One of physicist Stephen Hawking’s most famous paradoxes may finally be solved: Black holes may in fact hang onto information about the massive stars that created them, new research indicates.
This information may lurk in the radiation around black holes – colloquially known as “quantum hair” – and could, in theory, be retrieved to retell the origins of those black holes, the research suggests.
These findings, published March 6 in the journal Physics Letters B. (opens in new tab) , may finally resolve a thorny problem that Hawking was working on in his last years.
Related: Stephen Hawking’s final book says there’s ‘no possibility’ of God in our universe
According to Hawking’s work, radiation slowly “leaks” out of black holes in the form of thermal energy, which has come to be known as “Hawking radiation.” But because of its thermal nature, this radiation can’t carry information. That means that as black holes evaporate, they methodically destroy all information about the stars that created them. This is contrary to the laws of quantum mechanics, which say that information cannot be destroyed and that an object’s final state can reveal clues about its initial state. This problem has troubled cosmologists for decades and is known as the “Hawking information paradox.”
“[This research] is the final nail in the coffin for the paradox because we now understand the exact physical phenomenon by which information escapes a decaying black hole,” lead study author Xavier Calmet (opens in new tab) , a professor of physics at the University of Sussex, told Live Science via email. He suggests a modification to Hawking radiation that makes it “non-thermal” and thus capable of carrying information with it away from the final fate of the black hole.
Physicist Stephen Hawking in his office in 1989. (Image credit: Jean-Regis Rouston/Roger Viollet via Getty Images) The black hole problem
Black holes are objects so massive that nothing can escape the pull of their gravity, not even light. They form when enormous stars run out of fuel and collapse in on themselves.
In classical physics, black holes are “very simple objects,” Calmet said. “So simple that they can be characterized by three numbers: their mass, angular momentum, and electric charge.”
Famous physicist John Wheeler described this lack of distinguishing characteristics by saying “black holes have no hair.” But, Calmet explained, while the final black hole is very simple, the original star that birthed it is a complex astrophysical object, consisting of a complicated amalgam of protons, electrons, and neutrons which come together to form the elements that build the chemical composition of that star.
While black holes carry no “memory” of the stars they once were, the rules of quantum physics say that information can’t simply be erased from the universe. In 1976, Hawking introduced a fly to this cosmic ointment by showing this information couldn’t dwell indefinitely within black holes sealed away from the outside universe either. Applying the rules of quantum mechanics to black holes, Hawking suggested they emit a type of thermal radiation, later called Hawking radiation. Over immense periods of time, the leaking of this radiation causes black holes to completely evaporate, leaving only a vacuum behind. In this way, information is irretrievably lost.
“This is however not allowed by quantum physics, which posits that the movie of this black hole’s ‘life’ could be rewound,” Calmet said. “Starting from the radiation we should be able to rebuild the original black hole and then eventually the star.”Finding the black hole’s ‘hair’
Along with his colleague Steve Hsu (opens in new tab) , a professor of theoretical physics at Michigan State University, Calmet has been working since 2021 to crack Hawking’s paradox. In a previous study, published in March 2022, the team argued that black holes do indeed have “quantum hair,” in the form of a unique quantum imprint in the gravitational fields that surround them
In their new research, the team reassessed Hawking’s 1976 calculations, but this time accounted for the effects of “quantum gravity” — the description of gravity according to the principles of quantum mechanics — something Hawking hadn’t done. Related stories— The 12 Strangest Objects in the Universe
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“While these quantum gravitational corrections are minuscule, they are crucial for black hole evaporation,” Calmet said. “We were able to show that these effects modify Hawking radiation in such a way that this radiation becomes non-thermal. In other words, factoring in quantum gravity the radiation can contain information.”
While the quantum hair suggested in Calmetand Hsu’s previous work was an abstract mathematical concept, the team has now identified the exact physical phenomenon by which information escapes the black hole via Hawking radiation, and how it could be retrieved by an outside observer. This is currently not possible, as it would require an instrument sensitive enough to measure Hawking radiation, which currently is purely theoretical.
