Sunday Times, 14 February 2016
The week’s news was dominated by two faces. There were the increasingly worn features of John Kerry, US Secretary of State, announcing in Munich “a partial ceasefire” in Syria, a deal in which neither he nor anybody else really believed. In Washington DC, meanwhile, there was, in front of the Stars and Stripes, the smiling face of physicist David Reitze as he announced with dramatic pauses, “We… have… detected… gravitational… waves.”
In the abyss between the two announcements lay all of human history. On one side the unresolvable bitterness, futility and tragedy of conflict; on the other the astounding capacity of the human mind to look, whether in science and art, far beyond the narrow cage in which it is confined.
Reitze’s announcement had an exact predecessor. In 1919 the great astronomer Arthur Eddington returned from the African coastal island of Principe to announce to the Royal Society that he had observed the curvature of starlight round the sun during an eclipse. Both announcements provided experimental confirmation of Einstein’s General Theory of Relativity, published in 1915. And both were overshadowed by war.
Such precise and momentous confirmations are rare in physics. The subject now reaches so far outward into the cosmic immensity and so far inward into the subatomic realm that any attempt to confirm theory tends to be both expensive and massive. It took, for example, the 27 kilometre circumference of the mighty Large Hadron Collider to detect the infinitesimally small and fleeting Higgs boson. Similarly it took two enormous L-shaped laser detectors, 2000 miles apart, to sense the gravitational waves from a black hole collision that happened a billion light years away (6000 trillion miles).
There are still big physics theories out there that defy experiment and may always do so. Confirmation of the theory of ‘superstrings’ as the fundamental constituents of matter, for example, remains, in spite of enormous efforts, almost impossible to imagine. And the ‘multiverse’ theory, which suggests that our universe is but one of billions, is hampered by the fact that, almost by definition, no other universes can be detected.
Some scientists have now concluded that many of their colleagues have lost touch with reality. In their book The Singular Universe and the Reality of Time, Lee Smolin and Roberto Magabeira Unger argued that scientists should stop tallking about “what might be the case”, after all there might be “giant angels and unicorns hovering just beyond our cosmological horizon”, and concentrate on what could be experimentally verified. Two physicists, George Ellis and Joe Silk, concluded in a recent paper that “theoretical physics risks becoming a no-man’s-land between mathematics, physics and philosophy that does not truly meet the requirements of any.”
So the glee accompanying this week’s announcement is understandable. But what, exactly, does it mean?
For the purposes of the next dinner party at which you are asked to define relativity in three and a half words, here’s the answer – it’s all geometry. Prior to Einstein we looked out at the night sky and saw the cosmos defined by Isaac Newton. The usual metaphor for this is the billiard table, astral bodies moving like the balls across a flat plane of universal time and unchanging space. Einstein, however, showed that cosmic geometry was in constant flux; the table was continuously warping as space and time, now indissolubly linked, were changed by motion and mass. Gravity emerged from this warping and a gravitational wave is the expanding ripple zone that ensues.
But gravity, surprisingy considering it’s what keeps your feet on the ground and orders the motion of the planets, is the weakest of the four fundamental forces known to physics. It is also the most elusive, so elusive that even Einstein began to doubt his own theory. He wrote a paper in 1935 denying the existence of gravitational waves. Fortunately for him – and somewhat astonishingly in view of his global fame – it was rejected for publication because an error was discovered in his calculations.
What was needed to discover gravitational waves was, first, fantastically accurate equipment, far beyond anything available to Einstein. These have included great deep frozen metallic beams or spheres that would deform slightly on the impact of a wave. But success came with the Laser Interferometer Gravitational Wave Observatory (LIGO) . This is able to measure a difference in length – the deformation caused by a wave – of less than one ten thousandth of the size of a proton.
Secondly, we also needed a cosmic event of unbelievable power. Such was the collision of two black holes, one 29 times the mass or our sun, the other 36 times. This impact was so cataclysmic that energy equivalent to the mass of three of our suns was released.
“For a very short amount of time, the actual power in gravitational waves was higher than all the light in the visible universe,” explained Peter Fritschel, LIGO’s chief detector scientist.
The ensuing gravitational waves travelled at the speed of light for a billion years until they encountered a species with the intellect to detect them. The smile on David Reitze’s face was a great moment of self-recognition in the 14 billion year history of our universe.
Perhaps you will now say that it changes nothing. Our daily lives will continue as before and innocent people will continue to die in pointless wars. The Russians will bomb Aleppo and their ambassador will barely be able to suppress a smile as he denies all knowledge.
Science, however, will move on. Think of gravitational waves in the same way you think of light or radio waves and you realise they offer new ways of seeing further and deeper into the universe. In 1964 the microwave background radiation of the universe, the heat signature of the Big Bang, was first detected. Gravitational waves offer the possibility that we may not just see but hear and feel that faint echo of creation’s inception.
“And if history is any guide,” the physicist Lawrence Krauss wrote of this latest discovery, “every time we have built new eyes to observe the universe, our understanding of ourselves and our place in it has been forever altered.”
Unfortunately such advances in understanding have never produced human improvement. We remain what we always were, creatures made of equal parts of war and wonder. All the more reason then, as John Kerry puts a brave face on an implausible peace, to be grateful that, in Oscar Wilde’s words, “some of us are looking at the stars”. And smiling.