Monday, April 23, 2018


I am giving (another) seminar in Heidelberg on Wednesday (April 25th), this time about my upcoming book.

May 1st is a national holiday in Germany (labor day) and I’ll be off-grid due to family affairs for some days.

May 7th to 9th I am in Stockholm to get yelled at (it’s complicated).

On May 26th I am in Hay-on-Wye which is a village someplace UK that hosts an event called How The Light Gets In at which I am supposed to debate how “the pursuit of beauty drive[s] the evils that hold back a better society.” I wouldn’t go as far as calling grand unification an evil, so please don’t judge me by the tagline.

I have also been asked to share this image below. Hope it makes more sense to you than to me.

On May 28th I am giving a public lecture in Dublin at the Irish Quantum Foundations conference.

In summary this means May will be a very slow month on this blog.

Wednesday, April 18, 2018

Guest Post: Brian Keating about his book “Losing the Nobel Prize"

My editor always said “Don’t read reviews”... But given that I’ve received some pretty amazing reviews lately, how bad could it be? Nature even made a delightfully whimsical custom-illustration of my conjecture: that some of my fellow astronomers look to the skies for the Nobel Prize:

Illustration by Stephan Schmitz for Nature.

When I saw Sabine had finally gotten round to reading my book, I was thrilled! This is sure to be an awesome review from a fellow-traveller: a first-time author herself.

Gulp. After reading Sabine’s blog, I immediately regretted not taking my editor’s advice. But, Sabine was kind enough to offer me a chance to reply to her review (a review of a review?) so here goes.

First off, speaking of not reading things, the cover of the version I sent to Sabine explicitly says “don’t quote without checking against the final version” (See the white cover version in the upper left hand corner of this photograph on Medium).

Unfortunately, Sabine never read the finished version. In fact, the few times I asked her about her progress reading the “ADVANCE UNCORRECTED” review copy’ book sent to her in August, she only replied “I’ve not started it”. Fair enough, she was writing her own book about things being Lost. And she did pass it on to a German publisher on my behalf, which was terribly kind of her.

But the version Sabine read was not even proof-read, nor copyedited, nor fact-checked. Right on the cover it implores the reader to “not quote for publication without checking against the finished book”. This is something she, as an author, probably should have realized before writing her review. I’ve reviewed multiple books for fellow physicists long before writing my own -- as has she -- and always make sure to cross-check against the final version(s) [plural because often I’ve read and listened to the audio book before writing my review].

[[SH: I quoted a single sentence, and I assume that sentence is still in the book because otherwise hed have rubbed it in by now.]]

But, what about the substance of her review? Well, much of what’s inaccurate about it stems from unwarranted or incorrect assumptions. For example, she complains that I did not inquire as to what “Swedish Royal Academy has to say about the reformation plans”.

First of all, I’m not sure how she could possibly know with whom I’ve been in communication with...she’s not Zuckerberg!

[[SH: I guessed that much from my exchange with him, and reading the book confirmed it because if he had been in touch with them he’d have mentioned it.]]

Secondly, not only did I seek (and receive permissions from the Swedish Academy), I corresponded with a member of the Swedish Academy...and they agreed with my proposal:

“Thanks for sending me your interesting piece in the Scientific American. Although I, for obvious reasons, cannot comment on any details concerning the Nobel prize, I can assure you that all the points that were rised [sic] in your article are actively discussed in the Committee and the Academy, and have been so for a long time. We are acutely aware of both challenges and difficulties related to revising the self-imposed rules for how the prize is awarded. We also very much welcome debate about these issues, so I thank you for caring about the future of the Nobel prize, and I will forward you article to the other members of the committee.

How’s that for seeing what “they have to say”?

[[SH: I was the one who got Brian in contact with the above quoted member of the Swedish Academy after it became clear to me that Brian had not bothered communicating them.]]

Some of this appears in the final book version.

[[SH: I am so happy I could be of help.]]

And all of this I would have been happy to share with Sabine...had she asked. I was gratified to see that my concerns were shared by them and that they had not, as Sabine asserted, ignored my ideas: “I’d be surprised if the Royal Academy even bothers responding to Keating’s book.”

I agree with her: I’m not convinced anything will come of it...until the day the Nobel Prize in physics is boycotted or sued. And I think that day is coming.

Why? It relates to two objections Sabine raised early in her review:

“I have found Keating’s book outright perplexing. To begin with let us note that the Nobel Prize is not a global community award. It’s given out by a Swedish committee tasked with executing the will of a very dead man.”

It really not that perplexing, Sabine. The Nobel Prize is a global event, not just a simple Swedish smorgasbord. The prize for peace, for example, is for world peace, not merely to implore Norsemen to stop making war with their many conniving enemies, right?

Fact: According the Nobel Foundation, 100 million people tune into the festivities each year...ten times the population of Sweden and about 10% of the audience the Oscars receive. Winners become celebrities and the Nobel Committees revel in the fame and adoration the events receive.

Why, they’re even moving into a brand, spanking new $150M building in Stockholm next year, designed by a fancy architecture firm, for all their many festivities (the old venue is too small apparently).

The winners are disproportionately non-Scandinavian and the prize aims to reward those who have benefitted “all mankind”, not just Swedes. In fact, the prize for literature is currently undergoing a bonafide sex scandal:

“STOCKHOLM — A sexual abuse and harassment scandal roiling the committee that awards the Nobel Prize in Literature deepened on Wednesday, as the king of Sweden and the foundation that finances the prize warned that the scandal risked tarnishing one of the world’s most important cultural accolades.” [emphasis mine]

The Nobel Prize leaders and the King recognize the power of the prize. It is not only science’s greatest accolade, it’s the greatest one humanity has to offer as well. As such it should be held to a higher standard.

With respect to the many comments others have made about me having sour grapes, no one who reads the book could come away thinking I actually still want to win it. Of course, after reading Sabine’s review, many have cancelled their orders so they may never learn!

But even that notwithstanding, I’m often criticized for writing about it without having won the Nobel. I find that a bit silly. Can one not criticize Harvey Weinstein without being an member of the Academy? Can one not criticize President Trump if one has not been president?

