Word: einstein
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...decade later, though, Edwin Hubble discovered that the universe was expanding after all. Einstein immediately and with great relief discarded the cosmological constant, declaring it to be the biggest blunder of his life. (If he had stuck to his guns, he might have nabbed another Nobel...
Even so, the idea of a cosmological constant wasn't entirely dead. The equations of quantum physics independently suggested that the seemingly empty vacuum of space should be seething with a form of energy that would act just like Einstein's disowned antigravity. Problem was, this force would have been so powerful that it would have blown the universe apart before atoms could form, let alone galaxies--which it clearly did not. "The value particle physicists predict for the cosmological constant," admits Chicago's Turner, "is the most embarrassing number in physics...
Aside from that detail, the Einstein connection made the idea of dark energy, or antigravity, seem somewhat less nutty when Schmidt and Perlmutter weighed in. Of course, some astrophysicists had lingering doubts. Maybe the observers didn't really have the supernovas' brightness right; perhaps the light from faraway stellar explosions was dimmed by some sort of dust. The unique properties of a cosmological constant, moreover, would make the universe slow down early on, then accelerate. That's because dark energy grows as a function of space. There wasn't much space in the young, small universe, so back then...
Same goes for the universe, but with one more dimension. According to Einstein, the whole thing could be positively or negatively curved or flat (but don't try to imagine in what direction it might be curved; it's quite impossible to visualize). "What the new measurements tell us," says Turner, "is that the universe is in fact flat. Draw a triangle that reaches all the way across the cosmos, and the angles will always add up to 180[degrees...
According to Einstein, the universe's curvature is determined by the amount of matter and energy it contains. The universe we evidently live in could have been flattened purely by matter--but the new discoveries prove that ordinary matter and exotic particles add up to only about 35% of what you would need. Ergo, the extra curvature must come from some unseen energy--just about the amount, it turns out, suggested by the supernova observations. "I was highly dubious about dark energy based only on supernovas," says Princeton astrophysicist Edwin Turner (no relation to Michael, though the two often refer...