SCIENCE IN THE NEWS - Stephen Hawking and Black Holes / Quan

SCIENCE IN THE NEWS - Stephen Hawking¹ and Black Holes / Quantum Theory
By Caty Weaver²

Broadcast: Tuesday, August 17, 2004

VOICE ONE:

This is SCIENCE IN THE NEWS, in VOA Special English. I'm Bob Doughty³.

VOICE TWO:

And I'm Sarah Long. When a world famous scientist admits being wrong about something, people hear about it. But when the subject is something like quantum theory, they might not understand it.

VOICE ONE:

So we will try our best to explain quantum theory ... coming up this week on SCIENCE IN THE NEWS.

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VOICE TWO:

 
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Recently, the physicist⁵ Stephen Hawking had an announcement that made news around the world. Mister Hawking is the Lucasian Professor of Mathematics at the University of Cambridge in England. He was in Ireland at the Seventeenth International Conference on General Relativity. This was his announcement: he has changed his mind about black holes.

Professor Hawking admitted that he had been wrong for thirty years. He presented a new theory. He says he now accepts that black holes cannot destroy the information about the objects they swallow.

VOICE ONE:

Black holes are generally the remains⁶ of exploded stars -- big stars. Black holes are extremely dense⁷. The gravity they produce is great enough to pull in other objects from space. Scientists tell us this force is so great that not even light can escape.

In nineteen seventy five, Stephen Hawking declared that black holes destroyed all evidence of whatever they swallowed. He said any information about matter eaten by a black hole would cease to exist.

VOICE TWO:

Other physicists⁸ who study space found that declaration difficult to swallow. Many argued that the total loss of information would be impossible; it would violate the laws of quantum theory.

The other astrophysicists argued that there must have been a mistake in Professor Hawking's math. Over the years, some found a compromise. They presented mathematical arguments to permit conflicting theories about information in black holes. But no scientist was able to discover the problem in the professor's work.

Now Stephen Hawking says he has found the mistakes himself. He says he redid his work from nineteen seventy five, but in a new way. He says the new results show that information about what is inside a black hole is carried back out to the universe by radiation. Professor Hawking's work in the nineteen seventies had shown that black holes release radiation. In fact, scientists call this Hawking Radiation.

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VOICE ONE:

You are listening to SCIENCE IN THE NEWS, in VOA Special English.

Stephen Hawking says his recent work shows something new about the surface of a black hole. This surface is called the event horizon. The professor says changes that take place in the event horizon permit information to leak out of the black hole.

However, he says the information would be changed by the black hole experience. By this theory, the information would be so changed that it could not be recognized. Stephen Hawking said he would publish a complete description of his new work in professional journals and on the Internet.

The findings could help the scientific efforts to find what is called a Theory of Everything. Physicists hope to be able to find the link between the laws that govern the smallest parts of matter with those that guide larger objects in the universe. These laws often appear to conflict.

VOICE TWO:

The changes that Professor Hawking describes in the surface of black holes are quantum changes. Quantum theory describes how energy and matter act at the level of atoms and particles of atoms. It now guides most research in physics.

In nineteen hundred, the German physicist Max Planck wrote a paper that dealt with two forms of energy: heat and light. At the time, scientists did not understand why increased heat leads to changes in the color of light. A common example involves what happens to a piece of metal that is heated. As the temperature increases, the metal becomes red. As the metal gets hotter and hotter, it turns yellow and then white. But why?

To explain this, Planck said atoms and molecules⁹ must affect energy in small, separate parts. He called these divisions of energy "quanta." Material loses light energy as it is heated. The color of that light is the result of the number of quanta lost. Planck described an unchanging balance between the energy of each quantum and the color of the light. This balance is known as Planck's constant.

Before his paper, scientists thought energy changed in a continuous flow. But the new work showed that changes in huge numbers of extremely small parts simply make it appear that way.

VOICE ONE:

Max Planck's finding was the beginning of quantum mechanics. This describes how matter and radiation operate at the atomic level. Quantum mechanics describes the structure of the atom and the movement of its particles. It also explores how atoms take in energy and release energy as light.

Physicists hope quantum mechanics will help them to understand actions that conflict with traditional laws of physics. Isaac Newton developed his theories in England three centuries ago based on normal human experience. But scientists now know that extremely small particles and systems do not follow those laws of nature that Newton observed. Such conflicts must be settled if scientists are to reach a single theory for everything.

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VOICE TWO:

Several major ideas guide quantum mechanics. One is the idea that energy is divided into parts. Another is that light energy exists at the same time both as particles and as a wave. A person sees light particles. But the particles are spread out in an area that includes places where they could be but are not. So the probability of where each particle will be means that light acts like a wave.

Another major part of quantum mechanics is called Schrodinger's Equation. Erwin Schrodinger, an Austrian, developed this idea in the middle of the nineteen twenties. It basically says that the act of measurement changes the nature of that which is being measured. In everyday life, the effect of this interference is too small to notice. But, as we said, things are different in the world of atoms and subatomic particles.

For example, scientists need light to see an electron before they can measure it. But light is made up of photons. These will affect the movement of the electron.

VOICE ONE:

Another major part of quantum mechanics is called the Uncertainty¹⁰ Principle. The German scientist Werner Heisenberg proposed this idea. The basic explanation is that the exact position of a particle and its speed and direction can never be known together. In other words, you can measure either the position or the momentum¹¹. But if you measure one, you sacrifice the other. So it is impossible to know both at the same time.

