Wednesday, March 14, 2018

Stephen Hawking dies at 76. What was he famous for?

I woke up this morning to the sad news that Stephen Hawking has died. His 1988 book “A Brief History of Time” got me originally interested in physics, and I ended up writing both my diploma thesis and my PhD thesis about black holes. It is fair to say that without Hawking my life would have been an entirely different one.

While Hawking became “officially famous” with “A Brief History of Time,” among physicists he was more renowned for the singularity theorems. In his 1960s work together with Roger Penrose, Hawking proved that singularities form under quite general conditions in General Relativity, and they developed a mathematical framework to determine when these conditions are met.

Before Hawking and Penrose’s work, physicists had hoped that the singularities which appeared in certain solutions to General Relativity were mathematical curiosities of little relevance for physical reality. But the two showed that this was not so, that, to the very contrary, it’s hard to avoid singularities in General Relativity.

Thanks to this seminal work, physicists understood that the singularities in General Relativity signal the theory's breakdown in regions of high energy-densities. In 1973, together with George Ellis, Hawking published the book “The Large Scale Structure of Space-Time” in which they laid out the mathematical treatment in detail. Still today it’s one of the most relevant references in the field.

A somewhat lesser known step in Hawking's career is that  already in 1971 he wrote one of the first papers on the analysis of gravitational wave signals. In this paper together with Gary Gibbons, the authors proposed a simple yet path-leading way to extract signals from the background noise.

Also Hawking’s – now famous – area theorem for black holes stemmed from this interest in gravitational waves, which is why the paper is titled “Gravitational Radiation from Colliding Black Holes.” This theorem shows that when two black hole horizons merge their total surface area can only increase. In that, the area of black hole horizons resembles the entropy of physical systems.

Only a few years later, in 1974, Hawking published a seminal paper in which he demonstrates that black holes give off thermal radiation, now referred to as “Hawking radiation.” This evaporation of black holes results in the black hole information loss paradox which is still unsolved today. Hawking’s work demonstrated clearly that the combination of General Relativity with the quantum field theories of the standard model spells trouble. Like the singularity theorems, it’s a result that doesn’t merely indicate, but prove that we need a theory of quantum gravity in order to consistently describe nature.

While the 1974 paper was predated by Bekenstein’s finding that black holes resemble thermodynamical systems, Hawking’s derivation was the starting point for countless later revelations. Thanks to it, physicists understand today that black holes are a melting pot for many different fields of physics – besides general relativity and quantum field theory, there is thermodynamics and statistical mechanics, and quantum information and quantum gravity. Let’s not forget astrophysics, and also mix in a good dose of philosophy. In 2017, “black hole physics” could be a subdiscipline in its own right – and maybe it should be. We owe much of this to Stephen Hawking.

In the 1980s, Hawking worked with Jim Hartle on the no-boundary proposal according to which our universe started in a time-less state. It’s an appealing idea whose time hasn’t yet come, but I believe this might change within the next decade or so.

After this, Hawking tried several times to solve the riddle of black hole information loss that he posed himself, alas, unsuccessfully. It seems that the paradox he helped create finally outlived him.

Besides his scientific work, Hawking has been a master of science communication. In 1988, “A Brief History of Time” was a daring book about abstract ideas in a fringe area of theoretical physics. Hawking, to everybody’s surprise, proved that the public has an interest in esoteric problems like what happens if you fall into a black hole, what happed at the Big Bang, or whether god had any choice when he created the laws of nature.

Since 1988, the popular science landscape has changed dramatically. There are more books about theoretical physics than ever before and they are more widely read than ever before. I believe that Stephen Hawking played a big role in encouraging other scientists to write about their own research for the public. It certainly was an inspiration for me.

Good bye, Stephen, and thank you.

Tuesday, March 13, 2018

The Multiworse Is Coming

You haven’t seen headlines recently about the Large Hadron Collider, have you? That’s because even the most skilled science writers can’t find much to write about.

