More stories

  • in

    A Brief History of Timekeeping: A new book explores how we mark time

    By George Bass

    HOW did humans progress from measuring time with stone solstice markers to a smart watch on which it is also possible to read this review?
    In A Brief History of Timekeeping, Chad Orzel, physicist and author of bestselling book How to Teach Quantum Physics to Your Dog, turns his enthusiasm for time travel to something more tangible: how humans through the ages have measured the passage of time.
    It may seem like being ruled by the clock is a relatively recent phenomenon, but Orzel argues that it has been “a major concern in essentially every era and location we find evidence of human activity”.
    Thanks to a 1960s excavation of a site in east Ireland, for example, we know that the 5200-year-old tomb Newgrange was built by people with enough astronomical knowledge to create an opening that focuses a shaft of light onto the back of the chamber at sunrise on the winter solstice.
    Knowledge of the movement of stars remains important today in our understanding of time, says Orzel. It explains, for instance, why religious holidays change dates from year to year. Yet the calendar is also a social construct, representing a delicate balancing act between stellar movement, bureaucracy, ritual and religion. The overnight jump from Wednesday 2 September to Thursday 14 September when Great Britain adopted the Gregorian calendar in 1752 is a case in point.
    Orzel’s enthusiasm for the past is balanced by his disdain for modern misconceptions around time. He admonishes the flat-Earth conspiracy theory that has been promoted by celebrities like basketball player Kyrie Irving, and the way it disrupts geography and astronomy lessons in schools.
    He also laments how the passing aeons often only become of interest to the public when they have something dramatic to say, such as the widely shared Mayan prophecy that the world would end on 21 December 2012. This was based on a fundamental misreading of the Mayan calendar system, says Orzel, who concedes that at least it made people more aware of the Mayans’ pioneering base-20 numerical system.
    Throughout the book, Orzel scoots backwards and forwards in time, treating us to illustrations of spectacular forgotten timepieces. He explains how Athenian water clocks were used to limit speaking time in law courts, how a 12th-century Chinese water tower designed by Su Song became the basis for the modern mechanical clock, using a system of scoops, bronze spheres, counterweights and – crucially – a numbered face. Rod-based verge-and-foliot clocks followed in its wake, and Orzel details how these gave way to the pendulum, which reduced the number of missed ticks per day from several hours’ worth to just minutes.
    The author’s enthusiasm doesn’t wane as he moves into the digital era, explaining how quartz-based wristwatches “democratised” time and serve as temporal “tuning forks” for the masses, before exploring how many of our modern devices sync up with caesium atomic clocks for the latest word in punctuality.
    He also ponders how tomorrow’s quantum computers may prompt physicists to argue for the decimalisation of time. This has been attempted before, most recently by 19th-century French polymath Jules Henri Poincaré, who argued for splitting the day into 100 minutes made up of 100 seconds. This would be confusing for a generation or so, but as Orzel’s book makes clear, time, and its measurement, stands still for no one.

    More on these topics: More

  • in

    Don't Miss: Moonfall, a disaster movie of epic proportions

    Reiner Bajo/Lionsgate
    Watch
    Moonfall sees director Roland Emmerich try to top his other disaster films, such as The Day After Tomorrow and Independence Day, by knocking the moon out of orbit and crashing it into Earth. In cinemas from 4 February.

    Read
    The Man Who Tasted Words and other unusually gifted or affected people are the subject of neurologist Guy Leschziner’s journey through our senses, setting out how we use them to understand the complexities of the world around us.Advertisement
    Rolex/Ambroise Tézenas
    Visit
    Thao Nguyen Phan has combined videos, silk paintings and mixed media to explore the history, industry and contested future of Vietnam’s Mekong river. The exhibition runs at Tate St Ives, UK, from 5 February.

