The Weather application is seen on an iPhone in this photo illustration on January 29, 2019. (Photo by Jaap Arriens/NurPhoto via Getty Images)
NurPhoto via Getty Images
You get bombarded with a ton of questions when people find out you’re a weather enthusiast. Most of them are easy—“will it rain tomorrow?” and, if they’re feeling feisty, “how much do you get paid to be wrong?”—but the most common question by far is “what weather app do you use?” I use just a couple of simple apps to stay on top of the weather when I’m not at my computer. You’ve probably got a few on your phone right now.
It’s easy to assume that folks who love the weather have a treasure trove of secret weather apps that they keep from the masses, like it’s a produce department and we’re hogging all the good bananas for ourselves. The truth is that most of us weather nerds use the apps everyone else has on our phones. It’s all about how you use the data available to you.
Forecasts: Google’s Default Weather App
Yes, “Google’s default weather app.” No, I’m not kidding. Meteorologists and weather buffs get so riled up over weather apps that we don’t stop to consider where those forecasts come from. Some apps aren’t always clear about where they source their forecasts.
I’m fine with the default weather app on my phone—which is helpfully titled “Weather” with a little Google logo over the sun—because I know the forecasts are generated by The Weather Channel. It says so right at the bottom of the app. And almost every reputable app is clear about where they get their data.
Apps aren’t inherently bad if they use good data. What’s bad is relying solely on an app for all of your weather info. Apps are intended for weather at a glance. They tell you the temperature and the chance of precipitation, but that’s it. You can miss important context like the chance for severe weather or a hurricane on an uncertain track.
It’s okay to use the weather app on your phone—that is, as long as you know where the data comes from and you seek out additional context from trustworthy voices like local television meteorologists on social media.
Alerts: The Weather Channel
Weather alerts are tricky. Just about every weather app on my phone sends me alerts—and I even subscribe to a free service that sends texts and emails and phone calls, too. My phone sounds like a slot machine whenever I wind up under a tornado warning.
I judge weather alerts by their reliability and speed. Most of my alerts come within a few minutes of their issuance by the National Weather Service, but The Weather Channel’s app sends the push notification to my phone right away. Sometimes, I get the alert before my actual NOAA Weather Radio goes off.
Radar: Radarscope
Radar is a tough nut to crack on your mobile device. Services have to straddle the line between “too much data for the average user” and “so little data that it’s not helpful.” Most radar data is okay at a glance if you want to know if it’s going to rain or if you really did just hear thunder in the distance.
Radarscope is by far the best radar app out there. Not only does the app give you high-resolution radar imagery for every radar site in the United States (and some in Canada!), but the app also gives you access to the full suite of radar products—precipitation, wind, and “dual-pol” data that lets you differentiate between different types of precipitation.
Unfortunately, Radarscope isn’t free—it costs $9.99—but it’s worth it if you’re serious about wanting to stay ahead of storms heading your way.
Shortcut: NWS Bookmarks
The National Weather Service doesn’t have its own mobile app, but that doesn’t mean that you can’t keep your local NWS forecast on your home screen. Most mobile browsers allow you to add bookmarks directly to your home screen. This nifty feature allows you to add your town’s NWS forecast directly on the home screen—bypassing other apps and the agency’s lack of one.
Back in 1976, the late Carl Sagan sat down on the Tonight Show with Johnny Carson to talk about a new form of space propulsion called solar sailing. Four decades later, and The Planetary Society has officially demonstrated this "tremendously exciting prospect" in practice.
Drawing on ten years of hard work and 7 million dollars in crowdfunding, the nonprofit Society's LightSail 2 has become the first small spacecraft to raise its orbit solely on the power of sunlight.
"We're thrilled to announce mission success for LightSail 2," says Bruce Betts, LightSail program manager and the Society's chief scientist.
"Our criteria was to demonstrate controlled solar sailing in a CubeSat by changing the spacecraft's orbit using only the light pressure of the Sun, something that's never been done before."
The LightSail 2 spacecraft has been up in orbit for over a month, and last week, it opened its sails for the first time. In the eight days or so since, the spacecraft has raised its orbit by 1.7 kilometres, pushed along solely by the Sun's photons, which 'bounce off' its reflective sails.
(The Planetary Society)
Following Japan's IKAROS solar sail, which was launched in 2010, LightSail 2 is only the second-ever successful attempt at solar flying. Yet unlike IKAROS, it can use this new form of propulsion to actually change its orbit.
According to project manager Dave Spencer, LightSail 2 is being controlled autonomously by an on-board algorithm. By twisting the spacecraft 90 degrees every 50 minutes, this software can alter the craft's orientation, so that it gets enough energy from the Sun no matter where it is. IKAROS, in comparison, could only turn about four or five degrees.
This impressive algorithm is still being updated and tweaked. One of the biggest challenges so far has been refining the spacecraft's momentum, which is controlled by a spinning wheel.
This momentum wheel is used to change the craft's orientation so that it turns the thrust from solar sailing on and off. When the wheel starts approaching maximum speed, which it does a couple times per day, it needs to be slowed down.
This is currently done using electromagnetic torque rods, which orient the spacecraft using Earth's magnetic field. Unfortunately, this temporarily takes the spacecraft out of its proper orientation for solar sailing, so scientists are still trying to figure out how to reduce these saturation points as much as possible. A software patch for this very issue was uploaded today.
"We are learning a lot from LightSail 2 right now," said Bill Nye, the CEO of The Planetary Society, during a recent press conference.
"In other words, although we've declared mission success, and we did this thing that we have been hoping to do for - depending on how you reckon - 42 years, LightSail 2 will fly for almost another year... We are going to learn a lot about controlling the spacecraft and the performance of the sails in the next few months."
(The Planetary Society)
It's hard to predict exactly how much further the spacecraft will be able to raise its orbit. Prelaunch simulations predicted that as solar propulsion adds up, it would increase the craft's orbit by about half a kilometre per day.
In the end, this wasn't too far off the mark; in fact, the spacecraft increased by around 900 metres (2,950 ft) just the other day.
But just as there's a lower limit to the spacecraft's orbit, there's also an upper limit.
"The atmospheric density at those altitudes is really poorly modelled and highly variable, and so we don't really know at what point atmospheric drag is going to overcome our ability to continue orbit raising," explained Spencer in the press briefing.
"So we'll keep doing this as long as we can."
The applications for this technology are limitless, and scientists have proposed using it in the search for alien life, monitoring weather on the Sun and as a warning system for incoming asteroids.
There's even a dream that if a material can be found that tolerates high heat and radiation, a solar-sailing spacecraft could creep really close to the Sun, receiving a huge thrust that would ultimately allow it to travel much farther and at much higher speeds.
"This technology enables us to take things to extraordinary destinations in the Solar System and maybe even beyond, in a way that was never possible before," Nye said in the briefing, "because you don't need fuel, you don't need all the systems to control fuel, manage fuel and buy fuel."
