Questions. 1) What is the purpose of this article?

1) What is the purpose of this article?

2) What are two main procedures for a theoretical physicist?

3) What is meant by working from the experimental basis?

4) What is meant by working from the mathematical basis?

5) What does the choice of the procedure depend on?

Note

1) extremes – крайности

TEXT 7

RADIUM

The early alchemists¹ spent most of their time trying to change common metals such as lead into gold. Many people laughed at the idea. The alchemists had no clear notion of what they were doing. They simply tried all sorts of strange "recipes" and hoped to make the change take place by magic.

Now the scientists know that the alchemists were not entirely wrong. For it is possible for certain metals to change into others. The discovery and study of radium showed that this is true. The al­chemists would be unhappy, however, because radium, which is thou­sands of times more expensive than gold, goes through a series of changes and becomes common lead.

Radium is one of the simple substances, or elements, that scien­tists call radioactive. Radioactive elements change all by themselves into other elements. As they do so, they send out powerful rays.-These rays can go through many substances that light cannot go through. The rays from radium, for instance, can go through flesh and be used to treat such diseases as cancer.

A common use of radium is in paint. Paint containing very tiny amounts of this element is used on the hands of clocks and watches to make them glow in the dark. Chemicals in the paint give out flashes of light when hit by rays from the radium.

Carelessly used radium can cause terrible burns. Supplies of it must be kept in special containers with thick lead walls.

Pure radium is a white metal. It is very heavy. But there is so little of it that no one has ever been bothered by its weight. Only a few pounds have been produced in the whole world.

Radium was discovered by the French scientists Pierre and Marie Curie. The story of their work is one of the really exciting chapters in the story of science.

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