听力文摘：是否真的存在零重力?

Weightlessness and zero gravity are two different things.

失重和零重力其实是两种完全不同的概念。

Think about it,the earth's gravity keeps the moon in orbit¹.

想想看，地球的重力使月球绕轨运行。

And astronauts are generally much closer to earth than the moon is, which means that the earth's pull on them has to be much stronger.

通常，宇航员其实比月球更为接近地球，这就意味着地球作用于他们的地心引力更强。

While we're on Earth, we feel our weight because, as the Earth's gravity pulls us into its center, the ground pushes back against our feet.

我们站立于地面上可以感受到重力，是因为地球本身的引力将我们拉向地心，但同时力又反作用于我们的双脚。

When astronauts orbit the earth, they're still subject to gravity,

宇航员绕地飞行时，他们仍然受到重力的作用。

but they're moving sideways so quickly that even though they're being pulled towards the earth, they're not getting any closer to the center of the planet².

但是由于他们始终侧向移动，而且速度如此之快，所以即使他们受到地心引力的影响，他们也并没有更接近地心。

In other words, they're basically³ in a state of constant free fall, and that's why they're weightless.

换而之，他们基本上是处于恒定的自由落体运动中，也就是他们失重的原因。

It just gets weaker.

它只会减弱。

And every object with mass, including you and me, has what's known as gravitational attraction.

每一个有重量物体，包括你我，都有万有引力。

Although you're subject to all those forces, the Earth's gravity masks their pull because the Earth is so large and so close.

虽然所有物体都受到万有引力的作用，但是地球本身的庞大，而且我们离地球如此之近，这就使得物体的重力被掩盖。

So moving away won't free you of the Earth's gravity.

因而，离开地球并不能让你脱离地心引力的影响。

All that would happen is that the Earth's pull would be masked by the pull of some other object, like Mars⁴.

但有可能会是这样的情况，地球的引力会被诸如火星的物体所掩盖。

1 orbit   

n.轨道；vt.使沿轨道运行；使进入轨道运行；vi.沿轨道运行，环行

参考例句：

• The space rocket was launched and went into orbit.宇宙火箭发射后进入轨道。
• We can draw the earth's orbit round the sun.我们可以画出地球绕太阳运行的轨迹。

2 planet   

n.行星

参考例句：

• Neptune is the furthest planet from the sun. 海王星是离太阳最远的行星。
• Rubbish, however, is only part of the problem of polluting our planet. 然而, 垃圾只是我们这个星球的污染问题的一个方面。

3 basically   

adv.基本上，从根本上说

参考例句：

• His heart is basically sound.他的心脏基本上健康。
• Basically I agree with your plan.我基本上同意你的计划。

4 Mars   

n.火星，战争

参考例句：

• As of now we don't know much about Mars.目前我们对火星还知之甚少。
• He contended that there must be life on Mars.他坚信火星上面一定有生物。