"SpaceX's unorthodox card-dealing launch of 60 Starlink broadband satellites has led to an unusual viewing opportunity for skywatchers -- and an occasion to wonder about the impact of such mega-constellations on the natural night sky," reports GeekWire: A video captured by satellite-watcher Marco Langbroek in the Netherlands sums up the awe... It didn't take long for Langbroek and other skywatchers to work out the coordinates for the long train of satellites, and to plug those coordinates into online satellite-pass calculators such as CalSky. On Twitter, David Dickinson, author of "The Universe Today: Ultimate Guide to Viewing the Cosmos," started doling out location-specific sighting predictions based on the Orbitron satellite-tracking program.

CalSky automatically picks up your coordinates for satellite sightings, but for those in the Seattle area, the best time to look for the Starlink train passing by tonight is likely to be in the range of 10:50 to 11:10 p.m. PT, going from southwest to northeast. That's a liberal stretch of time that accounts for a range of locations (say, Port Townsend vs. North Bend), plus uncertainties in the orbital estimates. There are other passes overnight at around 12:30, 3:50 and 5:20 a.m. PT. The brightness of the satellites is a question mark. Some say they can be seen with the naked eye, while others advise scanning with binoculars. A lot depends on how the satellites pick up the glint of the sun after dusk or before dawn. Tonight Langbroek reported that the satellite train wasn't as bright as it was the night before.

Speaking of brightness, astronomers and SpaceX fans have already begun the debate over the prospect of having thousands of broadband-beaming satellites in low Earth orbit. The 60 satellites launched this week merely represent the beginning of a campaign aimed at launching as many as 11,000 such spacecraft. And that's just for SpaceX's Starlink system. Thousands more could go into orbit for the constellations being contemplated by OneWeb, Telesat, LeoSat Enterprises and Amazon's Project Kuiper.
Today Elon Musk tweeted defensively that "sats will be in darkness when stars are visible" -- while GeekWire points out that the satellites are also scheduled to spread. "Within just a few days, the tightly spaced 'train' will turn into a dispersed chain that girdles the globe," their article concludes.

"And once that happens, chances are that skywatchers and sky-worriers alike will turn their attention to the next batch of Starlink satellites."

New submitter jimminy_cricket writes: Recently at the Laboratory for Laser Energetics in Brighton, New York, one of the world's most powerful lasers blasted a droplet of water, creating a shock wave that raised the water's pressure to millions of atmospheres and its temperature to thousands of degrees. X-rays that beamed through the droplet in the same fraction of a second offered humanity's first glimpse of water under those extreme conditions. The x-rays revealed that the water inside the shock wave didn't become a superheated liquid or gas. Paradoxically -- but just as physicists squinting at screens in an adjacent room had expected -- the atoms froze solid, forming crystalline ice.

"You hear the shot," said Marius Millot of Lawrence Livermore National Laboratory in California, and "right away you see that something interesting was happening." Millot co-led the experiment with Federica Coppari, also of Lawrence Livermore. The findings, published this week in Nature, confirm the existence of "superionic ice," a new phase of water with bizarre properties. Unlike the familiar ice found in your freezer or at the north pole, superionic ice is black and hot. A cube of it would weigh four times as much as a normal one. It was first theoretically predicted more than 30 years ago, and although it has never been seen until now, scientists think it might be among the most abundant forms of water in the universe.

The CEO of Party City cited a global helium shortage as he announced on Thursday that the retail chain will close 45 of its 870 stores this year. The shortage has been hitting party supply stores particularly hard for months, CNBC reported last month. Miami Herald reports: Party City CEO James Harrison said in February that the company was already missing its revenue "in large part due to helium supply pressures," according to CNBC, which reports that the company has experimented with "decorative air-filled balloons -- in lieu of the real thing. The company didn't say which stores will close this year.

"The problem is, helium is being used up faster than it can be produced these days," Anders Bylund, an analyst at Motley Fool, said in an investing note. "Helium shortages fluctuate over time and across geographical markets, but anywhere between 50 and 200 of Party City's 850 stores don't have any helium in their tanks at any given time." Bylund added: "Helium may be the second most plentiful element in the universe, but it's also one of the lightest and doesn't form molecules easily with heavier atoms. Hence, the helium we use ends up floating into space, never to be seen again. There is no economically efficient way to manufacture the gas, so the bulk of the worldwide helium supply is a byproduct of natural gas extraction."