As to this snarky bit: “Keating apparently thinks he knows better what Alfred Nobel wanted than Alfred Nobel himself. Maybe he does. I don’t know, my contacts in the afterworld have not responded to requests for comments.”

I resonate with Sabine’s admission that she has no direct lines to the afterworld; neither do I. And that’s the exact purpose of a will, isn’t it? “A last will and testament is a legal document that communicates a person's final wishes pertaining to possessions and dependents

Alfred died without any children or spouse...his will specified what was to be done with the money he made from the (world wide) patent on dynamite. After providing some kroner for his friends, and his nephews and nieces (the nieces got only ½ of what his nephews received...perhaps an early source of the prize’s legendary sexism?), he left money for the titular prizes. Reading the will, we learn:

“The whole of my remaining realizable estate shall be dealt with in the following way: the capital, ...shall be annually distributed in the form of prizes to those who, during the preceding year, shall have conferred the greatest benefit to mankind. ... one part to the person who shall have made the most important discovery or invention within the field of physics…”

One sees three conditions for awarding the prize:

1. The person [in the singular]
2. Who in the Preceding year
3. Conferred “the greatest benefit to mankind”

I don’t need to have clairvoyance into the netherworld because Alfred did it for me. It is abundantly clear what he wanted and all three of these rules are routinely ignored and have been for over a century.

As for the power of the prize to affect the judgement and career choices of scientists, let me just say it affects non-astronomers too: "With physicist Peter Mansfield, Lauterbur in 2003 bested Damadian to Nobel recognition of magnetic resonance imaging (MRI). This outcome prompted the appearance of full-page ads financed by the Friends of Raymond Damadian in a number of newspapers, including The New York Times.” [emphasis mine].

Wherever there is an idol, people will bow down to it, the Nobel is no baal [Warning: another Old Testament reference], but it is no exception either.

As for the pro-experimental bias of my book “Keating for example suggests that the Nobel Prize only be given to “serendipitous discoveries,” by which he means if a theorist predicted it then it’s not worthy.” Sabine, how could you miss the lovely pie chart I made for you and your fellow brainiacs as well as the accompanying text: “A serendipity criterion would mean Nobel Prizes would go to the theorist(s) who predict new phenomena, though they should win only after experimental verification.”

[[SH: He also explains that if a theorist predicted it, then the experimental verification wasn’t serendipitous, so what gives? And yeah, I was about to make a joke about that pie chart but then felt sorry for the graphics designer who probably just did what Brian asked for.]]

In the book I am advocating that more theorists should win it, and experimentalists should not win it if they/we merely confirm a theory...that leaves them/us susceptible to confirmation bias. For reference, this was in the copy Sabine read.

Alas, time is fleeting and the launch of my book is few short days away, so I must take leave of back reacting.

But I am thankful that Sabine has permitted me this chance to address some of her concerns. And I am grateful for the many kind words she did employ in her review. I enjoy your work and I wish you best of luck with your book...may you never read a review you have to react to!

Monday, April 16, 2018

Book Review: “Losing the Nobel Prize” by Brian Keating

Losing the Nobel Prize: A Story of Cosmology, Ambition, and the Perils of Science’s Highest Honor
Brian Keating
W. W. Norton & Company (April 24, 2018)

Brian Keating hasn’t won a Nobel Prize. Who doesn’t know the feeling? But Keating, professor of physics at UC San Diego, isn’t like you and I. He had a good shot at winning. Or at least he thought he had. And that’s what his book is about.

Keating designed the BICEP telescope, whose upgrade – BICEP2 – made headlines in 2014 by claiming the first indirect detection of primordial gravitational waves through B-modes in the cosmic microwave background. Their supposed detection turned out to be contaminated by a foreground signal from dust in the Milky Way and, after a few months, was declared inconclusive. And there went Keating’s Nobel Prize.

In his book, Keating tells the story of the detection and its problems. But really the book is about his obsession to win the Nobel Prize and his ideas for reforming the award’s criteria. That’s because Keating has come to the conclusion that pursuing science to the end of winning a Nobel prize is no good, and he doesn’t want his colleagues to go down the same road. He also doesn’t think it’s fair to hand out the prize for maximally three people (who moreover should be alive) because by his own accounting he’d have been fourth on the list. At best.

“Losing the Nobel Prize” is well written and engaging and has a lot of figures and, ah, here I run out of nice things to say. But we all know you didn’t come for the nice things anyway, so let’s get to the beef.

I have found Keating’s book outright perplexing. To begin with let us note that the Nobel Prize is not a global community award. It’s given out by a Swedish committee tasked with executing the will of a very dead man. Keating apparently thinks he knows better what Alfred Nobel wanted than Alfred Nobel himself. Maybe he does. I don’t know, my contacts in the afterworld have not responded to requests for comments.

In any case, you’d think if someone writes a book about the Nobel Prize they’d hear what the Swedish Royal Academy has to say about the reformation plans. But for all I can tell Keating never even contacted them. His inside knowledge about the Nobel Prize is having been invited to nominate someone.

Keating doesn’t mention it, but the club of those eligible to submit nominations for the Nobel Prize is not very exclusive. Every tenured professor in the Nordic countries (in the respective discipline) can nominate candidates. Right, that’s not very equal opportunity. Fact is the Nobel Prize is unashamedly North European. And North Europeans in general, with Swedes in particular, don’t care whether US Americans like what they do. I’d be surprised if the Royal Academy even bothers responding to Keating’s book.

Even stranger is that Keating indeed seems to believe most scientists pursue their research because they want to win a Nobel Prize. But I don’t know anyone who has ever chosen a research project because they were banking on a Nobel. That’s because at least in my discipline it’s widely recognized that winning this award doesn’t merely require scientific excellence but also a big chunk of luck.

Maybe Keating is right and Nobel obsession is widespread in his own discipline, experimental astrophysics. But no such qualifier appears anywhere in the book. He is speaking for all of science. “Battle is an apt metaphor for what we scientists do.” And according to Keating, it’s not Nature’s reclusiveness that we battle but each other. And it’s all because everyone wants to win the Nobel Prize.

Keating at some point compares the Nobel Prize to Olympic Gold, but that’s a poor comparison. If you wanted to compare the Nobel Prize to say, discus throw, you’d have to let 99.9% of discuses randomly explode right after being thrown. And when that happens you disqualify the athlete.

