For all practical purposes. From the author of Lost in Math: How Beauty Leads Physics Astray, at her blog BackRe(Action) According to Penrose’s conformal cyclic cosmology, the universe goes through an infinite series of “aeons,” each of which starts with a phase resembling a big bang, then forming galactic structures as usual, then cooling down as stars die. In the end the only thing that’s left are evaporating black holes and thinly dispersed radiation. Penrose then conjectures a slight change to particle physics that allows him to attach the end of one aeon to the beginning of another, and everything starts anew with the next bang. This match between one aeon’s end and another’s beginning necessitates the introduction of a new Read More ›

The physicist who answers is Sabine Hossenfelder, author of Lost in Math: How Beauty Leads Physics Astray (2018) and she responds, saying (among other things) If you want every elementary particle to each have a universe inside, you need to explain why we only know 25 different elementary particles. Why aren’t there billions of them? An even bigger problem is that elementary particles are quantum objects: They get constantly created and destroyed and they can be in several places at once. How would structure formation ever work in such a universe? It is also a generally the case in quantum theories that the more variants there are of a particle, the more of them you produce. So why don’t we produce Read More ›

Modified gravity is a hypothesis (1983) that attempts to account for the gravitational pull that is otherwise attributed to dark matter (which has never been identified). From Sabine Hossenfelder, author of Lost in Math: How Beauty Leads Physics Astray, at : Which one is right? We still don’t know, though astrophysicists have been on the case since decades. Ruling out modified gravity is hard because it was invented to fit observed correlations, and this achievement is difficult to improve on. The idea which Milgrom came up with in 1983 was a simple model called Modified Newtonian Dynamics (MOND). It does a good job fitting the rotation curves of hundreds of observed galaxies, and in contrast to particle dark matter this model Read More ›

From Ethan Siegel at Forbes: So why do so many theoretical physicists write papers about the multiverse? About parallel Universes and their connection to our own through this multiverse? Why do they claim that the multiverse is connected to the string landscape, the cosmological constant, and even to the fact that our Universe is finely-tuned for life? Because even though it’s obviously a bad idea, they don’t have any better ones. … As I’ve explained before, the Multiverse is not a scientific theory on its own. Rather, it’s a theoretical consequence of the laws of physics as they’re best understood today. It’s perhaps even an inevitable consequence of those laws: if you have an inflationary Universe governed by quantum physics, Read More ›

From John Timmer at Ars Technica: LIGO’s detection of gravitational waves came almost exactly a century after Einstein had formulated his general theory of relativity and an ensuing paper mathematically describing the possibility of gravitational waves. Or at least that’s the story as it was presented to the public (including by yours truly). And in some ways, it’s even true. But the reality of how relativity progressed to the point where people accepted that gravitational waves are likely to exist and could possibly be detected is considerably more complicated than the simple narrative described above. In this week’s Nature Astronomy, a group of science historians lays out the full details of how we got from the dawn of relativity to Read More ›

From Columbia mathematician Peter Woit at Not Even Wrong: New Scientist today has a feature article headlined How to think about… The multiverse The idea of an infinite multitude of universes is forced on us by physics. It starts off quoting Sean Carroll: “One of the most common misconceptions is that the multiverse is a hypothesis,” says Sean Carroll at the California Institute of Technology in Pasadena. In fact, it is forced upon us.”It is a prediction of theories we have good reason to think are correct.” The problem with this claim is that it’s simply not true. There is no model that “we have good reason to think [is] correct” that predicts a multiverse of universes with different physics Read More ›

In a world where some researchers earnestly study the question of why so many people don’t ”trust science,” we learn from Michael Marlow & Edward Archer at RealClearScience: In contrast [to confidence in politicians], public confidence in the ‘scientific community’ runs at 40% and has remained stable since the 1970s. This trust, however, turns out to be seriously misplaced when it comes to the government’s data on what we eat and drink. The nutrition research methods of the Centers for Disease Control and Prevention (CDC) and the US Department of Agriculture (USDA) are based on the naïve but politically expedient notion that a person’s usual diet can be measured simply by asking what he or she remembered eating and drinking. Read More ›

From the University of Bonn: A new study found a way to determine whether the mysterious “star putty” really exists Researchers at the University of Bonn and the University of California at Irvine used sophisticated computer simulations to devise a test that could answer a burning question in astrophysics: is there really dark matter? Or does Newton’s gravitational law need to be modified? The new study, now published in the Physical Review Letters, shows that the answer is hidden in the motion of the stars within small satellite galaxies swirling around the Milky Way. Using one of the fastest supercomputers in the world, the scientists have simulated the matter distribution of the so-called satellite “dwarf” galaxies. These are small galaxies Read More ›

