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One of quantum physics’ greatest paradoxes may have lost its leading explanation

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Gravity is unlikely to be the cause of quantum collapse, suggests an underground experiment at Italy’s Gran Sasso National Laboratory.

 

Tommaso Guicciardini/Science Source

It’s one of the oddest tenets of quantum theory: a particle can be in two places at once—yet we only ever see it here or there. Textbooks state that the act of observing the particle “collapses” it, such that it appears at random in only one of its two locations. But physicists quarrel over why that would happen, if indeed it does. Now, one of the most plausible mechanisms for quantum collapse—gravity—has suffered a setback.

The gravity hypothesis traces its origins to Hungarian physicists Károlyházy Frigyes in the 1960s and Lajos Diósi in the 1980s. The basic idea is that the gravitational field of any object stands outside quantum theory. It resists being placed into awkward combinations, or “superpositions,” of different states. So if a particle is made to be both here and there, its gravitational field tries to do the same—but the field cannot endure the tension for long; it collapses and takes the particle with it.

Renowned University of Oxford mathematician Roger Penrose championed the hypothesis in the late 1980s because, he says, it removes the anthropocentric notion that the measurement itself somehow causes the collapse. “It takes place in the physics, and it’s not because somebody comes and looks at it.”

Still, the hypothesis seemed impossible to probe with any realistic technology, notes Diósi, now at the Wigner Research Center, and a co-author on the new paper. “For 30 years, I had been always criticized in my country that I speculated on something which was totally untestable.”

New methods now make this doable. In the new study, Diósi and other scientists looked for one of the many ways, whether by gravity or some other mechanism, that a quantum collapse would reveal itself: A particle that collapses would swerve randomly, heating up the system of which it is part. “It is as if you gave a kick to a particle,” says co-author Sandro Donadi of the Frankfurt Institute for Advanced Studies.

If the particle is charged, it will emit a photon of radiation as it swerves. And multiple particles subject to the same gravitational lurch will emit in unison. “You have an amplified effect,” says co-author Cătălina Curceanu of National Institute for Nuclear Physics in Rome.

To test this idea, the researchers built a detector out of a crystal of germanium the size of a coffee cup. They looked for excess x-ray and gamma ray emissions from protons in the germanium nuclei, which create electrical pulses in the material. The scientists chose this portion of the spectrum to maximize the amplification. They then wrapped the crystal in lead and placed it 1.4 kilometers underground in the Gran Sasso National Laboratory in central Italy to shield it from other radiation sources. Over 2 months in 2014 and 2015, they saw 576 photons, close to the 506 expected from naturally occurring radioactivity, they report today in Nature Physics.

By comparison, Penrose’s model predicted 70,000 such photons. “You should see some collapse effect in the germanium experiment, but we don’t,” Curceanu says. That suggests gravity is not, in fact, shaking particles out of their quantum superpositions. (The experiment also constrained, though did not rule out, collapse mechanisms that do not involve gravity.)

To confirm the result, physicists need to engineer those superpositions directly, as opposed to relying on random natural occurrences, says Ivette Fuentes of the University of Southampton: “You should, in principle, be able to make a superposition of massive particles. So let’s do it.” She says her team is working to create clouds of 100 million sodium atoms at a temperature just above absolute zero.

Although Penrose praises the new work, he thinks it’s not really possible to test his version of the model. He says he was never comfortable with particle swerves, because they might cause the universe to gain or lose energy, violating a basic principle of physics. He has spent the pandemic lockdown creating a new and improved model. “It doesn’t produce a heating or radiation,” he says. In that case, gravity might be causing collapse, yet hiding its tracks.

Other factors such as interactions between germanium protons and electrons might also cloak the signal, says theoretical physicist Maaneli Derakhshani of Rutgers University, New Brunswick. All in all, he says, if gravity does cause collapse, the process has to be more complicated than Penrose originally proposed. “One could reasonably argue that … the juice isn’t worth the squeeze.”

 

SOURCE: – Science Magazine

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Bus-sized asteroid to pass close to the earth: NASA – Asia Times

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As interstellar traffic goes, this is a close one.

According to a report in The Independent, an asteroid the size of a mini-bus is set to fly past Earth in the coming hours.

The object, known as 2020 SW, will fly just 13,000 miles above the Earth’s surface on 24 September, NASA has said.

