练习材料:
Lesson35-1 Space odyssey
The Moon is likely to become the industrial hub of the Solar System, supplying the rocket fuels for its ships, easily obtainable from the lunar rocks in the form of liquid oxygen. The reason lies in its gravity. Because the Moon has only an eightieth of the Earth's mass, it requires 97 per cent less energy to travel the quarter of a million miles from the Moon to Earth-orbit than the 200 mile-journey from Earth's surface into orbit!
This may sound fantastic, but it is easily calculated. To escape from the Earth in a rocket, one must travel at seven miles per second. The comparable speed from the Moon is only 1.5 miles per second.
应用配置:L0+L4
知识笔记:fuels/ lunar/ liquid/
练习感悟:用时26分。晚上完成。生词不多,用时也比较短,录制一条就过。
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