Currently there is no real way for astrophysicists to measure the effect the researchers propose, as it is minuscule, Calmet acknowledged. Instead, he suggests one way to progress this theory would be by studying simulations of black holes in labs on Earth. The team’s mathematical modeling of Hawking radiation and black holes could prove invaluable in these simulations.
Mark Zuckerberg’s announcement this week that Meta would pivot its moderation policies to allow more “free expression” was widely viewed as the company’s latest effort to appease President-elect Donald Trump.
More than any of its Silicon Valley peers, Meta has taken numerous public steps to make amends with Trump since his election victory in November.
That follows a highly contentious four years between the two during Trump’s first term in office, which ended with Facebook — similar to other social media companies — banning Trump from its platform.
As recently as March, Trump was using his preferred nickname of “Zuckerschmuck” when talking about Meta’s CEO and declaring that Facebook was an “enemy of the people.”
With Meta now positioning itself to be a key player in artificial intelligence, Zuckerberg recognizes the need for White House support as his company builds data centers and pursues policies that will allow it to fulfill its lofty ambitions, according to people familiar with the company’s plans who asked not to be named because they weren’t authorized to speak on the matter.
“Even though Facebook is as powerful as it is, it still had to bend the knee to Trump,” said Brian Boland, a former Facebook vice president, who left the company in 2020.
Meta declined to comment for this article.
In Tuesday’s announcement, Zuckerberg said Meta will end third-party fact-checking, remove restrictions on topics such as immigration and gender identity and bring political content back to users’ feeds. Zuckerberg pitched the sweeping policy changes as key to stabilizing Meta’s content-moderation apparatus, which he said had “reached a point where it’s just too many mistakes and too much censorship.”
The policy change was the latest strategic shift Meta has taken to buddy up with Trump and Republicans since Election Day.
A day earlier, Meta announced that UFC CEO Dana White, a longtime Trump friend, is joining the company’s board.
And last week, Meta announced that it was replacing Nick Clegg, its president of global affairs, with Joel Kaplan, who had been the company’s policy vice president. Clegg previously had a career in British politics with the Liberal Democrats party, including as a deputy prime minister, while Kaplan was a White House deputy chief of staff under former President George W. Bush.
Kaplan, who joined Meta in 2011 when it was still known as Facebook, has longstanding ties to the Republican Party and once worked as a law clerk for the late conservative Supreme Court Justice Antonin Scalia. In December, Kaplan posted photos on Facebook of himself with Vice President-elect JD Vance and Trump during their visit to the New York Stock Exchange.
Joel Kaplan, Facebook’s vice president of global policy, on April 17, 2018.
Niall Carson | PA Images | Getty Images
Many Meta employees criticized the policy change internally, with some saying the company is absolving itself of its responsibility to create a safe platform. Current and former employees also expressed concern that marginalized communities could face more online abuse due to the new policy, which is set to take effect over the coming weeks.
Despite the backlash from employees, people familiar with the company’s thinking said Meta is more willing to make these kinds of moves after laying off 21,000 employees, or nearly a quarter of its workforce, in 2022 and 2023.
Those cuts affected much of Meta’s civic integrity and trust and safety teams. The civic integrity group was the closest thing the company had to a white-collar union, with members willing to push back against certain policy decisions, former employees said. Since the job cuts, Zuckerberg faces less friction when making broad policy changes, the people said.
Zuckerberg’s overtures to Trump began in the months leading up to the election.
Following the first assassination attempt on Trump in July, Zuckerberg called the photo of Trump raising his fist with blood running down his face “one of the most badass things I’ve ever seen in my life.”
A month later, Zuckerberg penned a letter to the House Judiciary Committee alleging that the Biden administration had pressured Meta’s teams to censor certain Covid-19 content.
“I believe the government pressure was wrong, and I regret that we were not more outspoken about it,” he wrote.
After Trump’s presidential victory, Zuckerberg joined several other technology executives who visited the president-elect’s Mar-a-Lago resort in Florida. Meta also donated $1 million to Trump’s inaugural fund.
