## Wednesday, November 19, 2008 ... //

### Parallel Universes and science on TV

The History Channel has aired

Parallel Universes
and one of the stars of the show, Clifford Johnson, seems to be unhappy about the outcome.

The idea of the program is that the newest results in science indicate that our Universe is probably much larger than we thought and it can contain many regions that are not smoothly connected to ours but that are qualitatively similar, the parallel universes. And the filmmakers thought it was a great theme for a TV program. And in fact, so do I. But...

What do these parallel universes mean?

Let me begin with the term "parallel universes". It is a term that seems to be exciting for a certain large group of the laymen (and filmmakers) although it creates almost no excitement among most professional physicists. The phrase has been given at least three vastly different meanings:
1. different histories that could occur in quantum mechanics interpreted with the many-worlds interpretation
2. different stringy vacua that may or may not be connected with ours by bubble nucleation within eternal inflation
3. different branes that may be parallel to our, Standard Model brane in our world if it is a braneworld
Again, professionals would never confuse these three concepts but the laymen and filmmakers often do - because what they really understand about these concepts are just the two words, "parallel universes". With this poor resolution of their wavelets, the very different concepts above may coincide.

However, the "parallel universes" in the many-worlds interpretation of quantum mechanics do not change any observation we could ever do, at least in principle. In the many-worlds interpretation of quantum mechanics, there exists a whole tree of alternative worlds where the past events took place with different outcomes. Our "branch" of the tree was chosen randomly. But we can't have any contact with the other branches where the history differs. For example, in many "alternative universes", Adolf Hitler may have won the war.

But we will never see these other worlds because the history of our world is something that can never be rewritten again. These different worlds have separated from ours, they will never reunite, and if you wish, you may also decide to believe that the other worlds don't exist (and choose e.g. the Consistent History approach, a fully satisfactory post-Copenhagen interpretation).

Adopting the many-worlds interpretation can't change the morality of rational people, either. While there may exist other worlds where you are a thief, mass murderer, global warming alarmist, or even an aggressive crackpot ;-) and you might think that these other worlds diminish the importance of your decisions, the reality is different. In this world, you will only be judged for the things you have done in this world, not in the others, so the existence of other worlds is inconsequential once again.

Also, the many-worlds interpretation of quantum mechanics was first coined half a century ago. That's surely not a topic that should be discussed as cutting-edge science.

Instead, this program primarily focused on the other two types of "parallel universes" - those from the stringy landscape and the possible parallel branes in our world. In principle, there may exist a causal contact between our world and these "parallel worlds" if the latter exist. But the nature of this contact is very different in both cases. In the case of the different vacua of the string landscape, they might exist within bubbles that emerge somewhere in our Universe and that will expand (or bubbles in a grandson or great grandson universe etc.) or, on the contrary, our Universe might have arisen from a bubble in another one. The causal relationship is very distant and asymmetric.

On the other hand, if there are parallel branes inside our braneworld, they are just a tiny fraction of a millimeter away from us (in the direction of a new coordinate of space). In principle, we can interact with them, at least gravitationally. We could send and receive gravitational waves - and perhaps other signals - to/from this additional brane if it existed and hosted life.

Clifford Johnson says that he has never heard about "level N parallel universes" in the scientific context, where N is an integer. Well, it's time to read one of Max Tegmark's papers, Clifford. ;-)

Are these things exciting?

Now, are these scenarios more likely than they were two decades ago? I think that the answer is clearly Yes. Are they guaranteed to be true? In the case of parallel branes in our world, the answer is No, we don't know how many parallel branes (and hidden gauge groups) there are in our compactification if any; in the case of other compactifications of string theory, the answer is Probably yes, we are almost certain that our type of "vacuum" is not the only vacuum-like solution to the fundamental equations of Nature. Even if you wanted to be extremely speculative and assume that all of string theory is wrong, more general insights have made it unlikely that our vacuum is a completely unique solution to some equations.

But we're not really sure about the existence of any "evolution links" between these other compactifications and our world; we're not sure whether the eternal inflation and other "nonminimal cosmologies" are physically relevant. So we don't know whether the multitude of compactifications has some implications that can influence the lives of the ordinary and even less ordinary people.

