Section outline

  • General

    Collapse all Expand all

  • 地球在太空中的运动

    Lesson Objectives
    ::经验教训目标

    • Describe the motion that provides the Earth with its day and night cycle.
      ::描述为地球提供昼夜循环的动作
    • Describe the motion of the Earth that provides it with its seasons. (Advanced Topic) 
      ::描述为地球提供季节的地球运动。 (高级专题)
    • Understand the Earth orbits around  the Sun and explains its yearlong cycle. 
      ::了解围绕太阳的地球轨道,解释其长达一年的周期。

    Lesson Vocabulary
    ::词汇表课程

    • revolution
      ::革命革命革命 革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命革命
    • rotation
      ::旋转

    The Rotating Earth
    ::旋转地球

    So how do we know that the Earth rotates on its axis? Before this century, all evidence collected about Earth's motion came from Earth-bound observations. From Earth-bound observation it is easy to see why, historically, the Earth was stationary. It was the Sun and the stars that orbited the Earth. One simple experiment can be used to show that is not the case. It is the Earth that is rotating causing the cycles we see in the sky.   
    ::我们怎么知道地球在其轴心上旋转?本世纪之前,所有关于地球运动的证据都来自地球对地观测。从地球对地观测中可以很容易地看出,为什么历史上地球是静止的。是太阳和恒星环绕地球。一个简单的实验可以用来证明事实并非如此。地球是旋转导致我们在天空中看到的周期的。

    The experiment was designed by Léon Foucault, a French scientist, in the year 1851. He hung a heavy iron weight from a long wire. He pulled the weight to one side and then released it. The weight swung back and forth in a straight line. If Earth did not rotate, the pendulum would never change direction as it moved back and forth. But it did not continue to swing in the same direction. It was thought to change because the Earth was rotating beneath it.  Figure    shows how this might look.
    ::实验是法国科学家Léon Foucault在1851年设计的。他用长线吊着重铁重量。他把重力拉到一边,然后释放出来。重力在一条直线上回转。如果地球不旋转,则钟摆不会随着它的回转而改变方向。但是它并没有继续沿着同一方向摇摆。人们认为它会改变,因为地球在它下面旋转。图显示它可能看起来如何。

    lesson content
     
    Imagine a pendulum at the North Pole. The pendulum always swings in the same direction. But because of Earth’s rotation, its direction appears to change to observers on Earth.

    A Turn of the Earth
    ::地球的转变

    In this video, MIT students demonstrate how a Foucault Pendulum is used to prove that the Earth is rotating.
    ::在影片中,麻省理工学院的学生展示了Foucault Pentulum是如何用来证明地球在旋转的。

     

     

    Earth’s Rotation
    ::地球的旋转

    Imagine a line passing through the center of Earth. The line extends through both the North Pole and the South Pole. This imaginary line is called an  axis.  Earth spins around its axis, just as a top spins around its spindle. This movement is called Earth’s  rotation.
    ::想象一下穿过地球中心的一条线。 这条线横穿北极和南极。 这一条假想的线被称为轴。 地球绕着轴旋转, 就像环绕轴的顶部旋转一样。 这个运动被称为地球的旋转。

    At the Equator, the Earth rotates at a   of about 1,700 km per hour. In contrast, at the poles the movement speed is nearly nothing. You can model this motion out on the playground. What if you lined up all the students in a row? One end will represent the center point, or axis. The axis would also represent one of Earth's poles. The other end of the line represents the Earth's equator. Imagine the line moving in a circle around the axis. Make sure you keep the line straight through this exercise. The person standing at the axis turns slowly. The person on the outside of the circle will need to walk much faster. 
    ::赤道时, 地球每小时旋转约 1 700 公里。 相反, 在极处, 运动速度几乎是空的。 您可以在操场上模拟这个运动。 如果您将所有学生排成一行, 如何? 一边代表中点或轴。 轴也将代表地球的极之一 。 另一边代表地球的赤道 。 想象这条线在轴周围的圆形中移动的线 。 想象一下这条线在轴上移动 。 请确保您保持直线通过此项练习。 站在轴上的人会慢慢转动。 圆外的人需要更快的行走 。

    Day-Night Cycle
    ::日夜周期

    Earth rotates once on its axis about every 24 hours. To an observer looking down at the North Pole, Earth appears to rotate counterclockwise. From nearly all points on Earth, the   appears to move across the sky from east to west.
    ::地球大约每24小时在其轴上旋转一次。 观察北极的观察者认为, 地球似乎逆时旋转。 从地球上几乎所有的点看, 地球似乎从东向西移动。

