Scientists Simulated a Black Hole in The Lab, And Then It Started to Glow

PHYSICS16 November 2022

ByMICHELLE STARR

Simulation of a warped and spinning black hole. (Yukterez/Wikimedia Commons, CC BY-SA 4.0)

A new kind of black hole analog could tell us a thing or two about an elusive radiation theoretically emitted by the real thing.

Using a chain of atoms in single-file to simulate the event horizon of a black hole, a team of physicists has observed the equivalent of what we call Hawking radiation – particles born from disturbances in the quantum fluctuations caused by the black hole's break in spacetime.

This, they say, could help resolve the tension between two currently irreconcilable frameworks for describing the Universe: the general theory of relativity, which describes the behavior of gravity as a continuous field known as spacetime; and quantum mechanics, which describes the behavior of discrete particles using the mathematics of probability.

For a unified theory of quantum gravity that can be applied universally, these two immiscible theories need to find a way to somehow get along.

This is where black holes come into the picture – possibly the weirdest, most extreme objects in the Universe. These massive objects are so incredibly dense that, within a certain distance of the black hole's center of mass, no velocity in the Universe is sufficient for escape. Not even light speed.

That distance, varying depending on the mass of the black hole, is called the event horizon. Once an object crosses its boundary we can only imagine what happens, since nothing returns with vital information on its fate. But in 1974, Stephen Hawking proposed that interruptions to quantum fluctuations caused by the event horizon result in a type of radiation very similar to thermal radiation.

If this Hawking radiation exists, it's way too faint for us to detect yet. It's possible we'll never sift it out of the hissing static of the Universe. But we can probe its properties by creating black hole analogs in laboratory settings.

This has been done before, but now a team led by Lotte Mertens of the University of Amsterdam in the Netherlands has done something new.

A one-dimensional chain of atoms served as a path for electrons to 'hop' from one position to another. By tuning the ease with which this hopping can occur, the physicists could cause certain properties to vanish, effectively creating a kind of event horizon that interfered with the wave-like nature of the electrons.

The effect of this fake event horizon produced a rise in temperature that matched theoretical expectations of an equivalent black hole system, the team said, but only when part of the chain extended beyond the event horizon.

This could mean the entanglement of particles that straddle the event horizon is instrumental in generating Hawking radiation.

The simulated Hawking radiation was only thermal for a certain range of hop amplitudes, and under simulations that began by mimicking a kind of spacetime considered to be 'flat'. This suggests that Hawking radiation may only be thermal within a range of situations, and when there is a change in the warp of space-time due to gravity.

It's unclear what this means for quantum gravity, but the model offers a way to study the emergence of Hawking radiation in an environment that isn't influenced by the wild dynamics of the formation of a black hole. And, because it's so simple, it can be put to work in a wide range of experimental set-ups, the researchers said.

"This, can open a venue for exploring fundamental quantum-mechanical aspects alongside gravity and curved spacetimes in various condensed matter settings," the researchers write.

The research has been published in Physical Review Research.

Prehistoric predator? Artificial intelligence says no

by University of Queensland

An artistic digital rendition of the recently identified dinosaur. Credit: Dr Anthony Romilio

Artificial intelligence has revealed that prehistoric footprints thought to be made by a vicious dinosaur predator were in fact from a timid herbivore.

In an international collaboration, University of Queensland paleontologist Dr. Anthony Romilio used AI pattern recognition to re-analyze footprints from the Dinosaur Stampede National Monument, south-west of Winton in Central Queensland.

"Large dinosaur footprints were first discovered back in the 1970s at a track site called the Dinosaur Stampede National Monument, and for many years they were believed to be left by a predatory dinosaur, like Australovenator, with legs nearly two meters long," said Dr. Romilio.

"The mysterious tracks were thought to be left during the mid-Cretaceous Period, around 93 million years ago.

"But working out what dino species made the footprints exactly—especially from tens of millions of years ago—can be a pretty difficult and confusing business.

"Particularly since these big tracks are surrounded by thousands of tiny dinosaur footprints, leading many to think that this predatory beast could have sparked a stampede of smaller dinosaurs.

"So, to crack the case, we decided to employ an AI program called Deep Convolutional Neural Networks."

