P!=NP is the biggest open question today, and not just because of the cliched joke that if P=NP, we'd solve the other 5 outstanding Clay Millenium Prize Problems. It's the biggest outstanding question because it has the chance to reveal very fundamental flaws in our entire scaffolding of theoretical understanding of our computational universe. Many different---and currently very plausible---advances to answering the P=NP question could very well be akin to the Michelson-Morley experiment, revealing gigantic flaws in our understanding of the computational universe, just as that experiment pretty much put the kibosh on luminiferous aether. Anyone who confidently asserts that P!=NP is dangerously close to Lord Kelvin's assertion in 1900 that "There is nothing new to be discovered in physics now. All that remains is more and more precise measurement."