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Disinfection of public drinking water is one of the great public health success stories of the 20th century. In 1900, outbreaks of cholera and typhoid, both caused by waterborne bacteria, were common in American cities. In 1908, Jersey City, N.J., became the first U.S. city to routinely disinfect community water. Other cities and towns quickly followed, and by 1920, the typhoid rate in the United States had dropped by 66 percent.

But that battle isn’t over. Around the world, more than 2 billion people lack reliable access to safe water (SN: 8/18/18, p. 14), and half a million people die each year from diarrhea caused by contaminated water, according to the World Health Organization.
And in the United States, challenges remain. The management failures that caused the 2014 lead contamination crisis in Flint, Mich., were a wake-up call (SN: 3/19/16, p. 8), but Flint is hardly alone. Systems in other big cities are also falling short. In October, officials in Newark, N.J., scrambled to hand out home water filters after it became clear that efforts to prevent lead from leaching into drinking water were not getting the job done. In the first six months of 2017, more than 22 percent of water samples in that city exceeded federal limits for lead, according to news reports.

If big cities are struggling, small towns with skimpy budgets as well as the many people who get their water from private wells often have it harder, lacking access to the infrastructure or technology to make water reliably safe. But science can help.

In this issue, Science News staff writer Laurel Hamers digs into the latest research on water treatment technology and finds a focus on efforts to invent affordable, scalable solutions. There’s a lot of engineering and chemistry involved, not surprisingly, and also physics — it’s hard to move water efficiently through a filter while also catching the bad stuff. Her story is a testament to researcher ingenuity, and a helpful primer on how a typical municipal water treatment plant works.

As I read Hamers’ story, I realized that I didn’t know how our water is treated here in Washington, D.C., even though I live barely a mile from one of the city’s two treatment plants. (I at least get credit for knowing the water comes from the Potomac River.) So I Googled it and found a description of how that process works. Plus I found data on potential contaminants such as Giardia and Cryptosporidium, as well as information on how residents can get their water tested for lead, which can leach from pipes or fixtures.
I also learned that each spring, the Washington Aqueduct briefly switches disinfectants from chloramine to chlorine while the agency cleans the water pipes. That might explain the short-lived swimming pool smell in the tap water.

For me, this became a double win; I learned a lot about advances in water treatment technology from Hamers’ reporting, and I was motivated to seek out information about my local water supply.

If other readers feel inspired by our work to learn more, count me as a happy journalist.

A newly designed airplane prototype does away with noisy propellers and turbines.

Instead, it’s powered by ionic wind: charged molecules, or ions, flowing in one direction and pushing the plane in the other. That setup makes the aircraft nearly silent. Such stealth planes could be useful for monitoring environmental conditions or capturing aerial imagery without disturbing natural habitats below.

The aircraft is the first of its kind to be propelled in this way, researchers report in the Nov. 22 Nature. In 10 indoor test flights the small plane, which weighs about as much as a Chihuahua, traveled 40 to 45 meters for almost 10 seconds at a steady height, even gaining about half a meter of altitude over the course of a flight.
Most planes rely on spinning parts to move forward. In some, an engine turns a propeller that pushes the plane forward. Or a turbine sucks in air with a spinning fan, and then shoots out jets of gas that propel the plane forward.

Ionic wind is instead generated by a high-voltage electric field around a positively charged wire, called an emitter. The electricity, often supplied by batteries, makes electrons in the air collide with atoms and molecules, which then release other electrons. That creates a swarm of positively charged air molecules around the emitter, which are drawn to a negatively charged wire. The movement of molecules between the two wires, the ionic wind, can push a plane forward. The current design uses four sets of these wires.
Moving ions have helped other things to fly through the air, such as tiny airborne robots. But conventional wisdom said that using the approach to move something through the air as big as an airplane wasn’t possible, because adding enough battery power to propel a plane this way would make it too heavy to stay aloft. (The ion thrusters that propel spacecraft through the vacuum of space work in a very different way and aren’t functional in air.) Attempts to build ion-propelled aircraft in the 1960s weren’t very successful.
MIT aeronautics researcher Steven Barrett thought differently. With the right aircraft design and light enough batteries, flight might be possible, his initial calculations suggested. So he and his team used mathematical equations to optimize various features of the airplane — its shape, materials, power supply — and to predict how each version would fly. Then the researchers built prototypes of promising designs and tested the planes at the MIT indoor track, launching them via a bungee system.
“The models and the reality of construction don’t always match up perfectly,” Barrett says, so finding the right design took a lot of tries. But in the new study, he and his collaborators report success: 10 flights of the aircraft, which has a 5-meter wingspan and weighs just under 2.5 kilograms.

