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    Two black holes merged despite being born far apart in space

    Signals buried deep in data from gravitational wave observatories imply a collision of two black holes that were clearly born in different places.

    Almost all the spacetime ripples that experiments like the Laser Interferometer Gravitational-Wave Observatory, or LIGO, see come from collisions among black holes and neutron stars that are probably close family members (SN: 1/21/21). They were once pairs of stars born at the same time and in the same place, eventually collapsing to form orbiting black holes or neutron stars in old age.

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    Now, a newly noted marriage of black holes, found in existing data from U.S.–based LIGO and its sister observatory Virgo in Italy, seems to be of an unrelated pair. Evidence for this stems from how they were spinning as they merged into one, researchers report in a paper in press at Physical Review D. Black holes that are born in the same place tend to have their spins aligned, like a pair of toy tops spinning on a table, as they orbit each other. But the pair in this case have no correlation between their respective spins and orbits, implying that they were born in different places.

    “This is telling us we’ve finally found a pair of black holes that must come from the non-grow-old-and-die-together channel,” says Seth Olsen, a physicist at Princeton University.

    Previous events that have turned up in gravitational wave observations show back holes merging that aren’t perfectly aligned, but most are close enough to strongly imply family connections. The new detection, which Olsen and colleagues found by sifting through data that the LIGO-Virgo collaboration released to the public, is different. One of the black holes is effectively spinning upside down.

    That can’t easily happen unless the two black holes come from separate places. They probably met late in their stellar lives, unlike the black hole littermates that seem to make up the bulk of gravitational wave observations.

    In addition to the merger between unrelated black holes, Olsen and his collaborators identified nine other black hole mergers that had slipped through the prior LIGO-Virgo studies (SN: 8/4/21).

    “This is actually the nice thing about this type of analysis,” says LIGO scientific collaboration spokesperson Patrick Brady, a physicist at the University of Wisconsin–Milwaukee who was not affiliated with the new study. “We deliver the data in a format that can be used by other people and then [they] will have access to try out new techniques.”

    To compile so many new signals in data that had already been gone over by other researchers, Olsen’s group lowered the analytical bar a little.

    “Out of the 10 new ones,” Olsen says, “there are about three of them, statistically, that probably come from noise,” rather than being definitive black hole merger detections. Assuming that the merger of black holes strangers is not among the errant signals, it almost certainly tells a tale of black hole histories distinct from the others seen so far.

    “It would be [extremely] unlikely for this to come from two black holes that have been together for their whole lifespan,” Olsen says. “This must have been a capture. That’s cool because we’re finally able to start probing that region of the [black hole] population.”

    Brady notes that “we don’t understand the theory [of black hole mergers] well enough to be able to confidently predict all of these types of things.” But the recent study may point to new and interesting opportunities in gravitational wave astronomy. “Let’s follow this clue to see if it really is reflecting something rare,” he says. “Or if not, well, we’ll learn other things.” More

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    Shape of human brain has barely changed in past 160,000 years

    An analysis of fossils suggests changes in the shape of the braincase during human evolution were linked to alterations in the face, rather than changes in the brain itself

    Humans

    1 August 2022

    By Luke Taylor
    Digital restoration of child and adult crania from 160,000 years agoM. Ponce de León and Ch. Zollikofer/Univ. of Zurich
    The physical transformation of the human cranium over the past 160,000 years was probably driven by alterations in the face resulting from diet and lifestyle changes, not from the evolution of the brain itself as previously thought, a study has found.
    The cranium, or braincase, of early modern humans dating back 200,000 years isn’t much different in size from those today, but has a significantly different shape, suggesting that the brain has become rounder over time.
    The leading hypothesis is that changes in behaviour, such as the development of tools and art, caused the shape of the Homo sapiens brain to change and, in turn, the skull that protects it.Advertisement
    But fossil evidence is scarce and there are many interacting forces at play. It is simple for a skull with a large face to house a large brain, for example, but a small face complicates matters.
    To investigate the causes behind the transformation of the braincase, Christoph Zollikofer at the University of Zurich in Switzerland and his colleagues digitally restored the skulls of 50 hominins recovered in Ethiopia and Israel, including H. sapiens as well as Homo erectus and Neanderthal specimens for comparison. The 3D models of the fossils were then compared with 125 modern human specimens.
    Comparing the braincases of early modern human children with adults for the first time allowed the researchers to isolate the brain’s role in the evolution of the skull.
    The team was surprised to find that while the size and proportions of the skulls of H. sapiens children from 160,000 years ago were largely comparable to infants today, the adults looked remarkably different to those of modern adults, with much longer faces and more pronounced features.

