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Posts Tagged ‘Ptolemy’

Moon: From 4.5 billion years ago to the present: Owners’ Workshop Manual, David M. Harland (Haynes 2016)

It was a clever idea: to put out a guide to the Moon in the same format as one of Haynes’ famous car-maintenance manuals. And the execution matched the idea. This is a detailed and interesting history of selenological speculation and lunar exploration, all the way from the ancient Greeks to the Apollo missions and beyond.

Except that there hasn’t been much beyond the Apollo missions. As the book’s final page notes:

On 31 December 1999 National Public Radio in the United States asked Sir Arthur C. Clarke, renowned for forecasting many of the developments of the 20th century, whether anything had happened in the preceding 100 years that he never could have anticipated. “Yes, absolutely,” he replied without a moment’s hesitation. “The one thing that I never would have expected is that after centuries of wonder and imagination and aspiration, we would have gone to the Moon… and then stopped.” (“Postscript”, pg. 172)

And we’ve been stopped for some time. Neil Armstrong died in 2012, forty-three years after that “small step for a man” and “giant leap for mankind” in 1969. But David M. Harland ends on an optimistic note: he thinks that “The Moon is humanity’s future.” It will be our gateway to the rest of the solar system and perhaps even the stars.

But it will be more than just a gateway. There is still a lot we don’t understand about our nearest celestial neighbour and big surprises may still be in store. One thing we do now understand is that the scarred and pitted lunar surface got that way from the outside, not the inside. That is, the moon was bombarded with meteors, not convulsed by volcanoes. But that understanding, so obvious in hindsight, took a long time to reach and it was actually geologists, not astronomers, who promoted and proved it (ch. 5, “The origin of lunar craters”). It was the last big question to be settled before the age of lunar exploration began.

Previously scientists had looked at the Moon with their feet firmly on the ground; at the end of the 1950s, they began to send probes and robotic explorers. Harland takes a detailed look at what these machines looked like, how they worked and where they landed or flew. Then came the giant leap: the Apollo missions. They were an astonishing achievement: a 21st-century feat carried out with technology from the 1960s, as Harland puts it. Yet in one way they depended on technology much earlier than the 1960s: pen and paper. The missions relied on the equations set out in Newton’s Principia Mathematica (1687). Newton had wanted to explain, inter multa alia, why the Moon moved as it did.

By doing that, he also explained where a spacecraft would need to be aimed if it wanted to leave the Earth and go into orbit around the Moon. His was a great intellectual achievement just as the Apollo missions were a great technological achievement, but he famously said that he was “standing on the shoulders of giants”. Harland begins the book with those giants: the earlier scientists and mathematicians who looked up in wonder at the Moon and tried to understand its mysteries. Apollonius, Hipparchus and Ptolemy were giants in the classical world; Galileo, Brahe and Kepler were giants in the Renaissance. Then came Newton and the men behind the Apollo missions.

Are there more giants to come? The Moon may be colonized by private enterprise, not by a government, so the next big names in lunar history may be those of businessmen, not scientists, engineers and astronauts. But China, India and Japan have all begun sending probes to the Moon, so their citizens may follow. Unless some huge disaster gets in the way, it’s surely only a matter of time before more human beings step onto the lunar surface. Even with today’s technology it will be a great achievement and more reason to marvel at the Apollo missions. And the Apollo photographs still look good today.

There are lots of those photographs here, with detailed discussion of the men and machines that allowed them to be taken. The Moon is a fascinating place and this is an excellent guide to what we’ve learned and why we need to learn more.

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Discovering the UniverseDiscovering the Universe: The Story of Astronomy, Paul Murdin (Andre Deutsch 2014)

First published in 2011 as Mapping the Universe, this is a well-written, well-illustrated history of astronomy that begins in the Stone Age and ends with the Hubble Space Telescope and Large Hadron Collider. The photographs will stimulate your eyes as the text stimulates your mind. The universe is a big place and big things happen there, like gamma-ray bursts (GRBs):

Until 1997, astronomers didn’t know whether GRBs originated in some sort of explosions on the edge of our solar system, around our Galaxy, or far away. Two examples proved that the explosions occur the edge of the observable Universe. For their duration of a few seconds, the bursts had been over a million times brighter than their parent galaxy, the biggest bangs since the Big Bang. (ch. 17, “Exploding Stars”, pg. 87)

Ptolemy, Galileo and Newton would all be astonished by the technology that allows modern astronomers to study phenomena like gamma-ray bursts, but one thing has remained constant: the importance of mathematics and measurement in studying the sky. The story of astronomy is not just about seeing further and clearer, but also of measuring better and mathematizing more powerfully. Ptolemy’s geocentric universe entailed the arbitrary complexity of epicycles on epicycles, to explain how the planets sometimes seemed to move backwards against the stars. Then Copernicus resurrected the ancient Greek hypothesis of a heliocentric universe.

Back cover

Back cover


Planetary retrogression became easier to explain. Other hypotheses, like the steady state universe and Kepler’s planetary Platonic solids, haven’t proved successful, but data don’t explain themselves and astronomers have to be adventurous in mind, if not usually in body. This book contains the big names, the big sights and the big mysteries that are still awaiting explanation. More big names, sights and mysteries are on their way.

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