My flatmate, Jordan, was just telling me how he replaced his headlight on his car today, went home, and then his mom noticed that the other light had burned out. There should be a way to tell how long your lights have left. not just in car head lights, but in household lights as well. He pointed out that it could have been dangerous if they both went out at the same time.

I am not sure of the physics of it though. lights can burn forever if they are never turned off, or so i hear. I think the longest lasting lightbulb is burning in some firehouse in the middle of the country, and has been for the past 100 years or so. but i digress. Since lights burn out from the degradation of the filament connection, you'd have to develop a tiny sensor to measure that connection's strength, and determine how much longer it had. If such a sensor could be developed, perhaps have the light flash 3 times every few hours to let the person know it's going out. or a dashboard light turns on in a car.