Move over, Neil deGrasse Tyson. Take a hike, Bill Nye. We have a new science guy now and his name is Stephen Colbert. Today, we learn about skinny sharks, tiny knots, shark regenerating, your brain on triatholons, the invasion of the cicadas and - most importantly - why do dogs wag their tails. I know the answer to that last one. My dogs wag because I've got treats for them.

Open thread below...