As they approach a black hole’s event horizon, particles of accreting gas can take on opposing orbital trajectories – remarkably similar to the paths produced in manmade particle colliders. Using advanced new models, Andrew Mummery at the University of Oxford, together with Joseph Silk at Sorbonne University, showed how such particles could collide at colossal energies, with detectable collision products that could offer valuable new insights for particle physics.

Within a black hole’s accretion disk, gas particles travel in circular orbits that gradually shrink under its immense gravity. Once an orbit contracts beneath a critical radius, it becomes unstable, and the particles it carries will suddenly plunge toward the black hole.

“Long ago, Roger Penrose showed that these particles could extract energy from the spin of massive black holes in the region where they decay,” Silk explains. “This happens in the ergosphere – the region just outside the event horizon where debris can gain energy from the black hole’s intense gravitational and rotational fields.”

In the theory described by Penrose, a particle approaching a black hole splits into two fragments – possibly through a collision or spontaneous decay. After the split, one fragment falls into the event horizon, while the other gains enough energy from the black hole’s spin to escape its gravity – exiting the ergosphere with more energy than the original particle.

Building on this idea, Silk and two of his previous collaborators – Maximo Bañados and Stephen West – proposed an alternative escape mechanism. Their idea involves gas particles in retrograde orbits (moving opposite to the black hole’s spin) within the accretion disk. Since a retrograde orbit becomes unstable at larger radii than a prograde orbit (movement in the same direction as the black hole’s rotation), these particles fall farther before reaching the ergosphere, allowing them to gain more energy through gravitational acceleration.

Within the ergosphere, Bañados, Silk and West considered how these now highly energetic particles could collide with those originating from prograde orbits, travelling in opposite directions. If this occurred, the relative velocity between the two would be enormous – imparting extreme relativistic energies to their collision products. The trio proposed that some of these products could escape the ergosphere with more energy than either of the original particles.

In their latest study, reported in Physical Review Letters, Silk and Mummery explored this possibility in greater detail. They used models recently developed by Mummery to simulate the flow of particles accreting onto rapidly spinning supermassive black holes.

“We showed that the infalling gas would develop a pattern of turbulent rotating and counter-rotating vortices as it plunged into the black hole’s ergosphere,” Silk explains. The rotation direction of each vortex depends on whether the particles originated from prograde or retrograde orbits within the accretion disk.

When particles travelling in opposite directions collide in the ergosphere, their circular paths resemble the magnetically guided trajectories of protons and heavy ions in manmade particle colliders, such as CERN’s Large Hadron Collider – only on a vastly larger scale. “We found that the collisions occurred at hundreds of times higher energies than those reached in any existing collider, and would approach or even exceed the energies expected for the proposed Future Circular Collider,” Silk notes.

At such colossal energies, Mummery and Silk predict that the collision products could include gamma rays and ultrahigh-energy neutrinos, which might be detectable from nearby supermassive black holes – such as Sagittarius A* at the centre of our own galaxy. As a result, the process could offer an entirely new approach to observations in particle physics.

“Our predicted signatures would complement those of the next generation of giant particle supercolliders planned by CERN and in China, helping to provide evidence of new particle physics beyond the Standard Model,” says Silk. In particular, the duo suggest that these signatures could lead to a highly sensitive probe of dark matter – potentially offering more robust tests for candidates such as weakly interacting massive particles.

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The Norwegian-born condensed-matter physicist Ivar Giaever, who shared the Nobel Prize for Physics in 1973, died on 20 June at the age of 96. In the late 1950s, Giaever made pioneering progress in the electron tunnelling in superconductors as well as provided a crucial verification of the Bardeen–Cooper–Schrieffer (BCS) theory of superconductivity.

Born in Bergen, Norway, on 5 April 1929, Giaever graduated with a degree in mechanical engineering in 1952 from the Norwegian Institute of Technology. Following a year of military service he worked as a patent examiner for the Norwegian government before moving to Canada in 1954 where he began working at General Electric.

Two years later he moved to GE’s research laboratory in New York, where he continued to study the company’s engineering courses. In 1958 he joined the GE’s R&D centre as a researcher.

At the same time, Giaever began to study physics at Rensselaer Polytechnic Institute in New York where he obtained a PhD in 1964 working in tunnelling and superconductivity. That year he also became a naturalized US citizen.

