Leading article: Not fade away

Perhaps it tells us something about the difference between art and science. Scientists have discovered that a bright yellow pigment used by Vincent Van Gogh in some of his most famous paintings turns brown in sunlight. They are trying to work out why as the first step in reversing the process.

And yet there is in art something which celebrates the transience of life rather than seeking to arrest it. Sometimes it is dictated by the medium: Giotto's frescoes are fading from exposure to light, even the greatest of Turner's watercolours is not fixed, and now it seems Van Gogh's yellow has been reacting with his pigmented white.

But the exquisite poignancy with which earthly pleasures slip through our mortal fingers has been one of the great human insights. The Buddha spoke of impermanence. The slave next to the general in the triumphal processions of ancient Rome whispered in his ear memento mori – remember you must die. The Dutch painters of the 17th century specialised in "vanitas", symbols of death and decay, like the skull and the morbid still life, or of fleeting evanescence, like soap bubbles or butterflies.

As for man, his days are like grass, he flourishes like a flower of the field; the wind blows over and it is gone. But don't expect science to give up quite so quickly.