ORIGINS: The Second
Some things are essential to our everyday lives, yet their ORIGINS have escaped us. The names of the days of the week? The months? Our "Arabic" numeral system? Giving someone the
bird? 60 seconds in a minute? What defines the length of a second?
The game of chess? It goes ON and ON... HAWTaction [hot ak-shuh
n] will bring you those histories in ORIGINS.
Time is fascinating. It's a man-made concept that is the structure of our existence, from measuring the span of a lifetime to arranging the simplest of habitual practices. Its importance is undeniable; every civilization has had a form of it. Like language, it is an inevitable necessity. Looking at the diversity of historic calendar systems - with their proprietary days, months, seasons - it's amazing that we've got any standards at all. But we do! (YAY?) We have the global standard of 12-month years and 7-day weeks.
Also? The second. I find this to be the most arbitrary global standard, because (I believed) it's the standard all others are built on. A minute is built on the length of a second. Hour on that of a minute... So, it all goes back to a second. (Or does it?) But how did we decide how long a second should last? As a child I imagined people created it by going, "A second should last.... THIS... much." "No, it should last... THIIIS... much." The ORIGINS of the second are little more complicated. (Or are they?)
n] will bring you those histories in ORIGINS.The Second
Time is fascinating. It's a man-made concept that is the structure of our existence, from measuring the span of a lifetime to arranging the simplest of habitual practices. Its importance is undeniable; every civilization has had a form of it. Like language, it is an inevitable necessity. Looking at the diversity of historic calendar systems - with their proprietary days, months, seasons - it's amazing that we've got any standards at all. But we do! (YAY?) We have the global standard of 12-month years and 7-day weeks. Also? The second. I find this to be the most arbitrary global standard, because (I believed) it's the standard all others are built on. A minute is built on the length of a second. Hour on that of a minute... So, it all goes back to a second. (Or does it?) But how did we decide how long a second should last? As a child I imagined people created it by going, "A second should last.... THIS... much." "No, it should last... THIIIS... much." The ORIGINS of the second are little more complicated. (Or are they?)
This whole thing starts with the Ancient Egyptians. As far back as 2,000 B.C.E., they were splitting their days and nights into 12-hour segments. The daylight segments were measured with a sundial and the nighttime ones by the movement of the stars. Simple, but I'm still trying to find out where this twelve came from. It could easily have been twenty or eight, but I think it has something to do with the fact that the Egyptians used a base 6 number system. (If anyone has the answer to this "twelve," please post in comments!)
The system would provide a sliding system with daytime hours in June lasting longer than those in December. (Oh, those seasons...) If you're building pyramids, that simple system might work, but if you're building hanging gardens, you might need something a bit more... sophisticated? The Babylonians took that 24 hour day idea, and started splitting it sexagesimally, which means, 1/60th. AH! You might recognize that breakdown: breaking hours into segments of 60, then each of those segments into 60? Sound familiar? But where did this "sixty" come from?
Just as we have a base 10 number system now, there are a number systems with different bases: 2 (for computers), 5, 6 (Egyptians), 12, 20 (Brittany, France), 60... Well, in 2,000 B.C.E., the Sumerians used a base 60 number system. (I know what you're thinking: They used that random system, and now it is ALL OVER OUR LIVES. Darnit.) The base-60 system traveled from Sumeria to Babylonia, setting the standard there. It was no surprise, then, when they wanted to break down the Egyptian's 24 hour day, they used the 1/60th fraction. (Surely, this splitting hours into 1/60 also came to Egypt, but it was the Babylonians who spread the system around the world.)
So, here's the funny thing. Those Babylonians? They could use decimals to calculate solar events to the exactness of 2 microseconds. The odd thing? They had no way to measure these intervals. So, they could compute their year to 2 microseconds, but couldn't measure it. Wow.
The system pushed through Europe and Asia, setting the global standard. And it remained that way, too, with the day being split into 24 hours, hours split into 60 minutes and minutes split into 60 seconds. In other words, the second was defined as 1/86,400 of a day.
I guess I was wrong in thinking the second was the building block the minute and hour are built on. It was always the day that was the standard, and the second defined as a fraction of it. How cute. The problem is that, because we revolve around the sun elliptically, there are some days that are longer than others depending on how far we are from the sun. We aren't talking about variable daylight hours anymore, now we're talking about variable lengths of days. So, how to get around this?