    More on these topics: More

  • in

    Origin review: A genetic history of the Americas

    By Michael Marshall

    WHO were the first people to reach the Americas? When did they get there, and how? These are among the most mysterious questions in prehistory, and have long been studied using traditional archaeology: bones, artefacts and so on. In recent years, however, the field has been revolutionised by genetic data. DNA from living people and preserved remains has both enhanced and transformed our understanding of the continents’ First Peoples (those who were on the continent before Europeans arrived) and how they got there.
    Jennifer Raff is a genetic anthropologist at the University of Kansas who has been involved in many studies of ancient American DNA, so she is an ideal guide to the subject. Her book Origin bills itself as “a genetic history of the Americas”, and it largely delivers on that promise. The final third of the book, in particular, draws on genetic and archaeological evidence to tell the story as we see it now. This section is a model of clear and nuanced explanation: Raff highlights the uncertainties and caveats, but doesn’t allow them to overwhelm the story.
    The earlier part of the book is less clear in places. Raff re-examines not only some of the Americas’ most important digs, but the problems inherent in interpreting the evidence from artefacts alone, before the advent of genetic technology.
    She recounts, for example, how archaeologists were convinced that the first people in the Americas were the Clovis, who made a distinctive kind of stone tool. This idea became dogma, and any archaeological sites that seemed older than the Clovis were dismissed – often on flimsy grounds. Only in the past decade or so has pre-Clovis settlement become accepted.
    Then there is the question of how the First Peoples got there. All the evidence suggests that they came from Asia, but there is an open question over the route they took. The evidence is complex and contradictory, and Raff is admirably fair-minded in the way she handles it.
    These sections are crucial to the story because they elucidate just how much light genetics has been able to shed on the big mysteries. Unfortunately, they jump back and forth in time, both in prehistory and in the historical sequence in which the discoveries were made, which can get a little confusing. The problem is exemplified by the first page, where an arresting anecdote is interrupted by four footnotes.
    Despite this, Origin has many strengths. Raff is a critical historian of her own field, who casts a beady eye over the crimes and misdemeanours committed by earlier generations of archaeologists in the Americas. She argues that the story of anthropology in the Americas cannot be separated from the genocide perpetrated by Europeans on First Peoples. Archaeologists frequently dug up buried bodies without consulting local Native American groups, who regard the bodies as their own ancestors – a belief that has often been validated by genetic evidence.
    These attitudes also fed into scientists’ conclusions. When huge artificial structures were found in North America, Europeans attributed them to a lost group of “Mound Builders” and argued that they couldn’t be the work of First Peoples.
    “Raff casts a beady eye over the crimes and misdemeanours of earlier generations of archaeologists”
    It will make uncomfortable reading for people still wrestling with the legacy of the European colonial empires. Some scientists may prefer that these darker episodes not be mentioned, but I tend to agree with Raff that it is crucial to face them head on. She argues that scientists studying the history and culture of Indigenous peoples anywhere in the world must be in constant dialogue with them: asking permission before conducting new studies and asking what the Indigenous peoples themselves want to know.
    Minor niggles aside, then, Origin is a very human book. The settlement of the Americas isn’t simply a scientific mystery to be solved. For Raff, studying the First Peoples is also about learning collaboratively and healing the wounds of history.

    More on these topics: More

  • in

    160,000-year-old fossil may be the first Denisovan skull we've found

    A partial skull from China represents the earliest human with a “modern” brain size. It could represent an unknown group of ancient humans, or perhaps one of the enigmatic Denisovans

    Humans

    26 January 2022

    By Michael Marshall
    Fragments of a large ancient human skull known as Xujiayao 6Xiu-Jie Wu,Christopher J.Bae, Martin Friess, Song Xing, Sheela Athreya, Wu Liu
    An ancient human that lived in China at least 160,000 years ago had an unusually large brain for the time – comparable to the brain size of people alive today. The find is more evidence that hominin evolution went in many different directions, rather than taking a straight line from small brains to large ones.
    It is also possible that the skull belonged to a mysterious kind of hominin called a Denisovan. Very few Denisovan bones are known, so … More

  • in

    The James Webb Space Telescope has reached its new home at last

    The James Webb Space Telescope has finally arrived at its new home. After a Christmas launch and a month of unfolding and assembling itself in space, the new space observatory reached its final destination, a spot known as L2, on January 24.

    But the telescope can’t start doing science yet. There are still several months’ worth of tasks on Webb’s to-do list before the telescope is ready to peep at the earliest light in the universe or spy on exoplanets’ alien atmospheres (SN: 10/6/21).

    “That doesn’t mean there’s anything wrong,” says astronomer Scott Friedman of the Space Telescope Science Institute in Baltimore, who is managing this next phase of Webb’s journey. “Everything could go perfectly, and it would still take six months” from launch for the telescope’s science instruments to be ready for action, he says.

