I'll make it extremely easy for you @astro Provide some actual solid evidence of any sort that human emissions control the planet's temperature. I bet you find as much actual evidence as you'll find for the flat earth "theory" If you abstain, then I'll assume you agree that there is in fact no no explicit evidence at all, none, nada, nil
NEWS PARTICLE PHYSICS The inside of a proton endures more pressure than anything else we’ve seen For the first time, scientists used experimental data to estimate the pressure inside a proton BY EMILY CONOVER 1:18PM, MAY 16, 2018 please log in to view this image FEELING THE PRESSURE Extreme pressures are found within the proton, scientists report. The proton contains three particles called quarks (illustrated) as well as gluons, which hold the particle together. y the protons: Those little particles are under a lot of pressure. Protons’ innards are squeezed harder than any other substance we have measured, a new study finds. “It’s really the highest pressure we have ever seen,” says physicist Volker Burkert, a coauthor of the study, published in the May 17 Nature. Protons break the pressure recordset by neutron stars, the incredibly dense dead stars that can form when a massive star explodes and its core collapses, squeezing more mass than the sun’s into a remnant the size of a city. The pressure in the proton’s center averages a million trillion trillion times the strength of Earth’s atmospheric pressure, report Burkert and colleagues, from Thomas Jefferson National Accelerator Facility in Newport News, Va. That’s around 10 times the pressure found inside a neutron star. Previously, scientists had theoretically predicted that such pressures might occur inside protons, but the new result is the first experimental proton pressure gauge. In proton research, the particle’s internal pressure distribution has been a largely unexplored frontier, even though pressure is one of the proton’s fundamental properties. “It’s as important as electric charge or mass,” says physicist Peter Schweitzer of the University of Connecticut in Storrs, but was unknown until now. Protons are made up of smaller particles including quarks, which are electrically charged, and gluons, which transmit the strong nuclear force that holds protons together (SN: 4/29/17, p. 22). In the center of this ball of particles, Burkert and colleagues report, an intense pressure pushes outward. But this record-breaking outward force is kept in check by an inward pressure from the outer regions of the particle. This pressure pattern parallels what happens in much larger objects: “In some sense, it’s looking like a star,” says physicist Oleg Teryaev of the Joint Institute for Nuclear Research in Dubna, Russia. Stars also have pressures that push outward in their centers, which counteract the inward pull of gravity. Protons are held together by the strong force, just as stars are held together by gravity. But the tiny protons are a different beast. So “it’s natural, but it’s not completely trivial” that the two objects would have similarities pressure-wise, Teryaev says. please log in to view this image TIGHT SQUEEZE To determine the pressure inside a proton, scientists used data from CLAS detector (shown), in which electrons are scattered off of protons. JEFFERSON LAB/FLICKR ( CC BY-NC 2.0) To quantify the proton’s squeeze, the researchers used data from a particle detector known as CLAS, short for the Continuous Electron Beam Accelerator Facility Large Acceptance Spectrometer, located at Jefferson Lab. In experiments with CLAS, scientists shot electrons at liquid hydrogen, a plentiful source of protons, and watched what happened as electrons interacted with the protons’ constituents and ricocheted away. The new measurement is based on data from 2015 that was analyzed for the first time using a technique that could tease out the proton’s pressure. The experiment, however, studied the quarks in protons, but not gluons, because the energy of the electrons — 6 billion electron volts — was not enough for the electrons to fully probe the protons. To make their pressure estimate, the researchers assumed that the gluons’ pressure contribution was the same as the quarks’, which is in line with some theoretical predictions. Future particle accelerators, such as the planned Electron-Ion Collider, would allow for gauging the gluons’ contribution to provide a better estimate of the crushing pressure protons endure.
Professor Peter Ridd. Challenges bad science on the Great barrier Reef, gets fired, because that bad science brought in millions of government funding to his James Cook University. if Institutions claim doom and get millions in funding to investigate non problems politicians back, it easily explains the "consensus" in keeping the financial tap on. The corruption of science is largely wholesale these days. Peter Ridd On 2 May, 2018, I received a letter from James Cook University (JCU) terminating my employment. JCU have sacked me because I dared to fight the university and speak the truth about science and the Great Barrier Reef. Shortly after I went public with the GoFundMe campaign to which you donated in February the university presented me with a further set of misconduct allegations, which alleged that I acted inappropriately by talking about the case and have now ended my employment. I will be fighting their employment termination, alongside the original 25 charges behind JCU’s ‘final censure’ last year. As a consequence of the sacking, and the new misconduct allegations, my legal costs have substantially increased. JCU appears to be willing to spend their near unlimited legal resources fighting me. In the name of honesty and truth in science, we must fight back. We have an excellent legal team and are confident that we can win the legal case. I feel extremely indebted to all those who have given so generously. I was blown away by the number of people who supported me, and I had hoped that more funding would not be necessary. Sadly, however circumstances have changed. I have contributed another $15000 of my own money, in addition to the $24000k I have already spent. However, based on the growing complexity of the case, we will need to raise an additional $159000. It is a bit frightening, but we have reopened the GoFundMe site to receive more donations. You have already contributed generously so all I ask of you is to help spread the word to expand the number of people who are helping. I know there were many who were unable to donate the first time – including my own Mum – due to the speed we reached the original target of $95K. For additional background on all the new allegations from JCU, I have uploaded all the documentation so that you can judge JCU’s allegations for yourself if you wish. https://platogbr.wordpress.com/fired-details/ In summary, JCU (1) objects to my criticism of the earlier allegations; (2) criticised my involvement with the Institute of Public Affairs; and (3) objects to me not remaining silent. The facts of the matter are simple: (1) the earlier allegations were an unreasonable infringement on my academic freedom, I was well within my rights to criticise JCU; (2) I have never been paid by the IPA, other than some initial support for my legal case and reimbursement for flights and hotels related to speaking arrangements which is normal academic practice; and (3) I am well within my rights, as stated by my employment agreement, to speak publicly about disciplinary proceedings. Thanks, Peter
Dark matter particles elude scientists in the biggest search of its kind But XENON1T’s results narrow where to search for hypothetical particles called WIMPS BY EMILY CONOVER 5:00AM, MAY 28, 2018 please log in to view this image WIMPING OUT The XENON1T experiment (contained inside the large tank above, at left) reports no hint of any interactions from particles of dark matter within, despite a yearlong search. The largest particle detector of its kind has failed to turn up any hints of dark matter, despite searching for about a year. Known as XENON1T, the experiment is designed to detect elusive dark matter particles, which are thought to make up most of the matter in the cosmos. Physicists don’t know what dark matter is. One of the most popular explanations is a particle called a WIMP, short for weakly interacting massive particle. XENON1T searches for WIMPs crashing into atomic nuclei in 1,300 kilograms of chilled liquid xenon. But XENON1T saw no such collisions. The particles’ absence further winnowed down their possible hiding places by placing new limits on how frequently WIMPs can interact with nuclei depending on their mass. Researchers describe the results May 28 in two talks, one at Gran Sasso National Laboratory in Italy, where XENON1T is located, and the other at the European particle physics lab CERN in Geneva. XENON1T had previously reported no hint of WIMPs using about a month’s worth of data (SN: 9/30/17, p. 17). The new study, however, was highly anticipated by physicists, as the longer search provided a better chance for spotting WIMPs. As the WIMP window narrows, scientists are preparing to rev up the search, creating larger, more sensitive WIMP detectors, and moving on to search for other possible dark matter particles, such as axions (SN Online: 4/9/18).
