Time is woven into the fabric of the universe as one of the dimensions in which we live our daily lives. But maybe it is only a brain state that we use to piece together events. Could it exist only in our minds? Your sense of time can be totally different than the person next to you. This and other theories illustrate that time is an illusion and does not really exist. The world's top physicists tackle this fundamental question, does time exist, and offer new ways to perceive the physical world.

In the last few years, the Red Planet has yielded up many new clues that life may have once existed there...and may even exist there today. There is now have proof that water once flowed on the surface, that Mars once had lakes, and that the frozen poles are mostly water, not carbon dioxide as previously thought. Mars has snow--an aurora--and lightning generated by dust storms. Most intriguing of all are the seasonal plumes of methane that just may point to bacteria living below the surface.

Our Sun has served Earth well for almost five billion years. It's bathed us with heat and energy. But like humans, our home star is mortal. In five billion years, it will stop nurturing its planetary offspring. The aging star will bloat out beyond the orbit of our planet incinerating all living things--including humans if we're still around.

Scorched by their proximity to the sun, Mercury and Venus are hostile worlds; one gouged with craters from cosmic collisions and the other a vortex of sulphur, carbon dioxide and acid rain. Prime examples of planets gone awry, do they serve as a warning for ominous scenarios that might someday threaten Earth?

Ignited by the power of the atom, burning with light, heat and wrath, stars are anything but peaceful. They collide, devour each other, and explode in enormous supernovas--the biggest explosions in the Universe.

Are we alone? SETI--the Search for Extraterrestrial Intelligence--is a privately funded project using radio telescopes and optical telescopes to scan the stars for signals.