In my experience, while almost everyone agrees that Nobel Laureates in Physics deserve their prizes, they also acknowledge it matters to be at the right place at the right time. And since everyone knows talent isn’t the only relevant factor to win the Prize, few hold grudges about not winning it. It’s really more a lottery than a competition.

Having said that, even after reading the book I am not sure just how Keating proposes we think about the Nobel Prize. While he uses analogies to athletic competition, he also compares the Nobel Prize with the Oscar and with a religious accolade, depending on what suits his argument. Possibly the reason for my difficulty understanding Keating is that he assumes his readers know what’s the fourth and fifth commandment and what was up with that Golden Calf in the Old Testament. I may know what B-modes are, but that one beat me.

He also lost me at various other places in the book where I just couldn’t figure out what’s going on or why. For example, I guess pretty much everyone who reads the book will know that BICEP failed to measure the signal they were after. Yet the reader has to wait until Chapter 14 to hear what happened there. Chapter 15, then, is titled “Poetry for Physicists,” contains some reflections on how we’re all made of stardust and so on, praises Jim Simons for funding the Simons Observatory, mentions as an aside that Keating will be the Observatory’s director, and ends with a poem about dust. The next chapter is slap back to Nobel’s will and then goes on about the lack of female laureates. If follows an image of Keating’s academic genealogy, and then we are transported into a hospital room to witness his father’s death.

If that sounds confusing it’s because it is. There are so many things in the book that didn’t make sense to me I don’t even know where to begin.

Keating for example suggests that the Nobel Prize only be given to “serendipitous discoveries,” by which he means if a theorist predicted it then it’s not worthy. You read that right. No Nobel for the Higgs, no Nobel for B-modes, and no Nobel for a direct discovery of dark matter (should it ever happen), because someone predicted that. Bad news for theorists I suppose. The culprit here seems to be that Keating (an experimentalist) doesn’t believe theory development has any role to play in experimental design. He just wants rich guys to crank out money so experimentalists can do whatever they want.

The most befuddling aspect of this book, however, is that Keating indeed seems to believe he had a chance of winning the Nobel Prize. But the Nobel Prize committee would have done well not handing out a prize even if BICEP had been successful measuring the signal they were after.

B-mode polarization from primordial gravitational waves would have been an indirect detection of gravitational waves, but there was a Nobel Prize for that already and being second doesn’t count. And in contrast to what Keating states in the book, this detection would not have been evidence for quantum gravity because the measurement wouldn’t have revealed whether the waves were or weren’t quantized.

Neither for that matter, would it have been evidence for inflation. As Keating himself notes in the passing by quoting Steinhardt, models for inflation can predict any possible amount of B-modes. He doesn’t mention it, but I’ll do it for him, that some models without inflation also predict B-modes.

So the claim that B-modes would be evidence for inflation is already wrong. Even worse, Keating repeats the myth that such a detection would moreover be evidence for the multiverse because that just sounds so spectacular. But it doesn’t matter how often you repeat this claim it’s still wrong, and it isn’t even difficult to see why. If you want to make any calculation to predict the B-mode spectrum you don’t need to begin with a multiverse. All you need is some effective theory in our universe. And that theory may or may not have an inflaton.

My point being simply if you don’t need X it to make prediction Y, measuring Y isn’t evidence for X. So, no, B-modes aren’t evidence for the multiverse.

I don’t personally know Brian Keating, but he’s on twitter and he seems to be a nice guy. Also I got this book for free, so I want to warmly recommend you buy it because what else can I say. If nothing else, Keating has a gift for writing. And who knows, his next book might be about not winning a Nobel Prize for Literature.

Tuesday, April 10, 2018

No, that galaxy without dark matter has not ruled out modified gravity

A smear with dots, 
also known as NGC 5264-HST.
Did you really have to ask?

And if you had to ask, why did you have to ask me?

You sent me like two million messages and comments and emails asking what I think about NGC 1052-DF2, that galaxy which supposedly doesn’t contain dark matter. Thanks. I am very flattered by your faith.

But I’m not an astrophysicist, I’m a theorist. I invent equations and then despair over my inability to solve them. That’s what I do. I know about as much about telescopes as penguins know about cacti. And until last week I thought a globular cluster is a kind of glaucoma. (Turns out it’s not.)

But since you ask.

If nothing else, I have the benefit of a university account with subscriptions to all major journals, so at least I could look at the Nature paper in question. We can read there:
“the existence of NGC1052–DF2 may falsify alternatives to dark matter. In theories such as modified Newtonian dynamics (MOND) and the recently proposed emergent gravity paradigm, a ‘dark matter’ signature should always be detected, as it is an unavoidable consequence of the presence of ordinary matter.”
This paragraph is decorated with two references, one of which is to Milgrom’s MOND and one is to Erik Verlinde’s emergent gravity. And, well, I’m a theorist. Therefore I can tell you right away those people don’t know a thing about the theories they try to falsify.

It is beyond me why so many astrophysicists believe that modified gravity is somehow magically different from particle dark matter, or indeed all other theories we have ever heard of. It’s not.

For both modified gravity and particle dark matter you have additional degrees of freedom (call them fields or call them particles) which need additional initial conditions. In a universe in which you have a large variety of initial conditions (seeded by quantum fluctuations), you will get a large variety of structures. Same thing for modified gravity as for particle dark matter.

Another way to put this is that you can always cook up exceptions to the rule. The challenge isn’t to explain the exception. The challenge is to explain the rule. Modified gravity does that. Particle dark matter doesn’t.

Of course you don’t see the exceptions in Milgrom’s or in Verlinde’s paper. The reason is that both merely contain equations which describe time-independent situations. These equations derived in Milgrom’s and Verlinde’s papers are not theories, they are certain limits of theories, approximations that work in some idealized circumstances, such as equilibrium. The full theories are various types of “modified gravity” and if you want to rule those out, you better find out what they predict first.

But we don’t even have to stoop so low. Because, interestingly enough, the authors of the Nature study rule out MOND without even making a calculation for what that limit would predict. Stacy had to do it for them. And he found that MOND is largely compatible with the upper value of their supposed measurement results.

Having said that, let us have a look at their data.