NASA's Near-Earth Asteroid Scout, which is set to launch sometime in mid 2020, is probably the earliest application for this new technology. The bold mission plans to use a solar sail and a 6U CubeSat, or miniaturised spacecraft, to gather data on nearby asteroids that hold potential for future human missions.
"Some of the very early concepts for solar sailing missions had large spacecrafts and enormous sails," Spencer explained in the briefing.
"But what's really interesting is that in the last decade or so, it's been the CubeSat revolution where the technology has gotten so small that has allowed solar sailing to really take the forefront and be developed as a source of in space propulsion for these tiny spacecraft."
Facebook is developing a brain-computer Augmented Reality (AR) interface device that would help users type with their mind.
At its F8 Developers' Conference in 2017, the company announced its Brain-Computer Interface (BCI) programme -- outlining its goal to build a non-invasive, wearable device that lets people type by simply imagining themselves talking.
Facebook is supporting a team of researchers at University of California, San Francisco (UCSF) who are working to help patients with neurological damage speak again by detecting intended speech from brain activity in real time.
In a paper appeared in the journal Nature Communications, the UCSF team "has shared how far we have to go to achieve fully non-invasive BCI as a potential input solution for AR glasses", said Facebook in a blog post on Tuesday.
The UCSF team has been able to decode a small set of full, spoken words and phrases from brain activity in real time -- a first in the field of BCI research.
The researchers emphasise that their algorithm is so far only capable of recognising a small set of words and phrases, but ongoing work aims to translate much larger vocabularies with dramatically lower error rates.
"The promise of AR lies in its ability to seamlessly connect people to the world that surrounds them and to each other. Rather than looking down at a phone screen or breaking out a laptop, we can maintain eye contact and retrieve useful information and context without ever missing a beat," Facebook added.
As Chief Scientist Michael Abrash and the team at Facebook Reality Labs (FRL) see it, "we are standing on the edge of the next great wave in human-oriented computing, one in which the combined technologies of AR and VR converge and revolutionise how we interact with the world around us".
"It is going to be something completely new, as clean a break from anything that has come before as the mouse/GUI-based interface was from punch cards, printouts, and teletype machines," said Abrash.
The aim of the BCI research programme at Facebook Reality Labs is to develop a non-invasive, silent speech interface that will let people type just by imagining the words they want to say - a technology that could one day be a powerful input for all-day wearable AR glasses
Ultimately, the researchers hope to reach a real-time decoding speed of 100 words per minute with a 1,000-word vocabulary and word error rate of less than 17 per cent.
Facebook first announced in 2017 that its research lab, Building 8, was working on a computer-brain interface.
The Facebook programme comes on the heels of Elon Musk-led startup Neuralink's bold research that has revealed tiny brain "threads" in a chip which is long lasting, usable at home and has the potential to replace cumbersome devices currently used as brain-machine interfaces.
In 1970, the Indian government planned to flood 8.3 square kilometers of pristine evergreen tropical forest by building a hydroelectric plant to provide power and jobs to the state of Kerala. And they would have succeeded—if it weren’t for a burgeoning people’s science movement, buttressed by a pioneering female botanist. At 80 years old, Janaki Ammal used her status as a valued national scientist to call for the preservation of this rich hub of biodiversity. Today Silent Valley National Park in Kerala, India, stands as one of the last undisturbed swaths of forest in the country, bursting with lion-tailed macaques, endangered orchids and nearly 1,000 species of endemic flowering plants.
Sometimes called “the first Indian woman botanist,” Ammal leaves her mark in the pages of history as a talented plant scientist who developed several hybrid crop species still grown today, including varieties of sweet sugarcane that India could grow on its own lands instead of importing from abroad. Her memory is preserved in the delicate white magnolias named after her, and a newly developed, yellow-petaled rose hybrid that now blooms in her name. In her later years, she became a forceful advocate for the value and preservation of India’s native plants, earning recognition as a pioneer of indigenous approaches to the environment.
Edavaleth Kakkat Janaki Ammal was born in 1897, the tenth in a blended family of 19 brothers and sisters in Tellicherry (now Thalassery) in the Indian state of Kerala. Her father, a judge in a subordinate court system in Tellicherry, kept a garden in their home and wrote two books on birds in the North Malabar region of India. It was in this environment that Ammal found her affinity for the natural sciences, according to her niece, Geeta Doctor.
As she grew up, Ammal watched as many of her sisters wed through arranged marriages. When her turn came, she made a different choice. Ammal embarked on a life of scholarship over one of matrimony, obtaining a bachelor’s degree from Queen Mary’s College, Madras and an honors degree in botany from the Presidency College. It was rare for women to choose this route since women and girls were discouraged from higher education, both in India and internationally. In 1913, literacy among women in India was less than one percent, and fewer than 1,000 women in total were enrolled in school above tenth grade, writes historian of science Vinita Damodaran (and Ammal’s distant relative) in her article “Gender, Race, and Science in Twentieth-Century India.”
After graduating, Ammal taught for three years at the Women’s Christian College in Madras before receiving a unique opportunity: to study abroad for free through the Barbour Scholarship, established at the University of Michigan by philanthropist Levi Barbour in 1917 for Asian women to study in the U.S. She joined the botany department as Barbour Scholar at Michigan in 1924. Despite coming to America on a prestigious scholarship, Ammal, like other travelers from the East, was detained in Ellis Island until her immigration status was cleared, her niece writes. But mistaken for an Indian princess with her long dark hair and traditional dress of Indian silks, she was let through. When asked if she was in fact a princess, “I did not deny it,” she said.
During her time at the University of Michigan she focused on plant cytology, the study of genetic composition and patterns of gene expression in plants. She specialized in breeding interspecific hybrids (produced from plants of a different species) and intergeneric hybrids (plants of a different genera within the same family). In 1925, Ammal earned a Masters of Science. In 1931, she received her doctorate, becoming the first Indian woman to receive that degree in botany in the U.S.
Her expertise was of particular interest at the Imperial Sugar Cane Institute in Coimbatore, now the Sugarcane Breeding Institute. The Institute was trying to bolster India’s native sugarcane crop, the sweetest species of which (Saccharum officinarum) they had been importing from the island of Java. With Ammal’s help, the Institute was able to develop and sustain their own sweet sugarcane varieties rather than rely on imports from Indonesia, bolstering India’s sugarcane independence.
Ammal’s research into hybrids helped the Institute identify native plant varieties to cross-breed with Saccharum in order to produce a sugar cane crop better suited for India’s tropical environmental conditions. Ammal crossed dozens of plants to determine which Saccharum hybrids yielded higher sucrose content, providing a foundation for cross-breeding with consistent results for sweetness in home-grown sugarcane. In the process, she also developed several more hybrids from crossing various genera of grasses: Saccharum-Zea, Saccharum-Erianthus, Saccharum-Imperata and Saccharum-Sorghum.
