The more you understand about technology, the cooler it gets. I think most of our readers know that you can put a LOT of pictures, music, and email on a computer, but humor me while I explain how amazingly cool that feat is.
All of that data is stored on a hard disk. Inside that hard disk are a few, well... disks (as in flat, round plates) called platters. They're stacked vertically, and spin very quickly. Similar to a record player, data is stored in rings (records use spirals), and a head reads data from the platter, moving toward the center of the platter and back out again depending on where the data is (just like you can move a record player head to skip to different parts of a record). So there is a platter, always spinning, and a head moving in and out to read data as it passes underneath.
The interesting part about this all this is the scale! I first learned this in a class a few years ago, but saw it again today in Tom's Hardware:
"The dimensions of the head are impressive. With a width of less than a hundred nanometers and a thickness of about ten, it flies above the platter at a speed of up to 15,000 RPM, at a height that’s the equivalent of 40 atoms. If you start multiplying these infinitesimally small numbers, you begin to get an idea of their significance.
Consider this little comparison: if the read/write head were a Boeing 747, and the hard-disk platter were the surface of the Earth:
* The head would fly at Mach 800
* At less than one centimeter from the ground
* And count every blade of grass
* Making fewer than 10 unrecoverable counting errors in an area equivalent to all of Ireland."
You can look at scale another way: a nanometer is one-billionth of a meter. According to this link a germ is about 1000 nanometers large. That hard drive head is a tenth the width of a germ. Next time you feel like your computer is taking too long to do something, think of a Boeing 747 flying at 800 times the speed of sound counting blades of grass!