Slashdot reader schwit1 shares a report from USA Today discussing a new book from famed astronautical engineer Bob Zubrin, who makes the case for why we should go to space -- not only for the knowledge and challenge, but to "ensure our survival and protect our freedom." Among the reasons why he thinks we need to spread out through the Solar System (and perhaps beyond): For the Knowledge: We know little about the universe, despite our conceit that we have things figured out. The farther we go, the more new things we will encounter, and the more our knowledge and understanding will expand.

For the Challenge: Zubrin looks at the way the Age of Exploration rejuvenated a stagnant Europe at the beginning of the 16th Century, and the way the American frontier imparted a dynamism to American culture that, since that frontier's closing, seems to have faded. New frontiers, with their array of opportunities and challenges, make an excellent antidote to stagnation, aristocracy and zero-sum thinking.

For Our Survival: Last week saw reports that an 1100-foot asteroid will pass within 13,000 miles of earth -- that's closer than many satellites -- in less than a decade. (The famous Barringer Meteor Crater in Arizona was made by an asteroid a fraction that size, and exploded with the force of more than 100 Nagasaki-sized atomic bombs). These asteroid encounters turn out to be much more common than once thought, and the likelihood of a strike is high enough that authorities are rehearsing a response. With a strong space economy, deflecting dangerous asteroids will be easy. Without it, we're just sitting ducks in a cosmic shooting gallery.

For Our Freedom: Earth is crowded, and governments (and corporations like Facebook) are getting ever more intrusive as privacy grows every more scarce. The danger of a global tyranny backed by modern technology of surveillance and control is growing. Getting a sizable chunk of humanity off the planet and far enough away -- the Moon, Mars, even the asteroid belt -- makes it less likely that such a tyranny could become all-encompassing.

An anonymous reader quotes a report from Phys.Org: An international team of scientists has demonstrated for the first time that it is possible to generate a measurable amount of electricity in a diode directly from the coldness of the universe. The infrared semiconductor device faces the sky and uses the temperature difference between Earth and space to produce the electricity. In contrast to leveraging incoming energy as a normal solar cell would, the negative illumination effect allows electrical energy to be harvested as heat leaves a surface. Today's technology, though, does not capture energy over these negative temperature differences as efficiently. By pointing their device toward space, whose temperature approaches mere degrees from absolute zero, the group was able to find a great enough temperature difference to generate power through an early design.

The group found that their negative illumination diode generated about 64 nanowatts per square meter, a tiny amount of electricity, but an important proof of concept, that the authors can improve on by enhancing the quantum optoelectronic properties of the materials they use. Calculations made after the diode created electricity showed that, when atmospheric effects are taken into consideration, the current device can theoretically generate almost 4 watts per square meter, roughly one million times what the group's device generated and enough to help power machinery that is required to run at night. By comparison, today's solar panels generate 100 to 200 watts per square meter. The study has been published in the journal Applied Physics Letters.

Avengers: Endgame has already earned more money in just five days than 17 of the 21 previous films in the Marvel Cinematic Universe did in their entire theatrical run (including Captain Marvel). The Wrap reports that it's the first time in history a movie has earned over a billion dollars in just its first weekend.

It demolished the record $640,521,291 global box office opening for the previous Avengers movie, Infinity Wars, in 2018. This weekend the sequel earned $1,209,000,000, with both Avengers films earning more than the next-biggest-opening films The Fate of the Furious and Star Wars: The Force Awakens.

In fact, "In one fell swoop, Avengers: Endgame has already made more than movies like Skyfall, Aquaman and The Dark Knight Rises grossed in their entire runs, not accounting for inflation," reports USA Today: To accommodate demand, Disney released Avengers: Endgame in more theaters (4,662 in the U.S. and Canada) than any opening before. Advance ticketing services set new records. Early ticket buyers crashed AMC's website. And starting Thursday, some theaters even stayed open 72 hours straight. "We've got some really tired staff," says John Fithian, president and chief executive of the National Association of Theater Owners. "I talked to an exhibitor in Kansas who said, 'I've never sold out a 7 a.m. show on Saturday morning before,' and they were doing it all across their circuit."

