In a lab in Illinois, physicists captured and tamed a tiny particle of antimatter in a trap with invisible walls. By studying how the positron behaved, the researchers may soon have a chance to break our best mathematical model of physical reality.

The positron is the antimatter counterpart of the electron, which means the two particles have the same mass but the opposite electric charge. Unlike electrons, however, positrons are rare and typically exist for a tiny fraction of a second because the moment one meets one of the super-abundant electrons in our universe, the pair annihilate. This makes positrons difficult to study.

at Northwestern University in Illinois and his colleagues have now found a way to trap a positron and keep it around for months on end. By analysing data collected while the positron was trapped, they plan to precisely measure the antiparticle’s properties and consequently investigate one of the biggest problems with the standard model of particle physics.

The researchers obtained the positron from a radioactive isotope of sodium that emits one whenever it decays. Such positrons are very fast and hard to control, so they placed the sodium into a special refrigerator to lower its temperature and energy, and slow down the antiparticles.

They slowed them further by directing the positrons through a tungsten crystal. While some positrons were annihilated as they travelled through the crystal, some came through unscathed. They were then directed into a refrigerated chamber that was empty of all other particles. Here, electronic components generated electromagnetic fields that confined a single incoming positron, serving as invisible walls that trapped the particle.

The researchers then pushed the positron into its lowest possible energy state, which Gabrielse says allowed them to keep the otherwise elusive antiparticle trapped for months. They could also push it into the next lowest energy state with controlled bursts of microwaves.

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“It’s a real kick to stand in my lab and watch a positron making transitions – ‘quantum jumps’ we call them – between its lowest energy states. How much more fundamental, how much neater can it get?” he says.

“Trapping an antiparticle is extremely difficult,” says at Japanese scientific institute RIKEN, particularly since any stray particle, burst of light or tiny vibration could disturb it and the trap had to be kept just tenths of a degree above the coldest temperature possible.

The payoff for trapping and controlling the positron despite these experimental challenges could be remarkable. “This has the potential to become one of the most precise measurements of a fundamental constant in physics,” says Ulmer.

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Specifically, Gabrielse and his colleagues want to measure the positron’s magnetic moment, which is a number that quantifies its response to magnetic fields. The researchers have previously made the most precise ever measurement of the electron’s magnetic moment, and comparing this figure with the one for the antiparticle would enable them to compare the properties of matter and antimatter with unprecedented precision.

The standard model predicts they should have identical magnetic moments, but this prediction underscores a notable shortcoming of this theory. The problem is that if matter and antimatter are so alike, then they should have been created in equal amounts and fully annihilated as the universe began, leaving nothing. “The standard model seems to be inconsistent, or at least significantly incomplete, with basic features of the universe, like why we have a universe at all,” says Gabrielse.

Uncovering a difference between the electron and positron could hint at some currently unknown mechanism that resulted in our matter-filled universe. If all goes according to plan, the researchers aim to have data that will shed light on this within the year.

Will we ever fully understand reality? Can we ever fully know the inner workings of the universe? Theoretical physicist Carlo Rovelli thinks we’re asking all the wrong questions. Inspired by the monumental, mind-bending artworks of Anish Kapoor, Rovelli explains how we must let go of old ideas and accept that we will never know everything about the universe.

Speaking to New Scientist reporter Michael Brooks, Rovelli questions whether space even exists and criticises the pursuit of unfounded theories. His radical perspective suggests everything is connected, from our atoms to our soul, and the new challenge is finding a language that brings all aspects of reality into the conversation.

Rovelli is a theoretical physicist and author based at Aix-Marseille University in France, whose work focuses on loop quantum gravity, which aims to unify quantum mechanics and Albert Einstein’s general theory of relativity.

For decades, the idea has been dismissed as too strange to take seriously. But experiments involving microtubules, anaesthetics and brain organoids are beginning to test whether quantum effects could play a role in consciousness.

We explore Roger Penrose and Stuart Hameroff’s controversial Orch OR theory, the evidence for and against it and whether quantum computers could one day help reveal what consciousness really is. We also venture into whether observation and consciousness could play a fundamental role in shaping reality itself.

Ghostly particles called neutrinos pose some of the biggest mysteries of modern physics, but researchers thought they could get a handle on them by corralling them into a laser beam. Two new analyses show that neutrinos are more slippery than that, making the proposed neutrino laser design impossible.

Researchers have been studying neutrinos since the 1940s. They are among the most abundant particles in the universe, but much about them remains unknown. Notably, they are extremely light, mere ghosts compared with more massive particles like neutrons, yet their exact mass is unclear.��

In 2025,  at the University of Manchester in the UK and  at the Massachusetts Institute of Technology (MIT) suggested a novel and surprising way to gain clarity –  using thousands of extremely cold radioactive atoms to create a laser beam of neutrinos.

, also at MIT, heard a lecture about the idea and immediately worried about it being too good to be true. He and his colleagues have now confirmed that hunch with two rigorous mathematical investigations.

Neutrinos are produced when radioactive atoms undergo nuclear decay. Jones and Formaggio theorised that if many such decaying atoms were pushed into a quantum phase of matter called a “Bose-Einstein condensate” (BEC), where they all share a quantum state, then their respective neutrino emissions would be amplified, forming a laser-like beam. Creating such a BEC would require making thousands of radioactive atoms extremely cold so they could behave quantumly, which is a big technical challenge.��

But Ketterle, who received the Nobel prize for creating some of the first ever BECs in the 1990s, and his team uncovered a more fundamental obstacle.

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The key to the neutrino laser proposal was a memory effect: when an atom in the BEC emitted a neutrino, it would be more likely to continue emitting more neutrinos in the same direction, thus pushing them into a beam, because the quantum state that all the ultracold atoms share would retain a trace of that first emission. Ketterle and his colleagues showed that this memory, although present, would be about 10,000 billion times too brief to affect the neutrinos as intended. Even more troublingly, the team uncovered that the memory would actually have the opposite effect from that intended, which Ketterle calls an anti-memory.��

“If I am an atom and I have emitted a neutrino, I am not allowed to [immediately] emit a neutrino again,” he says. This effect’s origin is subtle, stemming from neutrinos being a type of particle called fermions, which fundamentally behave differently than particles of light that our ideas about lasers tend to be built upon.��

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“I think these papers sharpen where the real difficulty lies,” says  at Queen’s University in Canada. “For nuclear-scale energies [pertaining to atoms’ decay], these requirements become extraordinarily demanding.” 

He says the new analysis does not categorically rule out every possible way to build a neutrino laser, but shows that the most conventional scenario where each atom emits one neutrino cannot work. If each atom emitted two neutrinos at a time, the analysis may be different, he says. “I think the interesting scientific question now becomes more precise rather than disappearing: what kinds of nuclear or neutrino processes, if any, avoid the limitations they have identified?” says Leach. In his view, this question is most likely to be definitively answered through experiments.��

Formaggio and Jones didn’t respond New Scientist’s request for comment.

For Ketterle, the lesson of the neutrino laser that couldn’t be is that science can correct itself even when doing so means abandoning inspiring and creative ideas. Getting clarity required hours of discussion, including with Jones and Formaggio. But that is ultimately how physics ought to work, he says.