But scientists can at least mathematically predict how matter will act in ways we would think impossible. Again, it is all about probability.

VOICE TWO:

The study of quantum mechanics has uses in areas like chemistry, molecular¹² biology and information technology. It has already led to smaller and more powerful computers.

Quantum theory has also led to a greater understanding of the universe. The same is true of Albert Einstein's general theory of relativity. But Einstein's theory deals with larger structures in the universe; quantum theory deals with the very opposite.

Some scientists are at work to combine these two theories into a theory of everything. This could help explain the formation of the universe from the very beginning of time.

VOICE ONE:

One of the scientists involved in this effort is Stephen Hawking. Many people know about his work from his popular book "A Brief History of Time."

Professor Hawking is sixty-two years old. That makes him one of the oldest survivors¹³ of A.L.S., or amyotrophic lateral¹⁴ sclerosis. Americans call this Lou Gherig's disease, after a baseball player who had it. The disease attacks the nervous system.

Stephen Hawking uses a wheelchair. And he uses a computer to speak for him. He enters words one letter at a time. Then the computer serves as his voice.

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VOICE TWO:

SCIENCE IN THE NEWS was written by Caty Weaver and produced by Cynthia Kirk. This is Bob Doughty.

VOICE ONE:

And this is Sarah Long. If you have a question for our program, or a comment, we want to hear from you. Send an e-mail to [email protected]. And please tell us your name and where you are writing from. Our postal¹⁵ address is VOA Special English, Washington D.C., two-zero-two-three-seven, U.S.A.

Join us again next week for more news about science, in Special English, on the Voice of America.

1 hawking   

利用鹰行猎

参考例句：

• He is hawking his goods everywhere. 他在到处兜售他的货物。
• We obtain the event horizon and the Hawking spectrumformula. 得到了黑洞的局部事件视界位置和Hawking温度以及Klein—Gordon粒子的Hawking辐射谱。

2 weaver   

n.织布工；编织者

参考例句：

• She was a fast weaver and the cloth was very good.她织布织得很快，而且布的质量很好。
• The eager weaver did not notice my confusion.热心的纺织工人没有注意到我的狼狈相。

3 doughty   

adj.勇猛的，坚强的

参考例句：

• Most of successful men have the characteristics of contumacy and doughty.绝大多数成功人士都有共同的特质：脾气倔强，性格刚强。
• The doughty old man battled his illness with fierce determination.坚强的老人用巨大毅力与疾病作斗争。

4 graphic   

adj.生动的，形象的，绘画的，文字的，图表的

参考例句：

• The book gave a graphic description of the war.这本书生动地描述了战争的情况。
• Distinguish important text items in lists with graphic icons.用图标来区分重要的文本项。

5 physicist   

n.物理学家，研究物理学的人

参考例句：

• He is a physicist of the first rank.他是一流的物理学家。
• The successful physicist never puts on airs.这位卓有成就的物理学家从不摆架子。

6 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

7 dense   

a.密集的，稠密的，浓密的；密度大的

参考例句：

• The general ambushed his troops in the dense woods. 将军把部队埋伏在浓密的树林里。
• The path was completely covered by the dense foliage. 小路被树叶厚厚地盖了一层。

8 physicists   

物理学家( physicist的名词复数 )

参考例句：

• For many particle physicists, however, it was a year of frustration. 对于许多粒子物理学家来说，这是受挫折的一年。 来自英汉非文学 - 科技
• Physicists seek rules or patterns to provide a framework. 物理学家寻求用法则或图式来构成一个框架。

9 molecules   

分子( molecule的名词复数 )

参考例句：

• The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。
• Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。

10 uncertainty   

n.易变，靠不住，不确知，不确定的事物

参考例句：

• Her comments will add to the uncertainty of the situation.她的批评将会使局势更加不稳定。
• After six weeks of uncertainty,the strain was beginning to take its toll.6个星期的忐忑不安后，压力开始产生影响了。

11 momentum   

n.动力，冲力，势头；动量

参考例句：

• We exploit the energy and momentum conservation laws in this way.我们就是这样利用能量和动量守恒定律的。
• The law of momentum conservation could supplant Newton's third law.动量守恒定律可以取代牛顿第三定律。

12 molecular   

adj.分子的；克分子的

参考例句：

• The research will provide direct insight into molecular mechanisms.这项研究将使人能够直接地了解分子的机理。
• For the pressure to become zero, molecular bombardment must cease.当压强趋近于零时，分子的碰撞就停止了。

13 survivors   

幸存者，残存者，生还者( survivor的名词复数 )

参考例句：

• The survivors were adrift in a lifeboat for six days. 幸存者在救生艇上漂流了六天。
• survivors clinging to a raft 紧紧抓住救生筏的幸存者

14 lateral   

adj.侧面的，旁边的

参考例句：

• An airfoil that controls lateral motion.能够控制横向飞行的机翼。
• Mr.Dawson walked into the court from a lateral door.道森先生从一个侧面的门走进法庭。

15 postal   

adj.邮政的，邮局的

参考例句：

• A postal network now covers the whole country.邮路遍及全国。
• Remember to use postal code.勿忘使用邮政编码。