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Speaker 1: Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff,

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Speaker 1: it's Christian Seger in. Today's question is why do we

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Speaker 1: measure time the way we do? At the first glance,

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Speaker 1: it seems like it's a sensible thing until we start

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Speaker 1: delving into it. So let's start with a day. What

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Speaker 1: is a day? A day is just the amount of

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Speaker 1: time that it takes our globe to make a full

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Speaker 1: rotation on its axis. Simple, right, But then we divide

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Speaker 1: a day into twenty four parts for some reason, and

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Speaker 1: then of those twenty four hours we measure those in

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Speaker 1: sixty minute increments for some reason. And then we get

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Speaker 1: down to a minute, we measure that in terms of seconds,

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Speaker 1: again a collection of sixty for some reason. But when

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Speaker 1: we get to seconds, we measure those in the most

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Speaker 1: popular numerical system today, the decimal system, So we talk

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Speaker 1: in terms of a hundredth of a second or a

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Speaker 1: millionth of a second. But why how do we even

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Speaker 1: start measuring days and dividing them this way? Well, the

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Speaker 1: Babylonians were measuring time in what's called a sexy gesimal

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Speaker 1: system as opposed to a decimal system. They were based

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Speaker 1: on sixty instead of base ten, So earlier we said

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Speaker 1: that the decimal system is the most popular, and it

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Speaker 1: makes sense right because the vast majority of human beings

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Speaker 1: have ten fingers. It's very easy for the human species

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Speaker 1: to count to ten. So why would you use something

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Speaker 1: that relies on sixty or why would you use something

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Speaker 1: that relies on twelve. Well, when we look at the

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Speaker 1: Babylonian system, it actually makes some sense. There is some

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Speaker 1: method to this ancient madness. And here's why. If we

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Speaker 1: use the base ten idea ten to one hundred, the

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Speaker 1: notation that we would have to make to measure a

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Speaker 1: specific time of day would become ridiculous very quickly, and

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Speaker 1: complicated as well. The thing is that sixty has some

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Speaker 1: advantages because sixty, if you just break it down, is

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Speaker 1: essentially five times twelve. Then it has both the advantages

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Speaker 1: of a ten and twelve as a system. So that

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Speaker 1: is why it makes sense for us to use sixty

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Speaker 1: seconds in sixty minutes. But the big explanation that no

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Speaker 1: one's figured out yet is how this spread around the world.

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Speaker 1: Did it happen because it was an accident of history?

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Speaker 1: Did it happen because it was really the most efficient

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Speaker 1: way that human beings have figured out how to measure time.

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Speaker 1: And one last thing. We're all familiar with AM and PM, right.

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Speaker 1: AM stands for anti meridium and PM stands for post meridium.

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Speaker 1: These are terms that came about during the Roman era

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Speaker 1: when they used to divide the entire day into two things,

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Speaker 1: just AM and PM. This was so important, in fact,

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Speaker 1: that they used to have these people whose only job

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Speaker 1: was to wait until the sun crossed over so they

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Speaker 1: could run to the forum and say, every buddy, okay,

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Speaker 1: it is noon. It is officially p M. And the

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Speaker 1: reason why is because lawyers were required to show up

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Speaker 1: by noon. Check out the Brainstuff channel on YouTube, and

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Speaker 1: for more on this and thousands of other topics, visit

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Speaker 1: how stuff works dot com.