But are these notions exciting? Well, in science they are acceptable only if they are compatible with the experiments that have already been done. For example, one easy experiment implies that there are no dinosaurs in your apartment. All theories that would imply that there are easily visible dinosaurs over there are ruled out. There is still room for new phenomena but they are pretty subtle and it's damn hard to discover them. So if someone only gets excited by the dinosaurs in her bedroom or something else of the sort, she will be disappointed!

Now, are the typical viewers of the History Channel excited about the prospect of having an unusual signature at the LHC? What about a newly created particle that decays into many smaller particles isotropically, with apparently thermal distribution? Well, I think that the answer is obviously No, she is not excited. She doesn't even recognize that we have just produced a mini black hole. Even if she were told so, she has no idea whether it should be surprising or not.

Why isn't she excited? Because she doesn't know the things that you need to know to have sensible expectations about these relatively abstract experiments. She's been doing other things in her life. You only absorb the necessary background if you study these and related things at the technical level for years. By definition, the History Channel is not focusing at this expert audience. If it were, it would be the arXiv.TV station, not the History Channel.

Does it mean that non-experts shouldn't be shown any science? I think that the answer is a resounding No. Science on TV is important because it inspires newer generations and because it removes some kind of "unhealthy mystery" from the scientists. People should know that scientists do things that may be fun for many other people and they should know that these mysterious scientists who seem to be decoupled from the "ordinary world" are not conspiring to secretly destroy the world all the time. ;-) However, the TV programs are not focusing on the expert audiences so they have different (lower) technical standards and different (more entertainment-industry-like) criteria.

Still, I think that a good filmmaker of scientific programs should try to understand the topics and should try to be accurate. The accuracy will never be the only benchmark of his or her work but it will be one of them. The accuracy of technical statements that would turn a regular viewer off is almost likely to be sacrificed, to one extent or another. The Big Bang Theory at CBS is an exception: Sheldon Cooper's statements are remarkably accurate and reflect how a very bright and well-informed physicist would genuinely react to various things. The adviser is doing a superb job.

The price that you pay for this accuracy in TBBT is that the audiences can't quite identify themselves with Sheldon. They still (usually) like him but they know that "he's somewhere else" and they are ready to ignore the details of what he says. This decoupling is a price for the accuracy: the experts and the laymen are at a different frequency, indeed, and any TV show that shows them to be at the same frequency is guaranteed to be inaccurate about the science.

By the way, I want to mention a few examples of the better-than expected accuracy of TBBT. For example, Penny said something about "waiting for light years, as you - the physicists - would say". In a generic sitcom that mentions science, the actual "scientists" would think just like Penny does. A "light year" sounds scientific so it should clearly be used by scientists and others who want to sound as scientists.

But in TBBT, Sheldon explains very aptly that a physicist would actually never use the phrase because a "light year" is a unit of distance, not time, and gives a few more examples of a similar confusion.

He also defines astrology very accurately to make it clear why it is a mass delusion and debunks several additional science-loaded myths. Leslie Winkle realistically mentions some would-be predictions (e.g. modifications of dispersion relations) that some of her charlatan colleagues believe to follow from loop quantum gravity. And so on. These technically accurate sentences may only have been accurate because it is OK if the viewers don't quite understand - it's part of their purpose, after all. ;-) These sentences are produced by geeks who are not supposed to be understood.

However, there exists a different kind of statements and messages that the viewers are surely capable to understand and that should be communicated accurately, even in generic TV programs about science: the sociological statements.

The audiences should get a fair picture about the IQ of the people who work on various topics, the degree of respect they enjoy from their colleagues, the amount of time needed to develop and/or learn a scientific theory, and the confidence of various scientists in various basic, comprehensible statements. This is not hard and a distorted picture of these comprehensible points deserves to be called a dishonesty.

What I want to say is that a scientist should probably be tolerant if a TV program presents a technical idea inaccurately or if it makes it more "sexy" than the scientists actually think it is. Maybe it's because the scientist was narrow-minded, after all. Why didn't she think about a parallel world with dinosaurs in her bedroom? Maybe she should have! :-) And most of the simplification is because the normal viewers could simply not swallow the technical stuff in its precise form.