In 1956, the standard day length was, essentially, defined as that of a certain "epoch." The second, therefore, was defined as "the fraction 1/31,556,925.9747 of the tropical year for 1900 January 0 at 12 hours ephemeris time." I don't want to even try to understand that babble, and scientific community wanted nothing to do with it, either. The second they had another option, they seized it: the atomic clock.
The atomic clock changed it all. First developed in 1955, it wasn't until the 1970's that it was used to set the time standard. Now science didn't have to deal with "median epochs" to define the standard day length, and, therefore, the second. The world could now use something reliable, like cesium, a metal that's liquid at room temperature (like mercury) that "vibrates" on a very consistent basis. Count the transitions that provide those vibrations, and you've got a second. Current definition: The second is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom. Count just over nine million of these transitions, and you have a second. Done.
So, thems the ORIGINS of the second, people. Recap: Egyptians used 24-hour day, Babylonians split the hours by 1/60 and 1/60, then the cesium atomic clock allowed them to set a standard that doesn't depend on the variable length of a day.
There. You learned something.
The second? Another one of the ORIGINS explained on HAWTaction [hot ak-shuhn].
The system would provide a sliding system with daytime hours in June lasting longer than those in December. (Oh, those seasons...) If you're building pyramids, that simple system might work, but if you're building hanging gardens, you might need something a bit more... sophisticated? The Babylonians took that 24 hour day idea, and started splitting it sexagesimally, which means, 1/60th. AH! You might recognize that breakdown: breaking hours into segments of 60, then each of those segments into 60? Sound familiar? But where did this "sixty" come from?
Just as we have a base 10 number system now, there are a number systems with different bases: 2 (for computers), 5, 6 (Egyptians), 12, 20 (Brittany, France), 60... Well, in 2,000 B.C.E., the Sumerians used a base 60 number system. (I know what you're thinking: They used that random system, and now it is ALL OVER OUR LIVES. Darnit.) The base-60 system traveled from Sumeria to Babylonia, setting the standard there. It was no surprise, then, when they wanted to break down the Egyptian's 24 hour day, they used the 1/60th fraction. (Surely, this splitting hours into 1/60 also came to Egypt, but it was the Babylonians who spread the system around the world.)
So, here's the funny thing. Those Babylonians? They could use decimals to calculate solar events to the exactness of 2 microseconds. The odd thing? They had no way to measure these intervals. So, they could compute their year to 2 microseconds, but couldn't measure it. Wow.
The system pushed through Europe and Asia, setting the global standard. And it remained that way, too, with the day being split into 24 hours, hours split into 60 minutes and minutes split into 60 seconds. In other words, the second was defined as 1/86,400 of a day.
I guess I was wrong in thinking the second was the building block the minute and hour are built on. It was always the day that was the standard, and the second defined as a fraction of it. How cute. The problem is that, because we revolve around the sun elliptically, there are some days that are longer than others depending on how far we are from the sun. We aren't talking about variable daylight hours anymore, now we're talking about variable lengths of days. So, how to get around this?
In 1956, the standard day length was, essentially, defined as that of a certain "epoch." The second, therefore, was defined as "the fraction 1/31,556,925.9747 of the tropical year for 1900 January 0 at 12 hours ephemeris time." I don't want to even try to understand that babble, and scientific community wanted nothing to do with it, either. The second they had another option, they seized it: the atomic clock.
The atomic clock changed it all. First developed in 1955, it wasn't until the 1970's that it was used to set the time standard. Now science didn't have to deal with "median epochs" to define the standard day length, and, therefore, the second. The world could now use something reliable, like cesium, a metal that's liquid at room temperature (like mercury) that "vibrates" on a very consistent basis. Count the transitions that provide those vibrations, and you've got a second. Current definition: The second is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom. Count just over nine million of these transitions, and you have a second. Done.
So, thems the ORIGINS of the second, people. Recap: Egyptians used 24-hour day, Babylonians split the hours by 1/60 and 1/60, then the cesium atomic clock allowed them to set a standard that doesn't depend on the variable length of a day.
There. You learned something.
The second? Another one of the ORIGINS explained on HAWTaction [hot ak-shuh
n].Join the HAWTaction reader group on Facebook.
Wow, great research.
It takes me 27,577,895,310 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom to clear our a room after eating alot of cheese.
I'm the sassiest commenter, ever.
Si, Jason. Tu eres!