"A cosmic mystery of immense proportions, once seemingly on the verge of solution, has deepened and left astronomers and astrophysicists more baffled than ever. The crux ... is that the vast majority of the mass of the universe seems to be missing." -William J. Broad Despite the wondrous, luminous sights of the night sky, we've learned that normal matter -- protons, neutrons, electrons and the like -- make up only 4% of the total energy in the Universe.