the solar system
1. earth is one of nine planets which revolve around the sun. this family of planets, with their moons, is known as the solar system. since we live on earth, we think it is the most important planet. but the other planets are also interesting. some are smaller than earth, some larger; some are hotter, some colder. each one is different from all others and has something special about it.
2. no one knows for certain how the solar system began. we do know a lot about the planets, however, from the science of astronomy. astronomers have studied the planets and other objects in space for thousands of years. astronomy is a very complicated science. we look at the other planets to study, them, but the planet we are on is moving all the time. computers have helped us in the past twenty or thirty years. the satellites we send into space to measure and take pictures also tell a lot about the planets and help us to understand them.
3. mercury is the closest planet to the sun. it is also the smallest and fastest planet. the speed of the planet gave it its name: mercury was the rapid messenger of the roman gods. mercury completes its orbit around the sun in only 88 days, while earth's orbit takes 365 1/4 days. a day on mercury, however, is much longer than a day on earth. earth rotates on its axis once every 24 hours. mercury rotates on its axis once every 59 days.
4. astronomers don't know why mercury rotates so slowly, but they do know that this slowness means there is lot of heat and cold. the side of mercury which faces the sun is 350 degrees celsius. the side which is away from the sun is dark and cold. at 170 degrees below zero celsius, it is probably the coldest place in the solar system.
5. venus is the second planet in distance from the sun. it is about the same size as earth, and it comes closer to earth than any other planet. next to the sun and the moon, venus is the easiest object in the sky to see. people of ancient times loved its brightness and beauty so much that they named it after the roman goddess of love and beauty.
6. venus revolves around the sun once every 225 days and rotates on its axis once every 244 days. information from telescopes and satellites tells us that the planet is very hot. the temperature is usually between 300 and 675 degrees celsius. we can observe both venus and mercury either in the evening or early in the morning just before the sun rises.
7. mars is called the red planet because it has a definite red-orange color. it is the fourth farthest planet from the sun. a day on mars is only-about 40 minutes longer than a day on earth, but a year lasts 687 days. the planet was named after the roman god of war.
8. for many years, people believed that there was life on mars, but we now know that there probably isn't. the mariner space program sent many satellites to mars. we have excellent photos and information on this neighbor planet, and nothing suggests that there is any life there.
9. the fifth planet from the sun is also the largest of all the planets, jupiter. jupiter revolves around the sun once every 12 years, yet its day is amazingly short. its rotation, or its day, is only about 10 hours long. this is the fastest rotation - the shortest day - of any of the planets.
10. the planet's name is appropriate, since jupiter was the supreme roman god - the king of all the other gods. if you can imagine jupiter as a hollow ball, all of the other planets would fit inside and there would still be a lot of room left. jupiter has fourteen moons, the largest number of any planet.
11. after jupiter, the next farthest planet from the sun is saturn. it is almost 100 times larger than earth and is the farthest planet that we can see without the help of a telescope. saturn has a 29 1/2 year revolution time around the sun, but its day is about as long as jupiter's. the most interesting features about saturn are its rings. there are three large rings around the planet which are made up of billions of pieces of ice, rock, and metal, all in beautiful colors.
12. saturn was named for the roman god of time, probalb1y because it moves so slowly. the planet has ten known moons. the largest moon, titan, is larger than earth. it is the only moon of any planet which has its own atmosphere.
13. the seventh planet, uranus, was discovered in 1781 and was named for the greek god of the sky. it is twice as far from the sun as saturn, so it was difficult for early astronomers to find it. a year on uranus lasts 84 of our years, but the planet's day is about as long as saturn's or jupiter's.
14. uranus is unusual because it is tilted. on earth, it is always cold at the north and south poles and it is always hot at the equator, but this is not true on uranus. the tilt of the planet means that each pole has 42 year summer, followed by a 42 year winter.
15. in 1977, an airplane went high above the atmosphere of earth and carried a telescope to look at uranus more clearly. by this method, astronomers discovered that uranus has five rings which are similar to saturn's. the planet also has five moons.
16. neptune, the eighth planet, was "discovered" in 1843 before it was seen. no one actually saw the planet in a telescope until 1846. its discovery by use of mathematics was a remark/tble achievement. astronomers knew that planets change the motion of other nearby objects. after uranus was discovered, many people realized that there must be another planet which was affecting the way it moved.
