[al:新概念英语（四）] [ar:MP3 同步字幕版（英音）] [ti:Space Odyssey] [by:更多学习内容，请到chazidian.com搜索“新概念”] [00:01.55]Lesson 35 [00:03.49]Space odyssey [00:12.30]When will it be possible for us to think seriously about colonising Mars? [00:19.69]The Moon is likely to become the industrial hub of the Solar System supplying the rocket fuels for its ships, [00:27.91]easily obtainable from the lunar rocks in the form of liquid oxygen. [00:33.59]The reason lies in its gravity. [00:36.49]Because the Moon has only an eightieth of the Earth's mass, [00:40.86]it requires 97% less energy [00:44.05]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! [00:53.22]This may sound fantastic, but it is easily calculated. [00:58.20]To escape from the Earth in a rocket, one must travel at seven miles per second. [01:04.38]The comparable speed from the Moon is only 1.5 miles per second. [01:10.68]Because the gravity on the Moon's surface is only a sixth of Earth's (remember how easily the Apollo astronauts bounded along), [01:19.48]it takes much less energy to accelerate to that 1.5mps than it does on Earth. [01:27.36]Moon dwellers will be able to fly in space at only three percent of the cost of similar journeys by their terrestrial cousins. [01:36.69]Arthur C.Clark once suggested a revolutionary idea passes through three phases: [01:43.13]1. 'It's impossible--don't waste my time.' [01:47.69]2. 'It's possible, but not worth doing.' [01:53.00]3. 'I said it was a good idea all along.' [01:58.78]The idea of colonising Mars--a world 160 times more distant than the Moon--will move decisively from the second phase to the third, [02:09.19]when a significant number of people are living permanently in space. [02:14.41]Mars has an extraordinary fascination for would-be voyagers. [02:19.02]America, Russia and Europe are filled with enthusiasts--many of them serious and senior scientists who dream of sending people to it. [02:30.55]Their aim is understandable. [02:33.94]It is the one world in the Solar System that is most like the Earth. [02:38.93]It is a world of red sandy deserts (hence its name--the Red Planet), [02:45.03]cloudless skies, savage sandstorms, chasms wider than the Grand Canyon and at least one mountain more than twice as tall as Everest. [02:56.38]It seems ideal for settlement.