Not working in the film's favor was its lengthy three-hour running time. But theaters added thousands of showings for Endgame to get it on more screens than any movie before to satiate the frenzy.

For an industry dogged by uncertainty over the growing role of streaming, the weekend was a mammoth display of the movie theater's lucrative potency. Fithian calls it possibly "the most significant moment in the modern history of the movie business.... We're looking at more than 30 million American and more than 100 million global guests that experienced Endgame on the big screen in one weekend," Fithian says. "The numbers are just staggering...."

Disney now holds all but one of the top 12 box-office openings of all time. (Universal's Jurassic World is the lone exception...) After its acquisition of 20th Century Fox, Disney is expected to account for at least 40% of domestic box-office revenue in 2019, a new record of market share... The company's Captain Marvel -- positioned as a kind of Marvel lead-in to Endgame -- rose to No. 2 in its eighth weekend in theaters.
Comscore reports that the movie accounted for 88% of all ticket sales this weekend -- and that the total weekend box office of $400 million was the largest ever. Theatre owners hope this will also mean more ticket sales in the future, with millions of moviegoers exposed to trailers for upcoming films. And whatever happens, "This has got to be the biggest weekend in popcorn history," a senior media analyst for Comscore told USA Today.

"Think of the gallons of soda and the hot dogs sold!"

Zorro shares a report from CBS News: If you're looking for more "Avengers: Endgame" content to fill the void until you get to see the movie, Google has the perfect Easter egg for you. Open Google, search "Thanos," click the Infinity Gauntlet on the right side -- and watch as half of your search results turn to dust. The gauntlet -- complete with the six Infinity Stones -- will snap its fingers when clicked, just as Thanos did in "Avengers: Infinity War." But this time, instead of eliminating half of the universe's population, Thanos will eliminate half your Google Search results, perfectly balancing the internet. Make sure you turn the sound on.

Slashdot reader The Snazster shares a report from ScienceDaily, reporting on materials provided by Johns Hopkins University: New measurements from NASA's Hubble Space Telescope confirm that the Universe is expanding about 9% faster than expected based on its trajectory seen shortly after the big bang, astronomers say. The new measurements, published April 25 in the Astrophysical Journal Letters, reduce the chances that the disparity is an accident from 1 in 3,000 to only 1 in 100,000 and suggest that new physics may be needed to better understand the cosmos.

In this study, [Adam Riess, Bloomberg Distinguished Professor of Physics and Astronomy at The Johns Hopkins University, Nobel Laureate and the project's leader] and his SH0ES (Supernovae, H0, for the Equation of State) Team analyzed light from 70 stars in our neighboring galaxy, the Large Magellanic Cloud, with a new method that allowed for capturing quick images of these stars. The stars, called Cepheid variables, brighten and dim at predictable rates that are used to measure nearby intergalactic distances. The usual method for measuring the stars is incredibly time-consuming; the Hubble can only observe one star for every 90-minute orbit around Earth. Using their new method called DASH (Drift And Shift), the researchers using Hubble as a "point-and-shoot" camera to look at groups of Cepheids, thereby allowing the team to observe a dozen Cepheids in the same amount of time it would normally take to observe just one. [...] As the team's measurements have become more precise, their calculation of the Hubble constant has remained at odds with the expected value derived from observations of the early universe's expansion by the European Space Agency's Planck satellite based on conditions Planck observed 380,000 years after the Big Bang. "This is not just two experiments disagreeing," Riess explained. "We are measuring something fundamentally different. One is a measurement of how fast the universe is expanding today, as we see it. The other is a prediction based on the physics of the early universe and on measurements of how fast it ought to be expanding. If these values don't agree, there becomes a very strong likelihood that we're missing something in the cosmological model that connects the two eras."

