Dark and Darker

Neither Newton nor Einstein - thought he was describing anything other than ordinary matter, the kind you can see, touch, feel, and taste. Yet for nearly three-quarters of a century astrophysicists have been waiting for someone to explain why 85 percent of all the gravity in the universe originates in a substance that no one has ever seen, touched, felt, or tasted. There's no guarantee that it even is a substance: maybe "excess" gravity emanates from something other than matter. In any event, the experts are clueless - and no closer to an answer today than they were in the 1930s. That's when the colorfully contentious Swiss-American astrophysicist Fritz Zwicky discovered the first sign that there is far more gravity in the cosmos than the stars, galaxies, and other visible objects could ever account for. Where was the "missing mass"?