Английский язык. Ч.3 (Units 9,10). Ильичева Н.А - 33 стр.

are the same in all reference frames implies that all inertial reference frames are
equivalent for the description of mechanical phenomena.


(3;…)
     In the last half of the nineteenth century there arose a complication. When
Maxwell presented his comprehensive and very successful theory of
electromagnetism, he showed that light can be considered an electromagnetic
wave. Maxwell’s equations predicted that the velocity of light c would be
3 · 108 m/s. The question then arose: in what reference frame does light have
precisely the value predicted by Maxwell’s theory? It was assumed that light
would have a different speed in different frames of reference. For example, if
observers were traveling on a rocket ship at a speed of 1 · 108 m/s away from a
source of light, we might expect them to measure the speed of light reaching
them to be 3 · 108 m/s – 1 · 108 m/s = 2 · 108 m/s. Nineteenth-century physicists
viewed the material world in terms of the laws of mechanics, so it was natural
for them to assume that light too must travel in some medium. They called this
transparent medium the ether and assumed it permeated all space. It was
therefore assumed that the velocity of light given by Maxwell’s equation must
be with respect to the ether. However, it appeared that Maxwell’s equations did
not satisfy the relativity principle. They were not the same in all inertial
frames. They were simplest in a reference frames at rest in the ether. Thus,
although most of the laws of physics obeyed the relativity principle, the laws
of electricity and magnetism apparently did not. Instead, they seemed to single
out one reference frame that was better than any other – a reference frame that
could be considered absolutely at rest.


(4;…)
    The problems that existed at the turn of the century with regard to
electromagnetic theory and Newtonian mechanics were beautifully resolved by
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