Multiverse

From Sedeer El-Showk at Nautilus: From the Muslim perspective, fine-tuning isn’t a problem, but rather an example of the beauty and order of the cosmos. Multiverse proposals seem to willfully undermine this beauty, positing a plethora of universes to account for the observed characteristics of our universe. To Mimouni, the idea is also unscientific. “From an ontological point of view, it’s a catastrophe, because you’re proposing things you can never observe, universes that are causally disconnected from our universe,” he says. “In fact, it’s against the philosophy of science as we understand it because it talks about entities that can never be studied or have their existence proven.” More. Got it in one. The multiverse is not only “not science.” Read More ›

From Ben Freivogel at Nautilus: If the multiverse is large and diverse enough to contain some regions where dark matter is made out of light particles and other regions where dark matter is made out of heavy particles, how could we possibly predict which one we should see in our own region? And indeed many people have criticized the multiverse concept on just these grounds. If a theory makes no predictions, it ceases to be physics. Freivogel nonetheless thinks that the multiverse is the physicist’s friend: Theoretical and observational evidence suggests that we are living in an enormous, eternally expanding multiverse where the constants of nature vary from place to place. In this context, we can only make statistical predictions. Read More ›

From Shannon Hall at New Scientist: So where are these unseen universes in relation to ours? How many are there? What goes on inside them? And can we ever hope to visit one? Such questions might sound daft, particularly given the lack of observational evidence that the multiverse exists. And yet thanks to new ideas on where distant universes might be hiding or how to count them, physicists are beginning to get their bearings. Rather fittingly, though, there is not just one answer – depending on which version of the multiverse you’re navigating, there are many. (paywall) More. [colour emphasis added] Question: “New pics from Pluto, including strange, icy haloes” sounds like science, a matter of public interest. “How far away Read More ›

 In a review of Max Tegmark’s 2015 book, Our Mathematical Universe: My Quest for the Ultimate Nature of Reality, mathematician Daniel Kleitman observes at Inference: Tegmark’s chief argument now follows. Our local universe arose through the process of inflation; since this inflation happened, it had a finite non-zero probability of happening. In an infinite universe, inflation must have taken place infinitely often. There must therefore be an infinite number of local universes. Tegmark then claims that, since you also have a finite non-zero probability of existing in the infinite universe, there must be infinitely many copies of you in the other local universes. He then weakens his claim, though he does not acknowledge this, by pointing out that the physical Read More ›

From Tasneem Zehra Husain at Nautilus: It’s not the immensity or even the inscrutability, but that it reduces physical law to happenstance. Not just a feature, a benefit. I am not alone in my ambivalence. The multiverse has been hotly debated and continues to be a source of polarization among some of the most prominent scientists of the day. The debate over the multiverse is not a conversation about the particulars of a theory. It is a fight about identity and consequence, about what constitutes an explanation, what proof consists of, how we define science, and whether there is a point to it all. … The multiverse is less like a closed door and more like a key. To me, Read More ›

From Nobelist and multiverse proponent* Steven Weinberg at New York Review of Books: Many physicists came to think that the reaction of Einstein and Feynman and others to the unfamiliar aspects of quantum mechanics had been overblown. This used to be my view. His view has changed to: The introduction of probability into the principles of physics was disturbing to past physicists, but the trouble with quantum mechanics is not that it involves probabilities. We can live with that. The trouble is that in quantum mechanics the way that wave functions change with time is governed by an equation, the Schrödinger equation, that does not involve probabilities. It is just as deterministic as Newton’s equations of motion and gravitation. That Read More ›

Here. Our goal is to consolidate the idea of fine-tuning across disciplines such as biology, chemistry, and physics. Fine-tuning is often deemed a fact and used to reach grandiose metaphysical conclusions by philosophers, theologians, and even physicists, without a proper understanding of the underlying assumptions entailed by these arguments. As a consequence the physical and philosophical literature on this subject are rather confusing, leading to esoteric topics such as Boltzmann Brains. We intend to present a comprehensive review of the physics used for deriving fine-tuning arguments, scrutinising the current ones and uncovering new examples, thereby providing a solid foundation for future efforts to interpret this fascinating facet of Nature. We will produce a field-manual for fine-tuning and create an accompanying Read More ›

From Peter Woit at Not Even Wrong: Back in 2013 one could read lots of claims in the media that “Hard evidence for the multiverse” had been found, based on “effects of quantum entanglement between our horizon patch and others”. These claims were discussed on this blog (with a response from the authors here). A new paper by Will Kinney has now been published in JCAP, including the following conclusion about such claims: It is worthwhile to discuss in general the “concrete predictions” originally claimed by the authors of refs. [1,2], since several key claims do not survive even cursory scrutiny. For example, the discontinuity in the effective potential claimed to be correlated with voids and the CMB cold spot Read More ›

