The shining contraption honours one of history’s greatest clockmakers, John Harrison, the eighteenth-century pioneer of longitude, one of whose inventions was a ‘grasshopper escapement’. The Corpus clock’s maker and donor, John Taylor, was an undergraduate at Corpus in the 1950s and has since been a phenomenally successful inventor. He also has a passion for old clocks. Taylor chose to make his ‘grasshopper’ a fearsome, crusty giant locust. This beast, at once menacing, beautiful and whimsical, creeps inexorably along the top rim of the clock. It operates by putting its claws into the teeth of the great clockwork escape wheel that rotates around the outer edge of the clock face and, like Harrison’s grass-hopper, restrains and measures out the speed of rotation. This sinister monster is the ‘chronophage’ or ‘time eater’.10
When the Corpus clock strikes the hour it tolls off the numbers not with chimes but with a rattle made by shaking iron chains over a wooden coffin, with a hammer beating the wooden lid, all inside the back of the clock.
It seemed appropriate that Hawking should unveil this awesome device. Nearly everyone associates Stephen Hawking with the Big Bang and time’s ‘brief history’. He has tamed time by turning it into another space dimension. He has also seemed miraculously to have stretched out his own time – defying, perhaps, that horrific creature on top of the clock.
A quieter celebration
But time was indeed passing, even for Hawking. A year later, on 30 September 2009, obeying a dictum of the University of Cambridge that Lucasian Professors of Mathematics retire at the age of sixty-seven, he relinquished the title he had held for thirty years. His successor would be Michael Green, a distinguished theoretical physicist specializing in string theory.
In contrast to the celebration of Hawking’s sixtieth birthday, his stepping down as Lucasian Professor was marked quietly with a champagne reception in the department. His retirement meant little change. His busy schedule, his research, his status in the DAMTP stayed much the same. His title would now be Director of Research for the Cambridge Centre for Theoretical Cosmology. He kept his spacious corner office, and his personal assistant and graduate assistant were not ejected from the cluster of offices around him. In an audio message to BBC Newsnight, Hawking reiterated that he was not really retiring, merely changing titles, and added:
It has been a glorious time to be alive and doing research in theoretical physics. Our picture of the universe has changed a great deal in the last forty years, and I’m happy if I have made a small contribution. I want to share my excitement and enthusiasm. There’s nothing like the Eureka moment of discovering something that no one knew before. I won’t compare it to sex, but it lasts longer.11
For the past year, Hawking had been making threatening statements about the possibility of his leaving Cambridge and England – his way of protesting at the proposed draconian cuts in public funding for the kind of basic research he does and the kind of scientific education that he tries to inspire young people to choose. Funds were to be channelled instead into industrial applications of science, science that some thought would bring money into the UK. Hawking had been protesting about such priorities – calling them ‘ignorant of the past, and blind to the future’ – for over a decade. ‘To demand that research projects should all be industrially relevant is ridiculous. How many of the great discoveries of the past that laid the foundations for our modern technology were made through industrially motivated research? The answer is, hardly any.’12
If he moved, where would he go? Hawking had enjoyed working as a visitor at the Perimeter Institute for Theoretical Physics, a state-of-the-art research centre in Waterloo, Ontario, where Neil Turok was now Director. There were rumours that in retirement he would take up a post there. However, Hawking did not abandon Cambridge and probably never will. In spite of change of title, funding cuts, and inexorably deteriorating physical condition and ability to communicate his ideas, his goal remained as mind-bogglingly ambitious as ever: ‘A complete understanding of the universe, why it is as it is, and why it exists at all.’13 And how long was that going to take? In an interview on the Charlie Rose Show, the previous year, Hawking had been asked that question. He had replied by repeating the words he had used in 1980, in his inaugural lecture as Lucasian Professor: ‘by the end of the century’. Then he added with a cagey grin that though his estimate remained the same, there was a lot more of the twenty-first century left than there had been of the twentieth when he first made that prediction.
