After watching the Breakthrough Prize awards tonight, tomorrow night on the Science Channel you can watch a program that actually features physicists rather than Hollywood/Silicon Valley celebrities. There’s an hour long infomercial for the Multiverse, entitled “Which Universe Are We In?”. You get to hear from
- Max Tegmark starting and ending the show with a generic promotional spiel about how wonderful the multiverse is.
- Seth Lloyd about how weird QM is, and that it and cosmology provide strong experimental support for the multiverse.
- Anthony Aguirre explaining about seeing collisions of other universes in the sky, and about how evidence for the multiverse has now been seen (BICEP2), providing a huge leap forward for the multiverse.
- Laura Mersini-Houghton about the string landscape and how she has used it to make predictions, which are now becoming accepted.
The program ends kind of like a car commercial, with beautiful scenery and swelling music. A voice over mentions un-named fuddy-duddy critics, mainly to say that BICEP2’s “great support for the theory of the multiverse” has “given then something to think about”. It suggests that the answer to the question raised by all these different kinds of multiverse (“which one is true?”) can be answered by believing all multiverse models at once, no need to choose.
No mention of tedious things like dust. This multiverse is all new and shiny, slices, dices, provides every reality you could possibly want.
On a somewhat higher level, Quanta magazine followed up last week’s multiverse piece with a new one this past week, Multiverse Collisions May Dot the Sky from Jennifer Ouellette. Aguirre appears here too, working with collaborators on analyzing possibly observable consequences of bubble collisions. One of them is Hiranya Peiris, who explains that multiverse theory is like the theory of evolution:
Peiris acknowledges that this argument has its critics. “It can predict anything, and therefore it’s not valid,” Peiris said of the reasoning typically used to dismiss the notion of a multiverse as a tautology, rather than a true scientific theory. “But I think that’s the wrong way to think about it.” The theory of evolution, Peiris argues, also resembles a tautology in certain respects — “an organism exists because it survived” — yet it holds tremendous explanatory power. It is a simple model that requires little initial input to produce the vast diversity of species we see today.
A multiverse model tied to eternal inflation could have the same kind of explanatory power. In this case, the bubble universes function much like speciation. Those universes that happen to have the right laws of physics will eventually “succeed” — that is, they will become home to conscious observers like ourselves. If our universe is one of many in a much larger multiverse, our existence seems less unlikely.
The problem of course with bubble collision “predictions” are that they’re not falsifiable. As far as they’re concerned, you can only win: seeing nothing doesn’t disprove the multiverse. The most recent attempt to look for evidence in the CMB that I’m aware of is this, which found nothing in the WMAP-7 data. I haven’t seen anything using Planck data released so far. Presumably when new data is released later this month some kind of search for bubble collision evidence will be done, and Quanta magazine isn’t likely to report the likely outcome.
The Quanta piece isn’t an infomercial like the TV program, it does explain some of the problems with this whole endeavor, including this from Erick Weinberg:
“My own feeling is you need to adjust the numbers rather finely to get it to work,” Weinberg said. The rate of formation of the bubble universes is key. If they had formed slowly, collisions would not have been possible because space would have expanded and driven the bubbles apart long before any collision could take place. Alternatively, if the bubbles had formed too quickly, they would have merged before space could expand sufficiently to form disconnected pockets. Somewhere in between is the Goldilocks rate, the “just right” rate at which the bubbles would have had to form for a collision to be possible.
Researchers also worry about finding a false positive. Even if such a collision did happen and evidence was imprinted on the CMB, spotting the telltale pattern would not necessarily constitute evidence of a multiverse. “You can get an effect and say it will be consistent with the calculated predictions for these [bubble] collisions,” Weinberg said. “But it might well be consistent with lots of other things.” For instance, a distorted CMB might be evidence of theoretical entities called cosmic strings. These are like the cracks that form in the ice when a lake freezes over, except here the ice is the fabric of space-time. Magnetic monopoles are another hypothetical defect that could affect the CMB, as could knots or twists in space-time called textures.
Weinberg isn’t sure it would even be possible to tell the difference between these different possibilities, especially because many models of eternal inflation exist. Without knowing the precise details of the theory, trying to make a positive identification of the multiverse would be like trying to distinguish between the composition of two meteorites that hit the roof of a house solely by the sound of the impacts, without knowing how the house is constructed and with what materials.
