole to reconstruct what went in. In practice this would be a bit far-fetched, but in principle this is exactly what you could do if, for example, the pranksters had just set your collection on fire instead of collapsing it to a black hole. Physicists tend to believe that information is never really lost in physical processes, even if it gets re-arranged into less useful forms.

But black holes are different, sadly. To the best of our knowledge, there is no correlation between what went into making the black hole and what kind of radiation comes out. Indeed, there are reasonable-sounding arguments that there can’t be any such correlation. In that case, the information originally present in your books and CD’s has truly been lost.

Of course, we haven’t seen any black holes up close and evaporating, so these are all thought experiments thus far. But it bugs people to no end to think that evaporating black holes violate such a cherished notion of physics; this conundrum is known as the black hole information loss paradox. For a long time we didn’t even know whether the information could somehow be stored in a black hole, much less retrieved; more recently, however, string theorists have shown that (in many cases) that the amount of information in the black hole really is the same as contained in the stuff that went into making it. And there have been a couple of very clever proposals recently, one of which might turn out to be on the right track: Horowitz and Maldacena have suggested that the Hawking radiation that falls into the black hole is carefully arranged to cancel out the information of the infalling matter, effectively transferring it to the outgoing radiation; while Mathur has suggested that we need to dramatically change our ideas about what the interior of the black hole is like, enough so that the information is actually sitting close to the surface where perhaps it can escape more easily.

I bring this up because I have secret inside information which I now feel empowered to reveal, since the rumors seem to be public anyway. Stephen Hawking has asked to give a plenary talk at a big upcoming conference, where he says he will announce a solution to the information loss problem. As a member of the scientific organizing committee of GR17, I got the email request from our chief organizer; was there any chance we would say “no”? But actually I doubt very much that Hawking will simply announce a solution that everyone will agree with. Theoretical physics just doesn’t work that way. Even if he has a clever idea, people will have to wrestle with it themselves before it would catch on. Also, Hawking isn’t always right; for a long time he has been insisting that information really is lost, which is certainly a minority viewpoint. Unfortunately I won’t be at the conference, which is July 18-23 in Dublin. But I’m sure we’ll be seeing news reports about Hawking’s talk; the media love him, for good reason.

An apparent rupture in the spacetime continuum has been noted over at archy and Pandagon. In one of the questions asked to President Bush on his current “bus” tour, the interlocutor referred to an apparent acausal propagation of economic hardship:

In 1998, due to the impending recession, I started living the American nightmare.

John McKay at archy wonders whether there could be a quantum-mechanical explanation for how anyone could be suffering through the effects of a recession that wouldn’t begin for another two years. But I think it is more likely that the explanation requires closed timelike curves. You see, in relativity it is impossible to move faster than the speed of light; physical particles are therefore confined to move along “timelike” trajectories that move inexorably forward in time. But in general relativity spacetime is curved; it is therefore conceivable that a timelike curve can loop back and intersect itself in the past, in a kind of time machine. Bush’s questioner had obviously found such a closed timelike curve, lived through the horrors of the recent recession, gone backwards in time, and cowered in fear as he lived once more through 1998 with the ever-present knowledge that the economy would tumble just about the time Bush was elected. Of course, it is probably necessary to violate some of the laws of physics to actually create closed timelike curves in the real world; this is the content of Hawking’s Chronology Protection Conjecture. But the administration has never let the laws of nature get in the way of their plans.

Or, I suppose, maybe the bus-tour audiences are not completely representative samples of the local population; one might even suspect that they are carefully selected to be sympathetic. But that would make me a wacky conspiracy theorist. Besides, there was one actual question, when Bush was asked about a cut in federal funding to local health services. His priceless response, as reported on NPR:

Well, that’s what happens when you’re trying to cut the deficit in half.

Such an answer cannot be explained simply by closed timelike curves; we need to invoke parallel universes.

Good news and bad news. First the good: David Appell has restarted his blog, Quark Soup. Good links to all sorts of science stories, with interesting commentary.

Now the bad: in one of David’s recent posts, he brings to our attention a slightly loopy screed about experimental gravitation by Gregg Easterbrook. It’s a tired argument, sloppily made: we shouldn’t spend government money on speculative scientific research without any tangible benefits to society. In particular, he picks on the LIGO experiment to detect gravitational radiation.

But while we’re counting tax-funded abstract science boondoggles, let us not forget the Laser Interferometer Gravitational Wave Observatory, a $365 million government project that is all but certain to have no practical result, other than as a jobs program.

He stoops as low as you might fear, suggesting that we should be spending the money on trying to cure AIDS. (I’m sure that, absolutist as he apparently is, Easterbrook donates all of his above-subsistence-level income directly to medical research. Those of us who think that we can try to help sick people and pursue other interests at the same time will presumably lead more complicated lives.)

Now, Easterbrook has long ago forfeited any right to be taken seriously when talking about science, for example in his classic discussion of extra dimensions, in which he can’t see why scientists are happy to talk about spatial dimensions but not spiritual ones. I wasn’t blogging at the time of that travesty, but he was justly ridiculed by Kieran Healy, Atrios, and many others.

