THERE is an awful lot of it about but what it is remains the "most profound mystery in science", says the man who gave it its name: dark energy.

This weird, invisible force that is pushing the galaxies apart at a faster and faster rate accounts for almost three-quarters of the universe, the University of Chicago cosmologist Michael Turner said yesterday.

"It's very different than anything else we know," Professor Turner, who was attending a conference in Canberra, said. "Until we understand what dark energy is, we don't understand the destiny of the universe."

The mystery is no surprise. The existence of dark energy was revealed 11 years ago by two teams, one led by the Australian astronomer Brian Schmidt, who discovered the expansion of the universe was accelerating.

Australian astronomers are also now leading the way in throwing light on this dark side of the cosmos.

The director of the Anglo-Australian Observatory, Matthew Colless, said his team was measuring the position of 200,000 distant galaxies, and seeking tiny "wiggles" in their distribution.

These features will have been influenced by dark energy when it began to become dominant over the pull of gravity, about 8 billion years ago.

First results were expected soon and could provide "vital clues" about the nature of the strange force, Professor Colless said.

Yesterday astronomers using the Hubble Space Telescope released the most accurate measurement so far of the expansion rate of the universe, based on observations of pulsating stars and recent exploding stars, called type 1a supernovas.

Adam Reiss, of Johns Hopkins University, said his team's results narrowed the possibilities for dark energy.

They supported the simplest idea about the repulsive force: that it was very similar to the cosmological constant Albert Einstein proposed a century ago to explain why the universe did not collapse under the pull of gravity.

Professor Turner said dark energy had some remarkable characteristics.

"It seems to be smoothly distributed throughout the universe," he said.

"The feature that gives it repulsive gravity is that it is extraordinarily elastic. It wants to scrunch up."

Professor Schmidt, of the Australian National University, said the cosmic acceleration meant "the universe is slowly fading away on us".

The new value for the expansion rate of the universe is 74.2 kilometres per second per megaparsec (a megaparsec is about 3 million light years).

It is thought about 4 per cent of the universe is visible matter, about 23 per cent is dark matter, and 73 per cent is dark energy.

I love thinking about the large-scale structure of the universe