Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff, it's Christian Seger in. Today's question is why do we measure time the way we do? At the first glance, it seems like it's a sensible thing until we start delving into it. So let's start with a day. What is a day? A day is just the amount of time that it takes our globe to make a full
rotation on its axis. Simple, right, But then we divide a day into twenty four parts for some reason, and then of those twenty four hours we measure those in sixty minute increments for some reason. And then we get down to a minute, we measure that in terms of seconds, again a collection of sixty for some reason. But when we get to seconds, we measure those in the most popular numerical system today, the decimal system, So we talk in terms of a hundredth of a second or a
millionth of a second. But why how do we even start measuring days and dividing them this way? Well, the Babylonians were measuring time in what's called a sexy gesimal system as opposed to a decimal system. They were based on sixty instead of base ten, So earlier we said that the decimal system is the most popular, and it makes sense right because the vast majority of human beings have ten fingers. It's very easy for the human species
to count to ten. So why would you use something that relies on sixty or why would you use something that relies on twelve. Well, when we look at the Babylonian system, it actually makes some sense. There is some method to this ancient madness. And here's why. If we use the base ten idea ten to one hundred, the notation that we would have to make to measure a specific time of day would become ridiculous very quickly, and
complicated as well. The thing is that sixty has some advantages because sixty, if you just break it down, is essentially five times twelve. Then it has both the advantages of a ten and twelve as a system. So that is why it makes sense for us to use sixty seconds in sixty minutes. But the big explanation that no one's figured out yet is how this spread around the world. Did it happen because it was an accident of history?
Did it happen because it was really the most efficient way that human beings have figured out how to measure time. And one last thing. We're all familiar with AM and PM, right. AM stands for anti meridium and PM stands for post meridium. These are terms that came about during the Roman era when they used to divide the entire day into two things,
just AM and PM. This was so important, in fact, that they used to have these people whose only job was to wait until the sun crossed over so they could run to the forum and say, every buddy, okay, it is noon. It is officially p M. And the reason why is because lawyers were required to show up by noon. Check out the Brainstuff channel on YouTube, and for more on this and thousands of other topics, visit how stuff works dot com.