I Unit - Our Picture of the Universe

OUR PICTURE OF THE UNIVERSE

Stephen Hawking narrates how mankind has come to frame the theories of the planetary system and the universe as a whole. He says that a unified theory regarding the birth and nature of the universe is essential. Man has always been fascinated by the mysteries of the universe, every age tried to explain the universe in its own way. The early people believed that the earth was a flat plate supported by a giant tortoise. An infinite number of tortoises supported the giant tortoise. Aristotle was the first to propose a scientific theory about the planetary system. He proposed the geo-centric theory. According to that theory the earth was the center of the universe with the sun the moon and the stars revolving around it. He was the first to propose that the earth was round by his observation of the shadow of the earth on the moon during eclipses. He confirmed his theory by the position of the North Star which appeared to be low when viewed from the South but appeared to be just over the head when viewed from the North. Next to Aristotle was Ptolemy. He too supported the views of Aristotle. Ptolemy gave the eight spears in which Earth was at the centre and Sun, Moon and the then discovered five planets formed the seven spears whereas stars formed the outermost eighth spear. He too said the revolution was circular in orbits.

Copernicus discounted the geo-centric theory and proposed helio-centric theory. According to that the Sun was the centre of the planetary system and the earth and other planets revolved around the Sun in circular orbits. But the actual observation did not match the predictions. Johannes Kepler and Galileo too believed in circular orbits in the beginning. Galileo invented telescope and found that few moon were revolving around Jupiter. This was a death blow to Aristotle-Ptolemic theory. Kepler suggested elliptical orbits for the planets. Now the predictions matched the observation. But Kepler could not explain what forces made the planets to revolve around the sun.

It was now Newton’s turn to give explanation for the motion of the planets and stars. He explained that the elliptical orbits of the moon round the earth and those of the planets round the sun were due to the gravitational forces. He gave us gravitational theory and also mathematical formulas to calculate the motions of plants and satellites. He explained that as there were infinite stars in the universe there was no centre for them to fall to. Newton’s law of gravitation showed that the universe showed that the universe could not remain static, later Edwin Hubble observed that the universe was expanding. He observed that the distant galaxies were moving rapidly away. So he believed that he heavenly objects were closer together earlier and hence the universe was dense. These discoveries brought forth the question about the beginning of the universe or tis origin. Hubble suggested that there was a time in the past called the Big Bang when the universe was very small and infinitely dense. Time had a beginning at the point of the Big Bang. Then the universe blew up with a bang to from the present state of the universe. It is still expanding.

Stephen say’s that God created the universe at any point of time in the past. If the universe was expanding here might be reasons why there had to be a beginning. It could be imagined that God created the universe at the time of the Big Bang or later, but not earlier. All there theories according to Stephen are partial theories. Thus a unified theory regarding the universe is necessary. As the universe appeared to be following certain laws, even the beginning must have had some laws. Those laws should be found to have a unified theory about the universe. Scientists have only tow partial theories to explain the universe. One is the general theory of relativity and the other is the quantum theory. The first is on a loage scale and the second is a mini scale. So Hawkin proposes the necessity of havng a quantum theory of gravity. Thus to explain the universe, a unified theory is essential. It satisfies man’s undying curiosity to know the unknown. So that he can solve the mystery of the universe.