How an atomic clock works, and its use in the global positioning system (GPS)

How an atomic clock works, and its use in the global positioning system (GPS)


How An Atomic Clock Works And its Use in the Global Position System (GPS) I want to show you the most amazing thing. The world’s first commercially available chip scale atomic clock. Symmetricon’s CSAC. That’s right: This tiny device about the size of a quarter is an atomic clock. The most accurate atomic clocks lose about a second over 138 million years. The way that atomic clocks work amazes me let me explain how the very first one worked. I’ll start with Jell-O. Tap a block of Jell-O and it wiggles back and forth. Just like the swings of a pendulum in a grandfather clock the oscillations of this Jell-O keep time. Now, Jell-O isn’t very good for this but inside an atomic clock there’s a chunk of quartz of a similar shape that it if we tap it which we do it with a jolt of electricity it will oscillate some five millions times per second. It keeps time to about 1 second in 90,000 years a fraction of the accuracy needed for an atomic clock. Quartz loses time because it slows down and needs to be “nudged” to restore its oscillation. There’s where the “atomic” part of an atomic clock comes into play. We use cesium atoms to control those nudges very accurately. Every time the quartz’s oscillations slow down just the tiniest bit we give it a tap an electrical jolt at just the right time so essentially its oscillations never decay. Let me show you how we use cesium to do this. The atoms in pure cesium exist mostly in two slightly different forms A low energy form and one with just a bit more energy. For an atomic clock these two states have two properties critical to making a clock. One, they can be separated by a magnet. And two, the lower energy atoms can be converted to the higher energy ones if we bombard cesium with the right radiation. Engineers tie the slowing down of the quartz vibrations to the precise wavelength of the bombarding radiation to create a feedback loop. Let me show you how. In an oven we heat cesium chloride to create a gaseous stream of cesium ions. The stream contains both the low and high energy ions. We first flow it through a magnet separating the two types, discarding the high energy ones, allowing the lower energy ions to pass into a chamber. Inside the chamber we bombard the ions with just the right wavelength radiation to make them jump to higher energy. As these gaseous ions leave the chamber they pass through another magnet that directs high energy ions toward a detector this time discarding any lower energy ones. The detector converts the arriving ions to a current. The trick here is to tie that current from the detector to the quartz oscillator. When the quartz’s oscillations decay that is it slows down a little then the energy bombarding the cesium ions in the chambers changes and fewer high energy ions exit the chamber, so current decreases or stops. This tells the electronics to “zap” the quartz oscillator and correct the period of oscillation. It does this by applying the proper voltage that via the piezoelectric effect, taps the quartz and restores its oscillations. Thus creating a clock that loses less than a second over many million years. Our world runs off such accuracy. For example, the global position system (GPS) requires it. The global positioning system consists of 24 satellites orbiting the earth. A GPS receiver uses the position of four of these satellites to locate itself. One to correct the time on the receiver and three to locate its position. Here’s how it works. A signal is sent to the receiver from the first satellite that contains that satellites location and the signal’s time of departure. The receiver then multiplies the signal’s travel time by the speed of light to calculate its distance from the satellite. With one satellite the receiver knows that it’s located on a sphere around that satellite with a radius equal to the calculated distance. So, it does the same calculation with a second satellite. The intersection of these two spheres narrows the location to the circumference of a circle. Then with a third satellite the receiver can reduce the location to a single point. Since signals are traveling at the speed of light, being off by even a millisecond means an error of about a million feet, or 300 kilometers. But with atomic clock accuracy the receiver can locate itself to about 3 feet. I’m Bill Hammack, the engineerguy. This video is based on a chapter in the book Eight Amazing Engineering Stories. The chapter features more information about this subject. Learn more about the book at the address below.

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  1. +Jamie Jr DeFelice +carolyn mmitchell +engineerguy Conspiracy? Unfortunately Against Humanity. This Video Did Not Show Any Real 'Video' Of Satellites In Space; Would You Like To Know Why? Because They Don't Exist. We're Engineers Too, And Lawyers; And All The Experimentation And Evidence Weighs Heavily In Favor Of An Earth That Is Stationary And Planar; And Therefore Not Orbited By Satellites And Space People (Space Is A Hoax). Strength. GODspeed.

  2. Even though the explanation of the principle of a frequencystandard is correct, the description of the cs atomic (beam) clock is not. It's not using Cs ions but rather neutral Cs-133. An oven creates a beam of neutral Cs atoms which are in either of the two hyperfine states of its ground state. By utilizing a Stern-Gerlach selector, a beam only consisting of only one state can be created. Then the interrogation in the microwave cavity happens via the Ramsey-Scheme and in the end, another Stern-Gerlach selector distinguishes between both states, so one can measure the individuale population in dependence of the applied microwave field.

  3. This guy doesn't know what he's talking about jello works fine it was actually used in the beginning of good technology.

  4. The piezoelectric effect is at the core of all electronic technologies and this is the epitome of its engineered application. Truly awe inspiring when physics can be so precisely controlled. I love this!

  5. 0:20 I don’t know what your smoking but it’s more the size of 4 quarters lol. Unless you accidentally held that quarter way closer to the camera that thing is much larger than that.

  6. “Not sure if you can’t follow everything because you’re stupid or I just talk too fast? Buy the book and find out.”

  7. Another fine video. But of course there is no atomic clock in a GPS receiver so this doesn’t explain how gps works. The short answer to that is the quartz clock in a receiver is not accurate enough to get a fix. However the quartz clock is accurate enough over the short interval that the error is equal for all satellites being received and that enables the processor to then determine a position using clever mathematics. This process does however require an extra satellite hence you need 4 satellites to get a 3d fix or 3 sats for a 2d fix (2d as in it is assumed you are on the surface of the earth).

  8. How do you calculate distance between the satellite with just a time? Since there are no atomic clocks in the receivers how would you calculate the time difference?

  9. So basically , it's a glorified quartz clock? I'm having to fill in the gaps in my mind… but I guess the atoms nudge the "jello" just at the precise moment it needs to be nudged? Also … how often is that?

  10. Uuuummmm ??? It's only accurate to 1 second every 138 million years ? Well ?? I guess I can live with that ! As long as my coffee pot turns on at exactly 7 am

  11. just something i want to mention:
    3 satellites will not trilaterate the position to a single point, but in fact, two points. one is on the surface of earth, while the other is in space. it acts as if there is another satellite at the core of the earth giving it a reading of earth's radius, so it can conclude your position to one point.

  12. It was correctly mentioned that four are needed, but the demonstration then goes on to say that only three are needed for locating position.

  13. Thank you for this very well done explanation , i was always curious as to how atomic clocks worked and i had a completely wrong idea about how they did , again thank you for clearing things up

  14. Went to see about buying one, saw the price, decided I don't need that kind of accuracy in my life.

  15. “ it’s about size of a quarter”
    – puts quarter near it
    – big size difference is clearly visible
    – doesn’t give a flying fuck
    -profit???

  16. I hope Bill didn't start the birds and the bees talk with his kids like that. LOL "Son, go ask your mom to make some jello." Haha
    Amazing how complex everything has to be to make our lives so simple.

  17. if the radiation within the chamber decays, do they insert more radiating components or they simply produce another chamber with radiation?

  18. Rrrrrright.Ok, that makes sense. Thank you.I'm still working on how peanut butter and jelly sandwich works.

  19. Where do you take energy to heat cesium chloride in an oven?
    Or it is some kind of a natural process?

  20. I'm almost clicked on the link for that book but, I'll wait to have couple more videos down. Those references for the book are getting more interesting with every video though….

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