But scientists should expect and demand the accuracy in the filmmakers' description of the sociology of their fields: who believes whom and how much. These points don't have to be quite perfect but they should simply not be entirely wrong.

For example, it would be bad if a program created the impression that all top physicists are thrilled by Max Tegmark's level IV parallel universes. ;-) It would be bad because it is untrue - look at the citation counts - and moreover, even ordinary people are capable to understand that it is untrue. At least, Max Tegmark is a very serious scientist who also likes to write speculative stuff.

There also exist scientists who have never published any valuable stuff and who only create their name by publishing meaningless speculations directed at the laymen, not the peers - and I am talking not only about Lee Smolin - and it would be even worse if a filmmaker were presenting these things as the pillars of contemporary science. That would be as bad as presenting a "consensus" about a man-made climate catastrophe.

But be ready: if you were never imagining a dinosaur living in a parallel universe, it may have been due to your lack of imagination and the filmmaker is likely to be better in this respect, especially because he's been trained and selected to attract wide audiences and many people - and not only ordinary people - are more likely to be thrilled by visually attractive stuff! In fact, I often like visually intriguing stuff, too. It's a different stuff than scientific accuracy but it is another thing that I expect from TV shows that are worth watching.

And that's the memo.

Not Even Wrong and BRST

But let me mention another kind of distortion of science that I find absolutely stunning. Peter Woit, a critic of physics, decided to write a few blog posts trying to (dishonestly) suggest that he has an idea about the contemporary physics research. For no good reason, he chose the BRST quantization, a "modern" technical tool (from the 1970s) to analyze theories with gauge symmetries.

Now, this is a basic stuff that a normal graduate student usually learns when she is first introduced to gauge theories - surely not something that you can publish research papers about. But it is even more funny to look how Peter Woit divided this stuff into parts. In the first part, he talks about the action of symmetries on linear spaces - the material that, I am pretty sure, most string theorists have known since the high school.

Even more interesting is the second part because he effectively copies the section 3.2.1 of "Superstring Theory", a classic 1987 book by Green, Schwarz, and Witten. What Woit says about the BRST issues is more or less correct - it's what Green, Schwarz, and Witten have also written, after all. There are some strange delicate bugs - for example, a real physicist knows that the physically interesting ghost number is often a number different from zero - but most of his comments are OK. Now, isn't it ironic for a vitriolic, Al-Qaeda-style critic of string theory to choose a section of a string theory textbook as a source of explanations of a topic that he views important?

Now, what he is confused by is the philosophy and the very goal of the BRST machinery. The BRST machinery is not really "new physics". It is just a mathematical tool to apply to "old physics" and to determine the right Jacobians whenever gauge symmetries are gauge-fixed, to determine which states are physical, which states are not, and why the unphysical states do not cause any problems. You can use other (less convenient methods) to find the same results - and only the physical results about the physical states are physical (and measurable)! ;-)

Everything else about one's approach to a physical theory - whether we choose a gauge symmetry at all, whether we gauge-fix it now or then, how we gauge-fix it, whether we extend the gauge symmetry to a BRST symmetry, whether we use path integrals or the operator approach etc. - is just a question about our strategy to get the final results (such as the cross sections). We don't construct "new theories" in this way.

And once you learn the definition of the BRST cohomology, you are still light years (or at least years) away from being able to decide about the validity of string theory. These are just entirely different levels of knowledge.

The third and fourth part of Woit's "lectures" are purely mathematical and focus on things like exact sequences. That's perfectly fine but in combination with a grumpy guy who is often quoted as a critic of the abstract mathematical character of string theory that is claimed to be detached from experiments, the focus on the Chevalley-Eilenberg complexes sounds a little bit too ironic, doesn't it? What is the doable experiment that decides whether these complex are relevant for the world around us? Isn't it not even wrong blah blah blah? But none of his anonymous readers - or the journalistic garbage that has promoted the jerk in the media two years ago - cares because all of them are equipped with hypocrisy of an unprecedented degree.

