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Javier E

What Oppenheimer really knew about an atomic bomb ending the world - The Washington Post - 0 views

www.washingtonpost.com/...oject-history-atomic-bomb-test

world atom bomb end-of-the-world catastrophe physics quantum

shared by Javier E on 28 Jul 23 - No Cached
  • In a chilling, existential, bizarrely comic moment, the new movie “Oppenheimer” revives an old question: Did Manhattan Project scientists think there was even a minute possibility that detonating the first atomic bomb on the remote plains of New Mexico could destroy the world?
  • physicists knew it wouldn’t, long before the Trinity test on July 16, 1945, at the Alamogordo Bombing Range, about 210 miles south of the secret Los Alamos, N.M., laboratory.
  • “This thing has been blown out of proportion over the years,” said Richard Rhodes, author of the Pulitzer Prize-winning book “The Making of the Atomic Bomb.” The question on the scientists’ minds before the test, he said, “wasn’t, ‘Is it going to blow up the world?’ It was, ‘Is it going to work at all?’”
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  • In the movie, one scene has J. Robert Oppenheimer, director of the laboratory, seeking to reassure his boss, Gen. Leslie Groves, on the eve of the test. Upon investigation, Oppenheimer tells him, physicists have concluded that the chances the test detonation will destroy the world are “near zero.” Realizing the news has alarmed, not reassured, the general, Oppenheimer asks, “What do you want from theory alone?”“Zero would be nice,” the general replies.
  • no physicists or historians interviewed for this story recalled coming across any mention of such a conversation between Oppenheimer and the general in the historical record.
  • “Did the actual exchange happen at that moment? No, I don’t think so,” said Alex Wellerstein, an associate professor at Stevens Institute of Technology in Hoboken, N.J., and author of the 2021 book, “Restricted Data: The History of Nuclear Secrecy in the United States.”“But were there discussions like that? I believe so,” he added.
  • At a conference in the summer of 1942, almost a full year before Los Alamos opened, physicist Edward Teller raised the possibility of atomic bombs igniting Earth’s oceans or atmosphere. According to Rhodes’s account, Hans Bethe, who headed the theoretical division at Los Alamos, “didn’t believe it from the first minute” but nonetheless performed the calculations convincing the other physicists that such a disaster was not a reasonable possibility.
  • “I don’t think any physicists seriously worried about it,” said John Preskill, a professor of theoretical physics at California Institute of Technology.
  • Still, the discussions and calculations persisted long after the Trinity test. In 1946, three Manhattan project scientists, including Teller, who would later become known as the father of the hydrogen bomb, wrote a report concluding that the explosive force of the first atomic bomb wasn’t even close to what would be required to trigger a planet-destroying chain reaction in air. The report was not declassified until 1973.
  • A 1979 study by scientists at the University of California’s Lawrence Livermore Laboratory examined the question of whether a nuclear explosion might trigger a runaway reaction in the atmosphere or oceans. In page after page of mathematical equations, the scientists described a complex set of factors that made atmospheric ignition effectively impossible.
  • Probably the easiest to grasp is the fact that, even under the harshest scenarios, far more energy would be lost in the explosion than gained, wiping out any chance to sustain a chain reaction.
  • Dudley’s essay also recounted a story that on the day of the test, “as zero hour approached” Gen. Groves was annoyed to find Manhattan Project physicist and Nobel Prize winner Enrico Fermi making bets with colleagues about whether the bomb would ignite the atmosphere, “and, if so, whether it would destroy only New Mexico ― or the entire world.” (Some experts have suggested Fermi’s actions may have been more of a joke, or an example of gallows humor.)
  • Fascination with this doomsday scenario may stem, at least in part, from a misunderstanding of what physicists mean when they say “near zero.” The branch of physics known as quantum mechanics, which deals with matter and light at the atomic and subatomic scale, does not rule out any possibilities.
  • For example, if a boy tosses a rubber ball at a brick wall, there is an exceedingly remote — but still valid — possibility that instead of watching the ball bounce back, he could see it pass through the wall.
  • Aditi Verma, an assistant professor of nuclear engineering and radiological sciences at the University of Michigan, put it this way: “What a physicist means by ‘near zero’ would be zero to an engineer.”
  • In the 2000s, scientists encountered a similar problem of terminology as they prepared to generate high-speed particle collisions at the Large Hadron Collider in Geneva. Talk surfaced that the activity might generate a black hole that would devour Earth.
  • As outlandish as the notion was to many scientists, the nuclear research organization CERN felt obliged to deal with the fear, noting on its website that “some theories suggest that the formation of tiny ‘quantum’ black holes may be possible. The observation of such an event would be thrilling in terms of our understanding of the Universe; and would be perfectly safe.”
  • In other words, any black hole created by the collider would be far too small to pose any risk to the planet.Scientists say such disaster scenarios are sometimes the price of crossing new thresholds of discovery.
  • “You don’t often talk in certainties,” he said. “You talk in probabilities. If you haven’t done the experiment, you are hesitant to say ‘This is impossible. It will never happen.’ … It was good to think it through.”
  • Rhodes added that he hopes the “Oppenheimer” movie will not lead people to doubt the scientists on the Manhattan Project.“They knew what they were doing,” he said. “They were not feeling around in the dark.”
Javier E