17. neptune is very cold-about 220 degrees below zero celsius. it takes the planet 165 years to revolve around the sun. it spins on its axis once every 16 hours. neptune has two moons. the larger moon, triton, is only a little larger than earth's moon. neptune was named for the roman god of the sea, and it is even the same color as the sea. the planet looks blue-green in a telescope because of its gases.
18. the last discovery of a planet was made in 1930. pluto was named for the roman god for the dead and ruler of hell. in 1955, two astronorr/ers figured out that pluto had a "day" of almost a week and a "year" of 248 earth years.
19. pluto's orbit around the sun is unusual. pluto is the farthest planet from the sun, but it sometimes comes closer to the sun than other planets, and occasionally it is even closer than neptune. no one knows for sure, but it is probably about 140 degrees below zero celsius on this ninth planet.
20. in roman mythology, the god of fire and metal working is called vulcan. some astronomers believe that there is a tenth planet, and they have named it vulcan. there is some evidence that another planet is somewhere in space, but that it is hidden by the other planets. the famous scientist all~ert einstein did not believe that there was another planet, so most astronomers don't look for vulcan, but no one knows for certain that it isn't out there.
21. there may not be a vulcan, but it is probable that there are many other solar systems in the universe. the sun is a star, and we know that there are billions of other stars. many of them are probably similar to our sun. it is easy to suppose that many of these suns have planets just like the nine which are in our solar system.
参考译文：太阳系
1．地球是围绕太阳旋转的九个行星之一。这个行星家庭以及它们的卫星， 就是我们所知道的太阳系。因为我们在地球上生活，我们就认为它是最重要 的行星。但是其他行星同样令人感兴趣。一些比地球小，一些比较大，一些比 较热，一些比较寒冷。每一个都不同于所有其它行星，各有特色。
2．没有人能确切知道太阳系是如何形成的。然而，我们从天文学中知道 了很多关于行星的事。天文学家已经研究行星和太空中的其它天体数千年了。 天文学是一个非常复杂的学科。我们看着其它行星研究它们，我们所在的行 星也始终在移动。在过去二三十年里，计算机帮助了我们。我们送到太空中 的人造卫星的测量和拍摄的照片，也告诉了我们许多有关行星的事，并且帮 助我们认识它们。
3．水星是最靠近太阳的行星。它也是最小的和最快的行星。行星的速度 确定了它的名字： mercury。墨丘利(mercury)神是罗马神中的快速 的信使。水星在仅仅88天里完成它围绕太阳的轨道，然而地球沿轨道飞行需 要花费三百六十五又四分之一天。在水星上的一天，比地球上的一天长的多。 每24小时地球围绕它的轴自转一周。水星围绕它的轴自转一周要59天。