Experimental chauvinism

One more controversy is going to be mentioned here. Matt Strassler published his first analysis of the recent CDF dimuon events paper,
Flesh and blood, or merely ghosts?
As the title indicates, Matt is skeptical about ambitious interpretations of the paper in terms of brand new physics.

Tommaso Dorigo decided to criticize Matt's paper. Tommaso thinks that it was politically incorrect for Matt to
• notice that only a subset of the CDF collaboration signed the paper
• consider the paper to be too short given the importance of the suggested interpretation
• be disappointed that certain extra checks were not performed and certain extra graphs were not included
• be disappointed with some logically questionable interpretations of other graphs.
Tommaso also seems to think that the experimenters themselves are the only ones who have the right to offer an opinion on the reliability of certain results. Recently, I agreed with Tommaso that the papers should be published if they are able to survive a fixed amount of scrutiny, regardless of the "sign" of the papers i.e. whether or not they are surprising for someone.

But I incorrectly thought that the agreement was due to Tommaso's reasonable opinions. In fact, the agreement was a pure coincidence and the reason behind Tommaso's opinions was the dumbest kind of experimental chauvinism you could think of. Tommaso is clearly not alone: other experimenters physically forced Matt to modify some formulations in his paper although - fortunately - the content of the paper hasn't yet been changed.

Now, let me tell you about the actual situation here.

Matt is an exceptional theorist as far as the analysis of raw collider data goes. As a winner of the LHC Olympics, he is probably better in these things than the union of the 370 worst CDF members and at least comparable to the union of the 370 best CDF members. He may lack some particular types of experience but on the other hand, he is clearly more intelligent than virtually all members of the CDF collaboration and the only reason why he didn't become an experimental particle physicist was that he was able to do something more difficult, too.

Which 370 members signed the paper may therefore be a relevant piece of information for a person less qualified than Matt who is deciding whether Matt should be trusted. Unfortunately, the subset is "unknown". ;-)

According to the CDF internal policies, a paper that gets a sufficient number of supporters is published as a paper of the whole CDF collaboration that claims "consensus" in this way. Well, it's questionable whether it is such a good idea to hide who agreed and who disagreed with something but it's their policy. On the other hand, it's just policy, not the truth. And it is only their policy, not an international law.

Theorists like Matt are in no way constrained by similar policies and their task is different from preserving someone's little secrets and taboos and from pretending that they don't know certain things. The theorists' task is to combine all the available information into the most convincing - and therefore hopefully correct - theoretical explanation of the observations.

If an imperfection of the experimenters seems to be a likely explanation - and it is surely a rather important candidate in this case where the alternatives involve a very shocking new type of physics - the theorist must also make reasonable guesses about the likelihood that the experimenters did a certain imperfect step. To make this guess, Matt correctly used all the available information - including the limited number of supporters of the paper - and, as an honest theorist, he also openly revealed all the arguments that have influenced his decisions. The counting of the people was just one of the minor ones.

Tommaso seems to think that it should be a heresy to think that the experimenters are fallible. To make things even more ludicrous, he offers us this nice quote by Freeman Dyson:
The professional duty of a scientist confronted with a new and exciting theory (or data) is to try to prove it wrong. That is the way science works. This is the way science stay honest. Criticism is absolutely necessary to make room for better understanding.
And what is Tommaso's interpretation? Freeman Dyson surely meant that the criticism is only acceptable if it is not directed against the "infallible" Tommaso Dorigo and his friends, Tommaso argues: the criticism must be "constructive". Well, that's an amusing interpretation, especially if Tommaso's idiotic and intimidating attack against Matt's paper is probably supposed to be constructive in this sense. ;-)

Sorry, Tommaso, but Freeman Dyson surely meant what he said: even experimenters are fallible. And some of them are not only fallible but they are as dumb as a door knob if not as Tommaso himself! The history of science is flooded by all kinds of "renowned" experimenters who have proved that relativity was wrong, the Feynman - Gell-Mann V-A theory of weak interactions was wrong, and dozens of other bizarre conclusions.

Whether or not the subgroup of the CDF collaboration discovered something new or important or whether they have just showed their imperfect abilities to manipulate with the detectors and the data remains to be seen. Attempts of hundreds of average experimenters to bully a theorist are surely not helpful in revealing the truth.