Idea for extended version of "Sun Jar" Answered
After seeing the recent Sun Jar I'ble, I had an idea (not even concrete enought to be a Completable) for an interestingly extended version. There now exist LEDs for infrared, visible red, green, and blue, and near UV.
It should be possible, with a mix of small low-voltage constant-current power supplies and pulse modulators, to construct a multiple-LED light source which roughly models what we perceive as the solar "spectrum." I don't mean formally reproducing the raw wavelength distribution, but rather the combination of intensities we see (or measure with a thermometer) in a prism- or grating-spread spectral display.
Coupling such a circuit to a solar cell would allow you to build a "Sun Jar" which "collects sunlight" during the day and "releases sunlight" at night. As I said, just an idea...