In most calendar years, our little blue planet’s denizens get to look up into the night sky and see a beautiful full moon 12 times – that is, once a month.
However, the lunar month doesn’t quite match up to our rigid structure of calendar months. We humans like to define everything in a way that often suits us, but more often than not doesn’t suit others, or in this example doesn’t suit the universe.
In reality, rather than one nice neat and tidy full moon each calendar month, that pesky old moon plays by its own rules. By this I mean that there is in fact 29.530587981 days between full moons, and even this is an average. Now think about that for a second…
I assume you remember the months vs days rhyme they teach you as a kid:
30 Days hath September,
April, June and November.
All the rest have 31,
except for February all alone,
It has just 28 days a year,
But 29 on each leap-year.
If you do, then you’ll realize that way back in time, we decided it was too hard to remember the number 29.530587981, and instead built a wacky set of months with various days each, to make up a year (must have been a committee involved).
Then some bright spark wrote down the rhyme above so they could remember all the different months’ number of days.
Then we started teaching kids to remember the rhyme – believe me, I know. I’ve been trying to explain this to my 5 year old!
But try as we might, none of those months ever add up to 29.530587981.
So every month, those little extra bits mismatch with the lunar month, and this process occurs over and over again.
When all those little extra bits of time get added up, eventually something has to adjust, and you get a month with two full moons for the price of one!
And that second full moon is a Blue Moon.
July 2015 is one of those rare months. (Actually not that rare, they occur approximately every 2.7 years if you run the numbers). And tonight’s the night, so don’t forget to look up!
Just remember a couple of things while you do…
1) The moon is not actually blue, although it can appear that way sometimes
2) Given the speed of travel of the Earth, Moon and Sun, a full moon is actually an instantaneous event, and doesn’t last all night (blink and you’ll miss it!)
3) All those rules we construct to make sense of something – to define it – actually more often than not make it more complicated.
Then, after a nice relaxing weekend, when you come back to the office on Monday to review HR or OH&S Policy, or Performance Reviews, or Staffing Strategies, Org Charts and so on – try and remember point 3 from when you were staring up at the moon.
ALEX KELLY – 31st July 2015