Hang on. Y'all pronounce these differently? I've lived in four U.S. regions and have a pretty generic middle-American accent and I'm having trouble even thinking what the distinction might be.
To me they sound pretty much same if you’re very consciously saying the words as units, in isolation, “trying to pronounce them”.
If I say them a little more casually, though, the sounds that come out of my mouth are a little bit closer to “haam” and “hmster” - the vowel sound definitely gets emphasized in the former case and clipped almost entirely in the latter case.
It’s really easy to trick yourself into thinking you’re saying a word “properly” unless you’re very very conscious of the sounds you’re producing. As a Canadian, I know this - the stereotype Americans have of the Canadian accent is exaggerated, and it’s much stronger in rural areas, to the extent that I didn’t really think I sounded any different to the Americans in TV or movies. But Americans could still pretty quickly tell I was Canadian when I moved down there. The word “about” is one of the canonical tells, and although I don’t say “aboot” or anything, I learned that I do really say it in an accented way. It wouldn’t be apparent if you just asked me to pronounce the word, but in a sentence my mouth would gloss over the vowels, saying something more like “abut”.
It could definitely be an accent or something that I just happen not to have heard much. It just surprised me that I couldn't think of what difference the author was thinking there might be.
How well do you hear the difference between the /p/ sounds in words like pill, pat, punk vs. spill, spat and spunk?
Now try standing in front of a mirror, and hold a Kleenex (tissue...) in front of your mouth while pronouncing those words. You'll probably see a tiny flutter when pronouncing 'spill', 'spy' etc., but a large movement when pronouncing 'pill', 'pie' etc. The tissue is showing a difference that your ears have a hard time with. Not because the difference is hard to hear--a Thai speaker would have no problem--but because the sounds are allophonic in English (but phonemic in Thai).
Even in dialects where it is not traditionally transcribed (such as American - partly because long vowels are most common in place of a disappearing /r/), usually there is in fact an audible difference when you aren't thinking about it. This is part of why computer speech always used to sound so terrible. The most blatant example is when comparing vowels before /t/ vs before /d/, which means that "matter" (short) and "madder" (long) are distinguishable even in accents where /t/ is pronounced like /d/ in this context.
Note that this is orthogonal to stress (since both syllables are stressed in this example), and also orthogonal to the badly-named "long vowel, short vowel" taught in school (which is actually for completely different vowel sounds and which omits several other vowel sounds).
If I speak these sentences out loud, the words sound exactly the same to me:
"That doesn't matter at all." "He was madder than hell."
Incidentally I'd say both A's here also sound just like my A's in ham and hamster! It's a very pinched sound, almost nasally. My choir director has had to train it out of us by exaggerating it and making it sound even more ridiculous because it has no place in singing.
But I'd still say it'd be interesting to record your voice and check the actual timings even if you can't consciously hear the length. Assuming you can actually practice running speech while thinking about it, of course.
Regardless, it's a red herring, because vowel length can also refer to "long" vs "short" vowels as in Bake vs. Back. Thats a different, and in my view more common, meaning of vowel length
As for 'hamster', no one (that I know of) pronounces the /m/ as a glottal stop, although people sometimes epenthesize a voiceless consonant [p] (by devoicing the end of the /m/). Where some English dialects get a glottal stop is for an intervocalic or word-final /t/ (in addition, of course, to the glottal stop in the middle of 'oh-oh' and 'uh-uh'). I've also heard American English speakers glottalize word-final /k/ and sometimes /t/, but a glottalized stop is not the same as a glottal stop.
This doesn't resonate with me - the `ma` in both those words are pronounced exactly the same and are of the same duration when speaking.
I checked a few youtube videos now before responding (some science video with 'matter' in the title and some video with 'madder' in the title) and there isn't a distinguishable difference.
Do you have a few links to videos that show a difference?
I think the vowel gets pretty cramped with similar short vowels (hem-ham-hum) so the tendency is to make it more different. It drifted away in general in American English, but the vowel in "air" stands in the way in non-rhotic accents, so the change is much more random and word specific.
Edit - ah I see reading the context now, it's not the pronunciation but the speed. Hamster has a very fast ham sound
Kind of gave it away there.