    Human faces continue to grow until the age of around 20, but the brain reaches around 95 per cent of its adult size by age 6.
    If the fossil children – with near fully developed brains – resemble living ones, but fossil adults had very different skulls, we can rule out that brains have changed significantly in shape, says Zollikofer. “And if it’s not the brain driving this change, we must look for something else, like breathing, eating or moving.”
    The researchers cautiously hypothesise that changes in diet or a reduced need for oxygen could have been responsible.
    Faces in modern humans are far smaller, with subtler indentation, than those of their ancestors. Studies show that this change accelerated when hunter-gatherers became agriculturalists around 12,000 years ago and ate softer foods, probably due to less loading on the skull from chewing.
    The authors are right to remain cautious in their hypotheses, says Chris Stringer at the Natural History Museum in London.
    There is little evidence of major dietary changes between the Middle and Late Stone Age when these changes occurred, he says. Of the many possible causes, a reduction in oxygen intake could be more likely as humans have developed smaller ribcages and have less lung capacity.
    Journal reference: PNAS, DOI: 10.1073/pnas.2123553119
    Sign up to Our Human Story, a free monthly newsletter on the revolution in archaeology and human evolution

    More on these topics: More

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    My quest for an eco-friendly green lawn

    Artificial turf has grown in popularity, but it has major drawbacks, says Beronda L. Montgomery, who is looking for a sustainable alternative

    Humans

    | Columnist

    27 July 2022

    By Beronda L. Montgomery
    Olga Prava/Shutterstock
    I RECENTLY stood surveying my new front lawn with a landscaper. The grass is a fine-bladed fescue variety that grows slowly, partly because it is a shade-tolerant species situated beneath the cover of my front yard’s large oak trees. These grasses are efficient at photosynthesis and can produce enough sugars to grow in limited light.
    It is important to know whether your lawn is populated by sun-loving or shade-tolerant plants because they have different nutrient requirements. All plants have relatively high nitrogen needs because chlorophyll, which is central to photosynthesis, contains nitrogen. Shade-tolerant varieties, however, generally have lower nitrogen … More

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    Don't Miss: The Sandman, Netflix's adaptation of Neil Gaiman's comics

    Visit
    Zero to Birth reveals how the brain is built, as neurobiologist William Harris explores the development of the human brain in utero and a bit beyond. Catch it live at the Royal Institution, London, at 7pm BST on 8 August.

    Read
    The Uses of Delusion are manifold, says psychologist Stuart Vyse. In this new book, he connects research into illogical thinking with its evolutionary origins and explains the possible benefits of irrational behaviour. On sale from 1 August.

    Watch
    The Sandman stars Tom Sturridge as the titular lord of dreams, imprisoned by … More

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    Reimagined bicarb volcano could spark your children's love for science

    Shutterstock/Bangkok Click Studio
    I AM a science teacher and I think anyone who spends time with young children can be one too. It is in the home that children first encounter literature, maths, music and art – through reading, counting, singing and drawing. But this sort of informal teaching isn’t so common when it comes to science. That is partly because many people lack the knowledge or confidence to talk about science with children, and partly because science isn’t ingrained in our culture in quite the same way.
    Some children do try out “experiments” at home, such as making a “volcano” using bicarbonate of … More

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    Life As Told By a Sapiens to a Neanderthal review: Joyful curiosity

    This evolution bestseller is full of ironic humour, sharp insights and affectionate acknowledgement of human flaws – and ends up as a celebration of curiosity

    Humans

    27 July 2022

    By Rebecca Wragg Sykes
    Excavations at Atapuerca, near Burgos, Spain, shed new light on the first humans in Europeagefotostock/Alamy
    Life As Told By a Sapiens to a Neanderthal
    Juan José Millás and Juan Luis Arsuaga (translated by Thomas Bunstead and Daniel Hahn)
    Scribe
    IN THE Spanish city of Burgos, a towering 13th-century Gothic cathedral stands opposite the Museum of Human Evolution. Built 800 years apart, these buildings are both dedicated to finding meaning and exploring human origins, but the bones in the museum are 1000 times older than the cathedral, and its “high priest” … More

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    The pornography-detection cap that reads your mind

    Feedback raises an eyebrow at the cap which reads brainwaves to help China detect pornography, while also investigating secret cannabis facilities in Australia – and grave-robbing badgers

    Humans

    27 July 2022

    Josie Ford
    Thought police
    Maintaining China’s 73-year ban on pornography is a job of work, but a natty new piece of headgear may help. The government’s “porn appraisers” have now merely to cast their eyes over suspect material at speed, and their caps – a sort of wire-covered shower cap developed by researchers at Beijing Jiaotong University – will read their brainwaves and detect when something catches their salacious interest. PC Gamer wonders why the system is so far only 80 per cent accurate, suspecting it is because the training material comes pre-censored. But what if the erroneous results were false positives? Feedback … More

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    The Moonday Letters review: Genre-busting sci-fi extols hope as a duty

    In Emmi Itäranta’s The Moonday Letters, humans have adapted to live off-world. But central to this genre-crashing thrill ride is a reminder that hope is essential

    Humans

    27 July 2022

    By Sally Adee

    Living off-world is the norm in Emmi Itäranta’s new sci-fi novelGorodenkoff/Getty Images
    The Moonday Letters
    Emmi Itäranta
    Titan

    THE culture on Europa is so different from anywhere else in the solar system that visitors need to be carefully briefed during the inbound journey.

    The settlements established on the Jovian moon – domes built in the ocean deep beneath its frozen surface – are shielded from the harsh radiation of space by a thick crust of ice. A crack anywhere would be devastating and the ice is sensitive to sound, … More