4．天文学家不知道水星自传为什么如此之慢，但是他们知道这种缓慢意 味着有大量的炙热和寒冷。水星面对太阳的一面达摄氏350度。背离太阳的 一面黑暗而寒冷，达到摄氏零下170度，它可能是太阳系中最寒冷的地方。
5．venus(金星)是距离太阳第二远的行星。它大约和地球的大小相同， 而且它比其它任何行星离地球更近。紧邻太阳和月亮，金星是天空中最容易 被看见的天体。远古时代的人们如此喜爱它的明亮和美丽，因此他们以罗马 爱和美的女神维纳斯(venus)为它命名。
6．金星每225天围绕太阳旋转一周，而每244天围绕它的轴自转一周。 来自望远镜和人造卫星的数据告诉我们，它是个非常热的行星。温度通常在 摄氏300度到675度之间。我们能在傍晚或早晨太阳升起之前同时观察到金 星和水星。
7．mars(火星)被称作红色星球是因为它确实有一种清楚的桔红色。它 是离太阳第四远的行星。火星上的一天只不过比地球上的一天长大约40分钟， 但是—一年却要持续687天。这颗行星被以罗马战神玛斯命名。
8．许多年以来，人们相信在火星上有生命，但是我们现在知道或许没有。 mariner(水手)太空计划向火星发送了许多人造卫星。我们有关于这颗邻 居行星的极好的照片和数据资料，其中没有什么显示出火星存在任何生命。
9．jupiter(木星)是离太阳第五远也是所有行星中最大的一颗星。木星 每12年围绕太阳旋转一周，然而它的一天却出奇的短。它的自转，或它的 一天只有大约10个小时。这是任何行星中速度最快的自转，最短的一天。
10．这颗行星的名字是恰当的，因为朱庇特(jupiter)是至高的罗马神， 所有的其它神的王。你是否能想象木星如同一个空的球，那么把所有的其它 行星都放到里面，它仍然还剩有许多空间。木星拥有十四个卫星，是所有行 星中卫星最多的一个。
11．在木星之后，下一个距离太阳最远的行星是saturn(土星)。它几 乎比地球大一百倍，是我们不借助望远镜所能看到的最远的行星。土星围绕 太阳旋转一周的时间是二十九又二分之一年，但是它的千天大约像木星一天 那么长。土星最令人感兴趣的特征是它的环。有三个环围绕着土星，它们由 亿万片冰物质、岩石、和金属物质构成，它们都有美丽的颜色。
12．saturn(土星)以罗马的时间之神命名，可能是由于它移动如此之 慢。这个行星有十个为人所知的卫星。最大的卫星，titan，比地球还大。 titan是所有行星的卫星中唯一有自己的大气层的卫星。
13．第七颗行星是uranus(天王星)，发现于1781年，以希腊天空之 神命名。它离太阳的距离是土星的两倍，因此对于早期的天文学家来说找到 它很困难。天王星上的一年相当于我们地球的八十四年，但是这个行星的一 天大约与土星或木星的一天相当。
14．uranus(天王星)非常特殊，因为它是倾斜的。在地球上，北极和 南极总是最冷，赤道总是最热，但是在天王星上这个规律不正确。这颗行星 的倾斜意味着它的每个极有42年的夏天，随后是42年的冬天。
15．在1977年，一架携带了天文望远镜的飞机飞出地球大气层以便更清 楚地观察天王星。通过这个方法，天文学家发现天王星有五个类似于土星的 光环。这颗行星也有五个卫星。
16．neptune(海王星)是第八颗行星，1843年，它被“发现”于看到 它之前。1846年以前没有人在天文望远镜中真正看见这颗行星。发现它凭借 的是数学，其本身就是一项非凡的成就。天文学家早就知道行星能改变它附 近其它天体的运动。在天王星被发现之后，许多人认识到一定存在另一个行 星影响着它移动的轨迹。
17．neptune(海王星)是一颗非常冷的星，大约在摄氏零下220度。 它绕太阳一周要用165年。它围绕它的轴旋转一圈要16小时。海王星有两个 卫星。大一点的卫星叫triton，仅仅略大于地球的卫星。neptune(海王 星)取名于罗马的海洋之神，而且它的颜色也如同大海。这颗有自己的大气 层，所以在天文望远镜里看上去呈蓝绿色的。
18．最后一颗行星的发现在1930年。pluto(冥王星)被以象征死亡和 地狱统治者的罗马神命名。在1955年，两个天文学家计算出冥王星的“一天” 几乎是地球上的一个周，而它的“一年”则是248个地球年。
19．pluto(冥王星)围绕太阳运转的轨道是非同寻常。冥王星是离太阳 最远的行星，但是它有时比其他行星还要靠近太阳，偶尔它甚至比海王星更 靠近太阳。没有人确切知道，但估计这第九个行星上的温度大约是摄氏零下 140度。
20．在罗马人的神话中，司火与锻冶之神被称为vulcan。一些天文学 家相信有第十颗行星，而且他们已经命名它为vulcan。有些证据表明在太 空的某个地方有另外的一颗行星，但是它被其它行星所隐藏。著名科学家艾 伯特·爱因斯坦不相信存在另外一颗行星。因此，大多数天文学家不再寻找 vulcan。但是没有人能确定它确实不在那里。
21．可能没有vulcan，但是，在宇宙中可能有许多其它的太阳系。太 阳是一颗恒星，而我们知道有数以亿计的其它的恒星。它们中的许多可能与 我们的太阳类似。很容易推想大部份这样太阳系应该有行星，恰恰如同我们 的太阳系拥有的九大行星一样。