A study challenged the evidence for the mysterious antigravitational force known as dark energy. Then cosmologists shot back.
Category: cosmology – Page 342
Teams have looked for a “fifth force” in the universe within the Earth’s mantle, ultra-vacuum chambers, and in hypothetical particles such as “X17.” Finding it could help explain mysteries around dark matter and dark energy.
A physicist from RUDN University has proposed a new theoretical model for the interaction of spinor and gravitational fields. He considered the evolution of the universe within one of the variants of the widespread Bianchi cosmological model. In this case, a change in the calculated field parameters led to changes in the evolution of the universe under consideration. Upon reaching certain values, it began to shrink down to the Big Bang. The article was published in the journal The European Physical Journal Plus.
The spinor field is characterized by its behavior in interaction with gravitational fields. Dr. Bijan Saha of RUDN University focused on the study of a nonlinear spinor field. With its help, he explained the accelerated expansion of the universe. The study of a spinor field with a non-minimal coupling made it possible to describe not only the expansion of the universe, but also its subsequent contraction and the resulting Big Bang within the framework of the standard Bianchi cosmological model.
The basic calculations performed by Bijan Saha allow moving away from the isotropic model of the Friedman-Robertson-Walker universe (FRW) that is most often used. According to this traditional model, the properties of the universe are independent of the direction in which they are considered. The physicist has put forward an alternative: an anisotropic model in which such dependence exists. On the one hand, the “classical” isotropic model describes the evolution of the modern universe with great precision. On the other hand, there are theoretical arguments and observational data that lead to the conclusion that an anisotropic phase existed in the distant past.
Sean Carroll is a theoretical physicist at the California Institute of Technology. He specialises in quantum mechanics, gravitation, cosmology, statistical mechanics and foundations of physics. His latest book is Something Deeply Hidden: Quantum Worlds and the Emergence of Spacetime (2019). He lives in Los Angeles.
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If you were to travel back in time to kill your grandparents — let’s ignore the ‘why’ here, for the sake of argument — you would never have been born. Which means there was nobody to kill your grandparents. Which means you were actually born after all, which… hold up, what’s going on here?!
These kinds of brain-breaking paradoxes have been puzzling us forever, inspiring stories ranging from “Back to the Future” to “Hot Tub Time Machine.”
Now, New Scientist reports that physicists Barak Shoshany and Jacob Hauser from the Perimeter Institute in Canada have come up with an apparent solution to these types of paradoxes that requires a very large — but not necessarily infinite — number of parallel universes.
Scientists thought the case of the cosmic rays’ source was closed, but new evidence cracks it wide open again.
Our home galaxy has a new, super-precise mass measurement: about 890 billion times the mass of our sun. That’s 3.9 tredecillion lbs. (1.8 tredecillion kilograms), a tredecillion being a 1 with 42 zeros after it, or 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000. That amounts to about 6 billion billion billion elephants, 296 quadrillion Earth masses or 135 times the mass of the supermassive black hole in the image released back in April.
Measuring the Milky Way’s mass presents some unusual difficulties, because we live in it. There’s no way to stick galaxies on scales, so researchers typically “weigh” galaxies by tracing the movements of stars inside the galaxies, which can reveal how the galaxy’s gravity is influencing those stars. But while anyone with a reasonably good telescope can spot the full Andromeda galaxy, most of the body of the Milky Way is hidden from us.
MIT physicists are reigniting the possibility, which they previously had snuffed out, that a bright burst of gamma rays at the center of our galaxy may be the result of dark matter after all.
For years, physicists have known of a mysterious surplus of energy at the Milky Way’s center, in the form of gamma rays—the most energetic waves in the electromagnetic spectrum. These rays are typically produced by the hottest, most extreme objects in the universe, such as supernovae and pulsars.
Gamma rays are found across the disk of the Milky Way, and for the most part physicists understand their sources. But there is a glow of gamma rays at the Milky Way’s center, known as the galactic center excess, or GCE, with properties that are difficult for physicists to explain given what they know about the distribution of stars and gas in the galaxy.
Crisis on Infinite Earths was seeing the destruction of the Multiverse — but there have been hints that it could be reversed in the end.