1.11地球是一块磁铁
Section outline
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Lesson Objectives
::经验教训目标- Describe Earth as a magnet.
::将地球描述为磁铁
- State how Earth’s magnetism benefits living things.
::说明地球磁力是如何使生物受益的。
Lesson Vocabulary
::词汇表课程- magnetosphere
::磁层
- magnetic field
::磁磁场
- magnet
::磁磁磁
- magnetic poles
::电磁极
- compass
::指南针
Introduction
::导言Did you ever use a compass? Maybe you were out hiking? Maybe you have seen one on a car's dashboard. Did it look like the one in Figure ? Did you notice how it always moves? It moves as you go around corners. Do you know why? It spins around because it must always point north. It moves because the Earth is a giant magnet. In this lesson, you’ll learn why. You will also learn how Earth’s magnetism helps all living things.
::你曾经使用过指南针吗?也许你出去远足了?也许你在汽车的仪表板上看到过一个。它看起来像图中的那个吗?你有没有注意到它总是在移动?它随着你环绕的角落移动?知道为什么吗?它旋转,因为它总是向北移动。它移动是因为地球是一个巨大的磁铁。在这个教训中,你会知道为什么。你也会知道地球的磁铁如何帮助所有生物。A compass pointer is aligned by Earth’s magnetism to point north. Magnet Earth
::磁石地球Think about a huge bar magnet. Now imagine it running through the Earth. One end enters the south pole. The other end sticks out the north pole of the earth. You can see an example in Figure . This is a good model for Earth as a magnet. Like a bar magnet, Earth has north and south poles. Like all magnets it also has a magnetic field.
::想象一下一个巨大的铁块磁铁。 现在想象一下它穿过地球。 一端进入南极。 另一端刺入南极。 另一端刺出地球的北极。 您可以在图中看到一例。 这是地球磁铁的好模型。 像铁块磁铁一样, 地球有北面和南面。 就像所有磁铁一样, 它也有磁场 。Earth is like a giant bar magnet. Earth’s Magnetic Poles
::地球的磁极It is true that a compass needle always points north. That does not mean it points exactly north. Earth's geographic north pole is not the same as its magnetic north pole. Those two locations are fairly close. That does not mean they are the same place. Earth’s magnetic south pole is also not the same as its geographic south pole.
::诚然,针针针总是指向北。 这并不意味着针针指向北。 地球的北极与磁性北极不同。 这两个地点相距相当近。 这并不意味着它们就是同一地点。 地球的南极磁性也不同于其南极。Earth’s magnetic north pole is close to the geographic north pole. A compass pointer has north and south poles. A magnet's north pole points to Earth’s magnetic north pole. How can this happen. Aren't like poles supposed to repel? Shouldn't the north pole of the compass be pointing to the south pole of the Earth? The answer may surprise you. Earth’s magnetic north pole is actually the south pole of magnet Earth! It’s called the magnetic north pole to avoid confusion. Because it's close to the geographic north pole, it would be confusing to call it the magnetic south pole.
::指南针指针指向北纬和南纬两极。磁铁的北极点指向地球磁极的北极。这怎么可能发生呢?它不像北极应该击退的一样吗?指南针的北极点指向地球的南极吗?答案可能令你吃惊。地球磁极实际上是磁铁地球的南极。它被称为磁北极以避免混乱。由于它接近于地理北极,因此称它为磁南极将令人困惑。Earth’s Magnetic Field
::地球磁场Like all magnets, Earth has a magnetic field. Earth’s magnetic field is called the magnetosphere . It is a huge region that extends outward into space. It stretches from the surface to several thousand kilometers into the sky. It is strongest at the poles. You can see the extent of the magnetosphere in Figure .
::与所有磁铁一样,地球有磁场。地球磁场被称为磁层。地球磁场是一个向外延伸至空间的巨大区域。它从表面延伸至天空数千公里,在极地最强。您可以看到图中磁层的范围。The magnetosphere extends outward from Earth in all directions. Why Is Earth a Magnet? (Advanced Topic)
::为什么地球是磁网?The idea that Earth is a magnet is far from new. It was first proposed in 1600 by a British physician named William Gilbert. Knowing it acts like a magnet is one thing. Knowing why it acts like a magnet is more difficult. In fact, finding out why is a fairly recent discovery. To find out why required new technology. It was the seismograph that made it possible to learn why the Earth acted like a magnet. Seismograph are used to study earthquakes. By studying earthquake waves they were able to learn about Earth's interior (see Figure ). They discovered that Earth has an inner and outer core. The outer core consists of liquid metals, mainly iron and nickel. Scientists think that Earth’s magnetic field is generated here. It is caused by the motion of this liquid metal. The liquid metal moves as Earth spins on its axis.