So the galaxy in question is an “ultra-diffuse galaxy” with “globular clusters.” For all I can tell that means it’s a smear with dots. The idea is that you measure how fast the dots move. Then you estimate whether the visible mass suffices to explain the speed by which the dots move. If it does, you call that a galaxy without dark matter. Have I recently mentioned that I am not an astrophysicist?

There are ten of the globular clusters, and here is the data. With the best-fit Gaussian.

Figure 3b of Dokkum et al, Nature 555, p. 629–632

In case that looks a little underwhelming, some nice words must be added here about how remarkable an achievement it is to make such a difficult measurement and how brilliant these scientists are and so on. Still, ehm, that’s some way to fit data.

And it’s not the only way to analyze the data. Indeed, they tried three different ways which gives the results 4.7 km/s, 8.4 km/s and 14.3 km/s. All I learn from this is that it’s not enough data to make reliable statistical estimates from. But then I’m a theorist.

Michelle Collins, however, is an actual astrophysicist. She is also skeptical. She even went and applied two other methods to analyze the data and arrived at mean values of 12 +/-3 km/s or 11.5+/-4 km/s, which is well compatible with Stacy’s MOND estimate.

Michelle also points out that globular clusters are often not good representatives to measure what is going on in a whole galaxy, because these clusters might have joined the galaxy at a late stage of formation. In other words, even those estimates might be totally wrong because the sample is skewed.

When I factor all this information together, I arrive at a 95 percent probability that this supposedly dark-matter-less galaxy will turn out to contain dark matter after all and it will be well compatible with modified gravity.

I give it an equally high probability that five years after the claim has been refuted, astrophysicists will still say modified gravity has been ruled out by it. Like the Nature paper refers once again to the Bullet cluster but fails to mention that the Bullet cluster can well be explained with modified gravity, but is difficult to explain with particle dark matter.


A recent Nature editorial praised a “Code of Ethics for Researchers” that was proposed by the World Economic Forum Young Scientists Community. In this Code, you can read that scientists are supposed to pursue the truth and
“Pursuing the truth means following the research where it leads, rather than confirming an already formed opinion. This is particularly challenging but necessary when questioning current beliefs [...] Results must be represented accurately without over- or understatement, hiding facts and/or drawbacks, or misleading the reader in any way.”
Maybe the editors at Nature should read what they recommend.

Update April 11: The paper’s first author has some comments on the various points of criticism that have been raised here.
Update April 14: A group of astrophysicists has a response on the arXiv: “Current velocity data on dwarf galaxy NGC1052-DF2 do not constrain it to lack dark matter.”
Update April 16: Another paper on the arXiv today, this one showing that the observations aren’t in conflict with modified gravity: MOND and the dynamics of NGC1052-DF2.

Wednesday, April 04, 2018

Particle Physicists begin to invent reasons to build next larger Particle Collider

Collider quilt. By Kate Findlay.
[Image: Symmetry Magazine]
Nigel Lockyer, the director of Fermilab, recently spoke to BBC about the benefits of building a next larger particle collider, one that reaches energies higher than the Large Hadron Collider (LHC).

Such a new collider could measure more precisely the properties of the Higgs-boson. But that’s not all, at least according to Lockyer. He claims he knows there is something new to discover too:
“Everybody believes there’s something there, but what we’re now starting to question is the scale of the new physics. At what energy does this new physics show up,” said Dr Lockyer. “From a simple calculation of the Higgs’ mass, there has to be new science. We just can’t give up on everything we know as an excuse for where we are now.”
First, let me note that “everybody believes” is an argument ad populum. It isn’t only non-scientific, it is also wrong because I don’t believe it, qed. But more importantly, the argument for why there has to be new science is wrong.

To begin with, we can’t calculate the Higgs mass; it’s a free parameter that is determined by measurement. Same with the Higgs mass as with the masses of all other elementary particles. But that’s a matter of imprecise phrasing, and I only bring it up because I’m an ass.

The argument Lockyer is referring to are calculations of quantum corrections to the Higgs-mass. Ie, he is making the good, old, argument from naturalness.

If that argument were right, we should have seen supersymmetric particles already. We didn’t. That’s why Giudice, head of the CERN theory division, has recently rung in the post-naturalness era. Even New Scientist took note of that. But maybe the news hasn’t yet arrived in the USA.

Naturalness arguments never had a solid mathematical basis. But so far you could have gotten away saying they are handy guides for theory development. Now, however, seeing that these guides were bad guides in that their predictions turned out incorrect, using arguments from naturalness is no longer scientifically justified. If it ever was. This means we have no reason to expect new science, not in the not-yet analyzed LHC data and not at a next larger collider.

Of course there could be something new. I am all in favor of building a larger collider and just see what happens. But please let’s stick to the facts: There is no reason to think a new discovery is around the corner.

I don’t think Lockyer deliberately lied to BBC. He’s an experimentalist and probably actually believes what the theorists tell him. He has all reasons for wanting to believe it. But really he should know better.

Much more worrisome than Lockyer’s false claim is that literally no one from the community tried to correct it. Heck, it’s like the head of NASA just told BBC we know there’s life on Mars! If that happened, astrophysicists would collectively vomit on social media. But particle physicists? They all keep their mouth shut if one of theirs spreads falsehoods. And you wonder why I say you can’t trust them?

Meanwhile Gordon Kane, a US-Particle physicist known for his unswerving support of supersymmetry, has made an interesting move: he discarded of naturalness arguments altogether.

You find this in a paper which appeared on the arXiv today. It seems to be a promotional piece that Kane wrote together with Stephen Hawking some months ago to advocate the Chinese Super Proton Proton Collider (SPPC).

Kane has claimed for 15 years or so that the LHC would have to see supersymmetric particles because of naturalness. Now that this didn’t work out, he has come up with a new reason for why a next larger collider should see something:
“Some people have said that the absence of superpartners or other phenomena at LHC so far makes discovery of superpartners unlikely. But history suggests otherwise. Once the [bottom] quark was found, in 1979, people argued that “naturally” the top quark would only be a few times heavier. In fact the top quark did exist, but was forty-one times heavier than the [bottom] quark, and was only found nearly twenty years later. If superpartners were forty-one times heavier than Z-bosons they would be too heavy to detect at LHC and its upgrades, but could be detected at SPPC.”
Indeed, nothing forbids superpartners to be forty-one times heavier than Z-bosons. Neither is there anything that forbids them to be four-thousand times heavier, or four billion times heavier. Indeed, they don’t even have to be there at all. Isn’t it beautiful?