In 1940, Ammal moved to Norfolk, England, to begin work at the John Innes Institute. There she worked closely with geneticist—and eugenicist—Cyril Dean Darlington. Darlington researched the ways that chromosomes influenced heredity, which eventually grew into an interest in eugenics, particularly the role of race in the inheritance of intelligence. With Ammal, however, he mostly worked on plants. After five years of collaboration, the pair coauthored the Chromosome Atlas of Cultivated Plants, which is still a key text for plant scientists today. Unlike other botanical atlases that focused on botanical classification, this atlas recorded the chromosome number of about 100,000 plants, providing knowledge about breeding and evolutionary patterns of botanical groups.
In 1946, the Royal Horticultural Society in Wisley offered Ammal a paid position as a cytologist. She left the John Innes Institute and became the Society’s first salaried woman staff member. There, she studied the botanical uses of colchicine, a medication that can double a plant’s chromosome number and result in larger and quicker-growing plants. One of the results of her investigations is the Magnolia kobus Janaki Ammal, a magnolia shrub with flowers of bright white petals and purple stamens. Though Ammal returned to India around 1950, the seeds she planted put down roots, and the world-renowned garden at Wisley still plays host to Ammal’s namesake every spring when it blooms.
A rose hybrid named in "E.K. Janaki Ammal" in honor of Ammal's life and work.
(John Innes Centre U.K.)
When she returned to India in the early 1950s, she did so at the request of Jawaharlal Nehru, India’s first Prime Minister after their 1947 independence from British rule. India was recovering from a series of famines, including the Bengal famine of 1943 that killed millions. It was for this reason, Vinita Damodaran tells Smithsonian, that “Nehru was very keen to get [Ammal] back [to India] to improve the botanical base of Indian agriculture.” Nehru made her a government appointed supervisor in charge of directing the Central Botanical Laboratory in Lucknow. In this capacity, she would reorganize the Botanical Survey of India (BSI), originally established in 1890 under the oversight of Britain’s Kew Gardens to collect and survey India’s flora.
But Ammal found herself dissatisfied with some of the initiatives that the government had implemented to boost India’s food production. Under the 1940s Grow More Food Campaign, the government reclaimed 25 million acres of land for the cultivation of food, mostly grain and other cereals. “She found the deforestation was getting quite out of hand, quite rampant,” Damodaran says. Damodaran reads from a letter that Ammal sent to Darlington in which she expressed her distress over the extent to which deforestation was destroying India’s native plants: “I went 37 miles from Shillong in search of the only tree of Magnolia griffithii in that part of Assam and found that it had been burnt down.”
At this point, Ammal’s work took a decidedly different turn. After spending decades applying her skills to improving the commercial use of plants, she began using her influence to preserve indigenous plants under threat. One of Ammal’s goals for the botanical survey was to house plant specimens that had been collected from across the continent in an herbarium in India. She wanted the BSI to be conducted by Indian scientists and kept for India. But in the 60 years since the British first controlled the BSI, she found not much had changed when the government appointed a European, Hermenegild Santapau, as her director, a position that Damodaran says Ammal “felt had been unjustly denied her.”
In another letter to Darlington she expressed both anger and sadness at the decision to appoint Hermenegild. “I bring you news of a major defeat for botanical science in India,” she wrote. “The Govt. of India has appointed as the chief botanist of India—a man with the Kew tradition and I—the director of the Central Botanical Laboratory must now take orders from him ... Kew has won … and we have lost.” Despite India’s independence from British rule, Britain’s colonization of the country manifested in science.
Ammal believed a truly systematic study of India’s flora could not be done if the specimens were collected by foreign botanists and then studied only in British herbaria. Damodaran explains, “This was critical to her: how do you create a revitalized botanical survey, in terms of both collection and research, that enables you to do this new flora?”
To that end Ammal issued a memorandum on the survey, writing, “The plants collected in India during the last thirty years have been chiefly by foreign botanists and often sponsored by institutions outside India. They are now found in various gardens and herbaria in Europe, so that modern research on the flora of India can be conducted more intensely outside India than within this country.”
This continues to be a problem today. “The largest collection of Indian plants are held there [at the Kew and the Natural History Museum],” Damodaran says, “It’s still quite an imperial institution.”
To preserve Indian plants, Ammal saw the need to value the indigenous knowledge about them. In 1955 she was the only woman to attend an international symposium in Chicago, ironically entitled Man’s Role in Changing the Face of the Earth. The Symposium interrogated the various ways that humans were changing the environment in order “to keep abreast of all the means at man’s disposal to affect deliberately or unconsciously the course of his own evolution.” In the room full of mostly white men, she spoke about India’s subsistence economy, the significance of tribal cultures and their cultivation of native plants, and the importance of Indian matrilineal traditions that valued women as managers of property, including a family’s plants—all of which were threatened by the mass-production of cereals.
“It is in this sense,” Damodaran writes, “that one can see Janaki Ammal as pioneering both indigenous and gendered environmental approaches to land use whilst continuing to be a leading national scientist.”
In the later years of her career, Ammal lent her voice to a booming environmental movement called Save Silent Valley, a campaign to stop a hydroelectric project that would flood the Silent Valley forests. By the time she joined protesters and activists, she was an established voice in Indian science, and a scientist emeritus at Madras University’s Centre for Advanced Studies in Botany. Joining the movement was a natural outgrowth of her previous decades of work, bringing full circle a scientific life of systematic study and a love of the natural wonders of her country. “I am about to start a daring feat,” she wrote, again to Darlington. “I have made up my mind to take a chromosome survey of the forest trees of the Silent Valley which is about to be made into a lake by letting in the waters of the river Kunthi.”
Harnessing her scientific expertise, she spearheaded the chromosomal survey of the Valley plants in an effort to preserve the botanical knowledge held there. As part of the larger movement, one of the most significant environmental movements of the 1970s, Ammal was successful: the government abandoned the project, and the forest was declared a national park on November 15, 1984. Unfortunately, Ammal was no longer around to see the triumph. She had died nine months earlier, at 87 years old.
In a 2015 article remembering her aunt, Greeta Doctor wrote that Ammal never liked to talk about herself. Rather, Ammal believed that “My work is what will survive.” She was right: though she is relatively unknown in her country, her story is out there, written in the pages of India’s natural landscape. From the sweetness of India’s sugar and the enduring biodiversity of the Silent Valley to Wiseley’s blooming magnolias, Ammal’s work does not just survive, it thrives.
This video from the Glenn Research Center highlights in stunning, behind-the-scenes imagery the launches of three space shuttle missions: STS-114, STS-117, and STS-124. NASA engineers provide commentary as footage from the ground and from the orbiters themselves document in detail the first phase of a mission.
