Researchers in California have unraveled one of life's enduring mysteries: Why do shoelaces come undone? When running, the foot hits the ground at about seven times the force of gravity. The knot stretches and relaxes in response. As it loosens, swinging legs apply an inertial force on the free ends of the laces, and pretty soon they are flopping around like overcooked spaghetti. To fix the problem, fix the knot. A weak knot will typically have one loop pointing toward the toes and one toward the ankle. A stronger knot, usually based on a square knot, typically has the loops oriented on opposite sides.

Milestone in switching on big X-ray laser

Scientists say they've reached a milestone on the way to switching on the world's biggest X-ray laser, designed to capture images of structures and processes at the atomic level. The DESY research center near Hamburg, Germany, said it successfully fired electrons through a 1.3-mile particle accelerator. It plans to increase the energy of the electrons and generate the first X-ray laser light next month. Once the European XFEL project begins operation later this year it will produce up to 27,000 X-ray laser flashes per second. Scientists hope it will open up new areas of research, like mapping the atomic details of viruses and deciphering the molecular composition of cells.

Ocean floor eroding as coral reefs die

U.S. government scientists have found a dramatic impact from the continuing decline of coral reefs: The seafloor around them is eroding and sinking, deepening coastal waters and exposing nearby communities to damaging waves that reefs used to weaken. The new study examined reefs in Hawaii, the Florida Keys and the U.S. Virgin Islands, finding seafloor drops in all three locations. Coral reefs naturally generate sand as hard coral skeletons die, and their calcium carbonate bodies become the next layer of the seafloor. Meanwhile, the living tops of coral columns grow taller and taller, which allows them to keep pace in eras of rising seas. But as corals are subjected to more and more assaults from a combination of global climate change, local pollution, and direct human-caused damage, this natural dynamic appears to have been undermined, and seafloor accretion has swung to erosion.

News services