On Friday, Meta revealed to its workforce in a memo obtained by CNBC that it intends to shutter several internal programs related to diversity and inclusion in its hiring process, representing another Trump-friendly move.
The previous day, some details of the company’s new relaxed content-moderation guidelines were published by the news site The Intercept, showing the kind of offensive rhetoric that Meta’s new policy would now allow, including statements such as “Migrants are no better than vomit” and “I bet Jorge’s the one who stole my backpack after track practice today. Immigrants are all thieves.”
Recalibrating for Trump
Zuckerberg, who has been dragged to Washington eight times to testify before congressional committees during the last two administrations, wants to be perceived as someone who can work with Trump and the Republican Party, people familiar with the matter said.
Though Meta’s content-policy updates caught many of its employees and fact-checking partners by surprise, a small group of executives were formulating the plans in the aftermath of the U.S. election results. By New Year’s Day, leadership began planning the public announcements of its policy change, the people said.
Meta typically undergoes major “recalibrations” after prominent U.S. elections, said Katie Harbath, a former Facebook policy director and CEO of tech consulting firm Anchor Change. When the country undergoes a change in power, Meta adjusts its policies to best suit its business and reputational needs based on the political landscape, Harbath said.
“In 2028, they’ll recalibrate again,” she said.
After the 2016 election and Trump’s first victory, for example, Zuckerberg toured the U.S. to meet people in states he hadn’t previously visited. He published a 6,000-word manifesto emphasizing the need for Facebook to build more community.
The social media company faced harsh criticism about fake news and Russian election interference on its platforms after the 2016 election.
Following the 2020 election, during the heart of the pandemic, Meta took a harder stand on Covid-19 content, with a policy executive saying in 2021 that the “amount of COVID-19 vaccine misinformation that violates our policies is too much by our standards.” Those efforts may have appeased the Biden administration, but it drew the ire of Republicans.
Meta is once again reacting to the moment, Harbath said.
“There wasn’t a business risk here in Silicon Valley to be more right-leaning,” Harbath said.
While Trump has offered few specific policy proposals for his second administration, Meta has plenty at stake.
The White House could create more relaxed AI regulations compared with those in the European Union, where Meta says harsh restrictions have resulted in the company not releasing some of its more advanced AI technologies. Meta, like other tech giants, also needs more massive data centers and cutting-edge computer chips to help train and run their advanced AI models.
“There’s a business benefit to having Republicans win, because they are traditionally less regulatory,” Harbath said.
Meta’s CEO Mark Zuckerberg reacts as he testifies during the Senate Judiciary Committee hearing on online child sexual exploitation at the U.S. Capitol in Washington, U.S., January 31, 2024.
Evelyn Hockstein | Reuters
Meta isn’t alone in trying to cozy up to Trump. But the extreme measures the company is taking reflects a particular level of animus expressed by Trump over the years.
Trump has accused Meta of censorship and has expressed resentment over the company’s two-year suspension of his Facebook and Instagram accounts following the Jan. 6 attack on the Capitol.
In July 2024, Trump posted on Truth Social that he intended to “pursue Election Fraudsters at levels never seen before, and they will be sent to prison for long periods of time,” adding “ZUCKERBUCKS, be careful!” Trump reiterated that statement in his book, “Save America,” writing that Zuckerberg plotted against him during the 2020 election and that the Meta CEO would “spend the rest of his life in prison” if it happened again.
Meta spends $14 million annually on providing personal security for Zuckerberg and his family, according to the company’s 2024 proxy statement. As part of that security, the company analyzes any threats or perceived threats against its CEO, according to a person familiar with the matter. Those threats are cataloged, analyzed and dissected by Meta’s multitude of security teams.
After Trump’s comments, Meta’s security teams analyzed how Trump could weaponize the Justice Department and the country’s intelligence agencies against Zuckerberg and what it would cost the company to defend its CEO against a sitting president, said the person, who asked not to be named because of confidentiality.
Meta’s efforts to appease the incoming president bring their own risks.
After Zuckerberg announced the new speech policy Tuesday, Boland, the former executive, was among a number of users who took to Meta’s Threads service to tell their followers that they were quitting Facebook.
