The Perception of Ancient Light Beyond Visibility

David Malin Anglo-Australian Observatory and RMIT University

The human eye is the only way by which we can appreciate the subtle majesty of the night sky; but it needs time to adjust to the spectacle. The natural progression of twilight runs at about the right pace, allowing the eye to adapt to the dark. But who nowadays has the time to sit beneath the sky from sunset until the faintest stars appear, an hour or so later? Our ancient ancestors did; they had no choice. Apart from the campfire there was no artificial light at night, so every cloudless evening the stars would be there to be admired. And they would gaze at them wide-eyed, not only out of wonder, but because in the dark the eye's black pupil expands to fill the coloured iris, admitting more light. "These lovely lamps, these windows of the soul", wrote the 16th-century poet Guillaume de Salluste (1544-90) of the eyes.

We have not evolved to admire the stars; their beauty enhances our lives and piques our curiosity, but it has no survival value. However, dark adaptation became essential for a species that both hunts and is hunted. It was so important that during twilight, the eye evolved to abandon its sense of colour and fine detail in darkness, replacing it with increased sensitivity to monochrome.

A moonlit landscape is almost a million times fainter than when the Sun shines on it. But beneath the Moon we see our world only in varieties of grey. The sky is blue and the grass is green, but by moonlight all we see is shade and texture.

Our appreciation of the number, colour and beauty of stars is thus limited by the size of the pupil of the eye. Or it was. When the telescope was first invented its most obvious feature was its ability to make merchant ships and military forces seem clearer and closer. Galileo showed that its real advantage was in expanding human vision - literally - by increasing the effective size of the pupil of the eye. The front lens of Galileo's first, simple telescope was about 12 millimetres in diameter, about twice as wide as the pupil of the dark-adapted eye, and capable of collecting four times as much light. This, and the modest magnification of his telescope, is why Galileo was able to see further and fainter than anyone before him. It took a while for this to be understood, but when it was, the front lenses of astronomical telescopes became ever larger and were eventually substituted by curved mirrors, which could be made bigger still. But even with these lenses, the eye continued to have its problems. To observe effectively it had to be dark adapted, which takes many minutes. To make drawings some light was needed, so a candle was lit, destroying dark adaptation, which had to be recovered so that the now-invisible drawing could be checked against what was seen in the telescope. Observing was a slow and tedious business. Which brings us to the second revolutionary technology that changed our perception of the world. A practical system of photography was invented in 1839. But it would take 40 years before the technology had improved enough for night-time astronomy. The breakthrough came in 1883, when for the first time stars too faint to be seen by eye were photographed using a telescope. Photography had been transformed from largely a recorder of the everyday world into a detector of an unseen and unseeable universe.

Traditional photography is no longer used in astronomy, having been displaced by digital technology; the true-colour photographs in this exhibition are among the last to be made using traditional processes. The images aim to emphasise the vast multitudes of stars that Galileo barely glimpsed, and between them the dark clouds of dust that arise from the stars themselves and permeate the Milky Way Planet Earth and we ourselves are made from this Stardust. If the stars had never existed, neither would we. From the artist's perspective these photographs are of interest because they show shapes, textures and colours that are true to nature and yet have never been seen. They reveal a part of the natural world that is beyond unaided vision, yet is entirely real and relevant to our existence. Even more remarkable is the idea that the light captured by the photographic plate is ancient light. It has been travelling for thousands, sometimes millions of years across space and time. It shows us what was, not what is.

Reproduced with the permission of the author and MGA