91色情片

When the International Space Station goes into orbit, it will have an atomic
clock on board. But it won鈥檛 help the astronauts tell the time. The US National
Institute of Standards and Technology is developing a laser-cooled caesium
atomic clock that will exploit microgravity conditions to achieve accuracy 鈥渁t
least ten times better than any clock on Earth鈥�. The clock will enable
scientists to improve the performance of Global Positioning System satellites
and help the institute synchronise its clocks back on Earth.