How China's buses shaped the world's EV revolution - BBC Future - 0 views

www.bbc.com/...le-revolution-began-with-buses

china EV buses transport public response climate change history policy

shared by Javier E on 20 Dec 23 - No Cached
  • After around two decades of government support, China now boasts the world's largest market for e-buses, making up more than 95% of global stock. At the end of 2022, China's Ministry of Transport announced that more than three-quarters (77% or 542,600) of all urban buses in the country were "new energy vehicles", a term used by the Chinese government to include pure electric, plug-in hybrids, and fuel cell vehicles powered by alternative fuels such as hydrogen and methanol. In 2022, around 84% of the new energy bus fleet was pure electric.
  • . In 2015, 78% of Chinese urban buses still used diesel or gas, according to the World Resources Institute (WRI). The NGO now estimates that if China follows through on its stated decarbonisation policies, its road transport emissions will peak before 2030.
  • China is also home to some of the world's biggest electric bus manufacturers, such as Yutong, which has been raking up orders across China, Europe and Latin America.
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  • "China has really been at the forefront of success in conversion of all vehicles to electric vehicles, especially buses," says Heather Thompson, chief executive officer of the Institute for Transportation and Development Policy (ITDP), a non-profit focusing on sustainable transport solutions. "The rest of the world is trying to do the same, but I think China is really out ahead."
  • At the time of China's 2001 entry into the World Trade Organisation, the international automotive industry was dominated by European, US and Japanese brands. These companies had spent decades perfecting internal combustion engine technology. To compete, Beijing decided to find a new track for its auto industry: making cars that did not use conventional engines.
  • That same year, the central government launched the so-called "863 plan" for EV research and development. There were numerous practical challenges, however, in the way of mass electrification. Not many manufacturers were making new energy vehicles, buyers were few and there was a lack of charging infrastructure in existence. The answer? Buses.
  • "The Chinese government adopted a very smart strategy," says Liu Daizong, ITDP's East Asia director. "They realised quite early on that they should drive [the EV industry] through electric buses," he notes, since their public service status meant Beijing "could have a strong hand on their electrification".
  • "Bus routes were fixed. This means when an electric bus finished a round, it could return to the depot to recharge," explains Xue Lulu, a mobility manager at the World Resources Institute (WRI) China. The typical daily mileage of a Chinese bus ­– 200km (120 miles) – was a realistic range for battery makers to meet.
  • The following year, the country began its large-scale rollout of new energy buses, with the "Ten Cities and Thousand Vehicles" programme. Over three years, the programme aimed to provide 10 cities with financial subsidies to promote 1,000 public-sector new energy vehicles in each, annually. Its goal was to have 10% new energy vehicles in the country by the end of 2012.
  • Strong policy support from both central and regional governments "gave manufacturers confidence in setting up production lines and stepping up research efforts," says Liu.
  • Together, these strong and consistent government signals encouraged Chinese manufacturers to expand their EV production capacity, bring down costs and improve their technologies. One such company was Build Your Dream, better known as BYD. The Shenzhen-based firm, the world's largest EV maker in 2022, ballooned its business a decade before by supplying electric buses and taxis for China's EV pilot cities.
  • "Back then, most buses used diesel, which was a main source of nitrogen oxides (NOx) emissions," says Xue, referring to the air pollution that smothered Beijing and other Chinese cities in the early 2010s. Yet in 2013, a new plan from central government cited tackling air pollution as one of the reasons for rolling out EVs.
  • This addition proved to be critical: it not only connected EV uptake with people's health, it also indirectly tied the e-bus campaign to local officials' political performance, as the central government would soon hand air-quality targets to all provinces.
  • The years 2013 and 2014 proved to be important for China's EV push. For the first time, the central government made EV purchase subsidies available to individual consumers, not just the public sector, opening the floodgate to private ownership. Additionally, it offered discounted electricity tariffs to bus operators to make sure the cost of running electric buses would be "significantly lower than" that of their oil or gas-powered equivalents.
  • The new economic push, plus local government's determination to battle air pollution, generated great enthusiasm for e-buses. By the end of 2015, the number of EV pilot cities rocketed from 25 to 88. In the same year, the central government set a target of 200,000 new energy buses on the road by 2020 and announced a plan to phase out its subsidies for fossil-fuel-powered buses.
  • To further stimulate the market, many cities devised various local policies on top of national incentives. For example, Shenzhen, a southern city with a population of more than 17 million, encouraged government agencies to work with private companies to create a full range of renting mechanisms for bus operators
  • Different cities' bus operators also designed different charging strategies. "Buses in Shenzhen had bigger batteries, so they normally charged overnight," says Xue, of WRI China. Between 2016 and 2020, Shanghai, another electric bus hub, subsidised the electricity e-buses used -- regardless of the hours of the day -- to give them more flexibility in charging.