There are loads of data for sure, and nuclear physicists are giddy with joy because the LHC has delivered a wealth of new information about the structure of protons and heavy ions. But the good old proton has never been the media’s darling. And the fancy new things that many particle physicists expected – the supersymmetric particles, dark matter, extra dimensions, black holes, and so on – have shunned CERN.

It’s a PR disaster that particle physics won’t be able to shake off easily. Before the LHC’s launch in 2008, many theorists expressed themselves confident the collider would produce new particles besides the Higgs boson. That hasn’t happened. And the public isn’t remotely as dumb as many academics wish. They’ll remember next time we come ask for money.

The big proclamations came almost exclusively from theoretical physicists; CERN didn’t promise anything they didn’t deliver. That is an important distinction, but I am afraid in the public perception the subtler differences won’t matter. It’s “physicists said.” And what physicists said was wrong. Like hair, trust is hard to split. And like hair, trust is easier to lose than to grow.

What the particle physicists got wrong was an argument based on a mathematical criterion called “naturalness”. If the laws of nature were “natural” according to this definition, then the LHC should have seen something besides the Higgs. The data analysis isn’t yet completed, but at this point it seems unlikely something more than statistical anomalies will show up.

I must have sat through hundreds of seminars in which naturalness arguments were repeated. Let me just flash you a representative slide from a 2007 talk by Michelangelo L. Mangano (full pdf here), so you get the idea. The punchline is at the very top: “new particles must appear” in an energy range of about a TeV (ie accessible at the LHC) “to avoid finetuning.”

I don’t mean to pick on Mangano in particular; his slides are just the first example that Google brought up. This was the argument why the LHC should see something new: To avoid finetuning and to preserve naturalness.

I explained many times previously why the conclusions based on naturalness were not predictions, but merely pleas for the laws of nature to be pretty. Luckily I no longer have to repeat these warnings, because the data agree that naturalness isn’t a good argument.

The LHC hasn’t seen anything new besides the Higgs. This means the laws of nature aren’t “natural” in the way that particle physicists would have wanted them to be. The consequence is not only that there are no new particles at the LHC. The consequence is also that we have no reason to think there will be new particles at the next higher energies – not until you go up a full 15 orders of magnitude, far beyond what even futuristic technologies may reach.

So what now? What if there are no more new particles? What if we’ve caught them all and that’s it, game over? What will happen to particle physics or, more to the point, to particle physicists?

In an essay some months ago, Adam Falkowski expressed it this way:
“[P]article physics is currently experiencing the most serious crisis in its storied history. The feeling in the field is at best one of confusion and at worst depression”
At present, the best reason to build another particle collider, one with energies above the LHC’s, is to measure the properties of the Higgs-boson, specifically its self-interaction. But it’s difficult to spin a sexy story around such a technical detail. My guess is that particle physicists will try to make it sound important by arguing the measurement would probe whether our vacuum is stable. Because, depending on the exact value of a constant, the vacuum may or may not eventually decay in a catastrophic event that rips apart everything in the universe.*

Such a vacuum decay, however, wouldn’t take place until long after all stars have burned out and the universe has become inhospitable to life anyway. And seeing that most people don’t care what might happen to our planet in a hundred years, they probably won’t care much what might happen to our universe in 10100 billion years.

Personally I don’t think we need a specific reason to build a larger particle collider. A particle collider is essentially a large microscope. It doesn’t use light, it uses fast particles, and it doesn’t probe a target plate, it probes other particles, but the idea is the same: It lets us look at matter very closely. A larger collider would let us look closer than we have so far, and that’s the most obvious way to learn more about the structure of matter.

Compared to astrophysical processes which might reach similar energies, particle colliders have the advantage that they operate in a reasonably clean and well-controlled environment. Not to mention nearby, as opposed to some billion light-years away.

That we have no particular reason to expect the next larger collider will produce so-far unknown particles is in my opinion entirely tangential. If we stop here, the history of particle physics will be that of a protagonist who left town and, after the last street sign, sat down and died, the end. Some protagonist.