One for Sisu The Chicxulub asteroid impact might have set off 100,000 years of global warming The hit caused the release of carbon dioxide, driving temperatures to rise, researchers say BY LAUREL HAMERS 3:13PM, MAY 24, 2018 please log in to view this image START FROM SCRATCH The asteroid that hit Earth about 66 million years ago, wiping out most of the planet’s life, also spewed carbon dioxide into the air and heated up the climate for millennia, a new study suggests. After a giant asteroid hit Earth about 66 million years ago, the planet’s climate went on a roller coaster ride. The space rock’s impact set off tsunamis and wildfires before climate-chilling clouds of sulfur gas engulfed the planet for decades, wiping out most life (SN: 11/25/17, p. 14). As these clouds dissipated, billions of tons of carbon dioxide, which spewed into the atmosphere when the asteroid hit, fueled roughly 100,000 years of global warming, new data suggest. Analyzing fossilized fish bits hints that the influx of the greenhouse gas raised the temperature of the ocean on average by 5 degrees Celsius, scientists report online May 24 in Science. It’s not surprising that the climate heated up after the collision, which left a 200-kilometer-wide crater centered around what’s now Chicxulub, Mexico, says Johan Vellekoop, a geologist at KU Leuven in Belgium. But finding evidence to back up the warming claim has been challenging. A common way to estimate past temperatures on Earth is to measure the proportion of heavier to lighter forms of oxygen in the carbonate shells left behind by dead invertebrates. Animals incorporate different oxygen forms into shells, teeth and bones at different rates depending on temperature. But carbonate fossils from around the time of the impact aren’t well enough preserved to be a reliable thermometer. Instead, paleogeologist Ken MacLeod of the University of Missouri in Columbia and colleagues analyzed those same types of oxygen ratios in a crushed jumble of fish bones, teeth and scales — a different way to measure past temperatures. The team collected sediment samples from a section of rock in what’s now El Kef, Tunisia, that records the transition between the periods before and after the impact in its layers. (Samples from 2 meters of rock laid down before the impact and 6.6 meters laid down after the strike recorded almost 250,000 years of geologic history.) Back in the lab, the researchers spent hours peering through microscopes to sort out glassy, amber fish teeth and mineralized scales and measure the oxygen content within them. Hidden gems Bits of fossilized fish, painstakingly sorted from sediment, give new clues to Earth’s climate after the Chicxulub impact. The debris is made up of bones (top left), teeth (top right) and scales (bottom right). A jumbled mix of pieces is also shown (bottom left). please log in to view this image K. MACLEOD AND PAGE QUINTON The ratio of heavier oxygen to lighter decreased by about 1 percent in the fish bits collected after the impact compared with those pieces from before the impact, the team found. That change translates to an increase in seawater temperature of about 5 degrees Celsius — a substantial amount. The elevated temperatures persisted for about 100,000 years before the planet cooled down again, an analysis of fish debris collected from different levels of rock showed. While the study looked only at ocean temperature, air temperature would probably reflect that increase, too, MacLeod says. “It’s a pretty robust result,” says Clay Tabor, a climate scientist at the University of Connecticut in Hartford. But getting similar results from sites elsewhere in the world would boost the case that this was a global effect and not a local fluke, he says. The story is far from over, MacLeod agrees. It’s not clear how long after the impact the warming began, for instance. His team hopes to analyze fish debris from other sites that might reveal finer-scale changes in temperature.
