Shtrange

Over a period of several centuries (roughly 1350 to 1700) in England, the English language went through what linguists call "The Great Vowel Shift."  That's basically where our long vowels came from -- A changed from ah to ay, I changed from ee to eye, etc.  Nobody knows what caused it, but these things happen.  Languages are fluid.

I think that American English is in the midst of another change.  Over the last 40 years or so, I have noticed changes in the pronunciation of the short vowel sounds for E and A, so that "better" sounds more like "butter," and "slap" sounds more like "slop." 

One consonant sound is changing too, but this one hasn't been around more than a few years.  People have started to change the S sound to SH at the beginning of words or syllables that start with STR, like "shtrong" or "inshtruct."

This is all very gradual, of course, and not all native English speakers have changed, yet.  I've done a little searching on the Internet to see what other people have to say about it, and I've found nothing about the vowels and only a few complaints about the SHTR thing, mostly from Michelle Obama's detractors.

Nobody has offered an explanation, but I think it's easy to see what's causing this.  Pay attention to what your lips and tongue do when you say "bet" and then "but."  Everything loosens right up, doesn't it?  Do the same thing with "hat" and "hot," and then with "sss" and "shhh."  It takes less energy and movement in each case.

Maybe several centuries from now this will be known as "The Great Lazy Mouth Shift."

Ekshtraordinary.