A short history of the universe

By David Malin and Fred Watson 1 June 2011
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Leading astronomers David Malin and Fred Watson explain the Big Bang through to the edge of our knowledge.

As a species, we’ve been looking at – and wondering about – the night sky and other aspects of the natural world for a million years or more. Our western stories of the sublime, everlasting perfection of heaven and (from watching volcanoes) the eternal damnation of hell probably arose in this way. Humans are both blessed and blighted with an almost insatiable curiosity and a need to know why things are as they are – it’s what makes us human – and there’s nothing more puzzling than our experience of the night sky.

Looking up at night is one of the most subtle and profound experiences, and it’s freely available all over the world (except on cloudy nights and when a good show is on the telly). Any culture with a dark sky and a little curiosity will have a story describing the forces that move the Sun and Moon across the sky. The broad arch of the Milky Way appears as the Rainbow Serpent, and the journey from day into night is celestial Yin and Yang. Those legends that survive have a richness and variety that celebrate human imagination. A good deal of sky lore has been lost, which is a pity, since it reveals much about the cultures from which it sprang.

A common theme is that the daily, monthly and yearly cycles of Sun, Moon and stars were somehow centred on the Earth, and that we are thus the centre of creation. But there’s good evidence, in the alignment of structures such as Stonehenge and the Pyramids, that careful watchers of the sky had centuries ago uncovered many subtle patterns of change that suggested a different interpretation. Even if the cycles were not understood, they were predictable, and this predictability led to the growth of mathe-matics, the basis of the sciences, and to astronomy, which itself gradually emerged from the non-science of astrology.

Almost all of these measurements concerned the solar system, either the motions of the Sun, Moon and planets, or the rotation and motion of the Earth itself, using the so-called fixed stars as a reference frame. Observations were made with the naked eye, often assisted with increasingly sophisticated instruments for accurately measuring angular distances and time.

Moving the centre of the universe

As the renaissance spread through Europe in the 16th century, and as the technology of astronomical instrumentation rapidly improved, it became clear that some ancient astronomical ideas were simply wrong, especially the notion of the Earth-centred universe. This is normally attributed to Ptolemy (about 150 AD), aided and abetted by the great authority of Aristotle (around 350 BCE) but is certainly much older. Its best remembered antagonist was the rather colourless Polish astronomer and cleric Nicolaus Copernicus (1473-1543) but he was by no means the first to suggest the Sun as the centre of the solar system. Copernicus’ heliocentric views were based on philosophical and aesthetic arguments rather than observation and were not widely accepted in his lifetime. The idea was influential, however, most notably with the Catholic Church, which thought it heretical because it displaced the Earth as the centre of God’s creation.

Almost 60 years after the death of Copernicus, the Florentine professor of mathematics and astronomy, Galileo Galilei (1564-1642) found himself questioning the accepted Aristotelian wisdom while studying at the University of Pisa (and later at Padua) in northern Italy. In contrast to Copernicus, Galileo was ambitious and well aware of the value of publicity. And he was not simply a theorist. He experimented with pendulums, hydraulic pumps, thermometry (the measurement of temperature) and the magnetic compass, as well as ways to test Aristotle’s descriptions of how objects fall under gravity, allegedly using the famous leaning tower as a very public drop site. He was also a musician and familiar with such exciting new concepts as perspective drawing and was in occasional demand as an art critic.

In May of 1609, Galileo heard about the invention of an optical tube said to make distant objects appear closer. Within a month he had made his first telescope and was soon aware of the military and economic value to a major seafaring city-state such as nearby Venice of a device that was able to identify distant ships. By August 1609 he had demonstrated the new instrument to the Venetian Senate, which was suitably impressed and rewarded him with a permanent position at the university of Padua (and a higher salary). In November of that year Galileo first records turning the telescope to the night sky. What he saw there astounded him. He sketched and quickly published in a small book, Sidereus Nuncius (The Starry Messenger), “unfolding great and marvellous sights” – some of which challenged the accepted wisdom of Aristotle, which had stood for almost two millennia.