That is closer than the artificial objects that are in orbit around our planet, and power GPS, televisions and more — a close call, indeed.

The object was only discovered on the 18th of September by a NASA-funded project in Arizona, and further observations were able to track its trajectory and rule out any chance that it might collide with Earth, the report said.

After making its pass, it will then fly off to continue its trip around the solar system. It will not come back anywhere near Earth until 2041, when it will be at an even further distance.

The asteroid is thought to be about five to ten meters wide, roughly the size of a “small school bus,” the space agency said. The size is estimated from the brightness of the object, NASA said.

It is not expected to hit Earth — and if you’re reading this, it probably missed us.

This illustration shows a near-Earth asteroid like asteroid 2020 SW traveling through space. Credits: NASA/JPL-Caltech.

However, if it were to hit, it would explode into a fireball as it made its way through the atmosphere, becoming a bright meteor of the kind that is sometimes visible from Earth’s surface, the report said.

Despite repeated suggests that the world is under threat from such asteroids, their visits are fairly common and never pose any great risk to people on Earth.

“There are a large number of tiny asteroids like this one, and several of them approach our planet as close as this several times every year,” said Paul Chodas, director of the Center for Near-Earth Object Studies (CNEOS) at NASA’s Jet Propulsion Laboratory in California.

“In fact, asteroids of this size impact our atmosphere at an average rate of about once every year or two.”

Experts have repeatedly suggested that asteroids more generally could pose more of a threat, and space agencies including NASA conduct “planetary defence” work intended to improve the chances of spotting an asteroid and dealing with any that might possible lead to any danger, the report said.

NASA has been tasked with finding 90% of the near-Earth asteroids that are 140 meters or bigger.

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Such asteroids are far more dangerous than those akin to 2020 SW, since their larger size means they are able to make it through the atmosphere and potentially cause problems when they crash into Earth.

Their larger size also makes them easier to spot, however. There are many more smaller ones of sizes similar to 2020 SW, but their smaller size and lower brightness makes them difficult to see until they get close by.

“The detection capabilities of NASA’s asteroid surveys are continually improving, and we should now expect to find asteroids of this size a couple days before they come near our planet,” said Chodas.

Asia Times Financial is now live. Linking accurate news, insightful analysis and local knowledge with the ATF China Bond 50 Index, the world’s first benchmark cross sector Chinese Bond Indices. Read ATF now. 

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Teenage British activist stages climate protest on Arctic ice floe – SaltWire Network

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By Natalie Thomas

ABOARD ‘ARCTIC SUNRISE’ (Reuters) – Like many of her generation, Mya-Rose Craig feels strongly that adults have failed to take the urgent action needed to tackle global warming and so she has headed to the Arctic Ocean to protest.

Armed with a placard reading ‘Youth Strike for Climate”, the 18-year-old British activist is staging the most northerly protest in a series of youth strikes worldwide.

The strikes, made famous by Swedish campaigner Greta Thunberg, are resuming after a lull caused by the global coronavirus pandemic to draw public attention back to the threat posed by climate change.

“I’m here to… try and make a statement about how temporary this amazing landscape is and how our leaders have to make a decision now in order to save it,” she told Reuters Television as she stood with her placard on the edge of the Arctic sea ice.

“I absolutely think that my generation has always had to think about climate change… which is why as we’ve got older there’s been this massive wave of just this need for change, this demand for change when we realised the grown-ups aren’t going to solve this so we have to do it ourselves.”

Craig, from southwest England, is known as “Birdgirl” online, where her blog chronicling her bird-watching experiences has attracted thousands of followers.

She has travelled hundreds of miles above the Arctic Circle aboard a Greenpeace ship, Arctic Sunrise.

Climate data shows the Arctic is one of the fastest changing ecosystems on the planet, with serious consequences for wildlife from polar bears and seals to plankton and algae, while the melting sea ice contributes to rising sea levels worldwide.

Warming in the Arctic shrank the ice covering the polar ocean this year to its second-lowest extent in four decades, scientists said on Monday.

For Craig, getting to the ice floe involved a two-week quarantine in Germany, followed by a three-week voyage to the edge of the sea ice.

Craig said those who dismiss the youth protests as just a rebellious phase by her generation are wrong, and she wants those in power to stop treating climate change as a low-priority issue, raised only to appease “the lefties in the corner”.

