Latest news with #generalrelativity
Yahoo
4 days ago
- Science
- Yahoo
An Astrophysicist Proposes We Send a Spacecraft to Visit a Black Hole
Black holes are some of the most mysterious objects in the Universe – a reputation not helped by the difficulty of studying them. Because these ultra-dense objects emit no light we can detect, we have to study them based on the effect they have on the space around them, from large distances across space-time. But there could be another way to get the skinny on these cosmic heavyweights. "I was looking for some completely new way to study black holes," astrophysicist Cosimo Bambi of Fudan University in China told ScienceAlert, "and I realized that an interstellar mission to the closest black hole is not unrealistic – but nobody had ever proposed it." Related: Physicists Simulated a Black Hole in The Lab, And Then It Began to Glow Black holes generate the strongest gravitational fields in the Universe, so strong that not even light is fast enough to achieve escape velocity from its powerful hold. Although we know a fair bit about how they behave, the measure of what we don't know about them is far greater than what we do. Additionally, the black hole gravitational regime would be one of the best in the Universe for testing general relativity, offering extreme conditions not found anywhere else that would really push the theory to its absolute limits. A probe orbiting a black hole would be able to perform tests, and take measurements of the black hole, that we can't do from Earth. "We do not know the structure of a black hole, namely of the region inside the event horizon. General relativity makes clear predictions, but some of them are certainly incorrect," Bambi said. "Black holes are therefore ideal laboratories to find possible deviations from the predictions of general relativity." In his proposal, Bambi lays out the physical feasibility of a black hole exploration mission, focusing on the two first hurdles that would need to be addressed: firstly, the identification of a suitable target; and secondly, the technology. To be clear, this is long-term planning. The technology we have now is not ready for such a mission, and the distances involved would mean a travel time of decades. But each journey begins with a single step – and without that step, the journey cannot take place. Finding a suitable black hole to visit is the first major hurdle. Currently, the closest known black hole to Earth resides at a distance of about 1,565 light-years. That's too far, really. There could, however, be black holes much closer. If they're just hanging out in space, not doing anything, black holes are hard to spot, but astronomers are getting better at finding them based on the way their gravitational field warps the space-time around them. Finding such a black hole nearby within the next decade or so isn't outside the realm of possibility. "I think we just need to be 'lucky' and have a black hole within 20 to 25 light-years. This is not under our control, of course. If there is a black hole within 20 to 25 light-years of the Solar System, we can develop the technology for such a mission," Bambi explained. "If the black hole is not within 20 to 25 light-years, but still within 40 to 50 light-years, the technological requirements are more challenging. If the black hole is at more than 40 to 50 light-years, I am afraid we have to give up." The next step would be how to get there. This would require the development of a craft that can travel at speeds up to a third of the speed of light, powered initially by Earth-based lasers, then by solar (or stellar) power as it makes its way to its destination – a journey of 70 years or so. "Two or more probes orbiting around the black hole would be the best option," Bambi said. "Generally speaking, we need that the probe gets as close as possible to the black hole, then it separates into a main probe (mothership) and many small probes. If these probes can communicate with each other through the exchange of electromagnetic signals, we can determine their exact trajectories around the black hole and how electromagnetic signals propagate around the black hole." Any data sent from the probe would then travel at light-speed to get back to Earth; at a distance of 20 light-years, that would mean an additional 20 years before data comes in, for a total mission duration of around a century or so. That's a long time, but it's worth thinking about now, even before a nearby black hole has been found, because such a mission would require a great deal of planning. And the results would absolutely be worth it, Bambi said. "I would hope to observe deviations from the predictions of general relativity and some clues to develop a theory beyond general relativity," he told ScienceAlert. In a statement, he adds, "It may sound really crazy, and in a sense closer to science fiction. But people said we'd never detect gravitational waves because they're too weak. We did – 100 years later. People thought we'd never observe the shadows of black holes. Now, 50 years later, we have images of two." The proposal has been published in iScience. Related News You're More Likely to Die From an Asteroid Than Rabies, Scientists Find Scientists Have Brewed a 'Super Alcohol' Theorized to Exist in Deep Space Earth Spun Faster Today. Here's How We Know. Solve the daily Crossword
Forbes
4 days ago
- Science
- Forbes
Black Hole Mission: The Trillion-Dollar Quest To Test Einstein
