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.