Leave your feedback Share Copy URL https://www.pbs.org/newshour/show/a-spark-of-inspiration Email Facebook Twitter LinkedIn Pinterest Tumblr Share on Facebook Share on Twitter Story Any parent can remember the moment when their child asks one of those seemingly simple, yet devilishly hard questions: “why is the sky blue?” “why are plants green?” and “where do babies come from?” One of the toughest in this category is “what is a flame?” Miles O’Brien report on Alan Alda’s Flame Challenge, which challenges scientists to answer that question: with 6,000 11-year-olds as judge.