From Daniel Sarewitz at the Weekly Standard, reflecting on Sabine Hossenfelder’s Lost in Math: How Beauty Leads Physics Astray, … What, then, joins Hossenfelder’s field of theoretical physics to ecology, epidemiology, cultural anthropology, cognitive psychology, biochemistry, macroeconomics, computer science, and geology? Why do they all get to be called science? Certainly it is not similarity of method. The methods used to search for the subatomic components of the universe have nothing at all in common with the field geology methods in which I was trained in graduate school. Nor is something as apparently obvious as a commitment to empiricism a part of every scientific field. Many areas of theory development, in disciplines as disparate as physics and economics, have little contact Read More ›

  From astrophysicist Ethan Siegel, reviewing Sabine Hossenfelder’s new book, Lost in Math: How Beauty Leads Physics Astray, at Forbes: The history of physics is filled with great ideas that you’ve heard of, like the Standard Model, the Big Bang, General Relativity, and so on. But it’s also filled with brilliant ideas that you probably haven’t heard of, like the Sakata Model, Technicolor theory, the Steady State Model, and Plasma Cosmology. Today, we have theories that are highly fashionable, but without any evidence for them: supersymmetry, grand unification, string theory, and the multiverse. … Yet unlike in the past, these dead-ends continue to represent the fields in which the leading theorists and experimentalists cluster to investigate. These blind alleys, which have Read More ›

And Sabine Hossenfelder, author of Lost in Math: How Beauty Leads Physics Astray, can just suck it up. From IAS director Robbert Dijkgraaf at Quanta: Scientists seek a single description of reality. But modern physics allows for many different descriptions, many equivalent to one another, connected through a vast landscape of mathematical possibility. The current Standard Model of particle physics is indeed a tightly constructed mechanism with only a handful of ingredients. Yet instead of being unique, the universe seems to be one of an infinitude of possible worlds. We have no clue why this particular combination of particles and forces underlies nature’s structure. Why are there six “flavors” of quarks, three “generations” of neutrinos, and one Higgs particle? Furthermore, the Read More ›

They used to be a regular stop for news of crackpot cosmology. From Dan Falk at NBC, discussing Sabine Hossenfelder`s new book, Lost in Math: How Beauty Leads Physics Astray (June, 2018): But the new century brought a rough patch. Yes, there have been some remarkable findings, including the 2012 discovery of the Higgs Boson and the discovery of gravitational waves four years later. But those triumphs were based on theories developed decades earlier — a full century earlier in the case of gravitational waves. And new ideas like string theory (which holds that matter is made up of tiny vibrating loops of energy) remain unverified. “All of the theoretical work that’s been done since the 1970s has not produced a single successful Read More ›

From Sabine Hossenfelder at her blog BackRe(Action), responding to a physics major who has heard from cosmologist Brian Greene that string theory can be a grand theory of everything: Greene states very carefully that superstring theory “has the capacity to embrace” gravity as well as the other known fundamental forces (electromagnetic, weak, and strong). What he means is that most string theorists currently believe there exists a specific model for superstring theory which gives rise to these four forces. The vague phrase “has the capacity” is an expression of this shared belief; it glosses over the fact that no one has been able to find a model that actually does what Greene says. Superstring theory also comes with many side-effects Read More ›

Asks Columbia mathematician Peter Woit at Not Even Wrong: University press offices and grant agencies put out irresponsible hype about the work of one their faculty or grantees. In this case, it’s Taming the multiverse: Stephen Hawking’s final theory about the big bang from Cambridge, and Stephen Hawking’s last paper, co-authored with ERC grantee Thomas Hertog, proposes a new cosmological theory, in which universe is less complex and finite from the European Research Council. And, of course, pop science media run with it, even if it’s old and debunked news. Woit laments, This is rather depressing, making one feel that there’s no way to fight this kind of bad science, in the face of determined efforts to promote fake physics Read More ›

From ScienceDaily: The theory of eternal inflation that Hawking and Hertog put forward is based on string theory: a branch of theoretical physics that attempts to reconcile gravity and general relativity with quantum physics, in part by describing the fundamental constituents of the universe as tiny vibrating strings. Their approach uses the string theory concept of holography, which postulates that the universe is a large and complex hologram: physical reality in certain 3D spaces can be mathematically reduced to 2D projections on a surface. … Hertog and Hawking used their new theory to derive more reliable predictions about the global structure of the universe. They predicted the universe that emerges from eternal inflation on the past boundary is finite and Read More ›