“Last post before deleting,” Boland wrote in his post.
Before the post could be seen by any of his Threads followers, Meta’s content moderation system had taken it down, citing cybersecurity reasons.
Boland told CNBC in an interview that he couldn’t help but chuckle at the situation.
“It’s deeply ironic,” Boland said.
— CNBC’s Salvador Rodriguez contributed to this report.
The fires that have been raging in Los Angeles County this week may be the “most destructive” in modern US history.
In just three days, the blazes have covered tens of thousands of acres of land and could potentially have an economic impact of up to $150bn (£123bn), according to private forecaster Accuweather.
Sky News has used a combination of open-source techniques, data analysis, satellite imagery and social media footage to analyse how and why the fires started, and work out the estimated economic and environmental cost.
More than 1,000 structures have been damaged so far, local officials have estimated. The real figure is likely to be much higher.
“In fact, it’s likely that perhaps 15,000 or even more structures have been destroyed,” said Jonathan Porter, chief meteorologist at Accuweather.
These include some of the country’s most expensive real estate, as well as critical infrastructure.
Accuweather has estimated the fires could have a total damage and economic loss of between $135bn and $150bn.
“It’s clear this is going to be the most destructive wildfire in California history, and likely the most destructive wildfire in modern US history,” said Mr Porter.
“That is our estimate based upon what has occurred thus far, plus some considerations for the near-term impacts of the fires,” he added.
The calculations were made using a wide variety of data inputs, from property damage and evacuation efforts, to the longer-term negative impacts from job and wage losses as well as a decline in tourism to the area.
The Palisades fire, which has burned at least 20,000 acres of land, has been the biggest so far.
Satellite imagery and social media videos indicate the fire was first visible in the area around Skull Rock, part of a 4.5 mile hiking trail, northeast of the upscale Pacific Palisades neighbourhood.
These videos were taken by hikers on the route at around 10.30am on Tuesday 7 January, when the fire began spreading.
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At about the same time, this footage of a plane landing at Los Angeles International Airport was captured. A growing cloud of smoke is visible in the hills in the background – the same area where the hikers filmed their videos.
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The area’s high winds and dry weather accelerated the speed that the fire has spread. By Tuesday night, Eaton fire sparked in a forested area north of downtown LA, and Hurst fire broke out in Sylmar, a suburban neighbourhood north of San Fernando, after a brush fire.
These images from NASA’s Black Marble tool that detects light sources on the ground show how much the Palisades and Eaton fires grew in less than 24 hours.
On Tuesday, the Palisades fire had covered 772 acres. At the time of publication of Friday, the fire had grown to cover nearly 20,500 acres, some 26.5 times its initial size.
The Palisades fire was the first to spark, but others erupted over the following days.
At around 1pm on Wednesday afternoon, the Lidia fire was first reported in Acton, next to the Angeles National Forest north of LA. Smaller than the others, firefighters managed to contain the blaze by 75% on Friday.
On Thursday, the Kenneth fire was reported at 2.40pm local time, according to Ventura County Fire Department, near a place called Victory Trailhead at the border of Ventura and Los Angeles counties.
This footage from a fire-monitoring camera in Simi Valley shows plumes of smoke billowing from the Kenneth fire.
Sky News analysed infrared satellite imagery to show how these fires grew all across LA.
The largest fires are still far from being contained, and have prompted thousands of residents to flee their homes as officials continued to keep large areas under evacuation orders. It’s unclear when they’ll be able to return.
“This is a tremendous loss that is going to result in many people and businesses needing a lot of help, as they begin the very slow process of putting their lives back together and rebuilding,” said Mr Porter.
“This is going to be an event that is going to likely take some people and businesses, perhaps a decade to recover from this fully.”
The Data and Forensics team is a multi-skilled unit dedicated to providing transparent journalism from Sky News. We gather, analyse and visualise data to tell data-driven stories. We combine traditional reporting skills with advanced analysis of satellite images, social media and other open source information. Through multimedia storytelling we aim to better explain the world while also showing how our journalism is done.