Leaving aside that just because we can’t calculate the masses doesn’t mean they have to be near the discovery-threshold, the historical analogy doesn’t work for several reasons.

Most importantly, quarks come in pairs that are SU(2) doublets. This means once you have the bottom quark, you know it needs to have a partner. If there wouldn’t be one, you’d have to discontinue the symmetry of the standard model which was established with the lighter quarks. Supersymmetry, on contrast, has no evidence among the already known particles speaking in its favor.

Physicists also knew since the early 1970s that the weak nuclear force violates CP-invariance, which requires (at least) three generations of quarks. Because of this, the existence of both the bottom and top quark were already predicted in 1973.

Finally, for anomaly cancellation to work you need equally many leptons as quarks, and the tau and tau-neutrino (third generation of leptons) had been measured already in 1975 and 1977, respectively. (We also know the top quark mass can’t be too far away from the bottom quark mass, and the Higgs mass has to be close by the top quark mass, but this calculation wasn’t available in the 1970s.)

In brief this means if the top quark had not been found, the whole standard model wouldn’t have worked. The standard model, however, works just fine without supersymmetric particles. 

Of course Gordon Kane knows all this. But desperate times call for desperate measures I guess.

In the Kane-Hawking pamphlet we also read:
“In addition, a supersymmetric theory has the remarkable property that it can relate physics at our scale, where colliders take data, with the Planck scale, the natural scale for a fundamental physics theory, which may help in the efforts to find a deeper underlying theory.”
I don’t disagree with this. But it’s a funny statement because for 30 years or so we have been told that supersymmetry has the virtue of removing the sensitivity to Planck scale effects. So, actually the absence of naturalness holds much more promise to make that connection to higher energy. In other words, I say, the way out is through.

I wish I could say I’m surprised to see such wrong claims boldly being made in public. But then I only just wrote two weeks ago that the lobbying campaign is likely to start soon. And, lo and behold, here we go.

In my book “Lost in Math” I analyze how particle physicists got into this mess and also offer some suggestions for how to move on.

Tuesday, April 03, 2018

Book Review: “Farewell to Reality” by Jim Baggott

Farewell to Reality: How Modern Physics Has Betrayed the Search for Scientific Truth
Jim Baggott
Pegasus Books (1 Aug 2013)

Not sure how I missed “Farewell to Reality” when it came out. Indeed, I didn’t take note of Jim Baggott’s writing until I was asked to review one of his more recent books for Physics World. And having enjoyed that, I had a look at his previous books.

“Farewell to Reality,” which appeared in 2013, is a critical take on supersymmetry, string theory, multiverses, many worlds, and related ideas. Baggott collectively refers to them as “fairy tale science.”

His book is a well-researched and methodological approach to these speculative theories. Baggott first establishes a basis, spelling out what he will take the purpose of scientific explanation to be. Then he goes through the background knowledge (general relativity, quantum mechanics, standard model). Having done that, he evaluates whether the “fairy tales” are worth being taken seriously, concluding (unsurprisingly given the book’s title) that, no, they’re not.

The book suffers somewhat from its rather heavy, philosophical opening chapter, followed by the inevitable but necessary terminology, but the later chapters pick up in pace. It takes some enthusiasm to get through the book’s first part. But this slow start has the benefit of making the book fairly self-contained; I believe you don’t need to bring more than high-school physics to make sense of Baggott’s explanations.

I largely agree with Baggott’s assessment, though I am less critical of research on the foundations of quantum mechanics and I could quibble with his take on black hole evaporation, but it seems somewhat besides the point. I share Baggott’s worry that presenting unfounded speculations, like that we live in a multiverse, as newsworthy research undermines public trust in science. Baggott writes:
“[T]he continued publication of popular science books and the production of television documentaries that are perceived to portray superstring theory or M-theory as ‘accepted’ explanations of empirical reality (legitimate parts of the authorized version of reality) is misleading at best and at worst ethically questionable.”

“I believe that damage is being done to the integrity of the scientific enterprise. The damage isn’t always clearly visible and is certainly not always obvious. Fairy-tale physics is like a slowly creeping yet inexorable dry rot. If we don’t look for it, we won’t notice that the foundations are being undermined until the whole structure comes down on our heads.”

which I think is entirely correct.

Baggott is a gifted science writer whose explanations seem as effortless as I’m sure they’re not. He knows his stuff and isn’t afraid of clear words. And having noted this, it is not irrelevant to mention that Baggott is no longer working in academia; he has no reason to sell fairy tales as science. And he doesn’t. He’s a writer you can trust.

While I am sorry I missed Baggott’s book when it appeared, I am glad I didn’t read it before writing my own book. It’s somewhat depressing to look at “Farewell to Reality” years after it was published and see that nothing has changed.

I would recommend “Farewell to Reality” to anyone who is looking for a sober assessment of what to make of all the interesting but speculative ideas that theoretical physicists have cooked up in the past decades.

I also recommend of course that you buy my book. It covers some more topics that Baggott doesn’t discuss, such as models for inflation, dark matter, various approaches to quantum gravity, and what the absence of supersymmetric particles at the LHC means.

Wednesday, March 28, 2018

Why Black Stars Aren’t A Thing.

Not a black star,
but about equally real.
I came to physics by accident. I had studied mathematics, but the math department was broke. When I asked the mathematicians for a job, they sent me to the other side of the building. “Ask the physicists,” they said.

The physicists didn’t only give me a job. They also gave me a desk, a computer, and before I knew I had a topic for a diploma thesis. I was supposed to show that black holes don’t exist.

I didn’t know at that time, but it was my supervisor’s shtik, the black-holes-don’t-exist-speech. Prof Dr Dr hc mult Walter Greiner, who passed away two years ago, was the department head when I arrived. His argument against black holes was that “God wouldn’t separate himself from part of the universe.” Yo. He mostly worked on heavy ion physics.

