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LIGO black holes may come from lifelong pairs
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This week
Civilisation, the enemy of bacteria Andy Coghlan
IT’S not just elephants and tigers – we have been wiping out far tinier organisms too, with potential consequences for our physical and mental health. That’s the bleak message from an in-depth analysis of the effect our history as a species has had on Earth’s microbes, especially those that live inside us. “Diversity of gut bacteria is declining with civilisation,” Michael Gillings of Macquarie University in Sydney,
LIGO black holes may come from lifelong pairs THE recent spate of gravitational waves may come from pairs of stars that lived and died together. These gravitational waves are created when two black holes orbiting each other spiral inwards and merge, producing a massive burst of energy. Last week, the Laser Interferometer Gravitational-Wave Observatory (LIGO) announced it had found a second such ripple in space-time. 10 | NewScientist | 25 June 2016
Australia, told the annual meeting of the American Society for Microbiology in Boston this week. The practices of the human era, known as the Anthropocene – including agriculture, sanitation and widespread antibiotic use – are probably to blame. Gillings suggests that the microorganisms living inside us began to get less diverse 350,000 years ago, when we learned to use fire. Cooking unlocked more calories from our food, allowing us to evolve smaller digestive
But how do you make a binary black hole in the first place? Start with a binary star, says Krzysztof Belczynski of Warsaw University, Poland. Belczynski and colleagues modelled how binary star systems could evolve into binary black holes like the source of the first LIGO signal. They started with two stars formed around 2 billion years after the big bang, one 96 times the mass of the sun, the other 60 times. After 3.5 million years, the stars got close enough to shift material from the larger to the smaller, collapsing the larger star into a black hole. For a few million years more, the black hole
livestock,” says Antje Boetius of the Max Planck Institute of Marine Microbiology in Bremen, Germany. Farming the same animals and eating the same food means that microbes are less diverse, and valuable genetic sequences may have been lost forever, she says. For humans, the biggest changes probably occurred after the industrial revolution. Disinfectants, sanitation, processed food, caesarean births, bottle-feeding, frequent international travel, and – –How we eat made bacteria extinct– most of all – antibiotic drugs together prompted a major tracts with less space for microbes homogenisation of the bacteria to grow. and other species that live inside Bacterial diversity probably humans worldwide. declined further around 10,000 Some researchers suspect years ago, when the invention of that the sudden loss of so many agriculture narrowed our diets species plays a role in a wide range and pushed sheep, pigs, cattle of health problems, including and poultry to eventually obesity, asthma, psoriasis and become some of the most even mental health conditions. common vertebrates on Earth. “It’s beginning to look like the Around 12,000 years ago, microbiome has effects on brain before agriculture, most of the activity, and anxiety and world’s gut flora – with a biomass depression have been linked estimated at 200 million tonnes – with irritable bowel syndrome,” would have been living inside wild said Gillings. animals. By the year 2000, the But we could stop the trend, microbial biomass in wild says Boetius. “By increasing crop animals was tiny compared with diversity and [changing] how the 600 million tonnes in farm we live, we can decide how to animals and the 200 million manage this,” she says. “It’s tonnes living inside us. about behaviour, and we can “We only use four species of change that.” n
and the star shared an envelope of gas, drawing them closer before the second star collapsed, leaving two black holes of 37 and 31 solar masses. These happily coexisted for another 10 billion years before colliding. The team calculates that there should be 218 such mergers each year in a particular volume of space. LIGO’s rate of detection so far implies the universe produces between 9 and 240 black hole mergers in the same time
“People are starting to do these studies as we actually have some data to play with”
and volume, so the model fits (Nature, DOI: 10.1038/nature18322). But just last week, Carl Rodriguez of Northwestern University in Evanston, Illinois, and his colleagues suggested most binary black holes are created in a different way: from many individual holes thrashing around in dense stellar regions. They predicted a rate of between 5 and 10 mergers – still consistent with LIGO. “The game now is to try to narrow down which classes of models are correct,” says Mark Hannam of Cardiff University, UK. “People are starting to do these studies as we actually have some data to play with.” Jacob Aron n