It was trained with 1,500 dinosaur footprints, all of which were theropod or ornithopod in origin—the groups of dinosaurs relevant to the Dinosaur Stampede National Monument prints.

The results were clear: the tracks had been made by a herbivorous ornithopod dinosaur.

Dr. Jens Lallensack, lead author from Liverpool John Moores University in the UK, said that the computer assistance was vital, as the team was originally at an impasse.

"We were pretty stuck, so thank god for modern technology," Dr. Lallensack said.

"In our research team of three, one person was pro-meat-eater, one person was undecided, and one was pro-plant-eater.

"So—to really check our science—we decided to go to five experts for clarification, plus use AI.

"The AI was the clear winner, outperforming all of the experts by a wide margin, with a margin of error of around 11 percent.

"When we used the AI on the large tracks from the Dinosaur Stampede National Monument, all but one of these tracks was confidently classified as left by an ornithopod dinosaur—our prehistoric 'predator'."

The team hopes to continue to add to the fossil dinosaur tracks database and conduct further AI investigations.

The research is published in the Journal of The Royal Society Interface and includes collaborations between Australian, German, and UK researchers.

A replica of the dinosaur trackway is on display at the Queensland Museum, Brisbane, and the track site can be visited near south-west of Winton, Queensland.

More information: Jens N. Lallensack et al, A machine learning approach for the discrimination of theropod and ornithischian dinosaur tracks, Journal of The Royal Society Interface (2022). DOI: 10.1098/rsif.2022.0588

Journal information: Journal of the Royal Society Interface

Provided by University of Queensland 

'Dino Cave' reveals dinosaur crouch walkers

 

Hubble Views a Billowing Cosmic Cloud

A small, dense cloud of gas and dust called CB 130-3 blots out the center of this image from the NASA/ESA Hubble Space Telescope. CB 130-3 is an object known as a dense core, a compact agglomeration of gas and dust. This particular dense core is in the constellation Serpens and seems to billow across a field of background stars.

Dense cores like CB 130-3 are the birthplaces of stars and are of particular interest to astronomers. During the collapse of these cores enough mass can accumulate in one place to reach the temperatures and densities required to ignite hydrogen fusion, marking the birth of a new star. While it may not be obvious from this image, a compact object teetering on the brink of becoming a star is embedded deep within CB 130-3.

Astronomers used Hubble’s Wide Field Camera 3 to better understand the environment surrounding this fledgling star. As this image shows, the density of CB 130-3 isn’t constant; the outer edges of the cloud consist of only tenuous wisps, whereas at its core CB 130-3 blots out background light entirely. The gas and dust making up CB 130-3 affect not only the brightness but also the apparent color of background stars, with stars toward the cloud’s center appearing redder than their counterparts at the outskirts of this image. Astronomers used Hubble to measure this reddening effect and chart out the density of CB 130-3, providing insights into the inner structure of this stellar nursery.

Text credit: European Space Agency (ESA)
Image credit: ESA/Hubble, NASA & STScI, C. Britt, T. Huard, A. Pagan

Media Contact:

Claire Andreoli
NASA's Goddard Space Flight Center, Greenbelt, MD
301-286-1940

Last Updated: Nov 18, 2022

Editor: Andrea Gianopoulos

Powerful impact provides insight into deep structure of Mars

by Rachel Fritts, American Geophysical Union

This cross-sectional illustration shows the farside meteorite impact observed by the Mars Reconnaissance Orbiter and the resultant propagation paths, through the mantle and along the core-mantle boundary, of seismic waves detected by the InSight seismic station. Credit: Institut de Physique du Globe de Paris/Centre National D’Études Spatiales/N. Starter

NASA's InSight lander (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) launched in 2018 with the goal of peering deep into Mars's interior for the first time to gain important information about the planet's structure and formation. To help with this task, the lander is equipped with a sensitive seismometer that allows it to detect subtle marsquake vibrations.

By recording the way these vibrations are reflected and bent as they travel through the planet, InSight has helped scientists map the layout of Mars's crust, mantle, and core. Recently, an unusual series of vibrations provided an opportunity for even deeper understanding.

