The Standard Mouse
More mouse balls than...
Well, the first thing most people would ask is "what's wrong with my mouse? It works fine." Before we answer that, let's just take a quick look at how a regular mouse works. Labeled an "optical-mechanical" or "opto-mechanical"….well, mechanism, a mouse makes use of a ball, which rolls along the underside of the device against a mouse pad or table. Stop me if you already know this part.
Now, here's the interesting part. The ball is situated along a couple of dollies (the cylindrical kind, not the dress-wearing kind), oriented against the X/Y plane. The dollies end on notched flywheels. On the other side of the flywheel sits a light emitting diode and a photoreceptor. When you move the mouse, the ball rolls along the surface and turns the dollies. This turns the flywheel, and the notches block out the light from the diode as they turn. This tells the receptor which direction the mouse is moving and how fast it's going, and the software translates the signal into onscreen cursor movement.
Notice the flywheel and sensor
So what's wrong with that?
Technically, the system works. In fact, it works great. As long as you have a level, uniform surface, you shouldn't experience any skips or loss of tracking. So why bother changing what isn't broken? For one, the mouse design is very retro - it's an old design with a lot of analog aspects in a wholly digital realm. It's also chock full of mechanical engineering - lots and lots of moving parts. This decreases the life of the device, and the open nature of the moving parts makes dust and grime collection a given.
If you've never cleaned out the guts of your mouse before, just take a second to look at the insides. Remove the ball and examine the rollers. $50 says they've collected a thick deposit of black gunk, which is an accumulation of dust, mouse pad, and dead skin and sweat from anyone who's used the device. Pretty damned gross, right?
Besides the questionable sanitary aspect, we're also dealing with another big problem here - precision. As dirt and grime collects over the rollers (and in some cases, the ball), the smoothness and consistency of the mechanism is compromised. How? Well, if you've ever used a public computer (and you KNOW those systems haven't had a good cleaning in as long as they've existed), you've probably noticed the mouse is less responsive, and in some cases has developed a chunkiness to its rolling. The dirty rollers create an inconsistent surface for the ball to roll against, and can more easily cause slips and missed movements.