Tag Archives: time

Einstein’s Special Theory of Relativity


As you move faster, time slows down for you. Even though that’s true when you’re riding in a car, the slowdown is so teeny-tiny that it’s not worth measuring. But, if you were to travel to another galaxy at almost the speed of light, time would slow down—for you—to the point where you would age more slowly than your pals back on Earth.

When you got back from your trip, your friends would be old and wrinkly but you’d be ready to graduate from high school.

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Einstein

So atomic clocks saved the day—yay! Satellites are synchronized with each other to nanosecond accuracy. Their signals let our GPSs figure out where we are because even though those satellites are hurtling through space at 17,000 miles per hour, their atomic clocks will always show the correct time, right? Nothing’s gonna interfere with each satellite’s time, nothing! No sir! Not one thing!

Okay, maybe one thing: Einstein.

I can see you loyal-yet-exasperated readers flinging your half-eaten peanut-butter-and-jelly sandwiches across the room and yelling, “Oh, come off it, Manders! Have you finally gone around the bend? Should we have you fitted for a straight-jacket and a drool-cup? What’s Einstein got to do with my global positioning system?”

Listen, and I will tell you all about it.

Feedback loop

A cesium atom oscillates 9,192,631,770 times every second. That never changes.

What does change is the atoms’ energy state. The excited cesium atoms bounce off the detector every time the microwaves hit the same frequency as the atoms’ oscillations. The detector sends a signal to the microwave resonator, so that the microwave frequency is adjusted to sync better with the atoms. This is called a feedback loop. The detector sends a signal, the signal adjusts the microwave frequency, the microwaves excite the atoms, the atoms bounce off the detector, the detector sends a signal, the signal adjusts the microwave frequency, the microwaves excite the atoms…over and over and over. The time between each signal is exactly one second. No gears, no moving parts to oil, nothing mechanical.

That’s it! That’s how the atomic clock works. Thanks for sticking with me for an entire week on this. Finally, we can get on with our lives!

As with my explanation of the liquid crystal display, this is a simplification. I left out a lot of stuff. It’s the idea, the principle, that I was interested in explaining. Luckily for you, here are links to click on if you’d like more exact, in-depth info about atomic clocks.

https://www.livescience.com/32660-how-does-an-atomic-clock-work.html
https://www.timeanddate.com/time/how-do-atomic-clocks-work.html
https://www.gps.gov/applications/timing/


https://science.howstuffworks.com/question40.htm
https://www.fda.gov/radiation-emitting-products/resources-you-radiation-emitting-products/microwave-oven-radiation
https://science.howstuffworks.com/atomic-clock3.htm
https://www.britannica.com/technology/atomic-clock

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Atomic Clocks

We’re now at the point where we can talk about…atomic clocks, which lose only one second every 100. Million. Years. Yay!

What is an atomic clock and how does it work? That’s an excellent question. Honestly, I have no idea. You would think, as an adult grown-up-type guy, I’d know something like that. I don’t. I avoided science classes in school so I could hang out in the art room.

I don’t know how you get atoms to float around in a tube so you can zap ‘em with radio waves until they change into a different energy state and bounce off a detector that counts the atoms in their new changed state and funnels the whole mess into a feedback loop…

I need to go away for a few days and marinade myself in sciency research until I figure this one out. I’ll be back. In the meantime, please enjoy this hold music—

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32,768 oscillations per second

When you hit a tuning fork against something it vibrates, giving a specific musical note.

We learned that a digital clock is regulated by measuring how many times a quartz crystal oscillates per second—32,768 times. How does it count all those vibrations so quickly? Here’s how: the crystal is purposely cut with a laser to exactly the size and shape (the shape of a tuning fork) that will produce 32,768 oscillations in a second, then stop.* The electric circuit zaps the crystal with electricity, which makes the crystal vibrate until it returns to its original shape. When the vibrating stops, exactly one second has passed. The stopped vibrations trigger the circuit to move the second hand and give the crystal another zap.

The same principle applies in animated entertainment for children. The mouse hits the cat, who oscillates for a second, then resumes his former shape.

Here’s how a tuning fork works: https://www.youtube.com/watch?v=hW-igtIn3A8

Basics of LC oscillators and their measurement


https://en.wikipedia.org/wiki/Crystal_oscillator

* “Because 32768Hz can be so conveniently divided to give a 1 second pulse, it is a very popular size for it to be cut to. Manufacturers can bang them out and be sure they will sell.” https://www.quora.com/Why-does-Quartz-vibrate-exactly-32768-2-15-times-per-second

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The liquid crystal display explained!

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.

