Device That Revolutionized Timekeeping Receives an IEEE Milestone (ieee.org) 46
An anonymous reader writes: The invention of the atomic clock fundamentally altered the way that time is measured and kept. The clock helped redefine the duration of a single second, and its groundbreaking accuracy contributed to technologies we rely on today, including cellphones and GPS receivers. Building on the accomplishments of previous researchers, Harold Lyons and his colleagues at the U.S. National Bureau of Standards (now the National Institute of Standards and Technology), in Washington, D.C., began working in 1947 on developing an atomic clock and demonstrated it to the public two years later. Its design was based on atomic physics. The clock kept time by tracking the microwave signals that electrons in atoms emit when they change energy levels. This month the atomic clock received an IEEE Milestone. Administered by the IEEE History Center and supported by donors, the milestone program recognizes outstanding technical developments around the world.
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Me thinks you don't understand atomic clocks at all.
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Re:Atomic clock operation (Score:5, Informative)
No, they aren't. Radioactive decay is random and would make a terrible clock. The second is defined in terms of a electron transitions of the cesium-133 atom, which is the only stable isotope. Hydrogen maser clocks are even more stable timekeepers, but again, not based on a radioactive isotope.
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Hydrogen maser clocks are even more stable timekeepers, but again, not based on a radioactive isotope.
Don't forget rubidium! - much cheaper than cesium or hydrogen, but also not as accurate. (Also not radioactive)
Hydrogen masers become unstable and drift [chronos.co.uk] ('aging effect') while Cesium is consistent. Applications where very accurate time over both the short and long term are required (such as Galileo GNSS) use a combination of Hydrogen and Cesium standards, using each to overcome the weakness of the other.
Cesium also benefits from the fact its oscillation is literally the definition of a second.
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Re:More information (Score:5, Informative)
Well, I was going to mod you up +1 Informative, but then I notice the goatse link... Now, since I'm writing this, I can't mod you down either. But at least I can warn others to check the links before clicking. (Note: The rest of the links appear to be legit.)
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The other links are actually informative. Why throw out the good with the bad? You might choose to do it otherwise, but I chose to do it this way. Have a nice day.
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Thanks, don't know how that happened.
Re: GoDaddy did the right thing in the wrong way (Score:2)
Inattentive carelessness would be my guess as to how it happened.
ELI5: How did they set the first atomic clock? (Score:2)
Did they just use whatever the "reference time" was for some existing highly accurate clock? Or did they do a bunch of astronomical measurements and then set the atomic clock based on some astronomical reference that defined some specific time?
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For information about the history of the definition of a second as measured by the first cesium clock, see https://en.wikipedia.org/wiki/... [wikipedia.org].
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Simple, they googled it.
Re: Why do phone (cell) systems need accurate timi (Score:1)
Accurate time is needed by cell phones (and all digital networks) for a number of purposes. Accurate time is needed to clock high speed data circuits. When you're talking about billions of bits per second, a small error loses lots of bits. Accurate time is needed for seamless handoffs of signals between cell sites. It is needed for enhanced 911 location systems to work. It is used in radio frequency systems to keep transmitters on frequency which becomes more and more important as channels get closer to
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The GPS receiver in your phone (and GPS/GNSS systems in general) utterly depend on hyper-accurate timekeeping to work. In a nutshell, the orbiting satellites are transmitting perfect "true" time continuously, as well as information on its orbit. Your GPS receiver uses that information to work out the precise local time, and using that it can calculate the exact position of the satellite around the earth, the distance to each of the satellites, and thus its own position.
The ephemeris data (precise informatio
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Redefinition (Score:2)
Time Geeks (Score:2)
Many years ago, I wound up doing a small contract/visit at the Naval Research Labs at the Navy Yards in DC. Partly by tradition, partly by necessity, the Navy has a healthy obsession with accurate time keeping, and I was working with the Navy's time geeks. They were a fascinating group of guys to work with, their equipment and clocking was accurate enough to measure the (electrical) distance to a satellite in geosynchronous orbit to within half an inch.
Anyhow, I was having lunch in his office and there on t
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Well, even if you get that chip, you need to have traceability! Just because you have the precision of an atomic clock, doesn't mean that you have the accuracy yet... ;) You still need to be able to trace its settings back to a standard... Also, have you made the relativistic corrections for your altitude and that nearby mountain?
In all seriousness, when I did work for a company that built satcom equipment, we eventually did buy a GPS disciplined time and frequency standard. We went for the cheap model that
"Milestone" is a plaque (Score:2)
The first atomic clock, developed near this site by Harold Lyons at the National Bureau of Standards, revolutionized timekeeping by using transitions of the ammonia molecule as its source of frequency. Far more accurate than previous clocks, atomic clocks quickly replaced the Earth’s rotational rate as the reference for world time. Atomic clock accuracy made possible many new technologies, including the Global Positioning System (GPS).
and posted it in a park in Washington DC near where the original work was done.