Level5 Unit3 Part4 Listening

Electromagnetic Force

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, transportation and manufacturing. Imagine what life would be like without electricity!

The electromagnetic force has two parts, the electric force and the magnetic force. The electric force is the force between electrically charged particles 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.

Why does the Earth have a magnetic field? Many scientists believe that the Earth's magnetic field is due 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.

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.

Magnetic Field Reverseal

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 field reverses. In other words, the North and South magnetic poles 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 five 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.

Some people worry about the effects of a magnetic field reversal. They think there is a possibility 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 cancer, especially skin cancer. This would be because of an increase in the amount of radiation absorbed by our bodies.

The possibility that a field reversal would be an extinction event is very low. There is very little historical evidence to show that previous reversals have caused extinctions. Humans have been on Earth for millions 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 outer 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!

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 underlines the importance of getting reliable information, backed by strong evidence.

Level5 Unit3 Part4 Vocabulary

Decision-Making Verbs

Resume, 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.

Interrupt, to stop something in progress. I hate to be interrupted when I'm working, but sometimes it's necessary. It's difficult to have a conversation with her because she always interrupts.

Reconsider, to?reassess or think again about changing something. I was planning to vote against him, but after hearing him speak, I'm going to reconsider. I didn't want to hire her at first, but then I reconsidered and offered her the job.

Conclude, to reach a decision, to end something or?summarize the main points. To conclude my presentation, here is a summary of my recommendations. After hearing arguments for and against the project, we have reached a conclusion.

Anticipate, to think in advance, to predict what's ahead. I won the game, because it was easy to anticipate my?opponent's next move. He try to anticipate what we are going to do, but he was completely wrong, so he lost.

Status of Affairs

Permanent, to be?fixed or unchanging, the opposite of?temporary. He plans to stay there permanently. He has decided to become a permanent resident of China.

Temporary, only lasting for a short time,?the opposite of permanent. We can only offer him a temporary position in the company. This isn't the kind of job he wants, but it's ok as something temporary, until he can find something better.

Definite, well defined,?precise, certain, unchanging. We can't begin the project until you give us?a?more definite schedule. We can't give you a definite answer until we get more information.

Obvious, easy to see, stands out. Of the job candidates we interviewed, he was the obvious choice. It's obvious that he can't afford to buy that house.

Trivial, of little or no importance,?insignificant. It's a trivial detail, so there is no need to worry about it. Those problems are not trivial, so we need to find a solution.

Level5 Unit3 Part4 Dialogue

Argument over Investment

I just heard what you did.

You did it without?consulting me.

Yes, I talked to them and decided to invest more money.

I didn't have time to consult with you. and I trusted them.

That's our money not yours.

We've been saving it to buy a house.

You had no right to make that decision without letting me know.

How can I trust you?

Look, it was an opportunity I couldn't?resist.

I'm sure it's going to be ok.

No it isn't.

It's a stupid investment and it's going to fail.

I really hate you now.

That's a really strong word for simply disagreeing.

Why can't we disagree without becoming so emotional.

We aren't just disagreeing.

You've broken your promise again.

I can't trust you anymore, especially when you keep doing stupid things that affect me.

You say I'm being stupid, but it's just that we don't agree.

No, that's not the point.

You are not listening.

You said you wouldn't do anything unless we both agreed.

And look what you've done.

Your promises are just empty words.

I really?despise you now.

Well, what should we do?

If you keep talking like that, we had better break up.

Yes, we should.

I've had enough.

I don't want to see you anymore, and I don't want you to even contact me.

Sure,?if that's what you really want.

But I want you to know that I haven't been lying to you.

Don't say anything more.

I don't want to hear it.

You are a fool and you can't even see what you are doing.

Hi, I'm calling to apologize.

Did you get my flowers?

Yes, but I told you not to call me.

Yes, I know, but I don't want our relationship to end like this.

We've been through too much together.

Let's give it another try.

I'm sorry.

I think it's too late.

This was the last?straw.

Please give me another chance.

You were right about everything.

I'll try to get the money back.

When you get the money back you can call me again.

If you don't, you can pay me what you owe me, and then leave me alone.

OK, I'll get it back.

I'll do anything to get you back in my life.

I'll think about it.