In a new paper published in Geophysical Research Letters, Durán et al describe one of the largest seismic events recorded on Mars, and the farthest from InSight's location. It is the first such event with pressure waves (P waves) that reached into the lower mantle more than 800 kilometers beneath the planet's surface and all the way to the core, where they were diffracted.

After analyzing the vibrations, the authors concluded that the event, which turned out to be an impact, occurred near Mars's Tharsis volcanic plateau, on the opposite side of the planet from InSight, in agreement with satellite images showing the impact site.

The depth of the detected vibrations allowed the researchers to constrain the structure of Mars's lower mantle in more detail than has previously been available. They found that the lower mantle appears to be more variable, in terms of both its temperature and composition, than suggested by previous seismic models. However, they say, it will require more data to determine precisely how the thermal and chemical makeup of the lower mantle varies, and why.

More information: C. Durán et al, Observation of a Core‐Diffracted P‐Wave From a Farside Impact With Implications for the Lower‐Mantle Structure of Mars, Geophysical Research Letters (2022). DOI: 10.1029/2022GL100887

Journal information: Geophysical Research Letters 

Provided by American Geophysical Union

This story is republished courtesy of Eos, hosted by the American Geophysical Union. Read the original story here.

 

The Mysterious Origins of The Great Barrier Reef May Finally Be Explained

NATURE15 November 2022

ByCARLY CASSELLA

(zstockphotos/Getty Images)

Australia's Great Barrier Reef might never have come to be were it not for the formation of a vast island based mostly on sand.

K'gari, also known as Fraser Island, has the honor of being the world's largest sand island, covering around 640 square miles (nearly 1,700 square kilometers) just off the southeastern coast of Queensland.

Along with the nearby Cooloola Sand Mass, the mass of forested dunes and beaches forms an unofficial base to the vast reef that sits to its north.

If this terrestrial 'launching pad' had never formed, researchers think the masses of sand carried northwards along the coast by ocean currents would have landed right where the reef now sits.

Quartz-rich sands have a way of smothering carbonate-rich sediments, which are necessary for coral development.

Without K'gari in the way to guide sediment off the continental shelf and into the deep, conditions would not have suited the formation of the world's largest coral reef, experts argue.

The Great Barrier Reef has a confusing origin story. It only formed half a million years ago, long after conditions were appropriate for the growth of coral.

K'gari might be the lost puzzle piece researchers have been searching for. Analysis and dating of sand from the many dunes on the 123 kilometer (76 mile) long island suggest the land mass formed between 1.2 and 0.7 million years ago, just a few hundred thousand years before the Great Barrier Reef came to be.

The island's presence probably deflected northward currents, researchers explain, providing the southern and central parts of the great barrier reef the reprieve they needed to start growing thousands of kilometers of coral.

The coast of Queensland, Australia, showing sediment dispersal before the formation of K'gari and Cooloola (left) and after (right). (Ellerton et al., Nature Geoscience, 2022)

K'gari and Cooloola themselves arose from the accumulation of sand and sediment from the south.

Amid periods of ice formation and fluctuating sea levels, researchers suspect sediment around the world 'suddenly' became exposed. In successive periods of ice melt and rising oceans, that sediment then got caught up in the currents.

Along the east coast of Australia this probably meant a long northward treadmill of soil and sand tracing the continental shelf.

A slope off the southern coast of Queensland, however, makes the perfect place for sediment to accumulate, and this is right where K'gari and Cooloola are found.

Just south of the sand masses, coral reefs are conspicuously missing.

If researchers are right, that's probably because the northward currents here are too strong. K'gari and Cooloola break up the long distance dispersal, stopping quartz-rich sands from smothering developing reefs.

"Before Fraser Island developed, northward longshore transport would have interfered with coral reef development in the southern and central [Great Barrier Reef]," researchers write.

Sediment records from the southern Great Barrier Reef support this idea. About 700,000 years ago, there appears to have been an uptick in carbonate content in sediment in this region.

Research on reefs further north is now needed as well, but at least two-thirds of the Great Barrier Reef seems to owe its existence to a wall of sand to the south.

"The development of Fraser Island dramatically reduced sediment supply to the continental shelf north of the island," the authors argue.

"This facilitated widespread coral reef formation in the southern and central Great Barrier Reef and was a necessary precondition for its development."

The study was published in Nature Geoscience.