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Time delay

Over the weekend I finished reading The Dark Forest, second book in the Three Body trilogy. The third book is coming out in the fall, so I’m all caught up. Sort of.

The odd thing about all this is that the ending is already well-known (not that I’ve peeked). The trilogy was originally written in Chinese, and published for the Chinese-language market. Only after it was a big success did a publisher agree to hire translators and produce a version for international readers. The third book came out years ago; it’s the translation that’s due this year.

It feels strange to be reading on a time delay, especially one that seems so artificial: couldn’t they have translated all three books and published them together? On the plus side, waiting for the whole trilogy before publishing the first book in English means that the publishers (and Chinese audience) have vetted the last book for me. It can’t be bad!

As for the second, it certainly strikes a different tone from the first. It’s set in the future, first near and then farther, so it’s themes are far less aggressively historical. Instead, it’s a canvas for consideration of abstract ideas and open questions: love, delusion, internationalism, strength of character, the limits of morality. I don’t expect it to win any awards for style, but it does well enough as both a coherent story and a vehicle for consideration of new ideas.

Burying the lede

The LIGO project observed its first gravitational wave within a week of first turning on, but didn’t report it until nine months later. The odds of that event being extremely rare are low … but then the obvious question is: have they observed more since? Had they observed more at the time?

The Boston Globe’s article profiling MIT professor Rainer Weiss includes the answer to this question, buried in a quote at the bottom of the piece:

there seem to be about one of them a month that we can detect

With the exception of Rainer Weiss, the LIGO team must have an incredible poker face, for this not to have leaked for so long … but as I said, it’s also not a surprise.

This is going to be so exciting!


Friday night I went out with some coworkers to Korea-town. We went to a snazzy Korean-inflected burger place hidden in plain sight, on the second floor of a building with a run-down nondescript lobby. Then we went to a food court where American pop music played over Korean music videos, and our dessert stop featured chocolate “dirt” served in an actual miniature flowerpot.

As we walked out onto the sidewalk, someone suggested finishing off with karaoke. Some of us pulled out our phones to look for the nearest karaoke parlor, but one of us just pointed straight up. Sure enough, on the fourth floor directly across the street was a sign for WOW Karaoke, where we rented one of their 5 rooms for an hour.

I’m not saying New York City is always this convenient, but sometimes it really is.

Dear Evan Hansen

A childhood friend of mine is emerging as a Big Deal in the world of musical theatre, and his latest production is Dear Evan Hansen, a heartfelt musical about high school students who feel like outcasts. I couldn’t have seen it without this inside connection: the current run (off-broadway at the Second Stage Theater) is sold out.

As a drama set in the present-day reality of high school life, Dear Evan Hansen necessarily begins on a computer screen, and most of its arc is intertwined with social media. At least 4 laptops appear onstage. (In retrospect, the use of laptops instead of smartphones suggests an earlier setting, as does the Trapper Keeper on the nightstand, but never mind.)

The set is essentially all black, save for a disc representing the current room that can roll in or out as needed. In the opening scene, Evan is sitting on his bed, on the disc, typing on his laptop. As he types, imagery representing his screen appears in glowing form across the stage behind him, courtesy of a suite of high-powered projectors. In the upper left corner of the stage, the words “Microsoft Word” appear, along with the menus and controls of an actual MS Word window, but broken across different set components in a way that makes it easy to identify but hard to read.

The rest of the show builds on this mechanism, pulling in user interface elements from Facebook, Twitter, YouTube, Kickstarter, and more, sometimes with stark clarity, but often shifting, overlapping, or blurred into dizziness. This is the world we inhabit, and so the actors literally play out their drama from inside an all-encompassing computer screen.

I’ve never seen anything like it, and I think it raises the bar for plays set in the present.

As for the music, I’ve definitely heard the like before. It’s a classic modern Broadway soundtrack with strings and electric guitar, full of moving ballads, solo and ensemble pieces, songs that move the story forward and don’t leave a dry eye in the house. Apart from one odd number that works too hard to merge two heavy-handed metaphors for father-son bonding, it’s a killer cast album waiting to happen.

Considering the theme, Dear Evan Hansen seems like a natural fit for adventurous high school drama programs looking for material that speaks to the teenage experience, like Runaways a generation ago. On closer inspection, that won’t be so easy. For one thing, the production relies heavily on the star, Ben Platt, who proves incredible stamina by delivering the vast majority of the songs, somehow combining soaring power notes with a tone that ranges from shy to mortified. The cast is small, no big dance numbers or choruses to fill up with all your B students. And then there’s the set, which is still out of reach for tight school drama budgets.

I hope the show’s creators get a chance to create a version that works around these issues. Even a slightly less compelling version of the show would be much more meaningful in a high school than “Into the Woods” or “Guys and Dolls”.