There’s also the problem that even if you did see something, it really would tell you pretty much nothing about the supposed other universe:
Should a signature for a bubble collision be confirmed, Peiris doesn’t see a way to study another bubble universe any further because by now it would be entirely out of causal contact with ours. But it would be a stunning validation that the notion of a multiverse deserves a seat at the testable physics table.
Update: One problem with arguing that the multiverse is like the theory of evolution that physicists should keep in mind: creationists love it.
Peter, after following your blog for several years, I finally got round to reading your book, thank you – an exhilarating read!
I can’t help thinking of Copernicus adding epicycles to his heliocentric model of the solar system to avoid the ‘paradigm shift’ of Keplerian orbits.
Multiverse -> epicycles?
Phil Fogle,
Not sure it’s such a good analogy, with epicycles you at least have a rather well-defined, testable framework. Part of the problem with the multiverse is that you don’t even have a well-defined theory you can calculate anything with.
Glad you enjoyed the book!
If I can put a name on what concerns me with “this kind” of theories (strings, multiverse, parallel universes inter alia) is their theism.
Their fans glorify the Impossibility of Knowing, and they bask in it.
They are glad that the scientific method has finally found the position such a slut deserves (back to the kitchen) and they feast on the infidels.
Have we already past the point where enough is enough and their marks are already left on science for a couple of centuries? I don’t know. But hopefully in the end what will be remembered won’t be the silence of the friends.
Peter,
Is there any chance of sanity and the scientific method coming back to physics? With billionaires giving away money to theorists who have no testable results, it doesnt seem as though there is any feedback to prevent this thing from spiraling out of control. Any ideas how we might see theoretical physics become a science again?
On falsifiability: “Fossil rabbits in the Precambrian.”
Michael,
The problem isn’t billionaires. The choices of mathematicians were perfectly reasonable, and this year the physics prize went to an important experimental result, which I think had to do with a realization that the physics prize choices of theorists were becoming an embarrassment.
Many parts of theoretical physics are perfectly healthy, but the multiverse mania problem really is just getting worse, and it’s a problem generated by physicists themselves, not by the press and not by the billionaires. I have no idea what might slow it down or reverse the trend, keep thinking people will just get tired of listening to the same nonsense. Doesn’t seem to be happening though.
It is more than evident to any fair minded observer that this pop science multiverse mania harms fundamental progress in physics. It reminds me of the attitude of the of the faculty of the university I attended in the seventies that deterred me from continuing to be a math major.
This comparison with evolution theory is nonsense. From the fossil record (e.g. the faunal succession) and DNA it is evident that the biological species have not all come into existence at the same time as the Genesis fairy tale would have it, but in temporal succession. And that the fittest (in terms of adaptation to the environment) survive is seen all the time. To suggest that evolutionary theory is a tautology is BS. The theory of evolution is not at all like this multiverse nonsense for which there is no evidence at all. Peiris must be desperate to come with this “comparison”.
I suppose I must accept some of the blame myself. Subjects like unification and universal origins are intrinsically fascinating to me, and I keep going back to those subjects again and again in hopes of learning about the true answers to the deepest questions. This is in spite of the fact that there’s virtually no hope of any relevant prediction making contact with experiment.
Meanwhile robust and vital physics is being done in areas like calculating QCD phenomena from first principles, untangling the mysteries of high-temperature superconductivity, using quantum mechanics to speed up computation without worrying about all the dead cat nonsense. I.e. doing research that is constantly confronted with the unforgiving standard of nature as we know it exists. Such work is old, somewhat prosaic, fiendishly difficult, tends to yield only incremental progress over the span of careers and does almost nothing to satisfy the primeval desire to somehow understand “what it all means”.
Unfortunately, the multiverse is the only realm in which such spiritually satisfying pursuits are likely to flourish while I am alive. Maybe a bit like a habitual parishioner finally losing his faith completely, and facing the loss of the sense of certainty and wonder that faith once promised, I’m mourning. I used to love reading these gripping stories about strings and loops quantum proliferation. But it’s dead to me now, and the storytellers are not sages; they’re human just smarter-than-average beings who went far down the wrong path in pursuit of some standard of beauty they’ll never realize, and likely doesn’t even exist.