A detector designed to hunt for dark matter has succeeded in detecting one of the rarest particle interactions in the universe. "According to a new study published today in the journal Nature, the team of more than 100 researchers measured, for the first time ever, the decay of a xenon-124 atom into a tellurium 124 atom through an extremely rare process called two-neutrino double electron capture," reports Live Science. "This type of radioactive decay occurs when an atom's nucleus absorbs two electrons from its outer electron shell simultaneously, thereby releasing a double dose of the ghostly particles called neutrinos." From the report: By measuring this unique decay in a lab for the first time, the researchers were able to prove precisely how rare the reaction is and how long it takes xenon-124 to decay. The half-life of xenon-124 -- that is, the average time required for a group of xenon-124 atoms to diminish by half -- is about 18 sextillion years (1.8 x 10^22 years), roughly 1 trillion times the current age of the universe. This marks the single longest half-life ever directly measured in a lab. Only one nuclear-decay process in the universe has a longer half-life: the decay of tellurium-128, which has a half-life more than 100 times longer than that of xenon-124. But this vanishingly rare event has only been calculated on paper.

An anonymous reader quotes The Next Web: As stunning and ground-breaking as it is, the EHT project is not just about taking on a challenge. It's an unprecedented test of whether Einstein's ideas about the very nature of space and time hold up in extreme circumstances, and looks closer than ever before at the role of black holes in the universe. To cut a long story short: Einstein was right....

His general theory of relativity has passed two serious tests from the universe's most extreme conditions in the last few years. Here, Einstein's theory predicted the observations from M87 with unerring accuracy, and is seemingly the correct description of the nature of space, time, and gravity. The measurements of the speeds of matter around the center of the black hole are consistent with being near the speed of light.
The advanced computing research center at the University of Texas at Austin says the data for the photo "was collected during a 2017 global campaign, after decades of scientific, engineering, and computational research and preparation." And their own facility played a role in the finished photo, according to an article shared by aarondubrow: Helping to lay the groundwork for the black hole imaging, and providing the theoretical underpinnings that enabled the researchers to interpret the mass, underlying structure, and orientations of the black hole and its environment, were supercomputers at The University of Texas at Austin's Texas Advanced Computing Center (TACC) -- Stampede1, Stampede2 and Jetstream -- all three of which were supported by grants from the National Science Foundation (NSF), which also provided key funding for the EHT... "We are doing finite difference, three-dimensional simulations with not just gas dynamics, but also magnetic fields," said Harvard University professor and EHT researcher Ramesh Narayan. "That includes radiation and what is called two-temperature physics in a general relativistic framework. For these, we really do need the TACC's Stampede system with lots of cores and lots of hours.... The simulations are computationally very expensive and supercomputers are definitely needed...."

Alongside the simulation and modeling effort, another group of researchers from the University of Arizona (UA) were using Jetstream -- a large-scale cloud environment for research located both at TACC and Indiana University -- to develop cloud-based data analysis pipelines that proved crucial for combining huge amounts of data taken from the geographically-distributed observatories, and sharing the data with researchers around the world. "New technologies such as cloud computing are essential to support international collaborations like this," said Chi-kwan Chan, leader of the EHT Computations and Software Working Group and an assistant astronomer at UA. "The production run was actually carried out on Google Cloud, but much of the early development was on Jetstream. Without Jetstream, it is unclear that we would have a cloud-based pipeline at all."

You can now download the source code of every Infocom text adventure game, thanks to archivist Jason Scott who uploaded the code to GitHub. "There are numerous repositories under the name historicalsource, each for a different game," reports Ars Technica. "Titles include, but are not limited to, The Hitchhiker's Guide to the Galaxy, Planetfall, Shogun, and several Zork games -- plus some more unusual inclusions like an incomplete version of Hitchhiker's sequel The Restaurant at the End of the Universe, Infocom samplers, and an unreleased adaptation of James Cameron's The Abyss." From the report: The code was uploaded by Jason Scott, an archivist who is the proprietor of textfiles.com. His website describes itself as "a glimpse into the history of writers and artists bound by the 128 characters that the American Standard Code for Information Interchange (ASCII) allowed them" -- in particular those of the 1980s. He announced the GitHub uploads on Twitter earlier this week. The games were written in the LISP-esque "Zork Implementation Language," or ZIL, which you could be forgiven for not being intimately familiar with already. Fortunately, Scott also tweeted a link to a helpful manual for the language on archive.org. Gamasutra, which first reported the news, notes that Activision still owns the rights to Infocom games and could request a takedown if it wanted.

