Guest Post: Joe Polchinski on Black Holes, Complementarity, and Firewalls

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If you happen to have been following developments in quantum gravity/string theory this year, you know that quite a bit of excitement sprang up over the summer, centered around the idea of “firewalls.” The idea is that an observer falling into a black hole, contrary to everything you would read in a general relativity textbook, really would notice something when they crossed the event horizon. In fact, they would notice that they are being incinerated by a blast of Hawking radiation: the firewall.

This claim is a daring one, which is currently very much up in the air within the community. It stems not from general relativity itself, or even quantum field theory in a curved spacetime, but from attempts to simultaneously satisfy the demands of quantum mechanics and the aspiration that black holes don’t destroy information. Given the controversial (and extremely important) nature of the debate, we’re thrilled to have Joe Polchinski provide a guest post that helps explain what’s going on. Joe has guest-blogged for us before, of course, and he was a co-author with Ahmed Almheiri, Donald Marolf, and James Sully on the paper that started the new controversy. The dust hasn’t yet settled, but this is an important issue that will hopefully teach us something new about quantum gravity.

Introduction

Thought experiments have played a large role in figuring out the laws of physics. Even for electromagnetism, where most of the laws were found experimentally, Maxwell needed a thought experiment to complete the equations. For the unification of quantum mechanics and gravity, where the phenomena take place in extreme regimes, they are even more crucial. Addressing this need, Stephen Hawking’s 1976 paper “Breakdown of Predictability in Gravitational Collapse” presented one of the great thought experiments in the history of physics. …

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Let the Universe Be the Universe

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My article in the Blackwell Companion to Science and Christianity, which asks “Does the Universe Need God?” (and answers “nope”), got a bit of play last week, thanks to an article by Natalie Wolchover that got picked up by Yahoo, MSNBC, HuffPo, and elsewhere. As a result, views that are pretty commonplace around here reached a somewhat different audience. I started getting more emails than usual, as well as a couple of phone calls, and some online responses. A representative sample:

  • “Sean Carroll, servant of Satan…”
  • “God has a way of bring His judgement to those who mock Him… John Lennon stated “Christianity will end, it will disappear.” Lennon was shot six times after saying that… Marilyn Monroe said to Billy Graham after Graham said the Spirit of God had sent him to preach to her: “I don’t need your Jesus”. A week later she was found dead in her apartment.”
  • “See you in hell.”
  • “Maybe GOD is just a DOG that you will meet when you are walking on the Beach trying to figure out how to get sand out of your butt crack.”

I admit that last one is a bit hard to interpret. The others I think are pretty straightforward.

A more temperate response came from theologian William Lane Craig (a fellow Blackwell Companion contributor) on his Reasonable Faith podcast. I mentioned Craig once before, and here we can see him in action. I’m not going to attempt a point-by-point rebuttal of his comments, but I did want to highlight the two points I think are most central to what he’s saying. …

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Why String Theory?

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Breathless press reports notwithstanding, string theory is very far from being dead. If you’re interested in what it is and what’s going on within the field, I can recommend a new website called Why String Theory? (And of course, accompanying twitter feed @WhyStringTheory.) It was set up by Oxford undergraduates Charlotte Mason and Edward Hughes, working under Joseph Conlon. It’s a very engaging and professional-looking site, featuring a great deal of explanatory material.

Developing pedagogical sites like this is a great project for undergrads; the only looming issue is keeping the site going once the students move on to bigger and better things. Hopefully this one is kept up — I think an initial surge of interest has already been taxing the poor web server.

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Scientists, Your Gender Bias Is Showing

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Nobody who is familiar with the literature on this will be surprised, but it’s good to accumulate new evidence and also to keep the issue in the public eye: academic scientists are, on average, biased against women. I know it’s fun to change the subject and talk about bell curves and intrinsic ability, but hopefully we can all agree that people with the same ability should be treated equally. And they are not.

That’s the conclusion of a new study in PNAS by Corinne Moss-Racusin and collaborators at Yale. (Hat tip Dan Vergano.) To test scientist’s reactions to men and women with precisely equal qualifications, the researchers did a randomized double-blind study in which academic scientists were given application materials from a student applying for a lab manager position. The substance of the applications were all identical, but sometimes a male name was attached, and sometimes a female name.

Results: female applicants were rated lower than men on the measured scales of competence, hireability, and mentoring (whether the scientist would be willing to mentor this student). Both male and female scientists rated the female applicants lower.

This lurking bias has clear real-world implications. When asked what kind of starting salaries they might be willing to offer the applicants, the ones offered to women were lower.

I have no reason to think that scientists are more sexist than people in other professions in the US, but this is my profession, and I’d like to see it do better. Admitting that the problem exists is a good start.