But I have been told by several people who speak to politicians more frequently than I that the “just do it” argument doesn’t fly. To justify substantial investments, I am told, an experiment needs a clear goal and at least a promise of breakthrough discoveries.

Knowing this, it’s not hard to extrapolate what particle physicists will do next. We merely have to look at what they’ve done in the past.

The first step is to backpedal from their earlier claims. This has already happened. Originally we were told that if supersymmetric particles are there, we would see them right away.
“Discovering gluinos and squarks in the expected mass range […] seems straightforward, since the rates are large and the signals are easy to separate from Standard Model backgrounds.” Frank Paige (1998).

“The Large Hadron Collider will either make a spectacular discovery or rule out supersymmetry entirely.” Michael Dine (2007)
Now they claim no one ever said it would be easy. By 2012, it was Natural SUSY is difficult to see at LHC and “"Natural supersymmetry" may be hard to find.” 

Step two is arguing that the presently largest collider will just barely fail to see the new particles but that the next larger collider will be up to the task.

One of the presently most popular proposals for the next collider is the International Linear Collider (ILC), which would be a lepton collider. Lepton colliders have the benefit of doing away with structure functions and fragmentation functions that you need when you collide composite particles like the proton.

In a 2016 essay for Scientific American Howard Baer, Vernon D. Barger, and Jenny List kicked off the lobbying campaign:
“Recent theoretical research suggests that Higgsinos might actually be showing up at the LHC—scientists just cannot find them in the mess of particles generated by the LHC's proton-antiproton collisions […] Theory predicts that the ILC should create abundant Higgsinos, sleptons (partners of leptons) and other superpartners. If it does, the ILC would confirm supersymmetry.”
The “recent theoretical research” they are referring to happens to be that of the authors themselves, vividly demonstrating that the quality standard of this field is currently so miserable that particle physicists can come up with predictions for anything they want. The phrase “theory predicts” has become entirely meaningless.

The website of the ILC itself is also charming. There we can read:
“A linear collider would be best suited for producing the lighter superpartners… Designed with great accuracy and precision, the ILC becomes the perfect machine to conduct the search for dark matter particles with unprecedented precision; we have good reasons to anticipate other exciting discoveries along the way.”
They don’t tell you what those “good reasons” are because there are none. At least not so far. This brings us to step three.

Step three is the fabrication of reasons why the next larger collider should see something. The leading proposal is presently that of Michael Douglas, who is advocating a different version of naturalness, that is naturalness in theory space. And the theory space he is referring to is, drums please, the string theory landscape.

Naturalness, of course, has always been a criterion in theory-space, which is exactly why I keep saying it’s nonsense: You need a probability distribution to define it and since we only ever observe one point in this theory space, we have no way to ever get empirical evidence about this distribution. So far, however, the theory space was that of quantum field theory.

When it comes to the landscape at least the problem of finding a probability distribution is known (called “the measure problem”), but it’s still unsolvable because we never observe laws of nature other than our own. “Solving” the problem comes down to guessing a probability distribution and then drowning your guess in lots of math. Let us see what predictions Douglas arrives at:

Slide from Michael Douglas. PDF here. Emphasis mine.

Supersymmetry might be just barely out of reach of the LHC, but a somewhat larger collider would find it. Who’d have thought.

You see what is happening here. Conjecturing a multiverse of any type (string landscape or eternal inflation or what have you) is useless. It doesn’t explain anything and you can’t calculate anything with it. But once you add a probability distribution on that multiverse, you can make calculations. Those calculations are math you can publish. And those publications you can later refer to in proposals read by people who can’t decipher the math. Mission accomplished.

The reason this cycle of empty predictions continues is that everyone involved only stands to benefit. From the particle physicists who write the papers to those who review the papers to those who cite the papers, everyone wants more funding for particle physics, so everyone plays along.

I too would like to see a next larger particle collider, but not if it takes lies to trick taxpayers into giving us money. More is at stake here than the employment of some thousand particle physicists. If we tolerate fabricated arguments in the scientific literature just because the conclusions suit us, we demonstrate how easy it is for scientists to cheat.