Barrett’s team isn’t the only one who thought the ionic wind method might take off. Based on calculations done in his lab, “we were confident that this could be done,” says Franck Plouraboue of the Toulouse Fluid Mechanics Institute in France, who wasn’t part of the research. “Here they’ve done it — which is fantastic!”

It’s an example of distributed electric propulsion, says Plouraboue — spreading out the thrust-generating parts of the plane, instead of having one centralized source. That’s a hot area for aircraft research right now. NASA’s X-57 Maxwell plane, for example, bears 14 battery-operated motors along its wings. Increasing the number of propellers makes the plane go farther on the same amount of energy, says Plouraboue, but also increases the drag. With ionic wind propulsion, increasing the number of wires doesn’t increase drag very much.

The plane still needs some upgrades before it’s ready for the real world: Its longest flight was only 12 seconds. And while the aircraft can maintain steady flight for a short time once launched, it can’t actually get off the ground using ionic wind.

Even with improvements, ion-propelled aircraft won’t find their niche as passenger planes, predicts Daniel Drew, an aerodynamics researcher at the University of California, Berkeley, who was not involved in the work. (Drew has designed miniature flying bots that fly using ionic propulsion.) It’s probably not feasible to scale up to something the size of a 747 — there are efficiency trade-offs as planes get bigger, he says. But down the road, the approach might be useful for small, uncrewed planes or drones.

Devices that eavesdrop on neural activity can help paralyzed people command computer tablets to stream music, text friends, check the weather or surf the internet.

Three people with paralysis below the neck were able to navigate off-the-shelf computer tablets using an electrode array system called BrainGate2. The results, published November 21 in PLOS One, are the latest to show that neural signals can be harnessed to directly allow movement (SN: 6/16/12, p. 5).

The two men and one woman had electrode grids implanted over part of the motor cortex, an area of the brain that helps control movement. The brain implants picked up neural activity indicating that the participants were thinking about moving a cursor. Those patterns were then sent to a virtual mouse that was wirelessly paired to the tablet.
Using nothing more than their intentions to move a cursor, the three participants performed seven common digital tasks, including web browsing and sending e-mail. One participant looked up orchid care, ordered groceries online and played a digital piano. “The tablet became second nature to me, very intuitive,” she told the researchers when asked about her experience, according to the study.

Another participant enjoyed texting friends, “especially because I could interject some humor,” he told the scientists. The system even allowed two of the participants to chat with each other in real time.

For the study, the researchers used tablets with standard settings, without installing any shortcuts or features to make typing or navigation easier.

SAN DIEGO — Getting goose bumps doesn’t just make hairs stand on end; it may also help hair grow.

Nerves and muscles that raise goose bumps also stimulate stem cells in the skin to make hair follicles and grow hair. Ya-Chieh Hsu, a stem cell researcher at Harvard University, reported the unpublished findings December 9 at the joint meeting of the American Society for Cell Biology and the European Molecular Biology Organization. Getting goose bumps when it’s cold may encourage animals’ fur to grow thicker, Hsu said.
Nerves that are part of the sympathetic nervous system — which controls pupil dilation, heart rate and other automatic processes — nestle next to stem cells that will create hair follicles, Hsu and her colleagues found. Usually nerves are wrapped in a protective coating called myelin, like electrical wire sheathed in plastic. But Hsu’s group found that the nerves’ ends were naked where they meet hair follicle stem cells, like wires stripped at the tips to make contacts with electrical nodes.

