Man’s First Real Invention
Man’s first real invention，and one of the most important inventions in history，was the wheel．All transportation and every machine in the world depend on it．
The wheel is the simplest yet perhaps the most remarkable of all inventions，because there are no wheels in nature—no living thing was ever created with wheels．How，then，did man come to invent the wheel？
Perhaps some early hunters found that they could roll the carcass of a heavy animal through the forest on logs more easily than they could carry it．However，the logs themselves weighed a lot．
It must have taken a great prehistoric thinker to imagine two thin slices of log connected at their centers by a strong stick．This would roll along just as the logs did，yet be much lighter and easier to handle．Thus the wheel and axle came into being，and with them the first carts．
人类第一项真正的发明
轮子是人类第一项真正的发明，也是历史上最重要的发明之一，世界上的一切交通工具和每一部机器都有赖于它。
在一切发明中，轮子是最简单的，然而也许是最了不起的一项发明，因为自然界中没有轮子——带轮子的生物还没有被创造出来过。那么，人类是怎样发明轮子的呢？
也许是一些早期的猎人发现了这一点：依靠圆木的滚动，把沉重的动物尸体推出森林，比肩扛背驮要容易。不过，圆木本身也够重的了。
这一定使一位史前的伟大思考者产生想像，用一根结实的棍棒把两块圆木的薄片从中心连接起来，这玩意儿也恰恰像圆木一样能向前滚动，不但要轻得多，而且更容易驾驭。这样轮子和轴便应运而生，随之出现了第一批手推车。
The AirCushioned Vehicle ThatTravels Clear out of Sea and Land
The aircushioned vehicle is not an airplane，since it does not have wings．It is neither a ship nor an automobile，since it travels clear of sea and land．It has a conventional gasoline engine，but no wheels．How does it travel？What keeps it in the air？
Under the air car is an air chamber with a large propeller parallel to the ground．The gasoline engine supplies power that causes the propeller to whirl．This fills the chamber with air．Some of the air is forced toward the ground through tiny holes around the edges of the car．
These air jets create a wall that keeps the air from escaping from the chamber．As more and more air crowds into the chamber，the molecules of air become compressed．Their pressure becomes so strong that it lifts the car off the ground．
Once the car is floating，the driver releases some of the compressed air．This makes the car speed forward．
脱离海面和陆地行驶的气垫船
气垫船不是飞机，因为它没有双翼。它不是轮船，也不是汽车，因为它脱离海面和陆地行驶。气垫船装有常规的汽油发动机，但没有轮子。它是怎样行驶的呢？是什么使它悬在空中的呢？
气垫船下面是一个空气箱，里面装有一个与地面平行的大螺旋桨。汽油发动机供能后，螺旋桨便旋转起来，这就使气箱内充满了空气。部分空气通过气垫船边缘的小孔被压向地面。
这些喷射出的气流形成一道屏障，阻止空气从气箱逸出。由于越来越多的空气聚集在气箱内，空气分子受到压缩。正是这些空气分子的强大压力使气垫船脱离地面。
当气垫船浮动时，司机释放出一部分压缩空气，使气垫船高速向前飞行。
A Dream Laboratory at theUniversity of Chicago
A unique laboratory at the University of Chicago is busy only at night．It is a dream laboratory where researchers are at work studying dreamers．Their findings have revealed that everyone dreams from three to seven times a night，although in ordinary life a person may remember none or only one of his dreams．
While the subjects—usually students—sleep，special machines record their brain waves and eye movements as well as the body movements that signal the end of a dream．Surprisingly，all subjects sleep soundly．
Observers report that a person usually fidgets before a dream．Once the dream has started，his body relaxes and his eyes become more active，as if the curtain had gone up on a show．As soon as the machine indicates that the dream is over，a buzzer wakens the sleeper．He sits up，records his dream，and goes back to sleep—perhaps to dream some more．
Researchers have found that if the dreamer is wakened immediately after his dream，he can usually recall the entire dream．If he is allowed to sleep even five more minutes，his memory of the dream will have faded
芝加哥大学的梦幻实验室
芝加哥大学的一座独特的实验室只在夜间忙碌。它是一座梦幻实验室，研究人员们在那里对做梦者进行研究。研究成果揭示：每个人一夜做梦3至7次，虽然在日常生活中，一个人对做过的梦可能全然没有记忆，或仅能记住个把而已。
当受实验者——通常是学生——睡眠时，特殊的机器不仅把预示梦将结束的身体动作记录下来，也把受实验者的脑波和眼睛的活动情况记录下来。说也奇怪，受实验者都睡得很香。
观察家们报告说，一个人在做梦前总是要翻身的。梦一开始，身体便呈放松状态，眼睛变得更为活跃，好像一场演出已经启幕一样。要是机器显示梦已结束，蜂音器便唤醒熟睡者。他坐起来，记下他的梦中情景，然后再入睡乡——也许去做更多的梦。
研究人员们发现，假如做梦者在梦后立即被唤醒，通常他能回忆起整个梦的内容；如果让他继续睡，即使只多睡5分钟，他对那梦的记忆也会消失。
How the Word Radar Was Coined
Under proper conditions，sound waves will be reflected from a hillside or other such obstruction．Sound travels at the rate of about onefifth of a mile per second．If the hill is eleven hundred feet away，it takes two seconds for the sound to travel to the hill and back．Thus，by timing the interval between a sound and its reflection（the echo），you can estimate the distance to an obstruction．
During World War Ⅱthe British used a practical application of this principle to detect German planes on their way to bomb London long before the enemy was near the target．They used radio waves instead of sound waves，since radio waves can penetrate fog and clouds．The outnumbered Royal Air Force （RAF）always seemed to the puzzled Germans to be lying in wait at the right time and never to be surprised．It was radio echoes more than anything else that won the Battle of Britain．
Since the radio waves were used to tell the direction in which to send the RAF planes and the distance to send them （their range of flight，in other words），the device was called radio directing and ranging，and from the initials the word radar was coined．
“雷达”一词是怎样创造出来的
在适当条件下，声波会从山坡或其他类似的障碍物反射回来。声音以大约每秒1／5英里的速度传播。假如小山在1100英尺之外，声音传到小山又反射回来需要两秒钟。这样，通过计算声音与其回声的间隔时间，你便能推算出某一障碍物有多远。
第二次世界大战期间，英国人实际运用了这一原理，使前去轰炸伦敦的德国飞机早在接近目标之前便被探测出来。他们使用的是无线电波，而不是声波，因为无线电波能穿透浓雾和云层。在感到迷惑的德国人看来，数量上处于劣势的皇家空军似乎总是适时地守候在那里，而从未被突然袭击过。不列颠之战的胜利主要是靠着无线电回声，而不是靠别的什么。
由于无线电波被用来测定派遣皇家空军飞机的方向和距离（或称航程范围），这一装置被称为“无线电定向和测距器”（radio directing and ranging）从（这几个字的）首字母产生了radar（雷达）一词。
Europe’s One and Only Atomic City
In Switzerland．six miles west of Geneva，lies a collection of laboratories and buildings，and，most curious of all，a circular mound of earth more than 650feet in diameter．This cluster has unique importance．It is Europe’s one and only atomic city dedicated to investigating the atom peaceful purposes．