NEWS PARTICLE PHYSICS Mysterious neutrino surplus hints at the existence of new particles The MiniBooNE experiment found more interactions of the subatomic particles than expected BY EMILY CONOVER 3:45PM, JUNE 1, 2018 please log in to view this image NEW NEUTRINO? The particle detector MiniBooNE (shown) observed an excess of neutrino interactions, which may hint at the existence of a new type of neutrino. FERMILAB Pip-squeak particles called neutrinos are dishing out more than scientists had bargained for. A particle detector has spotted a puzzling abundance of the lightweight subatomic particles and their antimatter partners, antineutrinos, physicists report May 30 at arXiv.org. The finding mirrors a neutrino excess found more than two decades ago. And that match has researchers wondering if a new type of particle called a sterile neutrino — one even more shadowy than the famously elusive ordinary neutrinos — might be at large. Such a particle, if it exists, would transform the foundations of particle physics and could help solve cosmic puzzles like the existence of dark matter, an unidentified inert substance that makes up the preponderance of the matter in the universe. The new study was conducted with a neutrino detector called MiniBooNE, while the previous neutrino excess was found with a different apparatus, the Liquid Scintillator Neutrino Detector, which operated in the 1990s at Los Alamos National Laboratory in New Mexico. “We have two very different detectors … and we have the same results,” says MiniBooNE physicist En-Chuan Huang of Los Alamos National Laboratory. Hints of excess neutrinos have shown up in earlier results from MiniBooNE, which has been operating since 2002 at Fermilab in Batavia, Ill. But the new research includes twice as much data, making the neutrino deluge too strong to ignore. please log in to view this image SEE THE LIGHT The MiniBooNE detector, a tank containing over 800 tons of mineral oil outfitted with light sensors (shown), looks for flashes produced by the interactions of subatomic particles called electron neutrinos. FERMILAB Still, some physicists are questioning whether the excess signals are really from neutrinos. “The events … are real. The question is, what are they?” says neutrino physicist Jonathan Link of Virginia Tech in Blacksburg. The apparent neutrino surplus could be a red herring: Other particles can interact in ways that mimic neutrinos. Neutrinos come in three known types: electron neutrinos, muon neutrinos and tau neutrinos, named after the electron and its two heavier cousins, muons and taus. Weirdly, neutrinos can morph from one type to another: A particle born as a muon neutrino might later be detected as an electron neutrino (SN: 1/26/13, p. 18). In the new experiment, scientists blasted muon neutrinos and antineutrinos at MiniBooNE, and looked for particles that had morphed into the electron type. Using a large tank of mineral oil outfitted with sensitive light detectors, MiniBooNE looked for small flashes of light produced in electron neutrino and antineutrino interactions. The researchers saw 2,437 interactions, about 460 more than predicted. That excess potentially hints at the existence of sterile neutrinos, which could alter the way neutrinos shift from one type to another, causing more muon neutrinos to morph into the electron type than otherwise expected. While ordinary neutrinos rarely interact with matter, sterile neutrinos wouldn’t interact at all, except via gravity. Sterile neutrinos have been proposed as a possible candidate for what makes up dark matter. But to explain the MiniBooNE results, the sterile neutrinos would have to be relatively lightweight — too puny to explain dark matter. Still, the existence of light sterile neutrinos might suggest heavier ones are out there, too, says cosmologist Kevork Abazajian of the University of California, Irvine. “Sometimes people say they're like cockroaches: If you have one [type of] sterile neutrino, you have many. Other neutrino misbehavior has shown up in experiments that measure electron antineutrinos produced in nuclear reactors. These experiments see fewer interactions than expected, a result that could also be explained by a sterile neutrino (SN: 3/19/16, p. 14). But there’s an inconsistency: A sterile neutrino should cause a deficit of muon neutrinos in other experiments, but that hasn’t been seen. That means the explanation is likely more complicated than there being a single type of sterile neutrino. It’s not yet clear how the various results from different neutrino experiments fit together. For now, the new study has physicists puzzled. “I actually don’t know what to make of it,” says neutrino physicist Kate Scholberg of Duke University. But theoretical physicists, she says, “will chew on this like crazy.”
https://www.cbsnews.com/news/alan-bean-astronaut-who-walked-on-the-moon-dies-at-86/ Godspeed Alan Bean.
NEWS PARTICLE PHYSICS, ASTRONOMY If real, dark fusion could help demystify this physics puzzle The idea could reveal why galaxies have dark matter cores of even densities BY EMILY CONOVER 9:00AM, JUNE 6, 2018 please log in to view this image DARK CLOUDS Galaxies and galaxy clusters are surrounded by dark matter (illustrated in blue over an image of the cluster Abell 2744; red indicates gas). Dark matter particles may undergo a process called dark fusion, one scientist suggests. Fusion may have a dark side. A shadowy hypothetical process called “dark fusion” could be occurring throughout the cosmos, a new study suggests. The standard type of fusion occurs when two atomic nuclei unite to form a new element, releasing energy in the process. “This is why the sun shines,” says physicist Sam McDermott of Fermilab in Batavia, Ill. A similar process — dark fusion — could occur with particles of dark matter, McDermott suggests in a paper published in the June 1 Physical Review Letters. If the idea is correct, the proposed phenomenon may help physicists resolve a puzzle related to dark matter — a poorly understood substance believed to bulk up the mass of galaxies. Without dark matter, scientists can’t explain how galaxies’ stars move the way they do. But some of the quirks of how dark matter is distributed within galaxy centers remain a mystery. Dark matter is thought to be composed of reclusive particles that don’t interact much with ordinary matter — the stuff that makes up stars, planets and living creatures. That introverted nature is what makes the enigmatic particles so hard to detect. But dark matter may not be totally antisocial (SN: 3/3/18, p. 8). “Why wouldn’t the dark matter particles interact with each other? There’s really no good reason to say they wouldn’t,” says physicist Manoj Kaplinghat of the University of California, Irvine. Scientists have suggested that dark matter particles might ricochet off one another. But the new study goes a step further, proposing that pairs of dark matter particles could fuse, forming other unknown types of dark matter particles in the process. Such dark fusion could help explain why dark matter near the centers of galaxies is more evenly distributed than expected. In computer simulations of galaxy formation, the density of dark matter rises sharply toward a cusp in the center of a galaxy. But in reality, galaxies have a core evenly filled with dark matter. Those simulations assume dark matter particles don’t interact with one another. But dark fusion could change how the particles behave, giving them energy that would provide the oomph necessary to escape entrapment in a galaxy’s dense cusp, thereby producing an evenly filled core. “You can kick [particles] around through this interaction, so that’s kind of cool,” says physicist Annika Peter of the Ohio State University in Columbus. But, she says, dark fusion might end up kicking the particles out of the galaxy entirely, which wouldn’t mesh with expectations: The particles could escape the halo of dark matter that scientists believe surrounds each galaxy. For now, if fusion does have an alter ego, scientists remain in the dark.
