Astronomer Seth Shostak of SETI, the guest for the middle two hours of the show, discussed the nature of our universe, the possibility of extraterrestrial life, and whether alien visitors to Earth would be friendly.

Shostak said the universe is filled with hundreds of billions of galaxies, each one containing hundreds of billions of star systems. Perhaps even more incredible, Shostak claims "there might be more planets than stars." After calculating the probabilities and examining evidence for vast amounts of liquid water on Mars and Jupiter's moons, Shostak concluded, "life [in the universe] is a very common phenomenon."

Based on his research, Shostak thinks we will make contact with extraterrestrials by the year 2025. His bold claim will be featured in the upcoming documentary "Naked Science: Alien Contact," which airs Nov. 24th on the National Geographic Channel.