I’ll look forward to the LHC telling us a bit more about things like QCD matter and the properties of the Higgs. I’ll try to be more appreciative of the real science being done, and give the time and consideration people doing such difficult and important work are due. I’ll once-and-for-all tell multiversalists where they can shove it.
The comment about evolution is so ignorant that I can’t even be bothered to de-construct it. Just about the only good thing left to say about these stringy multiuniversalists is that they serve as an example and warning of the pathology that happens to the natural sciences when they get separated from nature and observation.
I just wish that they wouldn’t try take to take biology, chemistry, condensed matter physics and other forms of science still following scientific method down to their path into pseudo-science and metaphysics.
LMMI,
I don’t think it’s at all necessary to only pay attention to ideas that are experimentally testable. Actually, testability in itself is not the real problem with the multiverse. The problem with the multiverse is that it’s inherently an empty idea, devoid of explanatory power, being invoked as an excuse for failure. In fundamental physics, there are a small number of questions we don’t understand, and there’s nothing wrong with speculative work with a long-term goal of understanding those, but now far away from useful contact with experiment. As an example: there’s a huge amount we don’t understand about QFT, and trying to improve that situation is very worthwhile, even if dealing with questions about QFT not relevant to experimental tests.
The problem is that this kind of hard work has trouble competing with hucksters who claim that they already have the answers. Such hucksters are always going to get on TV shows, the disturbing trend is that they’re now starting to get real traction in the scientific community itself. Dealing with this I fear is not a problem for the public, but a problem for scientists themselves.
Thr multiverse interpretation I think is a primary example of an empty or bad explanation like the Ancient Greek Myth of Persephone as an explanation for the seasons. It was specific/testable, but not truly falsifiable because you could ways move the goalpost or alter something without questioning the main idea.
Actually, Persephone was falsifiable, with a trip to the southern hemisphere where it is summer in january. The multiverse has lots of explanatory power. It can “explain” everything, and therefore nothing.
Peiris’ take on evolutionary theory serves to show exactly two things: his utter ignorance and arrogance. unfortunately, physicists are derided as arrogant by many of the practitioners of the so-percieved “less hard sciences” and this is a perfect example why.
I wonder whether she realizes how much harm she does to the credibility of science with statements like these. Or if she even cares, for that matter.
The tautology that Hiranya Peiris has in mind is “the survival of the fittest”. I.e. “they survived because they were fit and we know that they were fit because they survived”. In the context of evolution that is a tautology but it is not quite the same as Peiris’ garbled “an organism exists because it survived” .
“One problem with arguing that the multiverse is like the theory of evolution that physicists should keep in mind: creationists love it. ”
Let’s just keep them out of the argument. Saying that this or that theory is unacceptable because creationists like it is no better than saying that the multiverse is true because is supports atheism (which is Susskind’s position.)
See http://en.wikipedia.org/wiki/Association_fallacy
The “epicycles” analogy is an interesting one. However I think it is an analogy that applies to the Standard Model rather than the Multiverse. The arbitrary terms of the SM could be considered similarly to planetary epicycles, motivating one to look for a deeper model underneath which may explain why the terms are what they are.
Unfortunately the Multiverse says you can have any “epicycles” you like. No further explanation necessary!
There is only one hope out of this multiverse/dimensions mania. Let the real falsifiable quantum theory of gravity show up.
“Let’s just keep them out of the argument. Saying that this or that theory is unacceptable because creationists like it is no better than saying that the multiverse is true because is supports atheism”
I am not so sure I agree. I think it is very important to understand why creationists like the Multiverse so much. It is not that they believe in it, they like it because it so seriously discredits the anthropic principle.
Mike Sharples,
It’s not that creationists like the multiverse or care about the anthropic principle. What they (or at least some of them) do like is when prominent physicists announce that the theory of evolution and an obviously pseudo-scientific theory have the same status.
Just wondering… who exactly is investing the big money on such infomercials?