    Of course, the Sun is not moving from east to west at all. The Earth is actually rotating on its axis. The Moon and stars also seem to rise in the east and set in the west. We often say that the Sun is “rising” or “setting.” Actually, it is the Earth’s rotation that makes it appear that way. The Moon and the stars at night also seem to rise in the east and set in the west. Earth’s rotation is also responsible for this too. As Earth turns, the Moon and stars change position in the sky. All the motion in the sky that you notice is due to the Earth’s rotation.
    ::当然,太阳并没有从东向西向西移动。地球实际上在轴上旋转。月球和恒星似乎也在东向东升起,在西向。我们经常说太阳是“崛起 ” 或“建立 ” 。 事实上,正是地球的旋转才使太阳看起来如此。 夜晚的月球和恒星似乎也在东向西升起,并设置在西面。地球的旋转也是造成这种情况的原因。随着地球的旋转,月球和恒星在天空的位置也发生变化。你注意到的天空中的所有运动都是地球的旋转造成的。

    Earth’s rotation explains the cycle of daylight and darkness. The cycle occurs every 24 hours, the length of an Earth day. Different places experience sunset and sunrise at different times. The amount of daylight and darkness also differs by location.
    ::地球的旋转可以解释日光和黑暗的循环。 周期每24小时发生一次,即地球日的长度。 不同的地方在不同的时间经历日落和日出。 日光和黑暗的数量也因地点而异。

    The daylight and darkness cycles are determined based on how far north or south they are. At the equator, there is an even amount of daylight and darkness. No matter what day of the year it is, the equator always experiences 12 hours of daylight every 24 hours. At the poles, the amount of daylight varies greatly. In their summer months. The poles receive 24 hours of continuous daylight for 6 months. During their winter months they have 24 hours of darkness. This too lasts for 6 months.
    ::日光和黑暗的循环取决于它们所处的北面或南面的距离。在赤道地区,日光和黑暗的程度是相等的。不管是哪一天,赤道地区总是每24小时12小时的日光。在北极地区,日光的量差别很大。在夏季月份,北极地区连续每天24小时的日光,持续6个月。在冬季月份,北极地区有24小时的夜光。这同样持续了6个月。

     

     

    Earth’s Seasons (Advanced Topic)
    ::地球季节(高级专题)

    lesson content
     
    The Earth tilts on its axis.

    The Earth is tilted  23 1/2∘  on its axis. ( Figure  ) This means that as the Earth rotates, one hemisphere has longer days with shorter nights. At the same time the other hemisphere has shorter days and longer nights. For example, in the Northern hemisphere summer begins on June 21. On this date, the North Pole is pointed directly toward the Sun. This is the longest day and shortest night of the year in the Northern Hemisphere. The South Pole is pointed away from the Sun. This means that the Southern Hemisphere experiences its longest night and shortest day ( Figure  ).
    ::地球在其轴轴上倾斜 23 1/2 。 (图 ) 这意味着随着地球旋转,一个半球的日数较长,夜晚较短。 同时,另一个半球的日数较短,夜晚更长。 例如,北半球的夏季从6月21日开始,北极直接指向太阳。 这是北半球一年中最长、最短的一天。 南极远离太阳。 这意味着南半球的夜晚最长、最短的一天( 图 ) 。

    The hemisphere that is tilted away from the Sun is cooler because it receives fewer direct rays. As Earth orbits the Sun, the Northern Hemisphere goes from winter to spring, then summer and fall. The Southern Hemisphere does the opposite from summer to fall to winter to spring. When it is winter in the Northern hemisphere, it is summer in the Southern hemisphere, and vice versa. 
    ::远离太阳的半球更冷却,因为它接收的直接射线较少。随着地球在太阳轨道上运行,北半球从冬季到春季,然后是夏季,然后是秋季和秋季。南半球从夏季到秋季到冬季到春季,反之亦然。当北半球的冬天到南半球的夏天,南半球的夏天到南半球的夏天,反之亦然。

    What does this mean for you? If you live in North America, July 1 is usually a very warm day. If you traveled to Southern Australia, you would need a heavy coat. At the equator, the seasons never change. As a result, the average daily temperatures remain the same. There is no summer and winter as we know them. 
    ::这对你意味着什么?如果你住在北美,7月1日通常是非常温暖的一天。如果你前往南澳大利亚州,你需要一件大衣。在赤道地区,季节永远不会改变。因此,平均每天气温保持不变。我们所认识的夏季和冬季没有。

    lesson content
     
    Earth's tilt changes the length of the days and nights during different seasons.

    Earth’s Revolution
    ::地球革命

    Earth’s revolution around the Sun takes 365.24 days. That is equal to one year. Why does the Earth stay in orbit around the Sun? It is the Sun's gravity ( Figure   ) that holds the Earth in place. If not for gravity, the Earth would continue to go in a straight line. 
    ::围绕太阳的地球革命需要365.24天。 相当于一年的时间。 为什么地球留在围绕太阳的轨道上?是太阳的引力(图)支撑着地球。 如果不是因为引力,地球将继续沿着一条直线前进。

    Earth's orbit is not a circle. It is somewhat elliptical. So as we travel around the Sun, sometimes we are a little farther away from the Sun. Sometimes we are closer to the Sun.
    ::地球轨道不是一个圆圈。 它有点椭圆。 当我们环绕太阳旅行时, 有时我们距离太阳更远一点。 有时我们距离太阳更近。

    lesson content
     
    Earth and the other planets in the solar system make elliptical orbits around the Sun.

