The word "chiaroscurro" means light and dark in italian. it was a technique frequently used in the 16th century in religious images to create a strong contrast. why do you think contemporary artists don't seem to use this technique as frequently?

You do not see contemporary artist using chiaroscuro as much anymore, because it was used at a time when there were only candles and firelight for nighttime illumination. many of the paintings that used chiaroscuro did so to depict people who were around candlelight. this to illuminate their forms and create a dramatic effect. because we have modern electricity and light, the technique isn't seen as frequently in present day art.

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Generally spontaneous human combustion is something that still bewilders some, human combustion happens very rarely and doesn't affect the surrounding areas, so unless you want to set your self on fire, human combustion will remain spontaneous and very rare.