Time is often called the fourth dimension. The other three being length, width, and height. Those are easy to measure. Pick up anything, declare its length to be the standard unit and start holding it against objects. You can even do that several times or at any time you wish.
Time is different in that way. How do we measure time? We compared the other dimensions to something within that dimension. Can we do the same with time? How do you hold another time next to the timeframe you want to measure? And even if we manage to do that, can we do it again and again or at any time we chose?
We started to name recurring events. The most prominent one in nature being the day. Some cultures define a day from sunrise/set to the next sunrise/set, some from noon (sun reached highest place) to noon and some the direct opposite, from midnight to midnight (sun at noon on the direct other side of the earth).
A day is pretty long, if you want to measure short events during the day. Another unit was needed and we divided the day into 24 hours. This goes on, we get 60 minutes per hour and 60 seconds per minute. That was enough for the everyday life for hundreds of years. Then we got into milliseconds and nanoseconds because technology needed more precise measuring.
After we cleared this up, let us start a journey into some fun facts of measuring time.
Why do we have 24 hours and not 10 or 20? And why do we have 60 minutes/seconds and not 100?
Because we, as human kind, started measuring time way before the introduction of the metric system. And even though most children do count with their fingers and reach the number 10, most adults realized there is a “better” way of counting with your hands.
Using the thumb as an index you can count three bones per finger. Assuming no heavy injuries you can count to 12 with one hand that way. The 12 became the focal point for most number based interactions between humans. If you use two hands you can count to 24. If you use the bones method on one hand and count with fingers on the other the amount of “round trips” you already made on the 12-base hand, you can count to 12 * 5 = 60. And 12 * 12 = 144 being named a gross comes from using one hand for 1-12 and the other as a factor reminder, how many times you already counted.
Here we are, having 24 hours per day and 60 minutes and seconds. Additionally the number 24 has a lot of divisors. You can easily divide it by 2, 3, 4, 6, 8, and 12. We’re missing the 5 and 10 most prominently. That is why the hour is divided into 60 minutes. We got the 5 and 10 in there, as well as 15, 20, and 30. Sadly, the 8 had to go again. But if you put the minutes and hours together, we not only see the gross again, we can now also divide by all those other numbers we missed so far. We got 1440 minutes per day and can easily chop them up in smaller parts without resorting to fractions.
When we started to worry about even smaller amounts of time, it was more for scientific research. Since the metric system is most prominent in science, it was logical to use it for the smaller time units, so we introduced milli and nanoseconds.
That is easy. We just said, one day is 24 hours (which in turn is 1440 minutes and so on). Yes, as long as you follow the above definition. But there is always someone who tells you “The time it takes the earth to make one full rotation.”
Nope. Welcome, to fun fact number 2.
Let us imagine we are watching the earth from orbit. We look down at the north pole and the earth turns counter clockwise. Isn’t that ironic, we measure time based on earth rotation but the clock turns the other way around? Anyway, the sun is left to the earth in this mental picture, directly shining on any spot you chose. Let’s take Greenwich since it’s the 0° meridian anyway. Now we take a full rotation. But the sun is not shining directly at Greenwich. Just a small angle is missing for the high noon. Why? Because the earth is also rotating around the sun. Ironically counterclockwise again. It moved up (and slightly to the left) a little bit. A full earth rotation “only” takes 23 hours, 56 minutes and (rounded down) 4 seconds. The other 3 Minutes and 56 seconds to get the complete 24 hours are needed to compensate for the earth rotating around the sun.
You can experiment with it at home. Put a lamp in the middle of the room. That will be the sun. Sit in an office chair facing the lamp. You are now the earth. Rotate on your own axis while also rotating the chair around the lamp. Both counter clock wise. For a better demonstration make it a quarter of a circle “per day”. The angle you moved around the lamp (in this case 90 degrees) needs to be compensated by you adding to your full rotation those 90 degrees.
