Sunday, August 6, 2017
Churchill's Bomb: How the United States Overtook Britain in the First Nuclear Arms Race 1st Edition by Graham Farmelo, Basic Books
Ripples in Spacetime by Govert Schilling review – a new window on the universe
Long before homo sapiens was up on its hind legs, two black holes – each more massive than two dozen suns – were swirling around each other in outer space at a colossal rate. They merged with such violence that the very fabric of space and time shook, the ripples spreading out across the universe.
A little more than a billion years later, in the early hours of 14 September 2015, some of those ripples were detected by scientists in the US. By any standards, this was a truly remarkable achievement. The astronomers had managed to identify a disturbance that had lasted only 20 milliseconds – much briefer than the blink of an eye – and was smaller than a millionth of the width of an atom. They had found the first direct evidence of gravitational waves, a feat likely to be rewarded soon with a Nobel prize.
In Ripples in Spacetime, the Dutch astronomy journalist Govert Schilling gives us a lively and readable account of the waves’ discovery. They had first appeared in the mind of Albert Einstein almost a century before, after he deduced their existence from his new theory of gravity. For reasons that Schilling does not make entirely clear, Einstein twice doubted that the waves existed but was eventually convinced that they should be part of nature’s fabric.
Einstein apparently did not spend much time contemplating the possibility of discerning these waves. This was probably because, according to his theory, they interact so feebly with ordinary matter that they would be almost certainly impossible to detect in the foreseeable future. Theorists later calculated that it might just be possible to detect them, presumably emitted in the aftermath of violent collisions between massive, compact objects in outer space. Schilling spends a good deal of time making sure that we understand all this. “Buckle up for a crash course in astrophysics,” he tells us, before delivering a clear, pacy narrative.
Astronomers detected a disturbance that was smaller than a millionth of the width of an atom
All great scientific discoveries open up new lines of research, and pose more questions than answers. This one is no different. Schilling underlines that this discovery is the opening of a new window on the universe, the beginning of a new branch of science. Astronomers will no longer be limited to observing space through the waves of electricity and magnetism (for example, visible light) entering telescopes, but will be able to observe it through waves of gravity. Galileo would have been amazed.
The design of the huge apparatus that first detected the waves exploits the fact that when the waves pass through, its dimensions are minutely altered. The change is much too small to see directly, even using the most powerful microscope. Calculations showed, however, that it should be possible to measure the change by exploiting the extremely subtle interference between beams of light from lasers. Hence the acronym Ligo, short for Laser Interferometer Gravitational-wave Observatory.
The Ligo authorities built two identical observatories, one in Hanford, Washington State, in the US, and the other over 3,000km away, in Livingston, Louisiana. This doubling-up enabled experimenters at the observatories to check each other’s results – if only one of them appeared to detect the waves, no one would have believed it. As Ligo’s director later said, it was “truly a scientific moonshot”.
Plans for detecting gravitational waves began to take shape in 1960, five years after Einstein’s death. Several scientists contributed innovative ideas, but, according to Schilling, Ligo was the brainchild of three scientists: the Scot Ronald Drever, and the Americans Kip Thorne and Rainer Weiss. The US National Science Foundation bankrolled the enterprise, conceived, built and operated by the California Institute of Technology and the Massachusetts Institute of Technology. Valuable contributions were made by a few other leading academic institutions (some in the UK), but most kept their distance, deeming the project too speculative.
Schilling expertly guides us through the development of the venture, highlighting the personal clashes and technical problems that put it in jeopardy. By the early 1990s, it was in deep trouble. The brilliantly inventive Drever was thrown off the team and even found himself locked out of his office. Two years later, the project’s principal investigator was replaced by the experienced experimentalist Barry Barish, who put it back on the rails. He later described the authorities’ agreement to continue to fund it after 1994, despite an alarming hike in the budget, as “a miracle”.
Schilling expertly guides us through the venture, showing the personal clashes and problems that put it in jeopardy
By 2015, about 1,000 scientists and engineers were working on the project, which had racked up a cost of more than $1bn. But it was suddenly all worth it. Astronomers detected a tiny disturbance that clearly signalled the discovery of gravitational waves, emitted by merging black holes exactly as Einstein’s theory had predicted. The gravitational waves emitted in this single collision had a power that was much greater than the output of all the stars in the universe combined.
The Ligo officials announced the discovery almost five months later. The science had to be watertight. A few years before, astronomers working on another project had rushed to announce the sensational discovery of gravitational waves formed early in the universe, but the evidence – splashed across front pages all over the world – turned out to be a handful of dust.
In decades to come, Ligo and other detectors will be able to monitor bursts of gravitational waves with ever-increasing precision. The team has already detected them from a few other black hole mergers, and waves emitted from mergers between these and other exotic cosmic objects are expected to be commonplace in the near future.
Yet all this depends on maintaining adequate funding for basic research. One of the heroes of Schillings’s story is an institution – the US’s farsighted and patient National Science Foundation. If the gravity waves discovery is awarded the Nobel prize in physics on 3 October, it will be interesting to see whether it will, in keeping with tradition, be shared among a maximum of three scientists. That would seem invidious: it is time the Nobel authorities awarded the credit for such successful big-science projects to an entire team.