The Structure of the Universe

The way in which we currently view the structure of the universe has been developed throughout centuries by various astronomers whose predictions and observations have all aided in the development of this model.

Aristotle based his model of the universe on Pythagorean theory which described the Earth as a sphere. His claims of a round Earth were reinforced by three observations. The first of these was that all Earthly matter moved towards the centre of the Earth, and this would consequently produce a sphere. The second observation was that if the Earth was flat, then lunar eclipses would not portray segments which possessed a curved outline. The last of these observations claimed that if or when a person travels North or South, they do not in both cases observe the same stars, nor are they positioned identically. Aristotle also hypothesised a geocentric universe. This means that a static Earth is orbited by its moon, the sun and all of the other planets-which were believed to be homocentric spheres- in perfect God-like circles. Aristotle also claimed that beyond all of the planets, the stars were embedded in a larger sphere, which too rotated. In 140 AD, this model of the universe was refined by Ptolemy who additionally included epicycles. Aristotle furthermore postulated that the world, which lay below the moon, was imperfect and corruptible whereas that which lay beyond the moon was incorruptible and designed to perfection. He supposed that the substances upon Earth consisted of four dissimilar elements- water, air, fire and earth- whereas the ‘heavens’ above were created of quintessence. This model was widely accepted as it complied with religious views and predominated over all others for close to two-thousand years. The str...

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... his announcement of his theories, Einstein applied his General Theory of Relativity to establish a model of the structure of the universe in which he believed the universe to be infinite and unchanging but this idea was not supported by relativity. In attempt to fix this issue to satisfy his theory, Einstein introduced a positive cosmological constant by which the universe could exist as a static, infinite sphere. The strengths of Einstein’s model were his idea of a curved space-time and the introduction of his General Theory of Relativity describing that time moved slower near an object the size of a planet. A major weakness of his model was that he believed the universe a static and eternal continuum which was later disproved. Technology limited the development of this model as many outcomes of his predictions could not be tested because technology was limited.