When the first atomic clock was built?
Since the beginning of development in the 1950s, atomic clocks have been made based on the hyperfine (microwave) transitions in hydrogen-1, caesium-133, and rubidium-87. For decades, scientific-instrument companies such as Hewlett-Packard have been making caesium-beam clocks and hydrogen masers for entities like NIST and USNO, at prices rivalling those of cars.
In August 2004, NIST scientists demonstrated a chip-scaled atomic clock. According to the researchers, the clock was believed to be one-hundredth the size of any other. It was also claimed that it requires just 75 mW, making it suitable for battery-driven applic ...more