Einstein’s general relativity reigns supreme, even on a galactic scale Astronomers tried and failed to find a flaw in the famous physicist’s theory of gravity BY EMILY CONOVER 2:00PM, JUNE 21, 2018 please log in to view this image FLYING COLORS Einstein’s theory of gravity has passed another test, based on the galaxy ESO 325-G004 (bright spot at center right). The experiment is the most precise check of general relativity on a galactic scale. NASA, ESA, HUBBLE HERITAGE TEAM/STSCI AND AURA Email Twitter Facebook Reddit Google+ SPONSOR MESSAGE Chalk up another win for Einstein’s seemingly invincible theory of gravity. A new study shows that the theory of general relativity holds true even over vast distances. General relativity prevailed within a region spanning a galactic distance of about 6,500 light-years, scientists report in the June 22 Science. Previously, researchers have precisely tested the theory by studying its effects on the solar system (SN Online: 8/15/17). But experiments on larger scales are more difficult. The new test is the most precise one yet across such great distances. According to general relativity, the force of gravity is the result of matter warping spacetime (SN: 10/17/15, p. 16). In the study, the team looked at how light from a faraway galaxy was bent by that warping as the light passed by an intervening galaxy while traveling toward Earth. The closer galaxy, known as ESO 325-G004 and located about 450 million light-years away from Earth, distorted the image of the distant galaxy into a ring, like a cosmic version of a fun house mirror (SN: 10/17/15, p. 24). Using the observations of distorted light, the scientists estimated ESO 325-G004’s mass. Then they compared that measurement with a second mass estimate based on how stars in the galaxy zipped around and hence how much mass was tugging on them. The two measurements agreed, validating Einstein’s theory. The result challenges certain proposed tweaks to general relativity, which predict that the masses won’t match up. For physicists, such tweaks are appealing because they might eliminate the need for dark energy, a mysterious pressure thought to be behind the universe’s accelerating expansion. But so far, Einstein still reigns supreme. Nice ring to it Light from a distant galaxy is shaped into a ring (inset) by the warping of spacetime caused by an intervening galaxy named ESO 325-G004 (bright spot). The ring becomes visible when bright light from the galaxy itself is removed from the image. please log in to view this image T.E. COLLETT ET AL/SCIENCE 2018 What a man he really was.
It's staggering, and people eulogise over Hawking. Einstein didn't even get his Nobel for general relativity. He got it for the photo-electric effect
just an acknowledgement. The reality of it is saying a caveman sat down in his cave, shut his eyes and imagines a steam engine or an aeroplane and how it would all work. He had not computers to do calculations, no colliders, no concepts of subatomic particles. He just imagined thought experiments
Well my daughter is now officially a published scientist having assisted with the attached published research, bit of easy reading for everyone. She still has a year to go of her Masters degree as well. Very proud Dad www.sciencedirect.com/science/article/pii/S1568163718301247?_rdoc=1&_fmt=high&_origin=gateway&_docanchor=&md5=b8429449ccfc9c30159a5f9aeaa92ffb
Nice one , mate, and many congrats to your daughter. I'm meting my MA daughter for tea on the way home
By way of a complete coincidence FEATURE BIOMEDICINE, NEUROSCIENCE, MENTAL HEALTH The brain may clean out Alzheimer’s plaques during sleep If sleep deprivation puts garbage removal on the fritz, the memory-robbing disease may develop BY LAURA BEIL 6:00AM, JULY 15, 2018 please log in to view this image THE CLEAN CYCLE Lack of sleep may contribute to Alzheimer’s disease by robbing the brain of the time it needs to wash away sticky proteins. MICHAEL MORGENSTERN Scentist Barbara Bendlin studies the brain as Alzheimer’s disease develops. When she goes home, she tries to leave her work in the lab. But one recent research project has crossed into her personal life: She now takes sleep much more seriously. Bendlin works at the University of Wisconsin–Madison, home to the Wisconsin Registry for Alzheimer’s Prevention, a study of more than 1,500 people who were ages 40 to 65 when they signed up. Members of the registry did not have symptoms of dementia when they volunteered, but more than 70 percent had a family history of Alzheimer’s disease. Since 2001, participants have been tested regularly for memory loss and other signs of the disease, such as the presence of amyloid-beta, a protein fragment that can clump into sticky plaques in the brain. Those plaques are a hallmark of Alzheimer’s, the most common form of dementia. Each person also fills out lengthy questionnaires about their lives in the hopes that one day the information will offer clues to the disease. Among the inquiries: How tired are you? Some answers to the sleep questions have been eye-opening. Bendlin and her colleagues identified 98 people from the registry who recorded their sleep quality and had brain scans. Those who slept badly — measured by such things as being tired during the day — tended to have more A-beta plaques visible on brain imaging, the researchers reported in 2015 in Neurobiology of Aging. In a different subgroup of 101 people willing to have a spinal tap, poor sleep was associated with biological markers of Alzheimer’s in the spinal fluid, Bendlin’s team reported last year in Neurology. The markers included some related to A-beta plaques, as well as inflammation and the protein tau, which appears in higher levels in the brains of people with Alzheimer’s. Bendlin’s studies are part of a modest but growing body of research suggesting that a sleep-deprived brain might be more vulnerable to Alzheimer’s disease. In animal studies, levels of plaque-forming A-beta plummet during sleep. Other research suggests that a snoozing brain runs the “clean cycle” to remove the day’s metabolic debris — notably A-beta — an action that might protect against the disease. Even one sleepless night appears to leave behind an excess of the troublesome protein fragment (SN Online: 7/10/17). But while the new research is compelling, plenty of gaps remain. There’s not enough evidence yet to know the degree to which sleep might make a difference in the disease, and study results are not consistent. A 2017 analysis combined results of 27 studies that looked at the relationship between sleep and cognitive problems, including Alzheimer’s. Overall, poor sleepers appeared to have about a 68 percent higher risk of these disorders than those who were rested, researchers reported last year in Sleep. That said, most studies have a chicken-and-egg problem. Alzheimer’s is known to cause difficulty sleeping. If Alzheimer’s both affects sleep and is affected by it, which comes first? For now, the