Hawking’s graduate assistant, Sam Blackburn, had set 2009 off with a literal bang by courageously giving him a mini-rocket-launcher for his birthday. With this ‘office toy’, he could send missiles sailing across the room. In March he had travelled to Los Angeles and met his granddaughter Rose for the first time. He and Lucy had dedicated the second of their ‘George’ books to her. Rose and her older brother George are children of Robert Hawking and his wife Katrina.
Hawking made another of his lecture stops in Pasadena, California. The frenzy of the occasion was not at all unusual for him. It was happening several times, sometimes even many times, every year, and even at Caltech, by then almost home territory.
Space, the Final Frontier
Heralded by the opening fanfare from Richard Strauss’s Also Sprach Zarathustra, he made his entrance to the convention centre, filled to capacity with 4,500 people. Those who didn’t know the music by that name still recognized it as the thundering background music of the film 2001: A Space Odyssey. Hawking could no longer use his hands to drive his own wheelchair, a sad change, but, hands folded in his lap, he was wheeled down the aisle at considerable speed. The Blue Danube Waltz – not quite so huge and impressive, more friendly – replaced Richard Strauss with Johann Strauss as he started up the ramp to the stage. The audience waited. Nothing happened for a little while. A glitch? A way of heightening expectation? Hawking’s graduate assistant came out and made some adjustments to Hawking’s laptop. Hawking’s hands remained immobile in his lap. He was controlling his computer with a movement of his cheek muscle. Soon came the voice and the words everyone was waiting for: ‘Can you hear me?’ The Caltech crowd cheered. Stephen Hawking was back!
Hawking’s lecture was ‘Why We Should Go into Space’,14 which he had written the previous year as a fiftieth-birthday present for NASA and delivered in Washington, DC. It was a more adult version of the chapter by that same title in the ‘User’s Guide to the Universe’ in George’s Cosmic Treasure Hunt, published in 2007. One part of the talk that he had not included in that book had to do with the cost of space travel, which Hawking admitted would not come cheap but would still represent only a small fraction of world GDP, even if the present USA national budget for space exploration were to be increased twenty times. He recommended a goal of a base on the moon by 2020 and a manned landing on Mars by 2025, not only in the interest of space exploration but to reignite public interest in space and science in general. ‘A high proportion of space scientists say their interest in science was sparked by watching the moon landings,’ he said.
Would we find life out there? Hawking was thinking that even if the probability is small of life appearing on a suitable planet, in a universe as large as ours, life must have appeared somewhere else besides Earth. The distances between the places where it has appeared were likely to be extremely large and the life would almost certainly not all be DNA-based. Another possibility is that meteors may have spread life from planet to planet and even from stellar system to stellar system. If life spread in this way (the process is called panspermia) then it would not be surprising to find other DNA-based life at locations in our own neck of the woods.
One bit of evidence that panspermia may have been the source of life on Earth, he pointed out, is that life here appeared suspiciously quickly after the first moment that it would have been possible. The Earth was formed 4.6 billion years ago and for the first half-billion years was too hot for life to emerge. The earliest evidence of life comes from 3.5 billion years ago. That mean
s life appeared only about a half a billion years after it was first possible. A long time, that might seem, but actually amazingly short.
We haven’t of course been visited by aliens (at least, we don’t think so – ‘Why should they appear only to cranks and weirdos?’) and there seem to be no advanced, intelligent beings near us in the galaxy. The SETI project has heard no alien TV quiz shows. There is probably no alien civilization at our stage of development within a few hundred light years of us. ‘Issuing an insurance policy against abduction by aliens seems a pretty safe bet.’
Hawking mentioned three possible reasons why we haven’t heard from any aliens.
First, the probability of life appearing on a suitable planet may be too low.
Second, even if that probability is high, the probability of this life evolving into intelligent life may be too low. (It isn’t clear that intelligence confers long-term survival advantage. Think of bacteria and insects.)