    Here’s what to expect next.

    Life at L2

    L2, technically known as the second Earth-sun Lagrange point, is a spot about 1.5 million kilometers from Earth in the direction of Mars, where the sun and Earth’s gravity are of equal strength. Pairs of massive objects in space have five such Lagrange points, where the gravitational pushes and pulls from these celestial bodies essentially cancel each other out. That lets objects at Lagrange points stay put without much effort.

    The telescope, also known as JWST, isn’t just sitting tight, though. It’s orbiting L2, even as L2 orbits the sun. That’s because L2 is not precisely stable, Friedman says. It’s like trying to stay balanced directly on top of a basketball. If you nudged an object sitting exactly at that point, it would be easy to make it wander off. Circling L2 as L2 circles the sun in a “halo orbit” is much more stable — it’s harder to fall off the basketball when in constant motion. But it takes some effort to stay there.

    Sign Up For the Latest from Science News

    Headlines and summaries of the latest Science News articles, delivered to your inbox

    Thank you for signing up!

    There was a problem signing you up.

    “JWST and other astronomical satellites, which are said to be at L2 but are really in halo orbits, need propulsion to maintain their positions,” Friedman says. “For JWST, we will execute what we call station keeping maneuvers every 21 days. We fire our thrusters to correct our position, thus maintaining our halo orbit.”

    The amount of fuel needed to maintain Webb’s home in space will set the lifetime of the mission. Once the telescope runs out of fuel, the mission is over. Luckily, the spacecraft had a near-perfect launch and didn’t use much fuel in transit to L2. As a result, it might be able to last more than 10 years, team members say, longer than the original five- to 10-year estimate.

    [embedded content]
    Webb’s final destination is a spot in space called L2, about 1.5 million kilometers away from Earth. The telescope will actually orbit L2 as L2 orbits the sun (as shown in this animation). This special “halo orbit” helps the spacecraft stay in place without burning much fuel.

    Webb has one more feature that helps it stay stable. The telescope’s gigantic kitelike sunshield, which protects the delicate instruments from the heat and light of the sun, Earth and the moon, could pick up momentum from the stream of charged particles that constantly flows from the sun, like a solar sail. If so, that could push Webb off course. To prevent this, the telescope has a flap that acts as a rudder, said Webb sunshield manager Jim Flynn of Northrup Grumman in a January 4 news conference.

    Cooling down

    Webb sees in infrared light, wavelengths longer than what the human eye can see. But humans do experience infrared radiation as heat. “We’re essentially looking at the universe in heat vision,” says astrophysicist Erin Smith of NASA’s Goddard Space Flight Center in Greenbelt, Md., a project scientist on Webb.

    That means that the parts of the telescope that observe the sky have to be at about 40 kelvins (–233° Celsius), which nearly matches the cold of space. That way, Webb avoids emitting more heat than the distant sources in the universe that the telescope will be observing, preventing it from obscuring them from view.

    Most of Webb has been cooling down ever since the telescope’s sunshield unfurled on January 4. The observatory’s five-layer sunshield blocks and deflects heat and light, letting the telescope’s mirrors and scientific instruments cool off from their temperature at launch. The sunshield layer closest to the sun will warm to about 85° Celsius, but the cold side will be about –233° Celsius, said Webb’s commissioning manager Keith Parrish in a January 4 webcast.

    “You could boil water on the front side of us, and on the backside of us, you’re almost down to absolute zero,” Parrish said.

    One of the instruments, MIRI, the Mid-Infrared Instrument, has extra coolant to bring it down to 6.7 kelvins (–266° Celsius) to enable it to see even dimmer and cooler objects than the rest of the telescope. For MIRI, “space isn’t cold enough,” Smith says.

    Aligning the mirrors

    Webb finished unfolding its 6.5-meter-wide golden mirror on January 8, turning the spacecraft into a true telescope. But it’s not done yet. That mirror, which collects and focuses light from the distant universe, is made up of 18 hexagonal segments. And each of those segments has to line up with a precision of about 10 or 20 nanometers so that the whole apparatus mimics a single, wide mirror.

    Starting on January 12, 126 tiny motors on the back of the 18 segments started moving and reshaping them to make sure they all match up. Another six motors went to work on the secondary mirror, which is supported on a boom in front of the primary mirror.