Some 2,200 years ago, a group of Iron Age Celts laid a woman to rest in what is now Zürich, Switzerland.
The deceased, clad in a dress of fine sheep’s wool, a shawl and a sheepskin coat, was likely an individual of high stature: As a statement recently released by the city’s Office for Urban Development notes, the woman, roughly 40 years old when she died, boasted accessories including a necklace made of blue and yellow glass and amber, bronze bracelets, and a bronze belt chain decorated with pendants.
Based on analysis of her remains, archaeologists theorize she performed little physical labor during her lifetime and enjoyed a rich diet of starchy and sweetened foods. Curiously, Laura Geggel writes for Live Science, the woman was also buried in a hollowed-out tree trunk that still had bark on its exterior upon the makeshift coffin’s rediscovery in March 2017.
Reconstruction of the breast decoration with glass beads and brooches
(Office for Urban Development, City of Zurich)
Per a statement published in the immediate aftermath of the find, workers happened upon the gravesite while undertaking a construction project at the Kern school complex in Zürich’s Aussersihl district. Although the site is considered of archaeological importance, most previous discoveries dated to the 6th century A.D.
The only exception, according to Geggel, was the grave of a Celtic male found on the campus in 1903. Like the woman, who was buried about 260 feet away, the man showed signs of high social standing, wielding a sword, shield and lance and wearing a complete warrior outfit. Given the fact that the pair were both buried around 200 B.C., the Office for Urban Development suggests it is “quite possible” they knew each other.
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Block recovery of the breast decoration with glass beads and brooches
(Martin Bachmann, Kantonsarchäologie Zürich)
According to the 2017 statement, researchers launched a comprehensive assessment of the grave and its occupant soon after the discovery. For the past two years, archaeologists have documented, salvaged, conserved and evaluated the various goods found in the tomb, as well as conducting a physical examination of the woman’s remains and performing isotope analysis of her bones.
Uncovered grave with jewelry and gifts
(Office for Urban Development, City of Zurich)
The now-completed assessment “draws a fairly accurate picture of the deceased” and her community, per the statement. Isotope analysis reveals that the woman grew up in what is now Zürich’s Limmat Valley, meaning she was buried in the same region she likely spent most of her life. While archaeologists have previously unearthed evidence of a nearby Celtic settlement dating to the 1st century B.C., the researchers believe that the man and woman actually belonged to a separate smaller settlement yet to be discovered.
Reconstruction of the grave with Baumsarg
(Photo: Amt für Städtebau, Stadt Zürich )
Life pictures of the Celtic and the Celts from the Kernstrasse in Zurich
(Photo: Office for Urban Development, City of Zurich)
Today, the Celts are often associated with the British Isles. In actuality, as Adam H. Graham reports for Afar magazine, Celtic clans spanned much of Europe, settling down in Austria, Switzerland and other areas north of the Roman Empire’s borders. From 450 B.C. to 58 B.C.—exactly the time period in which the tree coffin woman and her potential male companion lived—a “wine-guzzling, gold-designing, poly/bisexual, naked-warrior-battling culture” dubbed La Tène actually served as the nexus of the Celtic world, thriving in Switzerland’s Lac de Neuchâtel region.
Unfortunately for these hedonistic Celts, an invasion by Julius Caesar abrubtly ended the festivities, paving the way for Rome’s eventual subjugation of much of the European continent.
A team led by Princeton physicist Ali Yazdani has shown that strong electron interactions play a key role in the superconductivity that has been discovered in graphene, a material made up of single-layer sheets of carbon atoms. Here, two graphene sheets stacked on each other with a twist make a long-wavelength moiré pattern. Credit: Designed by Kai Fu for Yazdani Lab, Princeton University
In spring 2018, the surprising discovery of superconductivity in a new material set the scientific community abuzz. Built by layering one carbon sheet atop another and twisting the top one at a "magic" angle, the material enabled electrons to flow without resistance, a trait that could dramatically boost energy efficient power transmission and usher in a host of new technologies.
Now, new experiments conducted at Princeton give hints at how this material—known as magic-angle twisted graphene—gives rise to superconductivity. In this week's issue of the journal Nature, Princeton researchers provide firm evidence that the superconducting behavior arises from strong interactions between electrons, yielding insights into the rules that electrons follow when superconductivity emerges.
"This is one of the hottest topics in physics," said Ali Yazdani, the Class of 1909 Professor of Physics and senior author of the study. "This is a material that is incredibly simple, just two sheets of carbon that you stick one on top of the other, and it shows superconductivity."
Exactly how superconductivity arises is a mystery that laboratories around the world are racing to solve. The field even has a name, "twistronics."
Part of the excitement is that, compared to existing superconductors, the material is quite easy to study since it only has two layers and only one type of atom—carbon.
"The main thing about this new material is that it is a playground for all these kinds of physics that people have been thinking about for the last 40 years," said B. Andrei Bernevig, a professor of physics specializing in theories to explain complex materials.
The superconductivity in the new material appears to work by a fundamentally different mechanism from traditional superconductors, which today are used in powerful magnets and other limited applications. This new material has similarities to copper-based, high-temperature superconductors discovered in the 1980s called cuprates. The discovery of cuprates led to the Nobel Prize in Physics in 1987.
The new material consists of two atomically thin sheets of carbon known as graphene. Also the subject of a Nobel Prize in Physics, in 2010, graphene has a flat honeycomb pattern, like a sheet of chicken wire. In March 2018, Pablo Jarillo-Herrero and his team at the Massachusetts Institute of Technology placed a second layer of graphene atop the first, then rotated the top sheet by the "magic" angle of about 1.1 degrees. This angle had been predicted earlier by physicists to cause new electron interactions, but it came as a shock when MIT scientists demonstrated superconductivity.
Seen from above, the overlapping chicken-wire patterns give a flickering effect known as "moiré," which arises when two geometrically regular patterns overlap, and which was once popular in the fabrics and fashions of 17th and 18th century royals.
These moiré patterns give rise to profoundly new properties not seen in ordinary materials. Most ordinary materials fall into a spectrum from insulating to conducting. Insulators trap electrons in energy pockets or levels that keep them stuck in place, while metals contain energy states that permit electrons to flit from atom to atom. In both cases, electrons occupy different energy levels and do not interact or engage in collective behavior.
In twisted graphene, however, the physical structure of the moiré lattice creates energy states that prevent electrons from standing apart, forcing them to interact. "It is creating a condition where the electrons can't get out of each other's way, and instead they all have to be in similar energy levels, which is prime condition to create highly entangled states," Yazdani said.
The question the researchers addressed was whether this entanglement has any connection with its superconductivity. Many simple metals also superconduct, but all the high-temperature superconductors discovered to date, including the cuprates, show highly entangled states caused by mutual repulsion between electrons. The strong interaction between electrons appears to be a key to achieve higher temperature superconductivity.
