Every now and then, you'll come across something that causes a sea-change in the way we perceive the universe and its workings. Einstein proved that Newton didn't have it all covered. Darwin showed us there was no cosmic watchmaker. And Julie now tells us that hitherto indivisible physical concepts can actually be separated out.
See this piece of string?
What do you have if you cut it in half? Instead of one piece of string, you have two smaller pieces of string.
What don't you have if you cut it in half? You don't have two half pieces of string.
Odd, isn't it? If someone rips a piece of paper in half you have two pieces of paper, not halves. On the other hand, if that swine rips up a twenty-pound note in front of you, then there will be two halves of a note. And a mad scramble for a roll of sticky tape. It seems it's only when things become more specific and defined that you are allowed to half, quarter, fifth (etc) them.
The same principle applies to noises. If someone whistles, then it's a whistle, even if they are suddenly cut short. On the other hand, if you talk about it musically, then our friend with the pursed lips can be said to have tweeted a minim, crotchet, or whatever.
That said, some things are still indivisible. A hole is a hole is a hole. You can't prise apart a clap.* And a bell peal is a bell peal, regardless of length.
Until now. Fancy another Trivial Pursuit question? Of course you do.
Tell me; what's the weath... physics like on your planet?
*Death of Terry Pratchett's Discworld would beg to differ with this statement.