Fact is, we presently have no evidence –  neither experimental nor theoretical evidence –  that a next larger collider would find new particles. The absolutely last thing particle physicists need right now is to weaken their standards even more and appeal to multiversal math magic that can explain everything and anything. But that seems to be exactly where we are headed.

* I know that’s not correct. I merely said that’s likely how the story will be spun.

Like what you read? My upcoming book “Lost in Math” is now available for preorder. Follow me on twitter for updates.

Saturday, March 10, 2018

Book Update: German Cover Image

My US publisher has transferred the final manuscript to my German publisher and the translation is in the making. The Germans settled on the title “Das Hässliche Universum” (The Ugly Universe). They have come up with a cover image that leaves me uncertain whether it’s ugly or not which I think is brilliant.

New Scientist, not entirely coincidentally, had a feature last week titled “Welcome To The Uglyverse.” The article comes with an illustration showing the Grand Canyon clogged by an irregular polyhedron in deepest ultramarine. It looks like a glitch in the matrix, a mathematical tumor on nature’s cheek. Or maybe a resurrected povray dump file. Either way, it captures amazingly well how artificial the theoretical ideals of beauty are. It is also interesting that both the designer of the German cover and the designer of the New Scientist illustration chose lack of symmetry to represent ugliness.

The New Scientist feature was written by Daniel Cossins, who did an awesome job explaining what the absence of supersymmetric particles has to do with the mass of the Higgs and why that’s such a big deal now. It’s one of the topics that I explore in depth in my book. If you’re still trying to decide whether the book is for you, check out the New Scientist piece for context.

Speaking of images, the photographer came and photographed, so here is me gazing authorly into the distance. He asked me whether the universe is random. I said I don’t know

Tuesday, March 06, 2018

Book Review: “Richie Doodles,” a picture book about Richard Feynman by M. J. Mouton and J. S. Cuevas

Richie Doodles: The Brilliance of a Young Richard Feynman
Rare Bird Books (February 20, 2018)

I’m weak. I have a hard time saying “no” when offered a free book. And as the pile grows, so does my guilt for not reading them. So when I was offered a free copy of a picture book about Richard Feynman, of course I said “yes.” I’d write some nice words, work off some guilt, and everyone would be happy. How hard could it be?

So the book arrived and I handed it to the twins, that being my great plan reviewing a children’s book. I don’t think the kids understood why someone would give them a book for free just to hear whether they liked it, but then I’m not entirely sure I understand the review business myself.

In any case, my zero-effort review failed at the first hurdle, that being that the book is in English but the twins barely just read German. So “mommy, read!” it was. Except that of course reading wouldn’t have done because, a thousand hours of Peppa Pig notwithstanding, they don’t understand much English either.

I am telling you this so you can properly judge the circumstances under which this, cough, review was conducted. It was me translating English verse on the fly. Oh, yes, the book is in verse. Which you might find silly but I can attest, that seven year olds think it’s the best.

The translation problem was fairly easy to solve – I even managed a rhyme here and there – but the next problem wasn’t. Turns out that the book doesn’t have a plot. It is a series of pictures loosely connected to the text, but it has no storyline. At least I couldn’t find one. There’s a dog named “Hitch” which appears throughout the “Tiny Thinkers” series (so far three books), but the dog is not present on most pages. And even if it’s on the page, it’s not clear why or what it’s doing.

That absence of story was some disappointment. Not like first-graders are demanding when it comes to storytelling. “The dog stole the doodle and the cat found it” would have done. But no plot.

Ok, well, so I made up a plot. Something along the lines that everyone thought Richie was just crazy doing all the doodles but turned out he was a genius. No, I don’t plan making career with this.

The next problem I encountered is that the illustrations are as awesome as the text isn’t. They are professionally done cartoon-style drawings (four-fingered hands and all) with a lovely attention to detail. The particular headache they gave me is that in several images a girl appears and, naturally, my daughters were much more interested in who the girl is and what she is doing rather than what the boy’s squiggly lines have to do with tau neutrinos. Maybe Richie’s sister? The book leaves one guessing.