The Starry Messenger’s fate

Galileo’s first notes described the appearance of the Moon and were accompanied by wash drawings of what he had seen over several weeks in November and December 1609. Nowadays this seems easy enough, but the lenses in Galileo’s telescope were far from perfect and the instrument had a field of view much smaller than the Moon’s disk, so his sketches are the result of many painstaking observations with a hand-held telescope following a moving target. They show the accomplished hand of an artist, with the peaks and depressions highlighted where sunlight meets shadow, and delicate gradations of grey across the surface. These are not artists’ impressions; however, they are a scientific record of “lofty mountains and deep valleys…vast protruberances, deep chasms and sinuosities…” revealed as the Moon waxes and wanes. Galileo was captivated by a previously unseen shadow play on a distant world.

Galileo was not the first person to turn a telescope towards the Moon, nor the first to make drawings of it. Some months before, in mid-1609, and later in 1610, the English astronomer and mathematician Thomas Harriot (1560-1621) had made some simple sketches of the Moon. But, these are neither as revealing nor as appealing as Galileo’s renditions. More important still, they weren’t published until long after Harriot died.

The publication of his Moon sketches and other discoveries in Sidereus Nuncius in March 1610 saw Galileo’s reputation reach far beyond Venice and Padua. The book was an immediate bestseller and a second edition was -published in Frankfurt, Germany, within months. Its pages contained descriptions and illustrations of other astonishing discoveries, among them a series of drawings of the changing orbits of Jupiter’s moons; sunspots, which showed the Sun’s rotation, and its imperfection; Saturn, a planet with an inexplicable shape; the Milky Way, seen as a collection of stars for the first time; the phases of Venus; and, of course, the craters, mountains and valleys on the Moon.

“I render infinite thanks to God,” wrote Galileo after his nights at the eyepiece, “for being so kind as to make me alone the first observer of marvels kept hidden in obscurity for all previous centuries.” Galileo’s little book shook the accepted view of the universe and humankind’s place within it to its foundations. He showed how a simple piece of technology combined with careful observations and striking illustrations could revolutionise the way science was done and explained to a wider public. But the wider public included influential sceptics, among them his former patrons in the Catholic Church. After many years of compromise and confrontation for his support of the Copernican system, in 1633 he was found guilty of heresy by the Holy Inquisition and condemned to house arrest for the rest of his life. Blindness eventually overtook him, perhaps a legacy of looking at the Sun through a telescope, and he died in 1642. Galileo extended human vision to the stars and beyond, replacing dogma and belief with the knowledge and understanding that underpins modern science.

Almost all the objects Galileo studied were very bright. Of course, he only had a 12mm telescope – a small-aperture instrument by any standard. But even when much larger telescopes were built, the limitations of the human eye hindered astronomical progress. Despite this, in 1705 Edmund Halley calculated the orbit of the comet named for him and in 1781 Uranus, the first new planet since ancient times to be discovered, was spotted by William Herschel, who, with his son John, also explored the Milky Way.

New lines were seen in the spectrum of the Sun, signalling the beginning of astrophysics, and measurements of the transit of Venus across the face of the Sun revealed the size of the solar system. Eventually even the distances to the nearest stars were measured – all of it valuable progress, made by diligent and persistent observers. After Galileo’s telescope, it was to be almost 230 years before another, similarly momentous technical advance would displace the human eye from the telescope and open up a completely new era of astronomy.

Astronomy, more than meets the eye

Lous Daguerre’s discovery of photography was first announced to the public in Paris in 1839 and it created quite a stir; the artist Paul Delaroche declared “from today, painting is dead!” The announcement itself was made by the astronomer François Arago, who wrote that photography would “accelerate the progress of one of the sciences [astronomy] which most honours the human spirit”.

