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LIGO's black holes collided inside a star
ALEXANDER SEMENOV/SCIENCE PHOTO LIBRARY
in Brief Voices best for warnings in space
Sea butterflies ‘fly’ in water just like insects do in the air THESE graceful winged sea snails are so admired for their looks that they are known as sea butterflies. It turns out that they share more with insects than just a name – they flap their wings under water just like flies. The tiny snails, Limacina helicina, are one species of zooplankton in the cold waters of the Arctic and Antarctic. Their heavy shell makes them sink like a rock when stationary – unless they secrete a mucous web that keeps them afloat. They have also evolved wing-like appendages for swimming. But exactly how they beat their “wings” and how that propels them was unknown.
Now David Murphy at Johns Hopkins University in Baltimore, Maryland, and his team have captured those details for the first time, using four high-speed cameras in a tank with free-swimming snails. What they saw surprised them. Most zooplankton paddle to push them through the water. But sea snails flap their wings just like a fruit fly, generating lift (Journal of Experimental Biology, doi.org/bcnm). “I had an ‘aha!’ moment when I saw its wing tips move in the same distinct figure-eight pattern,” says Murphy. This shows evolution converging on one locomotion technique to allow unrelated species to navigate similar environments. Due to their tiny size, the balance of inertial and viscous forces that sea snails experience in water is similar to that experienced by flies in air.
LIGO’s black holes collided inside a star CALL it a gut reaction. Space-time ripples may have come from two black holes colliding inside the belly of an enormous star. Scientists already knew that the gravitational waves detected by LIGO, the Laser Interferometer Gravitational-Wave Observatory, were generated when two black holes merged. Just 0.4 seconds later, NASA’s Fermi gamma-ray space telescope detected a bright
burst of gamma rays. It’s not clear whether the same event triggered both signals, but the Fermi team calculated that the probability of a coincidence was just 0.0022. But models of gamma-ray bursts suggest that isolated black holes can’t ignite them. Avi Loeb of Harvard University thinks he has an explanation: you could get a gamma-ray burst if the two black holes formed inside a
very massive star. Once the black holes merged, the star would collapse, triggering intense beams of gamma rays (arxiv.org/ abs/1602.04735). “The only way to explain the Fermi signal is to surround the black holes with a lot of dense material, and the obvious way to do that, as in Loeb’s idea, is to put them inside a star,” says Dan Maoz of Tel Aviv University in Israel. “Maybe there are other ideas, but we need to think them up.”
FIRE! Fire! Astronauts aboard the International Space Station may respond more quickly to human voice alerts than other types of emergency sounds. ISS crew are currently notified of dangerous events such as fires with specific sound tones, but in a high-stress situation it can be difficult to remember what they mean, says Aniko Sandor at the NASA Johnson Space Center (JSC) in Houston, Texas. To see whether voice alerts could be more useful, Sandor and her colleague Haifa Moses tested tones against voices in the Human Exploration Research Analog at the JSC, intended to simulate a real space station or planetary base. One participant reacted to both kinds of alert at similar speeds, but the other five were an average of 5 seconds faster at reacting to speech alarms, suggesting that a voice-alert system could improve safety on spacecraft.
Plants forget stress on purpose FORGET-ME-NOTS like to forget. Some plants have a long-term memory of things such as drought, priming them to tackle such future stresses quicker. But it seems that forgetting may be more beneficial – and the norm. When Peter Crisp at the Australian National University in Canberra and his colleagues scoured previous studies for examples of plant memories, they found that it is unusual. “Generally plants are good at forgetting,” says Crisp. His team argues that plants are making a trade-off. While being primed against previously experienced stress can be beneficial, it also comes with the cost of expressing genes when they aren’t needed (Science Advances, doi.org/bcp2). 27 February 2016 | NewScientist | 19
in Brief Voices best for warnings in space
Sea butterflies ‘fly’ in water just like insects do in the air THESE graceful winged sea snails are so admired for their looks that they are known as sea butterflies. It turns out that they share more with insects than just a name – they flap their wings under water just like flies. The tiny snails, Limacina helicina, are one species of zooplankton in the cold waters of the Arctic and Antarctic. Their heavy shell makes them sink like a rock when stationary – unless they secrete a mucous web that keeps them afloat. They have also evolved wing-like appendages for swimming. But exactly how they beat their “wings” and how that propels them was unknown.
Now David Murphy at Johns Hopkins University in Baltimore, Maryland, and his team have captured those details for the first time, using four high-speed cameras in a tank with free-swimming snails. What they saw surprised them. Most zooplankton paddle to push them through the water. But sea snails flap their wings just like a fruit fly, generating lift (Journal of Experimental Biology, doi.org/bcnm). “I had an ‘aha!’ moment when I saw its wing tips move in the same distinct figure-eight pattern,” says Murphy. This shows evolution converging on one locomotion technique to allow unrelated species to navigate similar environments. Due to their tiny size, the balance of inertial and viscous forces that sea snails experience in water is similar to that experienced by flies in air.
LIGO’s black holes collided inside a star CALL it a gut reaction. Space-time ripples may have come from two black holes colliding inside the belly of an enormous star. Scientists already knew that the gravitational waves detected by LIGO, the Laser Interferometer Gravitational-Wave Observatory, were generated when two black holes merged. Just 0.4 seconds later, NASA’s Fermi gamma-ray space telescope detected a bright
burst of gamma rays. It’s not clear whether the same event triggered both signals, but the Fermi team calculated that the probability of a coincidence was just 0.0022. But models of gamma-ray bursts suggest that isolated black holes can’t ignite them. Avi Loeb of Harvard University thinks he has an explanation: you could get a gamma-ray burst if the two black holes formed inside a
very massive star. Once the black holes merged, the star would collapse, triggering intense beams of gamma rays (arxiv.org/ abs/1602.04735). “The only way to explain the Fermi signal is to surround the black holes with a lot of dense material, and the obvious way to do that, as in Loeb’s idea, is to put them inside a star,” says Dan Maoz of Tel Aviv University in Israel. “Maybe there are other ideas, but we need to think them up.”
FIRE! Fire! Astronauts aboard the International Space Station may respond more quickly to human voice alerts than other types of emergency sounds. ISS crew are currently notified of dangerous events such as fires with specific sound tones, but in a high-stress situation it can be difficult to remember what they mean, says Aniko Sandor at the NASA Johnson Space Center (JSC) in Houston, Texas. To see whether voice alerts could be more useful, Sandor and her colleague Haifa Moses tested tones against voices in the Human Exploration Research Analog at the JSC, intended to simulate a real space station or planetary base. One participant reacted to both kinds of alert at similar speeds, but the other five were an average of 5 seconds faster at reacting to speech alarms, suggesting that a voice-alert system could improve safety on spacecraft.
Plants forget stress on purpose FORGET-ME-NOTS like to forget. Some plants have a long-term memory of things such as drought, priming them to tackle such future stresses quicker. But it seems that forgetting may be more beneficial – and the norm. When Peter Crisp at the Australian National University in Canberra and his colleagues scoured previous studies for examples of plant memories, they found that it is unusual. “Generally plants are good at forgetting,” says Crisp. His team argues that plants are making a trade-off. While being primed against previously experienced stress can be beneficial, it also comes with the cost of expressing genes when they aren’t needed (Science Advances, doi.org/bcp2). 27 February 2016 | NewScientist | 19