LiveScience: Like a fairy-tale beanstalk, a tree can grow and grow until it scrapes the sky. Instead of slowing down as the centuries add up, old trees speed up their growth, according to a study published on Jan. 15 in the journal Nature. "Trees keep growing like crazy throughout their life span," said Nate Stephenson, lead study author and a forest ecologist with the U.S. Geological Survey (USGS) in Three Rivers, Calif. The results of the survey of 403 tree species around the world suggest that trees...