Level5-Unit3-Part4-Listening

There are several fundamental forces that hold our universe together. One of these ,of course, is gravity , the force between objects that have mass. Another important force is the electromagnetic force. The electromagnetic force is responsible for chemical reactions. Without it, there would be no atoms or molecules. Up until a couple of hundred years ago, very little was known about this force. Learning about the electromagnetic force and how to use it was a major step forward. It revolutionized communication, transportaion and manufacturing. Imagine what life would be like without electricity!

有些主要的力將我們?nèi)f物聚集在一起。當(dāng)然，其中一種力叫重力，這種力存在大量物體之間。另一個(gè)重要的力電磁力。電磁力在化學(xué)反應(yīng)中承擔(dān)責(zé)任。沒有電磁力，就沒有分子或者原子。直到幾百年前，對(duì)這種力量知之甚少。如今，學(xué)習(xí)并使用電磁力向前邁出了重要的一步，使通信、搬運(yùn)、制造業(yè)產(chǎn)生徹底變革。想象一下沒有電的生活是什么樣子。

The electromagnetic force has two parts, the electrial force and the magnetic force. The electric force is the force between electrically charged particals, such as electrons and protons. Electric charges attract or repel each other with a force that depends on the distance between them. The magnetic force is the force between magnetic poles, such as the north and south pole. In fact, the earth is like a large bar magnet, with a north and a south pole. Many animals use the Earth's magnetic field to navigate during their migrations. We can also see this magnetic field when we use a compass.

電磁力分為兩部分，分為電力和磁力。電力產(chǎn)生與帶電粒子之間，例如：電子和質(zhì)子。帶電粒子之間相互吸引或者排斥，取決于它們之間相隔的距離。磁力產(chǎn)生于磁極之間，比如：南極和北極。事實(shí)上，地球就是一個(gè)巨大的磁球，有一個(gè)南極和北極。很多動(dòng)物在遷移時(shí)利用地球的磁極來辨別方向。當(dāng)我們用羅盤時(shí)，我們也用到磁力。

Why does the Earth have a magnetic field? Many scientists believe that the Earth's magnetic field is duo to the Earth's rotation. Deep inside the Earth is a solid iron core, surrounded by a liquid metal outer core.The moving electric currents inside this liquid metal create a magnetic field.

為什么地球有磁場(chǎng)？許多科學(xué)家認(rèn)為地球的磁場(chǎng)與地球的自轉(zhuǎn)是雙重的。在地球的深處是一個(gè)固體鐵芯，周圍是一個(gè)液態(tài)金屬外核。這種液態(tài)金屬內(nèi)部的移動(dòng)電流會(huì)產(chǎn)生一個(gè)磁場(chǎng)。

The Earth's magnetic field is important because it protects us from the solar wind. The solar wind is a current of charged? particles coming at us from the Sun. When the solar wind nears the Earth, the Earth's magnetic field deflects it away. This protects the Earth from the radiation, which can be dangerous to life. It also protects the satellites that we use for communication.

地球磁場(chǎng)是重要的，因?yàn)樗Ｗo(hù)我們免受太陽風(fēng)的侵襲。太陽風(fēng)是來自太陽的帶電粒子的電流。當(dāng)太陽風(fēng)接近地球時(shí)，地球的磁場(chǎng)使它偏離。這就保護(hù)了地球免受輻射，這對(duì)生命是危險(xiǎn)的。它還保護(hù)我們使用的衛(wèi)星進(jìn)行通信。

Scientists now believe that the Earth's magnetic field is about to reverse. This is called magnetic field reversal . Every 200,000 to 300,000 years. the Earth's magnetic poles switch places. This has happened many times in Earth's history, but it has been happening more? lately.

科學(xué)家們現(xiàn)在相信地球的磁場(chǎng)即將逆轉(zhuǎn)。這叫做磁場(chǎng)反轉(zhuǎn)。每200000到300000年。地球的磁極轉(zhuǎn)換位置。這在地球的歷史上已經(jīng)發(fā)生過很多次，但最近這種情況一直在發(fā)生。

Recent research provides evidence that there been fi ve magnetic reversals during? the past 500,000 years. The most recent event happened approximately 41,000? years ago.? Recent studies have found that the Earth's magnetic field has weakened about 5% per decade. At its current rate, the next reversal could happen within the next century.

最近的研究提供了證據(jù)表明，在過去的500000年里發(fā)生了磁反轉(zhuǎn)現(xiàn)象。最新的事件發(fā)生在大約41000年前。最近的研究發(fā)現(xiàn)，地球磁場(chǎng)每十年減弱約5%。按照目前的速度，下一個(gè)逆轉(zhuǎn)可能發(fā)生在下個(gè)世紀(jì)。

Some people worry about the effects of a magnetic field reversal. They think there is a passibility that it could cause many problems. For example, without a magnetic field, communications could be disrupted. Birds and other forms of life could become confused and get lost. Another effect would be an increase in some forms of caner, especially skin cancer. This would be because of an increase in the amount of radiation absorbed by our bodies.

有些人擔(dān)心磁場(chǎng)反轉(zhuǎn)的影響。他們認(rèn)為這種現(xiàn)象有可能造成許多問題。例如，在沒有磁場(chǎng)的情況下，通信可能中斷。鳥類和其他形式的生命可能會(huì)變得困惑和迷茫。另一個(gè)影響是某些形式的癌癥，尤其是皮膚癌的增加。這是因?yàn)槲覀兩眢w吸收的輻射量增加了。

The possibility that a field reversal would be an extinction event is very low. There is very little historical evidence to show that previous reversal have caused extinctions. Humans have been on Earth for million of years, during which there have been many reversals. Therefore, scientists believe that any changes would be temporary. Another theory is that the Earth's outer layer could rotate around the liquid metal core that? makes up most of the earth.So in the next reversal, continents could shift positions, from north to south. Imagine, if that happened, Australia would be in the northern hemisphere!

場(chǎng)反轉(zhuǎn)將是滅絕事件的可能性非常低。很少有歷史證據(jù)表明先前的逆轉(zhuǎn)導(dǎo)致了滅絕。人類在地球上已經(jīng)存在了數(shù)百萬年，在此期間出現(xiàn)了許多逆轉(zhuǎn)。因此，科學(xué)家認(rèn)為任何改變都是暫時(shí)的。另一個(gè)理論是，地球的外層可以圍繞構(gòu)成地球大部分的液態(tài)金屬核心旋轉(zhuǎn)。因此，在下一個(gè)逆轉(zhuǎn)中，大陸可以從北向南移動(dòng)位置。想象一下，如果那樣的話，澳大利亞會(huì)在北半球！

With so many theories, how can we know what to believe? This is important because some events require us to act well in advance. Otherwise, it will be too late to prevent a catastrophe.This underline the importance of getting reliable imformation, backed by strong evidence.

有這么多理論，我們?cè)趺床拍苤涝撓嘈攀裁茨?？這是很重要的，因?yàn)橐恍┦录笪覀兲崆靶袆?dòng)。否則，阻止災(zāi)難的發(fā)生已經(jīng)為時(shí)已晚。這強(qiáng)調(diào)了獲得可靠信息的重要性，有強(qiáng)有力的證據(jù)支持。