The nerves secrete the hormone norepinephrine. That hormone is necessary for hair growth, the researchers found. Those findings might help explain why hair loss is a side effect of drugs known as beta-blockers, which interfere with norepinephrine’s action.

Sympathetic nerves next to hair follicles are also wrapped around tiny arrector pili muscles, which contract to make hair cells stand on end, causing goose bumps. Mice with mutations that prevented the muscles from growing also lacked the sympathetic nerves and didn’t grow hair normally. Men with male pattern baldness also lack arrector pili muscles in their scalps, Hsu said, suggesting that sympathetic nerves and goose bump–raising muscles may also be important in that type of baldness. Restoring the nerves and muscles may lead to new hair growth, she said.

From tales about whales to enthralling scientific histories and the memoir of a frustrated astrophysicist, 2018 was a banner year for science books. Here are Science News’ picks for the titles that should be on any science lover’s bookshelf. Find detailed reviews of many of these books in the links below and in our Editor’s Pick: Favorite books of 2018.

The Truth About Animals
Lucy Cooke

A zoologist debunks myths about bats, pandas, Adélie penguins and many other misunderstood creatures, recounting surprising stories from the animal kingdom (SN: 4/14/18, p. 26). Basic Books, $28

Spying On Whales
Nick Pyenson

In this captivating look at whales, a paleontologist dives into the animals’ past, exploring how some of Earth’s most intelligent species came to be, and their uncertain future (SN: 7/7/18, p. 29). Viking, $27

Eager
Ben Goldfarb

Some people see beavers as pests. But a science writer explains how the dam-building rodents are actually vital ecosystem engineers that can create or expand habitats that benefit the entire wildlife community (SN: 8/4/18, p. 28). Chelsea Green Publishing, $24.95

The Rise and Fall of the Dinosaurs
Steve Brusatte

In this memoir, a paleontologist blends experiences from his career with evolutionary science to take readers on an engrossing journey through time, from the beginnings of the dinosaurs to their ultimate extinction. William Morrow, $29.99

The Big Ones
Lucy Jones

A seismologist examines past catastrophic natural disasters, including volcanic eruptions, earthquakes and floods, and their impact on culture, politics and society (SN: 3/31/18, p. 26). With the past as a guide, the author warns readers to be prepared for when the next disaster strikes. Doubleday, $26.95

Losing the Nobel Prize
Brian Keating

An astrophysicist’s dream of winning a Nobel Prize turned to dust after a promising experiment failed to find the first definitive evidence of cosmic inflation. The experience revealed how the prize can hamper scientific progress (SN: 4/14/18, p. 27). W.W. Norton & Co., $27.95

The Poisoned City
Anna Clark

Weaving together history, science and reporting, a journalist explores the public health crisis that began in Flint, Mich., when lead started leaching into residents’ drinking water (SN: 7/21/18, p. 28). Metropolitan Books, $30

The Poison Squad
Deborah Blum

A Pulitzer Prize–winning journalist tells the story of a government chemist at the turn of the 20th century and his mission to make food safe in the United States. Penguin Press, $28

Aroused
Randi Hutter Epstein

The history of endocrinology makes for a strange and fascinating read, from the scientists who discovered the effects of hormones to the people whose lives have been irrevocably changed by these powerful substances (SN: 7/7/18, p. 28). W.W. Norton & Co., $26.95

Nine Pints
Rose George

Blood, the feared as well as revered substance that flows throughout the human body, has a rich historical and scientific past (SN: 10/27/18, p. 28). Metropolitan Books, $30

She Has Her Mother’s Laugh
Carl Zimmer

This comprehensive history recounts how researchers have come to understand genetic inheritance. Looking to the future, the author considers risks of gene manipulation (SN: 6/9/18, p. 29). Dutton, $30

Genetics in the Madhouse
Theodore M. Porter

Using archival records, a science historian traces the origins of the study of human heredity to insane asylums in the 1800s (SN: 7/7/18, p. 29). Princeton Univ., $35

The Tangled Tree
David Quammen

In chronicling the lives of researchers who made important advances in molecular biology and genetics, this book shows how recent findings shake up our understanding of evolution and the tree of life. Simon & Schuster, $30

An orbital oopsie has led to new proof of Albert Einstein’s physics prowess.

