| 1. | Usually they burn up about 100km above the earth .
它们常在地球上空约100公里处被烧毁。 |
| 2. | An aircraft in steady flight over the earth is just as suitable an inertial frame of reference as the earth itself .
在地球上空稳定飞行的飞机，正如地球本身那样，也可作为惯性参照系。 |
| 3. | Nitrogen forms most of the earth ' s air
地球上空气的大部分成分是氮气。 |
| 4. | The huge rocket that lifted the orbiter from earth dropped into the atlantic ocean after about four minutes
巨大的火箭跟人造卫星分离后于四分钟后从地球上空落入大西洋。 |
| 5. | Blue light gets scattered ( spread ) around much more than all the other colors from the sun , causing the sky to appear blue
七色阳光都来至太阳，只是到达地球上空时因散射原因，蓝光更多，因而天空呈蓝色。 |
| 6. | Meteorological satellites carry sensors that are pointing towards the ground , enabling them to have bird eye view of the globe from the space
气象卫星在地球上空远处运行。它所带的感应器指向地球，从而拍摄地球的鸟瞰图。 |
| 7. | Meteorological satellites carry sensors that are pointing towards the ground , enabling them to have bird eye view of the globe from the space
气象卫星在地球上空远处运行。它所?带的感应器指向地球，从而拍摄地球的鸟瞰图。 |
| 8. | But , with about 2 , 000 thunderstorms taking place above the earth every minute of the day and night , there ' s enough activity to produce about 100 lightning strikes on earth every second
但是，由于在地球上空每分钟产生大约2 , 000次雷雨现象，就有足够的天气活动使地上每秒钟发生大约100次闪电。 |
| 9. | The idea of maintenance robots originated after a 1990 study concluded that an orbital station would require 75 percent more space - walking time than originally planned
以机器人从事维修工作的点子，源自1990年一份报告，它的结论是：地球上空的轨道太空站需要舱外活动的时间，比预估的要多75 % 。 |
| 10. | Such satellites ? maintaining their steady sweeps as the earth revolves beneath them ? cover all parts of the globe and hence are ideal for weather observation , communications and other tasks
这些卫星处在平稳旋转的地球上空，几乎可以对全球的所有地区进行稳定的扫描，因此能很好地完成气象观察、通讯以及其它任务。 |
