John Chambers and Jacqueline Mitton. From Dust to Life: The Origin and Evolution of Our Solar System. Princeton University Press, 2014

The intention of the authors is "to write for general readers who have some basic understanding of science, but not necessarily any specialist knowledge of the solar system and its origin".

Early studies of the solar system were hindered by astronomers' adherence to the opinion of the Greek philosopher Aristotle (384-322 BC) who considered it a matter of common sense that Earth was the centre of the cosmos. The use of this model made the apparent motions of the planets very complicated. Progress towards the familiar sun-centred model began with the work of Copernicus, which was refined by later astronomers.

In the 18th century astronomers set about measuring the astronomical unit (AU), the average distance between Earth and Sun. This was used to establish the scale of the solar system. This was done by combining the results of observations from different locations of the transit of Venus on 3 June 1769, to make the necessary calculations.

Improved telescopes were making it possible to discover more planets, as well as comets and asteroids. In 1781 German musician and keen amateur astronomer William Herschel, who had settled in England, discovered a new planet. He wanted to call it "George", after his patron, King George III, but it was eventually agreed that it should be named Uranus.

From about the middle of the 19th century scientists started attempting to discover the age of the solar system. Various methods were used to attempt to estimate the age of the Earth, but gave conflicting results. Then the discovery of radioactivity made more accurate calculations possible and it was eventually concluded that Earth was 4.55 billion years old.

There are descriptions of how stars are formed, and of the evolution of the solar system. The various theories devised to account for the present state of the solar system, and how these have been facilitated by studying the information obtained from space probes, are particularly interesting. For example, scientists have had great difficulty in explaining the formation of the Earth-Moon system. The generally accepted theory at present is that Earth was struck a glancing blow by a Mars-sized object. Some of the material was absorbed by the Earth and the rest of it eventually formed the Moon. This hypothesis was tested by comparing the composition of the Moon with that of Earth, and by running computer simulations of the process.

The rings of Saturn are very familiar, but Jupiter, Uranus and Neptune also have them. These are very insubstantial and were thus unknown until those of Uranus were discovered in 1977, followed some years later by those of Jupiter and Neptune, discovered some years later by the Voyager 1 and 2 spacecraft. Saturn's rings are very bright as they are composed almost entirely of water ice.

This is a publication suitable for every amateur astronomer's bookshelf, as the authors have fulfilled their aim in giving clear descriptions of often complicated natural processes. -- John Harney

No comments:

Post a Comment