To address this question, Princeton researchers used a scanning tunneling microscope that is so sensitive that it can image individual atoms on a surface. The team scanned samples of magic-angle twisted graphene in which they controlled the number of electrons by applying a voltage to a nearby electrode. The study provided microscopic information on electron behavior in twisted bilayer graphene, whereas most other studies to date have monitored only macroscopic electrical conduction.
By dialing the number of electrons to very low or very high concentrations, the researchers observed electrons behaving almost independently, as they would in simple metals. However, at the critical concentration of electrons where superconductivity was discovered in this system, the electrons suddenly displayed signs of strong interaction and entanglement.
At the concentration where superconductivity emerged, the team found that the electron energy levels became unexpectedly broad, signals that confirm strong interaction and entanglement. Still, Bernevig emphasized that while these experiments open the door to further study, more work needs to be done to understand in detail the type of entanglement that is occurring.
"There is still so much we don't know about these systems," he said. "We are nowhere near even scraping the surface of what can be learned through experiments and theoretical modeling."
Contributors to the study included Kenji Watanabe and Takashi Taniguchi of the National Institute for Material Science in Japan; graduate student and first author Yonglong Xie, postdoctoral research fellow Berthold Jäck, postdoctoral research associate Xiaomeng Liu, and graduate student Cheng-Li Chiu in Yazdani's research group; and Biao Lian in Bernevig's research group.
Citation: Experiments explore the mysteries of 'magic' angle superconductors (2019, July 31) retrieved 31 July 2019 from https://phys.org/news/2019-07-explore-mysteries-magic-angle-superconductors.html
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Harbor seals with tags (NMFS MMPA permit 16691). Credit: S. Steingass, 2019
Wearable devices fitted to harbor seals reveal their movements around the Oregon coast, for a population that has been increasing following the implementation of marine reserves and protection acts. The study publishes July 31, 2019 in the open-access journal PLOS ONE by Sheanna Steingass from Oregon State University, USA, and colleagues.
Approximately 10,000-12,000 harborseals, Phoca vitulina richardii, make the Oregon coast their home year-round—but there's little data on these seal populations. The authors of the present study investigated the ranges and habitats of these seals.
Steingass and colleagues fitted external satellite transmitters to 24 adult harbor seals from Alsea Bay and Netarts Bay in Oregon between September 2014 and April 2015. They collected location data every other month (in order to extend battery life) to evaluate and model the seals' movements, calculating each seal's home range (the area within which they spent 95 percent of their time) and core area (the smaller area where they were especially likely to stay). They also examined how seals used specific habitat and how frequently the seals spent time in five newly-established Oregon marine reserves.
The authors found the average home range for these seals was approximately 364 km2, though individual seals' home ranges varied greatly. The average calculated core area for seals encompassed on average 29.41 km2, though this also varied greatly.
Seals spent approximately 50 percent of their time in rivers, estuaries and bays, and were in the water (versus dry land) about 70 percent of the time. While they generally stayed close to the shore, when they did make open ocean trips, these lasted an average of around 22 hours. The seals in this study tended to use the marine reserve areas within their range only rarely, visiting them less than 2 percent of the time—the authors suspect this is due to the reserves' specific habitats.
As the first major documentation of space use of Oregon coast harbor seals in the last 30 years, this study enables further hypotheses and modelling of harbor seals in a future where marine areas are subject to frequent change.
The authors add: "Satellite tracking reveals at-sea habitat use for the first time for Pacific harbor seals in Oregon. Results from 24 seals demonstrate individual differences in behavior, with some study animals ranging hundreds of miles and few spending time within Oregon's marine reserves."
More information: Steingass S, Horning M, Bishop AM (2019) Space use of Pacific harbor seals (Phoca vitulina richardii) from two haulout locations along the Oregon coast. PLoS ONE 14(7): e0219484. doi.org/10.1371/journal.pone.0219484
Citation: Mapping Oregon coast harbor seal movements using wearable devices (2019, July 31) retrieved 31 July 2019 from https://phys.org/news/2019-07-oregon-coast-harbor-movements-wearable.html
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The Planetary Society has been busy recently. On June 25, its LightSail 2 launched into orbit; just last week on July 24, the craft opened its sails successfully, a key stage of its mission to demonstrate solar sailing in practice.
And now, the nonprofit foundation has released a statement, revealing that tomorrow (July 31), there is going to be a major announcement about LightSail 2; sounds like it could be something really exciting.
MEDIA ADVISORY: The Planetary Society to Announce Major Solar Sailing Milestone
The small LightSail 2 spacecraft is a crowd-funded endeavour, built to demonstrate controlled solar sailing - a promising method of propulsion that doesn't require fuel.
Instead, the craft hosts a large sail made out of a reflective material for photons emitted by the Sun to 'bounce' off of. Although photons - light particles - don't have mass, they do have momentum, and the hypothetical principles behind solar sails state that in the vacuum of space, even this small momentum can push the spacecraft forward.
So far, so good: LightSail 2 is currently drifting 720 km (420 miles) above Earth's surface, and over the next month the craft is expected to adjust its elliptical orbit by using the solar sail.
This is already exciting, but tomorrow at 5 pm UTC we can expect to hear a potentially major announcement from Bill Nye, the CEO of The Planetary Society, as well as three other scientists working for the foundation.
The solar sail deploying on LightSail 2. (The Planetary Society)
So far, it's anybody's guess what that announcement might bring; we've already received some stunning pictures of the solar sail deploying, so it won't be that.
They do tease that it's a 'major solar sailing milestone', so if that checks out, it will be one for the history books.
Watch this space, as we'll be sure to bring the news tomorrow as it happens!
This week, Tesla announced a utility-scale energy storage solution, to be called Megapack. Modeled after the giant battery system it built as part of the Hornsdale wind farm in South Australia, it can directly connect to renewable energy sources providing a constant source of power when the sun sets or the wind stops.
This system, called Powerpack, stored power generated by the wind farm and then delivered the electricity to the grid during peak hours. The facility saved nearly $40 million in its first year.
Tesla claims it can deploy a one gigawatt-hour plant over three acres in under three months, which is about four times faster than a comparable fossil fuel plant.
Concept illustration of the Megapack installed at a windfarm similar to Hornsdale
Tesla
This will be the third and largest energy storage system offered by Tesla. It also offer a residential-scale system called Powerwall and the commercial-scale version Powerpack. Tesla claims that Megapack will offer 60 percent greater energy density compared to it's existing Powerpack system.
This is the latest effort by the company to retool and grow its energy storage business, which is a smaller revenue driver than sales of its electric vehicles. Of the $6.4 billion in total revenue posted in the second quarter, just $368 million was from Tesla’s solar and energy storage product business.