  • Generous financial support did lead to problems. In 2016, an EV subsidy fraud shook China, with some bus operators found to have exaggerated the number of e-buses they had purchased. So that same year Beijing shifted its EV subsidy rules so bus operators could only receive financial support when a bus's mileage reached 30,000km (19,000 miles).
  • one year later, the government announced the so-called "dual-credit" policy. This allowed new energy vehicle makers to rake up credits which they could sell for cash to those needing to offset "negative credits" generated from making conventional cars.
  • it wasn't only China's buses that had benefitted.China's e-bus campaign helped create a big and stable market for its wider EV industry, brought down the costs and created economies of scale. In 2009, the year the e-bus campaign was rolled out, the total number of new energy vehicles sold stood at 2,300; by 2022, it was 6.9 million, analysis by Huang Zheng,
  • By 2022, the country had also built the world's largest EV charging network, with 1.8 million public charging stations – or two-thirds of the global total – and 3.4 million private equivalents. This means that on average, there is one charging pillar for every 2.5 of China's 13.1 million new energy vehicles.
  • Cold weather is a problem, too, as it can make a battery's charging time longer and its range shorter. The reason China has not achieved 100% electrification for its buses is its northern regions, which have harsh winters, says Xue.
  • To make e-buses truly "green", they should also be charged with renewable power, Wang says. But last year coal power still accounted for 58.4% of China's energy mix, according to the China Electricity Council, a trade body..
  • Globally, however, China is now in a league of its own in uptake of e-buses. By 2018, about 421,000 of the world's 425,000 electric buses were located in China; Europe had about 2,250 and the US owned around 300. A
  • But earlier this year, the European Commission announced a zero-emission target for all new city buses by 2030. And some countries are increasing their overall funding for the transition.
  • In 2020, the European Commission approved Germany's plan to double its aid for e-buses to €650m (£558m/$707m), then again in 2021 to €1.25 billion euros (£1.07m/$1.3bn). And the UK, which last year had the largest electric bus fleet in Europe with 2,226 pure electric and hybrid buses, has announced another £129m ($164m) to help bus operators buy zero-emissions fleets.
  • Countries have thus responded to China's manufacturing lead in divergent ways. "While the US has opted for a more competitive angle by fostering its own e-bus production, regions like Latin America are more open to trade with China due to a more friendly trading setup through [China's] Belt and Road Initiative,"
  • In order to avoid direct competition from Chinese manufacturers, the US has come up with a "school-bus strategy", says Liu. The Chinese don't make the iconic yellow vehicles, so this could ignite American e-bus manufacturing and create a local industry chain, he suggests. Backed by the US Environmental Protection Agency's $5bn (£3.9bn) Clean School Bus Programme, the national effort has so far committed to providing 5,982 buses.
  • In contrast, many Latin American cities, such as the Colombian capital of Bogota and the Chilean capital of Santiago, are greening their traditional bus sectors with the help of Chinese manufacturers, who are the largest providers to the region. In 2020, Chile became the country that had the most Chinese e-buses outside of China, and this year Santiago's public transport operator announced it has ordered 1,022 e-buses from Beijing-based Foton Motor, the biggest overseas deal the firm had received.
  • Chinese manufacturers are likely to receive a lot more orders from Chile and its neighbours in this decade. According to latest research by the global C40 Cities network, the number of electric buses in 32 Latin American cities is expected to increase by more than seven times by 2030, representing an investment opportunity of over $11.3bn (£8.9bn)
  • In June 2023, BloombergNEF forecast half of the world's buses to be entirely battery-powered by 2032, a decade ahead of cars. And by 2026, 36% and 24% of municipal bus sales in Europe and the US, respectively, are expected to be EVs as they begin to catch up with China
  • To meet the global climate goals set by the Paris Agreement, simply switching the world's existing bus fleets might not be enough. According to ITDP, the cumulative greenhouse gas emissions from urban passenger transport globally must stay below the equivalent of 66 gigatonnes CO2 between 2020 and 2050 for the world to meet the 1.5C temperature goal. This emissions limit will only be possible when the world not only adopts electric buses, but goes through a broader shift away from private transport
  • "We can't just focus on [replacing] the buses that exist, we need to actually get many, many more buses on the streets," Thompson adds. She and her team estimate that the world would need about 10 million more buses through 2030, and 46 million more buses cumulatively through 2050, to make public transport good enough to have a shot at achieving the Paris Agreement. And all those buses will need to be electric.
  • In China therefore, even though EVs are being sold faster than ever, its central government has instructed cities to encourage public transport use, as well as walking and riding bikes.
  • In Wang's hometown, meanwhile, which has just over three million residents, the local government has gone one step further and made all bus rides free. All citizens need to do is to swipe an app, with no charge, to get onto the bus. "My aunt loves taking buses now," says Wang. "She says it is so convenient."
Javier E

