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Vol. XVI, No. 2
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senses or external equipments cannot be obtained faster than the velocity of light. Consequently, the time taken by an observer in perceiving any event cannot be lessened beyond a certain limit. That is to say that the definition of simultaneity depends upon the spatial distance between the point of event and the observer.
This relation of space with time can be clearly understood by the example. A is the point of observer and B is the point of event (say, a collision between two cars). The instant of the observation of the event and the instant of the happening of the event are not the same, for the light will take a finite time to travel the distance A B. Thus, the time, which we term as 'present in our daily practice, is not a single instant but comprises of the whole interval that has elapsed between the happening of the event and the perceiving of the event by the observer, and the length of the interval will depend upon the distance between the observer and the point of event. It should be noticed here that however small the distance AB may be light, on account of its finite velocity, will take finite time to traverse it.
A practical astronomical example will reveal the importance of the new character of space and time. If, in the above example, B is a star 50 light - years * away from the earth and A is the observer on the earth making the observation of the events on the star through a telescope. Now, suppose that an explosion on the star is being observed by the observer. In our ordinary expression, we shall say that the event of observation on the earth and the event of explosion on the star are simultaneously taking place. But is it ture ? No, Since the star is 50 light years away from the earth, the light from the star will take 50 years to reach the earth It means that the explosion which is being observed 'Now', had already taken place 50 years ago. Thus, it be. comes clear that the term 'simultaneous' has not remained absolute. but it depends upon the distance between the two events. In other words, space and time are related to each other and the event universe are effected by them jointly. Physical Implications
1. During the discussion of Michelson-Morley experiment, we have seen that Lorentz and Fitzgerald explain the nul result by showing the contraction in space-and-time-dimensions. These are popularly known as 'Fitzgerald-Lorentz Contractions' and their values can be found by 'Lorentz Mathematical Equations'.
Ein leiu's theory of relativity also implies that when a system
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