Scientists are preparing to answer two of the universe's most baffling questions: why are beaches sandy and why do humans covet gold?

These may not seem fundamental issues but they confront a serious scientific problem. How did the elements from which our bodies and planet are made come into existence? And why are some more common than others?

Astronomers know the cosmos is mostly made up of hydrogen and helium, created at the Big Bang 15 billion years ago. The remaining 1 per cent - oxygen, silicon, gold and all the other elements are stardust.

This dust was 'cooked', out of hydrogen, in the centres of stars and was then spewed into space, where it eventually coalesced into Earth, other planets and eventually living beings, including Homo sapiens - hence Joni Mitchell's lines from Woodstock: 'We are stardust, billion-year-old-carbon...'

But although scientists understand the broad principles, they have yet to fathom some of the mechanisms involved. Researchers at Cern, the European centre for particle physics in Geneva, last week launched an experiment in which a specially tuned laser beam called Isolde will blast targets of different materials. The aim is to create elements as they were first formed inside stars.

Project leader Dr. David Lunney explained: 'We are going to create elements and then learn how constituents of our universe were made.'

The basic process of element formation is called fusion. Under intense pressures and temperatures that are found inside stars, hydrogen and helium atoms combine to form heavier elements. Relatively light elements, such as silicon and oxygen, are produced in this way. These two elements sometimes combine to form silicates, grains of sand which scientists have recently detected orbiting stars. Space is a beach, in other words.

But heavier elements - such as gold and silver - cannot be made this way, scientists realise. They would break back down into lighter elements as they were being formed inside stars. So only a special mechanism can explain their creation.

That mechanism occurs in large stars when fusion runs out of control. Layers of different elements are created in a spiral of increasing ferocity until a star explodes with fantastic force. This is a supernova, one of the most explosive events in the universe.

In a few seconds, as much energy as the sun could radiate in 9 billion years is released into space, creating a furnace thick with neutrons. These highly energetic particles crash into the various elements as they pour from the star, creating a soup of even denser, heavier elements which then decay into gold, silver and other allums. Space is seeded with precious metals.

At least that is the theory that most astronomers accept. 'The trouble is that this theory makes a lot of assumptions and is based on parameters that have not been properly tested,' said Lunney.

'To find out where dense neutron-rich atoms were made we need to find out how they were made. Then we will be able to calculate how these atoms would have behaved and find out if supernovae were indeed the crucibles in which the elements were first manufactured. We shall do this over the next five years.'

Supernovae are very rare events, as UK astronomer Dr. Paul Murdin points out. 'That is why we use sand as a building material and treasure gold for its rarity. The former is made of light elements and so are relatively common. Gold is shiny, heavy and rare, so we covet it.'