The Disk Keeps Spinning

I don't know if Macs do this, but every Windows user must be familiar with those mysterious moments when the hard disk just keeps spinning, spinning, spinning. You're just typing something routine, trying to click on a web link, or perhaps not even touching the computer at all -- just reading what's on the screen at the time -- and there goes that hard disk, spinning, spinning, and more spinning. If you succeed in clicking on a link or typing a few characters, the machine reacts with agonizing slowness, as though it's fitting in your requests in those few spare moments it has in between its own, far more important business. You want to press a big red button that would tell your computer, "stop whatever you're doing and pay attention to ME!" Eventually, some minutes later, the hard disk stops spinning and the computer gets back to normal, as though it remembers that it's supposed to at least pretend that you're boss. Needless to say, that's what I'm going through right now.

What are our computers doing during these mysterious spinning moments? Is it a computer's form of exercise? Are they carrying out secret instructions from some distant user? Or do they have their own agendas -- some grand, unknown computation that they are calculating, all in league together perhaps, linked up over the Internet, which will reach its fruition at some moment known only to them?

You might think that if you aren't even touching the computer, and if you haven't even asked it to do anything, it would sit at the ready, awaiting your next instruction. But you'd be wrong.