* Astronomy

While North Korea was testing a nuclear bomb, France was verifying its nuclear arms, too - with a battalion of soundless, black, cabinet-sized calculators buried beneath a meadow.
The world's established nuclear powers have for the past decade foregone real test blasts for the onscreen kind, harnessing the world's most powerful computers to simulate as best as possible what happens when a nuclear bomb explodes.
So why should any nation test-blast weapons anymore if supersimulators can do the job? Because, nuclear experts say, it has turned out to be tougher than most people thought to mimic the "real thing."
Scientists working in this secretive compound at Bruyeres-le-Chatel, south of Paris, are still several years away from being able to replicate nuclear fusion, or trying out a new bomb design without detonating it. Their American counterparts are only slightly closer, despite billions of dollars spent on supercalculators and superlasers.
At the heart of France's program to test its 300 or so warheads is the Tera-10 supercomputer, capable of 50 teraflops, or 50 trillion calculations, per second.
These supercomputers can predict parts of a nuclear blast. To complete the picture, France and the United States are looking to superlasers to create fusion ignition - which is what happens when a hydrogen bomb explodes.
The U.S. government has put 15 years and $3 billion into its National Ignition Facility, but is now saying it has no guarantees that it will be able to produce fusion after all.
Both the NIF and the French Laser Megajoule project are estimated to go on line in 2009, though the dates have been repeatedly pushed back.