Universe (1)

The oldest documented views on the structure of the Universe come from Babylonia and Ancient Egypt. They include religious and mythological elements like gods, heavens, underworlds etc. The first attempt to describe the working of the Universe within a scientific framework was the Ptolemy system. It originated in Alexandria – the learning centre founded by Alexander the Great – and was broadly based on the ideas contributed by the Greeks. It went something like this:

  • The Earth is the centre of the Universe
  • The Earth is surrounded by seven concentric spherical shells occupied by the six planets known to the Ancients plus the Sun
  • Some planets are locked inside smaller solid spheres housed within the primary shells
  • The shells/spheres are made of ether – a transparent and indestructible material filling the Universe outside the thin layer of air surrounding the Earth
  • All shells/spheres revolve seamlessly and uniformly to produce the planetary motion seen from the Earth
  • The Universe is perfect, unchanging and eternal – the shells/spheres will keep revolving forever
  • The irregularities in the movement of planets can be explained by rotation of the small solid spheres within the primary concentric shells
  • The space outside the seventh shell is filled with stars which are motionless
  • The very outer sphere is the seat of Primal Mover who is overseeing the show

This concept of the Universe survived well into the Middle Ages and was hijacked by Church and the rulers to justify the social status quo. Since God had created the Universe in perfect order and everything moved like clockwork the counts, kings and Popes were all part of this unchallengeable setup (thus said Ptolemy). So dare you not play up.

There were however some questions which the Ptolemy system had no answer to. For example, if the Earth is so special why does Primal Mover reside so far away from it? Or how to explain the supernovae which appear for a short period of time and fade away (the outer sphere with the stars was supposed to be perfect and unchanging). Despite these pesky problems the Ptolemy system was the official view of the Universe, taught at schools and preached from the pulpits. This is what all people in the Middle Ages, educated and commoners alike, thought the Universe was.

Then came a series of setbacks which ultimately killed the Ptolemy thing. First, Copernicus realised that it was possible to explain the celestial motions while keeping Sun in the centre of the Universe (although he still thought that the planetary orbits were circular). The Copernican idea was further refined by Galileo. Then Tycho Brahe confirmed that comets were not atmospheric phenomena but actually traveled through outer space (deemed to be filled with indestructible, crystalline ether). Then Keller found out that planetary orbits were not “perfect” circles but ellipses, negating the concept of revolving, onion-layered spheres. To add insult to injury Jupiter’s moons were discovered requiring even more levels of nested spheres to make things work. This was too much for Vatican and they gave up on patching up the Ptolemy model to fit the observations.

It is important to realise that the Ptolemy system was a kinematic model striving to explain the celestial motion observed from the Earth. The reason it is wrong is not that it places the Earth in the centre of the Universe. In our current understanding any location is a “centre” of its own reference frame and all movement is relative. The Ptolemy system failed because it could not explain the relative movement of the celestial bodies, regardless of the adopted frame of reference.

Ok, so there are no crystal spheres. How does the Universe work then?

Universe (2)

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