New Most Precise Clock Based On Aluminum Ion 193
eldavojohn writes "The National Institute for Standards and Technology has unveiled a new clock that will 'neither gain nor lose one second in about 3.7 billion years,' making it an atomic clock twice as precise as the previous pacesetter, which was based on mercury atoms. Experts call it a 'milestone for atomic clocks.' The press release describes the workings: 'The logic clock is based on a single aluminum ion (electrically charged atom) trapped by electric fields and vibrating at ultraviolet light frequencies, which are 100,000 times higher than microwave frequencies used in NIST-F1 and other similar time standards around the world.' This makes the aluminum ion clock a contender to replace the standard cesium fountain clock (within 1 second in about 100 million years) as NIST's standard. For those of you asking 'So what?' the article describes the important applications such a device holds: 'The extreme precision offered by optical clocks is already providing record measurements of possible changes in the fundamental "constants" of nature, a line of inquiry that has important implications for cosmology and tests of the laws of physics, such as Einstein's theories of special and general relativity. Next-generation clocks might lead to new types of gravity sensors for exploring underground natural resources and fundamental studies of the Earth. Other possible applications may include ultra-precise autonomous navigation, such as landing planes by GPS.'"
Re:Plane landings? (Score:5, Informative)
Re:Plane landings? (Score:3, Informative)
The relativistic speed means their clocks run slower than clocks sitting still on Earth, according to special relativity. Another source of GPS time difference is that they are farther away from the center of Earth's gravity than we are, so according to general relativity, their clocks run faster than clocks on Earth. Both factors have to be taken into account.
Re:Plane landings? (Score:5, Informative)
I do have my Private Pilots license with Instrument rating, but I also love physics...
Re:Assuming We're still around (Score:1, Informative)
Long-distance low-frequency radio syncing is actually quite inaccurate, at least as far as atomic timekeeping goes. There's the simple propagation delay based on your distance from the radio source, plus the possibility of getting waves that were reflected from the ionosphere, possibly more than once, likely varying from sync to sync, and no good way to know how much additional delay that adds even if it were consistent. Not to mention the issues with synchronization itself -- once you get the correct time code you wait for the next "beat" to start counting, but there's some delay between when the beat is received and when counting starts, or there's anticipation of the beat and possible imprecision due to that anticipation.
And there's the issue of non-continous correction. While your watch indicates approximately the correct time after a sync, there's likely some jump in the notion of local time after each sync, and between syncs there's no guarantee that timekeeping is accurate at all -- if you design a clock to sync every 12 hours it can be off by almost 2 seconds/day without displaying the wrong second-accurate time, and that doesn't lead to very consistent timekeeping on intervals shorter than the sync period.
All in all, it's plenty accurate for a wrist watch, but it's not really a high-precision time or frequency source.
Re:Plane landings? (Score:2, Informative)
Even if time did stand still or go backwards, you wouldn't be able to tell since our perception is dependent on time going forwards. Since time must be constant in any non-accelerated reference frame (gravity asside), if a clock was stopped by the slowing of time, so would your heart, and cells, and brain, and electrical impulses, etc...
I would recommend a pair of books for you written by Richard Feynman. Six easy pieces [amazon.com] and Six Not so easy pieces [amazon.com]... They provide a good "foundation" if you've never had a college level calculus based physics series before...
Re:Plane landings? (Score:4, Informative)
But his assumption that clock error is responsible for all of the current lack of precision is wrong. Clock error is responsible for probably less than a third of the current error. Atmospherics, multipath reflections, and ephemeris errors account for the bulk of the error.
Sure, every improvement is an improvement. But these clocks are not a magic bullet that will magically grant centimeter precision.
Re:Plane landings? (Score:4, Informative)
Red and blue shift are not caused by moving faster than the speed of light in the local medium (though Cherenkov radiation is), but rather by motion of the emitting object relative to the observer. (Not to mention cosmological and gravitational shifts.)
Re:Plane landings? (Score:5, Informative)
"Full blind autoland" systems have been around since the 1960's An unexpected problem with the first systems is that they were "too accurate", runways wear out quickly if touchdown always happens in the same place.
If GPS accuracy gets good enough to where you don't need those aux systems (or need them as primary at least), complexity of autopilots would drop significantly...
Most landings are performed by pilots. Even in an autoland situation the pilots go through similar procedures to if they were flying the plane. Otherwise things are likely to end up like TK1951.
Re:Ah, I unplugged the atomic clock... (Score:1, Informative)
I think you miss the point of accurate clocks. Everything you have said is exactly why we need such accurate clocks. The accuracy of GPS is not due to the accuracy of a single clock. It comes about by comparing clocks on different satellites. It is those relative differences that allow you to measure distance or changes in the fine structure constant, or whatever else you want to measure. Let's say we can get one of these clocks on a GPS satellite. How will we know the exact orbit? By comparing it to a stationary clock. That will tell us its altitude. Then we use the clock on the satellite to compare against other clocks on other satellites. The worse every clock in that chain is, the worse our overall results are. The better every clock in that chain is, the better. Yeah, the whole point of accurate clocks is so that you can compare them so that you can measure all of the things you are worried about.