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Chapter 1: Why does the month of May have 31 days and June have 30?
Hello, and thanks for downloading the More or Less podcast, with a programme that looks at the numbers in the news, in life, and in ancient Maya calendars. And I'm Tim Harford. Last month, the UK's Met Office recorded a temperature of 35.1 degrees Celsius from a sensor at London's Kew Gardens. This was, the press reported, the hottest May Day since records began.
a couple of our listeners got in touch to point something out. While 35.1 degrees seems like a sensible, rigorous way of measuring temperature, the month of May feels like an arbitrary way to record time.
This record was set quite late in the month, on the 25th of May. That made me wonder whether calendar months are always the most meaningful way to compare temperatures.
When meteorologists start quoting records in arbitrary periods such as the month of May, wouldn't it be better to narrow down these periods to more manageable and equal bytes? So, months, eh?
What's going on there? To find out more, I spoke to Kristen Lippincott, former director of the Royal Observatory at Greenwich and author of The Story of Time. Well, welcome to More or Less. Thank you. Now, our listeners have asked if May, the month of May, is an arbitrary way to measure time. Is it?
Well, yes and no. It is arbitrary in that May is just a name for a group of days put together. But the idea of May and the idea of having a seasonal calendar goes way, way, way back to prehistoric times. So what were these prehistoric calendars like? The first reason why you would have a calendar is basically for survival. It would be tracking the changes in environment, in climate.
For example, you'd want to know when the rains were coming, when it would be hot, when it would be cold, animal migration, sailing in the Mediterranean, things like that. people very quickly realized that they could tie these, what we would now call annual events, to the positions of the stars in the skies.
So, for example, the annual flooding of the Nile came with the morning rising of Sirius, or Hesiod says, don't sail when the Pleiades have set. So it's kind of how you can set markers in order to keep your community surviving.
And presumably, if we know something about these early calendars, they must have been recorded in some way. So what are the first written calendars? What do they look like?
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Chapter 2: What were prehistoric calendars like and why were they important?
Well, two words there that I would say don't quite fit with my thinking, scientific and rational. Basically, it was emotional. They wanted to get rid of the power of the Catholic Church, so they had to get rid of the old calendar so they could get rid of the saints' days.
So they said, let's return to a bucolic agricultural calendar and we'll call it, today is the day for growing grass or today is the day for picking grapes. Even though it looks numerically, because it is decimal-based, as if it's quote-unquote scientific, it's actually, like most calendars, deeply emotional and culturally based. And it didn't last?
No, because they were surrounded by countries who didn't keep that calendar, and it became really, really difficult when you're having any kind of international negotiations.
And if you have all of these historical calendars that reflect different values and different priorities, what should we conclude about the modern calendar? Does it tell us anything about what we value today or is it just a historical throwback?
Well, historical throwback again, I wouldn't say that. Our calendar is based on shared cultural, emotional, religious assumptions and inheritances. One could throw it out, have a decimal calendar or base all of our time on ticks of the cesium clock.
But the truth of the matter is, it works with the fact that we are on a rotating and revolving rock that happens to go around the sun, that happens to have a moon that goes around us. And our calendar is best able to accommodate the reality of where we live on Earth.
Our listeners have said that it is slightly silly, or at least arbitrary, to quote a temperature record based on the fact that this is the hottest day that we've ever had in the UK in the month of May. Do you have sympathy with that complaint?
I wouldn't call it silly. I think the problem is when one thinks of any of the ways we divide and mark time as having an ultimate reality. It doesn't. It's not a question of precision equaling truth. It's a question of how we manage to approximate a seasonal, a yearly, a monthly cycle. And the best way is our quote-unquote silly calendar.
So there we go. Yes, the month of May is arbitrary and our very, very hot June likewise, but then so are all calendars, it seems. Our thanks to Kristen Lippincott, former director of the Royal Observatory at Greenwich and author of The Story of Time. If you've seen a number you think we should take a look at, email us at moreorless at bbc.co.uk. Until next time, goodbye.
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