    [embedded content]
    Before the James Webb Space Telescope can start observing the universe, all 18 segments of its primary mirror need to act as one 6.5-meter mirror. This animation shows the mirror segments moving, tilting and bending to bring 18 separate images of a star (light dots) together into a single, focused image.

    This alignment process will take until at least April to finish. In part, that’s because the movements are happening while the mirror is cooling. The changing temperature changes the shape of the mirrors, so they can’t be put in their final alignment until after the telescope’s suite of scientific instruments are fully chilled.

    Once the initial alignment is done, light from distant space will first bounce off the primary mirror, then the secondary mirror and finally reach the instruments that will analyze the cosmic signals. But the alignment of the mirror segments is “not just right now, it’s a continuous process, just to make sure that they’re always perfectly aligned,” Scarlin Hernandez, a flight systems engineer at the Space Telescope Science Institute in Baltimore said at a NASA Science Live event on January 24. The process will continue for the telescope’s lifetime.

    Calibrating the science instruments

    While the mirrors are aligning, Webb’s science instruments will turn on. Technically, this is when Webb will take its first pictures, says astronomer Klaus Pontoppidan, also of the Space Telescope Science Institute. “But they’re not going to be pretty,” Pontoppidan says. The telescope will first test its focus on a single bright star, bringing 18 separate bright dots into one by tilting the mirrors.

    After a few final adjustments, the telescope will be “performing as we want it to and presenting beautiful images of the sky to all the instruments,” Friedman says. “Then they can start doing their work.”

    These instruments include NIRCam, the primary near-infrared camera that will cover the range of wavelengths from 0.6 to 5 micrometers. NIRCam will be able to image the earliest stars and galaxies as they were when they formed at least 12 billion years ago, as well as young stars in the Milky Way. The camera will also be able to see objects in the Kuiper Belt at the edge of the solar system and is equipped with a coronagraph, which can block light from a star to reveal details of dimmer exoplanets orbiting it.

    Next up is NIRSpec, the near-infrared spectrograph, which will cover the same range of light wavelengths as NIRCam. But instead of collecting light and turning it into an image, NIRSpec will split the light into a spectrum to figure out an object’s properties, such as temperature, mass and composition. The spectrograph is designed to observe 100 objects at the same time.

    MIRI, the mid-infrared instrument, is kept the coldest to observe in the longest wavelengths, from 5 to 28 micrometers. MIRI has both a camera and a spectrograph that, like NIRCam and NIRSpec, will still be sensitive to distant galaxies and newborn stars, but it will also be able to spot planets, comets and asteroids.

    And the fourth instrument, called the FGS/NIRISS, is a two-parter. FGS is a camera that will help the telescope point precisely. And NIRISS, which stands for near-infrared imager and slitless spectrograph, will be specifically used to detect and characterize exoplanets.

    [embedded content]
    The James Webb Space Telescope’s science instruments are stored behind the primary mirror (as shown in this animation). Light from distant objects hits the primary mirror, then the secondary mirror in front of it, which focuses the light onto the instruments.

    First science targets

    It will take at least another five months after arriving at L2 to finish calibrating all of those science instruments, Pontoppidan says. When that’s all done, the Webb science team has a top secret plan for the first full color images to be released.

    “These are images that are meant to demonstrate to the world that the observatory is working and ready for science,” Pontoppidan says. “Exactly what will be in that package, that’s a secret.”

    Partly the secrecy is because there’s still some uncertainty in what the telescope will be able to look at when the time comes. If setting up the instruments takes longer than expected, Webb will be in a different part of its orbit and certain parts of the sky will be out of view for a while. The team doesn’t want to promise something specific and then be wrong, Pontoppidan says.

    But also, “it’s meant to be a surprise,” he says. “We don’t want to spoil that surprise.”

    Webb’s first science projects, however, are not under wraps. In the first five months of observations, Webb will begin a series of Early Release Science projects. These will use every feature of every instrument to look at a broad range of space targets, including everything from Jupiter to distant galaxies and from star formation to black holes and exoplanets.

    Still, even the scientists are eager for the pretty pictures.