“It’s everything now and it has to be treated like that,” she said.  

(Reporting by Reuters Television; Writing by Gareth Jones; Editing by Janet Lawrence)

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The daring plan to save the Arctic ice with glass – BBC News

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The fear that action to combat climate change has been too slow has led some scientists to test unconventional methods to stem the loss of Arctic sea ice.

One of the most important, yet underappreciated, features of the Arctic sea ice is the ability of its blindingly white surfaces to reflect sunlight. For at least as long as our species has existed, the frozen seas at the top of our world have acted as a massive parasol that helps keep the planet cool and its climate stable.

Yet now, much of that ice is rapidly vanishing. Rising temperatures have locked the Arctic in a self-destructive feedback loop: the warmer it gets, the reflective white ice dissolves into darker, blue water, which absorbs more of the Sun’s warmth rather than reflecting it back into space. Warmer water accelerates melting, which means yet more absorption of heat, which drives further melting – and so on in a vicious cycle that is part of the reason why the Arctic is warming around twice as fast as the rest of the planet. This July, ice cover was as low as it had ever been at that time of the year.

As planet-warming greenhouse gas emissions continue to rise, some have been driven to explore desperate measures. One proposal put forward by the California-based non-profit Arctic Ice Project appears as daring as it is bizarre: to scatter a thin layer of reflective glass powder over parts of the Arctic, in an effort to protect it from the Sun’s rays and help ice grow back. “We’re trying to break [that] feedback loop and start rebuilding,” says engineer Leslie Field, an adjunct lecturer at Stanford University and chief technical officer of the organisation.

The melting of the sea ice has impacts far beyond the Arctic and its inhabitants. It will contribute to rising sea levels, and some say it’s already disrupting weather patterns around the globe. If we lose our protective white shield entirely – which some reckon could happen just decades from now – it could have the same warming effect as another 25 years of fossil fuel emissions at current rates, which would mean more intense droughts, flooding and heat waves. By rebuilding sea ice, Field hopes her approach will also restore its ancient function as a planetary air-conditioner and help counteract the effects of global warming. (Read more about how ice loss in the Arctic affects the rest of the world.)

Tiny powder-like beads could increase the reflectivity of Arctic ice, to reflect more of the Sun’s warmth back into space (Credit: Susan Kramer/Arctic Ice Project)

Many scientists frown upon such technological interventions in Earth’s planetary system, known broadly as “geoengineering”, arguing that fiddling with nature might cause further damage. However, “the utter lack of progress on climate mitigation is really opening up a space for all of these [geoengineering] things to be discussed,” says Emily Cox, who studies climate policy and public attitudes towards geoengineering at the University of Cardiff. That said, the urgency does not erase the uncertainty. “What do you do if something goes wrong… especially in the Arctic, which is already a fairly fragile ecosystem?”

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Field launched the Arctic Ice Project — formerly known as ICE911 — in 2008, soon after watching the climate change documentary An Inconvenient Truth, which convinced her of the urgency of doing something about the melting sea ice. In particular, it’s the fate of old, thick sea ice that worries her the most – the kind that lasts multiple years. This mature ice, dazzlingly white, has a high albedo, meaning it’s extremely good at reflecting sunlight – much more so than the thinner and darker young ice that forms each polar winter only to melt again during the summer. Yet over the past 33 years, that ice has dwindled by a staggering 95%.

What if, Field asked, she could layer a reflective material on top of the young ice to protect it during the summer months? If it had that extra protection, could it rebuild into sturdy multi-year ice, and kick-start a local process of ice regrowth? She settled on silica – or silicon dioxide – which occurs naturally in most sand and is often used to make glass, as the material of choice. She found a manufacturer that turns it into tiny, brightly reflective beads, each one 65 micrometers in diameter – thinner than a human hair, but too large for them to be inhaled and cause lung problems, Field says. The beads are also hollow inside, so they’ll float on water and continue to reflect away sunlight even if the ice begins to melt.

Over the past decade, she and her team have scattered the silica spheres over several lakes and ponds in Canada and the United States, so far with encouraging results. For instance, in a pond in Minnesota, just a few layers of glass powder made young ice 20% more reflective – enough to delay the melting of the ice. By spring, when the ice in an uncovered area of the pond had completely vanished, there was still nearly a foot of ice in the section treated with the glass beads.  