A Nobel life

It was work in the early 1960s that led to his Nobel prize. Following the Japanese physicist Leo Esaki’s discovery of electron tunnelling in semiconductors in 1958, Giaever showed that tunnelling also happened in superconductors, in this case a thin later of oxide surrounded by a metal in a superconducting state.

Using his tunnelling apparatus, Giaever also measured the energy gap near the Fermi level when a metal becomes superconducting, providing crucial verification of the BCS theory of superconductivity.

At the age of 44, Giaever shared half the 1973 Nobel Prize for Physics with Esaki “for their experimental discoveries regarding tunnelling phenomena in semiconductors and superconductors, respectively”. The other half went to Brian Josephson “for his theoretical predictions of the properties of a supercurrent through a tunnel barrier, in particular those phenomena which are generally known as the Josephson effects”.

In 1988 Giaever left General Electric and moved to Rensselaer where he continued to work in biophysics. In 1993, he founded the New York-based Applied BioPhysics Inc.

As well as the Nobel prize, Giaever also won the Oliver E Buckley Prize by the American Physical Society (APS) in 1965 as well as the Golden Plate Award by the American Academy of Achievement in 1966.

Gaiever’s career was not withouth controversy. In 2011 he resigned from the APS in protest after the organisation called the evidence of damaging global warming “incontrovertible”.

In 2016 he published his autobiography I am the Smartest Man I Know, in which he details his journey from relatively humble beginnings in Norway to a Nobel prize and beyond.

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Every mystical quest features a journey riddled with challenges, a cast of colourful characters, and a treasure trove that unlocks more intrigue. The Meteorite Hunters: On the Trail of Extraterrestrial Treasures and the Secrets Inside Them is no exception to this canon.

Written by science journalist Joshua Howgego, the book takes the reader on the pursuit of space rocks and how they have unravelled our understanding of the solar system. And, as is so often the way in science as it is with quests, the search and the people you meet along the way are just as interesting as the discoveries themselves.

Towards the end of Meteorite Hunters, Howgego confides that his aim for the book distils down to two questions: “how do you find them, and what do they tell us?”. Indeed, the tale follows this two-act structure pretty neatly. The first half sees the eponymous hunters and their adventures take centre stage, with enough science dotted throughout to set the scene for the second half, which takes us right up to date with the very latest missions to asteroids Itokawa and Ryugu, and the return of the Bennu sample from the OSIRIS-Rex mission. It is a tactic that is kind to the general reader, and there are plenty of interesting anecdotes and characters to keep things from getting too dry, along with some truly astonishing astrophysics.

The journey begins with a look at how people came to understand that rocks can fall from the sky. The truth of course is that civilizations throughout human history have (separately but repeatedly) come to this realization. Howgego highlights how existing knowledge and compelling physical evidence of meteorites from central South American cultures was dismissed as primitive superstitious nonsense by European invaders in the 16th century. It is the perennial story of knowledge being lost during the waves of European colonialism.

Western understanding of meteorites only really gets going in the very late 18th century, and Howgego introduces two key characters who helped cement the topic as a legitimate line of enquiry. Ernst Chladni was a German polymath who wrote the first book on meteorites in 1794 but whose ideas were initially ridiculed. Meanwhile, playwright and journalist Edward Topham had a large meteorite fall on his land in 1795 (witnessed by labourer John Shipley) and went on to the champion the idea of rocks falling from the sky. However, it would take until the mid-1960s, and the anticipation of lunar samples being returned by the Apollo missions, for this area of study to crystallize into the modern field of meteoritics.

Drama and dust

The origin story of many modern meteorite hunters – those who go out searching for these space rocks – often begin in a similar vein to that of Topham, with an inspiring find close to home leading to elaborate expeditions to track down historic falls. The meteorite scientists Howgego interviews are diplomatic when asked about the hunters – after all, they have the resources to investigate reports of fresh falls much more quickly than the hunters can decipher historical reports and local legends. But there is also a real tension between the two camps – there are serious issues with permanent loss of data from the scientific record through mishandling or denial of access to specimens in private collections.