However, Daguerre’s process and its immediate successors were tricky to use and not sensitive enough for capturing faint light, so it wasn’t until the 1880s that photography advanced enough to be used to photograph the stars. In South Africa, David Gill photographed the Great Comet of 1882 with a portrait camera and was impressed with the vast numbers of stars that appeared on the plate.

A few months later, Ainslee Common photographed the Orion Nebula (one of the brightest star-forming nebulae – a glowing interstellar cloud of dust and gas) with his homemade reflector and a 30-minute exposure from his garden in Ealing, near London. He was just as surprised as Gill to see faint stars on the photograph that had never been seen by eye, even with much bigger telescopes. Common’s picture of Orion showed that photography was much more than a recorder of visible light, it was a detector of the unseen.

Common won the Gold Medal of the Royal Astronomical Society for his work, and Gill championed an enormous international photographic sky-mapping project (the Carte du Ciel or “Map of the Sky”) that began in 1887 and lasted 100 years. As with Galileo, it was the power of images that enthused astronomers.

Though photography was by now much more convenient to use, it was not easily adapted to the telescopes of the day. Its ability to capture faint light was obvious however, and quickly drove telescope design in new directions. Apart from conventional stellar images, photography was soon harnessed to the spectrograph, to capture information about the composition, distance and velocity of the stars, and it was used to measure their colour and brightness. These data are the bread and butter of astrophysics, which flourished after 1890.

Just after World War I, photography was used to confirm that gravity could bend light, the first solid evidence of Einstein’s then-controversial General Theory of Relativity. The result made Einstein famous, and a headline in London’s Times on 17 November, 1919, which proclaimed a “Revolution in Science: New Theory of the Universe”, was typical. A decade later and with bigger and better telescopes came photographic spectra of variable stars, yielding the first extragalactic distances (to the Magellanic Clouds, two dwarf galaxies that are members of our Local Group of galaxies).

By the 1930s, spectra of much more distant galaxies showed that the universe was expanding, and by the 1940s, the dimensions and stellar composition of the Milky Way itself was well understood, as was our peripheral location within it. Almost all the observational data for these major discoveries were gathered on photographic plates, and black-and-white pictures of graceful galaxies, intriguing clouds of dust and spectacular star-forming regions began to appear in popular books and magazines.

Starstruck about astronomy

In 1930, Bernard Schmidt, an eccentric Estonian-German optical genius, invented a revolutionary type of super-efficient camera-telescope for astronomy that allowed wide-field, pin-sharp photographs to be made. Despite the loss of an arm in childhood, he fine-tuned the complicated optics himself. The first colour pictures of space were taken atop Palomar Mountain in California in 1958, using a Schmidt camera – almost identical to the UK Schmidt telescope at the Anglo-Australian Observatory (AAO) at Coonabarabran, in north-western NSW.

From this point on, telescopes became far more sophisticated; what began as a device to put your eye to has evolved into a pure imaging machine – it’s not possible to look through most professional telescopes today. Some, such as the Hubble Space Telescope, capture images from Earth’s orbit. While colour photographs are not essential for the science of astronomy, they’ve made astronomy accessible to a much wider audience. As with Galileo, the first truly scientific stargazer, modern astronomers recognise that their star stories – which reveal a universe bigger, grander, much more beautiful and more mysterious than anyone imagined – are more interesting if they’re well illustrated.

While Galileo’s observations confirmed his belief in the Copernican idea of a sun-centred solar system, they also hinted at multitudes of distant stars in the Milky Way for which he had no explanation. Every stage in the progress of astronomy since the time of Galileo has produced similar mysteries, only to be followed by a technological advance that allowed new understanding. Some puzzles, such as the age of the universe, endured until quite recently, while others, such as the nature of the energy that powers the stars, were resolved more than 50 years ago. Some, such as the intriguing nature of dark matter, are still an enigma.