Dark blue water absorbs more of the Sun's rays, accelerating the process of global warming - but bright white ice reflects that radiation away (Credit: Getty Images)

Dark blue water absorbs more of the Sun’s rays, accelerating the process of global warming – but bright white ice reflects that radiation away (Credit: Getty Images)

Field doesn’t want to carpet the Arctic in glass. Instead, she plans on distributing it strategically to protect some particularly fast-melting, vulnerable areas, like the Fram Strait, a thin passage between Greenland and Svalbard. According to results of a climate model she presented last December at the annual meeting of the American Geophysical Union, treating the Fram Strait could lead to large-scale ice regrowth across parts of the Arctic.

Scientists agree that the beads are well-intentioned, but worry about their potential effects on the Arctic ecosystem. If they float around there indefinitely, “it’s just going to clog up the ocean and mess with the ecosystem,” says Cecilia Bitz, an atmospheric scientist at the University of Washington who specialises in Arctic sea ice.

Field argues that the balls are safe because silica is so abundant in nature – indeed, it routinely washes from weathered rocks via rivers into the sea. And according to some safety testing as part of her 2018 study, the beads, when ingested, cause no ill effects in at least two species – sheepshead minnow fish and northern bobwhite birds.

However, some biologists are concerned about the potential effects on the creatures at the base of the Arctic food chain. Depending on how much light the silica beads reflect, they could block sunlight from photosynthesising plankton, such as diatoms, algae that live under the sea ice and around it. Any change in plankton abundance could cascade up the food web and have unpredictable effects on organisms from fish to seals and polar bears, notes Karina Giesbrecht, an ocean chemist and ecologist at Canada’s University of Victoria who has studied the role of silica in Arctic ecosystems.

On top of that, the silica balls are similar in size to diatoms, which are eaten by zooplankton known as copepods, Giesbrecht notes. If the beads sank into the water column, copepods might consume them thinking they are diatoms, without gaining any nutrition. In the worst case, the copepods could starve, with knock-on effects for other members of the Arctic ecosystem.

So far, Field has been using beads that mostly stay afloat (though some inevitably sink each season), and she is planning to test their impact on plankton ecosystems. If there are any harmful effects, she’ll explore ways of tailoring the beads to make them ecologically safer, she says. One option she is considering is whether to tweak their composition such that they dissolve after a period of time. There are many other questions that her team, which is about to undertake further testing in seawater-filled pools in Alaska, will have to answer to convince the world that the approach is safe and effective.

The young, thin Arctic ice is darker and less reflective than the thick, white, old ice – pushing the Arctic into a feedback cycle of warming (Credit: Martha Henriques)

The young, thin Arctic ice is darker and less reflective than the thick, white, old ice – pushing the Arctic into a feedback cycle of warming (Credit: Martha Henriques)

For one, Mark Serreze, a climate scientist who directs the US National Snow and Ice Data Center at the University of Colorado, Boulder, wonders whether they’ll work as intended. “If you put down the silica beads in an area of fast-moving ocean currents, notably the Fram Strait, they will be quickly dispersed,” rendering them ineffective, he says.

The proposal also raises financial questions, like who would foot the approximately $1-5bn (£800m to £4bn) annual bill for making, shipping, testing and distributing the necessary silica beads in the Fram Strait. It may be an eye-watering figure, but it starts to look small next to the estimated $460bn (£360bn) that the United States incurred in extreme weather and climate disasters between 2017 and 2019 alone, Field notes.

Researchers are exploring the feasibility of other geoengineering approaches to save the melting Arctic, but none come without problems. One, for instance, would entail building millions of wind-powered devices to pump water from the deep to the ice surface in order to build up thicker layers of ice – which is energy-intensive and might not be very effective, Bitz says. She and Serreze view such approaches as stop-gap solutions to climate change, in that they only treat single symptoms – in the case of silica dust, temperatures – while doing nothing about the root cause of it. If Field’s strategy works as intended, “that’s wonderful,” Bitz says, “but I know that not emitting CO2 in the first place will work.”

Field agrees that geoengineering is in no way a replacement for reducing carbon emissions. Rather, she sees it as a chance to buy the time needed for world economies to decarbonise and stave off the worst impacts of climate change. The silica beads, she says, are “the backup plan I hoped we’d never need”.

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