The Earth is an amazing place. It provides everything needed to sustain billions of creatures, plants and human civilization. We owe our very existence today to the planet's turbulent past. Our world was formed by a series of cataclysms, from the most powerful blast in the Universe to a planetary collision that could have destroyed it. Yet without these events, the Earth would not exist. Nor we. Could the same extraordinary chain of events have created other earth-like planets elsewhere in the Universe? Inhabited by creatures like us? The odds seem slim. But the incredible story of the birth of our world reveals that earths must be abundant. The question is no longer "are we alone" but "how far away are our neighbors?"
Scientists are only now starting to unravel the secrets of comets. Often referred to as dirty snowballs, they contain ice and elements from the very start of the universe. Some theorize that a comet, crashing into our planet, brought with it the organic material that started life on Earth. Spacecraft continues to offer new information on their makeup, from bringing back samples from a comet's tail to direct contact when a NASA-launched craft slammed into the comet Tempel-1.
There is a new kind of weather to worry about, and it comes from our nearest star. Scientists are expecting a fit of violent activity on the sun which will propel billions of tonnes of superheated gas and pulses of energy towards our planet. They have the power to close down our modern technological civilisation - e.g. in 1989, a solar storm cut off the power to the Canadian city of Quebec. Horizon meets the space weathermen who are trying to predict what is coming our way, and organistions like the National Grid, who are preparing for the impending solar storms.