Killers Of The Cosmos

Every day Earth is bombarded by 100 tons of meteoroids from space. Most burn up in the atmosphere. Sometimes they hit, exploding with a force bigger than any nuclear bomb. It was one rock that wiped out the dinosaurs -- does the same fate await humans?

Black holes were only theoretical until recently. And there are probably millions of them in the galaxy. Worse still, some are rogue, speeding through space with the potential to destroy Earth.

A spy satellite chances on a threat from deep space -- lethal blasts of deadly gamma rays. When a massive star dies, it can direct a blast of radiation that would obliterate life on Earth.

Right now, there are 6,000 satellites orbiting Earth, moving faster than any speeding bullet. Sixty percent are defunct and out of control. At any time, a collision could set off a chain reaction and cause a global communication meltdown.

There are hundreds of billions of planets out there. Maybe aliens exist, but humans just haven't found them yet. They might even be killers who want to invade and plunder Earth, threatening human life.

Everything comes to an end, even a universe. So, how will it all end? Will gravity make it collapse, or will it expand forever? And now there's a third alternative; dark energy is a mysterious impulse that could tear the very fabric of the universe apart.