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Read the text, translate it and name important milestones in the history of physics.

The most advanced science at present and the one, which seems to give the most light on the structure of the world, is physics. It is useful to have some idea of not only what the up-to-date development of physics is but also how we came to think in that way and how the whole of modern physics is connected with its history. In fact, the history of this science begins with Galileo, but in order to understand his work it will be well to see what was thought before his time.

The scholastics, whose ideas were derived from Aristotle, thought that there were different laws for celestial and terrestrial bodies, and also for living and dead matter. There were four elements: earth, water, air and fire, of which earth and water were heavy, while air and fire were light. Earth and water had a natural downward motion, air and fire upward motion. There was no idea of one set of laws for all kinds of matter; there was no science of changes in the movements of bodies.

Galileo – and in a lesser degree Descartes – introduced the fundamental concepts and principles which were enough for physics until the present century. They showed that the laws of motion are the same for all kinds of dead matter and probably for living matter also.

Galileo introduced the two principles that made mathematical physics possible: the law of inertia and the parallelogram law. The law of inertia, now familiar as Newton’s first law of motion made it possible to calculate the motions of matter by means of the laws of dynamics alone.

Technically the principle of inertia meant that causal laws of physics should be stated in terms of acceleration, i.e. a change of velocity in amount or direction or both which was found in Newton’s law of gravitation. From the law of inertia it followed that the causal laws of dynamics must be differential equations of the second order, though this form of statement could not be made until Newton and Leibniz had developed the infinitesimal calculus. Most of what students do on the mathematical side of physics may be found in Newton’s Principia. The basic idea of dynamics, the equations of motion, the ideas of momentum, of inertia, of mass and acceleration were applied by Newton to large bodies like the Earth and the Moon to explain the structure and the motion of the universe. From Newton to the end of the 19th century, the progress of physics involved no basically new principles. The first revolutionary novelty was Planck’s introduction of the quantum constant h to explain the structure and behaviour of atoms in the year 1900. Another departure from Newtonian principles followed in 1905, when Einstein published his special theory of relativity. Ten years later he published his general theory of relativity which was primarily a geometrical theory of gravitation showing that the universe is expending.



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In fact, when modern science was growing up from the time of Galileo to the time of Newton, all the sciences were very much joined together. A single man could do absolutely first-class research in pure mathematics, in physics, in camistry and even in biology. Towards the end of that time the sciences were beginning to separate and after that they continued to separate more and more.

Just at this moment we can see a great convergence of all sciences. Physics is increasingly penetrating all the other parts of science and this is evident in the names of the new hybrid subjects. We have long had physical chemistry; now we have chemical physics, which is different not so much in the propotion of physics and chemistry, but in its central interest of extending the range of physics. A biologist cannot do without knowledge of modern physics, while a physicist must know something of biology, as he may find a great deal of his work will be concerned with biophysics. The mathematical aspect of physics is also becoming much more evident especially now that we are having a growing symbiosis between physics and mathimatics in computational physics.

Our job in physics is to see things simply, to understand a great many complicated phenomena in a unified way, in terms of a few simple principles. You cannot predict what will happen in future, but you have to be ready to meet it [1, C. 186-187].

 




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Section I The History of Physics | Find key sentences in the text and retell it.

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