4x1 - Glacier Meltdown

January 31, 2007

4x2 - Destructive Forces

February 21, 2007

4x3 - Stone Age Apocalypse

February 28, 2007

4x4 - Comets

March 7, 2007

4x5 - Prehistoric Americans

March 14, 2007

4x6 - Deep Space Probes

March 27, 2007

Great distances and dangerous environments make robotic spacecraft the best way for scientists to explore our solar system. Acting as our eyes and ears, these probes have revealed secrets about the distant planets and their moons, their surfaces, weather and environments.

4x7 - Dino Meteor

April 12, 2007

4x8 - Planet Storm

April 26, 2007

4x9 - Polar Apocalypse

April 1, 2007

4x10 - Killer Lakes

May 3, 2007

Since the death of 1,700 people near a lake in Africa, scientists have uncovered a terrifying series of hazards in lakes across the world.

4x11 - Ring of Fire

August 2, 2007

4x12 - Alien Safari

August 9, 2007

With advanced technology in their hands, astronomers and scientists may now be capable of detecting extraterrestrial life in the universe. In fact, some think the proof may be found in as little as a decade. Astronomers involved in the effort, including those at SETI (Search for Extraterrestrial Intelligence), discuss the possibilities and the likely spots for finding life outside of Earth.

4x13 - Hyper Hurricanes

October 18, 2007

4x14 - Dangers of the Deep

October 25, 2007

4x15 - Solar Force

October 30, 2007

4x16 - Birth of the Solar System

November 6, 2007

Thanks to new developments in the technology of astronomy, scientists have been able to collect new information, giving them clues to how our solar system was formed.

4x17 - Hubble Trouble

November 6, 2007