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Category: physics – Page 31

Observations of the cosmic microwave background, leftover light from when the Universe was only 380,000 years old, reveal that our cosmos is not rotating. Infinitely long cylinders don’t exist. The interiors of black holes throw up singularities, telling us that the math of GR is breaking down and can’t be trusted. And wormholes? They’re frighteningly unstable. A single photon passing down the throat of a wormhole will cause it to collapse faster than the speed of light. Attempts to stabilize wormholes require exotic matter (as in, matter with negative mass, which isn’t a thing), and so their existence is just as debatable as time travel itself.

This is the point where physicists get antsy. General relativity is telling us exactly where time travel into the past can be allowed. But every single example runs into other issues that have nothing to do with the math of GR. There is no consistency, no coherence among all these smackdowns. It’s just one random rule over here, and another random fact over there, none of them related to either GR or each other.

If the inability to time travel were a fundamental part of our Universe, you’d expect equally fundamental physics behind that rule. Yet every time we discover a CTC in general relativity, we find some reason it’s im possible (or at the very least, implausible), and the reason seems ad hoc. There isn’t anything tying together any of the “no time travel for you” explanations.

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Astronomers have made a groundbreaking discovery of binary star systems, consisting of a white dwarf and a main sequence star, within young star clusters.

This discovery opens up new avenues for understanding stellar evolution and could provide insights into the origins of phenomena such as supernovas and gravitational waves.

Breakthrough Discovery in Star Clusters.

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Good news for anyone with a hankerin’ for going back in time to kill their grandfather before he had kids: a physicist named Germain Tobar from the University of Queensland in Australia says go for it since time travel paradoxes aren’t real. So feel free to kill your grandpappy without fear of deleting your own existence.

He didn’t explicitly frame it that way, but he does think that time travel paradoxes are bullshit. Tobar’s work uses Einstein’s theory of general relativity as a foundation and then builds from there. He says that, according to his calculations, events can exist both in the past and in the future simultaneously, independent of one another. Space-time will adjust itself to avoid paradoxes, thus allowing you to cause whatever mayhem you want throughout time without creating contradictions.

If true, famous time travel stories like The Terminator and Back to the Future wouldn’t be possible. A Terminator sent to the past to kill John Connor would not be killing John Connor in the future, theoretically. It would only kill John Connor in the past and space-time would find some way to adjust to ensure that John Connor is still alive in the future to continue to be a pain in every robot’s shiny metal ass.

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A new method enables researchers to analyze magnetic nanostructures with a high resolution. It was developed by researchers at Martin Luther University Halle-Wittenberg (MLU) and the Max Planck Institute of Microstructure Physics in Halle.

The new method achieves a resolution of around 70 nanometers, whereas normal light microscopes have a resolution of just 500 nanometers. This result is important for the development of new, energy-efficient storage technologies based on spin electronics. The team reports on its research in the current issue of the journal ACS Nano.

Normal optical microscopes are limited by the wavelength of light and details below around 500 nanometers cannot be resolved. The new method overcomes this limit by utilizing the anomalous Nernst effect (ANE) and a metallic nano-scale tip. ANE generates an electrical voltage in a magnetic metal that is perpendicular to the magnetization and a .

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For decades, scientists have used the Milky Way as a model for understanding how galaxies form. But three new studies raise questions about whether the Milky Way is truly representative of other galaxies in the universe.

“The Milky Way has been an incredible physics laboratory, including for the physics of galaxy formation and the physics of dark matter,” said Risa Wechsler, the Humanities and Sciences Professor and professor of physics in the School of Humanities and Sciences. “But the Milky Way is only one system and may not be typical of how other galaxies formed. That’s why it’s critical to find similar galaxies and compare them.”

To achieve that goal, Wechsler cofounded the Satellites Around Galactic Analogs (SAGA) Survey dedicated to comparing galaxies similar in mass to the Milky Way.

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New research into dark matter suggests it might have originated from a “Dark Big Bang,” distinct from the traditional Big Bang.

This theory, which posits a separate cosmic event as the source of dark matter, could change how we understand the universe’s early moments. Upcoming gravitational wave detection experiments could provide critical evidence to support this theory.

Alternative theory of dark matter genesis.

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Gravity has shaped our cosmos. Its attractive influence turned tiny differences in the amount of matter present in the early universe into the sprawling strands of galaxies we see today. A new study using data from the Dark Energy Spectroscopic Instrument (DESI) has traced how this cosmic structure grew over the past 11 billion years, providing the most precise test to date of gravity at very large scales.

DESI is an international collaboration of more than 900 researchers from over 70 institutions around the world and is managed by the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab).

In their new study, DESI researchers found that gravity behaves as predicted by Einstein’s theory of general relativity. The result validates the leading model of the universe and limits possible theories of modified gravity, which have been proposed as alternative ways to explain unexpected observations—including the accelerating expansion of our universe that is typically attributed to dark energy.

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MIT physicists have taken a key step toward solving the puzzle of what leads electrons to split into fractions of themselves. Their solution sheds light on the conditions that give rise to exotic electronic states in graphene and other two-dimensional systems.

The new work is an effort to make sense of a discovery that was reported earlier this year by a different group of physicists at MIT, led by Assistant Professor Long Ju. Ju’s team found that appear to exhibit “fractional charge” in pentalayer graphene—a configuration of five that are stacked atop a similarly structured sheet of boron nitride.

Ju discovered that when he sent an electric current through the pentalayer structure, the electrons seemed to pass through as fractions of their total charge, even in the absence of a magnetic field.

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Astronomers at the University of Toronto (U of T) have discovered the first pairs of white dwarf and main sequence stars—” dead” remnants and “living” stars—in young star clusters. Described in a new study published in The Astrophysical Journal, this breakthrough offers new insights into an extreme phase of stellar evolution, and one of the biggest mysteries in astrophysics.

Scientists can now begin to bridge the gap between the earliest and final stages of binary star systems—two stars that orbit a shared center of gravity—to further our understanding of how stars form, how galaxies evolve, and how most elements on the periodic table were created. This discovery could also help explain cosmic events like supernova explosions and gravitational waves, since binaries containing one or more of these compact dead stars are thought to be the origin of such phenomena.

Most stars exist in binary systems. In fact, nearly half of all stars similar to our sun have at least one companion star. These paired stars usually differ in size, with one star often being more massive than the other. Though one might be tempted to assume that these stars evolve at the same rate, more massive stars tend to live shorter lives and go through the stages of stellar evolution much faster than their lower mass companions.

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