::地球是一个磁体的想法远非新事物。 它最初由英国医生威廉·吉尔伯特于1600年提出。 了解它就像磁体一样是一回事。 了解它为什么像磁体是一回事。 了解它为什么像磁体是一件比较困难的事情。 事实上, 找出它为什么是一个相当近期的发现。 找出为什么需要新技术。 正是地震学使人们能够了解地球为什么像磁体一样。 地震学被用来研究地震。 通过研究地震波,他们能够了解地球的内部(见图 ) 。 他们发现地球有内外核。 外核由液态金属组成, 主要是铁和镍组成。 科学家们认为地球的磁场是在这里产生的。 它是由这种液态金属的运动造成的。 液态金属作为地球的轴心而移动。Charged particles flow through Earth’s liquid outer core, making Earth a giant magnet. Benefits of Earth’s Magnetic Field
::地球磁场的惠益Earth’s magnetic field helps protect Earth and its organisms. It protects us from harmful particles given off by the sun. Most of the particles are attracted to the north and south magnetic poles. This is where Earth’s magnetic field is strongest. This is also where relatively few organisms live.
::地球磁场有助于保护地球及其有机体。它保护我们免受太阳释放的有害微粒的伤害。 大部分微粒都吸引到北面和南面磁极。 这就是地球磁场最强的地方。 这也是生物数量相对较少的地方。Another benefit of Earth’s magnetic field is its use for navigation. People use compasses to detect Earth’s magnetic north pole. Knowing this helps them tell direction. Many animals have natural "compasses" that work just as well. Birds like the garden warbler in Figure use Earth’s magnetic field. They use it to guide their annual migrations. Recent research suggests that warblers and other migrating birds have structures in their eyes. These structures let them see Earth’s magnetic field as a visual pattern.
::地球磁场的另一个好处是用于导航。人们使用罗盘探测地球磁极的北极。知道这一点有助于他们辨别方向。许多动物都有自然的“复合”功能。像图中的园丁那样的鸟类使用地球磁场,他们用它来指导他们每年的迁移。最近的研究表明,沃布斯和其他迁徙的鸟类在他们眼中都有结构。这些结构让他们把地球磁场看成一种视觉模式。The garden warbler flies from Europe to central Africa in the fall and returns to Europe in the spring. Its internal "compass" helps it find the way. Lesson Summary
::经验教训摘要- Earth is a giant magnet. It has a north and south magnetic pole. It also has a magnetic field called the magnetosphere. Evidence in rocks shows that Earth’s magnetic poles have switched positions. They have done so hundreds of times in the past. Scientists think that Earth’s magnetic field is caused by the movement of charged particles within the outer core.
::地球是一个巨大的磁铁。 它有一个北面和南面磁极。 它还有一个磁场,叫做磁层。 岩石中的证据表明,地球磁极的位置已经改变。 过去,它们已经改变了数百次。 科学家们认为,地球磁场是由外核内带电粒的移动造成的。
- Earth’s magnetic field helps protect Earth’s surface. It also helps to protect organisms from harmful solar particles. Earth’s magnetic field is also used for navigation by humans and many other animals.
::地球磁场有助于保护地球表面,也有助于保护生物免受有害太阳粒子的伤害。 地球磁场也用于人类和许多其他动物的航行。
Lesson Review Questions
::经验回顾问题Recall
::回顾- What is the magnetosphere?
::什么是磁层?
- Identify evidence for magnetic reversals in Earth’s past.
::找出地球过去磁力逆转的证据。
- List two benefits to organisms of Earth’s magnetic field.
::列出对地球磁场生物的好处。
Apply Concepts
::应用概念- Use a bar magnet, a globe or large ball, and any other props you need to demonstrate to another student how Earth is like a bar magnet.
::使用铁棒磁铁,球球或大球 还有任何其他道具,你需要 向另一个学生展示地球是如何 像铁棒磁铁。
Think Critically
::仔细仔细思考- What is the relationship between Earth’s magnetic poles and Earth’s geographic poles?
::地球磁极与地球地理极之间的关系是什么?
- Explain why Earth is a magnet.
::解释为什么地球是磁铁
Points to Consider
::需要考虑的要点In this chapter, you learned that Earth is a magnet because of moving charged particles in its outer core. In the chapter "Electricity," you learned that moving charged particles create electric current. The next chapter explains how electric current and magnetism are related.
::在本章中, 你了解到地球是磁铁, 因为它在外核中移动了带电粒子。 在“ 电能” 一章中, 你学会了移动带电粒子会产生电流。 下一章解释电流和磁力之间的关系。- Based on what you now know about electricity and magnetism, can you predict how they are related?
::根据你现在对电力和磁铁学的了解 你能预测它们是如何关联的吗?
- Do you think electric current could be used to create a magnet? How might this be done?
::您认为电流可以用来制造磁铁吗? 如何做到这一点 ?
- Describe Earth as a magnet.
