Where Did Measurements Come From?
- Wednesday, January 24, 2007
Have you ever wondered where our measurements came from? Is it really true that a ruler is a foot long because it's about as long as a man's foot? If that's true, then back in the days before rulers, did a man with big feet build larger things than a man with small feet?
For years, researchers have speculated that ancient people had consistent measurements (no matter how big a man's feet were!). And yet, evidence indicates that these past civilizations did not have measuring equipment--or at least, none that they kept for very long. At the most, they appear to have had measuring rods that would have been discarded at the end of a building project. So how did they get consistent measurements?
According to the book Civilization One, ancient civilizations devised a system of measurement based on pendulums and the passage of time as measured by astronomy. It's a deep subject, but by the end of this article, you'll know how to create your own measuring system with nothing more than a piece of string, a rock, and time!
To start with, a pendulum is a weight, or bob, suspended by a rod or a string, so that it can swing freely back and forth under the influence of gravity. You can make a pendulum just by tying a rock to a piece of string.
The first thing you need to remember about a pendulum is that it needs to swing freely. That means it moves because of gravity and not because you push it. To use your pendulum, pull the bob back, keeping the string taut. Gently release the bob (don't push it) to allow the pendulum to begin swinging. Each swing is called a sweep. The farther back you release the bob from, the longer the sweeps will be.
Second, strange to say, a pendulum will make the same number of sweeps in a specified period of time regardless of the length of the sweep, and regardless of the weight of the bob. So, if you took a two-foot piece of string with a one-pound bob, and released it from a high height, it would make the same number of sweeps in thirty seconds as a one-ounce bob released from a lower height.
Now here's the most important thing. The only factor that affects how many sweeps the pendulum will make in a specified time period is the length of the string. So if you have a one-pound bob on a two-foot string, it will make more sweeps in thirty seconds than the same bob on a three-foot string.
That's all for theory--now let's get to the hands-on stuff! We have a few experiments to try, but first, you'll want to gather a few things:
- A roll of string
- Two weights, one light and one heavier, to use for bobs (keyrings might work well).
- Some steady object to hang pendulums from, where there's room for them to swing. Some ceiling light fixtures work well, or exposed beams in a garage or unfinished basement.
- A timer or a clock with a second hand.
To start with, make two pendulums by tying a piece of string to each weight (bob). Hang the pendulums side by side, making sure the strings are exactly the same length. Now, take a bob in each hand, pull them both back an equal distance, and let go. Count the sweeps for thirty seconds. Although the bobs are different weights, you'll find they make the same number of sweeps.
Now, try the same experiment, except this time, pull the bobs back different distances. Count the sweeps for thirty seconds and you should find that they're still the same, even though one pendulum had to travel farther on each sweep. Therefore, neither the length of the sweep, nor the weight of the bob, makes any difference in how many sweeps a pendulum will make in a given time period.
Finally, shorten one string by about one half, and again count the sweeps for thirty seconds. This time, you'll find that the pendulum with the shorter string made more sweeps. This proves that the only thing to affect the number of sweeps in a period of time is the length of the string.
Now let's take this backwards. You know a pendulum will swing at a constant rate, regardless of the length of the sweep or the weight of the bob. So, if you wanted to create a uniform system of measurement, with the ability to make your own "ruler" any time and know it would be the same length as the last one, how could you use pendulums to reach your goal? Stop and think about it for a few minutes before going on to the next paragraph . . .
In case you couldn't quite figure it out, the answer is this: Make a pendulum, any pendulum, and count the sweeps for a specified period of time. Suppose your pendulum makes fifteen sweeps in thirty seconds. Now, anytime, anywhere, you can get a piece of string exactly the same length as the first one, just by experimenting with different lengths until you get one that makes fifteen sweeps in thirty seconds.
So, the length of that string could now be the basis of a new system of measurement! You could easily make your own "yards," "miles" and "inches" based on this new unit of measurement--but what if you needed a measurement of volume, such as a gallon or a quart? Just make containers that are the same length on each side as your trusty piece of string, and presto! A whole new system of measurement, all your own --and remember, you could duplicate the whole thing any time you wanted, with nothing but a piece of string, a weight, and a reliable way to time the sweeps!
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