Giant 'Earth Stethoscope' Spies on Planet's Wonky Behavior

The planet is crawling with tiny spies: Hidden undersea microphones, instrument-clad satellites and infrared cameras are listening, watching and smelling all the action on planet Earth, from a migrating whale to a meteor crash. 

The international system, called the (CTBTO), has been spying on Earth for the past 18 years, but researchers are still finding fresh ways to interpret its data. In fact, about 1,000 scientists plan to discuss their findings at the CTBT Science and Technology conference, to be held June 22-26 in Vienna.

Here's a look at four things the CTBTO can see, hear and sniff on planet Earth.