I had made pretty clear to him that I wasn’t interested in heavy ion physics. Really I wasn’t sure I wanted to graduate in physics at all; it wasn’t even my major. But I was the math person, so certainly I could prove that black hole’s weren’t, no?

It was either that or computer simulations of big nuclei or back to the broke mathematicians. I picked the black holes.

That was 1997. Back then, measurements of the motion of stars around Sag A* were running, but they would not be published until 1998. And even after Sag A* proved to be dark, small, and heavy enough so that it should be a black hole, it took ten more years to demonstrate that indeed it doesn’t have hard surface, thus providing evidence for a black hole horizon.

We now know that Sag A* is a supermassive black hole, and that such black holes are commonly found in galactic centers. But when I was a student the case was not settled.

Greiner had explained to me why he thought black holes cannot form in stellar collapse. Because we know that black holes emit radiation, the famous “Hawking radiation.” So, when a star collapses it begins emitting all this radiation and it loses mass and the horizon never forms. That was his great idea. Ingenious! Why had no one thought of this before?

After some months digging in the literature, it became clear to me that it had been tried before. Not once, but several times, and equally many times it had been shown not to work. This was laid out in various publications, notably in Birrell and Davies’ textbook, but Greiner’s interest in the topic didn’t go far enough to look at this. Indeed, I soon found out that I wasn’t the first he had put on the topic, I was the third. The first delivered a wrong proof (and passed), the second left. Neither option seemed charming.

Black hole with accretion disk
and jet. Artist's impression.
[Image Source]
The argument for why Greiner’s idea doesn’t work is a shitload of math, but it comes down to a very physical reason: You can’t use Hawking radiation to prevent black holes from forming because that’s in conflict with the equivalence principle.

The equivalence principle is the main tenet of general relativity. It says that a freely falling observer should not be able to tell the presence of a gravitational field using only data from their vicinity, or “locally” as the terminology has it.

Hawking radiation obeys the equivalence principle – as it should. This means most importantly that an observer falling through the black hole horizon does not notice any radiation (or anything else that would indicate the presence of the horizon). The radiation is there, but its wavelengths are so long – of the size of the horizon itself – that the observer cannot measure the radiation locally.

If you want to know how Hawking-radiation affects the black hole you must calculate the total energy and pressure which the quantum effects creates. These are collected in what’s called the (renormalized) stress-energy-tensor. Turns out it’s tiny at the black hole horizon, and the larger the black hole, the smaller it is.

All of this is perfectly compatible with the equivalence principle. And that’s really all you need to know to conclude you can’t prevent the formation of black holes by Hawking-radiation: The contribution to the energy-density from the quantum effects is far too small, and it must be small because else an infalling observer would notice it, screwing over the equivalence principle.

What normally goes wrong when people argue that Hawking-radiation can prevent the formation of black hole horizons is that they use the result for the Hawking radiation which a distant observer would measure. Then they trace back this radiation’s energy to the black hole horizon. The result is infinitely large. That’s because if you want to emit anything at the horizon that can escape at all, you must give it an infinite amount of energy to start with. This is nonsense because Hawking radiation is not created at the black hole horizon. But it’s this infinity that has led many people to conclude that a collapsing star may be able to shed all of its energy in Hawking radiation.

But whenever you do physics and the math gives you an infinity, you should look for a mistake. Nothing physically real can be infinite. And indeed, the infinity which you get here cannot be observed. It is is cancelled by another contribution to the stress-energy which comes from the vacuum polarization. Collect all terms and you conclude, again, that the effects at the horizon are tiny. Done correctly, they do, of course, obey the equivalence principle.

In summary: Yes, black holes evaporate. But no, the energy-loss cannot prevent the formation of black hole horizons.

That was the status already in the late 1970s. Walter Greiner wasn’t the first but also not the last to try using quantum effects to get rid of the black hole horizon. I come across one or the other variation of it several times a year. Most recently it was via a piece on Science Daily, which also appeared PhysOrg, Science Alert, Gizmodo, BigThink, and eventually also Scientific American, where we read:
Black Hole Pretenders Could Really Be Bizarre Quantum Stars

New research reveals a possible mechanism allowing “black stars” and “gravastars” to exist

These articles go back to a press release from SISSA about a paper by Raúl Carballo-Rubio which was recently published in PRL (arXiv version here).

Carballo-Rubio doesn’t actually claim that black holes don’t form; instead he claims – more modestly – that “there exist new stellar configurations, and that these can be described in a surprisingly simple manner.”

These new stellar configurations, so his idea, are stabilized by strong quantum effects in a regime where general relativity alone predicts there should be nothing to prevent the collapse of matter. These “black stars” do not actually have a horizon, so the quantum effects never actually become infinitely large. But since the pressure from the quantum effects would get infinitely large if the mass were compressed into the horizon, the radius at which it stabilizes must be outside the horizon.

In other words, what stabilizes these black stars is the same effect that Greiner thought prevents black holes from forming. You can tell immediately it’s in conflict with the equivalence principle for there is nothing locally there, at the horizon or close by it, from which the matter would know when to stop collapsing. At horizon formation, the density of matter can be arbitrarily low, and the matter doesn’t know – cannot know! – anything about redshift from there to infinity. The only way this matter can know that something is supposed to happen is by using global information, ie by violating the equivalence principle.

Indeed that’s what Carballo-Rubio does, though the paper doesn’t really spell out where this assumption comes in, so let me tell you: Carballo-Rubio assumes from the onset that the system is static. This means the “quantum star” has no time-dependence whatsoever.

This absence of time-dependence is an absolutely crucial point that you are likely to miss if you don’t know what to look for, so let me emphasize: No stellar object can be truly static because this means it must have existed forever and will continue to exist for all eternity. A realistic stellar object must have formed somewhen. Static solutions do not exist other than as math.

The assumption that the system be static is hence a global assumption. It is not something that you can reach approximately, say, at the end of a collapse. Concretely the way this enters the calculation is by choice of the vacuum state.

Yes, that’s right. There isn’t only one vacuum state. There are infinitely many. And you can pick one. So which one do you pick?

Before we get there, allow me a digression. I promise it will make sense in a minute. Do you recall when Walter Wagner sued CERN because turning on the LHC might create tiny black holes that eat up earth?

