A slightly adapted version of a review I wrote for the Wall Street Journal:
Eyes on the Sky
Eyes on the Sky is an intriguing and unusual book. Popular books about astronomy usually focus on the wonders of the Universe – black holes, quasars, the Big Bang, and so on. But radio astronomer Francis Graham-Smith focuses on the terrestrial wonders that have revealed these exciting objects – the telescopes. Not just optical telescopes, but telescopes peering out at he Universe across all the wave bands of the electromagnetic spectrum, from radio waves to gamma rays. The story begins with Galileo, who first turned a telescope upwards almost exactly four hundred years ago, and ends with the radio telescopes that combine observations made by different antennae at widely spaced locations to mimic a dish the size of the Earth. But the author could not have been aware when he wrote the book how neatly this story rounds off an era in astronomy, since as of the fall of 2015 we have a completely new way of looking at the Universe, using gravitational waves, not electromagnetic radiation.
This book-ending is particularly appropriate, since Graham-Smith was one of the pioneers of radio astronomy who opened up the new investigation of the sky in the 1940s, using radar technology developed during World War Two. As he says, before 1947 “the only real astronomers were those who actually looked through [optical] telescopes”. Radio astronomy was the first of a clutch of new techniques which opened up new windows on the Universe. And it has all happened within a single human lifetime.
The approach of the book is both thematic and historical. The themes address each part of the spectrum, starting with Galileo and “conventional” telescopes then moving on to ultraviolet, infrared, X-ray and gamma ray astronomy, before winding up with Graham-Smith’s real love, radio astronomy. Within each theme he covers developments historically, including developments such as the use of rockets, satellites and high-altitude balloons to make observations at wavelengths blocked by the Earth’s atmosphere. The techniques have developed as much as the technology – interferometry and aperture synthesis, the methods used to make a virtual giant telescope out of an array of smaller instruments, are explained as clearly here as anywhere you are likely to find. But the real fascination of the book is the way it almost incidentally highlights the way science has changed in little more than fifty years. Galileo might have been amazed by the technology, but he would surely have understood the principles on which the 200-inch Hale telescope on Mount Palomar, the biggest one around in 1947, operated. But how could he have comprehended the significance of a satellite such as Planck, an observatory orbiting the Earth in order to measure the strength of radio waves from the dawn of time? Come to that, very few astronomers in 1947 would have taken the idea of such a satellite seriously.
Astronomers of 1947 would also have been astonished at the size of present day astronomical projects, both in terms of the physical dimensions of the equipment involved and the number of people – and nations — collaborating on the observations. The latest radio telescope to come online is the Five Hundred Metre Aperture Spherical Telescope (known as FAST), in Guizhou Province, southwest China. As the name suggests, it is a dish 500 metres across (for comparison, the famous Arecibo radio telescope that featured in the movie Contact is 1,000 feet, or just over 300 metres, across). But the dish of FAST is made up of 4,600 separate triangular panels, connected by flexible joints and a network of steel cables to 2,300 computer-controlled electric motors, which continually adjust the exact angle of each panel to in effect tilt the dish to track objects across the sky as the Earth rotates. The accuracy of this “active surface” keeps each triangle positioned to an accuracy of five millimetres.
The international nature of astronomy is highlighted by a telescope known (for obscure reasons; astronomers love acronyms) as VISTA. This has a mirror 4 metres across and is located at the European Southern Observatory, on a mountain top in Chile. The mirror was designed in the UK, cast in Germany, and smoothed to its precise shape in Russia, before being shipped to South America, where it is now used by astronomers of many nations; there are fifteen member states of ESO. Not that anyone “looks through” such a telescope; it captures light onto an array of Charge Coupled Devices (CCDs) — sixteen arrays each 2,048 by 2,048 pixels across, making a total of some 67 million pixels. The resulting images appear on monitor screens, or the data is sucked off by a computer for detailed analysis.
Since the time of Galileo, Graham-Smith points out, the light collecting area of individual telescopes has increased by a factor of more than half a million, while over the past fifty years there has also been a dramatic increase in the performance of detectors, such as CCDs. And as he emphasises, progress has not yet come to a halt. Where next? Well, we now have the ability to image planets orbiting other stars. The next generation of telescopes may be able to detect signs of life on those planets.