Tag Archives: clock

Please continue to hold while I sort this thing out

Remember how mechanical clocks are prone to lose time? It’s because they’re made out of physical machinery—pendulums or mainsprings and gears. We replaced those mechanical parts with a quartz crystal, zapped it with electricity to make it vibrate and got digital clocks. Digital clocks are more reliable, but they still lose 15 seconds every month.

To make the even-more-reliable atomic clock, we replaced the quartz crystal with atoms. Atoms vibrate on their own. We’re building a clock that’s as free of physical, mechanical parts as we can manage in this bad old fallen world.

Here’s what I’m getting from my exhaustive research so far: somehow cesium atoms are funneled down a tube. How do they get the atoms out of the cesium? I don’t know. The atoms are exposed to radiation—radio microwaves like the kind you use to heat up your old cold French fries—which makes them switch back and forth between energy states. The idea is to tune the radio waves to sync up with the atom’s own vibrations at 9,192,631,770 times every second. It’s not easy to get this exactly right—like tuning in a jazz station from 2 counties over on an old radio with dials. There’s a detector at the end of the tube. When the radio waves are at the exact right frequency (the same frequency as the atoms’ vibrations), the atoms change energy states and bounce off the detector—which means one second has passed. Then what? I dunno. How does the detector know when the atoms change from State B back to State A ? I dunno.

Back to my research. Thanks for your patience. Please continue to hold.

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Quartz crystal

Three inventions moved clocks and watches away from being mechanical/analogue so they could become digital: The quartz crystal, the circuit board and the liquid crystal display.

Quartz is a common mineral that does this weird thing: it generates a tiny bit of electricity if it’s squeezed, and vibrates when you send an electric charge through it. Watchmakers cut quartz into a shape that looks like a tuning fork, so it vibrates like a tuning fork.

So if we just squeeze the quartz—I’m not sure if this is really the way it happens…

…wow! It works! (photo credit: KTUL.com)

Amazing!! (photo credit: Google Earth)

Okay, okay, that was just a gag. You knew that, right? Just a teeny tiny electrical charge passes through the quartz crystal to regulate the watch.

“Inside a quartz clock or watch, the battery sends electricity to the quartz crystal through an electronic circuit. The quartz crystal oscillates (vibrates back and forth) at a precise frequency: exactly 32,768 times each second. The circuit counts the number of vibrations and uses them to generate regular electric pulses, one per second. These pulses can either power an LCD display (showing the time numerically) or they can drive a small electric motor (a tiny stepping motor, in fact), turning gear wheels that spin the clock’s second, minute, and hour hands.” https://www.explainthatstuff.com/quartzclockwatch.html

https://electronics.howstuffworks.com/gadgets/clocks-watches/digital-clock2.html

A Short History of Digital Clocks and Watches

https://h2g2.com/edited_entry/A1006534

A Brief History of the Wristwatch – Part 1

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The wristwatch

While I was blathering about cars and roads, I got ahead of myself—I haven’t been talking about time for awhile. In the previous post I mentioned that satellites need incredibly precise clocks so that their signals are accurate when finding your global position. But the last time we looked at a clock was Harrison’s marine chronometer from 200 years ago.

The Queen of Naples wearing her wristwatch.

In 1810 the very first wristwatch was designed by Abraham-Louis Breguet for the Queen of Naples. Before that, a ‘watch’ meant a pocket-watch, kept in your pocket and attached to a button-hole in your vest by a chain. Instead of hauling a time-piece out of your pocket, now all you had to do was look at your wrist.

Nowadays nobody wears a wristwatch. When we want to know the time, we haul our cell phones out of our pockets. Progress!

A Brief History of the Wristwatch – Part 1


https://www.hallandladdco.com/blogs/interesting-articles/a-short-history-of-the-wristwatch

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Hot- and cold-running time

After breaking his heart trying to perfect a clock to keep accurate time on the high seas, Harrison refused to give up. He turned instead to perfecting a watch.

No more worrying about pendulums!* Harrison got straight to work on a ship’s timepiece that uses a metal spring and balance wheel. That good ol’ metal spring and balance wheel would do the trick. No problems with a metal spring and balance wheel, no sir.

Well, maybe one small problem. When metal is warm, it expands slightly. When it cools, it contracts. This spring-powered timepiece was expected to be used in both tropical and arctic conditions. The temperature would change the character of the metal, which would make it less reliable, which would make the timepiece less accurate.

Now what?

* Okay, okay, pendula for you Latin nerds.

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Watch works

You remember an escapement is a way of slowly releasing energy that powers a clock. A watch didn’t use a pendulum for its escapement—it used a coiled metal mainspring and balance wheel. You wind the spring tightly and the spring wants to unwind. As it unwinds, its energy is released to oscillate the balance wheel back and forth. As the balance wheel oscillates, it swings a little fork side-to-side which stops and releases a gear. This is the watch’s escapement. No matter how the watch is bounced around, the spring keeps on releasing energy at a steady, reliable pace.

The wound-up spring wants to uncoil, to expand. As it expands, it pushes and turns the balance wheel. But the balance wheel is weighted so it only turns so far and then it swings back. When the balance wheel swings back it tightens the spring again. The wound-up spring wants to uncoil, to expand. As it expands, it pushes and turns the balance wheel. But the balance wheel is weighted so it only turns so far and then it swings back. When the balance wheel swings back it tightens the spring again. (Repeat over and over and over and…)




https://sciencing.com/analog-clocks-work-4912745.html
https://www.jcwa.or.jp/en/time/qa/qa07.html
https://www.wixonjewelers.com/education-type/watch-movements/
https://malalan.eu/how-it-works-escapement/
This beautiful video has French narration but the visuals are self-explanatory: The escapement animation starts at 3:30.

