Albert Einstein worked as an examiner for the Swiss patent office. He had difficulty passing examinations. He had tried teaching physics but was a lousy teacher and had lost several jobs. Einstein loved simplicity, in his daily life as well as in his thinking. In 1916, he published the general
theory of
relativity – a new way of looking at the world.
The basis of the theory of relativity is the principle of sameness which states that gravity (force) and inertia (resistance to force) are the same. This is because the frame of reference changes with the position of the observer. It is equally true to say that the earth rotates relative to the
universe or to say that the universe rotates around the earth. It all depends upon one’s frame of reference. Both points of view are correct, they are only different ways of saying one and the same thing. (It is all a matter of words, it is as meaningless to ask if the ice-cream is on top of the pie or the pie is under the ice-cream)
In the general theory of relativity Einstein adopted a four-dimensional model, time being the fourth dimension. All it means is that events that take place in the universe occur in a four-dimensional world of
space and time (“spacetime”). If an object is motionless in space, it is still travelling through time. Nothing strange about that – that is the everyday world we live in. What the theory of relativity does is not to treat space and time separately, but together as “spacetime”.
The
structure of space and time cannot be determined without observation and experiment. According to Einstein, the structure of this “spacetime” is warped or curved by the presence of large objects like the sun. The larger question, whether the
stars give rise to the geometry of “spacetime” or the geometry of “spacetime” gives rise to the stars, is still being debated by philosophers and scientists alike.
Many models of the universe, based on the theory of relativity, were proposed and debated. Some of them have properties stranger than one could imagine. The notion of an expanding universe is widely accepted nowadays. Working backwards, we arrive at the moment of creation, the so-called big-bang. What will eventually happen to the expanding universe? All that can be said with certainty is that nothing can be said with certainty!
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