BBC 6分钟英语学习 曼哈顿项目

6 min English from BBC learning English dot com.

A Hello. This is 6 min English from BBC Learning English.

I'm Sam, and hello, I'm Bob.

On August the 6th, 1945, the US aircraft and Nola Gay dropped an atomic bomb on the city of Hiroshima, instantly killing

70000 people. When Japan refused to surrender, a 2nd bomb was dropped on Nagasaki three days later.

Many believe the bombings quickened the end of the 2nd World War, but it came as a terrible human cost, which some have called a crime against humanity.

The invention of the atomic bomb, which resulted from the cooperation between the US military and some of the world's leading scientific minds, was known as the Manhattan Project.

In this program, will take a look into the science and the politics of the Manhattan Project, and, as usual, will learn some new vocabulary as well.

Even before World War Two, scientists had known about the potential energy inside uranium, the heaviest metal in the periodic table, a diagram which groups the chemical elements into rows and columns according to their atomic number and symbol.

The challenge for science was learning how to unleash this potential energy in a controlled way.

We'll hear more soon, but 1st I have a question for you, rob I mention that uranium is the heaviest element in the periodic table, but which is the lightest?

Is it a hydrogen, B carbon or C oxygen?

Well, oxygen is a gas, so it must be pretty light, so I'll say, see, oxygen.

Okay? Well, we'll find out the answer later in the program.

1st let's find out a bit more about the science of uranium from Frank Close and Oxford, professor of theoretical physics, in conversation with BBC radio for program in our time.

Well, in 1938, the discovery was made that if you use uranium, the atoms of uranium are the heaviest that occur naturally in the periodic table.

They're very fragile. And the discovery was that if you just almost touched them with a single neutron, that's a nuclear particle, the uranium was like a drop of water.

It would just break apart, split in two.

And this action of splitting the uranium has become known as fishing atoms of uranium are very fragile, easily broken or damaged.

In 1938, it was discovered that when nuclear particles called neutrons were fired at uranium atoms, they would split or break into.

This process of splitting uranium or fission, did two things 1st, it released huge amounts of energy, a billion times more than would be released in a normal chemical reaction.

Secondly, the act of spitting atoms released two more neutrons.

These new neutrons were freed to hit more uranium, creating four neutrons, which in turn were freed and created eight, then 16, and so on, making what's known as a chemical chain reaction.

In everyday English, a chain reaction is a series of events, where each event becomes the cause of the next.

The politics behind the development of the atomic bomb was no less complex than the science.

In the same year that Hitler invaded Poland, two Jewish scientists exiled from Nazi Germany, rudolph Pierels and Otto Fish 1st realized uraniums power as a weapon of war.

Listen as Professor Frank Close takes up the story for BBC radio, for programme in our time.

Now, what happened at that moment was that, having had the idea and the shock of the discovery, you immediately then think, maybe scientists in Germany have already had the same idea and come to the same conclusions.

Could Hitler already be building such a weapon?

And in their memorandum, which they wrote and reached the British government, they said, it's conceivable that Germany is in fact developing this weapon, and the only defense against it is to have one yourself.

After their discovery, perels and fresh were worried that the Nazis had already found out how to weaponize uranium.

It was conceivable or believable that Germany was building an atomic bomb.

They share this terrifying thought in their famous memorandum, a short written report on a specific topic.

As soon as US President Franklin Roosevelt read it, he started the Manhattan project, and the race to build an atomic bomb began in a strange twist of history.

It turned out that Hitler hadn't been building atomic bombs at all, and Hiroshima, the

Japanese city destroyed in 1945, was rebuilt and stands as a symbol of peace today.

OK, let's end on a lighter note,

sam, with your question. Yes, I ask, which is the lightest element in the periodic table?

It's a hydrogen, the lightest

of all gases, which come at the very start of the periodic table, having the atomic number one.

Ah, if only I remembered what our chemistry teacher taught us about the periodic table.

That's a chart

grouping all the chemical elements according to their atomic number.

Let's wake up the rest of the vocabulary too.

If something is fragile, it's easily broken.

To split something means to break it into two parts.

A chain reaction happens when one event becomes a cause of the next.

A memorandum is a short written report on a specific topic.

And finally, the adjective conceivable means believable.

And that brings us to the end of our program.

We hope you'll join us again soon for more interesting issues.

Un useful vocabulary. Bye for now.

Goodbye. Six news English from the BBC.

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