[人教版九年级英语听力]九年级英语听力：外星人来电

Suppose one day scientists pick up a transmissionthey think isgenerated by aliens.
假如有一天，科学家收到到外星人发来的信号该怎么办呢?

Now what? Do we build a landing strip andbreak outthe welcome wagon?

我们有建造飞碟起落跑道来欢迎它们吗?

Well here's the thing about picking up alienbroadcasts.

关于接收到外来广播的事情是这样的。

The receivers scientists are currently using to listento space noise are designed to find constantsignals,or signals that are pulsing at regular intervals.

科学家接者收目前会听航天噪音，然后找出不变信号或者找出那些常规跳动的信号。

But any message carried by these signals wouldprobably be lost because the receivers can't pickup the modulation, or rapid variations, in thebase signal.

但是任何携带信息的信号都可能丢失，因为接收者在信号基地不能收集到变调或快速变化的信号。

The SETI institute, which searches for extra terrestrial life, has compared picking up asignal'smodulation to picking up the sound of a flute when it's masked by the noise of a waterfall.

对外星智能的探索研究院，专门寻找外星生物。它他们对接受到信号的变调和被瀑布声掩盖的笛声做了比较。

Luckily, scientists would still have enough data to pinpoint where in the sky the transmissioniscoming from.

幸运的是，科学家们有足够的数据来确定信号广播的位置。

And any slow changes in the broadcast frequency would reveal information aboutthe rotationand movement of the aliens' planets.

广播频率的细微变化都会揭露外星人星球的旋转和运动情况。

Okay, but how will we know if they are friendly?

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