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Time Talk

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With The Particle at the End of the Universe scheduled to come out in November, most of the popular-level talks I’ll be giving in the near future will have to do with the LHC and the Higgs boson — and quantum field theory, as part of my secret agenda to get QFT accepted as part of the mainstream pop-sci vocabulary. So I’ll be giving fewer talks about the arrow of time, at least near-term. I thought I’d commemorate the occasion by sharing the slides I used for a recent version of this talk: “The Origin of the Universe and the Arrow of Time.” Not that I’m by any stretch done talking about it, but hopefully the next time the occasion arises I’ll have the energy to make up new slides from scratch.

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Lectures on Emergence and Complexity

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Simon DeDeo is a theoretical physicist and very smart guy, who started out as a cosmologist and has made the transition to complexity theorist at the Santa Fe Institute. (He’s not smart because he made that transition, it just so happens that both statements are true.)

This summer he gave a series of three lectures at SFI’s Complex Systems Summer School, on the general topics of Emergence and Complexity. These are big ideas, and obviously one cannot say everything interesting there is to say about them in three lectures, but Simon manages to cover a lot of extremely important and fascinating topics such as coarse-graining, renormalization, computation, and effective theories. Worth a listen!

Lecture 1: Coarse-Graining, Renormalization & Universality

Lecture 2: Effective Theories for Computational Systems

Lecture 3: Symmetry Breaking and Non-Equilibrium Phenomena

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Faith and Epistemological Quicksand

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Alvin Plantinga and Thomas Nagel are well-known senior philosophers at Notre Dame and NYU, respectively. Plantinga, a Christian, is known for his contributions to philosophy of religion, while Nagel, an atheist, is known (nevertheless) for his resistance to purely materialist/naturalist/physicalist theories of the mind (e.g. in his famous article, “What is it like to be a bat?“).

Now Nagel has reviewed Plantinga’s most recent book in the NYRB, giving it a much more sympathetic reading than most naturalists would offer. (For what it’s worth, Plantinga is a supporter of Intelligent Design, and Nagel has often spoken of it approvingly, while not quite buying the whole sales pitch.) Jerry Coyne offers a reasonable dissection of the review.

I wanted to home in on just one particular aspect because it was instructive, at least for me. There is a long-standing claim that “faith” is a way of attaining knowledge that stands independently of other methods, such as “logic” or “empiricism.” I’ve never quite understood this — how do we decide what to have faith in, if not by the use of techniques such as logic and empiricism? …

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Electrical Resistance

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A little while back, an anecdote was being passed around by liberal folks on Facebook that made Ann Romney look pretty bad. Apparently she said that a woman in the workforce “should be happy just to be out there in the working world and quit complaining that she’s not making as much as her male counterparts.” Even by the relatively relaxed standards that are rightfully applied to the families of political candidates rather than the candidates themselves, that sounded a little tone-deaf to me. So I checked on snopes.com and, indeed, found out that the story was completely false. It was made up by a humor site, and then picked up by people who don’t like Romney, who were willing to take it at face value. As ridiculous as any particular claim may be, confirmation bias nudges us toward greater credulity when we are faced with stories that we want to believe are true.

Which brings us to the Chevy Volt, the electric car from General Motors. One of the blogs I generally read is Outside the Beltway, which is a group of conservatives who are more than willing to decry the worst excesses of conservatives as well as liberals. I generally don’t agree with them (except for the decrying), but they say a lot of interesting things. Doug Mataconis, one of the bloggers there, fell quite a bit short of that standard in a recent post about the Volt.

Mataconis, relying on an equally silly Reuters article, tells us that GM loses $50,000 every time it sells a Volt. The attitude of the post is simple — “maybe I’m no fancy businessman, but even I know that it’s not a good strategy to keep building cars and selling them at a tremendous loss!”

Well, that would be a bad strategy. So bad, in fact, that it might be advisable to pull back a bit and ask if that’s what’s actually happening. …

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New Life for Gravitational Waves in Space?

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Last year we brought the bad news that NASA had pulled back from the LISA project, an ambitious proposal to build a gravitational wave detector in space. The science reach of LISA would be amazing, teaching us a great deal about black holes, general relativity, and cosmology.

Fortunately, the European Space Agency did not give up on the idea, and has kept it in the queue of possibilities without actually saying they will do it. They began to design a somewhat down-scaled mission, now dubbed NGO for “New Gravitational wave Observatory.” (Hey, nobody said NASA had a monopoly on dopey acronyms.) NGO was put into the hopper along with two other proposals as part of a selection process to decide on the ESA’s next large-scale mission, dubbed L1 (“L” for “large”), as part of the Cosmic Vision program. It lost out to JUICE, a mission to Jupiter’s moons with admittedly a much cooler acronym as well as some very good science behind it.

But if there is an L1, that implies that someday there might be an L2, and NGO is still in the running to be Europe’s next big mission in astrophysics from space. …

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New Life for Gravitational Waves in Space? Read More »

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