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

Posted by msmash on from the when-every-second-counts dept.

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.

21 of 111 comments (clear)

  1. Durability by ELCouz · · Score: 4, Insightful

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

    1. Re:Durability by 93+Escort+Wagon · · Score: 4, Funny

      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.

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    2. Re:Durability by flopsquad · · Score: 3, Insightful

      "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."

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    3. Re:Durability by arglebargle_xiv · · Score: 2

      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.

  2. they could have used a grandfather clock by Anonymous Coward · · Score: 2, Insightful

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

  3. Fail High School Physics Artlcie! by CajunArson · · Score: 5, Insightful

    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!

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  4. Not good enough by backslashdot · · Score: 2

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

  5. Well.... by johnsmithperson123 · · Score: 2

    Why did they put it in a satellite lasting under a millennium in lifespan?

  6. Spacetime? by mspohr · · Score: 2

    So, how do they compensate for space time dilation?

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  7. Obligatory by paiute · · Score: 2

    Mr. President, we must not allow an atomic clock gap!

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  8. Nationalism by ThatsNotPudding · · Score: 3, Funny

    In the coming decades, the Chinese will easily eclipse the US in being insufferable, jingoistic dicks.

  9. ...and Accuracy by Roger+W+Moore · · Score: 5, Interesting

    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 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.

    1. Re: ...and Accuracy by peragrin · · Score: 3, Insightful

      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

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    2. Re: ...and Accuracy by Anonymous Coward · · Score: 2, Interesting

      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, and I wish popsci authors would not extrapolate and lie like this. I work with Caesium fountain clocks and Rubidium strobe oscillators in my work, and they are not as reliable as OCXOs. "in a billion years", "in a thousand years" etc, implies a longevity that these devices simply do not possess.

    3. Re:...and Accuracy by Whip · · Score: 4, Informative

      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.

  10. jingoism by unixisc · · Score: 3, Insightful

    You mean that they haven't already, w/ those South China Sea islands, and all that?

  11. Extra pedantic... by Roger+W+Moore · · Score: 2

    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 so little about it: at least 95% of what it is made of is so far unknown to science.

  12. A billion years? Really? by hey! · · Score: 2

    Want to bet?

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  13. Re:not really by AK+Marc · · Score: 2

    With relativity, it'll be 100% accurate. It's you who is inaccurate.

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  14. Easy Maintenance by ememisya · · Score: 2

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

  15. Re:Besides by Plus1Entropy · · Score: 2

    They put the 12 at the top, same as us.

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