Astronomers have detected the universe's first molecule. "Helium hydride (HeH), a combination of helium and hydrogen, was spotted some 3000 light-years from Earth by an instrument aboard the airborne Stratospheric Observatory for Infrared Astronomy (SOFIA), a telescope built into a converted 747 jet that flies above the opaque parts of Earth's atmosphere," reports Science Magazine. The findings have been reported in the journal Nature. From the report: HeH has long been thought to mark the "dawn of chemistry," as the remnants of the big bang cooled to about 4000 K and ions began to team up with electrons to form neutral atoms. Researchers believe that in that primordial gas, neutral helium reacted with hydrogen ions to form the first chemical bond joining the very first molecule. In 1925, chemists synthesized HeH in the lab. In the 1970s, theorists predicted that the molecule may exist today, most likely formed anew in planetary nebulae, clouds of gas ejected by dying sunlike stars. But decades of observations failed to find any, casting doubts on the theory.

To find the elusive molecule, astrochemists search for characteristic frequencies of light it emits, particularly a spectral line in the far infrared typically blocked by Earth's atmosphere. But a far-infrared spectrometer aboard SOFIA allowed them to find that signature for the first time, in a planetary nebula called NGC 7027, the researchers report today in Nature. The result shows this unlikely molecule -- involving typically unreactive helium -- can be created in space. With this cornerstone confirmed, it appears that the evolution of the following 13 billion years of chemistry stands on firmer ground.

An anonymous reader quotes a report from Motherboard: On Wednesday, an international team of scientists published the first image of a black hole ever. It looked like a SpaghettiO, and yet the image was an incredible scientific achievement that gave humanity a glimpse of one of the universe's most destructive forces and confirmed long-held theories -- namely, that black holes exist. Storing the raw data for the image was a feat itself -- tiny portions of data spread across five petabytes stored on multiple hard drives, the equivalent of 5,000 years worth of MP3s. Katie Bouman, a computer scientist and assistant professor at the California Institute of Technology, led the development of the algorithm that imaged the black hole. An image of her posing with some of the data drives went viral as observers praised her success.

The massive amounts of data were essential to creating the image of the black hole. Bouman and other scientists coordinated radio telescopes all over the Earth, each pointed at the black hole and gathering data at different times. The data scientists then pieced this information together and used an algorithm to fill in the blanks and generate a likely image of the black hole. The five petabytes of data took up such a massive amount of digital and physical space it couldn't be sent over the internet. Instead, the hard drives were flown to processing centers in Germany and Boston where the data was assembled. On Reddit's /r/datahoarder subreddit, a community dedicated to spreading the passion of hoarding vast amounts of data, the drives were bigger news than the scientific achievement itself.

Astronomers have captured the first image of a black hole, heralding a revolution in our understanding of the universe's most enigmatic objects. From a report: The picture shows a halo of dust and gas, tracing the outline of a colossal black hole, at the heart of the Messier 87 galaxy, 55 million light years from Earth. The black hole itself -- a cosmic trapdoor from which neither light nor matter can escape -- is unseeable. But the latest observations take astronomers right to its threshold for the first time, illuminating the event horizon beyond which all known physical laws collapse.

The breakthrough image was captured by the Event Horizon Telescope (EHT), a network of eight radio telescopes spanning locations from Antarctica to Spain and Chile, in an effort involving more than 200 scientists. Sheperd Doeleman, Event Horizon Telescope Director and Harvard University senior research fellow said: "Black holes are the most mysterious objects in the universe. We have seen what we thought was unseeable. We have taken a picture of a black hole." The image gives the first direct glimpse of a black hole's accretion disk, a fuzzy doughnut-shaped ring of gas and dust that steadily "feeds" the monster within. A video stream of the press conference.