Okay, I sort of explained how a battery works. I kind of explained how a quartz crystal works. The circuit board was easy—even a shmo like me can explain printed metallic ink on a plastic card. But—liquid crystal display? I started this post about 17 times and kept getting lost in the weeds with carrot juice and double melting points and twisted nematics and polarization…

Let’s start here: analogue clocks and watches were inaccurate because they have physical, mechanical moving parts. So we replaced the wound-up mainspring with a battery. We replaced the balance wheel with a vibrating quartz crystal. Now we need to replace the moving mechanical gears, hour-hand and minute-hand with a digital (just the numbers) display of the correct time. How do we do that?

A digital wristwatch made by the Japanese company Casio.

Instead of mechanical gears and hands, we’re going to use electricity and light.

We want a watch-face that will light up and show us what time it is. We want most of the face to light up except the numbers, which should be black so we can read ‘em easily. We’ll block the light in the shape of each number so it shows up black. The numbers will change every minute, so we need a way to change the blocked areas every minute.

In order to block the light, we need a filter. The filter lets us control which rays of light pass through and which rays get blocked. A filter could be a wall of liquid filled with crystals that all face the same direction. The lined-up crystals let the light pass through. We’ll sandwich this wall between 2 plates of glass. The crystals still let light pass through—until we zap them with a little electricity. The electricity upsets the crystals so they don’t line up anymore and light can’t pass through.

We’re only going to zap in certain areas. We want those certain areas to be shaped like numbers. For instance, when we zap the glass in the shape of a ‘3,’ those crystals in the 3-shape get upset and don’t line up with the rest of the crystals in the wall. Light can’t pass through the 3-shape, so we see a black ‘3’ on a lighted watch-face.

Just like on a circuit board, we’ll print the numbers onto the glass in ink. This ink is transparent—and it conducts electricity. Each number is designed as a 7-segment figure, so we can zap only the segments that form a ‘3,’ or whichever number we want. Each segment is wired to the battery.

This is the principle behind LCDs. It’s a simplification. I left out a lot of stuff. But you get the idea, right?


https://electronics.howstuffworks.com/lcd.htm
https://electronics.howstuffworks.com/gadgets/clocks-watches/difference-between-quartz-and-liquid-crystal2.htm
http://www.madehow.com/Volume-1/Liquid-Crystal-Display-LCD.html

Many thanks to a couple of the Western Civ Irregulars, Diana (Ms Physics) and engineering-wiz Don M—both pals of mine since childhood. They pointed me in the right direction when I couldn’t find a way to explain this one.

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Circuit boards

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.

This will look better when I paint it. For one thing, the board will be a lovely green. The bigger, more complicated circuit boards look like city maps.

If you’ve ever wired something—like a lamp—you’ll remember getting out the needle-nose pliers and wire-cutters, maybe a razor blade to strip the insulation off the wire ends; you wrap the exposed copper wire around the appropriate screws then tighten ‘em up so the wire stays put…I’m trying to imagine how you would wire something as minuscule as the insides of a watch. Wires would need to go from the battery to the quartz crystal, back to the battery with a detour to power the hour, minute & second hands after counting how many oscillations the crystal made.

The circuit board is a flat card made of plastic or resin. Instead of wires, circuitry is printed right onto the card in metal ink. A circuit board can get a complicated electric network crammed onto a very small area. A small circuit board in a watch can direct electric power from a battery to the quartz crystal and anything else inside the watch .

You can see the circuit board at 27:20 https://www.youtube.com/watch?v=SFiq8WDx5Is

The History of Circuit Boards


https://www.pcb-solutions.com/pcb-market-monitor/the-history-of-pcb-infographic/
Those old discarded mass-produced watches and circuit boards can become playthings for someone with electrical knowledge—http://www.angelfire.com/ut/horology/quartz.html
https://sound-au.com/clocks/timebase.html

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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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WWI flying aces and wristwatches

For a long while, wristwatches were thought to be fashionable for ladies only. The guys stuck with their pocket watches—until the First World War. WWI was the first time airplanes were used in combat. Sometimes several airplanes were used for a coordinated attack, which meant they had to arrive at the target at the same moment. When you’re hundreds of feet in the air, working a joystick and firing a machine gun, you don’t have enough hands to also pull out your pocket watch to see if you’re on time (why didn’t they put a clock in the plane’s dashboard? I don’t know).

Does this happen to you? I started out drawing a wristwatch-wearing WWI fighter-pilot and he turned into Joe Kubert’s angst-riddled Enemy Ace Hans Von Hammer and his puppy, Schatzi.

Likewise, if infantry soldiers in the trenches were ordered to open fire on the enemy simultaneously at a pre-planned time, a timepiece on your wrist is a whole lot more convenient than one in your pocket to count down the seconds while you’re holding a machine gun and a shovel.

So designers began designing manly-looking wristwatches for the guys.

https://gallantry.com/blogs/journal/the-history-of-watches#
https://www.watchmaster.com/en/journal/stories-en/the-history-of-the-wristwatch

https://en.wikipedia.org/wiki/Enemy_Ace

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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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