Lepton number and gravitational waves

When I was in college, Gerhard ‘t Hooft (a Nobel-prize winning physicist) came to speak, and gave a lecture on black hole evolution (I think based on this paper). I didn’t have the education to really understand it, and I still don’t, but what I got out of it was

  • Hawking radiation is a semiclassical approximation
  • A black hole in a box should be coherent, just like Schrodinger’s Cat
  • Therefore Hawking radiation is really just the stuff that went in to the black hole coming back out, after a lot of interactions

This felt right to me. Call it parsimonious: if you can explain all expected black hole behaviors within the existing laws of physics, then that’s probably the right answer. It does, however, force you to throw out the no-hair theorem, which states that black holes are a perfect billiard ball, smooth and free of history. That might be true in General Relativity, but it can’t be true in coherent quantum gravity.

One interesting side effect of this approach is that all the various conservation laws should apply: not just the classical ones like conservation of energy, momentum, and charge, but also quantum ones like color charge, weak isospin, baryon number (i.e. # of quarks), and lepton number (~# of electrons).

This is not normally a problem. We can simply demand that the Hawking radiation spit out the same proportions of stuff that went in in the first place. No Big Deal.

A few months ago, the first gravitational wave detection was announced. A billion light-years away, a 36-solar-mass black hole merged with a 29-solar-mass black hole, in a collision so dramatic that 3 solar masses of energy were radiated away as gravitational waves, leaving a 62-solar-mass black hole behind, spinning rapidly. Conservation of mass/energy, check. Conservation of angular momentum, check.

But what about baryon number? Ordinary matter falling into the black hole is almost entirely baryonic by mass, insofar as it’s mostly protons and neutrons. Five percent of the mass was lost to gravitational waves. That means the Hawking radiation would have to produce the same number of baryons, at a 5% discount on mass! If the Hawking radiation is protons and neutrons as seems natural, then this is simply impossible. The mass of a proton (or neutron) is a constant.

I can think of several ways to resolve this problem, all of which seem implausible.

The baryons could come out bound in low-mass configurations The lowest-mass configuration known is Iron-56, which has a 1% mass discount … not even close to enough. The only known way to pack more baryons into less mass is to spit out an entire gravitationally bound neutron star … which would be an awfully big piece of Hawking radiation!

We could assume that at least 5% of the mass was contributed by the kinetic energy of infalling particles. This is probably true … but it doesn’t seem like there’s any reason it has to be true. If we carefully fed two black holes with low-speed baryons, would they then not be able to radiate gravitational waves upon colliding? That would be extremely weird, a gross violation of general relativity.

It turns out that baryon number may not be conserved. However, most existing theories assume some similar conservation laws. Even if baryons can be converted into leptons, the finite mass of the lightest lepton (neutrinos) means that proton-fed black holes will still run into this problem if they radiate enough of their mass into gravitational waves. Sure, it’s unlikely, but it still doesn’t seem like an expected limit. Moreover, the validity of quantum coherence and general relativity shouldn’t depend on the fine details of high-energy conservation laws!

Finally, we could postulate that baryon number or other quantum numbers could be carried away by the gravitational waves themselves. If the wave were absorbed by another black hole, it could even transfer the quantum number into that black hole, for eventual re-emission. This is the most beautiful solution … but also the weirdest. Firstly, this is weird because all existing quantum gravity theories assume a simple massless graviton as the force carrier. How do you encode a baryon or lepton number into a graviton!? Secondly, this is weird because essentially all gravitational wave mass energy will radiate to infinity, dissipating and redshifting with expansion. Where did the baryons go? You can’t redshift the mass of a proton!

I must be misunderstanding ‘t Hooft, but I’m not sure how. (I certainly can’t decipher the paper!)

I wonder if anyone else has thought about this.

The Man Who Knew Something

I saw The Man Who Knew Infinity on opening night Friday. It’s a biopic of Ramanujan, ostensibly. Ramanujan’s mathematical genius has been a staple of the sort of pop science that I’ve been reading since I was a kid, so I was glad to see his story reaching a larger audience.

The plot of the movie is almost indistinguishable from Ramanujan’s Wikipedia entry, with the exception of some extremely fishy subplots involving an almost comically evil mother-in-law, and his young beautiful bride (who in reality was 10 years old when she was married to the 22-year-old Ramanujan. Yikes.).

Ramanujan is the title character, but in the century-long cult of Ramanujan he is always described as unknowable, far beyond ordinary minds, and focused entirely on mathematics to the exclusion of all else. The movie doesn’t really try to resolve this, mostly leaving Ramanujan as an exotic object to be run through a social and academic wringer.

Instead, the movie becomes a biopic of G. H. Hardy, the relatable (if curmudgeonly) British mathematician who becomes Ramanujan’s mentor. By word count, it’s more a biopic of Hardy than of Ramanujan. Luckily, Jeremy Irons plays a subtle and wonderfully entertaining Hardy.

I might wish for some real insight into the soul of Ramanujan, something deeper than just wondering at the mystery of his amazing results. Instead, what I got was a decent portrait of Cambridge University in the midst of World War I, as measured by the reflections of Ramanujan’s splash.

I’ll take it.

James Webb Space Telescope Live!

You can watch the assembly of the James Webb Space Telescope live:

This week they’re taking off the mirror covers.

I don’t really know much about Webb, but a super-cooled origami-folding space telescope the size of a badminton court seems like it’s worth a look.