    It takes over eight minutes for light to get from the Sun to Earth. The   between the Earth and the Sun is about 93 million miles. That’s about 150 million kilometers. Earth revolves around the Sun at 27 kilometers per second. It is going really fast. Even at that speed it still takes a long time to go around the Sun. It takes 365.24 days to be exact.   and   are closer to the Sun. They take a shorter time to make one orbit. Mercury takes only about 88 Earth days to make one trip around the Sun. All of the other planets take longer. The exact amount depends on the planet's distance from the Sun.   takes more than 29 Earth years to make its journey around the Sun. How old would you be if you were on  ?
    ::从太阳到地球的光线需要超过8分钟。地球和太阳之间的光线大约为9 300万英里。大约1亿5千万公里。地球以每秒27公里的速度环绕太阳。它的速度非常快。即使以这种速度绕太阳需要很长的时间。精确地说,它也需要365.24天的时间。它离太阳更近。它们制造一个轨道需要较短的时间。汞只需要大约88个地球日就能够绕太阳旅行一次。所有其他行星需要更长的时间。确切的数量取决于地球与太阳的距离。它需要超过29年的时间来绕太阳旅行。如果你在太阳上,你将会有多老?

    Misconceptions about Elliptical Orbits and Seasons
    ::对椭圆轨道和季节的误解

    Some people often think the slightly oval shape of our orbit causes Earth's  . That's not true! The seasons are due to the tilt of Earth’s axis. The tilt of the Earth causes different amounts of energy to hit the earth depending on the Season. For the northern hemisphere, the Earth is tilted toward the Sun during the summer. This angle allows more energy to strike Earth’s surface. It also causes longer days. Longer days increase the amount of time we receive the Sun’s energy. Have you noticed that the days are longer in the summer months?
    ::有些人常常认为我们轨道的略微oval形状导致地球。这不是真的!季节是地球轴的倾斜造成的。地球的倾斜导致不同数量的能量依季节而撞击地球。对于北半球来说,夏季地球会向太阳倾斜。这个角度可以让更多的能量撞击地球表面。这还会造成更长的天数。更长的天数会增加我们得到太阳能量的时间。你有没有注意到夏天的天数会更长?

    Lesson Summary
    ::经验教训摘要

    • The planets in our solar system all spin as they revolve around the Sun in fixed paths called orbits.
      ::我们太阳系中的行星 以固定的轨道绕着太阳旋转
    • The balance between gravity and our motion around the Sun keep the planets in orbit at fixed distances from the Sun.
      ::引力和太阳周围运动之间的平衡 使行星在轨道上 与太阳保持固定距离
    • Earth has a magnetic field, created by motion within Earth's outer, liquid iron core. The magnetic field shields us from harmful radiation.
      ::地球有磁场,它是由地球外表的液态铁核心内运动产生的。磁场保护着我们免受有害辐射。
    • Earth rotates on its axis once each day and revolves around the Sun once every year.
      ::地球每天在其轴上旋转一次,每年围绕太阳旋转一次。
    • The tilt of Earth's axis produces seasons.
      ::地球轴的倾斜产生季节。

    Lesson Review Questions
    ::经验回顾问题

    Recall
    ::回顾

    1. What was the evidence that Earth was round before there were photos from space?
      ::在有太空照片之前 地球是圆的 证据是什么?
    1. What two substances does Earth have that allow it to support life?
      ::地球有两种物质 来维系生命?
    1. What does a compass have that allows you to tell direction?
      ::指南针有什么能让你指明方向的?
    1. Describe Earth’s rotation. Describe Earth's revolution.
      ::描述地球的旋转。描述地球的革命。
    1. How long does it take for Earth to make one revolution around the Sun?
      ::地球在太阳周围进行一场革命需要多久?
    1. Describe Earth’s orbit around the Sun. Describe the orbits of the other planets.
      ::描述地球围绕太阳的轨道,描述其他行星的轨道。

    Apply Concepts
    ::应用概念

    1. Earth's “spheres” all interact. Given what you know about Earth science, can you give some examples?
      ::地球的“范围”是相互作用的。根据你对地球科学的了解,你可以举几个例子吗?
    1. What would happen to Earth-Moon if Earth suddenly shrunk to half its current size?
      ::如果地球突然缩缩到目前大小的一半 地球月亮会怎么样?

    Think Critically
    ::仔细仔细思考

    1. Why do the planets that are furthest from the Sun take longer to make one orbit around the Sun? Explain your answer.
      ::为什么距离太阳最远的行星需要更长的时间才能绕太阳运行一个轨道?解释一下答案。
    1. Even though Earth is closest to the Sun in January, people in the Northern hemisphere experience winter weather. Why do you think people in the Northern Hemisphere have winter in January?
      ::尽管地球与1月份的太阳最接近,但北半球的人们却经历着冬天的天气。 你认为北半球的人们为什么在1月份会有冬天?