direction and the strength of the cause-and-effect arrow remain unclear. But approximately one-third of U.S. adults are considered sleep deprived (getting less than seven hours of sleep a night) and Alzheimer’s is expected to strike almost 14 million U.S. adults by 2050 (5.7 million have the disease today). The research has the potential to make a big difference. Dream weavers It would be easier to understand sleep deprivation if scientists had a better handle on sleep itself. The brain appears to use sleep to consolidate and process memories (SN: 6/11/16, p. 15) and to catalog thoughts from the day. But that can’t be all. Even the simplest animals need to sleep. Flies and worms sleep. But mammals appear to be particularly dependent on sleep — even if some, like elephants and giraffes, hardly nod off at all (SN: 4/1/17, p. 10). If rats are forced to stay awake, they die in about a month, sometimes within days. And the bodies and brains of mice change when they are kept awake, says neurologist David Holtzman of Washington University School of Medicine in St. Louis. In one landmark experiment, Holtzman toyed with mice’s sleep right when the animals’ brain would normally begin to clear A-beta. Compared with well-rested mice, sleep-deprived animals developed more than two times as many amyloid plaques over about a month, Holtzman says. Losing sleep Alzheimer’s disease disrupts sleep. And disrupted sleep itself might encourage Alzheimer’s by allowing buildup of amyloid-beta, or A-beta, which is thought to lead to the death of neurons. This cycle of sleep deprivation can also affect levels of the hormone melatonin, which helps the body to sleep, and can interfere with metabolism, a disruption that is also a risk factor for Alzheimer’s. please log in to view this image Source: Y. Saeed and S.M. Abbott/Current Neurology and Neuroscience Reports 2017 He thinks Alzheimer’s disease is a kind of garbage collection problem. As nerve cells, or neurons, take care of business, they tend to leave their trash lying around. They throw away A-beta, which is a leftover remnant of a larger protein that is thought to form connections between neurons in the developing brain, but whose role in adults is still being studied. The body usually clears away A-beta. But sometimes, especially when cheated on sleep, the brain doesn’t get the chance to mop up all the A-beta that the neurons produce, according to a developing consensus. A-beta starts to collect in the small seams between cells of the brain, like litter in the gutter. If A-beta piles up too much, it can accumulate into plaques that are thought to eventually lead to other problems such as inflammation and the buildup of tau, which appears to destroy neurons and lead to Alzheimer’s disease. About a decade ago, Holtzman wanted to know if levels of A-beta in the fluid that bathes neurons fluctuated as mice ate, exercised, slept and otherwise did what mice do. It seemed like a run-of-the-mill question. To Holtzman’s surprise, time of day mattered — a lot. A-beta levels were highest when the animals were awake but fell when the mice were sleeping (SN: 10/24/09, p. 11). “We just stumbled across this,” Holtzman says. Still, it wasn’t clear whether the difference was related to the hour, or to sleep itself. So Holtzman and colleagues designed an experiment in which they used a drug to force mice to stay awake or fall asleep. Sure enough, the A-beta levels in the brain-bathing fluid rose and fell with sleep, regardless of the time on the clock. A-beta levels in deeply sleeping versus wide-awake mice differed by about 25 percent. That may not sound like a dramatic drop, but over the long term, “it definitely will influence the probability [that A-beta] will aggregate to form amyloid plaques,” Holtzman says. The study turned conventional thinking on its head: Perhaps Alzheimer’s doesn’t just make it hard to sleep. Perhaps interrupted sleep drives the development of Alzheimer’s itself. Published in Science in 2009, the paper triggered a flood of research into sleep and Alzheimer’s. While the initial experiment found that the condition worsens the longer animals are awake, research since then has found that the reverse is true, too, at least in flies and mice. Using fruit flies genetically programmed to mimic the neurological damage of Alzheimer’s disease, a team led by researchers at Washington University School of Medicine reversed the cognitive problems of the disease by simply forcing the flies to sleep (SN: 5/16/15, p. 13). Researchers from Germany and Israel reported in 2015 in Nature Neuroscience that slow-wave sleep — the deep sleep that occupies the brain most during a long snooze and is thought to be involved in memory storage — was disrupted in mice that had A-beta deposits in their brains. When the mice were given low doses of a sleep-inducing drug, the animals slept more soundly and improved their memory and ability to navigate a water maze. Gray matters Even with these studies in lab animals indicating that loss of sleep accelerates Alzheimer’s, researchers still hesitate to say the same is true in people. There’s too little data. Human studies are harder and more complicated to do. One big hurdle: The brain changes in humans that lead to Alzheimer’s build up over decades. And you can’t do a controlled experiment in people that forces half of the study’s volunteers to endure years of sleep deprivation. Plus the nagging chicken-and-egg problem is hard to get around, although a study published in June in JAMA Neurology tried. Researchers from the Mayo Clinic in Rochester, Minn., examined the medical records of 283 people older than 70. None had dementia when they enrolled in the Mayo Clinic Study of Aging. At the study’s start, participants answered questions about their sleep quality and received brain scans looking for plaque deposits. People who reported excessive daytime sleepiness — a telltale sign of fitful sleep — had more plaques in their brains to start with. When checked again about two years later, those same people showed a more rapid accumulation than people who slept soundly. Other scientists have used brain scans to measure what happens to A-beta in people’s brains after a sleepless night. Researchers from the National Institutes of Health and colleagues completed a study involving 20 healthy people who had a brain scan while rested and then again after they were forced to stay awake for 31 hours. please log in to view this image HARD DAY'S NIGHT Scientists measured accumulation of amyloid-beta in people who were rested (left) and then again after 31 hours without sleep (right). In this PET scan of one volunteer’s brain, levels of A-beta, which is linked to Alzheimer’s, rose in the hippocampus (yellow at arrow) after sleep deprivation. E. SHOKRI-KOJORI/NIH Nora Volkow, head of the National Institute on Drug Abuse in Bethesda, Md., led the study. She is interested in sleep’s potential connections to dementia because people with drug addiction have