Latest news with #physicists
France 24
2 days ago
- Science
- France 24
Physicists still divided about quantum world, 100 years on
"Shut up and calculate!" is a famous quote in quantum physics that illustrates the frustration of scientists struggling to unravel one of the world's great paradoxes. For the last century, equations based on quantum mechanics have consistently and accurately described the behaviour of extremely small objects. However, no one knows what is happening in the physical reality behind the mathematics. The problem started at the turn of the 20th century, when scientists realised that the classical principles of physics did not apply to things on the level on atoms. Bafflingly, photons and electrons appear to behave like both particles and waves. They can also be in different positions simultaneously -- and have different speeds or levels of energy. In 1925, Austrian physicist Erwin Schroedinger and Germany's Werner Heisenberg developed a set of complex mathematical tools that describe quantum mechanics using probabilities. This "wave function" made it possible to predict the results of measurements of a particle. These equations led to the development of a huge amount of modern technology, including lasers, LED lights, MRI scanners and the transistors used in computers and phones. But the question remained: what exactly is happening in the world beyond the maths? A confusing cat To mark the 100th year of quantum mechanics, many of the world's leading physicists gathered last month on the German island of Heligoland, where Heisenberg wrote his famous equation. More than 1,100 of them responded to a survey conducted by the leading scientific journal Nature. The results showed there is a "striking lack of consensus among physicists about what quantum theory says about reality", Nature said in a statement. More than a third -- 36 percent -- of the respondents favoured the mostly widely accepted theory, known as the Copenhagen interpretation. In the classical world, everything has defined properties -- such as position or speed -- whether we observe them or not. But this is not the case in the quantum realm, according to the Copenhagen interpretation developed by Heisenberg and Danish physicist Niels Bohr in the 1920s. It is only when an observer measures a quantum object that it settles on a specific state from the possible options, goes the theory. This is described as its wave function "collapsing" into a single possibility. The most famous depiction of this idea is Schroedinger's cat, which remains simultaneously alive and dead in a box -- until someone peeks inside. The Copenhagen interpretation "is the simplest we have", Brazilian physics philosopher Decio Krause told Nature after responding to the survey. Despite the theory's problems -- such as not explaining why measurement has this effect -- the alternatives "present other problems which, to me, are worse," he said. Enter the multiverse But the majority of the physicists supported other ideas. Fifteen percent of the respondents opted for the "many worlds" interpretation, one of several theories in physics that propose we live in a multiverse. It asserts that the wave function does not collapse, but instead branches off into as many universes as there are possible outcomes. So when an observer measures a particle, they get the position for their world -- but it is in all other possible positions across many parallel universes. "It requires a dramatic readjustment of our intuitions about the world, but to me that's just what we should expect from a fundamental theory of reality," US theoretical physicist Sean Carroll said in the survey. The quantum experts were split on other big questions facing the field. Is there some kind of boundary between the quantum and classical worlds, where the laws of physics suddenly change? Forty-five percent of the physicists responded yes to this question -- and the exact same percentage responded no. Just 24 percent said they were confident the quantum interpretation they chose was correct. And three quarters believed that it will be replaced by a more comprehensive theory one day.
Gizmodo
2 days ago
- Science
- Gizmodo
After 100 Years of Quantum Mechanics, Physicists Still Can't Agree on Anything
In July 1925—exactly a century ago—famed physicist Werner Heisenberg wrote a letter to his equally famous colleague, Wolfgang Pauli. In it, Heisenberg confesses that his 'views on mechanics have become more radical with each passing day,' requesting Pauli's prompt feedback on an attached manuscript he's considering whether to 'complete…or to burn.' That was the Umdeutung (reinterpretation) paper, which set the foundation for a more empirically verifiable version of quantum mechanics. For that reason, scientists consider Umdeutung's publication date as quantum mechanics's official birthday. To commemorate this 100th anniversary, Nature asked 1,101 physicists for their take on the field's most fiercely debated questions, revealing that, as in the past, the field of quantum physics remains a hot mess. Published today, the survey shows that physicists rarely converge on their interpretations of quantum mechanics and are often unsure about their answers. They tend to see eye-to-eye on two points: that a more intuitive, physical interpretation of math in quantum mechanics is valuable (86%), and that, perhaps ironically, quantum theory itself will eventually be replaced by a more complete theory (75%). A total of 15,582 physicists were contacted, of which 1,101 responded, giving the survey a 7% response rate. Of the 1,101, more than 100 respondents sent additional written answers with their takes on the survey's questions. Participants were asked to name their favored interpretation of the measurement problem, a long-standing conundrum in quantum theory regarding the uncertainty of quantum states in superposition. No clear majority emerged from the options given. The frontrunner, with 36%, was the Copenhagen interpretation, in which (very simply) quantum worlds are distinct from classical ones, and particles in quantum states only gain properties when they're measured by an observer in the classical realm. It's worth noting that detractors of the Copenhagen interpretation scathingly refer to it as the 'shut up and calculate' approach. That's because it often glosses over weedy details for more practical pursuits, which, to be fair, is really powerful for things like quantum computing. However, more than half of physicists who chose the Copenhagen interpretation admitted they weren't too confident in their answers, evading follow-up questions asking them to elaborate. Still, more than half of the respondents, 64%, demonstrated a 'healthy following' of several other, more radical viewpoints. These included