Much of the high-tech (高技術)stuff you use—TV， telephones， e-mail—relies on over a hundred satellites whizzing (飛速轉動) around Earth. Here's a look at five ways you use satellites.

★TelevisionIf you've watched TV， then you've used a satellite.Broadcast stations send images from Earth up to satellites as radio waves. The satellite bounces1 those signals， which can only travelstraight， back down to a satellite dish(拋物面天線) at a point on Earth closer to your house. Satellite transmission2 works sort of like a shot in a game of pool when you ricochet(彈跳) your ball off the side of the pool(落袋式臺球) table at an angle that sinks it into the right pocket.

★Weather News flash!A severe3 thunderstorm with dangerous lightning is approaching your town. How do weather forecasters know what's corning so they can warn the public? They use satellites equipped4 with cameras and infrared(紅外線的) sensors to watch clouds. Computers use constantlychangingsatelliteimagestotrackthe storm.

★Telephone As you talk back and forth with a relative overseas， yon might experience a delay of a quarter secondthe time it takes for your voices to be relayed by a satellite bounce.

★E-mailSatellites also bridge long distances over the Internet by transmitting e-mails. Communications satellites，for phones and the Internet， use a geostationary orbit(對地靜止軌道). That means that a satellite's speed matches Earth's rotation5 exactly，keeping the satellite in the same spot above the Earth.

★GPSDriving you to a party at a friend's house， your dad turns down the wrong street. You're lost. No problem! The car has a global6 positioning system (GPS) receiver. GPS is a network of 24 satellites.The receiver collects information from the satellites and plots its distance from at least three of them.It can show where you are on a digital map. Thanks to satellites， you will make it to the party on time!

我們使用的大多數(shù)高科技產(chǎn)品——電視、電話和電子郵件都依賴于100多個環(huán)繞地球運轉的人造衛(wèi)星。下面我們來看看人們利用人造衛(wèi)星的5種方式：

★電視如果你看過電視，你就用到了人造衛(wèi)星。電臺把圖像以無線電波的形式從地球傳送給衛(wèi)星，衛(wèi)星把那些只能直線傳送的信號反射給地球表面離你家較近的衛(wèi)星信號接受器。衛(wèi)星傳輸?shù)姆绞接悬c像打臺球，你從某個角度把球擊到球桌的一側，使球反彈落進正確的袋口。

★天氣預報突發(fā)性新聞事件！一場伴有危險閃電的強雷暴天氣正在接近你所在的城鎮(zhèn)。天氣預報員是如何得知這個情況從而向公眾發(fā)出警告的呢？他們利用裝有照相機和紅外線傳感器的衛(wèi)星來觀察云層。計算機始終不停地利用時刻變化的衛(wèi)星圖像來跟蹤暴風雨。

★電話 當你與海外親人接打電話時，你也許會感覺到1/4秒的聲音延遲——這個延遲是因為你的聲音要由衛(wèi)星傳播過去。

★電子郵件 衛(wèi)星還通過互聯(lián)網(wǎng)傳輸電子郵件，在遙遠距離之間架起了橋梁。用于電話和互聯(lián)網(wǎng)的通訊衛(wèi)星使用的是對地靜止的軌道。也就是說衛(wèi)星的速度正好與地球旋轉的速度相配合，這樣衛(wèi)星就可以總是固定在地球上方的某一點。

★全球定位系統(tǒng) 你爸爸開車送你去朋友家參加一個聚會，可是拐錯了方向，結果你們迷路了。沒問題!這輛車上裝有全球定位系統(tǒng)(GPS)接收機。全球定位系統(tǒng)是由24個衛(wèi)星組成的網(wǎng)絡系統(tǒng)。接收機從其中至少3個衛(wèi)星接受信息并確定該車輛與它們之間的距離。接收機可以用數(shù)字地圖顯示出你所在的位置。多虧有了衛(wèi)星，你可以準點參加聚會了！

注釋：

1．bounce vt. (經(jīng)通信衛(wèi)星等)反射，轉播

2．transmission n．傳送，輸送

3．severeadj. 猛烈的

4．equip vt. 配備，裝備

5．rotation n.自轉

6．global adj.全球的