You may or may not be aware that in your own accent [HD: bog standard educated/metropolitan RBP] you have 2 LsClose enough for jazz, as my old Musical Director used to say ...
<potential_rant get-out="life's too short">...What she meant (and probably knows) was in your own accent you have dozens if not hundreds of Ls, which can be divided into two broad types. I mentioned this in the Introduction to When Vowels Get Together: Book 2 - Sonorants (now available in a work-in-progress form at all good Kindle libraries) in a note about allophones:
(in a way that I thought didn't give jazz the respect it deserves – how DARED he? – though in his defence I imagine in some circles it's a strong collocation [that's ESOL teacher-ese for "well-known phrase or saying"] in which case he was guilty of a careless use of words, rather than actual intellectual vandalism)
If the idea of allophones is new to you, consider the words leek and keel. In the first, the [l] sound is formed towards the front of the mouth (the so-called "clear l") and the [k] is formed at the back of the soft palate. In the second, the [k] sound is formed nearer the front of the mouth (the closure is between the body of the tongue and the hard palate), and the [l] is formed at the back (the so-called "dark l"). In both cases the distinct [l]s and [k]s are allophones of the /l/ and /k/ phonemes. (The sounds represented by the /i:/ phoneme differ too [because of the distinct positions of the tongue at the onset of the vowel] but the difference is much more difficult to hear).
If you've downloaded a copy, there's a mistake in this note; I got "hard" and "soft" mixed up. I'll upload a fixed copy later today.
To be clear, all the [l]s in keel, carl, coal, cool, kale, kill, call, curl, col, cull,.. [etc: the whole range of possible phonetic contexts] are different, though broadly similar: the so-called dark l. Similarly, all the [l]s in leek, lark, look, Luke, like, lake, lick, lack, lurk, lock, luck, leck...[etc: the whole range of possible phonetic contexts] are slightly different, though broadly similar: the so-called clear l – a name that has mnemonic value, as the l in it is clear.
But, returning to that Curious Case... As often, given the format (13-odd minutes of popular science) it wasn't entirely satisfying. If I had been the original asker of the question Why do people speak in different accents? I'd have felt short-changed (although I wouldn't have asked it in the first place, as I already know that it couldn't possibly be answered in this format).
It's an interesting question, and one that's impossible to answer in any non-circular way: People speak their mother tongue because it's the tongue spoken by their mothers (and their family and peers, colleagues et al)., and accents differ between mothers because they learnt from their mothers,,,: it's turtles all the way down, as many thinkers before Terry Pratchett said.
A feature of the Curious Cases... format is the signoff, with one of the presenters asking "Can we say Case Solved?" and the other answering "Y-e-s but..." Although there's an infinite supply of buts, I'm constantly entertained by the questions.
Update:2018.12.01.16:15 – Added PS
Towards the end of the programme, Adam Rutherford mentions the effect of "fortnight" on an American audience – which reminds me of a fortnight-related tidbit from my time at DEC (in the days when it was still OK to call it DEC, rather than the polysyllabic monstrosity wished on us by HR).
In the HELP text for VMS (the operating system that drove VAX computers) a counter was specified in micro-fortnights, as
60 (secs) x 60 (mins) x 24 (hrs) x 14 (days)This is a rough approximation to a million – OK, just over 1.2 million, but it was an engineering firm at the time.
For all I know, this may still be lurking in the code for OpenVMS; I doubt it though, as network management changed radically in the early 1990s (in ways discussed elsewhere [in my other blog]).
Update: 2018.12.02.12:05 – Added PPS
On further reflection, I've realized that the approximation was a bit closer than that 1.2+ million. As the writer was a software engineer, his "million" was 10242: about 1.05. So a fortnight is not that much more than a mega-second.