托福听力摘选：月球与火星的重力

Located at the NASA Research Center in Iowa is a 5,000-gallon vat of water, and inside the tank is an underwater treadmill designed by Dava Newman, an aerospace engineer. For four years Newman observed scuba divers as they simulated walking on the Moon and on Mars on her underwater moving belt. She wanted to discover how the gravity of the Moon and of Mars would affect human movement. To do this, Newman attached weights to the divers and then lowered them into the tank and onto the treadmill. These weights were carefully adjusted so that the divers could experience underwater the gravity of the Moon and of Mars as they walked on the treadmill. Newman concluded that walking on Mars will probably be easier than walking on the Moon. The Moon has less gravity than Mars does, so at lunar gravity, the divers struggled to keep their balance and walked awkwardly. But at Martian gravity, the divers had greater traction and stability and could easily adjust to a pace of 1.5 miles per hour. As Newman gradually increased the speed of the treadmill, the divers took longer, graceful strides until they comfortably settled into an even quicker pace. Newman also noted that at Martian gravity, the divers needed less oxygen. The data Newman collected will help in the future design of Martian space suits. Compared to lunar space suits, Martian space suits will require smaller air tanks; and, to allow for freer movement, the elbow and knee areas of the space suits will also be altered.

1. gallon: n. AmE a unit for measuring liquids, equal to 3.785 litres 加仑(等于3.785升)

2. vat: n. [C]a very large container for storing liquids such as whisky or dye, when they are being made(酿酒、盛染料用的)大缸，大桶

3. tank: n. [C]a large container for storing liquid or gas(盛放液体或气体的)大容器

4. treadmill: n. [C]a mill worked in the past by prisoners treading on steps fixed to a very large wheel(过去用以惩罚犯人的)踏车

5. aerospace: adj. involving the designing and building of aircraft and space vehicles 航空和航天(器制造)的 n.[U]the industry that designs and builds aircraft and space vehicles 航空和航天工业，航天工业

6. scuba diving: n. [U]the sport of swimming under water while breathing through a tube connected to a container of air on your back 斯库巴潜泳，水肺潜泳(戴自携式潜水呼吸器潜泳)

7. simulate: v. to make or produce something that is not real but has the appearance of being real 模仿，模拟

8. Martian: adj. of or relating to the planet Mars 火星的

9. stride: n. [C]a long step 大步，阔步

10. elbow: n. [C]the joint where your arms bends 肘