Powerwalls are now installed at more than 50,000 sites and according to the company's second-quarter earnings report, it deployed a record 415 megawatt-hours of energy storage products in Q2, an 81% increase from the previous quarter.
It's a significant step forward company most known for the production of electric cars and that certainly benefits from its knowledge of battery technology. Back in 2006, Musk described Tesla’s “overarching purpose” is “to help expedite the move from a mine-and-burn hydrocarbon economy towards a solar electric economy, which I believe to be the primary, but not exclusive, sustainable solution.”
The Megapack could provide a much-needed boost to the company if it can convince utilities companies to opt for this solution rather than the more common natural gas peaker plants. These are used when a local utility grid can’t provide enough power to meet peak demand, an occurrence that has become more common as temperatures and populations rise.
So far, it seems to be successful as Tesla’s Megapack will provide 182.5 MW of the upcoming 567 MW Moss Landing energy storage project in California with PG&E.
As the need for greater, industrial-scale battery efficiency increases , this could turn into a competitive international industry
Tesla
Tesla hopes to be the sustainable alternative. And in states like California, which have ambitious emissions targets, Tesla could gain some ground. Instead of using a natural gas peaker plant, utilities could use the Megapack to store excess solar or wind energy to support the grid’s peak loads.
In fact, only yesterday, the Southern Californian city of Glendale announced it was dropping a gas peaker in favor of clean alternatives.
As GreenTechMediareported, the city council voted in April 2018 to pause development on the 262 megawatt repowering of the Grayson Power Plant and examine clean energy alternatives. Now, the municipal utility has completed an examination of 34 clean energy proposals and selected a diverse portfolio it says will meet reliability needs and save ratepayers $125 million.
The final portfolio, proposed in Glendale Water & Power's new integrated resource plan, would repower the Grayson Power Plant with a 75 megawatt/ 300 megawatt-hour Tesla battery installation and up to 93 megawatts of fast-ramping Wartsila engines.
This week, Tesla announced a utility-scale energy storage solution, to be called Megapack. Modeled after the giant battery system it built as part of the Hornsdale wind farm in South Australia, it can directly connect to renewable energy sources providing a constant source of power when the sun sets or the wind stops.
This system, called Powerpack, stored power generated by the wind farm and then delivered the electricity to the grid during peak hours. The facility saved nearly $40 million in its first year.
Tesla claims it can deploy a one gigawatt-hour plant over three acres in under three months, which is about four times faster than a comparable fossil fuel plant.
Concept illustration of the Megapack installed at a windfarm similar to Hornsdale
Tesla
This will be the third and largest energy storage system offered by Tesla. It also offer a residential-scale system called Powerwall and the commercial-scale version Powerpack. Tesla claims that Megapack will offer 60 percent greater energy density compared to it's existing Powerpack system.
This is the latest effort by the company to retool and grow its energy storage business, which is a smaller revenue driver than sales of its electric vehicles. Of the $6.4 billion in total revenue posted in the second quarter, just $368 million was from Tesla’s solar and energy storage product business.
Powerwalls are now installed at more than 50,000 sites and according to the company's second-quarter earnings report, it deployed a record 415 megawatt-hours of energy storage products in Q2, an 81% increase from the previous quarter.
It's a significant step forward company most known for the production of electric cars and that certainly benefits from its knowledge of battery technology. Back in 2006, Musk described Tesla’s “overarching purpose” is “to help expedite the move from a mine-and-burn hydrocarbon economy towards a solar electric economy, which I believe to be the primary, but not exclusive, sustainable solution.”
The Megapack could provide a much-needed boost to the company if it can convince utilities companies to opt for this solution rather than the more common natural gas peaker plants. These are used when a local utility grid can’t provide enough power to meet peak demand, an occurrence that has become more common as temperatures and populations rise.
So far, it seems to be successful as Tesla’s Megapack will provide 182.5 MW of the upcoming 567 MW Moss Landing energy storage project in California with PG&E.
As the need for greater, industrial-scale battery efficiency increases , this could turn into a competitive international industry
Tesla
Tesla hopes to be the sustainable alternative. And in states like California, which have ambitious emissions targets, Tesla could gain some ground. Instead of using a natural gas peaker plant, utilities could use the Megapack to store excess solar or wind energy to support the grid’s peak loads.
In fact, only yesterday, the Southern Californian city of Glendale announced it was dropping a gas peaker in favor of clean alternatives.
As GreenTechMediareported, the city council voted in April 2018 to pause development on the 262 megawatt repowering of the Grayson Power Plant and examine clean energy alternatives. Now, the municipal utility has completed an examination of 34 clean energy proposals and selected a diverse portfolio it says will meet reliability needs and save ratepayers $125 million.
The final portfolio, proposed in Glendale Water & Power's new integrated resource plan, would repower the Grayson Power Plant with a 75 megawatt/ 300 megawatt-hour Tesla battery installation and up to 93 megawatts of fast-ramping Wartsila engines.
Wild adult female Bengal tiger, Panthera tigris tigris, Kanha National Park (also known as Kanha Tiger Reserve), MP, India. (Credit: Charles J Sharp / Sharp Photography / CC BY-SA 4.0)
/ Sharp Photography via a Creative Commons license
The wonderful thing about tiggers Is tiggers are wonderful things!”
-- Lyrics from The Many Adventures of Winnie the Pooh Composed by Richard M. Sherman and Robert B. Sherman.
After coming close to being extinguished from the wild, India’s tiger population has more than doubled in 12 years, according to a summary report that was recently released by Narendra Modi, India’s Prime Minister (PDF). According to this report, wild tiger numbers increased in India from 1,411 in 2006 to an estimated 2,967 in 2018.
In 1900, there were more than 100,000 wild tigers, but by 2010 it was estimated there were just 3,200 -- an all-time low. This steep population decline motivated India and 12 other “tiger countries” to hold the Tiger Summit of St. Petersburg in 2010, where they agreed to double the wild tiger population by 2022. Because most of the wild tigers live in India, this country was responsible for making most of the hard choices. Nevertheless, India achieved this goal four years early.
“Once the people of India decide to do something, there is no force that can prevent them from getting the desired results,” India’s prime minister announced at a press conference. “Today we reaffirm our commitment towards protecting tigers.”
The Prime Minister added that India is “now one of the biggest and most secure habitats of the tiger”.
India’s tigers represent roughly 70% of the global tiger population.
A survey of wild tigers takes place in India every four years. The most recent tiger population numbers are based on a 15-month long census that took place between 2018-2019 across 380,000 km2 (146,000 square miles) of land, coordinated by the Wildlife Institute of India, an autonomous government institution under India’s Ministry of Environment, Forest and Climate Change. This estimate is based on numbers collected using a variety of methods, including dung counts, distance sampling where human volunteers counted tigers spotted along a specific route, satellite imagery, and camera traps (a total of 2,461 individual tigers that were one year of age or older were photographed by 26,000 camera traps in known tiger habitats), and adoption of new statistical methods to make better estimates.