The spectre of superintelligent machines doing us harm is not just science fiction, technologists say -- so how can we ensure AI remains 'friendly' to its makers? From a story: Jaan Tallinn (co-founder of Skype) warns that any approach to AI safety will be hard to get right. If an AI is sufficiently smart, it might have a better understanding of the constraints than its creators do. Imagine, he said, "waking up in a prison built by a bunch of blind five-year-olds." That is what it might be like for a super-intelligent AI that is confined by humans. The theorist Eliezer Yudkowsky, who has written hundreds of essays on superintelligence, found evidence this might be true when, starting in 2002, he conducted chat sessions in which he played the role of an AI enclosed in a box, while a rotation of other people played the gatekeeper tasked with keeping the AI in. Three out of five times, Yudkowsky -- a mere mortal -- says he convinced the gatekeeper to release him. His experiments have not discouraged researchers from trying to design a better box, however.

The researchers that Tallinn funds are pursuing a broad variety of strategies, from the practical to the seemingly far-fetched. Some theorise about boxing AI, either physically, by building an actual structure to contain it, or by programming in limits to what it can do. Others are trying to teach AI to adhere to human values. A few are working on a last-ditch off-switch. One researcher who is delving into all three is mathematician and philosopher Stuart Armstrong at Oxford University's Future of Humanity Institute, which Tallinn calls "the most interesting place in the universe." (Tallinn has given FHI more than $310,000.) Armstrong is one of the few researchers in the world who focuses full-time on AI safety. When I asked him what it might look like to succeed at AI safety, he said: "Have you seen the Lego movie? Everything is awesome."

An anonymous reader quotes a report from CNET: One of the central puzzles in particle physics is discovering what particle (or particles!) makes up dark matter — the form of matter that is responsible for 85 percent of the mass in the known universe. Some physicists believe searching for a hypothetical particle known as an "axion" could lead to a better understanding of dark matter and to hunt for it, a team of U.S. physicists have recently designed and tested a basketball-sized, donut-shaped apparatus that can seek it out.

It has been believed that axions may be detectable by looking at an unusual type of neutron star known as a "magnetar". These small, erupting stars create some of the most powerful magnetic fields in the universe. Because of their giant magnetic power, axions would be converted to radio waves in the presence of the magnetar -- and thus, detectable by telescopes on Earth. That strange cosmic phenomenon inspired theoretical physicists to create the impressively-named ABRACADABRA experiment (the full name is "A Broadband/Resonant Approach to Cosmic Axion Detection with an Amplifying B-field Ring Apparatus" so the theorists deserve a round of applause for that backcronym). The experiment consists of a donut (or "toroid") shaped device, dangled in a freezer just above absolute zero and fine-tuned to create its own magnetic field. If axions exist, the magnetic field in the middle of the donut could reveal them. The study has been published in the journal Physical Review Letters.

"A team of international astronomers have been hunting for ancient, supermassive black holes -- and they've hit the motherlode, discovering 83 previously unknown quasars," reports CNET: The Japanese team turned the ultra-powerful "Hyper Suprime-Cam", mounted to the Subaru Telescope in Hawaii, toward the cosmos' darkest corners, surveying the sky over a period of five years. By studying the snapshots, they've been able to pick potential quasar candidates out of the dark. Notably, their method of probing populations of supermassive black holes that are similar in size to the ones we see in today's universe, has given us a window into their origins.

After identifying 83 potential candidates, the team used a suite of international telescopes to confirm their findings. The quasars they've plucked out are from the very early universe, about 13 billion light years away. Practically, that means the researchers are looking into the past, at objects form less than a billion years after the Big Bang. "It is remarkable that such massive dense objects were able to form so soon after the Big Bang," said Michael Strauss, who co-authored the paper, in a press release. Scientists aren't sure how black holes formed in the early universe, so being able to detect them this far back in time provides new avenues of exploration.

"Scientists are hoping to unlock some of the universe's mysteries through 50-year-old moon rocks," reports the New York Daily News -- specifically, three samples that spent that half century sealed in airtight canisters. One Apollo 18 sample from 1972 contains 1.8 pounds of a vacuum-sealed lunar core that is a stratified layer of rock that will be studied by six research teams. About 842 pounds of lunar rocks and soil have been brought back to Earth over six missions. Although a great deal of it has found its way to science labs, technological breakthroughs should allow for a more thorough comprehension of the satellite's chemical and geological composition...