It is rare for black hole physics to become a matter of lawsuits. Scientists whose research rarely attracts any attention were suddenly in the position of having to explain why these black holes, once created, would be harmless.

On the face of it, it’s not a difficult argument. These things would have interaction-probabilities far smaller than even neutrinos. They would readily pass through matter, leaving no trace. And being created in highly-energetic collisions, they’d be speedy, fly off to outer space and be gone.

But then, these tiny black holes would have a small but nonzero probability to become trapped in Earth’s gravitational field. They would then keep oscillating around the center of the planet. And if they stuck around for sufficiently long, and there were sufficiently many of them, they could grow and eventually eat up Earth inside-out. Not good.

That, however, the scientists argued, could not happen because these tiny black holes evaporate in a fraction of a second. If you believe they evaporate. And suddenly theoretical physicists had to very publicly explain why they are so sure black holes evaporate because otherwise the LHC might not be turned on and their experimentalist friends would never forgive them.

Rather unsurprisingly, there had been one-two people who had written papers about why black holes don’t evaporate. Luckily, these claims were easy to debunk. The court dismissed the lawsuit. The LHC turned on, no black holes were created, and everyone lived happily ever after.

For me the most remarkable part of this story isn’t that someone would go try to sue CERN over maybe destroying the world. Actually I have some understanding for that. Much more remarkable is that I am pretty sure everyone in the field knows it’s easy enough to find a theoretical reason for why black holes wouldn’t evaporate. All you have to do is postulate they don’t. This postulate is physical nonsense, as I will explain in a moment, so it would merely have complicated the case without altering the conclusion. Still I think it’s interesting no one even brought it up. Humm-humm.

So what’s that nonsense postulate that can keep black holes from evaporating? You choose a vacuum state in which they don’t. Yes, you can do that. Perfectly possible. It’s called the “Boulware state.” The price you pay for this, however, is that the energy created by quantum effects at the black hole horizon goes to infinity. So it’s an unphysical choice and no one ever makes it.

Ah! I hear you say. But not very loudly, so let me summarize this in plain terms.

You can assume a black hole doesn’t evaporate on the expense of getting an infinite amount of stress-energy in the horizon region. That’s an unphysical assumption. And it’s the same assumption as postulating the system does not change in time: Nothing in, nothing out.

And that – to tie together the loose ends – is exactly what Carballo-Rubio did. He doesn’t actually have a horizon, but he uses the same unphysical vacuum-state, the Boulware state. That’s the reason he gets such a large quantum pressure, hence violating the equivalence principle. It comes from the assumption that the system is static, has always been static, and will always remain static.

Let me be clear that Carballo-Rubio’s paper is (for all I can tell) mathematically sound. And the press-release is very carefully phrased and accurate. But I think he should have been clearer in pointing out that the assumption about time-independence is global and therefore he is describing a physically impossible situation that is not even approximately realistic.

If you followed my above elaborations, it should be clear that the details don’t matter all that much. The only way you can prevent a horizon from forming is to violate the equivalence principle. And worse, this violation must be possible when space-time curvature is arbitrarily small, as small or even smaller than what we have here on Earth.

Of course you can postulate whatever you want and calculate something. But please let us be clear that all these black stars and gravastars and quantum stars  and what have you require throwing out general relativity in regions where there is no local measure whatsoever that would call for such a breakdown. Doesn’t matter how much math you pour over it, it’s still in conflict with what we know about gravity.

The realistic situation is one in which matter collapses under its gravitational pull. In this case you have a different vacuum state (the Unruh state), which allows for evaporation. And that brings you full circle to the above argument for why the stress-energy is too small to prevent horizon formation. There’s no way to avoid the formation of a black hole. Nope, there isn’t. Black holes really exist.

As to my diploma. I simply wrote my thesis about something else but didn’t mention that until after the fact. I think Greiner never forgave me. A few years later he fired me, alas, unsuccessfully. But that’s a different story and shall be told another time.

That was a long post, I know. But I hope it explains why I think black stars and gravastars and qantum stars and so on are nonsense. And why I happen to know more about the topic than I ever wanted to know.

Monday, March 26, 2018

Modified Gravity and the Radial Acceleration Relation, Again

Have I recently mentioned that I am now proud owner of my personal modified gravity theory? I have called it “Covariant Emergent Gravity.” Though frankly I’m not sure what’s emergent about it; the word came down the family tree of theories from Erik Verlinde’s paper. Maybe I had better named it Gravity McGravace, which is about equally descriptive.

It was an accident I even wrote a paper about this. I was supposed to be working on something entirely different – an FQXi project on space-time defects – and thought that maybe Verlinde’s long-range entanglement might make for non-local links. It didn’t. But papers must be written, so I typed up my notes on how to blend Verlinde’s idea together with good, old, general relativity.

Then I tried to forget about the whole thing. Because really there are enough models of modified gravity already. Also, I’m too fucking original to clean up somebody else’s math. Besides, every time I hear the name “Verlinde” it reminds me that I once confused Erik Verlinde with his brother Herman, even though I perfectly know they’re identical twins. It’s a memory I’d rather leave buried in the depths of my prefrontal cortex.

But next thing I know I have a student who wants to work on modified gravity. He’s a smart young man. Indeed, I now think he is a genius. See, while I kept blathering about the awesomeness of McGaugh et al’s recent data on the radial acceleration relation, he had the brilliant idea of plotting the prediction from my model over the data.
Figure 1 from arXiv:1803.08683

Eh, I thought, look at this. (Deep thoughts are overrated.)

The blue squares in this figure are the data points from the McGaugh et al paper. The data come from galactic rotation curves of 156 galaxies, spanning several orders of magnitude. The horizontal axis (gB) shows the acceleration that you would expect from the “normal” (baryonic) mass. The vertical axis (gtot) shows the actually observed (total) acceleration. The black dotted line is normal gravity without dark matter. The red curve is the prediction from my model; 1σ-error in pink. For details, see paper.

As the data show, the observed acceleration is higher than what the normal (Newtonian limit of ) general relativity predicts, especially at low accelerations. Physicists usually chalk this mismatch up to dark matter. But we have known for some decades that Milgrom’s Modified Newtonian Dynamics (MOND) does a better job explaining the regularity of this relation, in the sense that MOND requires less fumbling to fit the data.

