Lightning
is an atmospheric discharge of electricity, usually accompanied by thunder,
which typically occurs during thunderstorms, and sometimes during volcanic
eruptions or dust storms.
In the
atmospheric electrical discharge, a leader of a bolt of lightning can travel at
speeds of 60,000 m/s (220,000 km/h), and can reach temperatures approaching
30,000 °C (54,000 °F), hot enough to fuse silica sand into glass channels known
as fulgurites which are normally hollow and can extend some distance into the
ground.
There
are some 16 million lightning storms in the world every year.
For an
American, the chance of being struck by lightning is approximately 1 in 576,000
and the chance of actually being killed by lightning is approximately 1 in
2,320,000.
Lightning
can also occur within the ash clouds from volcanic eruptions, or can be caused
by violent forest fires which generate sufficient dust to create a static
charge.
How
lightning initially forms is still a matter of debate: Scientists have studied
root causes ranging from atmospheric perturbations (wind, humidity, friction,
and atmospheric pressure) to the impact of solar wind and accumulation of
charged solar particles.
Ice
inside a cloud is thought to be a key element in lightning development, and may
cause a forcible separation of positive and negative charges within the cloud,
thus assisting in the formation of lightning.
♣ 미국 찰스턴(Charleston) Arthur Ravenel Bridge 2008년 4월 15일
♣ 미국 라스베가스 Mandalay Bay Resort 2008년 6월 26일
♣ 미국 밀워키(Milwaukee) 2008년 11월 7일
♣ 호주 southwest of Darwin 2007년 2월 16일
♣ 독일 Steinenbronn 2007년 6월 21일
♣ 호주 Swifts Creek 2007년 10월 4일
♣ 프랑스 Eiffel Tower, Paris 1902년
