We feel it every moment of our lives but for physicists, gravity is the longest running unsolved mystery of the universe. Why do all objects that have mass pull on one another? Cutting-edge theories are proposing unexpected answers: Gravity could be another force in disguise, a thermodynamic mirage, or even, a shadow of a hidden holographic universe. If so, the force that holds us to the surface of the earth, and holds the earth in orbit around the sun, may be a trick of the mind. We feel it, but it may not be real. Is Gravity an Illusion?

We float along the river of time. But does that river have a source? Where did time come from? Some believe time and space are one thing, and the Big Bang started the cosmic clock. Others believe the universe existed for almost half a million "years" before light could move and time began. Still others say time is older than our universe. But what if time itself is an illusion? Incredible new experiments may hold the answer. One groundbreaking experiment gives us the power to punch holes in time…and another may create a machine that operates outside time’s boundaries!

An individual’s life journey interweaves with many others. Those who are successful know when to fight or back down, when to cooperate or to go it alone and how to manipulate and deceive. But power is the ultimate prize: animals will use any means to rise through the ranks and win the game of life.

Researchers discuss mythic ancient treasure and curses including King Solomon's Ring, lost Aztec treasure, and the Omphalos.

Brian explores the physics of the size of life through some close encounters with Australia's wildlife. From swimming with great white sharks to tracking red kangaroos, he discovers that the size you are profoundly affects the life you lead and, ultimately, how long you have to enjoy it.

This episode examines the end of and the period immediately after World War II. It looks at Stalin's efforts to seize control of Poland and Eastern Europe, Democratic part bosses efforts to drop Henry Wallace from the 1944 presidential ticket, and British efforts to maintain their colonial holdings after the war.