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China Space IT Technology

China's Atomic Clock in Space Will Stay Accurate For a Billion Years (rt.com) 111

The space laboratory that China launched earlier this week has an atomic clock in it which is more accurate than the best timepiece operated by America's National Institute of Standards and Technology, according to Chinese engineers. The atomic called, dubbed CACS or Cold Atomic Clock in Space, will slow down by only one second in a billion years. In comparison, the NIST's F2 atomic clock, which serves as the United States' primary time and frequency standard, loses a second every 300 million years. From an RT report:"It is the world's first cold atomic clock to operate in space... it will have military and civilian applications," said Professor Xu Zhen from the Shanghai Institute of Optics and Fine Mechanics, who was involved in the CACS project. An atomic clock uses vibrations of atoms to measure time, which are very consistent as long as the atoms are held at constant temperature. In fact, since 1967 the definition of second has been "9,192,631,770 vibrations of a cesium-133 atom." In a cold atomic clock, the atoms are cooled down with a laser to decrease the effect of atom movement on the measurements. CACS goes even further and eliminates the pull of Earth's gravity by being based in orbit.
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China's Atomic Clock in Space Will Stay Accurate For a Billion Years

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  • Durability (Score:4, Insightful)

    by ELCouz ( 1338259 ) on Saturday September 17, 2016 @04:37PM (#52908425)
    Well the atomic clock won't last that long see that second offset!
    • Can you read the time in chinese?
    • ...and Accuracy (Score:5, Interesting)

      by Roger W Moore ( 538166 ) on Saturday September 17, 2016 @05:58PM (#52908721) Journal
      It probably won't stay that accurate for that long either if it is in space because it is in a different frame of reference and so relativistic effects, including those from general relativity, will build up. This is why the GPS satellites have to have their clocks corrected to stay accurate within the tolerances required. The shift per day for GPS is around 38 microseconds per day [wikipedia.org] which if it is the same for this satellite means that in 26,316 years the clock will be off by one second. This is still a long time but a lot, lot less than 1 billion years.
      • by peragrin ( 659227 ) on Saturday September 17, 2016 @06:25PM (#52908841)

        There is a much simpler reason why it won't last as long. Material degradation. Show me a system let alone a complex one like a satellite that doesn't lose bits of itself over time. Space radiation will slowly alter the chemical structure of the house, power supply, etc until it is non functioning and that will happen in just a thousand years or so

        • Re: (Score:2, Interesting)

          by Anonymous Coward

          It's an atomic clock. They usually have a functioning life of less than 30 years. To put it bluntly, "Stay accurate for a billion years" is just wrong. Even over the timeframe of 50 years, an oven controlled quartz oscillator is more accurate than a Caesium fountain clock, because the Cs fountain will stop functioning and it will fall out of lock, relying on a lower quality quartz oscillator.

          A nanosecond per year has the same slope as a second in a billion years, but the two have very different meanings, an

      • Not accurate ... frame of reference.

        I think someone didn't understand his physics course very well. Being in a different frame of reference does not affect a clock's accuracy. GPS clocks aren't corrected either, they are compensated for. There's a big difference.

        • Re:...and Accuracy (Score:5, Informative)

          by Whip ( 4737 ) on Saturday September 17, 2016 @09:46PM (#52909449)

          Well, it depends on how you define "accuracy". A clock can only ever be accurate in its own reference frame. As soon as you reach outside of the local reference frame, though, there's nothing directly tying the ticking of this clock to any other. So while atomic clocks are great for knowing how much time has passed locally, they are (in and of themselves) generally pretty useless at knowing what time it is.

          "What time it is" is effectively a fabrication. UTC (the most common version of "what time it is") combines the measurements of several hundred atomic clocks around the world to get an "official" time. Several hundred clocks that are all accurate to parts-per-billion, but all existing in different reference frames, and thus all ticking slightly differently. (And as a bonus, those reference frames change as materials deep in the earth move, underground water tables change, etc, so you can't even just program an offset into each clock so that everything lines up...)

          GPS clocks are actually corrected. There's at least three different corrections and compensations going on:

          1. The clocks were configured so that they would run at the right speed in orbit, by making them run at the wrong speed on the ground (this is a compensation)
          2. GPS time is 'steered' towards UTC(USNO) to keep GPS time and UTC as close as possible (this is a correction)
          3. The GPS system announces that the time differential between UTC(USNO) and GPS time is, and how fast they are diverging -- this is the A0 and A1 parameters that caused the 13usec timing anomaly in January. (This is a compensation)

          Anyhow, the best way to look at the long term 'accuracy' of an atomic clock is to consider the accuracy to be the amount of uncertainty existing in passage-of-time measurements in the clock's local reference frame. And that, in and of itself, has almost nothing to do with actually knowing what time it is.

