International scientists celebrated the successful start of a huge particle-smashing machine on Wednesday aiming to recreate the conditions of the "Big Bang" that created the universe.
At a vast underground complex beneath the European Alps, physicists on Wednesday fired the first beam of sub-atomic particles down a 27-kilometre-long ring-shaped tunnel.
The debut of the machine that cost $US9 billion registered as a blip on a control room screen at CERN, the European Organisation for Nuclear Research, at about 9:30 am local time.
Scientists say experiments using the Large Hadron Collider, the biggest and most complex machine ever made, could revamp modern physics and unlock secrets about the universe and its origins.
The project has had to work hard to deny suggestions by some critics that the experiment could create tiny black holes of intense gravity that could suck in the whole planet.
Such fears, fanned by doomsday writers, have spurred huge interest in particle physics before the machine's start-up.
Leading scientists have dismissed such concerns as "nonsense."
The Large Hadron Collider is designed to smash sub-atomic particles into each other at velocities close to the speed of light.
Researchers believe this will recreate the conditions in the universe moments after the Big Bang and help them understand mass, gravity and a mysterious dark matter that is believed to hold the universe together.
The Big Bang is thought to have occurred 15 billion years ago when an unimaginably dense and hot object the size of a small coin exploded in a void, spewing out matter that expanded rapidly to create stars, planets and eventually life on Earth.
Problems with the collider's magnets caused its temperature, which is kept at minus 271.3Â°C, to fluctuate slightly, delaying efforts to send a particle beam in the counter-clockwise direction.