The final problem appeared on the concluding page, where we see an angry looking (female) math teacher reprimanding a very smug looking boy (we aren’t told who that is) for drawing doodles instead of paying attention to the teacher. The text says “If your teacher sees you doodling in class, and says those silly drawings won’t help you pass… You can explain that your doodle isn’t silly at all. It’s called a Feynman Diagram explaining things that are small.”

I wasn’t amused. Please understand. I have a degree. I can’t possibly tell my kids it’s ok to ignore their math teacher because maybe their drawings will one day revolutionize the world.

So I turned this into an explanation about how math isn’t merely about numbers and calculus, but more generally about relations that can, among others, be represented by drawings. I ended up giving a two-hour lecture on braid groups and set theory.

The book finishes with some biographical notes about Feynman.

On Amazon, the book is marked for Kindergardners, age 4-6. But to even make sense of the images, the children need to know what an atom is, what mathematics is, and what a microscope is. The text is even more demanding: It contains phrases like “quark and antiquark pair” and speaks of particles that repel or attract, and so on.

Because of this I’d have guessed the book is aimed at children age 7 to 10. Or maybe more specifically at children of physicists. Of course I don’t expect a picture book to actually explain how Feynman diagrams work, but the text in the book is so confused I can’t see how a child can make sense of it without an adult who actually knows that stuff.

At some point, for example, the text raises the impression that all particles pass through matter without interaction. “Things so small they pass right through walls!” You have to look at the illustration on the opposite page to figure out this refers only to neutrinos (which are not named in the text). If you don’t already know what neutrinos are, you’ll end up very confused which collisions the later pages refer to.

Another peculiar thing about the book is that besides the “doodles” it says pretty much nothing about Richard Feynman. Bongo drums appear here and there but are not mentioned in the text. A doodle-painted van can be spotted, but is only referred to in the biography. There is also what seems to be an illustration of Schrödinger’s cat experiment and later a “wanted” poster looking for the cat “dead or alive.” Cute, yes, but that too is disconnected from the text.

I got the impression the book is really aimed at children of physicists – or maybe just physicists themselves? – who can fill in the details. And no word of lock-picking!

As you can tell, I wasn’t excited. But then the book wasn’t for me. When I asked the girls for their impression, they said they liked the book because it’s “funny.” Further inquiry revealed that what’s funny about the book are the illustrations. There’s a dog walking through a bucket of paint, leaving behind footprints. That scored highly, let me tell you. There’s a car accident (a scattering event), an apple with a worm inside, and a family of mice living in a hole in the wall. There are also flying noodles and even I haven’t figured out what those are, which made them the funniest thing in the world ever, at least for what my children are concerned.

The book has a foreword by Lawrence Krauss, but since Krauss recently moved to the sinner’s corner, that might turn out to be more of a benefit for Krauss than for the book.

In summary, the illustrations are awesome, the explanations aren’t.

I feel like I should be grateful someone produces children’s books about physics at all. Then again I’m not grateful enough to settle for mediocrity.

Really, why anyone asks me to review books is beyond me.

Thursday, March 01, 2018

Who is crazy now? (In which I am stunned to encounter people who agree with me that naturalness is nonsense.)

I have new front teeth. Or rather, I have a new dentist who looked at the fixes and patches his colleagues left and said they’ve got to go. Time for crowns. Welcome to middle age.

After several hours of unpleasant short-range interactions with various drills, he puts on the crowns and hands me a mirror. “Have a look,” he says. “They’re tilted,” I say. He frowns, then asks me to turn my head this way and that way. “Open your mouth,” he says, “Close. Open.” He grabs my temples with a pair of tongs and holds a ruler to my nose. Then he calls the guy from the lab.

