Why doesn't a lightbulb help a plant?

[TSN79]

I have a plant in my living room that doesn't get much light, and so it doesn't do very well. I've always been told that light from normal lightbulbs doesn't help because it's not "natural" light. But then I started thinking. The filament glows from the current and I'm just wondering what makes the emitted light not "natural"? It's just something that gets red hot from something and so emits light? Also - theoretically - if I could build a campfire in my room that would probably work since that would undoubtedly be natural light right? I mean, what is the sun if not just one huge campfire?

 

[chroot]

The sun is a blackbody (basic thermal radiator) with a temperature of about 5,700 Kelvin. This temperature causes it to emit the greatest energy in the green and yellow parts of the spectrum. A typical light bulb filament is much cooler than this, and produces most of its light in the red part of the spectrum.

A fire (campfire or candle flame) is also too cool to produce Sun-like light. The distinction between "natural" and "unnatural" light is immaterial -- light is light. There are many kinds of commercial lights on the market with spectra that are close to that of the Sun.

- Warren