          • by Whip ( 4737 )
            I guess I should also add that the clocks on the individual SVs (satellites) are also both corrected and compensated (the references above are about the GPS timescale itself, which the SVs still individually drift from). So that's at least three places there are compensations and two there are corrections. ;)
        • I think someone didn't understand his physics course very well. Being in a different frame of reference does not affect a clock's accuracy.

          Actually since I'm now the one at the front giving the lectures I'm petty confident I do understand my own physics courses! ;-) Being in a different frame does affect a clock's accuracy when I am making a measurement because time is local. The moment you are in a different frame the accuracy of the clock is limited at best by the accuracy with which you can determine the frame of the clock relative to your own.

          In fact this is now the limiting factor in the accuracy of clocks since they can now make cloc

      • by dywolf ( 2673597 )

        and shouldn't it state "reduces the affect of gravity" rather than "eliminate", since orbit is by definition ultimately a result of gravity, albeit a special case, but gravity none the less?

    • by 93 Escort Wagon ( 326346 ) on Saturday September 17, 2016 @06:00PM (#52908735)

      Well the atomic clock won't last that long see that second offset!

      Actually, you're wrong - they've planned (and compensated) for orbital decay. Every so often, the satellite releases a Galaxy Note 7 from its earth-facing side. The subsequent explosion restores the satellite into its original orbit.

      • Launching Galaxy Note 7s into space would surely be a violation of one of those "don't launch weapons into space" treaties, right?
    • Re:Durability (Score:4, Insightful)

      by flopsquad ( 3518045 ) on Saturday September 17, 2016 @07:03PM (#52908969)
      "Cool clock, I hear it's accurate for a billion years!"
      "Yeah. But I keep it in this chaotic field of hypervelocity space debris where millions of tiny bits of junk are whizzing around, constantly threatening to punch a big hole in my clock."
      "So... you don't think it's going to last a billion years?"
      "I'm not optimistic."
    • A hell of an environment to put such a device into and expect that it will maintain the levels of accuracy and reliability attainable here on earth. I suspect that it is another boast in an attempt by the Chinese government to boost their stature in the international scientific community. One good sunspot burst and it is toast, LITERALLY!
    • It won't last long for another reason: Turns out they used locally-sourced components, of which 20% were counterfeit, 35% had been recycled from scrapped cellphones and computers, 15% were made with incorrectly-copied formulae for the electrolytic, 10% fell off the circuit board after lauch due to bad pick-and-place/soldering, and another 10% were manufacturer's rejects that had been salvaged and re-marked.

      The clock is currently indicating that today is the umpteenth of Octember.

    • Well the atomic clock won't last that long see that second offset!

      Statistically, it's more likely to have orbital degradation with the failure of boosting mechanism, damage from orbital junk, damage by solids in space puncturing it and damaging equipment, damage from a nearby supernova's emissions, or failure of comms equipment and/or panels, far before the Chinese make the reading of its clock value available to anyone but their government and satellite-based guidance systems. :)

  • by Anonymous Coward

    Because the satellite will come down in 10 years, maybe 20 anyhow.

  • by CajunArson ( 465943 ) on Saturday September 17, 2016 @04:40PM (#52908437) Journal

    CACS goes even further and eliminates the pull of Earth's gravity by being based in orbit.

    Yeah, spot the glaring contradiction in that sentence. Hint: you can be free of the pull of Earth's gravity, or you can be in orbit around Earth... but not both!

    • And for pedants: Yes, technically nothing in the observable universe is theoretically "free" of Earth's gravitational influence, but "free" in as much as Earth's gravity is not the predominant factor in the gravitational force that the satellite experiences.

      • by NFN_NLN ( 633283 )

        Are suggesting that the gravitational effect diminishes over distance? Maybe even non-lineally?

        • by tomhath ( 637240 )

          diminishes over distance? Maybe even non-lineally?

          How about in free fall. And yes, we all know gravity is the reason it stays in constant free fall.

          • No, gravity is not what causes free fall. Gravity does, on the other hand, make orbits.

            Orbit is, by the by, an example of the concept of "throwing yourself at the ground and missing". Essentially, you're falling fast enough in the right direction to miss the planet/star/whatever. But gravity at LEO is still almost a full g. Rather lower at GEO, but still substantially larger in magnitude than any other force acting on the satellite.