    “I’m just very excited to get to see those first images, just because they will be spectacular,” Smith says. “As much as I love the science, it’s also fun to ooh and ahh.”    More

  • in

    An X-ray glow suggests black holes or neutron stars fuel weird cosmic ‘cows’

    A brilliant blast from a galaxy 2 billion light-years away is the brightest cosmic “Cow” found yet. It’s the fifth known object in this new class of exploding stars and their long-glowing remnants, and it’s giving astronomers even more hints of what powers these mysterious blasts.

    These Cow-like events, named for the first such object discovered in 2018 — which had the unique identifier name of AT2018cow — are a subclass of supernova explosions, making up only 0.1 percent of such cosmic blasts (SN: 6/21/19). They brighten quickly, glow brilliantly in ultraviolet and blue light and continue to show up for months in higher-energy X-rays and lower-energy radio waves.

    X-rays from the newest discovery, dubbed AT2020mrf, glowed 20 times as bright as the original Cow a month after the blast, Caltech astronomer Yuhan Yao reported January 10 at a virtual news conference held by the American Astronomical Society. And even one year after this new object’s discovery, its X-rays were 200 times as bright as those from the original Cow. Yao and colleagues also reported the results in a paper submitted December 1 at arXiv.org.

    Unraveling all that took a bit of time. The Zwicky Transient Facility at Caltech’s Palomar Observatory near San Diego, Calif., initially noted a bright new burst of light June 12, 2020, but astronomers didn’t realize what it was at the time.

    Sign Up For the Latest from Science News

    Headlines and summaries of the latest Science News articles, delivered to your inbox

    Thank you for signing up!

    There was a problem signing you up.

    Then in April 2021, researchers with the Spektrum-Roentgen-Gamma (SRG) space telescope, which studies X-ray light, alerted Yao and her colleagues to an interesting signal in SRG data from July 21–24, 2020, at the same spot in the sky. “I almost immediately realized that this might be another Cow-like event,” says Yao. The astronomers sprang to action and looked at that location with multiple other observatories in different kinds of light.

    One of those observatories was the space-based Chandra X-ray Observatory, the world’s most powerful X-ray telescope. In June 2021, a year after the original supernova blast, it captured X-rays from the same location. The source’s signal “was 10 times brighter than what I expected,” says Yao, and 200 times as bright as the original Cow was a year post-explosion.

    Even more exciting was that the strengths of both the Chandra X-ray detection and the original SRG X-ray observations also changed within hours to days. That flaring characteristic, it turns out, can tell astronomers a lot.

    “X-rays give us information of what’s happening at the heart of these events,” says MIT astrophysicist DJ Pasham, who has studied the original Cow but was not part of this new study. “The duration of the flare gives you a sense of how compact or how big the object is.”  

    A compact object like an actively eating black hole or a rapidly spinning and highly magnetic neutron star would create the strong and variable X-ray signals that were seen, Yao says. These were the two most probable leftover remnants of the original cosmic Cow as well, but the AT2020mrf observations provide even greater certainty (SN: 12/13/21).

    Further observations and catching these objects earlier in the act with multiple types of light will help researchers learn more about this new class of supernovas and what type of star eventually explodes as a Cow. More

  • in

    Science is increasingly revealing how we can boost our happiness

    Kseniia Zagrebaeva
    “Life, Liberty and the pursuit of Happiness.” These are three unalienable rights emphasised by the US Declaration of Independence as being the duty of their leaders to protect and secure.
    The third one gives perhaps most pause for thought. What should governments – and all of us – be doing to maximise societal and personal happiness? Indeed, what even defines happiness?
    Politicans and philosophers have wrangled over the apparent contradictions and conflicts that such questions throw up for centuries. Meanwhile, a simple equivalence has come to be made across the world. Many believe that happiness comes with having a bigger cake and … More

  • in

    How to perfectly pickle your cucumbers

    By Sam Wong
    StockFood/Scherer, Jim
    ALL over the world, people use acid to preserve fruit and vegetables, creating the sour and delicious foods we call pickles. The microbes that spoil our food have a hard time growing if the pH is lower than 4.5, but we can eat foods with a pH as low as 2 (the lower the pH, the more acidic the substance).
    Some pickles are made by salting vegetables or fruit, encouraging the growth of bacteria that produce lactic acid. These include kimchi, which I described in a previous issue (29 February 2020). A quicker and simpler way to make … More