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Category: cosmology – Page 273

Physicists measure gravitational time warp to within one millimeter

The flow of time isn’t as consistent as we might think – gravity slows it down, so clocks on the surface of Earth tick slower than those in space. Now researchers have measured time passing at different speeds across just one millimeter, the smallest distance yet.

The idea that time would be affected by gravity was first proposed by Albert Einstein in 1915, as part of his theory of general relativity. Space and time are inextricably linked, and large masses warp the fabric of spacetime with their immense gravitational influence. This has the effect of making time pass more slowly closer to a large mass like a planet, star, or, in the most extreme example, a black hole. This phenomenon is known as time dilation.

Here on Earth, time dilation effectively means that time moves more quickly at higher elevations. So for instance, time passes faster on the summit of Mount Everest than at sea level, but it applies over smaller distances too – someone living in a 10th floor apartment will age faster than someone on the first floor, and your head ages faster than your feet.

Examining the results of new dark matter searches by the PandaX-4T and ADMX collaborations

Physicists have predicted the existence of dark matter, a material that does not absorb, emit or reflect light, for decades. While there is now significant evidence hinting to the existence of dark matter in the universe, as it was never directed detected before its composition remains unknown.

In recent years, researchers worldwide have made different hypotheses about the composition of this elusive material and tried to test them experimentally. Many have suggested that it could be comprised of new and previously unobserved types of elementary particles, such as axions and weakly interactive massive particles (WIMPs).

A few weeks ago, two large research collaborations, the PandaX-4T and the ADMX Collaborations, published the results of two new dark matter searches based on different hypothesis. In their study, featured in Physical Review Letters, the PandaX-4T Collaboration tried searching for signs of a new elementary particle in data collected using a time projection chamber at the China Jinping Underground Laboratory (CJPL), the deepest underground lab in world.

Physicists may finally learn what’s inside a black hole

A light in the dark — If quantum computers continue to advance, and perform more calculations for less steep costs, Rinaldi and his team might be able to reveal what happens inside of black holes, beyond the event horizon — a region immediately surrounding a black hole’s singularity, within which not even light, nor perhaps time itself, can escape the immense force of gravity.

In practical terms, the event horizon prevents all conventional, light-based observations. But, and perhaps more compelling, the team hopes that further advances in this line of inquiry will do more than peek inside a black hole, and unlock what physicists have dreamed of since the days of Einstein: a unified theory of physics.

Breaking Cosmology: Too Many Disk Galaxies — “A Significant Discrepancy Between Prediction and Reality”

A study by the University of Bonn: Observations fit poorly with the Standard Model of Cosmology.

The Standard Model of Cosmology describes how the universe came into being according to the view of most physicists. Researchers at the University of Bonn have now studied the evolution of galaxies within this model, finding considerable discrepancies with actual observations. The University of St. Andrews in Scotland and Charles University in the Czech Republic were also involved in the study. The results have now been published in the Astrophysical Journal.

Most galaxies visible from Earth resemble a flat disk with a thickened center. They are therefore similar to the sports equipment of a discus thrower. According to the Standard Model of Cosmology, however, such disks should form rather rarely. This is because in the model, every galaxy is surrounded by a halo of dark matter. This halo is invisible, but exerts a strong gravitational pull on nearby galaxies due to its mass. “That’s why we keep seeing galaxies merging with each other in the model universe,” explains Prof. Dr. Pavel Kroupa of the Helmholtz Institute for Radiation and Nuclear Physics at the University of Bonn.

Scientists may have just found an invisible black hole — should you be worried?

It’s hard to spot a black hole.

There are two different approaches to such detection. In “X-ray binary stars” — in which a star and a black hole orbit a shared center while producing X-rays — a black hole’s gravitational field can pull material from its companion. The material circles the black hole, heating up by friction as it does so.

The hot material glows brightly in X-ray light, making the black hole visible, before being sucked into the black hole and disappearing. You can also detect pairs of black holes as they merge together, spiraling inwards and emitting a brief flash of gravitational waves, which are ripples in spacetime.

There are many rogue black holes that are drifting through space without interacting with anything, however — making them hard to detect. That’s a problem, because if we can’t detect isolated black holes, then we can’t learn about how they formed and about the deaths of the stars they came from.