Lifeboat Foundation

According to a paper posted to the arXiv pre-print server last week, the difference between an everyday supermassive black hole and a space-time tunneling wormhole may be a lacing of dark matter. While it sounds like crank fodder of the sort that not infrequently winds up on arXiv, the idea may hold actual water.

The theory pertains to one particular proposed form of dark matter known as axionic dark matter. Axions, a hypothesized fundamental particle of matter relating to the strong nuclear force, aren’t the only proposed candidate for dark matter, but as searches for WIMPs (weakly-interacting massive particles)—far and away the favored proposed particle comprising dark matter—come up empty, axionic dark matter has become a more and more plausible scenario. As theorized, dark matter axions would permeate the universe as an energetic condensate, interacting only very weakly via the electromagnetic force and existing as a kind of ghostly cosmic foam.

Crucially, while individual axions would be very light, they would together make up enough mass to account for the dark matter halos that form the gravitational scaffolding of galaxies. Axions are currently being hunted for via experiments involving giant Earth-based mirrors.

In principle, nothing that enters a black hole can leave the black hole. This has considerably complicated the study of these mysterious bodies, which generations of physicists have debated since 1916, when their existence was hypothesized as a direct consequence of Einstein’s Theory of Relativity. There is, however, some consensus in the scientific community regarding black hole entropy—a measure of the inner disorder of a physical system—because its absence would violate the second law of thermodynamics. In particular, Jacob Bekenstein and Stephen Hawking have suggested that the entropy of a black hole is proportional to its area, rather than its volume, as would be more intuitive. This assumption also gives rise to the “holography” hypothesis of black holes, which (very roughly) suggests that what appears to be three-dimensional might, in fact, be an image projected onto a distant two-dimensional cosmic horizon, just like a hologram, which, despite being a two-dimensional image, appears to be three-dimensional.

As we cannot see beyond the event horizon (the outer boundary of the back hole), the internal microstates that define its entropy are inaccessible. So how is it possible to calculate this measure? The theoretical approach adopted by Hawking and Bekenstein is semiclassical (a sort of hybrid between classical physics and quantum mechanics) and introduces the possibility (or necessity) of adopting a quantum gravity approach in these studies in order to obtain a more fundamental comprehension of the physics of black holes.

Planck’s length is the (tiny) dimension at which space-time stops being continuous as we see it, and takes on a discrete graininess made up of quanta, the “atoms” of space-time. The universe at this dimension is described by quantum mechanics. Quantum gravity is the field of enquiry that investigates gravity in the framework of quantum mechanics. Gravity has been very well described within classical physics, but it is unclear how it behaves at the Planck scale.

Continue reading “Loop quantum gravity theory offers glimpse beyond the event horizon” »

Kathryn Zurek realized a decade ago that we may be searching in the wrong places for clues to one of the universe’s greatest unsolved mysteries: dark matter. Despite making up an estimated 85 percent of the total mass of the universe, we haven’t yet figured out what it’s made of.

Now, Zurek, a theoretical physicist at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), says thanks to extraordinary improvements in experimental sensitivity, “We increasingly know where not to look.” In 2006, during grad school, Zurek began to explore the concept of a new “Hidden Valley” model for physics that could hold all of the answers to dark matter.

“I noticed that from a model-builder’s point of view that dark matter was extraordinarily undeveloped,” she said. It seemed as though scientists were figuratively hunting in the dark for answers. “People were focused on models of just two classes of dark matter candidates, rather than a much broader array of possibilities.”

Dark matter is a mysterious substance composing most of the material universe, now widely thought to be some form of massive exotic particle. An intriguing alternative view is that dark matter is made of black holes formed during the first second of our universe’s existence, known as primordial black holes. Now a scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, suggests that this interpretation aligns with our knowledge of cosmic infrared and X-ray background glows and may explain the unexpectedly high masses of merging black holes detected last year.

“This study is an effort to bring together a broad set of ideas and observations to test how well they fit, and the fit is surprisingly good,” said Alexander Kashlinsky, an astrophysicist at NASA Goddard. “If this is correct, then all galaxies, including our own, are embedded within a vast sphere of black holes each about 30 times the sun’s mass.”

In 2005, Kashlinsky led a team of astronomers using NASA’s Spitzer Space Telescope to explore the background glow of infrared light in one part of the sky. The researchers reported excessive patchiness in the glow and concluded it was likely caused by the aggregate light of the first sources to illuminate the universe more than 13 billion years ago. Follow-up studies confirmed that this cosmic infrared background (CIB) showed similar unexpected structure in other parts of the sky.

Continue reading “Scientist suggests possible link between primordial black holes and dark matter” »

The Standard Models of particle physics and cosmology don’t add up to all there is. What might be the next giant leap forward?

The collapse of a trapped ultracold magnetic gas is arrested by quantum fluctuations, creating quantum droplets of superfluid atoms.

Macroscopic implosions of quantum matter waves have now been halted by quantum fluctuations. The quantum wave in question is an atomic Bose-Einstein condensate (BEC), a quantum state with thousands to tens of millions of atoms in an ultracold gas all sharing the same macroscopic wave function. Attractive atomic interactions can cause BECs to collapse in spectacular ways, in what’s been termed a “bosenova,” a lighthearted allusion to a supernova explosion [1]. Tilman Pfau and colleagues from the University of Stuttgart, Germany, have shown that for BECs made of dysprosium, whose bosonic isotopes are among the most magnetic atoms in the periodic table, long-range dipole-dipole interactions between these neutral atoms create a totally new phenomenon: the arrested collapse of a quantum magnetic fluid, called a quantum ferrofluid [2, 3]. Such a ferrofluid relies crucially on the strong dipolar interactions in the dysprosium gas.

A team of astronomers investigating “the most mysterious star in our galaxy” have launched a Kickstarter campaign, with hopes to raise $100,000 to find out “Where’s the Flux?”

Whether these Universes are similar or different to our own, whether they have the same physical laws and properties, whether they have the same fundamental constants, particles and interactions, we do not know.

And at the same time, our very best laws of nature tell us that this is reality: we are a tiny fraction of our observable Universe, which is a tiny bit of the unobservable Universe, which is just one of a tremendous number of Universes in a multiverse that’s constantly generating new ones, and has been for billions of years. And that’s the Multiverse we live in, to the best of our knowledge!

Continue reading “What is the Multiverse, and why do we think it exists?” »

Caltech theoretical physicist Sean Carroll explores what existed before the Big Bang in his new book, “The Big Picture.”

Produced by Delano Samuels and Jessica Orwig

Continue reading “The Big Bang is not the beginning of our universe — it’s actually the end of something else entirely” »