As a mathematician and lay pedant I get easily annoyed when people promulgate mistruths. But I try to distinguish between the trivial and the serious and then only get worked-up about the second category. This week though, I cracked under the pressure of something completely frivolous and end-up releasing my own Bad Maths meme onto the internet.
Last August, I noticed people commenting online that October 2010 would have five Fridays, Saturday and Sundays (which is true) and that this wouldn’t happen for another 823 years (which is not true). At the time I was curious about why this annoyed me as deeply as it did, but I was still quickly distracted by other things. Then, just a few days ago, I saw that people were tweeting exactly the same fact about July 2011 having five Fridays, Saturdays and Sunday and that this wouldn’t happen for another 823 years. Now I was seriously annoyed.
But I couldn’t work out why. Surely this was the very quintessential trivial mis-fact that gets spread on the internet but cannot possibly cause any harm. Yet I found it deeply troubling.
After much thought (and asking the hive-mind) I’ve decided that this incorrect meme presses the following of my buttons:
Easy to disprove, but few people did
I got annoyed that so few people bothered to check a fact before they passed it on. If people aren’t checking easily falsifiable facts about trivial matters, can we still hope that they’re checking complex, semi-ambiguous facts when it comes to matters of great importance, such as medical advice?
It takes near-zero thought to flip forward in a calendar and see that March 2013 also has five Fridays, Saturdays and Sunday. Even if you’re July-centric, you’ll find another one of those in 2016.
With slightly more thought, you’ll notice that all 31 day months must have five lots of some group of three days, starting with whatever day the 1st of the month is. As the days drift around the year, eventually they all get equal goes and so 1/7 of all 31 month days will start with a Friday. There are seven 31 days in the year. This will average our rather nicely to happening once a year, not every 823 years.
Actually, this is about as much thought as it needs to realise there are only 14 different possible calendars (seven starting days, leap year or not) and in fact 2011 will repeat itself exactly in 2022.
If you’re prone to over-thinking things through, you can calculate that the sequence of calendars completely repeats itself every 400 years, meaning you can’t have date/day/month special-combination-events more than 400 years apart.
Perpetuates the Maths is Hard and Impenetrable image
I dream of a world not where everyone is better at maths, but where people have the mathematical confidence to use what they already know. Fewer people would be ripped off my banks and insurance companies if they weren’t thrown off by number-chaff and actually checked what the deal was.
This 823-years meme had me suspecting that people saw a fact accompanied by a big number and instantly assumed that they couldn’t think it through for themselves.
It’s a hollow substitute for real mathematical amazement
Blindly accepting all convoluted and possibly-untrue maths facts is like never peeling that semi-transparent protector film off the front of your mobile phone. You’re settling for a blurry approximation of the real thing because of sheer laziness.
There are so many amazing things in maths it’s a shame people spend their curiosity on whatever pseudomaths comes their way.
A once-in-823-years event twice in two years
Is the meme spreading through an entirely untapped demographic who missed it in October 2010 or do people clear out their mental-cache that frequently? Either the internet really does have an endless supply of forwarding-heavy, fact-checking-light users or there are some serious medium-term memory concerns to be had.
Now I knew what was annoying me about the 823 thing; what was I going to do about it? I considered setting up some kind of automated twitter service that would search for tweets featuring “823 years” without also using the key words “false”, “not” or “do you know how to use a calendar” and drop them a little note. But this felt a bit spammy and I was talked out of it by a wise sage of the internet (aka Dave Gorman).
Then this morning I was sent a different calendar fact that also only happens every 823 years! Apparently if you add the age you turn in 2011 to the two-digit year of your birth, the total will be 111. This is indeed true, and I’ll leave it as a quick puzzle to generalise this to any year and spot the ages for which it will not work. Anyhow: I was amazed that the 823 year had attached itself again despite having nothing to do with the factoid. I asked the tweeter of this fact and he said that his Arabic Dad had sent it to him.
This has resulted in my “823 Years Conjecture”: Stating that something happens every 823 years will greatly increase its chances of becoming a meme. Actually, I’m keen to find the earliest citation possible of 823 years; please do let me know if you find one. Maybe there actually is something that occurs every 823 years.
So I decided that my best outlet for my frustration was not a righteous campaign of auto-correcting people, but rather to craft my own 823 meme. This is what I settled on, and release onto the internet:
“Add the digits of your age in 2011. Subtract from age and add digits of answer. eg 31-4=27,2+7=9 It’s always 9! Will work again in 823 years”
I was proud of this tweet because it is technically correct, including the 823 thing. It will indeed work in 823 years, in addition to working every year in between.
It also mentions a year (2011, but as someone rightfully pointed out: I should have used 2012) but is fairly obviously year-invariant. My hope was that this would encourage people to look closer at the maths behind the trick.
In addition, there certain exceptions on ages. If you’re 9 or younger, the answer is zero (technically the final result is always “0 mod 9”). For ages over 100 you require repeated addition of the digits to get to 9 (known as the “digit root” of the number). It’s easy to start unpicking this maths trick and investigate why it actually works.
The response was half what I’d anticipated and half unexpectedly insightful/educational.
It did indeed get forwarded around with a straight face by faithful twitter followers (god I love those guys) and thus landed under the noses of people who had no idea about me and my emotional, mathematical journey of 823 years. Some of these people forwarded it on (no surprise there) and many people spotted the vacuous reference to 823 years (still unsurprised). What caught me off-guard was the barrage of mathematical smack-downs from people who had done just enough research to locate me as the source of the tweet, but not enough to actually read my twitter-page.
And you know what? Us members of the fact-pack can be real dicks when we feel the need to correct people.
I’m used to all sorts of abuse on the internet; it’s part of the game. Some of it is the brownian-motion of anonymous personal abuse, other bits are mathematical quibbles of disproportionate detail. But these tweets were different. There was something cutting about corrections from people who knew they had a superior grasp of very easy concept.
I realised that Past Matt – who wanted to set up an automated twitter account to do just that – was looking like a real jerk right now.
I even knew that I was meta-correct, but it still felt bad to be corrected. I’d gone from not knowing why I was annoyed at something to not being sure why I felt bad when people were correcting it. This brings me to my (recently devised) Inconsequential Mistake Paradox: As the triviality of a mistake online increases, so does both the want of other people to correct it as well as the insensitivity of doing so.
It seems the solution to depress my buttons is not to try and wipe incorrect memes off the face of the internet (with the damp cloth of insensitivity) but rather to flood the internet with valid, accessible nuggets of mathematical amazement. Netizens clearly have an appetite for this sort of stuff; if anything it’s our fault they have to sate themselves with pseudomaths. If there was more playful maths around, maybe people who develop more mathematical confidence and start to question dubious claims of all levels of severity.
UPDATE: I use the word “factoid” incorrectly above. Please consider it to be “factlet” for all intents and purposes.
And thanks to everyone who sent me this xkcd comic: Duty Calls