information-based approaches (17%), many worlds (15%), and the Bohm-de Broglie pilot wave theory (7%). Meanwhile, 16% of respondents submitted written answers that either rejected all options, claimed we don't need any interpretations, or offered their personal takes on the best interpretation of quantum mechanics. So, much like many other endeavors in quantum mechanics, we'll just have to see what sticks (or more likely, what doesn't). Physicists who discussed the results with Nature had mixed feelings about whether the lack of consensus is concerning. Elise Crull at the City University of New York, for instance, told Nature that the ambiguity suggests 'people are taking the question of interpretations seriously.' Experts at the cross-section of philosophy and physics were more critical. Tim Maudlin, a philosopher of physics at New York University, told Gizmodo that the survey's categorization of certain concepts is misleading and conducive to contradictory answers—a discrepancy that the respondents don't seem to have realized, he said. 'I think the main takeaway from this is that physicists do not think clearly—and have not formed strongly held views—about foundational issues in quantum theory,' commented Maudlin, my professor in graduate school. In an email to Gizmodo, Sean Carroll, a theoretical physicist at Johns Hopkins who responded to the survey, expressed similar concerns. Several factors may be behind this lack of consensus, he said, but there's a prevalent view that it 'doesn't matter as long as we can calculate experimental predictions,' which he said is 'obviously wrong.' 'It would be reasonable if we thought we otherwise knew the final theory of physics and had no outstanding puzzles,' added Carroll, who was part of an expert group consulted for the survey. 'But nobody thinks that.' 'It's just embarrassing that we don't have a story to tell people about what reality is,' admitted Carlton Caves, a theoretical physicist at the University of New Mexico in Albuquerque who participated in the survey, in Nature's report. However, the survey's results do seem to hint at a general belief in the importance of a solid theoretical groundwork, with almost half of the participants agreeing that physics departments don't give sufficient attention to quantum foundations. On the other hand, 58% of participants answered that experimental results will help inform which theory ends up being 'the one.' For better or worse, the survey represents the lively, fast-developing field of quantum science—which, if you've been following our coverage, can get really, really weird. A lack of explanation or consensus isn't necessarily bad science—it's just future science. After all, quantum mechanics, for all its complexity, remains one of the most experimentally verified theories in the history of science. It's fascinating to see how these experts can disagree so wildly about quantum mechanics, yet still offer solid evidence to support their views. Sometimes, there's no right or bad answer—just different ones. For you fellow quantum enthusiasts, I highly recommend that you check out the full report for the entire account of how and where physicists were split. You can also find the original survey, the methodology, and an anonymized version of all the answers at the end of the report. And if you do take the survey, or at least part of it, feel free to share your answers. Oh, and let me know whether you believe Heisenberg should have burned Umdeutung after all.
Yahoo
23-07-2025
- Science
- Yahoo
Yes, It's Possible to Safely Jump Into a Black Hole, Scientists Say
Here's what you'll learn when you read this story: Scientists say humans could indeed enter a black hole to study it. Of course, the human in question couldn't report their findings—or ever come back. The reason is that supermassive black holes are much more hospitable. In a finding ripped from Interstellar, scientists say humans can indeed explore black holes firsthand. The catch? If you're going to jump into a black hole, don't plan on ever jumping back out into our universe. 'A human can do this only if the respective black hole is supermassive and isolated, and if the person entering the black hole does not expect to report the findings to anyone in the entire Universe,' Grinnell College physicists explain in a new article in The Conversation. That's because of special physics found in supermassive black holes, resulting in a combination of gravity and event horizon that wouldn't instantaneously pull the human being into a very dead piece of spaghetti. Because supermassive black holes are much bigger than stellar and intermediate black holes, all the parts of them are more spread out. A person falling in would make it to the event horizon—the border of the black hole beyond which not even light can escape, and where gravity is so strong that light will orbit the black hole like planets orbit stars—a lot sooner than in a smaller black hole. The person would stay cognizant and intact for longer. But, of course, they would never emerge—making this a one-way rollercoaster ride of scientific discovery into oblivion. Why does the math work this way? It's a matter of facts about black holes of different sizes, the researchers say: 'For a black hole with a mass of our Sun (one solar mass), the event horizon will have a radius of just under 2 miles. The supermassive black hole at the center of our Milky Way galaxy, by contrast, has a mass of roughly 4 million solar masses, and it has an event horizon with a radius of 7.3 million miles or 17 solar radii. This implies, due to the closeness of the black hole's center, that the black hole's pull on a person will differ by a factor of 1,000 billion times between head and toe, depending on which is leading the free fall.' This means avoiding 'spaghettification' (really!) and a safe, gentle float past the event horizon. Why does stuff go in but never come out? Well, scientists have only begun to understand the specific instances in which black holes eject energy or information—and that's unlikely to ever take the form of a missive, or even Morse code message, from a disappearing astronaut. Those black holes are very old, for example, with different physics than this special case. But, like in Interstellar, our imaginations reel at the idea of studying a black hole from the inside. Perhaps in some far future, someone will invent the right kind of tether to pull someone back out. And in that case, we can confirm some of the facts of life in a black hole, time dilation or not. Get the Issue Get the Issue Get the Issue Get the Issue Get the Issue Get the Issue Get the IssueGet the Issue Get the Issue You Might Also Like The Do's and Don'ts of Using Painter's Tape The Best Portable BBQ Grills for Cooking Anywhere Can a Smart Watch Prolong Your Life? Solve the daily Crossword
