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Category: physics – Page 148

The trouble starts when they attempt to beam up from a planet during an ion storm. Something goes wrong. They appear aboard the Enterprise, but things are askew: Crew members greet the captain with Nazi-style salutes, and First Officer Spock sports a goatee. Observing these small but significant differences, Kirk muses that the crew has materialized in “a parallel universe coexisting with ours on another dimensional plane.”

These days, one parallel universe is hardly enough for science fiction. Instead, it seems the entire multiverse is having its Hollywood moment. Films like Doctor Strange in the Multiverse of Madness and Everything Everywhere All at Once entice the viewer with multiple versions of various characters and a dizzying array of alternate realities. Though they’re not particularly heavy on the physics, these films are definitely latching onto something. The idea of the multiverse — the provocative notion that our universe is just one of many— has fully cemented itself in mainstream pop culture. (Or, at least, in the current phase of the Marvel Cinematic Universe.) Its appeal as a storytelling device is obvious. Just as time travel allowed Marty McFly to experience different timelines in the Back to the Future series, multiverse tales allow characters to explore a multitude of worlds with varying degrees of similarity to our own, as well as altered versions of themselves.

While Hollywood can’t seem to get enough of the multiverse, it remains deeply controversial among scientists. Ask a prominent physicist whether they believe in a multitude of universes beyond our own, and you’ll get either a resounding yes or a vehement no, depending on whom you encounter. Advocates on the two sides show no mercy toward each other in their books, on their blogs, and, of course, on Twitter. But physicists didn’t pull the idea out of thin air — rather, several distinct lines of reasoning seem to point to the multiverse’s existence, bolstering the idea’s merit. Sabine Hossenfelder, a theoretical physicist at the Frankfurt Institute for Advanced Studies, has called the multiverse “the most controversial idea in physics.”

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Observations of galaxy growth can be explained if the black holes at their centre contain dark energy, pointing to a possible role in the universe’s expansion.

Massive black holes could be the source of dark energy and the accelerating expansion of the universe, according to observations of ancient, dormant galaxies with black holes at their centre.

The laws of physics suggest that gravity should cause the universe to contract, but a mysterious force, which physicists call dark energy, seems to be counteracting this and making the universe expand at an accelerating rate.

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The discovery of gravitational waves (GWs) in the system has shown that this prediction made by Einstein 107 years ago is true. The findings also resulted in a revolution in the world of astronomy.

What Are Gravitational Waves?

According to Space, Einstein proposed that violent cosmic events, such as two black holes colliding with each other, may lead to space-time ripples called gravitational waves. Such waves can be observed across several light years.

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Observations of supermassive black holes at the centers of galaxies point to a likely source of dark energy—the ‘missing’ 70% of the universe.

The measurements from ancient and dormant show black holes growing more than expected, aligning with a phenomenon predicted in Einstein’s theory of gravity. The result potentially means nothing new has to be added to our picture of the universe to account for dark energy: black holes combined with Einstein’s gravity are the source.

The conclusion was reached by a team of 17 researchers in nine countries, led by the University of Hawai’i and including Imperial College London and STFC RAL Space physicists. The work is published in two papers in the journals The Astrophysical Journal and The Astrophysical Journal Letters.

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Over 50 percent of high-mass stars reside in multiple star systems. But due to their complex orbital interactions, physicists have a difficult time understanding just how stable and long-lived these systems are. Recently a team of astronomers applied machine learning techniques to simulations of multiple star systems and found a new way that stars in such systems can arrange themselves.

Classical mechanics has a notorious problem known as the three-body problem. While Newton’s laws of gravity can easily handle calculations of the forces between two objects and their subsequent evolution, there is no known analytic solution when you include a third massive object. In response to that problem, physicists over the centuries have developed various approximation schemes to study these kinds of systems, concluding that the vast majority of possible three-object arrangements are unstable.

But it turns out that there are a lot of multiple-star systems out there in the galaxy. Indeed, over half of all massive stars belong to at least a binary pair, and many of them belong to triple or quadruple star systems. Obviously, the systems last a long time. Otherwise, they would have flung themselves apart a long time ago before we had a chance to observe them. But because of the limitations of our tools, we have difficulty assessing how these systems organize themselves and what stable orbit options exist.

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Last summer, the gravitational wave observatory known as LIGO caught its second-ever glimpse of two neutron stars merging. The collision of these incredibly dense objects — the hulking cores of long-ago supernova explosions — sent shudders through space-time powerful enough to be detected here on Earth. But unlike the first merger, which conformed to expectations, this latest event has forced astrophysicists to rethink some basic assumptions about what’s lurking out there in the universe. “We have a dilemma,” said Enrico Ramirez-Ruiz of the University of California, Santa Cruz.

The exceptionally high mass of the two-star system was the first indication that this collision was unprecedented. And while the heft of the stars alone wasn’t enough to cause alarm, it hinted at the surprises to come.

In a paper recently posted to the scientific preprint site arxiv.org, Ramirez-Ruiz and his colleagues argue that GW190425, as the two-star system is known, challenges everything we thought we knew about neutron star pairs. This latest observation appears to be fundamentally incompatible with scientists’ current understanding of how these stars form, and how often. As a result, researchers may need to rethink years of accepted knowledge.

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The global collaboration that delivered us not one but two pictures of supermassive black holes has now peered into one of the brightest lights in the Universe.

The Event Horizon Telescope (EHT), a telescope array comprising radio antennae around the world, studied a distant quasar named NRAO 530, whose light has traveled for 7.5 billion years to reach us.

The resulting data show us the quasar’s engine in incredible detail and will, astronomers say, help us understand the complex physics of these incredible objects, and how they generate such blazing light.

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Summary: Researchers explain how deep neural networks are able to learn complex physics.

Source: Rice University.

One of the oldest tools in computational physics — a 200-year-old mathematical technique known as Fourier analysis — can reveal crucial information about how a form of artificial intelligence called a deep neural network learns to perform tasks involving complex physics like climate and turbulence modeling, according to a new study.

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It’s a hot new early dark energy summer.

We’re still not sure exactly what dark energy is, but it may have played a key role in the early universe.

Physicists can’t see or measure dark energy (hence the name). The only clue that it exists is how it affects the rest of the universe; dark energy is the force that’s driving the universe to keep expanding faster. Physicists Florian Niedermann of Stockholm University and Martin Sloth of the University of Southern Denmark propose that if dark energy formed bubbles in the dark plasma of the early universe, it could solve one of the biggest mysteries in modern physics.

They describe their idea in a recent paper in the journal Physics Letters B.

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