The Olympic flame will be lit in a ceremony in Olympia, Greece, on Thursday.

奥运圣火将于周四在希腊奥林匹亚被引燃。

The flame is lit from the rays of the sun, representing 'purity'
The flame is kindled¹ by a 'high priestess' who captures the morning sun's rays in a parabolic（抛物线的） mirror.

The ceremony comes amid political and economic turmoil² in the home of the Ancient Olympics, where a week-long leg of the relay will be held.

The flame flies to Britain on 18 May for a 70-day relay around the UK.

Locog Chairman Lord Coe, International Olympic Committee president Jacques Rogge and Hellenic Olympic Committee president Spyros Capralos will be in Olympia for the moment marking the countdown to London 2012.

Lord Coe told the BBC: "Today is the rallying call to the athletes - the best athletes of their generation - to come to London. That in itself is a big moment because it's the biggest sporting event in the calendar."

The lighting³ ceremony takes place in front of the ruins of the Temple of Hera from 11:30 local time (09:30BST)

The flame - an Olympic symbol meant to represent purity because it comes from the sun - is then placed in an urn⁴ and taken to the stadium where the ancient Olympic Games were staged.

There, it will light the London 2012 torch of Liverpool-born Greek world champion 10km swimmer Spyros Gianniotis, who will carry it on the first leg of the relay around Greece.

He will pass it on to Alex Loukos, 19, the first British torchbearer, a boxer⁵ and, in 2005, one of a delegation⁶ of east London schoolchildren who travelled to Singapore as part of London's final bid for the Games.

The torch is due to travel 2,900kms (1,800 miles) through the country, carried by 500 torchbearers, on a route circling the country and travelling out to Crete.