I haven’t yet seen a copy of Marcelo Gleiser’s new book, but this weekend the Wall Street Journal had a review by John Gribbin, author of the 2009 multiverse-promotional effort In Search of the Multiverse. I don’t know how Gleiser treats this, but Gribbin emphasizes the multiverse as new progress in science (for some reason he’s now calling it the “metaverse”):
Within the metaverse, the story goes, there are regions that form inflating bubbles. Our universe is one such region or bubble. As Mr. Gleiser explains, the implication is that there are other universes, other bubbles far away floating across an inflating sea.
This seemingly speculative idea counts as a genuine scientific hypothesis, because it makes testable predictions. If other “bubble universes” exist in the metaverse, it is possible that, long ago, one or more of them may have collided with our universe, like two soap bubbles touching and moving apart. One effect of such a collision, Mr. Gleiser points out, would be to make ripples in the space of both bubble universes; they would leave a distinctive if faint ring-shaped pattern, known as a “cosmic wake,” in the background radiation that fills the universe. Data from the Planck satellite is being used to test this prediction right now. Is the metaverse real? We may well know in the next year or so.
This seems to be a reference to work by Matthew Kleban and collaborators, which I saw Kleban talk about recently (see here). My impression from that talk is that the actual state of affairs with Planck is that it has already looked for and ruled out most hoped-for signals of “bubble collisions”. I don’t know anyone besides Gribbin who believes that the next round of Planck data is going to answer the question “Is the metaverse real?”.
The really odd thing about the review is that Gribbin uses the multiverse to argue that John Horgan’s claims about physics in The End of Science are wrong. This is just bizarre. Gribbin and his multiverse mania for untestable theories provides strong ammunition for Horgan, since it’s the sort of thing he was warning about. Actually, I don’t recall anything in Horgan’s book about the multiverse, and suspect the idea that physics would end up embracing such an obviously empty idea was something that even he didn’t see coming. As the multiverse mania gains strength, physicists are blowing past the “End of Science” to something that has left conventional science completely behind.
Update: I took a look again at a copy of The End of Science, and, as I remembered, the chapter on “The End of Physics” has no mention of the multiverse pseudo-explanation of why one can’t ever understand the parameters of the Standard Model. Horgan ends the chapter with a vision of physics descending into “ironic science”, endlessly studying untestable string theory models and interpretations of quantum mechanics. With the multiverse we may already have gone past that point.
In the next chapter though, “The End of Cosmology”, there’s a long section about Linde and his “self-reproducing universe theory”, so Horgan more than 20 years ago already was writing about the place we’re ending up. I was interested to see the comment he got at the time from Howard Georgi about this kind of model:
quite amusing. It’s like reading Genesis.
Georgi also is quoted as describing inflation as:
a wonderful sort of scientific myth, which is at least as good as any other creation myth I’ve ever heard.
Of course what is different now is that 20 years ago the theory establishment saw Linde’s multiverse as kind of a joke, not at all part of science. Things have changed…
Update: While my favorite local bookstore doesn’t have a copy of the Gleiser book The Island of Knowledge, you can see parts of it on Google Books. Searching on “multiverse” you can read chapters 15 and 16 of the book which deal with the issue of the testability of the string theory multiverse. Reading these shows that Gribbin seriously misrepresents what Gleiser has to say about the multiverse. The context of his discussion of “Cosmic Wakes” and the possibility of seeing them in the Planck data is to argue that even if this happened (which he describes as having an “extremely small” probability), all that would show is evidence for a neighboring universe, not a multiverse:
However, I stress again that even a positive detection of a neighboring universe would not prove the existence of a multiverse. Within the present formulation of physics the multiverse hypothesis is untestable, however compelling it may be. [Page 129]
A collision between two bubble-universes would have left huge ripples, unless their vacuum energies happen to be quasi-degenerate: searches ate done for this atypical fine-tuned scenario of small ripples because the typical scenario was already excluded.
The evidence crisis
“the next round of Planck data”: isn’t the Planck mission over? (wikipedia says it was deactivated in October 2013)
Or if there is still some data to be exploited, what is it?
Thanks
J,
Planck is still at work on the data analysis, especially on the polarization data, with rumors of release set for October. There is a lot of interest in this, around the question of whether there will be evidence for primordial B-modes in this data. Gribbin is the only person I know of though who seems to think that “cosmic wakes” from other universes, not seen in the rest of the Planck data, will somehow show up in the new polarization results.