massive disruptions of sleep. For the study, the researchers injected people with a compound that latches onto A-beta and makes it visible under a PET scanner. The sleep-deprived brains showed an increase in A-beta accumulation that was about 5 percent higher in two areas of the brain that are often damaged early in Alzheimer’s: the thalamus and hippocampus. Other regions had lesser buildup. “I was surprised that it was actually so large,” says study coauthor Ehsan Shokri-Kojori, now at the National Institute on Alcohol Abuse and Alcoholism. “Five percent from one night of sleep deprivation is far from trivial.” And while the brain can likely recover with a good night’s sleep, the question is: What happens when sleep deprivation is a pattern night after night, year after year? “It does highlight that sleep is indispensable for proper brain function,” Volkow says. “What we have to question is what happens when you are consistently sleep deprived.” The study was published April 24 in the Proceedings of the National Academy of Sciences. One bad night Using PET scans to measure amyloid-beta markers, researchers compared levels of A-beta in the brains of 20 healthy volunteers after one restful night and after one night of sleep deprivation. Levels of the plaque-forming A-beta rose in most people tested. please log in to view this image E. SHOKRI-KOJORI ET AL/PNAS 2018 As tantalizing as studies like this may seem, there are still inconsistencies that scientists are trying to resolve. Consider a study published in May in Sleep from a team of Swedish and British researchers. They set out to measure levels of A-beta in cerebrospinal fluid and markers of neuron injury in 13 volunteers, sleep deprived and not. The first measurements took place after five nights of sound sleep. Then participants were cut back to four hours of sleep a night, for five nights. Four participants even lasted eight days with only four hours of nightly sleep. After good sleep versus very little, the measurements did not show the expected differences. “That was surprising,” says Henrik Zetterberg of the University Gothenburg in Sweden. Given the previous studies, including his own, “I would have expected a change.” He notes, however, that the study participants were all healthy people in their 20s and 30s. Their youthful brains might cope with sleep deprivation more readily than those in middle age and older. But that’s just a hypothesis. “It shows why we have to do further research,” he says. Rinse cycle Questions could be better answered if scientists could find a mechanism to explain how sleepless nights might exacerbate Alzheimer’s. In 2013, scientists revealed an important clue. The lymphatic system flows through the body’s tissues to pick up waste and carry it away. All lymphatic vessels run to the liver, the body’s recycling plant for used proteins from each organ’s operation. But the lymphatic system doesn’t reach the brain. “I found it weird because the brain is our most precious organ — why should it be the only organ that recycles its own proteins?” asks Maiken Nedergaard, a neuroscientist at the University of Rochester in New York. Maybe, she thought, the brain has “a hidden lymphatic system.” Nedergaard and colleagues decided to measure cerebrospinal fluid throughout the brain. When mice were awake, there appeared to be little circulation of fluid in the brain. Then the team examined sleeping mice. “You take mice and train them to be quiet under a microscope,” Nedergaard says. “The mice after a couple of days feel very calm. Especially if you do it during the daytime when they are supposed to be sleeping, and they are warm and you give them sugar water. They’re not afraid.” Slumbering stream Flow of cerebrospinal fluid in a mouse’s brain is much higher during sleep (left, red) than when the animal is awake (right, green). M. NEDERGAARD The day of the experiment, the scientists made a hole in the mice’s skulls, placed a cover over it and injected a dye to measure cerebrospinal fluid in the brain. During sleep, the spaces between the brain cells widened by about 60 percent and allowed more fluid to wash through, taking the metabolic debris, including A-beta, with it. “It’s like the dishwasher turned on,” Nedergaard says. She named this phenomenon the “glymphatic system” because it appears to be controlled by glial cells, brain cells that help insulate neurons and perform much of the brain’s routine maintenance work (SN: 8/22/15, p. 18). Similar observations of cerebrospinal fluid circulation have been carried out in people, but with less invasive ways of measuring. In one, researchers from Oslo University Hospital, Rikshospitalet compared 15 patients who had a condition called normal pressure hydrocephalus, a kind of dementia caused by buildup of cerebrospinal fluid in the cavities of the brain, with eight people who didn’t have the condition. The researchers used a tracer for cerebrospinal fluid and magnetic resonance imaging to measure the flow over 24 hours. Immediately after a night’s sleep, cerebrospinal fluid had drained in healthy people but lingered in the patients with dementia, the researchers reported in Brain in 2017. Go with the flow One way the brain might clear out waste, including amyloid-beta, is via circulation of cerebrospinal and interstitial fluids. Fluid flows through the spaces in the brain, bathing neurons and eventually carrying debris out of the brain toward the liver. Studies suggest that this “glymphatic” circulation increases during sleep. please log in to view this image E. OTWELL Source: M. Nedergaard/Science 2013 Don’t snooze, you lose? The central question — the one that doctors really want to answer — is whether better sleep could treat or even prevent Alzheimer’s. To try to figure this out, Bendlin and her Wisconsin colleagues are now studying people with sleep apnea. People with that condition stop breathing during the night, which wakes them up and makes for a lousy night’s sleep. A machine called a CPAP, short for continuous positive airway pressure, treats the condition. “Once people start treatment, what might we see in the brain? Is there a beneficial effect of CPAP on markers of Alzheimer’s?” Bendlin wonders. “I think that’s a big question because the implications are so large.” A study reported in Neurology in 2015 offers a reason to think CPAP might help. Using data from almost 2,500 people in the Alzheimer’s Disease Neuroimaging Initiative, researchers at the New York University School of Medicine found that people with sleep disorders like obstructive sleep apnea showed signs of mild cognitive problems and Alzheimer’s disease at younger ages than those who did not. But for those who used CPAP, onset of mild cognitive problems was delayed. “If we find out that sleep problems contribute to brain amyloid — what that really says is there may be a window to intervene,” Bendlin says. And the solution — more attention to sleep — is one prescription with no side effects.