This week
Civilisation, the enemy of bacteria Andy Coghlan
IT’S not just elephants and tigers – we have been wiping out far tinier organisms too, with potential consequences for our physical and mental health. That’s the bleak message from an in-depth analysis of the effect our history as a species has had on Earth’s microbes, especially those that live inside us. “Diversity of gut bacteria is declining with civilisation,” Michael Gillings of Macquarie University in Sydney,
LIGO black holes may come from lifelong pairs THE recent spate of gravitational waves may come from pairs of stars that lived and died together. These gravitational waves are created when two black holes orbiting each other spiral inwards and merge, producing a massive burst of energy. Last week, the Laser Interferometer Gravitational-Wave Observatory (LIGO) announced it had found a second such ripple in space-time. 10 | NewScientist | 25 June 2016
Australia, told the annual meeting of the American Society for Microbiology in Boston this week. The practices of the human era, known as the Anthropocene – including agriculture, sanitation and widespread antibiotic use – are probably to blame. Gillings suggests that the microorganisms living inside us began to get less diverse 350,000 years ago, when we learned to use fire. Cooking unlocked more calories from our food, allowing us to evolve smaller digestive
But how do you make a binary black hole in the first place? Start with a binary star, says Krzysztof Belczynski of Warsaw University, Poland. Belczynski and colleagues modelled how binary star systems could evolve into binary black holes like the source of the first LIGO signal. They started with two stars formed around 2 billion years after the big bang, one 96 times the mass of the sun, the other 60 times. After 3.5 million years, the stars got close enough to shift material from the larger to the smaller, collapsing the larger star into a black hole. For a few million years more, the black hole
livestock,” says Antje Boetius of the Max Planck Institute of Marine Microbiology in Bremen, Germany. Farming the same animals and eating the same food means that microbes are less diverse, and valuable genetic sequences may have been lost forever, she says. For humans, the biggest changes probably occurred after the industrial revolution. Disinfectants, sanitation, processed food, caesarean births, bottle-feeding, frequent international travel, and – –How we eat made bacteria extinct– most of all – antibiotic drugs together prompted a major tracts with less space for microbes homogenisation of the bacteria to grow. and other species that live inside Bacterial diversity probably humans worldwide. declined further around 10,000 Some researchers suspect years ago, when the invention of that the sudden loss of so many agriculture narrowed our diets species plays a role in a wide range and pushed sheep, pigs, cattle of health problems, including and poultry to eventually obesity, asthma, psoriasis and become some of the most even mental health conditions. common vertebrates on Earth. “It’s beginning to look like the Around 12,000 years ago, microbiome has effects on brain before agriculture, most of the activity, and anxiety and world’s gut flora – with a biomass depression have been linked estimated at 200 million tonnes – with irritable bowel syndrome,” would have been living inside wild said Gillings. animals. By the year 2000, the But we could stop the trend, microbial biomass in wild says Boetius. “By increasing crop animals was tiny compared with diversity and [changing] how the 600 million tonnes in farm we live, we can decide how to animals and the 200 million manage this,” she says. “It’s tonnes living inside us. about behaviour, and we can “We only use four species of change that.” n
and the star shared an envelope of gas, drawing them closer before the second star collapsed, leaving two black holes of 37 and 31 solar masses. These happily coexisted for another 10 billion years before colliding. The team calculates that there should be 218 such mergers each year in a particular volume of space. LIGO’s rate of detection so far implies the universe produces between 9 and 240 black hole mergers in the same time
“People are starting to do these studies as we actually have some data to play with”
and volume, so the model fits (Nature, DOI: 10.1038/nature18322). But just last week, Carl Rodriguez of Northwestern University in Evanston, Illinois, and his colleagues suggested most binary black holes are created in a different way: from many individual holes thrashing around in dense stellar regions. They predicted a rate of between 5 and 10 mergers – still consistent with LIGO. “The game now is to try to narrow down which classes of models are correct,” says Mark Hannam of Cardiff University, UK. “People are starting to do these studies as we actually have some data to play with.” Jacob Aron n