The choice of the journal's editors
Last year it was Dolly the sheep clone. The year before it was the possibility of life on Mars. This year, astronomy once again heads the list of the most important scientific advances of 1998.
It concerns the accelerating Universe, the discovery that the galaxies of the cosmos are flying apart at ever faster speeds.
Each year, the leading journal Science selects those advances from the past 12 months that have changed the practice or interpretation of science or its implications for society. For 1998, the journal has put the accelerating Universe at the top of the list.
Two international teams of astronomers provided a glimpse into the destiny of the Universe when they looked at distant stars and found that they were rushing apart at an accelerating rate.
Scientists discovered decades ago that the Universe has been expanding since the Big Bang. But whether the gravitational pull between galaxies could slow, and ultimately reverse, that expansion has been unknown.
This year's discovery showed that the expansion of the Universe is in fact speeding up. This implies that gravity is no match for the force that is pushing the Universe outwards in all directions, and that the expansion may continue, perhaps forever.
Number two
The runner-up for most important advance of the year concerns work on the nature of circadian rhythms. Almost every organism on Earth keeps track of the 24-hour cycle between night and day using its "circadian clock", a built-in mechanism that researchers found out a lot about in 1998.
A quick succession of discoveries shed light on how the molecular "gears" driving the circadian clock respond to light and temperature cues and how they work together in different organisms. The results showed a surprising similarity between clock workings in organisms from bacteria to humans.
Remarkably, it appears that fruit flies and mice - separated by nearly 700 million years of evolution - share the same timekeeping proteins. Once again science has shown us how closely related is all life on Earth.
These developments may ultimately provide insight into overcoming jet lag and winter depression.
Best of the rest
The genetic information obtained may eventually allow researchers to break new ground in understanding the evolutionary relationships among organisms.
They were long thought to have no mass. This year an international team using the Super-Kamiokande neutrino detector in Japan claimed to have found evidence that neutrinos do have mass.
It is a discovery which, if it holds up, should prompt a rethinking of the prevailing theory of the forces and particles that make up the Universe.
Major microelectronics firms have now entered the biochip business after taking notice of this technology's potential.
It is a far cry from Star Trek's transporter but this achievement is key for creating quantum computers, ultra-powerful machines that will one day offer incredible computing speed and power.