Ferreira, P. G. (2007) The State of the Universe: A primer in modern cosmology. London: Phoenix.

 

Ferreira, P. G. (2007) The State of the Universe: A primer in modern cosmology. London: Phoenix. (An imprint of Orion Books, an Hachette Livre UK company.) (Original, 2006.)

 

Introduction

I am a practising cosmologist. My job is to try to unravel the history and workings of the Universe, using a combination of mathematical tools, observations made with powerful telescopes and, above all, educated guesses. (p. 9)

 

The best we can do is to predict what may happen on earth over a few days. In contrast, our current model of the Universe is remarkably successful. It can describe the whole of the Universe over billions of years, within a much simpler and more elegant framework. (p. 10)

 

1. A mechanical Universe

Cosmology is the science of the origin and evolution of our Universe. … our view of what constitutes ‘the Universe’ has changed over time as a result of the interplay between theoretical prejudices and observational breakthroughs. (p. 13)

Pythagoras (582-496 BC). The earth is at the centre of the universe and the planets, the sun and the moon orbit it in perfect concentric spheres or wheels each at a different speed, creating a cosmos in constant motion and perfect harmony.

Plato (428-348 BC). The Universe consists of concentric spheres rotating at uniform speed within each other. Any mismatch between theory and observation is due to our inability to make accurate measurements, so the only way to build a model of the Universe is through pure reason.

Aristotle (384-322 BC). The Universe consists of 9 transparent concentric spheres spinning around the earth, supported by a set of 46 transparent, nested spheres. Outermost is the unchanging heavens, while the intermediary spheres contained the various planets. This model explained the motion of most of the planets; its failure to explain the remainder was explained through Plato’s mistrust of measurements.

Facing the problems of geocentric models. The Greeks had sufficient data to contradict geocentric models and responded in two ways:

·     Aristarchus (310-230 BC) proposed a heliocentric Universe in which the planets’ orbits moved together and apart at different times. His model was rejected.

·     Ptolemy (85-165 AD) proposed a geocentric Universe, but his model (unlike Aristotle’s) accorded more closely with the observed motions of the planets: the earth wasn’t quite at the centre and the planets moved in eccentric orbits.

Nicolaus Copernicus (1473-1543). The first to formulate a scientifically based heliocentric universe featuring uniform orbits, but including eccentric orbits; and explaining the retrograde motion of the planets as the result of observing them from a moving earth. His De revolutionibus orbium coelestium ('On the Revolutions of the Celestial Spheres') is often regarded as the starting point of modern astronomy and the Scientific Revolution. Greek, Indian and Muslim savants had published heliocentric hypotheses centuries before, his heliocentrism was the first scientific theory of the universe.

 

 

 

Pythagoras (582-496 BC) Greek mathematician and astronomer.

• The Earth is at the centre of the universe and the Sun, the Moon and the planets orbit it, each at a different speed, in perfect concentric spheres or wheels[1].
• The spheres are related by the whole-number ratios of pure musical intervals, creating a cosmos in constant motion and in perfect musical harmony - a state described as musica universalis (lit. 'universal music' or 'music of the spheres').

 

Plato (428-348 BC) Greek philosopher.

• The Universe consists of concentric spheres rotating at uniform speed within each other.
• Any mismatch between theory and observation is due to our inability to make accurate measurements, so the only way to build a model of the Universe is through pure reason.

 

Aristotle (384-322 BC) Greek philosopher.

• The Universe consists of 9 transparent concentric spheres spinning around the earth, supported by a set of 46 transparent, nested spheres. Outermost is the unchanging heavens, while the intermediary spheres contained the various planets.
• This model explained the motion of most of the planets; its failure to explain the remainder was explained through Plato’s mistrust of measurements.

 

Nicolaus Copernicus (1473-1543).

• Posed the first scientifically based heliocentric universe[2].
• His De revolutionibus orbium coelestium ('On the Revolutions of the Celestial Spheres') is often regarded as the starting point of modern astronomy and the Scientific Revolution.
• Greek, Indian and Muslim savants had published heliocentric hypotheses centuries before, his heliocentrism was the first scientific theory of the universe.

 

 

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[1] The most thorough and imaginative description of the concept can be found in Dante's Divine Comedy.

[2] It featured uniform orbits, but including eccentric orbits; and explained the retrograde motion of the planets as the result of observing them from a moving earth.