Third, intelligent beings who reach the stage of sending radio signals also have reached the stage of building nuclear bombs or similar weapons of mass destruction, and they may always destroy themselves very soon. Hawking calls that a sick joke, but he has also said that if extraterrestrial life has not destroyed itself, given the short time-span of life on Earth compared with the age of the universe, it is still unlikely that we would meet an example of alien life at a recognizably human stage. It would either be much more primitive than we are or so advanced that it would regard us as impossibly primitive.
Hawking favours the second possibility, the rarity not of life but of intelligent life. ‘Some would say it has yet to occur on earth.’ Why are we smiling?
Hawking’s lecture was long and thoughtful. He answered questions chosen ahead of time from those submitted by students and others in the Caltech community: how close are we to the Star Trek world? Don’t expect warp drive or replicators. We will have to ‘do it the hard way’, slower than light speed. To reach distant destinations we’ll need more than one generation. The journeys would be so long that the crews would even have time to evolve differently, so that the human race would divide into different species.
At the end of his visit to California, Hawking was not well enough to continue to Phoenix, as had been planned. Lucy appeared there instead and his pre-prepared lecture was broadcast over speakers. Back home in Cambridge, Hawking was in hospital for observation for a brief time, but all this turned out yet again to be only a temporary setback. He was back in fine form well ahead of an August trip to Washington, DC, to receive a Presidential Medal of Freedom from US President Barack Obama. In September, in Switzerland, where he visited CERN and the University of Geneva, his lecture ‘The Creation of the Universe’ filled one theatre and (by video link) ten other auditoriums.
It was his appearance in Washington to receive his medal that triggered a comment that unexpectedly drew him into the debate raging in the United States while President Obama was struggling to get a health care bill through Congress. One outspoken opponent of all public health care, disparaging the British system, commented that ‘If Stephen Hawking had been British, he’d be dead by now!’ Hawking responded that he was, of course, British and lived in Cambridge, England, and that ‘the National Health Service has taken great care of me for over forty years. I have received excellent medical attention in Britain. I believe in universal health care.’15 Jane Hawking might not have been so upbeat about the NHS, given her disappointments with them.
In February 2010, the Planetary Society of Pasadena, California, awarded Hawking the Cosmos Award for Outstanding Public Presentation of Science. Previous honorees had been James Cameron, creator of the film Avatar, and NOVA producer Paula Apsell.16 With Hawking’s health again uncertain, a delegation travelled from California to Cambridge to make the presentation. The society’s mission is ‘to inspire the people of Earth to explore other worlds, understand our own, and seek life elsewhere’. The press release announcing the presentation event in Cambridge ended with the words: ‘Tickets are sold out.’
Hawking unveiled another reminder of the swift passage of time in the spring of 2010. It was an unusual experience, having a garden named for him at the annual Royal Horticultural Society Chelsea Flower Show in London. The ‘Stephen Hawking Garden for Motor Neurone Disease: A Brief History of Time’ was dedicated not only to him but to all whose lives have been affected by motor neurone disease – patients, families, carers – and it was indeed a garden of mixed emotions. A spiral path representing the Earth’s plant history led visitors from an area with some of the most ancient species of plants and ended near the centre of the garden with ‘productive Mediterranean type plants that could produce food for us in the future, if climatic conditions allow’. At the centre of the garden was a pool in which water appeared to fall into a dark, hopeless vortex – representing a black hole – the end of time. Nearby, set into a drystone wall, was an antique clock, representing the swiftness with which time disappears for those with motor neurone disease. Queen Elizabeth met Hawking in the garden to admire the design, converse with him, and congratulate him.
