| Concept | Grade | Comments |
|---|
| The universe evolved from a hotter, denser state | A– | Compelling evidence drawn from many corners of astronomy and physics |
| The universe expands as the general theory of relativity predicts | | Passes the tests so far, but few of the tests have been tight |
| Dark matter made of exotic particles dominates galaxies | B+ | Many lines of indirect evidence, but the particles have yet to be found and alternative theories have yet to be ruled out |
| Most of the mass of the universe is smoothly distributed; It acts like Einstein’s cosmological constant, causing the expansion to accelerate | B– | Encouraging fit from recent measurements, but more must be done to improve the evidence and resolve the theoretical conundrums |
| The universe grew out of inflation | Inc | Elegant, but lacks direct evidence and requires huge extrapolation of the laws of physics |