From Sarah Lewin at LiveScience: Space.com talked with Adam Frank, an astrophysicist at the University of Rochester in New York who consulted on “Doctor Strange,” about how the movie’s magic of the mind fits in with the more science-grounded (comparatively!) worlds introduced previously, the concept of the multiverse and what science philosophy has to do with superheroes. … In general, the multiverse idea is very much built into the Marvel comics; Marvel has Earth 226A, Earth 213B … You can expect it to show up in different places. What’s interesting about the Marvel universe is, they would have these characters which would be the embodiment of impersonal forces. There’s a character who’s like, “I’m Eternity,” and he’s represented as this Read More ›

From University of Sydney: We invite you to the 2016 Fine-tuning, the Multiverse and Life Workshop, hosted at the University of Sydney. Issues of fine-tuning and naturalness are central to evaluating such physical and cosmological theories as inflation and extension to the Standard model of particle physics, including supersymmetry. In addition, our values of the fundamental constants of nature have the seemingly rare ability to support the complexity required by life. This has become an important way to test multiverse theories: the predicted observed value of fundamental “constants” depends on the values that permit the existence of observers. In light of these challenges, this workshop will bring together physicists, cosmologists, astronomers and philosophers of science for two days of invited Read More ›

From New Scientist on our universe’s five most startling coincidences: 1. Dark matter and energy balance 2. Universe lines up along “axis of evil” 3. Universe flat as a pancake 4. Space is all the same temperature 5. Higgs boson keeps the universe stable Having decided that these cirumstances are not coincidences, the New Scientist staff happily burble, One idea explains all the weird coincidences in the universe Don’t believe in coincidences but stuck for an explanation? Time to call up the anthropic principle and the multiverse … Why believe in the multiverse? Because a process such as inflation (see “The universe is flat as a pancake. Coincidence?“), if left unchecked, could produce a multitude of causally disconnected universes. String Read More ›

From Sabine Hossenfelder at Forbes: … the LHC found the Higgs but no evidence for anything new besides that. No supersymmetry, no extra-dimensions, no black holes, no fourth generation, nothing. This means that the Higgs-mass just sits there, boldly unnatural. Enter the multiverse. The multiverse idea states that there are infinite numbers of Universes like our own, and infinite ones with differences. Not only would anything that could happen actually happen in some universe within the multiverse, but anything that can happen would happen infinitely many times. Therefore, the multiverse also contains infinitely many universes that are almost exactly like our own, including our planet, and me, and you. But in some of these other universes, a dark matter particle Read More ›

From string theory skeptic Peter Woit at Not Even Wrong: The last talk of the [“C. N. Yang Institute for Theoretical Physics] event was a public talk by Ashoke Sen on What is String Theory? (slides here), one which made me think that maybe it wasn’t a bad thing that I hadn’t made it out to Stony Brook, since I might have been there for this. Sen’s talk was a depressing compilation of ancient hype and misleading claims about string theory, with the standard multiverse excuse for why it predicts nothing at all about particle physics. My time at the ITP coincided with the early years of this kind of string theory hype, which got started in late 1984, about Read More ›

In his September 22 release book, Universal: A Guide to the Cosmos. In an interview with The Guardian: How far are the dots apart for you to make that leap of understanding? The theory of inflation itself is almost nailed down. We teach it at undergraduate level, and the data supports it as far as we can tell. The idea of multiverses is not too big a leap from that. If that is right then you have essentially an infinity of universes and it follows there is a very natural, almost unavoidable mechanism for varying the laws of nature in each universe. Therefore the idea that we look out on a universe that has been waiting for us to appear in Read More ›

Responding to Barry Arrington’s comment that if The Atlantic thinks the multiverse is reaching its sell by date, surely the food waste dumpster looms, physicist Rob Sheldon comments, — That was a pretty ambiguous article, ending with a question. Because if the multiverse is a philosophy that is rotting culture, then we must dig down to its root, and ask “where did it come from?” I think, and we could probably ask 3 philosophers and get 4 opinions, that this multiverse concept is exactly what you expect from materialism. That is, the alternative to multiverse is NOT a determined, deterministic, Newtonian-Laplacian world. Nor is it a QM world of shadowy probabilities becoming realized by observation. Rather, the alternative to multiverse Read More ›