Yahoo
14-07-2025
- Science
- Yahoo
Experts ask where the center of the universe is
When you buy through links on our articles, Future and its syndication partners may earn a commission. This article was originally published at The Conversation. The publication contributed the article to Expert Voices: Op-Ed & Insights. About a century ago, scientists were struggling to reconcile what seemed a contradiction in Albert Einstein's theory of general relativity. Published in 1915, and already widely accepted worldwide by physicists and mathematicians, the theory assumed the universe was static – unchanging, unmoving and immutable. In short, Einstein believed the size and shape of the universe today was, more or less, the same size and shape it had always been. But when astronomers looked into the night sky at faraway galaxies with powerful telescopes, they saw hints the universe was anything but that. These new observations suggested the opposite – that it was, instead, expanding. Scientists soon realized Einstein's theory didn't actually say the universe had to be static; the theory could support an expanding universe as well. Indeed, by using the same mathematical tools provided by Einstein's theory, scientists created new models that showed the universe was, in fact, dynamic and evolving. I've spent decades trying to understand general relativity, including in my current job as a physics professor teaching courses on the subject. I know wrapping your head around the idea of an ever-expanding universe can feel daunting – and part of the challenge is overriding your natural intuition about how things work. For instance, it's hard to imagine something as big as the universe not having a center at all, but physics says that's the reality. First, let's define what's meant by "expansion." On Earth, "expanding" means something is getting bigger. And in regard to the universe, that's true, sort of. Expansion might also mean "everything is getting farther from us," which is also true with regard to the universe. Point a telescope at distant galaxies and they all do appear to be moving away from us. What's more, the farther away they are, the faster they appear to be moving. Those galaxies also seem to be moving away from each other. So it's more accurate to say that everything in the universe is getting farther away from everything else, all at once. This idea is subtle but critical. It's easy to think about the creation of the universe like exploding fireworks: Start with a big bang, and then all the galaxies in the universe fly out in all directions from some central point. But that analogy isn't correct. Not only does it falsely imply that the expansion of the universe started from a single spot, which it didn't, but it also suggests that the galaxies are the things that are moving, which isn't entirely accurate. It's not so much the galaxies that are moving away from each other – it's the space between galaxies, the fabric of the universe itself, that's ever-expanding as time goes on. In other words, it's not really the galaxies themselves that are moving through the universe; it's more that the universe itself is carrying them farther away as it expands. A common analogy is to imagine sticking some dots on the surface of a balloon. As you blow air into the balloon, it expands. Because the dots are stuck on the surface of the balloon, they get farther apart. Though they may appear to move, the dots actually stay exactly where you put them, and the distance between them gets bigger simply by virtue of the balloon's expansion. Now think of the dots as galaxies and the balloon as the fabric of the universe, and you begin to get the picture. Unfortunately, while this analogy is a good start, it doesn't get the details quite right either. Important to any analogy is an understanding of its limitations. Some flaws are obvious: A balloon is small enough to fit in your hand – not so the universe. Another flaw is more subtle. The balloon has two parts: its latex surface and its air-filled interior. These two parts of the balloon are described differently in the language of mathematics. The balloon's surface is two-dimensional. If you were walking around on it, you could move forward, backward, left, or right, but you couldn't move up or down without leaving the surface. Now it might sound like we're naming four directions here – forward, backward, left and right – but those are just movements along two basic paths: side to side and front to back. That's what makes the surface two-dimensional – length and width. The inside of the balloon, on the other hand, is three-dimensional, so you'd be able to move freely in any direction, including up or down – length, width and height. This is where the confusion lies. The thing we think of as the "center" of the balloon is a point somewhere in its interior, in the air-filled space beneath the surface. But in this analogy, the universe is more like the latex surface of the balloon. The balloon's air-filled interior has no counterpart in our universe, so we can't use that part of the analogy – only the surface matters. So asking, "Where's the center of the universe?" is somewhat like asking, "Where's the center of the balloon's surface?' There simply isn't one. You could travel along the surface of the balloon in any direction, for as long as you like, and you'd never once reach a place you could call its center because you'd never actually leave the surface. In the same way, you could travel in any direction in the universe and would never find its center because, much like the surface of the balloon, it simply doesn't have one. Part of the reason this can be so challenging to comprehend is because of the way the universe is described in the language of mathematics. The surface of the balloon has two dimensions, and the balloon's interior has three, but the universe exists in four dimensions. Because it's not just about how things move in space, but how they move in time. Our brains are wired to think about space and time separately. But in the universe, they're interwoven into a single fabric, called 'space-time.' That unification changes the way the universe works relative to what our intuition expects. And this explanation doesn't even begin to answer the question of how something can be expanding indefinitely – scientists are still trying to puzzle out what powers this expansion. So in asking about the center of the universe, we're confronting the limits of our intuition. The answer we find – everything, expanding everywhere, all at once – is a glimpse of just how strange and beautiful our universe is. This article is republished from The Conversation under a Creative Commons license. Read the original article.