Since 2006, tiger sightings increased at a rate of 6% per year in India.
The newly released report reveals that most states in India saw increases in tiger numbers: Madhya Pradesh (526) had the greatest number, followed by Karnataka (524) and Uttarakhand (442), whilst Chhattisgarh and Odisha reported decreases, and tiger reserves in Buxa, Dampa and Palamau reported no tigers at all.
“The poor and continuing decline in tiger status in the states of Chhattisgarh and Odisha is a matter of concern,” the authors noted in their report.
However, even as the numbers of wild tigers generally increased, the total area that they occupy decreased significantly from 88,000-89,000 km2 (54,680 square miles) in 2014 to 40,000 km2 (24,850 square miles) in 2018. According to the study’s authors, this loss in range was based on a lack of evidence for the presence of tigers, whereas a small portion resulted from a lack of sampling forests known to be occupied by tigers in 2014.
But the report also found that tigers are colonizing areas that were vacant in earlier surveys.
“New areas that were colonized by tigers in 2018 constituted 25,709 (28%) km2,” the authors stated in their report. “This analysis suggests that loss and gain of tiger occupancy was mostly from habitat pockets that support low density populations. Such habitats with low density tigers, though contributing minimally to overall tiger numbers, are crucial links for gene flow and maintaining connectivity between source populations.”
Thanks to the efforts of Project Tiger, which was established in 1973, India has increased the land set aside for tigers from just nine reserves encompassing approximately 18,278 km (11,360 miles) to 502 reserves comprising 72,749 km (45,200 miles) -- a huge improvement, although it is important to realize this represents only 2.21% of India’s total geographical area.
Other conservation actions that India has successfully implemented include connecting tiger source populations through habitat corridors and managing and protecting tiger reserves through incentivized voluntary relocation of humans.
Wild Bengal tigers live in a wide variety of habitat types, ranging from dry and tropical forests, and mangroves to grasslands. They avoid humans whenever possible, which is becoming increasingly difficult because India’s population has more than doubled in the last 20 years, now numbering more than 1.35 billion people.
Yet, despite tigers’ protected status, people and their livestock, roads, canals and railways are increasingly encroaching on tiger habitats and even into tiger reserves. This inevitably leads to conflicts provoked by killings of livestock or attacks on people, making tragedies inevitable, like the one that went viral recently where villagers viciously beat a tigress to death (more here). That lynched tigress attacked people after straying out of the Pilibhit tiger reserve in Uttar Pradesh.
One month prior to that, another tigress and her two cubs died after villagers poisoned the carcass of a cow she had killed a day earlier.
Such conflicts between tigers and humans occur mostly along the edges of protected reserves, forests and plantations, because India still needs to expand its tiger reserves to meet the needs of its tiny tiger population.
Additionally, tiger poaching is still alive and well -- body parts such as whiskers, teeth, the tail and skins are sold on the black market or used in “alternative medicines” in China. For example, of the 657 tigers died between 2010 and 2018, 21% were killed by poachers. But the Indian government is becoming more proactive so poachers photographed by tiger camera traps are now given a seven-year prison sentence.
Other threats includes climate change and rising sea levels, which endangers some of the last remaining tiger habitats (ref).
The XENON1T detector, with its low-background cryostat, is installed in the centre of a large water shield to protect the instrument against cosmic ray backgrounds. This setup enables the scientists working on the XENON1T experiment to greatly reduce their background noise, and more confidently discover the signals from processes they're attempting to study. XENON is not only searching for heavy, WIMP-like dark matter, but other forms of potential dark matter, including light candidates like dark photons and axion-like particles.
XENON1T collaboration
Sometimes, the solution to a puzzle you've been stymied by lies in a place you've already looked. Only, until you develop better-precision tools than you've used to conduct your previous searches, you won't be able to find it. This has played out many times in the sciences, from the discovery of new particles to uncovering phenomena like radioactivity, gravitational waves, or dark matter and dark energy.
We've been looking for new particles not predicted by the Standard Model with an enormous variety of experiments for decades, from accelerators to underground laboratories to rare, exotic decays of everyday particles. Despite decades of searching, no beyond-the-Standard-Model particles have ever turned up. But recently, searches have begun to consider light dark matter, despite having already looked in that expected range. We have to look better, and one unexplained experimental result is the reason why.
When you collide any two particles together, you probe the internal structure of the particles colliding. If one of them isn't fundamental, but is rather a composite particle, these experiments can reveal its internal structure. Here, an experiment is designed to measure the dark matter/nucleon scattering signal. However, there are many mundane, background contributions that could give a similar result. This particular hypothetical scenario will create an observable signature in Germanium, liquid XENON and liquid ARGON detectors.
Dark Matter Overview: Collider, Direct and Indirect Detection Searches - Queiroz, Farinaldo S. arXiv:1605.08788
Identifying a scientific puzzle — a phenomenon or observation that cannot be conventionally explained — is often the starting point that leads to a scientific revolution. If heavy elements are made from the synthesis of lighter ones, for example, then you have to have a viable pathway for the natural construction of the heavy elements we see today. If your best theory cannot explain why carbon exists, but we observe carbon to exist, that's a good puzzle for science to investigate.
Often, the puzzle itself offers possible clues to a solution. The fact that there are no stationary, oscillating in-phase electric and magnetic fields led to Special Relativity. If not for a mysterious observation of missing energy in radioactive beta decays, we wouldn't have predicted the neutrino. And patterns seen in the heavy composite particles produced in accelerators led to the quark model and the prediction of the Ω- baryon.
Different ways of putting together up, down, strange and bottom quarks with a spin of +3/2 results in the following 'baryon spectrum', or collection of 20 composite particles. The Ω- particle, on the lowest rung of the pyramid, was first predicted by applying Murray Gell-Mann's quark theory to the structure of the previously-known particles and inferring the existence of the missing pieces.
Fermi National Accelerator Laboratory
In the case of the mystery of carbon's existence, the situation has only gotten more interesting with time. Back in the 1950s, scientist Fred Hoyle, along with Geoffrey and Margaret Burbidge, were trying to understand how the heavier elements of the periodic table were formed if all you began with were the lightest ones of all.
Postulating that the Sun was powered by the energy released from the nuclear fusion of light elements into heavy ones, Hoyle could account for the synthesis of deuterium, tritium, helium-3 and helium-4 from raw hydrogen nuclei (protons), but couldn't find a way to get to carbon. You couldn't add a proton or neutron to helium-4, since both helium-5 and lithium-5 were unstable: they'd decay after ~10-22 seconds. You couldn't add two helium-4 nuclei together, because beryllium-8 was too unstable, decaying after ~10-16 seconds.