The lab guy shakes my hand. “What’s up?” he asks. “They crowns are tilted,” I say. He stares into my mouth. “They’re not,” he declares and explains he made them personally from several impressions and angle measurements and photos. He uses complicated words that I can’t parse. He calls for his lab mate, who confirms that the crowns are perfectly straight. It’s not the crowns, they say, it’s my face. My nose, I am told, isn’t in the middle between my pupils. I look into the mirror again, thinking “what-the-fuck,” saying “they’re tilted.”

Now three guys are staring at my teeth. “They’re not tilted,” one of them repeats. “Well,” I try a different take “They don’t have the same angle as they used to.” “Then they were tilted before,” one of them concludes. I contemplate the possibility that my teeth were misaligned all my life but no one ever told me. It seems very possible. Then again, if no one told me so far chances are no one ever will. “They’re tilted,” I insist.

The dentist still frowns. He calls for a colleague who appears promptly but clearly dismayed that her work routine was interrupted. I imagine a patient left behind, tubes and instruments hanging out of the mouth. “Smile,” she orders. I do. “Yes, tilted,” she speaks, turns around and leaves.

For a moment there, I felt like the participants in Asch’s famous 1951 experiment. Asch assigned volunteers to join a group of seven. The group was tasked with evaluations of simple images which they were told were vision tests. The volunteers did not know that the other members of the group had been given instructions to every once in a while all judge a longer of two lines as the shorter one, though the answer was clearly wrong. 75 percent of the trial participants went with the wrong majority opinion at least once.

I’d like to think if you’d put me among people who insisted the shorter line is the longer one, I’d agree with them too. I also wouldn’t drink the water, keep my back to the wall, and leave the room slowly while mumbling “Yes, you are right, yes, I see it clearly now.”

In reality, I’d probably conclude I’m crazy and then go write a book about it. Because that’s pretty much what happened.

For more than a decade I’ve tried to find out why so many high energy physicists believe that “natural” theories are more likely to be correct. “Naturalness,” here, is mathematical property of theories which physicists use to predict new particles or other observable consequences. Particle physicists’ widespread conviction that natural theories were preferable was the reason so many of them thought the Large Hadron Collider would see something new besides the Higgs boson: Supersymmetry, dark matter, extra dimensions, black holes, gravitons, or other exotic things.

Whenever I confessed to one of my colleagues I am skeptical that naturalness is a reliable guide, I was met with a combination of amusement and consternation. Most were nice. They explained things to me that I already knew. They didn’t answer my questions but insisted they did. Some gave up and walked away. Others got annoyed. Every once in a while someone told me I’m just stupid. All of them ignored me.

After each conversation I went and looked again at the papers and lecture notes and textbooks, but each time I arrived at the same conclusion, that naturalness is an argument from beauty, based on experience but with scant empirical evidence. For all I could tell, that a theory be natural was a wish not a prediction. I failed to see a reason for the LHC to honor this wish.

And it didn’t. The predictions for the LHC that were based on naturalness arguments did not come true. At least not so far, and we are nearing the end of new data. Gian-Francesco Giudice, head of the CERN theory division, recently rang in the post-naturalness era. Confusion reigns among particle physicists.

A few months have passed since Giudice’s paper. I am sitting at a conference in Aachen on naturalness and finetuning where I am scheduled to give my speech about how naturalness is a criterion of beauty, as prone to error as criteria of beauty have always been in the history of science. It’s a talk usually met with  befuddlement. Questions I get are mostly alterations of “Did you really just say what I thought you said?”

But this time it’s different. One day into the conference I notice that all I was about to say has already been said. The meeting, it seems, collected the world’s naturalness skeptics, a group of likeminded people I didn’t know exists. And they are getting more numerous by the day.

Most here agree that naturalness is not a reliable guide but a treacherous one, one that looks like it works until suddenly it doesn’t. And though we don’t agree on the reason why this guide failed just now and what to do about it, I’m not the crazy one any more. Several say they are looking forward to reading my book.

The crowns went back to the lab. Attempts at fixing them failed, and the lab remade them entirely. They’re straight now, and I am no longer afraid that smiling will reveal the holes between my teeth.