A high-energy neutrino has been traced to its galactic birthplace An Antarctic research station detected the high-energy particle as it slammed into the ice BY EMILY CONOVER 11:00AM, JULY 12, 2018 please log in to view this image HOME BASE Scientists traced a high-energy neutrino back to its source: a blazar, a galaxy harboring a supermassive black hole that fuels powerful jets of particles. A zippy little particle has been traced back to its cosmic stomping grounds, a flaring galaxy 4 billion light-years away, for the first time solving a cosmic whodunit. Scientists have long puzzled over the sources of high-energy particles from space, which batter the Earth at energies that can outstrip the world’s most advanced particle accelerators. Now, physicists have identified the source of an energetic, lightweight particle called a neutrino. The intergalactic voyager came from a type of bright galaxy called a blazar located in the direction of the constellation Orion, scientists report online July 12 in Science. “This is super exciting news,” says astrophysicist Angela Olinto of the University of Chicago, who was not involved with the new result. “It’s marking the beginning of what we call neutrino astronomy,” which uses the nearly massless particles to reveal secrets of cosmic oddities like blazars. While there may be additional cosmic sources for high-energy neutrinos, the detection indicates that at least some come from blazars. The result also suggests that blazars emit other energetic particles known as cosmic rays, which are produced in tandem with neutrinos. The origins of high-energy cosmic rays are poorly understood and until now, “nobody has ever been able to pinpoint a source that produces them,” says astrophysicist Francis Halzen of the University of Wisconsin–Madison, a leader of IceCube, the Antarctic neutrino observatory that detected the particle. Thanks to this discovery, “we will better understand nature of the universe’s immense cosmic accelerators,” France Córdova said in a July 12 news conference in Alexandria, Va. Scientists can’t produce such high-energy particles on Earth, “so we have to turn to the heavens to deepen our understanding of the highest-energy processes,” said Córdova, the director of the National Science Foundation, which funded IceCube. please log in to view this image ICE BREAKER The particle detector IceCube (shown) uses sensors in the Antarctic ice to detect high-energy neutrinos from sources outside the Milky Way. THE ICECUBE COLLABORATION IceCube, which was constructed within a cubic kilometer of ice sheet, uses thousands of embedded sensors to measure light produced when neutrinos slam into the ice. On September 22, 2017, IceCube detected a neutrino with an energy of nearly 300 trillion electron volts. (For comparison, protons in the Large Hadron Collider in Geneva reach energies of 6.5 trillion electron volts.) please log in to view this image ORION’S ARMPIT For the first time, a high-energy neutrino has been traced to a source outside of the Milky Way, a galaxy in the constellation of Orion (location indicated in blue). THE ICECUBE COLLABORATION By tracing the neutrino’s track backward, scientists zeroed in on a region of sky in the direction of the constellation Orion. Astronomers leapt into action, and telescopes around the world scoured the spot for light that could reveal the particle’s source. A flare of gamma rays, a type of high-energy light, was detected by the Fermi Gamma-ray Space Telescope coming from a blazar called TXS 0506+056, a brilliant galaxy powered by an enormous black hole that launches a jet of energetic particles in the direction of Earth. A variety of telescopes observed the blazar’s flare in other types of light, including X-rays and radio waves. Coming on the heels of the detection of gravitational waves and light from colliding neutron stars (SN: 11/11/17, p. 6) observed in August 2017, Fermi researcher Regina Caputo thought, “This is crazy, the sky is erupting,” she says. “I almost couldn’t believe it; the universe is revealing itself in ways we have never imagined before,” says Caputo, of NASA’s Goddard Space Flight Center in Greenbelt, Md. The detection of high-energy neutrinos with a well-defined incoming direction is rare — IceCube sent astronomers only 10 reports of such detections in the year and a half before this neutrino was found. This was the first time researchers were lucky enough to also spot the source’s light. “This is really what IceCube was built for, to try to see high-energy neutrinos from these exotic sources,” says neutrino physicist Kate Scholberg of Duke University, who was not involved with the research. Previously, scientists have identified the birthplaces of neutrinos of much lower energies: an exploding star (SN: 2/18/17, p. 24) and the sun. But high-energy neutrinos have been more elusive. While there have been previous hints of high-energy neutrinos associated with blazar flare-ups (SN Online: 4/7/16), the new detection makes the first solid connection between blazars and high-energy neutrinos. After unmasking the neutrino’s source, the IceCube researchers went back to their data and looked for additional neutrinos that could have come from the blazar. “There was something interesting happening there,” says IceCube researcher Naoko Kurahashi Neilson of Drexel University in Philadelphia. Over seven months starting in September 2014, IceCube saw a neutrino flare, an excess of high-energy neutrinos from that vicinity, the researchers report in a second paper published in the July 13 Science. please log in to view this image SEE THE LIGHT Sensors embedded in ice (illustrated) are used in the IceCube experiment to detect light emitted when a neutrino interacts with the ice. THE ICECUBE COLLABORATION Blazars are still poorly understood, including what kinds of particles they blast out. Because high-energy neutrinos can be produced only in combination with protons, the detection reveals that blazars are also a source of cosmic rays, which consist of protons and atomic nuclei. Cosmic rays have been detected on Earth at ultrahigh energies, and it’s been a mystery what kind of cosmic engine could rev particles up to those extremes. “This may be a clue to their origin,” says astrophysicist Floyd Stecker of NASA Goddard. But it’s still not clear whether blazars can accelerate protons to the very highest energies observed, he says. The highest energy cosmic rays are known to come from outside the Milky Way (SN: 10/14/17, p. 7). But in general, cosmic rays leave few clues of their birthplaces: As they travel through space, their trajectories get twisted by magnetic fields, and therefore don’t reliably point back to their sources. Neutrinos, on the other hand, are electrically neutral, which means they are unaffected by magnetic fields, traveling in a straight line from their origins to Earth. Since high-energy cosmic rays and neutrinos are produced together, the particles can help scientists understand cosmic rays as well, Olinto says. “What neutrinos gave us is a way through the fog.”