B’Rat,
I don’t think filming a physicist talking in an exotic location and throwing in a few special effects is really all that expensive. So, this infomercial probably didn’t cost a lot to produce, and it’s being shown repeatedly on cable channels, funded by commercials and your cable fees. So, no big money needed, it’s just the usual sort of project that TV production companies do all the time.
Actually the “tautology” argument really is just silly, and shows up Peiris as at best completely uninformed. Biologists have of course known about that from the beginning, Stephen Gould talks about it quite a lot. “Survival of the fittest” is a tautology, but that’s not what evolutionary biologists talk about. They talk about natural selection, and how it operates on various traits. Simple Biologist would no doubt be able to give a much better explanation than I can, as a lowly mathematician, but it’s very clear that evolutionary biologists don’t use any sort of tautological arguments. It’s depressing that a high end physicist thinks they do.
Jeff M,
To me. the TOE _is_ tautological in the sense that it is so good that, if it were not true, that fact would require an explanation – that is, in the absence of experimental evidence directed for or against the TOE, one would expect it to be true. This would not, of course, be a true tautology but rather, it seems to be a prediction or consequence of already known science. The amazing discovery would be that the TOE was _not_ true, and we would have to search for an explanation.
OTOH, the falsity of the multiverse would require no explanation. One does not expect it to be true on the basis of uncontroversial science,
This would make the TOE completely dissimilar to the “gee whiz” multiverse, which is just an escape from the hard problem of understanding and explaining, in a verifiable way, the particulars of this physical reality which we have come to know and love, and for which we have more concrete evidence than that we can imagine it.
“To me. the TOE _is_ tautological in the sense that it is so good that, if it were not true, that fact would require an explanation – that is, in the absence of experimental evidence directed for or against the TOE, one would expect it to be true.”
You must be joking. This is not a scientific argument. It reminds me of arguments for the existence of god – or communism – or scientology.
All,
Not much point in arguing about the possibility of a self-evidently true TOE, all that’s clear now is that no one has a candidate for such a thing. And if there were such a thing, I don’t think it would be “tautological”, but rather some sort of opposite of tautological, not telling us nothing new, but telling us everything.
“I haven’t seen anything using Planck data released so far.” Lloyd Knox of UC Davis gave a popular talk last week about the Cosmic Microwave Background as observed by the Planck spacecraft. At the end of the talk someone asked him about this (multiverse collisions) and he stated that they had seen no evidence to support this.
Dear Peter, this multiverse nonsense is more than I can bear. How can serious people throw our trade in the garbage bin on selling nonsensical emptiness? They also make me look like a fool, I am in the same trade, called physics.
But one thing is clear already: the many worlds idea about quantum mechanics is a mistaken, nonsensical issue. I spent 15 years on studying what goes on in quantum measurements, the only point of contact between the quantum framework and the reality of tests in detectors. We have good results and a good picture of what goes on. What is very clear: the many worlds idea comes in nowhere and it has nothings to to with the whole subject. It is a lot of talking about a misconceived structure of the theory. You better adopt the ensemble interpretation, and for those who don’t like that, let me add: Einstein worked on it, even in his last year.
Mike Sharples,
“Unfortunately the Multiverse says you can have any “epicycles” you like. No further explanation necessary!”
In a sense this is true. But I’m guessing the folks in favor of the multiverse argue that what makes the multiverse explanations for things possible is string theory with its myriad of ways the extra dimensions can compactify. Presumable, string theorists are hoping that eventually we will understand string theory much better, and be able to understand the mechanism by which a multiverse is generated as well as what makes each “universe” take on the specific set of laws it takes on.
But perhaps in the distant future, some theory (be it string theory, or something completely different) will come along and do a superb job at explaining everything we see around us, unifying gravity and quantum mechanics, and all the particles and interactions. Perhaps it will be validated by many experiments. But if it predicts a multiverse, then that would be very strong (indirect) evidence in favor of a multiverse. Perhaps this theory will rely on the multiverse explanation for at least one parameter that we observe (eg, dark energy). If the multiverse exists, then I suppose that’s the closest we can come to showing it exists.
David,
Sure, if you have a well-tested theory that implies a multiverse, that would be a good reason to believe it. With string theory though, this is being used the other way around, with the multiverse given as the reason for not being able to test it.