In 2014, two satellites intended for Europe’s Galileo network, the equivalent of the United States’ GPS network, were placed into orbit incorrectly, causing them to travel around Earth in ellipses rather than circles. That wasn’t ideal for the satellites’ originally intended navigational use, but scientists realized the wayward satellites were perfect for another purpose: testing Einstein’s theory of gravity, the general theory of relativity.

According to general relativity, gravity affects not just space, but also time. The deeper within a gravitational field you are, the slower time passes (SN: 10/17/15, p. 16). So a clock at a higher altitude will tick faster than one closer to Earth’s surface, where Earth’s gravity is stronger. The satellites’ orbital mishap allowed the most precise test yet of this effect, known as gravitational redshift, two teams of scientists report in a pair of papers in the Dec. 7 Physical Review Letters.

As the two misplaced satellites move in their elliptical orbits, their distance from Earth periodically increases and decreases by about 8,500 kilometers. Using the precise atomic clocks on the satellites, the scientists studied how that altitude change affected the flow of time. The clocks sped up and slowed down by tiny fractions of a second as expected, agreeing with the predictions of general relativity within a few thousandths of a percent, the teams report.

SEATTLE — The next generation exoplanet hunter is coming into its own. NASA’s Transiting Exoplanet Survey Satellite, or TESS, has already found eight confirmed planets in its first four months of observing — and some are unlike anything astronomers have seen before.

“The torrent of data is starting to flow already,” TESS principal investigator George Ricker of MIT said January 7 in a news conference at a meeting of the American Astronomical Society.

TESS launched in April and began science observations in July (SN: 5/12/18, p. 7). It was designed to be a follow-up to the prolific Kepler space telescope, which went dark in October after almost a decade of observing (SN Online: 10/30/18). Like Kepler, TESS searches for planets by watching for dips in starlight as planets cross, or transit, in front of their stars.
Unlike Kepler, which stared unblinkingly at a single patch of sky for years, TESS scans a new segment of sky every month. Over two years, TESS will cover the entire 360 degrees of sky visible from Earth’s orbit.

In the first four segments, TESS has already spotted eight confirmed planets and more than 320 unconfirmed candidates, said Xu Chelsea Huang of MIT. And several of them are downright strange.
Take the third-found planet, HD 21749b. Only 52 light-years away, it has the lowest temperature known for a planet orbiting a bright, nearby star, astronomers reported at the meeting and in a paper posted at arXiv.org on January 1.
That makes it a great candidate for follow-up observations with future telescopes like the James Webb Space Telescope, scheduled to launch in 2021. Webb will use starlight filtering through the atmospheres of planets like this one to measure those atmospheres’ properties and search for signs of life (SN: 4/30/16, p. 32).

“If we want to study atmospheres of cool planets, this is the one to start with,” Huang said.

“Cool” is a relative term. This particular planet is still probably too hot and gassy to host life. Its orbit takes 36 Earth days, the longest known orbital period for planets transiting bright stars within 100 light-years of the sun.

That leaves it at a distance from the star that should heat the planet’s surface to about 150° Celsius, too hot for liquid water. And at 2.84 times Earth’s size and 23.2 times Earth’s mass, its density suggests it must have a thick atmosphere, unlike Earth’s life-friendly one.

But it’s still worth checking out, says astronomer Diana Dragomir of MIT, a member of the TESS team. Despite its heat, this planet is “tepid” compared with most of the scorched worlds whose atmospheres astronomers can probe right now, she says, so closer to an Earthlike system. Smaller, cooler, more Earthlike worlds are few and far between, and may not orbit such bright stars.

