London missed obliteration by four hours
Friday 17 September 1999
Had the comet entered the atmosphere four hours earlier it would have exploded over the British capital, which lies on the same latitude, and killed millions of people. In Siberia, 2,000 sq km of forest were destroyed.
Such "comet hits" are not rare, occurring on average about once every 100 years. We may get only one year's warning that such an object is threatening the Earth, and none if it approaches us from the southern part of the sky, said Dr Matthew Genge of the Natural History Museum.
"The effect of a comet breaking up in the atmosphere would be like a nuclear airburst," said Dr Genge. "In Tunguska, the comet exploded 4km (2.5 miles) above the ground, and the trees were burnt for miles around."
Had that comet, which was about 70m in diameter, fallen towards London, people on the ground would first have seen bright lights in the sky. Moments later the heat from the comet's friction with the air would have meant anything combustible - including skin - would have burst into flame.
Within seconds the ice at its heart would have turned into superheated steam and exploded, sending out a shockwave and flattening buildings for miles. The whole event would take less than a minute.
"It would have left no crater, because nothing would have actually hit the Earth," said Dr Genge. "It would have posed quite a problem trying to understand what had happened."
The Tunguska event is thought to have killed only a few woodcutters. It still counts as one of modern humanity's narrowest escapes from extraterrestrial destruction. Comets, made of ice and mud, pose a greater risk to us than asteroids, which are usually solid iron or rock and would fall without breaking up.
"We know that fragments of comets about 10m across enter the atmosphere four or five times a year, because US military spy satellites began detecting them - and mistaking them for 20-kiloton nuclear bombs going off - in the 1970s," said Dr Genge.
- 1 I've been called an abusive and dangerous parent, when all I did was listen to my transgender child
- 2 Migrant crisis: Greek soldier saved 20 people singlehandedly off Rhodes beach
- 3 Sofyen Belamouadden murder: The inside story of a crime that horrified Britain
- 4 Company breaks open Apple Watch to discover what it says is 'planned obsolescence'
- 5 UK weather: Britain braced for snow as arctic air mass moves in
Migrant crisis: Greek soldier saved 20 people singlehandedly off Rhodes beach
Russian hack of President Obama's emails worse than previously admitted
Aaron and Melissa Klein: Oregon anti-gay bakers ordered to pay $135,000 after refusing to make cake for same-sex wedding
UK weather: Britain braced for snow as arctic air mass moves in
Nepal earthquake: US Pastor Tony Miano sparks outcry by suggesting Nepalis should convert and not rebuild their 'pagan shrines'
General Election 2015: Chuka Umunna on the benefits of immigration, humility – and his leader Ed Miliband
The sickening truth about food banks that the Tories don't want you to know
Migrant boat disaster: Ukip candidate mocks victims in sickening Twitter post
Nigel Farage wants the BBC to stop making programmes like Doctor Who, Strictly Come Dancing, and Top Gear
Global warming: Scientists say temperatures could rise by 6C by 2100 and call for action ahead of UN meeting in Paris
General Election 2015: Britain would become a 'communist dictatorship' under Ed Miliband and Nicola Sturgeon, claims wife of Michael Gove
£26000 per annum: Recruitment Genius: Haulage company based on the Thorpe Indu...
£25000 - £27000 per annum: Recruitment Genius: An SME based in East Cheshire, ...
£20000 - £22500 per annum + OTE £30K: SThree: SThree Group have been well esta...
£28000 - £40000 per annum: Recruitment Genius: A fantastic opportunity has ari...