Binary Chop

I love books and have a house full of them, so many that I’ve never read any of them more than once, there are just so many I haven’t had time to read yet. However, there are a few that get used more than once – my reference books.

We once almost spent an absolute fortune on a copy of Encyclopaedia Britannica but as we’d only just bought a house we couldn’t afford it. In the end we bought a ten volume encyclopaedia from a second hand bookshop.

A large proportion of an encyclopaedia is out of date the moment you buy it but this one was already many years out of date when we bought it. But how out of date?

It doesn’t contain a publication date. I’ve looked at the start of the first volume and the back of the last volume, but it doesn’t seem to say anything other than who edited it, who published it and who printed it.

I stuck a Post-it note in the front when I bought it in 1992 so I know it’s older than that, it’s clearly not from the previous century so I have a starting window of 1900-1992.

As a child did you ever play that game where one person picks a number between 1 and 100 and the other person tries to guess it with the only clues being higher or lower? If you’ve ever studied computer algorithms or thought a little about the game you will know there is a trick to guessing with a guaranteed maximum number of attempts – it’s called a Binary Chop.

Your first guess should be the middle number 1946 in my case. If the value is higher then you pick the middle number from what is left 1969. If you follow this process you will get to the answer in no more than log₂ n attempts. In our case 6.5 (or 7) attempts (between 2⁶ = 64 and 2⁷ = 128).

So what happened in 1946 that I can look for? WWII comes to mind and as the end papers of the encyclopaedia say Second Great War Edition I sort of know already that it will be in there. So my next guess needs to be the late 60’s.

Having read Stephen King’s book 11.22.63 I know that JFK was assassinated in 1963 but that’s a bit early. What about the moon landings? I know they were in my lifetime so that must be the late 60’s.

No mention of them so next guess is 1957. I’m struggling to think of anything now and need the help of an online encyclopaedia. Churchill resigned from office in 1955. No mention of that either.

George Orwell died in 1950 but he’s still alive and writing critical essays in my encyclopaedia.

Gandhi died in 1948, but that’s not mentioned, it does say that he moved to Bengal in Pakistan in August 1947.

As we know it would take time to prepare the encyclopaedia for publication we know it must have been a little while after August 1947 but not too long after January 1948 otherwise they surely would have included Gandhi’s death on 30^th January.

So I’m going to say it was published early in 1948.