      • And for pedants: Yes, technically nothing in the observable universe is theoretically "free" of Earth's gravitational influence

        Actually if you want to be extra pedantic that may not be quite true. Parts of the universe which we can observe today (and so are in the observable universe) may by now be causally disconnected from us due to the accelerating expansion of the universe and so no longer feel the Earth's gravity. Of course we really don't know too much about what is driving the acceleration so perhaps this does not apply but it just goes to show that it is best not to make sweeping statements about the universe when we know

      • How do you figure out that Earth's gravity is "not the predominant factor in the gravitational force that the satellite experiences" for a LEO satellite? You bet it is! What else should be predominant? The Moon? The Sun? Jupiter? Just go ahead and calculate their pull.
    • No. They said the pull of gravity, the didn't say it escaped gravity. Therefore, there is an implied dostinction between the two. It is still within the gravitational field, so it orbits. But gravity no longer creates stress forces on the mechanisms.

      • by Anonymous Coward

        Actually that's not right either. In orbit, the satellite will pass over different locations on the Earth that have (very small) variations in gravitational pull that will affect the satellite. In a fixed location on earth, the variations in gravitational pull over time will be much reduced since you aren't moving relative to the surface of the earth.

        What *is* greatly reduced are the effects of vibration from any source of mechanical noise on the earth including everything from plate tectonics to some inte

        • by OzPeter ( 195038 )

          That's not a fluctuation in gravity though.

          There's a "yo momma" joke in there somewhere

        • Not to mention the miniscule tidal difference between the near side and the far side of the satellite, which may show up in such fine measurements.

          I wonder if all these might add up to more distortion than a fixed point on the Earth.

    • If one considers "eliminating the pull of Earth's gravity" also as being weightless, then being in orbit makes this an accurate statement.

    • LEO (Low Earth Orbit) requires a velocity of 7.8 km/s. The surface of the Earth (at the equator) rotates at a bit under 0.5 km/s. So the relative difference in speed is 7.3 km/s.

      At that speed, the time dilation effect due to relativity is sqrt(1 - v^2/c^2) = 0.99999999970353434

      So an atomic clock in LEO will run slower than one on the ground, losing 1 second every 3373072286 seconds, or 1 second every 106.96 years. You can compensate for that with a math correction which takes into account relativit
    • Nigel Farage: We will negotiate exactly how we orbit the earth on a sovereign basis, rather than being ordered to do so by barmy Belgian bureaucrats. And the Polacks can all fuck off.

  • by backslashdot ( 95548 ) on Saturday September 17, 2016 @04:48PM (#52908467)

    I don't want to be late for my dentist appointment in the year 1,000,002,017.

  • by Anonymous Coward

    This must be a pet project of White Rose.

  • by John Smith ( 4340437 ) on Saturday September 17, 2016 @04:53PM (#52908487)
    Why did they put it in a satellite lasting under a millennium in lifespan?
    • Why did they put it in a satellite lasting under a millennium in lifespan?

      It's not about long-term functionality.. It's all about comparison to other human technology. Just like the comparison of the length of dic/)*Ev&
      NO CARRIER

  • So are our electronic devices going to be able to receive a signal and sync wirelessly?

    • Besides, what if the signaling standards change over that time - would that mean that the timepiece would be out of whack by a second and therefore worthless?
  • by mspohr ( 589790 ) on Saturday September 17, 2016 @05:11PM (#52908547)

    So, how do they compensate for space time dilation?

    • by Yvan256 ( 722131 )

      Simple, by adding the lag it takes for the signal to reach Earth, multiplied by the number of oxygen molecules between the satellite and the receiver, divided by the square root of of double the radius of the satellite. Let cook for 15 minutes and add salt to taste.

    • by AmiMoJo ( 196126 )

      They don't. They use time dilation to measure other things by comparing with a clock on the ground. That's the basis of satellite navigation, for example. Also let's then timestamp encryption data with enough accuracy to make attacks on the system extremely difficult.

    • Easily. The calculations for both relative speed dilation and gravitational dilation are known. Just calculate the correction factor and adjust clock speed accordingly.

    • So, how do they compensate for space time dilation?

      They don't believe in it.

      Too soon? :)

  • The atomic called, dubbed CACS or Cold Atomic Clock in Space, will slow down by only one second in a billion years.

    If they know it's going to slow down, and by one second, why don't they just add a billionth of a second a year?

    I assume what was meant was "drift by at most one second."