Theo,
I pretty much agree with you about the many worlds interpretation. But I hope people who want to argue about that will wait for a post where it’s the topic, which I’ll get around to some day…
Peter Orland,
“You must be joking. This is not a scientific argument. It reminds me of arguments for the existence of god – or communism – or scientology.”
It’s not a scientific argument for what?
I said that one would *expect* the TOE to be true and that if it turned out not to be (obviously implying experiments) one would need to know why. That is not an argument either …
Wait a minute, I know what’s wrong. I used “the TOE” to mean “theory of evolution” and you (and Peter W) took it to mean “the theory of everything”.
(slapping forehead)
I was trying to outline a substantial difference between the type of theory that was the theory of evolution, before it was established through research, and these theories of everything that are making physics look like a carnival side show. The reason I am doing it is that the comparison was made in the article referenced above.
Sorry about the misunderstanding, Nobody.
Nobody,
Funny. I thought the particle physicist’s had a trademark on “TOE”…
“One problem with arguing that the multiverse is like the theory of evolution that physicists should keep in mind: creationists love it.”
Not just they love it. The cited argument is the so called ‘tautology argument’.
http://www.talkorigins.org/faqs/evolphil/tautology.html
Can’t find the right words.
Dear Dr Woit
.
You really shouldn’t tell us what Creationists think.
Unless you like telling us stuff that’s wrong.
.
I’m a Creationist.
I like the multiverse for this reason:
If the multiverse is the best case that Atheists can offer, Creationism is in the catbird seat.
Peter,
As bad as you think these “theorists” are I don’t even think you fully realize the negative impact they have and are making. Science has become religion. Peer review has become the new authority…etc
Umm … there’s no evidence for any multiverse in the BICEP2 data.
If they mean evidence for inflation, inflation doesn’t require a multiverse. Even the Linde eternal inflation idea is not the modern multiverse concept, which comes from trying to save string theory from itself.
Meanwhile, while there’s no string cosmology, “string-inspired” cosmology has a hard time predicting inflation. If the next round of precision CMB measurements do confirm anything like what BICEP2 reported, string theory will have suffered another mortal blow.
How this is related to Darwin’s natural and other mechanisms of selection and evolution is beyond me. Unobservable multiverses, mutually disconnected, don’t “compete” in the same ecosystem and have nothing to adapt to. From a mathematical point of view, there’s no defined space of possibilities, or measure on that space. How do you compute probabilities?
I know, I know — I just don’t appreciate the poetry of it.
Peter, you wrote: “The problem of course with bubble collision “predictions” are that they’re not falsifiable. As far as they’re concerned, you can only win: seeing nothing doesn’t disprove the multiverse.” There’s not really anything wrong with this kind of search for corroborating evidence though, really. I mean, what’s the difference between that and, say, someone hunting for exoplanets in 1960? It was theorized that other stars should have planets, and until we had better equipment no one would have suggested in 1960 that not finding any was proof that there were none out there. But if there *happened* to be one big enough and near enough that a telescope in the 60s could see it, well great. The hypothesis that there were exoplanets was not falsifiable in 1960, but someone could have proved it if they’d got lucky. By analogy, some people think we live in a bubble universe that could in the past have intersected with another bubble, leaving a trace. If we find such a trace, that will be a pretty good data point. If we don’t–well you’re right, we don’t learn anything from that, because maybe the hypothesis is wrong, or maybe the traces are too far in our past, or maybe we’re not looking right, or maybe our bubble is still a “virgin”. But does that really mean no one should be allowed to look for the traces in the first place? There are probably better examples than exoplanets… counterexamples to the Riemann hypothesis? If we look and don’t find one, we haven’t learned anything. Should we not bother looking, then, because it’s a search that can only result in winning or stalemate, but never losing? Or SETI signals–no one will ever be convinced no one else is out there just because SETI doesn’t find any signals. Does that mean they shouldn’t even look? etc. etc.
I mean I agree there’s no evidence at all to believe that our bubble ever intersected another, or even that there were ever any other bubbles coexisting with ours in the first place. But you can’t also blame people exploring these ideas for actually going and looking for evidence – surely that can’t be a bad thing?
