The 4% Universe: Dark matter, dark energy and the race to discover the rest of reality by Richard PanekTimes, 12 February 2011
For Galileo seeing was believing. When in 1609 he learnt of the Dutch invention of the telescope, he quickly constructed his own. With no reason to think there was anything to find, he searched the night sky and found that there was far more to the universe than meets the naked eye. He saw that the Moon had mountains, the Sun had spots and he observed the phases of Venus. With the discovery of Jupiter’s moons, Galileo found hard evidence that not all heavenly bodies revolved around the Earth. In March 1610 he published, The Starry Messenger, his report of what he had seen. All 500 copies were sold within a week.
Four centuries later Galileo’s successors know that they cannot see, even using their dazzlingly variety of modern telescopes, an astonishing 96 percent of the universe. The tiny fraction that is visible to their fine-tuned instruments is the stuff that we and all the countless planets, stars and galaxies are made from. Get rid of us and of everything else we’ve ever thought of as the universe, and very little would change. ‘We’re just a bit of pollution,’ one cosmologist says. We maybe irrelevant, but the rest of reality has been dubbed ‘dark’ and for the American science writer Richard Panek it ‘could go down in history as the ultimate semantic surrender’. For this is not ‘dark’ as in distant or invisible, but ‘dark’ as in unknown - for now at least.
Yet what is known is that almost a quarter of what can’t be seen is something called dark matter. Although its very nature is a mystery, its presence is discernible through its gravitational effect on the movement of galaxies. Without dark matter the astronomical data doesn’t make sense.
From a derelict iron mine in Minnesota to mountaintop observatories, at a pace that would shame many a thriller writer, Panek tells the story of the quest to unlock the secrets of dark matter and the particles that make it up. These weakly interacting massive particles, or WIMPs, have proven so elusive that the possibility that two were detected in November 2009 caused great excitement.
Dark matter is less than half the tale Panek wants to tell. For three quarters of the unknown universe consists of an even stranger substance called dark energy. Its existence was inferred, once again, from the circumstantial evidence gathered by astronomers measuring what could be seen. They didn’t need Sherlock Holmes to remind them that after eliminating the impossible, whatever remains, no matter how improbable, is the truth.
In the late 1990s two rival teams set out to collect data on distant supernovae in an attempt to determine the rate at which the universe was expanding. It was assumed that the pull of gravity would act as a break on the pace of expansion. To their disbelief they found that space-time was being pushed apart faster than ever before. Something was overwhelming the force of gravity to drive the expansion. Dark energy was winning the cosmic tug-of-war.
With a future Nobel prize at stake, disputes and arguments over who did what and when were inevitable. Parek provides a behind-the-scenes glimpse of science in the raw as alliances are forged and friendships strained. There is a new universe to explore and the latest experiments reveal it is 13.75 billion years old and made up of 72.8 per cent dark energy, 22.7 per cent dark matter and 4.5 per cent ordinary matter. These numbers are ‘an exquisitely precise accounting of the depths of our ignorance,’ says Panek. ‘It’s 1610 all over again.’
