时间:2018-12-30 作者:英语课 分类:国家地理2007年


英语课
The image is unmistakable. Lightning is one of the most incredible natural phenomenons and one that scientists are still learning about. It's a common occurrence during summer when the heat of the day is broken by strokes of lightning. Worldwide, it's estimated lightning occurs 50 to 100 times a second. The greatest concentrations of lightning strikes are in Central Africa, the Himalayas and South America. Lightning is often seen flashing between storm clouds and the earth. The bursts of light are pure electricity.

Scientists don't fully 1 agree on what actually causes the electrical charge to be dispersed 2. But it is generally thought that lightning often occurs within the downdrafts and updrafts of thunderstorms. Lighter 3 particles moving toward the top of clouds become positively 4 charged, while heavier particles heading toward the bottom become negatively charged. When the positive and negative charges grow large enough, lightning is released between these regions.

Most of the lightning takes place within the cloud but some strikes the earth in bold flashes. In these cases, the charge escapes the cloud, making a branching path that reaches for the ground. The energy of the lightning strike contains hundreds of millions of volts 5 and lasts only a fraction of a second. What seems to be a single flash is actually a series of return strokes of electrical energy, reaching back up into the clouds. The path reaches temperatures of around 50,000 degrees Fahrenheit 6. This extreme heat creates the booming thunderclap as excessive pressure within the lightning path expands at supersonic rates on return strokes.

In the US, lightning occurs most often in Florida. Its hot moist climate is perfect for creating thunderclouds which produce lightning. But lightning is a deadly natural phenomenon, taking nearly 100 lives a year on average in the US, more than hurricanes or tornados 7. During electrical storms, experts warn that people should seek shelter inside a building or hardtop automobiles 8 and if caught in the open, avoid high ground and isolated 9 trees. Lightning is a powerful force of nature and one to be cautious of.


adv.完全地,全部地,彻底地;充分地
  • The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气,然后全部呼出。
  • They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。
adj. 被驱散的, 被分散的, 散布的
  • The clouds dispersed themselves. 云散了。
  • After school the children dispersed to their homes. 放学后,孩子们四散回家了。
n.打火机,点火器;驳船;v.用驳船运送;light的比较级
  • The portrait was touched up so as to make it lighter.这张画经过润色,色调明朗了一些。
  • The lighter works off the car battery.引燃器利用汽车蓄电池打火。
adv.明确地,断然,坚决地;实在,确实
  • She was positively glowing with happiness.她满脸幸福。
  • The weather was positively poisonous.这天气着实讨厌。
n.(电压单位)伏特( volt的名词复数 )
  • The floating potential, Vf is usually only a few volts below ground. 浮置电势Vf通常只低于接地电位几伏。 来自辞典例句
  • If gamma particles are present, potential differences of several thousand volts can be generated. 如果存在γ粒子,可能产生几千伏的电位差。 来自辞典例句
n./adj.华氏温度;华氏温度计(的)
  • He was asked for the boiling point of water in Fahrenheit.他被问到水的沸点是华氏多少度。
  • The thermometer reads 80 degrees Fahrenheit.寒暑表指出华氏80度。
n.龙卷风,旋风( tornado的名词复数 )
  • And the national weather service reports several tornados touch down. 国家气象中心报告预测龙卷风将来袭。 来自互联网
  • They had stock footage of lightning, tornados, and hurricanes. 他们存有关于闪电、龙卷风和飓风的电影胶片。 来自互联网
n.汽车( automobile的名词复数 )
  • When automobiles become popular,the use of the horse and buggy passed away. 汽车普及后,就不再使用马和马车了。 来自《简明英汉词典》
  • Automobiles speed in an endless stream along the boulevard. 宽阔的林荫道上,汽车川流不息。 来自《现代汉英综合大词典》
adj.与世隔绝的
  • His bad behaviour was just an isolated incident. 他的不良行为只是个别事件。
  • Patients with the disease should be isolated. 这种病的患者应予以隔离。
学英语单词
a change of tide
al ashuriyah
alister
america's
aminodiborane
analog differential analyzer
annulus fibrocartilagineus membranae tympani
aris
atmosphere pressure
baste someone's coat
bifurcation area
blackshere
bleed sb dry
Bluff Knoll
brush friction
bsub
Burnett I.
bust it
byphanamine
carbonate free burden
chasmo phyte
classification of states
cletocamptus deitersi
common environmental effect
continental affinity
cyberforensics
daidles
dermatitis dysmenorrhoeica
diphosphinine
eddy drag
editability
EPFS
EPXMA
filter(ing) disk(s)
fluctuation effect
focusing lamp
fountain-pen type exposuremeter
gauge device
give someone a run for his or her money
He that sups with the devil must have a long spoon.
industrial fermentation
internally heated oven
isthmoids
kosschen
Kutthung
laminadens
law of ocean-going trade
lead babbit alloy
limited current circuit
Magbuntuso
Makalu
maximum penetration force of cutting edge
metadurain
monetary law
montana ruby
multi-span structure
muscular strain
new network
non compos (mentis)
nonhyphenated
noughts-and-crosses
offring
outvotes
peeled back
percil
personal lubricants
photoinduced
physical revolution
planetoids
plans of attack
potable water supply system
Prairie Provinces
prestressed tie rod
pyrans
Rathke's pouch tumor
roady
robotic vacuum
rudden
segmental type
simulated interception
sintered calcium sodium phosphate fertilizer
solomon guggenheims
staidly
steam raising equipment
steel and iron slag cement
stone plate
straighteners
Sundok
third-party mediation
timeperiod
trajactory acceptance
transflex screen
trichoepithelioma papulosum multiplex
twin-passage bucket elevator
unboxable
uncommongoods.com
undersecretaryship
unsterile
vaporization room
VMSnet
Volscian
weighting matrix