Английский язык. Ч.3 (Units 9,10). Ильичева Н.А - 34 стр.

Einstein’s introduction of the theory of relativity in 1905. Einstein concluded
that the inconsistencies he found in electromagnetic theory were due to the
assumption that an absolute space exists. In his famous 1905 paper he proposed
doing away completely with the idea of ether and the accompanying assumption
of an absolute reference frame at rest. This proposal was embodied in two
postulates. The first postulate was an extension of the Newtonian relativity
principle to include not only the laws of mechanics but also those of the rest of
physics, including electricity and magnetism.
     First postulate (the relativity principle): The laws of physics have the same
form in all inertial reference frames.
The second postulate is consistent with the first.
     Second postulate (constancy of the speed of light): Light propagates
through empty space with a definite speed c independent of the speed or the
source of observer.
These two postulates form the foundation of Einstein’s special theory of
relativity.


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     One of the important consequences of the theory of relativity is that we can
no longer regard time as an absolute quantity. No one doubts that time flows
onward and never turns back. But the time interval between two events, even if
two events are simultaneous, depends on the observer’s reference frame. If the
two events occur at widely separated places, it is more difficult to know whether
the events are simultaneous since we have to take into account the time it takes
for the light from them to reach us. In other words events which are
simultaneous to one observer are not necessarily simultaneous to a second
observer. This fact suggests that time itself is not absolute. Einstein’s theory of
relativity predicts that it may pass differently in one reference frame than in
another. A general result of the theory is known as time dilation. The time
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