Customer Reviews

The Earth in Context: A Guide to the Solar System (Springer-Praxis Series in Astronomy and Space Sciences)

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The advent of the space age in 1957 has led to a quantum leap in mankind's knowledge of the Earth and its neighbors in the Solar System. After writing the most comprehensive book about the geologic work of the Apollo astronauts on the Moon ("Exploring the Moon", David Harland has turned to the exploration of the Solar System, and more specifically, the place of the Earth within it. The acceptance by the scientific community in the 1960's of the idea of "plate tectonics" as the mechanism to explain the large-scale geological evolution of the Earth has led to interest in determining the evolutionary process of the other bodies in the Solar System to fill out the picture and to tie all of this to the development of the conditions necessary for the sustenance of life on Earth. All of this is covered in this book.

One of the most important features of this book is an historical survey of the growth of the body of knowledge of the other bodies in the Solar System, starting with the invention of the telescope in the 17th century, and how this has evolved with improvements in observational technology down to our own time.

The author then leads us to the important question regarding the possible uniqueness of life on Earth, and why, if it is unique, this should be the case, especially considering that Earth's neighbors, Mars and Venus are similar to Earth in many ways and yet have evolved in radically different directions which are inimical to the sustenance of life as we know it (of course, the discovery of living organisms in hydrothermal vents where there is no oxygen at the bottom of the ocean is forcing scientists to broaden their views of what life-friendly environments are really like). For example, only the Earth, among the four terrestrial planets has a large, natural satellite. Why is this? If the Moon didn't exist there would be no life on Earth because the presence of the Moon keeps the Earth's orbit stable and prevents the obliquity of the spin axis from changing. All this leads to a stable thermal environment, vital for life to exist. Similarly, it is now believed that the water present on Earth was brought to the planet from comets originating in the outer Solar System. Another important question is why the Earth has plate tectonics whereas Mars certainly doesn't and Venus probably doesn't. Thus, we see that in order to understand our own planet, it is vital to understand the process that work on all the others and to know what is happening even at the outermost reaches of the Solar System. This book surveys all these matters, giving the layman a comprehensive picture of the current state of knowledge.

The book has an extensive glossary, but I would primarily recommend it to someone who has at least some college-level background in physics, engineering or other physical science in order to fully appreciate it.