Health & Science
The Milky Way’s ‘dark twin’
Astronomers have spotted a “dark twin” of the Milky Way, a discovery that blows apart their already patchy understanding of dark matter. Located 300_million light-years from Earth, Dragonfly 44 is about the same size as our own galaxy, but contains a tiny fraction of its stars. Only about 0.1 percent of the newly discovered galaxy is made up of ordinary, visible matter like stars—100 times less than the Milky Way. The rest apparently consists of dark matter, the elusive, mysterious substance that astrophysicists believe makes up 80 percent of the matter in the universe. Scientists have never actually seen dark matter; its existence is predicated on the theory that without its gravitational effect, stars and other celestial objects would drift apart rather than clump together in galaxies. Dragonfly 44 isn’t the first dark galaxy astronomers have discovered, but it’s the only one comparable in size to the Milky Way. “We thought we had sort of figured out what the relationship is between galaxies and dark matter,” the study’s lead author, Pieter van Dokkum, tells CNN.com. “This discovery turns that on its head. It means we don’t understand, kind of fundamentally, how galaxy formation works.”
Physicists hope to discover other dark galaxies, to increase their understanding of one of the most puzzling building blocks of the universe.
Lucy’s fatal fall
Anthropologists have learned a great deal from Lucy, the fossilized 3.2 million–yearold hominid discovered in Ethiopia in 1974. Now they think they know how the 3-foot-tall, bipedal female kicked the bucket: by falling out of a tree. It was previously assumed that the many breaks and fractures in Lucy’s bones were the natural result of the fossilization process. But after taking high-resolution CT scans of the bones, researchers saw evidence of greenstick fractures, which typically only affect living bone. When they then created a 3-D model of Lucy’s shattered humerus and showed it to 10 orthopedic surgeons, nine of them concluded she had suffered a compound fracture, most likely from putting out her hand to break a fall. Scientists calculated that the force needed to produce the breaks and fractures was consistent with a 45-foot drop; since the bones show no signs of healing, they deduced the injuries must have been fatal. Though some paleontologists dispute the findings, arguing that most fossils have similar levels of bone damage, the study’s lead author, John Kappelman, insists the evidence is compelling. “I have taught this fossil since I was a grad student in the 1980s,” Kappelman tells NationalGeographic.com. “I knew these fractures were there—I just never thought to ask what had caused them.”
Surviving life on ‘Mars’
When most people imagine a trip to Ha waii, they don’t envision spending 12 months inside a 1,000-square-foot dome on the side of a volcano. But six volunteers with NASA emerged last week after doing exactly that, to help the space agency prepare for an eventual crewed expedition to Mars. The human experiment—the second longest of its kind after a 520-day Russian “mission”—was designed to simulate what life would be like for astronauts during an extended stay on the Red Planet. The crew had to put up with austere amenities, freeze-dried food, and a frustrating 20- minute com muni cations delay with the outside world. On the few occasions they were allowed to leave the isolated, solarpowered dome, they had to don a spacesuit. The six volunteers, who celebrated their release by gorging on pizza and fresh fruit, said the biggest challenges had been avoiding boredom and getting along with one another in such a confined space. “It is kind of like having roommates that are always there,” mission commander Carmel Johnston tells BBC.com. “You can never escape them.” But the crew also expressed confidence that astronauts could cope with the psychological challenges of such a long expedition. NASA already has plans for two more simulated missions, each lasting eight months.
How your dog understands you
Man’s best friend may understand us better than we thought. Groundbreaking new research has found that dogs process words and intonation using separate parts of the brain— the same way humans do, reports The Washington Post. Scientists trained 13 dogs of various breeds to lie still in an MRI machine. The pooches then listened to a trainer reciting positive phrases (such as “good dog”) as well as meaningless ones (like “however”), in both a neutral tone and a happy, “attaboy” tone. The scans showed that the dogs processed the meaningful words with the left side of their brain—the same hemisphere humans use to process language—and intonation with the right side. Furthermore, the canines’ dopamine “reward centers,” which respond to things like food or being petted, weren’t activated by meaningless phrases spoken in a positive tone of voice or by encouraging words spoken in a flat tone. “Dogs not only tell apart what we say and how we say it,” says Attila Andics, the study’s lead researcher, “but they can also combine the two, for a correct interpretation of what those words really mean.”
Health scare of the week
Zika causes deafness
Children whose mothers were infected with the Zika virus while pregnant are at risk not only for brain damage but also for hearing loss. A Brazilian study involving 70 infants diagnosed with Zika-related microcephaly—a severe birth defect that leads to underdeveloped brains—found that 6 percent of the babies suffered permanent sensorineural hearing loss, Reuters.com reports. The study’s authors recommended that all infants whose mothers were exposed to the mosquito-borne virus during pregnancy be routinely screened for delayed or progressive hearing loss, even if they showed no symptoms at birth. To prevent the transfusion of Zikainfected blood to pregnant women, the U.S. Food and Drug Administration last week advised blood banks across the nation to screen donated blood for the virus.