Finding more longer-period planets “helps you explore the diversity of planets that are out there,” says astronomer Paul Dalba of the University of California, Riverside, who studies exoplanet atmospheres but was not involved in the TESS discovery. Because TESS spends such a short stretch of time looking at each segment of the sky, astronomers expect most of its planets to have shorter years than an Earth month. “The fact that we’re already getting one that’s longer period I think is just really exciting, showing that TESS isn’t just for the shortest-period exoplanets.”
The other planets in TESS’s first haul are equally exotic. TESS’s first find, Pi Mensae c, was reported in September ( SN Online: 9/18/18 ). The planet orbits its star every 6.27 days, and is about 2.14 times Earth’s size and 4.8 times Earth’s mass, giving it a density similar to pure water.
The weirdest thing about that super-Earth is the company it keeps, Huang said. Previous observations showed that the star Pi Mensae also has a planet 10 times the mass of Jupiter that orbits every 5.7 years. That planet, Pi Mensae b, revolves on a wildly eccentric orbit, swinging between the distance of Earth and the distance of Jupiter from its star.

“This is the most extreme system we know of that has this type of architecture,” Huang said.

Theories of how planets develop such wonky orbits suggest that this super-Jupiter should have booted Pi Mensae c out of the system (SN: 5/12/18, p. 28). “We are really surprised that the inner super-Earth actually survived that disruptive event,” Huang said. “It’s a mystery we really want to understand.”

The second planet found by TESS, LHS 3844b, has a radius just 1.3 times Earth’s. But it swings around its star every 11 hours, giving it a surface temperature of about 540° C, Huang said. “It’s likely a lava world.”

TESS has completed about one-twelfth of its first sky survey, but Ricker is already writing proposals to extend its initial two-year mission. TESS’s orbit is held stable by the moon’s gravity, so it doesn’t need to spend any fuel to stay put. The fuel on board, used to change the direction the telescope points, is enough to last for 300 years.

“The orbit itself was designed to be extremely stable on timescales of decades to centuries,” Ricker said. “TESS is really going to be an important part of our astronomical efforts for the next decade and for more to come.”

Editor’s note: This story was updated January 29, 2019, to correct the description of the planet LHS 3844b’s orbit. It orbits a star, not a planet.

Poop contains a lot of valuable scientific information. Researchers can monitor microbes, track enzyme activity or hunt for DNA to gather clues about overall health.

There’s so much one can learn from the waste product that microbiologist Aadra Bhatt at the University of North Carolina at Chapel Hill decided there should be a word for that research — something in the same vein as “in vivo” (research done in living animals) and “in vitro” (research done in a petri dish).

After some linguistic digging, she and two colleagues settled on “in fimo.” The term comes from fimus, one of several Latin words for manure or excrement. Their choice won out over the more obvious option of “in feces” because the word feces doesn’t have the same rich scatological legacy — originally it referred to the dregs in a wine cask, Bhatt says.

She and her colleagues, while already using in fimo at meetings and seminars, published their argument online December 13 in Gastroenterology. Compared with the laborious process of pulling together a scientific paper, coming up with this term was “delightful — and it wasn’t particularly drawn out,” Bhatt says. She hopes the word catches on and gains a place in the lexicon for poopetuity.

SEATTLE — Astronomers have spotted a second repeating fast radio burst, and it looks a lot like the first. The existence of a second repeating burst suggests there could be many more of the mysterious signals in the cosmos.

The burst, called FRB 180814.J0422+73, is one of 13 newly discovered fast radio bursts, or FRBs — brief, bright signals of radio energy that come from distant galaxies. The FRBs were detected over a few weeks last year by the Canadian Hydrogen Intensity Mapping Experiment, or CHIME, in British Columbia. Astronomers reported the discoveries at a meeting of the American Astronomical Society on January 7 and in the Jan. 9 Nature.
Most such bursts erupt once, last for a few milliseconds, and are never seen again. So astronomers have puzzled over what causes them for years (SN: 8/9/14, p. 22).

“If you have something that flashes for a millisecond in the sky, and there’s nothing that happens for many years, it’s really hard to study,” says astronomer Shriharsh Tendulkar of McGill University in Montreal, a member of the CHIME team.

