6 Minute English - The earth's core



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have you ever read any books by XXX. Jules Verne?

 Yes, I have. Journey to the Centre of the Earth was my favourite book as a child! A German Professor and his two companies companions climb down the a volcano in search of the Earth's centre - – or core. They visit strange lands inhabited by dinosaurs and giant prehistoric humans, and sealing sail across an underground ocean. Very exciting but it doesn't sound very realistic. How did do they get out again? Well, they shoot to the surface from the mouth of the Mount Etna during a volcanic eruption. Well. Wow! That sounds very uncomfortable! Well along Well, on today's show we're going to discuss what scientists really know about the Earth's core.

 Yes. The Earth has the a dense inner core surrounded by a fluid outer core. Dense, by the way, means heavy in relation to its size. But, Rob, I've got a question for you as usual: how big do you think the inner core is? Is it the size of... of… a) the Moon? b) Jupiter? or c) Mars? Right, Right! Well, I haven't the a clue to be honest so I'm going to take a guess and say c) Mars. Well, we'll find out later on in the show if you're right. But Rob Ihave a good before we get that, there, let's find out a bit more about what the Earth is made of. Well, the earth Earth has layers, a bit like an onion. I like your tactical technical language, Rob!

 But I try But I'm trying to keep things simple for you, There Alice! It has a thin outer layer or crust where we live. And this th includes are our continents and the ocean floors. Then beneath that there's another layer called the mantle. And beneath that that, there is is the Earth's core – over 6000km below the surface. Right. But what's the Earth made of, Rob? A It's a good question. And it depends on which layer you're talking about! The crust and mantle are rock and contain a lot of silica silicate – which is the same stuff the that glass is made of. But the outer and inner parts of the core mainly consisted consist of iron. And the core is very hot. Am I right?

 You are indeed. The professor and his companions wouldn't have survived very long down there! The outer core is a swelling swirling mass of molten – or liquid – metal and it's as hot as the surface of the Sun! Wow! That must be so hot! Right. Let's listen now to XXXX Simon Redfern talking about the inner core and what was what's happening in there. And so over time, the planet has started to cool. And as it cools, eventually at the centre of the Earth, the highest pressure of point, we pass over the crystallization temperature – the temperature iron. I am started to press the present of the earth freezing temperature of iron – and iron starts to freeze atthe centre of the Earth. And you get the a crystal of iron right in the middle and that starts to grow. I'm a bit worried that the Earth is freezing in the middle! Don't too worry, Alice! In this case, because of the incredibly high pressure in the core, the freezing point of iron is actually about 6000 degrees! And the iron has been cooling down and crystallization crystallizing for a billion years and the – and at a rate is of just half and million amillimetre every year.

 Oh well, yes, that sounds like small slow progress. Certainly. Now moving on, we should also talk about the fact of that it's the liquid iron outer core that generates magnetic fields – and this existence of magnetic fields it'sthanks to these magnetic fields that life on Earth is possible. Let's hear more about this. Well, the magnetic field is very important because it protects us against cosmic radiation. radiation so that's one .. really... How theydoes it do that? It just creates a shield, which will just deflect the cosmic rays from the Sun to reach us. And So it protects us. So it goes ... actually reach us at the surface. So it protects us. So it goes up there… Yeah, soyou would see that the radiation kind of goes round the Earth and not actually reach us. So there's a magnetic field round the Earth that protects us from the Sun's cosmic rays. I'd like the a magnetic field round me. It could be my superpower - like the X-Men! – like in X Men! Calm down, Magneto. Now the magnetosphere is the area around the Earth in which the Earth's magnetic field this is felt. It protects us from the Sun's radiation and the flow of particles, which with would otherwise strip away – or remove – the Earth's atmosphere. Right, I see. And what does 'radiation' mean? A Well, radiation means heat or energy or particles in the form of rays -In – in this case, the Sun's rays. OK. And 'deflect'? To deflect means to make something change direction. Right, I see. Thank you. Now, Rob, I ask asked you, the do you remember, at the beginning of the show, how big is the Earth's inner core.

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