1 "Time is an illusion. Lunchtime doubly so," joked Douglas Adams in The Hitchhiker's Guide to the Galaxy. Scientists aren't laughing, though. Some speculative new physics theories suggest that time emerges from a more fundamental-and timeless-reality.

2 Try explaining that when you get to work late. The average U.S. city commuter loses 38 hours a year to traffic delays.

3 Wonder why you have to set your clock ahead in March? Daylight Saving Time began as a joke by Benjamin Franklin, who proposed waking people earlier on bright summer mornings so they might work more during the day and thus save candles. It was introduced in the U.K. in 1917 and then spread

4 Green days. The Department of Energy estimates that electricity demand drops by 0.5 percent during Daylight Saving Time, saving the equivalent of nearly 3 million barrels of oil.

5 By observing how quickly bank tellers made change, pedestrians walked, and postal clerks spoke, psychologists determined that the three fastest-paced U.S. cities are Boston, Buffalo, and New York.

6 The three slowest? Shreveport, Sacramento, and L.A.

7 One second used to be defined as 1/86,400 the length of a day. However, Earth's rotation isn't perfectly reliable. Tidal friction from the sun and moon slows our planet and increases the length of a day by 3 milli-seconds per century.

8 This means that in the time of the dinosaurs, the day was just 23 hours long.

9 Weather also changes the day. During El Ni?o events, strong winds can slow Earth's rotation by a fraction of a milli-second every 24 hours.

10 Modern technology can do better. In 1972 a network of atomic clocks in more than 50 countries was made the final authority on time, so accurate that it takes 31.7 million years to lose about one second.

11 To keep this time in sync with Earth's slowing rotation, a "leap second" must be added every few years, most recently this past New Year's Eve.

12 The world's most accurate clock, at the National Institute of Standards and Technology in Colorado, measures vibrations of a single atom of mercury. In a billion years it will not lose one second.

13 Until the 1800s, every village lived in its own little time zone, with clocks synchronized to the local solar noon.

14 This caused havoc with the advent of trains and timetables. For a while watches were made that could tell both local time and "railway time."

15 On November 18, 1883, American railway companies forced the national adoption of standardized time zones.

16 Thinking about how railway time required clocks in different places to be synchronized may have inspired Einstein to develop his theory of relativity, which unifies space and time.

17 Einstein showed that gravity makes time run more slowly. Thus airplane passengers, flying where Earth's pull is weaker, age a few extra nano-seconds each flight.

18 According to quantum theory, the shortest moment of time that can exist is known as Planck time, or 0.0000000000000000000000000000000000000000001 second.

19 Time has not been around forever. Most scientists believe it was created along with the rest of the universe in the Big Bang, 13.7 billion years ago.

20 There may be an end of time. Three Spanish scientists posit that the observed acceleration of the expanding cosmos is an illusion caused by the slowing of time. According to their math, time may eventually stop, at which point everything will come to a standstill.

1、时间是什么？--英国着名科幻小说家道格拉斯·亚当斯在他的小说《银河系漫游指南》中开玩笑地说："时间就是一种幻觉，午餐时间就更不用说了。"可是，科学家却笑不出来。最新的一些物理学理论猜想认为，时间起源于某种更根本、同时也就不存在时间的一种实体。

2、上班迟到的时候，怎么给自己找借口？--美国人平均每年因交通问题而延误的时间大约为38小时。

3、为什么每年都要从三月份开始实行夏时制？--300年前，美国天才政治家、科学家本杰明·富兰克林（Benjamin Franklin）的一个玩笑开大了：他说，夏日时期，天一早就大亮了，应该早点儿把人们叫醒，让他们早点出去干活，这样不但可多干活，还能节约几根蜡烛。没想到英国人从1917年开始就把他的玩笑变成现实，并在全世界迅速推广开来。

4、为什么实行夏时制的日子被称为"绿色日子"?--美国能源部统计，实行夏时制期间，美国能源需求量下降0.5%,相当于节省了300万桶石油。

5、美国哪三座城市人们的动作最快？--心理学家通过观察银行出纳员找零钱的动作、行人的步伐速度和邮电行业工作人员的说话速度，判定人们动作最快的三座城市是：波斯顿、水牛城和纽约。

6、那动作最慢的又是哪些城市？--什里夫波特（美国路易斯安那州西北部城市）、萨克拉门托（加州首府）和洛杉矶。

7、一天的86400分之一就是一秒吗？--不一定！因为地球的自转并不是你想象的那么靠谱。由于太阳和月亮的牵引会产生潮汐现象，而潮汐会产生一定的摩擦力，使地球的自转速度逐渐降低，大约每过一百年，一天时间就会慢3毫秒。

8、恐龙时代一天有几个小时？--根据上述算法，那个年代，一天只有23个小时。

9、天气现象会影响时间吗？--天气也会对时间造成一定影响。在厄尔尼诺现象期间，暴风会使地球的自转速度慢下来，大约是每24小时减慢一个毫秒的几分之一。

10、原子钟的准确程度有多高？--现代技术取得了长足进展。1972年，全世界共有50多个国家共建起一个原子计时网络，该网络就成为全世界最大的时间权威，其准确度达到每3170万年相差一秒左右。

11、什么是闰秒？--为了使时间与地球自转速度的减慢相一致，每隔几年就要给某一天的时间延长1秒钟，这就是闰秒。最近一次调整是去年除夕（即2008年12月31日24:00）,那一天要比平时多出一秒钟。

12、世界上什么东西的时间最精确？--美国设在科罗拉多州的国家标准与技术研究所，用世界上最准确的时钟测算出单个汞原子的震动频率最为精确，每十亿年才差别一秒钟，因此汞原子的震动时间最准确。

13、美国什么时候才开始划分时区？--应该是在19世纪初的时候。因为此前美国的每个村落都是以当地日当正午的时候来确定时间的，所以那时候一个村子就有自己的一个微小时区，而不是现在的全国几个时区。

14、在还没有划分时区的时候，美国铁路运输有什么问题？--那时候简直乱套了，火车进出站时间乱套了，时刻表简直成了摆设，后来只好沿途设立时间告示牌，以区分出发地时间、目的地时间和"铁路时间"的不同。

15、1883年11月18日，美国各大铁路公司成功迫使政府采用时区制。

16、也许正是由于人们总在思考怎样用一个统一时间把不同地方的时间同步化的问题，才激发了爱因斯坦的灵感，产生了相对论，彻底统一了时空问题。

17、爱因斯坦通过计算，表明引力的存在会使时间过得慢一些，因此，乘坐飞机的旅客，由于在空中的地心引力要弱一些，结果每一次飞行，旅客就年轻几个微秒（原文说老了几个微妙，应该是作者自己没有倒过来的缘故--译者注）.

18、根据量子理论，能够存在的最小时间单位叫做普朗克时间，长度为0.0000000000000000000000000000000000000000001秒（一千亿亿亿亿亿分之一秒）.

19、时间并非一直都存在。大多数科学家相信时间就是诞生宇宙的大爆炸那一刻才开始有的，即137亿年前才有时间的存在。

20、时间也还有可能结束。西班牙有三名科学家提出假说认为，现在人们所观察到的宇宙膨胀现象，实质上是因为时间变慢而产生的假象。按照他们提供的数学模型计算，时间终归是会停止的，在那一时刻，一切就都停止了（同时宇宙也将不复存在，一切幻化为零--译者注。）