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Keep on trying

With John Harrison’s innovations, his clocks were more precise than any clock had ever been. The bad news was: his clocks still weren’t precise enough to win the Longitude Prize. “The amount awarded under the Act was commensurate with the accuracy of the invention in determining longitude: 10,000 pounds for 1 degree, £15,000 for 2/3 of a degree, and £20,000 for 1/2 of a degree.”

Rather than give up, Harrison tried something different. Instead of designing a precision clock, he turned to designing a precision watch. A watch is an analogue or mechanical (not digital) timekeeping device small enough to carry around with you. You can hold one in your hand. People attached an end of a chain to their watch, attached the other end to a belt loop or button-hole and kept the watch in a pocket.

Random side-note: A pocket-watch and chain play a part in the O. Henry short story, The Gift Of The Magi. https://www.enotes.com/topics/gift-magi Spoiler alert! DON’T unlock the summary until you’ve had the pleasure of reading the story itself.

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The clockmaker

In our last post you saw how to find your location by observing the moon and stars to calculate lunar distance. The object is to know both your local time and prime meridian time, or Greenwich Mean Time. A navigator needs to be an astronomer and a math whiz to use this method.

You may have asked yourself, “Wouldn’t it be easier to keep 2 clocks aboard the ship—one showing Greenwich Mean Time and the other kept to local time?” That’s an excellent question and I’m glad you asked it. In fact, that’s the question John Harrison asked.

John Harrison, English inventor and horologist, 1767.

John Harrison was a cabinet-maker with a side business building and repairing clocks. To win the Longitude Prize, he went for a straightforward solution: build an accurate clock that always, ALWAYS showed precisely the correct time in Greenwich.

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Let me see what moons are like on Jupiter

The moons of Jupiter travel around her at a regular rate, like the hands of a clock. Galileo thought that you could use the moons as a universal clock. With that clock as a reference point, you could use local time to figure out where you are on Earth.

This sounds like a great idea, but how does it work? I’m guessing that you look at Jupiter, see where her moons are, and calculate where you are on Earth based on which moons you can see. For instance, on Wednesday, May 25, if you’re in North America and you have a telescope you can watch Io and Europa pass in front of Jupiter. If you live on the east coast you’ll see them only starting out; on the west coast you’ll see them only at the end. If you live in the middle of North America you’ll see most of the passage.

Since they know exactly when those moons will be zipping across the face of Jupiter and how long it will take, astronomers are able to make charts of the moons’ progress showing local times everywhere on Earth.

This strikes me as a huge amount of work to figure out where you are on Earth. Then again, I’m holding a cell phone with a GPS (Global Positioning System) so it’s pretty easy for me to know exactly where I am. If I were floating around in the ocean in the 1600s, with no GPS, I imagine I’d be pretty desperate to know exactly where I were and would consider breaking out the old telescope to have a squint at Jupiter and her moons.

https://solarsystem.nasa.gov/moons/jupiter-moons/overview/?page=0&per_page=40&order=name+asc&search=&placeholder=Enter+moon+name&condition_1=9%3Aparent_id&condition_2=moon%3Abody_type%3Ailike
https://www.space.com/11724-jupiter-moons-shadow-play-skywatching.html

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Like a pendulum do

One time while sitting in church, Galileo noticed a lamp suspended from the ceiling that was swinging back and forth. That motion is known as a pendulum. As it swung, he observed the lamp kept the same rate of speed. It occurred to Galileo that you could use a pendulum’s regular rate of speed to regulate a clock.

We learned that in Galileo’s time a clock was powered by a weight that slowly released its energy as it was pulled to Earth by gravity. The mechanism that slowed down—regulated—the weight’s energy is called an escapement. Galileo thought to replace the verge and foliot escapement with a pendulum escapement.

Just like the verge and foliot, as the pendulum swings back and forth it allows a gear to move forward a little bit just before a pawl stops it—until the pendulum swings to the other side. The pendulum escapement releases-stops-releases-stops the gears as they move the hands of the clock. Here is an excellent animation of Galileo’s escapement. Notice how when the gear turns it gives the pendulum a teensy little push.

https://www.history.com/topics/inventions/galileo-galilei
http://www.cs.rhul.ac.uk/~adrian/timekeeping/galileo/

Watch this guy make a wooden pendulum clock: https://www.youtube.com/watch?v=rvU37Aho4FA

Here’s some terrible music:

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The amazing fantastic clock of Piazza San Marco

In 1493, the Venetian Republic commissioned the clockmaker Giovan Paolo Rainieri, from the town of Reggio Emilia, to design and build a clock. This clock would be big and beautiful and expensive—a tower would be designed and built on Saint Mark’s Plaza to house it. It would face the lagoon and the sea beyond, so the whole world could see how prosperous was Venice.

If you visit Venice you can see the Rainieri clock. Its face is decorated in gold and lapis lazuli (a mineral you make blue out of—blue paint ain’t cheap); the hand tells what hour it is and the current zodiac sign; above the clock is a statue of the Virgin Mary and Baby Jesus (made of gilded copper); twice a year a mechanical angel and three wise men parade in front of Mary and tip their crowns to her; above Mary is the lion of Saint Mark with his paw on the Gospel (the statue of the praying doge isn’t there anymore); and at the top, every hour two bronze giants ring an enormous bell with their hammers.

The entire contraption from top to bottom used a verge and foliot escapement to regulate the gears.

https://www.atlasobscura.com/places/torre-dell-orologio-venice-clock-tower
https://en.wikipedia.org/wiki/St_Mark%27s_Clock

https://en.wikipedia.org/wiki/St_Mark%27s_Clocktower

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