But it’s a shame that he makes so little sense, because the question itself is well worth asking. How much money should we, as a society, devote to basic scientific research? It is undoubtedly expensive, and getting more so — the next big step in particle physics (after the Large Hadron Collider in Geneva) will be a twenty-mile long Linear Collider, whose cost will be measured in billions of dollars. The cost will be spread out over multiple countries and many years, but it still represents a substantial chunk of change. (I gave a talk on the connections between a linear collider and cosmology.) In a well-ordered society, it’s worth spending some fraction of our money on projects of this sort; but what should the fraction be? Libertarian fantasies aside, private donations just aren’t going to cut it.

You could talk about technological spinoffs from basic science, but that misses the point. The reason why it’s worth spending people’s money on research into the fundamental workings of the universe is because people want to know the answers. They might not understand the details, and more often than not they’ve been traumatized by science classes from high school, but ordinary people really care about these deep questions. That’s why they buy books and go to lectures by Carl Sagan, Stephen Hawking, or Brian Greene. The amount that gets spent on this kind of research is small compared to numerous other government projects (bridges in Alaska, anyone?), and the results are an unambiguous good for society. And the unfortunate fact is, some experiments aren’t worth doing at all unless you’re willing to spend the money. For half the cost of the Linear Collider, you won’t get half the science — you’ll get nothing. Maybe that’s the choice that the country wants to make; but that’s not the impression I get from talking with people on airplanes who are fascinated by what I do.

Here is my favorite part of Easterbrook’s latest:

Today’s science community is pressuring Congress and the legislatures of Europe to fund incredibly expensive mega-projects almost certain to benefit no one but the scientists themselves. It’s hard not to conclude that physicists and their universities are using mumbo-jumbo about Einstein and the universe–knowing not one member of Congress has any idea what a “gravity wave” is supposed to be or whether this matters–to hoodwink taxpayers into providing cushy jobs for tenured researchers and their postdocs.

Ah, yes, the cushy jobs. I’m so jaded by now, it’s nice to be reminded about how easy my life is. Just last night (Sunday), when I bumped into one of my students in the office around 10 p.m., and we talked about modifications of the Friedmann equation in the presence of Lorentz-violating vector fields, here I thought we were working hard just because we cared so much about the research we were doing. I had completely forgotten that we were really in it for the extended vacation time, exorbitant salary, and total absence of responsibility that comes with an academic appointment.

Don’t get me wrong; I love my job, wouldn’t trade it for anything. But “cushy” isn’t the word I (or anyone in their right mind) would use to describe it. Almost anyone who grinds through grad school and postdocs to get a faculty job as a scientist could be making more money for less work doing something else. But there are a lot more people trying to get these jobs than there are positions, for the same reason why the public is willing to support basic research — we want to know how our universe works. It’s the only one we have.

Update: Damn it, more evidence that administration is strangling NASA’s pure science budget, in favor of going to the Moon and Mars. Paul Krugman said it best: “Money-saving suggestion: let’s cut directly to the scene where Mr. Bush dresses up as an astronaut, and skip the rest of his expensive, pointless — but optimistic! — Moon-base program.”

This quarter Shadi Bartsch and I are teaching Moments in Atheism, an undergraduate course in the Big Problems curriculum here at the University of Chicago. I’m not sure what is more surprising, the idea of a course on the history of atheism, or the fact that I could get a humanities course to count as a regular teaching credit.

Teaching the course has been a fantastic experience; it brings me back to my own days as an undergraduate, exploring great ideas in philosophy and history. Indeed, one of the interesting things we have realized along the way is how much the history of atheism parallels all of the major twists and turns in the intellectual history of Western civilization generally. This has to be one of the few courses ever taught with Thomas Aquinas, Karl Marx, and Stephen Hawking on the same syllabus.

We were concerned at first about the touchy nature of the material; we wanted everyone to feel comfortable, no matter what their personal beliefs about religion were. So far it seems to be a success; there is a range of views represented in the class, and nobody has yet complained (out loud, anyway) about being marginalized.

One interesting discovery is the paucity of scholarly work on the actual history of atheism. It’s easy enough to find polemical books on either side of the issue, or careful philosophical works for and against the existence of God, but there’s not so much done on how the ideas have actually developed through time. Maybe because it’s a touchy subject? Also fascinating how reluctant people were to declare themselves atheists (until the 19th century), no matter how obviously the implications of their work were pushing them in that direction. Up at least through Hume, the pressure was so great that nobody could admit to disbelieving in God, even if they thought He was completely powerless in the world, or equal to the world.

Unfortunately we didn’t have time to do much about the present day. It’s still a touchy subject, of course; probably as much now as two hundred years ago. The elder George Bush famously said that he didn’t think that atheists should be considered as citizens. I’m not sure why the US and Europe seem to have diverged so dramatically on this.