But then in 2016, astronomers discovered the first repeating FRB when they realized that a series of bursts all came from a single source, called FRB 121102 (SN: 4/2/16, p. 12). Astronomers tracked the signal to its host galaxy (SN: 2/4/17, p. 10) and determined it was coming from an extremely magnetic environment, such as the region surrounding a black hole (SN: 2/3/18, p. 6). Researchers didn’t know if FRB 121102’s repeating signal was unique. Of the more than 60 FRBs detected, no other was known to repeat — until now. Having spotted a second one, scientists are searching for more.

“Imagine you saw a unicorn,” Tendulkar says. “Then suddenly you discover another one. You know now there is a population of these. There is hope for discovering a lot more.”
The CHIME team detected the first of the repeating FRB signals on August 14, with four more coming over the next two months from the same spot on the sky. It wasn’t until the third burst, on September 17, that the team realized they might have a repeater, Tendulkar says.

“Somebody pointed out, hey look, these three bursts seem to have the same properties,” he says. “Everybody got really excited.”

Calculations show that the new repeater is about 1.6 billion light-years away. The CHIME team also saw an odd similarity between the two known repeating bursts. Most FRBs are just a sharp blip, akin to a single note being played on a trumpet. But some of the individual bursts in both repeaters were made up of multiple sub-bursts that descended in frequency, like the “wah wah wah wah” of a sad trombone.

“We’ve seen this in 121102, and we can’t explain it,” says astronomer Emily Petroff of ASTRON, the Netherlands Institute of Radio Astronomy, who was not involved in the new work. “Up until now we’ve only had the one repeater, and it’s given us more questions than answers.” But the fact that both repeaters behave similarly could suggest they have similar origins, she says.

Astronomers may have already caught a third repeating burst, too. FRB 110523, discovered in 2015, has some similar features to the first known repeating FRB, so it was worth checking to see if it also repeats, said astronomer Allison McCarthy of the University of Alabama in Tuscaloosa.

Together with Andrew Seymour of the Green Bank Observatory in West Virginia, McCarthy analyzed more than 41 hours of observations of FRB 110523 taken at the Arecibo Observatory in Puerto Rico. They found one potential repeat burst, McCarthy reported January 9 in a poster at the AAS meeting, but they’re not declaring victory just yet. “It wasn’t strong enough for us to be very sure we had detected one,” McCarthy said, adding that they’re about 60 percent certain. “But it’s still a promising candidate.”

Astronomers’ theories for what causes FRBs are almost as numerous as known FRBs themselves. At one point, astronomers even considered the idea that FRBs could be signals from intelligent aliens. But it’s unclear if the repeating bursts and single bursts both come from the same kinds of sources, or even if one-offs might also repeat if watched for long enough.

“It’s the wild, wild west out there,” Tendulkar says. “We have tantalizing clues, but it’s hard to make definitive conclusions.”

CHIME is likely to catch a lot more of these fast radio bursts. The telescope was still being tested when it caught the 13 new ones, so was not operating at peak performance. “They just barely turned on the telescope,” Petroff says, “and they’re already finding things.”

SAN FRANCISCO — Seizures during sleep can scramble memories — a preliminary finding that may help explain why people with epilepsy sometimes have trouble remembering.

The sleeping brain normally rehashes newly learned material, a nocturnal rehearsal that strengthens those memories. Neuroscientist Jessica Creery and her colleagues forced this rehearsal by playing certain sounds while nine people with epilepsy learned where on a screen certain pictures of common objects were located. Then, while the subjects later slept, the researchers played the sounds to call up some of the associated memories.

This sneaky method of strengthening memories, called targeted memory reactivation, worked as expected for five people who didn’t have seizures during the process. When these people woke up, they remembered the picture locations reactivated by a tone better than those that weren’t reactivated during sleep, said Creery, of Northwestern University in Evanston, Ill. She presented the research March 25 at the annual meeting of the Cognitive Neuroscience Society.

The opposite was true, however, for four people who had mild seizures, detected only by electrodes implanted deep in the brain, while they slept. For these people, memory reactivation during sleep actually worsened memories, making the reactivated memories weaker than the memories that weren’t reactivated during sleep. The combination of seizures and memory reactivation “seems like it’s actually scrambling the memory,” Creery says, a finding that suggests that seizures somehow accelerate forgetting.