Monty: a better analogy is philosopher Auguste Comte (1798-1857) who (prior to the discovery of emission and absorption line spectra from various elements in sunlight) claimed it impossible to ever know the composition of the sun, because it’s too hot to visit and sample. This is typical of defective “no go theorems,” which only get “accepted” without scrutiny because nobody has the time or inclination to argue over them. Woit and others are not, however, claiming to disprove and discredit all research on certain topics that are currently unproductive; rather they are trying to deflate the hype from populist speculations that are way overblown in the media.
Monty. As I understand it, the problem is not speculation and trying to find things out, it is partly presenting science fiction as science fact and partly suggesting that anything we don’t have an answer for is “Because Multiverse”.
“There’s not really anything wrong with this kind of search for corroborating evidence though, really.”
There’s nothing wrong with looking to see what’s there – in fact it’s necessary, but since you put it that way (“corroborating evidence”), what is it that you are trying to “corroborate”? Do you have any falsifiable predictions about the signal or is it “anything surprising will do”? If you can’t make a falsifiable prediction then you can’t use unpredicted results as a “corroboration” of an existing scientific theory.
So what is the theory and what observations does it predict?
How would an unexpected, unpredicted, structure in the sky “corroborate” an existing theory that makes no predictions any more than the existence of specific constants in our familiar world, which constants have never been derived from an over-arching theory that survives Occam’s razor, “corroborates” the multiverse? How would your multiverse theory without predictions be any better than “God set it up that way”?
A large scale, unpredicted, structure is nothing. Were such a thing found, you would have to write a theory simpler than the result and then verify it through its predictions. You aren’t at the first step of that. You haven’t even begun. You haven’t found something unknown to explain.
You multiverse lovers are already involved in overwrought promotion of fantasy as fact in the popular press. I dread the impact of an actual discovery on that existing, shameless performance, but _I_ predict that, should that happen, there will be an overnight cobbling up of some BS theory which would magically be much easier for our geniuses to arrive at than a theory explaining the parameters of our known laws, especially since multiverses are so fascinating to the gullible. Thinking will come later.
Oh wait, I forgot – the parameters of our laws have already been explained by the multiverse theory, as a consequence of its 3rd law – “whatever is, is”.
Kaku’s a good at this TV stuff. Perhaps you can arrange, beforehand, for him to explain how the multiverse is proven the very evening after something unknown is discovered or even better, he could explain it the day before as he already is.
As for exoplanets, their existence is a straightforward expectation from known theory. The form of an exoplanet’s signal was predictable and easily separable from spurious results. The discovery of their signal confirmed what was predicted and is providing fine tuning detail.
Monty,
Of course I’m not arguing one shouldn’t look, but just pointing out this is not a falsifiable test of the theory, and when, as everyone expects, nothing is found, no one will report on this or pay any attention.
“The theory of evolution, Peiris argues, also resembles a tautology in certain respects — “an organism exists because it survived” — yet it holds tremendous explanatory power.”
“an organism exists because it survived” is an observation, not a theory. It is an inaccurate re-statement of survival of the fittest (inaccurate in part because survival of the fittest works on populations over generations – it doesn’t describe an individual organism), which is a somewhat misleading phrase describing the process of natural selection. Natural selection is quite testable and verifiable, even if the biochemical mechanisms behind natural selection were not known for a long time after On The Origin of Species was published; indeed, On The Origin of Species itself has a lot of evidence for natural selection. On The Origin of Species, 1st edition 5th edition, with a definition of “Survival of the Fittest”
Finally, natural selection itself is only a subset of the modern theory of evolution. Mutation bias (some mutations are biochemically more likely to occur than others), as one example, is also part of the theory of evolution which is not part of natural selection. Sample source on Mutation bias )
So Peiris is arguing using an inaccurate re-statement of a misleading description of a portion of the theory he’s claiming that he’s describing to attempt to buttress a particular theory.
I personally never found the concept of the multiverse to be beautiful, though I was willing to accept it as a grim reality. We should be relieved if the multiverse were universally accepted as bunk. There is plenty left to ponder and strive for without chalking up every event as “bound to happen somewhere in the multiverse.”