One particle’s trek suggests that ‘spacetime foam’ doesn’t slow neutrinos The nearly massless particles appear to travel at virtually the speed of light BY EMILY CONOVER 7:00AM, JULY 19, 2018 please log in to view this image SPEED TEST A neutrino blasted from a bright galaxy known as a blazar (illustrated) along with a flare of light reveals that neutrinos travel at roughly the speed of light. An intergalactic race between light and a bizarre subatomic particle called a neutrino has ended in a draw. The tie suggests that high-energy neutrinos, which are so lightweight they behave as if they’re massless, adhere to a basic rule of physics: Massless particles travel at the speed of light. Comparing the arrival times of a neutrino and an associated blaze of high-energy light emitted from a bright, flaring galaxy (SN Online: 7/12/18) showed that the neutrino and light differed in speed by less than a billionth of a percent, physicists report in a paper posted July 13 at arXiv.org. Massless particles — including the particles of light known as photons — consistently move about 300,000 kilometers per second, while massive particles move more slowly. Although neutrinos have mass, their heft is so infinitesimal that high-energy neutrinos travel at a rate effectively indistinguishable from that of light. Some theories propose that a “spacetime foam” might slow particles of very high energies. The idea is that spacetime on extremely small scales is not smooth, but foamy. As a result, high-energy particles could get bogged down, as if moving through molasses. That effect could cause a significant difference between the speeds of the neutrino and the associated light, which would build up into a delay over the 4-billion-light-year trip from the neutrino’s home galaxy to Earth. But since the flare of light was spotted around the same time as the neutrino, there’s no evidence for such a discrepancy. The result once again refutes a 2011 claim that neutrinos might travel faster than light. That measurement, made by a particle detector known as OPERA, was eventually determined to have been distorted by a loose cable (SN: 4/7/12, p. 9).
A star orbiting a black hole shows Einstein got gravity right — again It’s the first time an effect of general relativity has been observed in such an environment BY EMILY CONOVER 8:00AM, JULY 26, 2018 please log in to view this image BLACK HOLE SUN Einstein’s theory of gravity was upheld in measurements of a star that recently made a close pass by the supermassive black hole at the center of the Milky Way, as shown in this artist’s conception illustrating the star’s trajectory over the past few months. A single star, careening around the monster black hole in the center of the Milky Way, has provided astronomers with new proof that Albert Einstein was right about gravity. More than 100 years ago, Einstein’s general theory of relativity revealed that gravity is the result of matter curving the fabric of spacetime (SN: 10/17/15, p. 16). Now, in a paper published July 26 in Astronomy & Astrophysics, a team of researchers reports the observation of a hallmark of general relativity known as gravitational redshift. The measurement is the first time general relativity has been confirmed in the region near a supermassive black hole. As light escapes a region with a strong gravitational field, its waves get stretched out, making the light redder, in a process known as gravitational redshift. The scientists, a team known as the GRAVITY collaboration, used the Very Large Telescope array, located in the Atacama Desert of Chile, to demonstrate that light from the star was redshifted by just the amount predicted by general relativity. Scientists have observed gravitational redshift before. In fact, GPS satellites would fail to function properly if gravitational redshift weren’t taken into account. But such effects have never been seen in the vicinity of a black hole. “That’s completely new, and I think that’s what makes it exciting — doing these same experiments not on Earth or in the solar system, but near a black hole,” says physicist Clifford Will of the University of Florida in Gainesville, who was not involved with the new study. At the Milky Way’s heart there lurks a hulking supermassive black hole, with a mass about 4 million times that of the sun. Many stars swirl around this black hole (SN Online: 1/12/18). The researchers zeroed in on one star, known as S2, which completes an elliptical orbit around the black hole every 16 years. please log in to view this image CLOSE ENCOUNTER A swarm of stars orbits the Milky Way’s supermassive black hole, shown in this simulation. L. CALÇADA/SPACEENGINE.ORG/ESO In May 2018, the star made its closest approach to the black hole, zipping by at 3 percent of the speed of light — extremely fast for a star. At that point, the star was just 20 billion kilometers from the black hole. That may sound far away, but it’s only about four times the distance between the sun and Neptune. Measuring the effects of general relativity in the black hole’s neighborhood is challenging because the region is jam-packed with stars, says astrophysicist Tuan Do of UCLA, who studies S2, but was not involved with this work. If attempting to observe this region with a run-of-the-mill telescope, “you’ll just see this big blur.” To obtain precise measurements and pinpoint individual stars in the crowd, the scientists used a technique called adaptive optics (SN Online: 7/18/18), which can counteract the distortions caused by the Earth’s atmosphere, and combined information from four telescopes in the Very Large Telescope’s array. “You can bring the light together from these four telescopes and thereby generate a super telescope ... and that does the trick,” says study coauthor Reinhard Genzel, an astrophysicist at the Max Planck Institute for Extraterrestrial Physics in Garching, Germany. Genzel and colleagues have been observing this star for decades, since before its previous swing by the black hole 16 years ago. In future work, the scientists hope to test other aspects of general relativity, including the theory’s prediction that S2’s orbit should rotate over time. A similar rotation was previously seen in Mercury’s orbit around the sun, which puzzled astronomers until Einstein’s theory explained the effect (SN Online: 4/11/18). The GRAVITY researchers might find other stars that orbit even closer to the black hole, allowing them to better understand the black hole and further scrutinize general relativity. If that happens, Will says, “they’ll really start to explore this black hole up close and personal, and it'll be a very cool new set of tests of Einstein’s theory.”