    • It is a rather badly worded description of how an accurate clock keeps time. It makes much more sense to say that it has a timekeeping error of less than 1 billionth of a second per year. Such a clock will only run for 10 to 20 years, so saying what it will do in a billion years is meaningless.
      • IIRC, the NIST clock is here on earth, so would last, well, if not a billion years, at least as long as the NIST keeps it plugged in. The Chinese space clock would be at the mercy of flying meteorites and other space objects, and vulnerable to being destroyed. Was there a compelling reason that that clock couldn't just be hooked up and plugged into the CPC's headquarters in Beijing?
        • by AK Marc ( 707885 )
          Being in space, the temperatures will be more consistent. This leads to fewer errors from thermal issues, so the clock is more accurate.
          • NIST could put their clock on the North Pole, or somewhere close - like north of Greenland or Ellesmere Island in Canada, and the thermal issues will be gone
            • Sorry, talking about the Chinese, they could send it north of their pal Russia - maybe to Yakutia, where the temperature variations won't be enough to matter
              • by AK Marc ( 707885 )
                Large swings in outside temperatures in the areas you listed. You'd be better off putting it in the Amazon jungle, if the goal was to have a stable temperature. And reality says that they are enough to matter. Hence why it's in space.
  • by paiute ( 550198 ) on Saturday September 17, 2016 @05:32PM (#52908615)
    Mr. President, we must not allow an atomic clock gap!
  • China's Atomic Clock in Space Will Stay Accurate For a Billion Years

    The key to successful journalism is understanding that adding "...in space" to anything makes it more interesting. If I say, "I just drank a bottle of beer", it's boring. If I say, "I just drank a bottle of beer...in space" it's suddenly more interesting.

    Try it yourselves at home. Make a boring declarative statement and add, "...in space" to the end and see if it hasn't become more interesting.

    Now that I think about it, adding "...for a

  • Nationalism (Score:4, Funny)

    by ThatsNotPudding ( 1045640 ) on Saturday September 17, 2016 @05:50PM (#52908693)
    In the coming decades, the Chinese will easily eclipse the US in being insufferable, jingoistic dicks.
  • by hey! ( 33014 ) on Saturday September 17, 2016 @07:27PM (#52909051) Homepage Journal

    Want to bet?

    • by Anonymous Coward

      It's OK, the satellite around it was made in China, so it'll be broken in less than 3 years.

      • It's OK, the satellite around it was made in China, so it'll be broken in less than 3 years.

        Oh, so they CAN make quality products over there, eh? Now I know what all of the money I've been spending on electronics and sticky note dispensers has been going toward! :)

  • With relativity, it will actually stay accurate for 0 seconds relative to all other mass.
  • by ememisya ( 1548255 ) on Saturday September 17, 2016 @10:29PM (#52909619) Homepage
    So they just have to correct it by a second 5 times before the Sun explodes.
    • by xupere ( 1680472 )

      I'd play it safe and set it 5 seconds fast now so that we don't forget later.

    • So they just have to correct it by a second 5 times before the Sun explodes.

      Elementary, my dear ememisya! Atomic matter from all of the dead life on Earth, as well as interstellar waves, will fix it all by itself. Has one of those "self-kerrectin' mechanisms" or some junk like that. Heck, one of the carbon atoms from your left eye might be part of the correction that is implemented .00000000000000000000001 picoseconds before the Sun's collapse reaches critical.

      Well, since Earth isn't the only thing that has atoms to spread through a dying planetary system, it sounded good, anywa

  • "It is the world's first cold atomic clock to operate in space."

    Is it really the worlds anything if it's in space??

    • "It is the world's first cold atomic clock to operate in space."

      Is it really the worlds anything if it's in space??

      Article clearly says it's for timing of their geostationary satellite positioning system, so no. Nobody gets anything. At least not until a Russian kid bored out of their mind hacks it in a week. Har har.

      Oh, you mean in terms of possession by the planet as an entity.. All I can say is that as long as it's within gravitational pull of Earth, it's Earth's. :)

  • a) "accurate" is not tied to "1 second" it may be - depending on application - a microsecond or a millenium.

    b) it will not stay accurate for a billion years because it will fail before that time - and probably it would have be maintained (power, helium etc) much ealier.

  • I think it is pretty cool they they can achieve this kind of accuracy, but to what end I cannot fathom. The rt article says:

    The Chinese plan to improve their BeiDou Navigation Satellite System with synchronization signals from the new orbital atomic clock.

    I'm thinking a clock accurate to 1 second every 1,000,000 years would more than suffice. Am I wrong?

    • The more accurate a clock on a GPS satellite is the more accurate will be the positioning information provided to end users. It's as simple as that.

  • by Anonymous Coward

    Clocks... In... Sssspppppppaaaaaaaaacccccceeeee!!

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