A single particle in the deep sea could prove Stephen Hawking right about the early universe
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Five decades ago, famed astrophysicist Stephen Hawking theorized that the Big Bang may have flooded the universe with tiny black holes. Now, researchers believe they may have seen one explode.
In Feb. 2025, the European collaboration KM3NeT — which consists of underwater detectors off the coasts of France, Italy and Greece — announced the discovery of a stupendously powerful neutrino. This ghostly particle had an energy of around 100 PeV — over 25 times more energetic than the particles accelerated in the Large Hadron Collider, the world's most powerful atom smasher.
Physicists have struggled to come up with an explanation for such an energetic neutrino. But now, a team of researchers who were not involved in the original detection have proposed a surprising hypothesis: The neutrino is the signature of an evaporating black hole. The team described their proposal in a paper that was uploaded to the arXiv database and has not been peer-reviewed yet.
In the 1970s, Hawking realized that black holes aren't entirely black. Instead, through complex interactions between the black hole event horizon and the quantum fields of space-time, they can emit a slow-but-steady stream of radiation, now known as Hawking radiation. This means black holes evaporate and eventually disappear. In fact, as the black hole gets smaller, it emits even more radiation, until it essentially explodes in a firestorm of high-energy particles and radiation — like the neutrino spotted by the KM3Net collaboration.
Related: Stephen Hawking's black hole radiation paradox could finally be solved — if black holes aren't what they seem
But all known black holes are very large — at least a few times the mass of the sun, and often significantly larger. It will take well over 10^100 years for even the smallest known black holes to die. If the KM3NeT neutrino is due to an exploding black hole, it has to be much smaller — somewhere around 22,000 pounds (10,000 kilograms). That's about as heavy as two fully grown African elephants, compressed into a black hole smaller than an atom.
The only known potential way to produce such tiny black holes is in the chaotic events of the early Big Bang, which may have flooded the cosmos with "primordial" black holes. The smallest primordial black holes produced in the Big Bang would have exploded long ago, while larger ones might persist to the present day.
Unfortunately, a 22,000-pound black hole should not survive all the way from the Big Bang to the present day. But the authors pointed out that there might be an additional quantum mechanism — known as "memory burden" — that allows black holes to resist decay. This would allow a 22,000-pound black hole to survive for billions of years before it finally exploded, sending a high-energy neutrino toward Earth in the process.
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Primordial black holes might be an explanation for dark matter — the invisible substance that accounts for most of the matter in the universe — but so far, searches for them have turned up empty. This new insight may provide an intriguing clue. The researchers found that if primordial black holes of this mass range are abundant enough to account for all the dark matter, they should be exploding somewhat regularly. They estimated that if this hypothesis is correct, the KM3NeT collaboration should see another showstopping neutrino in the next few years.
If that detection happens, then we may just have to radically rethink the way we approach dark matter, high-energy neutrinos and even the physics of the early universe.
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When you buy through links on our articles, Future and its syndication partners may earn a commission. DENVER—Psilocybin, the main psychoactive ingredient in magic mushrooms, can alleviate depression for at least five years after a single dose, a new study finds. The research, presented June 18 at the Psychedelic Science 2025 conference in Denver, focused on patients with major depressive disorder (MDD), which is often called clinical depression. The serious mood disorder causes a persistent feeling of sadness and a loss of interest or pleasure in activities that were once enjoyable. The most common treatments for MDD include talk therapy and medications such as selective serotonin reuptake inhibitors, and both can take a long time to show any benefits. When early studies hinted at psilocybin's potential as an antidepressant, a team of researchers undertook the first-ever randomized clinical trial to explore the use of the psychedelic for treating severe depression. The trial included 24 patients, half of whom received psilocybin at the very start of the trial and half of whom received the same dose eight weeks later—the "waitlist" group. Each patient also received 11 hours of psychotherapy. Even in that short time frame, "there was a significant reduction in depression in the immediate-treatment group compared to those on the waitlist," study co-author Alan Davis, director of the Center for Psychedelic Drug Research and Education at The Ohio State University, told Live Science. Once all of the patients had completed the four-week study, the psilocybin appeared to be four times more effective than traditional antidepressant medications, based on previous research data. One month after the treatment, 17 patients had relieved symptoms, including 14 who were in full remission from depression. Patients also responded much faster to psilocybin than is typical for conventional antidepressants. But do these benefits of psilocybin last? Related: Magic mushrooms temporarily 'dissolve' brain network responsible for sense of self Very few long-term studies of psilocybin for depression have been conducted to date, said Dr. Charles Raison, a professor of human ecology and psychiatry at the University of Wisconsin-Madison who was not involved in the research. "They are very difficult to do because people drop out," Raison told Live Science in an email. "But also because they go on all sorts of other treatments that obfuscate the degree to which any longer lasting benefits result from the psychedelic or because the participant got therapy or restarted an antidepressant." To investigate whether the benefits for psilocybin lasted and if the patients had experienced any side effects, the researchers contacted the original trial participants several years later to request their enrollment in a follow-up study. Twenty-one patients enrolled, and their clinicians rated any changes in the participants' levels of depression from before the original treatment to the present day. The patients also filled out a series of self-reported, online questionnaires and met up with clinicians to document their ability to engage in everyday tasks, their levels of anxiety and their general mental health. The researchers assumed that the three patients that didn't sign up for the follow up, and the three that didn't complete the questionnaires had not remained in remission. Even so, the researchers found that 67% of the participants who had suffered from depression half a decade earlier remained in remission after a single psychedelic therapy session. These patients also reported less anxiety and less difficulty functioning on a daily basis. In general, the two-thirds of the patients who responded well reported lasting positive changes in their mindsets, emotional health and relationships. "I'm excited by these deeper aspects of their lives that really speaks to the importance of these interventions beyond just reduction of depression," Davis said. RELATED STORIES —Psychedelics rapidly change the brain. Here's how. —Australia clears legal use of MDMA and psilocybin to treat PTSD and depression —'Magic mushroom' treatment for depression inches closer to approval Most of the patients shared that, following the original treatment, they'd engaged in self-reflection and therapy to help understand themselves and navigate life's challenges. Davis hypothesizes that the psychedelic experience catalyzes a deeper therapy process and would like to conduct future studies comparing the relative influences of psilocybin and psychotherapy in alleviating depression. "The biggest caveat of this study is the small sample size, and the fact that the original trial showed larger antidepressant effects than subsequent larger multi-site studies seem to be showing," Raison said. In a multi-site clinical trial with 233 participants, 37% of the 79 who received a single 25 mg dose of psilocybin, coupled with psychotherapy, went into remission from major depression. While these trials report less widespread antidepressant effects, they support the idea that psilocybin can effectively treat depression, Davis said, and he is keen to see how the findings of multi-site trials hold up five years post-treatment.
