I wish people would stop posting about that thing. It doesn't even provide enough light to read a book by. If i only ever take microscopical sips from a sealed bottle of water it will also last for years.

Point taken :P What light it does provide is still impressive that it has done it for a hundred years.

Any bulb will do that if you run it on 1/4 of its rated voltage and never turn it off. It will be about as bright as the "Centennial" bulb.

Any bulb?

I'm biased. I like that they run a webcam: http://www.centennialbulb.org/cam.htm

Where'd you get the 1/4 voltage figure and how does that relate to its longevity?

http://en.wikipedia.org/wiki/Incandescent_light_bulb , under the Light Output and Lifetime subhead.

Lifetime is approximately proportional to the 16th power of the voltage, according to that article. 1/4 was a randomly made up figure (and probably wouldn't even result in a visible glow with many bulbs) but if you could see the light from such a bulb, it would presumably last up to 4 billion times longer than normal. By the same token a 5% reduction in voltage will double the life of the bulb.

So it wouldn't be hard at all to find a voltage somewhere in between that will allow an ordinary incandescent bulb to emit visible, maybe even useful levels of illumination, while lasting 100 years or more.

As others have mentioned, the Centennial bulb doesn't exactly emit useful levels of light. If I'm doing the math right, if you took a 100W/120V incandescent bulb rated for 1000 hours and scaled down the voltage by the 16h root of 876, or 80 volts, its life expectancy would reach 100 years. The bulb would use about half the power be about 1/4 as bright as normal. Its color temperature would obviously be pretty awful, but the Centennial bulb doesn't excel in that department either.

Not quite any bulb. Tungsten filaments evaporate over time, carbon filaments don't. But carbon filaments are much more fragile if subjected to thermal cycling or vibration.

I once owned a Remington electric razor that just died for no reason one day. I decided to take it apart and see if there was anything obviously wrong with it. There was - the electrical contact with the motor was made by a piece of graphite, and it had worn down to nothing. At that moment I decided to switch to another brand on the hope that it did not practice planned obsolescence, and I've been happy ever since.

You've just discovered that Electric motors use brushes on their commutators? Welcome to the 20th century.

Brushes are intended to be replaced, and many manufacturers supply spare brushes in the original packaging.

In the 21st century however the traditional brushes have been replaced by electronic switching.

see https://en.wikipedia.org/wiki/Brushless_DC_electric_motor

I wouldn't consider the practice of using graphite brushes in DC motors as planned obsolescence. It's more like best tool for the job, with a limited lifetime by its very nature.