The triple-alpha process, which occurs in stars, is how we produce elements carbon and heavier in the Universe, but it requires a third He-4 nucleus to interact with Be-8 before the latter decays. Otherwise, Be-8 goes back to two He-4 nuclei.
E. Siegel / Beyond The Galaxy
But Hoyle had a brilliant possible solution up his sleeve. If a dense enough environment could create beryllium-8 on fast enough timescales, it could be possible for a third nucleus — another helium-4 — to get in there before the beryllium decayed away. Mathematically, that would enable you to create carbon-12: permitting the existence of carbon under the right conditions.
Unfortunately, we knew the mass of a carbon-12 nucleus, and it didn't match the mass of helium-4 plus the mass of beryllium-8. Unless our understanding of nuclear physics was wrong, this reaction couldn't account for the carbon we see today. But Hoyle's workaround was brilliant: he hypothesized the existence of another, hitherto undiscovered possibility: a resonant state of carbon-12 could exist that did have the right mass.
Willie Fowler in the W.K. Kellogg Radiation Laboratory at Caltech, which confirmed the existence of the Hoyle State and the triple-alpha process.
Caltech Archives
Then, it could decay to the carbon-12 we see today. This nuclear process, the triple-alpha process, is now known to occur inside red giant stars, with the resonant state of carbon-12 now known as the Hoyle state, as it was confirmed by nuclear physicist Willie Fowler later in the 1950s. The existence of carbon, and the puzzle of how to create it using known physics and pre-existing ingredients, led to this remarkable discovery.
Perhaps, then, a similar line of reasoning could lead to a solution to the biggest puzzles facing physicists today?
It's undoubtedly worth a try. We all know that these big puzzles include dark matter, dark energy, the origin of the matter/antimatter asymmetry in our Universe, the origin of neutrino mass and the incredible difference between the Planck scale and the actual masses of the known particles.
The masses of the quarks and leptons of the Standard Model. The heaviest standard model particle is the top quark; the lightest non-neutrino is the electron, which is measured to have a mass of 511 kev/c^2. The neutrinos themselves are at least 4 million times lighter than the electron: a bigger difference than exists between all the other particles. All the way at the other end of the scale, the Planck scale hovers at a foreboding 10^19 GeV. We do not know of any particles heavier than the top quark, nor why the particles have the mass values that they do.
Hitoshi Murayama of http://hitoshi.berkeley.edu/
On the other hand, we have clues from measurements and observations that our current story of the Universe may not be all that there is. Most of these have not yet reached the definitive 5-sigma threshold we require to claim that something new is out there, but they are suggestive.
The muon's measured magnetic moment doesn't match theoretical predictions with a 3.6-sigma tension.
The AMS experiment has seen an excess of positrons, with an energy cutoff seen with 4.0-sigma confidence.
But one experiment blew past that threshold years ago: an experiment designed to measure the decay of that short-lived state so essential to creating carbon in the Universe: beryllium-8. It disagrees with our conventional predictions by an impressive 6.8-sigma, and is known in the community as the Atomki anomaly.
The accelerator model, used to bombard Lithium and create the Be-8 used in the experiment that first showed an unexpected discrepancy in particle decays, located at the entrance of the Institute of Nuclear Research of the Hungarian Academy of Sciences.
Yoav Dothan
When you create a particle like beryllium-8, you fully expect it to decay back into two helium-4 nuclei with no preferred direction with respect to its center of mass. In a laboratory setting, fusing two helium-4 nuclei is impractical, but fusing lithium-7 with a proton will do just as good a job at creating beryllium-8 with one additional exception: it will create the beryllium-8 nucleus in an excited state.
Just as the Hoyle state of carbon was an excited state, it needed to emit a high-energy (gamma ray) photon before dropping down to the ground state. Well, the excited beryllium-8 has to emit a high-energy photon before it can decay to two helium-4 nuclei, and that photon will be energetic enough that there's a chance it can spontaneously produce an electron/positron pair. The relative angle between the electron and the positron, assuming you make a detector to trace out those tracks, will tell you what the energy of the emitted photon was.
The decay tracks of unstable particles in a cloud chamber, which allow us to reconstruct the original reactants. The opening angle between the sideways "V" shaped track will tell you the energy of the particle that decayed into them.
Wikimedia Commons user Cloudylabs
You'd fully expect that there would be a predictable energy distribution for the photon, and hence a smooth distribution in the opening angles between the electron and positron. You'd fully anticipate a maximum number of events with a particular angle, and then the event rate would decrease the greater you departed from that angle.
Except, starting in 2015, a Hungarian team led by Attila Krasznahorkay found a surprise: as the angle between the electrons and positrons gets larger, the number of events decreases, until you get to about a 140º angular separation, where they observed a surprising increase in the number of events. Maybe it was an experimental error; maybe there was an analysis error; or maybe, just maybe, the result is robust, and this is a clue that might help us solve a deep mystery in physics.
The excess of signal in the raw data here, outlined by E. Siegel in red, shows the potential new discovery now known as the Atomki anomaly. Although it looks like a small difference, it's an incredibly statistically significant result, and has led to a series of new searches for particles of approximately 17 MeV/c^2.
A.J. Krasznahorkay et al., 2016, Phys. Rev. Lett. 116, 042501
If the result is robust, one potential explanation is the existence of a new particle with a specific mass: about 0.017 GeV/c2. This particle would be heavier than the electron and all of the neutrinos, but lighter than every other massive, fundamental particle ever discovered. Manydifferenttheoreticalscenarios have been proposed to account for this measurement, and various ways to look for an experimental signature have also been devised.
The spin-dependent and spin-independent results from the XENON collaboration indicate no evidence for a new particle of any mass, including the light dark matter scenario that would fit with the Atomki anomaly.
E. Aprile et al., 'Light Dark Matter Search with Ionization Signals in XENON1T,' arXiv:1907.11485
If it weren't for the puzzling nature of the Atomki anomaly, there would be no motivation to be interested in dark matter at these energies. Results from electron-positron colliders should have seen something at these energies long ago, but no evidence for a new particle exists. It's only through contrived scenarios, which were explicitly contrived to both explain the Atomki anomaly and evade the existing constraints, that we concocted these light dark matter scenarios.
Still, that's where the clues are, so that's one of the places we're looking. There's a big warning here: in science, we have a tendancy to find the particles we're seeking in the places where we're actively looking, whether they actually exist or not. Fokke de Boer, who led the Atomki experiments before Krasznahorkay did, had a rich history of discovering similar evidence for new particles, only to have those results fail verification and replication.
The jury is still out on whether this anomaly is as good as it's hyped to be, but until we have a robust explanation, we have to both keep an open mind and look everywhere the data tells us new physics might reasonably be. Despite the null results, the search continues.
The solar sail deploying on LightSail 2. (The Planetary Society)