"When the previous generations did Apollo, they knew the technology they had in that day was not the technology we would have in this day," said NASA Administrator Jim Bridenstine. "So they made a determination that they would preserve samples. ⦠I'd like to thank, if it's OK, the Apollo generation, for preserving these samples, so that our generation could have this opportunity."
An anonymous Slashdot reader writes, "That's remarkable considering how often moon rocks were misplaced over the years."

A new study from researchers at Columbia University in New York suggests future spaceships could use black holes as powerful launch pads to explore the universe. The study "envisions firing laser beams that would curve around a black hole and come back with added energy to help propel a spacecraft to near the speed of light," reports Space.com. "Astronomers could look for signs that alien civilizations are using such a 'halo drive,' as the study dubs it, by seeing if pairs of black holes are merging more often than expected." From the report: Study author David Kipping, an astrophysicist at Columbia University in New York, came up with the idea of the halo drive through what he calls "the gamer's mindset." Using what he called a "halo drive" -- named for the ring of light it would create around a black hole -- Kipping found that even spaceships with the mass of Jupiter could achieve relativistic speeds. "A civilization could exploit black holes as galactic waypoints," he wrote in a study accepted by the Journal of the British Interplanetary Society and detailed online Feb. 28 in the arXiv preprint server.

The major drawback of a halo drive would be that "one has to travel to the nearest black hole," Kipping said. "It's akin to paying a one-time toll fee to ride the highway system. You have to pay some energy to reach the nearest access point, but after that, you can ride for free as a long as you like." The halo drive works only in close proximity to a black hole, at a distance of about five to 50 times the black hole's diameter. "This is why you have to travel to the nearest black hole first and [why you] can't simply do this across light-years of space," Kipping said. "We still first require a means to travel to nearby stars to ride the highway system. Kipping is now investigating ways to exploit other astronomical systems for relativistic flight. Such techniques "may not be quite as efficient or fast as the halo-drive approach, but these systems possess the deep energy reserves needed for these journeys," Kipping said.

fahrbot-bot shares a report from Phys.Org: Researchers from the Moscow Institute of Physics and Technology teamed up with colleagues from the U.S. and Switzerland and returned the state of a quantum computer a fraction of a second into the past. They also calculated the probability that an electron in empty interstellar space will spontaneously travel back into its recent past. The study is published in Scientific Reports.

Quantum physicists from MIPT decided to check if time could spontaneously reverse itself at least for an individual particle and for a tiny fraction of a second. That is, instead of colliding billiard balls, they examined a solitary electron in empty interstellar space. "Suppose the electron is localized when we begin observing it. This means that we're pretty sure about its position in space. The laws of quantum mechanics prevent us from knowing it with absolute precision, but we can outline a small region where the electron is localized," says study co-author Andrey Lebedev from MIPT and ETH Zurich. The physicist explains that the evolution of the electron state is governed by Schrodinger's equation. Although it makes no distinction between the future and the past, the region of space containing the electron will spread out very quickly. That is, the system tends to become more chaotic. The uncertainty of the electron's position is growing. This is analogous to the increasing disorder in a large-scale system -- such as a billiard table -- due to the second law of thermodynamics.

"However, Schrodinger's equation is reversible," adds Valerii Vinokur, a co-author of the paper, from the Argonne National Laboratory, U.S. "Mathematically, it means that under a certain transformation called complex conjugation, the equation will describe a 'smeared' electron localizing back into a small region of space over the same time period." Although this phenomenon is not observed in nature, it could theoretically happen due to a random fluctuation in the cosmic microwave background permeating the universe. The team set out to calculate the probability to observe an electron "smeared out" over a fraction of a second spontaneously localizing into its recent past. It turned out that even across the entire lifetime of the universe -- 13.7 billion years -- observing 10 billion freshly localized electrons every second, the reverse evolution of the particle's state would only happen once. And even then, the electron would travel no more than a mere one ten-billionth of a second into the past. The researchers then attempted to reverse time in a four-stage experiment by observing the state of a quantum computer made of superconducting qubits, instead of an electron. The researchers "found that in 85 percent of the cases, the two-qubit quantum computer returned back into the initial state," reports Phys.Org. "When three qubits were involved, more errors happened, resulting in a roughly 50 percent success rate. According to the authors, these errors are due to imperfections in the actual quantum computer. As more sophisticated devices are designed, the error rate is expected to drop."