A spacecraft no larger than a paperclip, launched on a laser beam and traveling at near-light-speed on a 100-year voyage to the nearest known black hole. If successful, it would return data from close to the event horizon itself — the point of no return — after which gravity will consume it forever. This is the incredible mission being proposed by an astrophysicist after the answer to a fundamental question in science: Was Albert Einstein right? Black Hole Mission: Testing Einstein Although he describes it as both 'speculative' and 'challenging' (as well as costing around $1 trillion), black hole expert Cosimo Bambi at Fudan University, China, thinks it will soon be possible to design a mission capable of reaching a black hole within a human lifetime. Outlined today in a paper published in the journal iScience, Bambi's vision includes a gram-scale nanocraft propelled by Earth-based lasers. Its mission would be to test the limits of Einstein's theory of general relativity, published in 1915, which states that mass curves space-time, which in turn tells mass how to move. It also predicted the existence of black holes. The data collected by the probe could, says Bambi, alter scientists' understanding of general relativity and the rules of physics. Black Hole Mission: The Destination A black hole is a region of space-time where gravity is so strong that nothing can escape — not even light. The Milky Way has a supermassive black hole, Sagittarius A* (or Sgr A*, pronounced 'sadge-ay-star'), at its center. About 22 million miles across, it's about 27,000 light-years from the solar system at the galaxy's center and in March, scientists published a new polarised light image of the strong magnetic fields spiraling from its edge. That came in the wake of its groundbreaking images of a black hole at the heart of distant galaxy Messier 87 in 2019 and Sagittarius A* in 2022. This new mission won't go to Sagittarius A*, but to another as yet unfound black hole around 20-25 light-years from Earth, which probably exists. 'There have been new techniques to discover black holes,' says Bambi. 'I think it's reasonable to expect we could find a nearby one within the next decade.' It's challenging since black holes are virtually invisible to telescopes — their presence can only be inferred by their effect on nearby stars and light. Black Hole Mission: The Long Wait There's no rush to locate the closest black hole to the solar system because there is currently no way of launching such a mission. 'We don't have the technology now,' says Bambi. 'But in 20 or 30 years, we might.' The hope is that nanocrafts made from just a microchip and light sail could be blasted into space by Earth-based lasers at a third of the speed of light. With that speed, it would take about 70 years to traverse 20-25 light-years. Once at the black hole, the spacecraft would investigate whether the event horizon exists and whether the rules of physics change near a black hole. With that data collected, it would transmit it back to Earth, a process that would take 20 years. That makes the total mission duration about 80-100 years. 'It may sound really crazy, and in a sense closer to science fiction,' says Bambi. 'But people said we'd never detect gravitational waves because they're too weak. We did — 100 years later. People thought we'd never observe the shadows of black holes. Now, 50 years later, we have images of two.' Wishing you clear skies and wide eyes.
Yahoo
17-07-2025
- Science
- Yahoo
WA observatory at risk from Trump cuts helps make stunning black hole discovery
The LIGO Hanford Observatory near the Tri-Cities and its twin in Louisiana detected ripples of time and space passing through Earth from the most massive collision of black holes ever observed, a coalition of the world's four gravitational wave observatories announced Tuesday. The gravitational waves were confirmed by comparing signals from space that were detected by both U.S. LIGO observatories despite lasting only a 10th of a second. '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,' said Mark Hannam of Cardiff University in Wales, who is a member of a coalition of the world's gravitational wave observatories, in a statement. In addition to the large mass of the merging black holes, they also were spinning more rapidly than any previously detected black hole, approaching the limit allowed by Einstein's theory of general relativity. The international coalition, the LIGO-Virgo-KAGRA collaboration, described the detection in a fact sheet as an event 'both extraordinary and puzzling to interpret.' It is 'a potent reminder that the cosmos still holds many surprises, and we are only just beginning to uncover them,' it said. The interpretation of the data and the announcement came as the future of at least one of the U.S. LIGO observatories is in jeopardy as deep cuts to science programs are proposed by the Trump administration. Gravitational waves are caused by cataclysmic events in space, such as colliding black holes, merging neutron stars, exploding stars and possibly even the birth of the universe itself, according to CalTech, which is a joint operator and manager of the two LIGO observatories under an agreement with the National Science Foundation. Since the U.S. Laser Interferometer Gravitational-wave Observatories made scientific history in 2015 with the first-ever direct detection of gravitational waves, or ripples in space and time, from a black hole merger, about 300 more black hole mergers have been detected. The U.S. LIGO's have collaborated on discoveries with Italy's Virgo gravitational-wave observatory since 2007 and Japan's KAGRA observatory since 2019. Massive black hole The black hole collision detected on Nov. 23, 2023, in the United States, during an international observing run, produced a final black hole about 225 times the mass of Earth's sun. The two black holes that merged had individual masses of about 100 and 140 times that of the sun. 