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Category: physics – Page 17

The DESI collaboration’s latest research supports the standard model of gravity and hints at evolving dark energy, based on a detailed analysis of data from millions of galaxies and quasars. These results contribute significantly to understanding the accelerated expansion of the universe.

A physicist from the University of Texas at Dallas, alongside an international team of researchers in the Dark Energy Spectroscopic Instrument (DESI) collaboration, is conducting a multiyear mission to tackle one of astrophysics’ biggest mysteries: Why is the universe’s expansion accelerating?

Scientists have proposed competing theories to explain this phenomenon. One theory suggests that dark energy, an unknown force, is driving galaxies apart. Another theory posits that gravity—the force that binds objects together in local systems like our solar system—behaves differently on vast cosmic scales and may need to be revised to account for the accelerating expansion.

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As physicists continue their struggle to find and explain the origin of dark matter, the approximately 80% of the matter in the universe that we can’t see and so far haven’t been able to detect, researchers have now proposed a model where it is produced before the Big Bang.

Their idea is that dark matter would be produced during a infinitesimally short inflationary phase when the size of the universe quickly expanded exponentially. The new model was published in Physical Review Letters by three scientists from Texas in the US.

An intriguing idea among cosmologists is that dark matter was produced through its interaction with a thermal bath of some species, and its abundance is created by “freeze-out” or “freeze-in.” In the freeze-out scenario, dark matter is in chemical equilibrium with the bath at the earliest times—the concentration of each does not change with time.

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Was dark matter created some time after the Big Bang? Gravitational wave detectors could soon find the answer.

For now, the duo’s results suggest that the Dark Big Bang is far less constrained by past observations than Freese and Winkler originally anticipated. As Ilie explains, their constraints could soon be put to the test.

“We examined two Dark Big Bang scenarios in this newly found parameter space that produce gravitational wave signals in the sensitivity ranges of existing and upcoming surveys,” he says. “In combination with those considered in Freese and Winkler’s paper, these cases could form a benchmark for gravitational wave researchers as they search for evidence of a Dark Big Bang in the early universe.”

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Is the universe really infinite? Or could it close back on itself like a sphere? If it’s infinite, how can it expand? And is it true that there might be copies of you in it? Today I want to explain how much we know about those questions and what the expansion of space has to do with Hilbert’s Hotel.

This video comes with a quiz which you can take here: https://quizwithit.com/start_thequiz/.…

The Kurzgesagt video is here: • The Paradox of an Infinite Universe.

Continue reading “Is the Universe Infinite or Finite?” | >

The fabric of space and time is not exempt from the effects of gravity. Plop in a mass and space-time curves around it, not dissimilar to what happens when you put a bowling ball on a trampoline.

This dimple in space-time is the result of what we call a gravity well, and it was first described over 100 years ago by Albert Einstein’s field equations in his theory of general relativity. To this day, those equations have held up. We’d love to know what Einstein was putting in his soup. Whatever it was, general relativity has remained pretty solid.

One of the ways we know this is because when light travels along that curved space-time, it curves along with it. This results in light that reaches us all warped and stretched and replicated and magnified, a phenomenon known as gravitational lensing. This quirk of space-time is not only observable and measurable, it’s an excellent tool for understanding the Universe.

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Scientists have a problem with cosmic rays—they produce too many muons at the Earth’s surface. Cascades of muons are byproducts of high-energy cosmic rays as they collide with nuclei in the upper atmosphere, and scientists see more muons at Earth’s surface than standard physics models predict.

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Why have 700 stars vanished how is it possible?

Of all the objects in the universe, stars are amongst the most fascinating. From the birth of newborn protostars to the dramatic final stages of their lives, the life cycle of stars has captivated the human imagination for centuries. Yet one of the greatest stellar mysteries is that of vanishing stars — stars that were once visible but have suddenly disappeared. While the mysteries behind them haven’t been completely unraveled, recent advances in telescope and monitoring technology have unveiled shocking truths about this extremely rare occurrence. Join us as we explore the concept of vanishing stars and unravel the mystery behind the disappearance of 700 known stars.
When we look up at the night sky, the stars appear eternal. In a sense, that’s true, as stars can live for millions or even billions of years, which is just mind-boggling compared to our own lifespans. However, like all living things, stars are born, they live, and they eventually die. Astrophysicists have made significant progress in understanding the life cycles of stars. However, when a star suddenly disappears, it raises more questions than answers. What could have caused it to vanish? Was it a natural event or something more unusual? The discovery that as many as a hundred stars may have disappeared from our observations in recent decades is a sobering reminder that our understanding of the universe is still incomplete. The vanishing stars challenge our assumptions and force us to confront the limitations of our knowledge. Keep watching as we explore some of the most groundbreaking discoveries in our understanding of vanishing stars and provide possible explanations to the stars that has vanished from our solar system and beyond in the last few decades.
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Distortions in pulsar signals reveal flaws in galactic models, pointing to new opportunities for understanding the universe and studying cosmic waves.

By analyzing patterns in pulsar signals, researchers discovered discrepancies in existing models of how the galaxy impacts pulsar signals, suggesting that these models need updates. The findings not only deepen our understanding of the universe but also improve our ability to study phenomena like gravitational waves.

Dr. Sofia Sheikh from the SETI Institute led a groundbreaking study that explores how pulsar signals—emissions from the spinning remnants of massive stars—become distorted as they travel through space. Published on November 26 in The Astrophysical Journal, this research was conducted by a group of undergraduate students from the Penn State branch of the Pulsar Search Collaboratory, a student club dedicated to pulsar science.

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Trying to understand the makeup and evolution of the solar system’s Kuiper belt has kept researchers busy since it was hypothesized soon after the discovery of Pluto in 1930. In particular, binary pairs of objects there are useful as indicators since their existence today paints a picture of how energetic or violent the evolution of the solar system was in its early days four billion years ago.

Looking closely at the evolution of an ultrawide (in separation) binary object, researchers included more physics that reveals much about their architecture and unfolding. They found that these ultrawide binaries may not have been formed in the primordial solar system as has been thought. Their work has been published in Nature Astronomy.

“In the outer reaches of the solar system, there exists a population of binary systems so widely separated that it seemed worth looking into whether or not they could even survive 4 billion years without being [completely] separated somehow,” said Hunter M. Campbell of the University of Oklahoma in the US.

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