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Text 9. Basic Facts of Nuclear Physics
In recent years tremendous advances have been made in the development of various branches of physics.
The most remarkable researchers of the twentieth century have substantiated two ideas about the nature of the matter which the Greek philosophers formulated twenty centuries ago. One is the theory that the many thousands of substances which exist in the world are formed out of a small number of simpler substances or elements (molecules). The other theory is that matter is constructed out of tiny particles or units, the so-called atoms of matter.
The modern scientist is convinced of the existence of molecules and atoms. Everything in and on the earth, the moon, the sun, and all other stars, is made of atoms. Billions of atoms together make everything that exists. Take a handful of air, and you will hold billions of atoms.
Look at your handful of atoms. You can't see a single one, no matter how hard you look, for every atom is too small to be seen even with a powerful microscope.
The atoms which form the molecules are, of course, smaller than the molecules, while the electrons of which the atoms are composed are yet smaller. From various experiments scientists concluded that the diameter of the average molecule is about one 125,000,000th of an inch. Since atoms compose molecules, they must be still smaller. If each atom in an orange measured one inch in diameter, the orange would be as large as the earth.
Molecules all vary in size, depending upon the number and size of the atoms which compose them. They vary from simple ones consisting of two atoms such as the hydrogen molecules, to complex ones, like those of starch, some of which contain as many as 2,500 atoms. Protein molecules are even larger than this.
Not all the atoms weigh the same amount. From the way atoms act, scientists have been able to compare their weight and list them in a table beginning with the lightest and ending with the heaviest. Such a table was created in 1869 by D. I. Mendeleyev, the great Russian scientist.
Hydrogen, the gas used in toy balloons, is very light. Uranium, the ore used for atomic energy production, is the heaviest, and its atom is the last in the table of atoms that exist naturally. Heavier ones which follow uranium in the table have been made by man.
The practical uses of nuclear energy are based on a knowledge of the structure of matter. Our knowledge of the internal structure of the atom is a twentienth century achievement. It is extremely new, so new in fact, that physicists realize that far more remains to be found out than has already been discovered. Yet that knowledge has already played an impotant part in the advance of chemistry and industry, and most recently in the peaceful use of atomic energy.
Notes
tremendous величезний
to advance просуватися
researcher науковець
substantial icmomнuй
to convince переконувати
billion мільярд
to conclude робити висновки
to vary змінювати(ся)