'It looks like we are seeing mergers of mergers,' which could lead to new information about steller evolution, said Michael Landry, head of the LIGO Hanford Observatory. Current stellar evolution models don't account for black holes so massive, which raises the possibility that what was detected was the merger of black holes, at least one of which had already merged to form a larger black hole, according to Hannam. The black holes could come from an extremely dense astrophysical environment, such as a nuclear star cluster or an active galactic nucleus, where black holes are more likely to collide, according to the LIGO-Virgo-KAGRA collaboration fact sheet. Now theories of steller evolution suggest that black holes with masses between about 60 and 130 solar masses, such as one of those in the detection announced Tuesday, should be rare or not even exist, according to the LIGO-Virgo-KAGRA collaboration. The initial merger detected in 2015, confirming Einstein's theory of relativity, had a final black hole mass of 62 times that of the sun. And until the one announced Tuesday, the most massive black hole merger detected was 140 times the mass of the sun, the same as the larger of the merging black holes in the new detection. 'This observation once again demonstrates how gravitational waves are uniquely revealing the fundamental and exotic nature of black holes throughout the universe,' said Dave Reitze, the executive director of LIGO at CalTech The high mass and extremely rapid spinning of the black holes that merged push the limits of both gravitational-wave detection technology and current theoretical models. Confirming LIGO detection The two black holes that collided were so incredibly heavy, that the signal they sent was lower in frequency and shorter compared to other detections, Landry said. In order to confirm that the the detection was from gravitational waves from space and not something on Earth, data from two or more sources was needed, in this case the Hanford and the Livingston, La., LIGOs, Landry said. Although just a tenth of a second long, the signal was 20 times louder than the typical detector noise, and a graph of the detections at both LIGOs closely match. They give a particularly clear view of the merger's grand finale when the newly formed black hole radiates energy through gravitational waves, vibrating and finally settling into a stable state, according to the LIGO-Virgo-KAGRA collaboration fact sheet. Extracting accurate information from the signal to make sure it was not a random blip in the data required the use of models that simulate what a signal would look like for different black hole pairs, accounting for the intricate dynamics of highly spinning black holes, according to the fact sheet. The modeling found that the probability of random noise mimicking the detection was less than once in 10,000 years. 'This gives us extreme confidence in the non-terrestrial origin of the signal, and thus in the reality of this gravitational-wave signal,' according to the fact sheet. The detection was from the fourth observing run of the collaboration and of the four international observatories that began in May 2023. Additional observations from the first half of the run through January 2024 will be published later this summer. Proposed LIGO closure The confirmation of the discovery of the heaviest black hole ever detected comes as the Trump administration's proposed budget for fiscal 2026 calls for closing either the Louisiana or Hanford LIGO. It is part of a 57% cut proposed by the administration for the National Science Foundation. The proposal has been given to Congress, which is working on bills now in the House and the Senate to set budgets for the National Science Foundation and its projects. According to LIGO CalTech, it is rare that a signal is so strong that a claim of detection can be made with just one observatory. Two or more detectors operating in unison are fundamental to LIGO's ability to contribute to the burgeoning field of gravitational wave astronomy, it said. To be able to hunt for and also find the visible light or other electromagnetic radiation associated with certain gravitational wave events using more traditional observatories, three or more gravitational-wave observatories are needed for triangulation to locate the region of the sky that contains the source of the wave, according to LIGO CalTech. To date, just one such source, the first-ever-known neutron star merger, has also been seen by observatories relying on light after a gravitational-wave detection. 'Though LIGO's mission is to detect gravitational waves from some of the most violent and energetic processes in the universe, the data LIGO collects may also contribute to other areas of physics such as gravitation, relativity, cosmology, astrophysics, particle physics and nuclear physics,' according to LIGO CalTech. 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
