Science briefs: What a dog's tail wagging tells another dog

A European satellite that mapped Earth's gravitational field in exquisite detail soon will be pulled down by gravity to its fiery destruction. Where and when it will crash no one knows. It could be almost anywhere on the globe. About 25 to 45 fragments of the 1-ton spacecraft are expected to survive all the way to the surface, with the largest perhaps weighing 200 pounds. It is the latest in a parade of spacecraft falling from the sky in what are worryingly called "uncontrolled entries." About 100 tons of debris will fall from the sky this year alone. There are, however, no known instances in which anyone has been injured by space debris. "It's rather hard to predict where the spacecraft will re-enter and impact," said Rune Floberghagen, the mission manager for the European Space Agency's Gravity Field and Steady-State Ocean Circulation Explorer, or GOCE (pronounced GO-chay). "Concretely, our best engineering prediction is now for a re-entry on Sunday, with a possibility for it slipping into early Monday." GOCE ran out of propellant last month, and has been dropping about 2.5 miles a day.

When dogs wag their tails, they can convey not just happiness but also a wide array of emotions. As Italian researchers reported in 2007, a wag to the left indicates negative emotions; a wag to the right indicates positive ones. Now the scientists have found that dogs agree.

In a study reported in the journal Current Biology, the researchers had dogs watch videos of other dogs wagging their tails. When watching a tail wag to the left, the dogs showed signs of anxiety, like a higher heart rate. When the tail went in the opposite direction, they remained calm. Taken together, the Italian studies suggest that dogs, like humans, have asymmetrically organized brains, said study author Giorgio Vallortigara, a neuroscientist at the University of Trento. "The emotions are associated presumably with activation of either the right or left side of brain," he said. Left-brain activation produces a wag to the right, and vice versa. Vallortigara said, "It's simply a byproduct of the asymmetry of the brain," and dogs learn to recognize the pattern over time.