Verdict from the Skies
WMAP ended its mission in 2009. A results summary in January 2010 announced that the large-scale temperature fluctuations in the CMBR are slightly more intense than the small-scale ones – a subtle but key prediction of many inflation models – and confirmed that the universe is indeed flat.17 This second conclusion was supported even more strongly than before by the overall randomness of locations of hot and cold points in the CMBR.18
As the WMAP mission was preparing to wind down,fn2 in May 2009 the European Space Agency launched its Planck satellite. Some of its detectors are designed to operate at a temperature of minus 273.05°C, just a tenth of a degree above absolute zero. A formal release of fully prepared CMBR images, analyses and scientific papers was not expected before 2013, but the ESA made a preliminary announcement of some results in January 2011. ‘We haven’t got to the real treasure yet, the cosmic microwave background itself,’19 said David Southwood, ESA Director of Science and Robotic Exploration. The project’s first goal had been to weed out some foreground sources that hamper studies of the CMBR. Many things may have affected this radiation during the evolution of the universe, ‘a whole lot of dirty astrophysics’20 complicating the picture – irregularities from gravitational lensing, radio sources, black holes, even instrument noise. The Planck scientists had in particular been focusing on the ‘anomalous microwave emission’, a glow associated with dense dusty regions of the galaxy, and been able to confirm that it comes from dust grains set spinning by collisions with either fast-moving atoms or ultraviolet light. Filtering out this microwave ‘fog’ from the data would not distort the CMBR. It would leave the CMBR untouched and allow Planck’s data to reveal the cosmic microwave background in unprecedented detail.21
As observations of the CMBR become more detailed and precise, it becomes more of a challenge for any model to agree with the findings. Success in hitting that target becomes more and more convincing evidence to support a model. Some models are winnowed out. But, so far, the agreement between observations and predictions having to do with the CMBR and the universe’s overall shape, large-scale smoothness, and smaller-scale structure look promising for inflationary cosmology.22 As John Barrow summed it up, ‘The growing observational evidence for the distinctive pattern of temperature variations in the microwave background radiation means that we take very seriously the idea that our visible portion of the universe underwent a surge of inflation in its very earliest stages.’23
Gravity waves from the moments right after the Big Bang are predicted to have left a distinct footprint in the CMBR,24 but this footprint was proving elusive. However, there are other potentially better ways to look for gravity waves. Kip Thorne, because of his abiding interest in black holes, has been working with colleagues for some time to develop instruments that can detect and measure more directly gravity waves that originate in black hole events, and in
the early universe. One technique is laser interferometry.
The interferometer is a device that splits a laser beam into two beams, perpendicular to one another. Each beam bounces off a mirror that sends it back along its path. The two beams are recombined when they meet. Each of the mirrors has a large mass attached to it, so if a gravity wave passes through the interferometer, stretching and contracting space between the masses (and hence the mirrors), that displaces them slightly and changes the distances the beams travel, producing interference patterns in the laser light (see Figure 19.1).
Figure 19.1. Sketch of an Earth-bound gravitational wave interferometer (by courtesy of Kip Thorne)
Earth-based gravity wave detectors are already in place in Hanford, Washington (LIGO); Hanover, Germany; and Pisa, Italy; but the grandmother of all such instruments, an astoundingly outsized arrangement, is scheduled to be launched into space in the form of three separate spacecraft, together known as LISA, the Laser Interferometer Space Antenna. Once in place, the three spacecraft will form a triangle with sides 5 million kilometres long. It will take approximately 20 seconds for light to travel between them. (See Figure 19.2.) When gravitational waves, stretching and squeezing space, pass through this enormous ‘apparatus’, their passage will alter slightly the distance between the spacecraft, and the distance travelled by the light beams between them, causing an interference of the light beams that can be measured with extremely sensitive instruments.25 LIGO and LISA were two of the instruments that Kip Thorne was talking about when he promised Hawking on his sixtieth birthday that gravitational wave detectors – LIGO, GEO, VIRGO and LISA – would test his ‘Golden-Age black-hole predictions’ well before his seventieth birthday.26 They had better get cracking!
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