Howgego goes on to discuss efforts to track meteorite falls in real-time, which may be more scientific and systematic but are no less dramatic. Modern programmes involving networks of automated digital cameras can trace their origins back to a resourceful young scientist, Zdeněk Ceplecha, who narrowly escaped the worst of the Stalinist purges in soviet Czechoslovakia. In 1959 he managed to reconstruct the trajectory of an incoming meteorite to within a very respectable margin of modern computations by using long-exposure photographic plates. In a beautiful full-circle moment, the tracking network initiated by Ceplecha followed a 2002 meteorite fall that turned out to have the exact same trajectory as that 1959 space rock – confirming that the two came from the same parent body.

One of the book’s more modern – and most interesting – characters is Swedish jazz guitarist Jon Larsen. His obsession of sifting through tonnes of urban dust for elusive micrometeorites has yielded invaluable (and beautifully photographed) specimens – something dismissed as an urban myth before someone with his patience and ingenuity came along. These pristine remnants of the protoplanetary disc, literal “star dust”, offer unique insights into the earliest days of our solar system.

Alongside his array of characters, Howgego creates a beautiful and accessible rendering of the complex astrophysics underlying the evolution and structure of our solar system as revealed from the study of meteorites. The descriptions of how competing theories have developed and merged also gives a realistic insight into the scientific method in action; consensus building, refinement through accretion of evidence, and an admission that the picture is not yet settled.

The hunt for, and study of, meteorites touches upon an unexpected variety of topics in modern science. But Howgego manages to weave them seamlessly together into a rich fabric, allowing his colourful cast of characters to tell their fascinating stories.

• 2025 Oneworld Publications 272pp £18.99 hb / £9.99 ebook

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In an unprecedented move, President Donald Trump announced late July 9 that he has named Transportation Sec. Sean Duffy as interim NASA administrator.

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New discovery confirms the long-debated hypothesis that the ancient winged reptiles ate plants

Scientists sequence 20-million-year-old enamel protein from teeth fossils preserved in Arctic cold

Japan’s Space BD has signed an agreement with Australian launch vehicle developer Gilmour Space ahead of that company’s first orbital launch attempt.

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Spaceport advocates won a tax break in the budget reconciliation bill that they hope will spur investment, but the provision has also generated a political backlash.

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Learn about the Moon-Rice project, which aims to create rice crops that can grow in space and help keep astronauts healthy.

Learn about a cosmic project that will journey to the dark side of the moon in order to listen for the Universe’s earliest echoes.

Learn how the benefits of GLP-1s may be outweighed by the risks.

India’s space regulator has approved services from Starlink, although SpaceX’s low Earth orbit network still needs spectrum and other clearances before it can provide broadband in the world’s most populous nation.

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Paul “Rusty” Thomas was tapped as chief executive of EnduroSat USA, as the company scales up operations.

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Is Earth's inner core solid or liquid? While the inner core is extremely hot, experts have known that it is solid for many years.

No one has to be reminded that we’re living at a dangerous time, and across Europe, leaders are scrambling to find the money to strengthen the bloc’s defenses. The continent’s defense startups are increasingly playing their part. But it sometimes seems as if we’re unwilling to let them. All across Europe, highly innovative companies building […]

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The SJ-21 and SJ-25 satellites “merged” on July 2 and have remained together since then.

A giant gas planet comparable in size to Saturn exists around a small red dwarf star. The discovery is beyond the scope of conventional astronomy theory, and is making experts reconsider conventional notions of planet formation.

When Canadian and European Space Agency leaders reaffirmed their commitment to work together in June, leaders focused their public remarks primarily on shared exploration goals and decades of fruitful partnership. “Canada and the European Space Agency are working on a number of projects all the way from exploration to Earth observation, communication, navigation and many […]

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Synspective, a Japanese company developing a radar imaging constellation, has signed an agreement with Exolaunch to launch 10 of the company’s satellites.

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New experiments show elephants use a wide range of movements to express their desires

A new evolutionary analysis of butterflies finds “false heads” arose from the coalescence of multiple traits

Scientists, ethicists, and officials worry the OpenAI-sponsored contest sidesteps archaeological norms

Partisan fight over Trump cuts heats up as Congress works on 2026 spending bills.

Despite a successful test flight of a reusable launch vehicle prototype last month, Honda has yet to decide whether to pursue development of an operational vehicle.

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