【正文】 uple of hundred years ago, very little have known about this force. Learning about the electromagnetic force and how to use it was a major step forward. It revolutionized munication, transportation and manufacturing. Imagine what life would be like without electricity. The electromagnetic force has two parts, the electrical force and magnetic force. The electrical force is the force between an electrical charge article such as electron and proton(質(zhì)子). 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 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 pass. Why does the earth have a magnetic field? Many scientists believe that the earth’s magnetic field is due to the earth rotation. Deep inside the earth is solid iron core surrounded by a liquid metal outer core. The moving electric currents inside this liquid metal create a magnetic field. The earth magnetic field is important because it protects us from the solar wind. The solar wind is a current of charge particles ing 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(輻射), which can be dangerous to life. It also protects the satellite that we use for munication. Scientists now believe that the earth’s magnetic field is about to reverse. This is called the magnetic field reversal. Every 200,000 to 300,000 years, the earth magnetic field reverses. In other words, the north and the south magnetic pole switch places. This has happened many times in earth’s history, but it has been happening more lately. Recent research provides evidence that there have been 5 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 magnetic field has weakened about 5% per decade. As its current rate, the next reversal could happen within the next century. Some people also worry about the effects of the magnetic field reverse. They think there is a possibility that it could cause many problems. For example, without magnetic field, munications can be disrupted. Birds and other forms of lives could bee confused and get lost. Another effect will the increase in some forms of cancer especially skin cancer. This will be because of the increase in the amount of radiation absorbed by our bodies. The possibility that a field reversal will be an extinction even is very low. There is very little historic evidence to show that previous reversals have caused extinctions. Humans have been on earth for million years, during which there have many reversals. Therefore, scientists believe any changes would be temporary. Another theory is that the earth outer layer could rotate around the outer liquid mental core that make out of the earth. So in the next reversal, continent could ship positions from north to south. Imagine the effect happened, Australia would be in the northern hemisphere. With so many theories, how can we know what to believe? This is important because some of them require us to act well in advance. Otherwise, it will be too late to prevent the catastrophe. This underlines the importance of getting reliable information backed by strong evidence. L5 Unit 34 vocabularyResume, to continue or start again after a pause. After a short interruption, our work resumed and we worked for another hour. Work on the project resumed once we passed the safety inspection(檢驗(yàn)。ve, overly simple or lacking experience. He wants to change the world, but he is very na239。ve. If you think that woman was good, then let’s give her a chance. Ok, I’ll give her a chance. And I respect. But I pletely disagree with your decision. I know and I thank you for your honest opinion. The fact that he wasn’t good looking might have made him stronger.She thinks his decision to hire the woman isn’t realistic and goes against experience.I’m attracted to the advertisement that get my attentionL5 Unit 33 Listening Living conditions around the world, vary from country to country. other countries have very large economies, but the majority of their citizens are poor. Some countries have smaller economies, but the majority of their citizens are not poor. So the size of a country economy isn’t the only factor that determines how wealthy the citizens are. The sides of its population is also an important factor. Another factor how a country’s wealth is distributed between the rich and the poor. Let’s look at some examples. This chart shows the world 5 largest economies in 2015. It ranks the countries by the gross domestic product, or GDP. The GDP is one way of measuring the size of an economy. It’s the total value of goods and services produced in a country thin a year. As you can see, according to this chart, the US and China had the largest economies. According the chart, India had the third largest economy in the world. Its economy was bigger than Japan’s. the average living conditions in Japan is much higher than in India. One reason for this is the difference in population. India has a much larger population, so its wealth is distributed among a larger number of people. You can find this information by checking a country per capita. Per capita means per person. If two countries have the same GDP but one country has half the number of people, its GDP per capita is twice large. Another important factor is how the wealth of a country is shared. In some countries, much of the wealth is concentrated in just a few people. For example, in the US, just 5% of the population had more than 70% of the wealth. This shows that many US citizens are not wealthy despite the size of their e