Earthquakes vary in how destructive they are. A quake measuring 3 to 5 on the Richter scale is considered minor; 5 to 7 is moderate to strong; 7 to 8 is major; and 8 or more is catastrophic.
Runner's high occurs during moderate to intense aerobics, when natural chemicals called endocannabinoids activate the part of the brain associated with "feeling good."
Jim Lehrer is stepping aside from his role as anchor for the PBS NewsHour, though he will still appear to moderate the weekly analysis of columnists Mark Shields and David Brooks.
Jim Lehrer is stepping aside from his role as anchor for the PBS NewsHour, though he will still appear to moderate the weekly analysis of columnists Mark Shields and David Brooks.