Originally posted by coquette
but the most accurate clocks today are "atomic" clocks that are based on RANDOM disintegrations! I tried to use that excuse for being late last week and it didn't work.
Actually not quite true. One of my jobs in the distant past was at NASA, Goddard Space Flight Center, working on the Apollo. You remember when we put a dozen people on the moon? We can't do it now
but anyway, I was on Apollo Tracking and Timing, the timing part was the atomic clocks used to co-ordinate changes from station to station around the world as tracking the craft could not be done by only one, considering we have this annoying planet in the way a lot of the time
We had a matrix of three clocks, in one big chassis, the primary, a cesium beam, the secondary a rhubidium beam, an alternate atomic clock technology but not as accurate as the cesium beam, then a third backup, a temperature compensated quartz clock, the precurser to todays watches but of course a hundred times more accurate. If you know about the National Bureau of Standards time hack transmissions on 5, 10, 15, and 20 Mhz short wave band, at the time they used 27 cesium beam clocks and the average of the timing pulses derived from them to make a clock much more accurate than any one cesium beam (there is a story about the first time they assembled the set, put them in a room together and found after a time, the clocks were somehow synchronizing to each other and all gave the same time hacks, they had to be separated into differant rooms so they could be separately tracked). So the time hacks on the shortwave bands were fed into our clocks, the hacks were exactly 8 cycles of a 1000 cycle tone, once per second. The reason we couldn't just use that directly was the transmission of the time hacks through radio waves meant they were smeared a bit in time due to reflections and refractions of the radio signal so they could not be counted on to arrive at any predictable time, but the hacks were used to set up the clocks to start them up, a rough time hack! But at the time, even the cesium beam clock had already been superceeded by the hydrogen beam clock. The cesium beam clock was accurate to about one second in several thousand years, plenty good enough to co-ordinate digital transmission of signals to the Apollo and to allow accurate switching between tracking stations, they had only a 100 nanosecond window to switch and maintain sync to the spacecraft. But the hydrogen beam clock, even in 1970 was a thousand times as accurate as the cesium beam, it fed a certain hyperfine line of hydrogen ionization into a cavity about 3 feet high and a foot across, which was designed to be a resonant cavity at about 9.8 Gigahertz, that frequency was then counted down and used as a clock much more accurate than Cesium. The most accurate clock now is based on photonics, and is very small, the size of a sugar cube, using a single ion of mercury in one version and another molecule, I forget which one right now, in another assembly that oscillates at optical frequency. Remember, the hydrogen beam clock oscillates at 9.8 gigahertz, 9800 megahertz. Well the optical frequencies, for instance, I work in photonics now and we use IR frequency bands of around 1550 Nanometer wavelength, that turns out to be a frequency of 193 TERAhertz or 193,000 Gigahertz or 193,000,000 megahertz. The higher you can get a clock to oscillate, the more accurate it becomes so you can see right away it is a thousand times as accurate as even the hydrogen beam, one second in one BILLION years. If you want to read about it, read my thread labled 'more power of photonics' which I see not much people are interested in, but is there right in the science forum for anyone to read. The reason accuracy on that order is important is for physicists to have a tool to probe the accuracy of the standard model of matter, with the ability to see if fundamental constants like the fine structure constant is really constant or has it ever so slightly changed over billions of years, if so, the standard model of matter will have to be overthrown so its an important tool in physics.