How Bad Are Ultraprocessed Foods, Really? - The New York Times - 0 views

www.nytimes.com/...ssed-foods-harmful-health.html

UPFs food diet processed health risks history culture

shared by Javier E on 07 May 24 - No Cached
  • scientists have found associations between UPFs and a range of health conditions, including heart disease, Type 2 diabetes, obesity, gastrointestinal diseases and depression, as well as earlier death.
  • That’s concerning, experts say, since ultraprocessed foods have become a major part of people’s diets worldwide. They account for 67 percent of the calories consumed by children and teenagers in the United States
  • What are ultraprocessed foods, exactly? And how strong is the evidence that they’re harmful? We asked experts to answer these
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  • Dr. Monteiro and his colleagues developed a food classification system called Nova, named after the Portuguese and Latin words for “new.” It has since been adopted by researchers across the world.
  • Unprocessed or minimally processed foods, like fresh or frozen fruits and vegetables, beans, lentils, meat, poultry, fish, eggs, milk, plain yogurt, rice, pasta, corn meal, flour, coffee, tea and herbs and spices.
  • Processed culinary ingredients, such as cooking oils, butter, sugar, honey, vinegar and salt.
  • If you look at the ingredient list and you see things that you wouldn’t use in home cooking, then that’s probably an ultraprocessed food,”
  • his group includes freshly baked bread, most cheeses and canned vegetables, beans and fish. These foods may contain preservatives that extend shelf life.
  • Ultraprocessed foods made using industrial methods and ingredients you wouldn’t typically find in grocery stores — like high-fructose corn syrup, hydrogenated oils and concentrated proteins like soy isolate.
  • They often contain additives like flavorings, colorings or emulsifiers to make them appear more attractive and palatable.
  • Think sodas and energy drinks, chips, candies, flavored yogurts, margarine, chicken nuggets, hot dogs, sausages, lunch meats, boxed macaroni and cheese, infant formulas and most packaged breads, plant milks, meat substitutes and breakfast cereals.
  • Processed foods made by combining foods from Category 1 with the ingredients of Category 2 and preserving or modifying them with relatively simple methods like canning, bottling, fermentation and baking
  • That has led to debate among nutrition experts about whether it’s useful for describing the healthfulness of a food, partly since many UPFs — like whole grain breads, flavored yogurts and infant formulas — can provide valuable nutrients
  • Most research linking UPFs to poor health is based on observational studies, in which researchers ask people about their diets and then track their health over many years.
  • Why might UPFs be harmful?
  • In a large review of studies that was published in 2024, scientists reported that consuming UPFs was associated with 32 health problems, with the most convincing evidence for heart disease-related deaths, Type 2 diabetes and common mental health issues like anxiety and depression.
  • Such studies are valuable, because they can look at large groups of people — the 2024 review included results from nearly 10 million — over the many years it can take for chronic health conditions to develop
  • She added that the consistency of the link between UPFs and health issues increased her confidence that there was a real problem with the foods.
  • But the observational studies also have limitations,
  • It’s true that there is a correlation between these foods and chronic diseases, she said, but that doesn’t mean that UPFs directly cause poor health.
  • Dr. O’Connor questioned whether it’s helpful to group such “starkly different” foods — like Twinkies and breakfast cereals — into one category. Certain types of ultraprocessed foods, like sodas and processed meats, are more clearly harmful than others