In addition to writing about Linde in his book, Horgan’s discussed the context at least three different times I specifically recall (my impression is of even more) with science writer George Johnson on their occasional appearances together on Bloggingheads.tv (all of which can be retrieved at its current website).
One of the problems I have with Horgan on Linde is that he always has seemed to have trouble separating Linde as a social person from Linde as a scientist. He’d met Linde several decades back in the context of a sort of socializing that’s not unusual around conferences in places like Aspen, and what struck Hogan was the image of Linde as a gregarious party animal full of jokes and magic tricks. Hogan’s written and oral descriptions of his interviewing Linde combine that image with Linde’s speculations on the existence of a multiverse. The things Linde’s done otherwise, Horgan has never really dealt with (and to me he’s neither equipped nor inclined to discuss anyway), particularly Linde’s academic and research work on inflation in Russia more than a decade before Guth’s first paper on it was published, as well as Linde’s work in the U.S. in the 1980s following publication of Guth’s paper, which corrected a number of shortcomings in Guth’s hypothesis and otherwise expanded on its implications.
Avattoir,
I just reread earlier today the section of Horgan’s book dealing with Linde. He certainly does deal with Linde’s scientific work on inflation, in Russia, and post-Guth. Yes, his treatment of this is non-technical, but no more so than any of the rest of the book, which is not a technical book.
The material there on Linde does portray him as a bit of a joker, but it’s clearly there for color (this is a popular book, you want to keep people awake), and to give a bit of context to the things Linde says. For instance he quotes Linde going on about how maybe the universe was created by some cosmic engineer who created it in just such a way that a message for us to read would be encoded in the CMB. Without a context for Linde’s sense of humor, this would just come off as making Linde look crazy.
Georgi calls inflation an amusing myth? Surely the scientific consensus is that inflation is a strong candidate for how the universe operates. Is Georgi referring to something else or is his comment out of date?
Sry…Im just a layman who takes most everything literally.
abbyyorker,
Georgi does call it not an “amusing” myth, but a “wonderful” and “scientific” one. This was in the early-mid 1990s, after inflation had been around for a decade or so, and hadn’t lived up to its promise as telling us something about GUTs. I’d guess Georgi was referring to the lack of any compelling prospects at the time for testing the idea. I don’t know whether the more recent claims about connection to CMB experiment have changed his mind, or whether he’s in the Steinhardt camp on this.
Georgi’s take on inflation is all about the failure of GUTs, which he and Glashow started in the 1970s. From the point of view of cosmology, inflation is a perfectly viable and testable class of theories.
Horgan’s vision of an increasingly empty academic theoretical physics, titillated by speculative manias, has turned out to be depressingly relevant.
I got a review copy of Gleiser’s “Island of Knowledge” and I’m presently reading it (half through). I will probably have a review on my blog within the next weeks.
In March, Horgan wrote Why I Still Doubt Inflation, in Spite of Gravitational Wave Findings. He also posted My 1992 Profile of Cosmic Trickster and Inflation Pioneer Andrei Linde. So yes, inflation skepticism is part of his end-of-science theme.
It was a good review, but Peter’s post might have left a misimpression.
Gribbin uses the term “metaverse” to refer to the larger inflating background à la Linde. It’s not the “multiverse” as typically used, but a connected spacetime, and one connected to us. It’s likely that Gribbin was consciously avoiding “multiverse” so as to not give aid and comfort to that lunacy. The only error he makes is his implication that inflation requires the Linde-an metaverse or “eternal inflation.” It’s consistent with it, but Linde’s form of inflation is not required.
Gribbin’s review eschewed the “multiverse” term altogether and didn’t mention string theory at all. I find that pretty telling. Furthermore, Gribbin emphasizes the non- or anti-scientific nature of claims of a “final theory.” That’s the point of the book’s title, that our science is an island (a growing island, to be sure) in a sea of ignorance, probably an allusion to Newton’s famous quote.
(The only place “multiverse” occurs in the Journal review is mention of the title of Gribbin’s book, “In Search of the Multiverse,” in the author blurb at the end.)
Two would be already a multi-, no? 😉
“A collision between two bubble-universes”
What does that even mean? Wouldn’t ekpyrotic fire emerge from every single point in space? Or is that another framework? What about if a universe is a holographic representation from a lower dimensional manifold and THESE ram each other in the night? How about if a Tegmark Level III universe rams one that is Tegmark Level IV? I’m so confused. It’s like reading Perry Rhodan stories.
Horgan says: “Thanks, Peter. I couldn’t have said it better myself.“