However, while MOND does a good job explaining the observations, it has the unappealing property of requiring an “interpolation function”. This function is necessary to get a smooth transition from the regime in which gravity is modified (at low acceleration) to the normal gravity regime, which must be reproduced at high acceleration to fit observations in the solar system. In the literature one can find various choices for this interpolation function.

Besides the function, MOND also has a free constant that is the acceleration scale at which the transition happens. At accelerations below this scale, MOND effects become relevant. Turns out this constant is to good approximation the square root of the cosmological constant. No one really knows why that is so, but a few people have put forward ideas where this relation might come from. One of them is Erik Verlinde.

Verlinde extracts the value of this constant from the size of the cosmological horizon. Something about an insertion of mass into de-Sitter space changing the volume entropy and giving rise to a displacement vector that has something to do with the Newtonian potential. Among us, I think this is nonsense. But then, what do I know. Maybe Verlinde is the next Einstein and I’m just too dumb to understand his great revelations. And in any case, his argument fixes the free constant.

Then my student convinced me that if you buy what I wrote in my last year’s paper, Covariant Emergent Gravity doesn’t need an interpolation function. Instead, it gives rise to a particular interpolation function. So then, we were left with a particular function without free parameters.

If you have never worked in theory-development, you have no idea how hair-raisingly terrible a no-parameter model is. It either fits or it doesn’t. There’s no space for fudging here. It’s all or nothing, win or lose.

We plotted, we won. Or rather, Verlinde won. It’s our function with his parameter that you see plotted in the above figure. Fits straight onto the data.

I’m not sure what to make out of this. The derivation is so ridiculously simple that Kindergarten math will do it. I’m almost annoyed I didn’t have to spend some weeks cracking non-linear partial differential equations because then at least I’d feel like I did something. Now I feel like the proverbial blind chick that found a grain.

But well, as scientists like to say, more work is needed. We’re still scratching our heads over the gravitational lensing. Also the relation to Khoury et al’s superfluid approach has remained murky.

So stay tuned, more is to come.

Tuesday, March 20, 2018

Hawking’s “Final Theory” is not groundbreaking

Yesterday, the media buzzed with the revelation that Stephen Hawking had completed a paper two weeks before his death. This paper supposedly contains some breathtaking insight.

The headlines refer to a paper titled “A Smooth Exit from Eternal Inflation” in collaboration with Thomas Hertog. The paper was originally uploaded to the arXiv in July last year, but it was updated two weeks ago. It is under review with “a leading journal” which I suspect but do not know is Physical Review D. Thomas Hertog gave a talk about this at the conference which I attended last summerYou can watch the video of Hertog’s talk here.

According to The Independent the paper contains “a theory explaining how we might detect parallel universes and a prediction for the end of the world.” Furthermore, we learn, “Hawking also theorised in his final work that scientists could find alternate universes using probes on space ships, allowing humans to form an even better understanding of our own universe, what else is out there and our place in the cosmos.”

In the Sunday Times you can read that the paper “shows how we might find other universes”  and in The Telegraph you find a quote by Carlos Frenk, professor of cosmology at Durham University who said: “The intriguing idea in Hawking’s paper is that [the multiverse] left its imprint on the background radiation permeating our universe and we could measure it with a detector on a spaceship.”

Since the paper doesn’t say anything about detecting parallel universes, I was originally confused whether the headlines were referring to another paper. But no, Thomas Hertog confirmed to me that the paper in question is indeed the paper that is on the arXiv. There is no other paper.

So what does the paper say?

The paper is based on an old idea by Stephen Hawking and Jim Hartle called the “no-boundary” proposal. In the paper, the authors employ a new method to do calculations that were not previously possible. Specifically, they calculate which type of universes a multiverse would contain if this theory was correct. The main conclusion seems to be that our universe is compatible with the idea, and also that this particular multiverse which they deal with is not as large as the usual multiverse one gets from eternal inflation.

It’s not entirely uninteresting if you are into multiverse ideas, because then you need this information to calculate the probability of our universe. But it is also a very theoretical paper that does not say anything about observational consequences.

The only thing that the paper does say is that inflation took place. And inflation predicts that gravitational waves produced in the early universe should leave an imprint in the cosmic microwave background (CMB). This is the CMB polarization signal that BICEP was looking for but didn’t find. There are, however, some satellite missions in the planning that will look for it with better precision.

So how do we detect parallel universes? By detecting the CMB polarization. I do not kid you.

Here’s what Hertog said about this:
“This model predicts that our universe came into existence with a burst of rapid expansion called cosmic inflation. A big bang of this kind amplifies gravitational waves which in turn show up in satellite images of [the pattern of temperature fluctuations in] the cosmic microwave background. Future satellite missions should see this, if the theory is correct.

Observational evidence for the no-boundary model [in the form of gravitational waves from the big bang] would yield strong evidence for a multiverse. This paper provides a step towards a mathematically sound and testable model of the multiverse. That constitutes a significant extension of our notion of physical reality.

Some cosmologists have argued against the multiverse on the basis it can’t be tested. However our model shows that observations in our own universe can provide strong evidence for the existence of other universes. ”
Allow me put this into perspective.

Theoretical physicist have proposed some thousand ideas for what might have happened in the early universe. There are big bangs and big bounces and brane collisions and string cosmologies and loop cosmologies and all kinds of weird fields that might or might not have done this or that. All of this is pure speculation, none of it is supported by evidence. The Hartle-Hawking proposal is one of these speculations.

The vast majority of these ideas contain a phase of inflation and they all predict CMB polarization. In some scenarios the signal is larger than in others. But there isn’t even a specific prediction for the amount of CMB polarization in the Hawking paper. In fact, the paper doesn’t so much as even contain the word “polarization” or “tensor modes.”

The claim that the detection of CMB polarization would mean the multiverse exists makes as much sense as claiming that if I find a coin on the street then Bill Gates must have walked by. And a swarm of invisible angels floated around him playing harp and singing “Ode To Joy.”

In case that was too metaphorical, let me say it once again but plainly. Hawking has not found a new way to measure the existence of other universes.

Stephen Hawking was beloved by everyone I know, both inside and outside the scientific community. He was a great man without doubt, but this paper is utterly unremarkable.

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.

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