  • UPFs like flavored yogurts and whole grain breads, on the other hand, have been associated with a reduced risk of developing Type 2 diabetes.
  • Clinical trials are needed to test if UPFs directly cause health problems, Dr. O’Connor said. Only one such study, which was small and had some limitations, has been done, s
  • In that study, published in 2019, 20 adults with a range of body sizes lived in a research hospital at the National Institutes of Health for four weeks. For two weeks, they ate mainly unprocessed or minimally processed foods, and for another two weeks, they ate mainly UPFs. The diets had similar amounts of calories and nutrients, and the participants could eat as much as they wanted at each meal.
  • During their two weeks on the ultraprocessed diet, participants gained an average of two pounds and consumed about 500 calories more per day than they did on the unprocessed diet
  • During their time on the unprocessed diet, they lost about two pounds.
  • That finding might help explain the link between UPFs, obesity and other metabolic conditions
  • The Nova system notably doesn’t classify foods based on nutrients like fat, fiber, vitamins or minerals. It’s “agnostic to nutrition,”
  • There are many “strong opinions” about why ultraprocessed foods are unhealthy, Dr. Hall said. “But there’s actually not a lot of rigorous science” on what those mechanisms are
  • Because UPFs are often cheap, convenient and accessible, they’re probably displacing healthier foods from our diets
  • the foods could be having more direct effects on health. They can be easy to overeat — maybe because they contain hard-to-resist combinations of carbohydrates, sugars, fats and salt, are high-calorie and easy to chew
  • It’s also possible that resulting blood sugar spikes may damage arteries or ramp up inflammation, or that certain food additives or chemicals may interfere with hormones, cause a “leaky” intestine or disrupt the gut microbiome.
  • Researchers, including Dr. Hall and Dr. Davy, are beginning to conduct small clinical trials that will test some of these theories.
  • most researchers think there are various ways the foods are causing harm. “Rarely in nutrition is there a single factor that fully explains the relationship between foods and some health outcome,”
  • In 2014, Dr. Monteiro helped write new dietary guidelines for Brazil that advised people to avoid ultraprocessed foods.
  • Other countries like Mexico, Israel and Canada have also explicitly recommended avoiding or limiting UPFs or “highly processed foods.”
  • The U.S. dietary guidelines contain no such advice, but an advisory committee is currently looking into the evidence on how UPFs may affect weight gain, which could influence the 2025 guidelines.
  • It’s difficult to know what to do about UPFs in the United States, where so much food is already ultraprocessed and people with lower incomes can be especially dependent on them,
  • “At the end of the day, they are an important source of food, and food is food,” Dr. Mattei added. “We really cannot vilify them,”
  • While research continues, expert opinions differ on how people should approach UPFs.
  • the safest course is to avoid them altogether
  • to swap flavored yogurt for plain yogurt with fruit, for example, or to buy a fresh loaf from a local bakery instead of packaged bread, if you can afford to do so
  • Dr. Vadiveloo suggested a more moderate strategy, focusing on limiting UPFs that don’t provide valuable nutrients, like soda and cookies
  • She also recommended eating more fruits, vegetables, whole grains (ultraprocessed or not), legumes, nuts and seeds.
  • Cook at home as much as you can, using minimally processed foods
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