So the angle the earth moves around the sun while performing a full rotation must be added to its own rotation to compensate and put the sun at the same position in the sky. And that is what we call a day and divided it into 24 hours and so on.
Which brings us to fun fact number 3. Even though a year is 365 days long (forget about leap year for a second), the earth moves completely around the sun and every day we have to add the small extra angle to its own rotation meaning: Within one year this adds to one extra rotation hence the earth rotates 366 times in one year.
Sadly, it’s not that easy. We didn’t quite make it. Let us put leap year back on the table. What are we actually doing in a leap year? We add one extra day every 4 years. Why? Because every year we miss the complete rotation around the sun by roughly 6 hours. No worries, February for the rescue. At least so we thought for a few hundred years until 1582. To a few of my readers, this year might sound familiar. You are about to learn why.
We are missing 5 hours, 48 minutes and 45 seconds per year for the full rotation around the sun. Give or take a few milliseconds. By adding one extra day every 4 years we actually miss by 45 minutes again. That is not too bad you might think and so did most of humanity. But in the 16th century we realized that 45 minutes in 4 years means more than 18 hours per century were piling up all the time. So they did some calculations and the result was to eliminate those 18 hours every century by declaring that every year ending on a double zero would not be a leap year even though it can be divided by 4.
Hey, wait a minute. If you did the math, you might have realized: We are still 6 hours off every century. No problem, every 4th time this rule shall be ignored, meaning: If it ends on 00 it is no leap year except for those years that can be divided by 400. That is why 1900 was no leap year but 2000 was and why 2100 will not be.
It is still not exact but the difference is now so small, it should keep us safe for a few thousand years or so.
But the damage was already done. To correct the error the year 1582 was special. Pope Gregor not only signed the new rules for leap years but also declared that in that year after Thursday, October the 4th the Friday should be October the 15th. We just skipped 10 days because this problem was actually introduced into the calendar way before the year 0. The church needed the equinox (day and night being exactly the same time length) to be on march 21st for the clerical calendar to match up with the numerical calendar.
Most people in that time had no use for the exact date. Most important was the day of the week. Common folks just needed to know whether to work or (on Sunday) go to church. Because that order was not disturbed, a lot of people did not even notice the change because they only were told the exact date for specific events in church and seldom kept count every day.
But nowadays we all keep track of the exact date.
We also keep track of the exact time of the day. Well, sort of. At least to the second. So when Phileas Fogg traveled around the world in 80 days he insisted on adjusting his watch to the local time zones. He also kept track of the date and wrote a journey. By traveling east, with the rotation of the earth, he “lost” one hour every time he entered a new time zone. He had to turn his clock forwards because the sun rose earlier for him compared to his start/end point London. After one complete trip around the world his travel log showed 80 days. That his because he saw the sun rise 80 times. But sadly, he was 5 minutes over the deadline that day. So he thought.
During the same time period the sun rose only 79 times in London. He thought he lost his bet when in fact he won. Luckily his servant Passepartout realized the mistake and explained it to him.
Now imagine you make a round trip heading west. The story would not have had such an exciting ending. The same time passed but he would have only 79 days in his journal. With every timezone he would have "gained" an extra hour. With an extra day to spare he would have realized he had just barely won. Even worse, maybe he would have waited to the next day, thinking there's one day to spare. And then he would have lost his bet.
Hooray for the narrative genius of Jules Verne.
Let's give some room here for the spoiler sensitive.
Now we can declare:
I hope you enjoyed these little nuggets I found during my research over the years. I want to give a big thank you to Dreemport for hosting this month’s events. I was finally able to put this knowledge to use.
This post was written as an entry to the Dreem-WOTW: Time Contest.
See you all next time.
Header image from pixabay
Earth-Sun image designed by me with free elements in Canva
Edit: Ooops, I wrote "... skipped 10 years ..." which is now corrected and reads "... skipped 10 days ..."