Yahoo
14-07-2025
- Science
- Yahoo
Scientists Detect Sign of Something Impossible Out in Deep Space
The very concept of black holes seems improbable. Albert Einstein infamously refused to believe they could exist, even though his theory of general relativity was instrumental in predicting them. Now, scientists have witnessed evidence of something about these baffling cosmic monstrosities that further stretches the boundaries of both physics and credulity: a titanic collision of two already enormous black holes so utterly extreme that it has scientists wondering if the event they seem to have detected is even possible. As detailed in a new yet-to-be-peer-reviewed paper by a consortium of physicists, the resulting black hole, whose signal has been designated GW231123, boasts an astonishing mass about 225 times that of our Sun — easily making it the largest black hole merger ever detected. Previously, the record was held by a merger that formed a black hole of about 140 solar masses. "Black holes this massive are forbidden through standard stellar evolution models," Mark Hannam at the Laser Interferometer Gravitational-Wave Observatory (LIGO), which made the detection, said in a statement about the work. "This is the most massive black hole binary we've observed through gravitational waves, and it presents a real challenge to our understanding of black hole formation." Black holes can produce huge, propagating ripples in spacetime called gravitational waves, which were predicted by Einstein back in 1916. Nearly 100 years later, LIGO — which consists of two observatories on opposite corners of the US — made history by making the first ever detection of these cosmic shudders. The merger was first spotted in November 2023 in a gravitational wave, GW231123, that lasted just a fraction of a second. Even so, it was enough to infer the properties of the original black holes. One had a mass roughly 137 times the mass of the Sun, and the other was around 103 solar masses. During the lead up to the merger, the pair circled around each other like fighters in a ring, before finally colliding to form one. These black holes are physically problematic because it's likely that one, if not both of them, fall into an "upper mass gap" of stellar evolution. At such a size, it's predicted that the stars that formed them should have perished in an especially vicious type of explosion called a pair-instability supernova, which results in the star being completely blown apart, leaving behind no remnant — not even a black hole. Some astronomers argue that the "mass gap" is really a gap in our observations and not the cause of curious physics. Nonetheless, the idea is "a hill at least some people were willing to get wounded on, if not necessarily die on," Cole Miller of the University of Maryland, who was not involved in the research, told ScienceNews. But perhaps the black holes weren't born from a single star. "One possibility is that the two black holes in this binary formed through earlier mergers of smaller black holes," Hannam said in the statement. Equally extreme as their weight classes are their ludicrously fast spins, with the larger spinning at 90 percent of its maximum possible speed and the other at 80 percent, both of which are equal to very significant fractions of the speed of light. In earthly terms, it's somewhere around 400,000 times our planet's rotation speed, according to the scientists. "The black holes appear to be spinning very rapidly — near the limit allowed by Einstein's theory of general relativity," Charlie Hoy, a member of the LIGO Scientific Collaboration at the University of Portsmouth, said in the statement. "That makes the signal difficult to model and interpret. It's an excellent case study for pushing forward the development of our theoretical tools." The researchers will present their findings at the GR-Amaldi meeting in Glasgow, which takes place this week. "It will take years for the community to fully unravel this intricate signal pattern and all its implications," according to LIGO member Gregorio Carullo at the University of Birmingham — so, tantalizingly, we're likely only scratching the surface of this mystery. More on space: James Webb Space Telescope Spots Stellar Death Shrouds
