Neil deGrasse Tyson explains radioactive decay. He explains how we can determine the age of a rock using meteorites and illustrates that atoms undergo nuclear transmutations over time until they become stable elements.

Per Thomas Edison's suggestion, The Secret Labbers visit Frederick Soddy to better understand radioactive decay. Watch Thomas Edison's Secret Lab on Netflix, the Kid Genius channel on Xfinity, public television and DVD. Visit EDISONSECRETLAB.COM for games, videos, downloads and more!

Charlie explains radiocarbon dating and how it is used to calculate the approximate age of an object. To make his explanation more concrete, he uses an analogy involving a refrigerator and the number of ice cubes in it.

Bill Nye explains why it gets colder as one travels up through the atmosphere. He uses miniature replicas of a city and a mountain to support his explanation. Bill also briefly touches upon the lapse rate.

Lois removes the krytonite to save Superman. Superman is weak but flies above the clouds to take in energy from the Sun and recharge.