Astronomers look into the future and see end of world in just 90 years
Civilisation has only a 50 per cent chance of surviving to 2100 without suffering a man-made catastrophic event, Lord Martin Rees, the Astronomer Royal, will warn at a debate in Edinburgh this week.
Lord Rees says mankind faces threats not only from self- inflicted problems such as global warming and over-population, but also from al-Qaeda-style terrorist groups obtaining nuclear weapons.
In the finale to the 2011 Edinburgh International Science Festival, Lord Rees is due to join his counterpart, the Astronomer Royal for Scotland, Professor John Brown, in the discussion "Fire in the Sky: Cosmic Threats to Earth".
The scientists have widely differing views with Prof Brown arguing threats are more likely to come from a random event from outer space such as an asteroid falling to earth.
Lord Rees - an atheist who earlier this month attracted controversy after winning the 1 million Templeton Prize, the world's richest prize, aimed at promoting religion - said: "The threat of global nuclear annihilation involving tens of thousands of bombs is thankfully in abeyance - but this prospect hasn't gone for good: we can't rule out by mid-century a global political realignment heading to a stand-off between new superpowers, that could be handled less well or less luckily than the Cuban missile crisis was.
"And the risk that smaller nuclear arsenals proliferate, and are used in a regional context, is higher than it ever was.
"Moreover, al-Qaeda-style terrorists might some day acquire a nuclear weapon. If they did, they would willingly detonate it in a city, killing tens of thousands of along with themselves, and millions would acclaim them as heroes."
Lord Rees, who based his prediction on analysis of potential threats from modern technology, added that the 21st century also "confronted us with grave new peril". He cited overpopulation and climate change as areas which while they "may not threaten a sudden world-wide catastrophe … are, in aggregate, worrying and challenging".
Meanwhile, Prof Brown said: "The threats Lord Rees and myself will be talking about are dangerous in different ways.
"Asteroids fall to earth on average 10-100 million years apart. It's been 65 million years since the last one, so one could happen next week to 60 million years from now. The probability in our lifetime is very small, making it low risk, high consequence.
"Solar flares, caused by a magnetic storms on the Sun, reach the Earth and can disrupt technology by 'frying' cable lines and knocking out GPS communications systems.
"Suppose they knocked out a quarter of the world's power supplies - that would create a potential threat to millions of people."There's more risk of a solar blast than an giant asteroid falling, but it would not have such high consequences."
• Fire in the Sky: Cosmic Threats to Earth, 23 April, 10am-5pm, Edinburgh University Student Union. Free. End of The World Ceilidh, same venue, 7:30pm to midnight. Tickets 10, 8.
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