The 4% Universe: Dark Matter, Dark Energy, and the Race to Discover the Rest of Reality

by Richard Panek

Guth realized that the infant universe could have gone through a process that physicists call a “phase transition” and everybody else calls “the thing that happens when water turns into ice or vice versa.” When the temperature of water changes, the transformation doesn’t happen all at once. It’s not as if the word goes out and suddenly every molecule of H2O in the lake has melted into liquid or hardened into ice. Instead, the transformation happens piecemeal. Even within small sections of the pond the ice isn’t freezing or melting uniformly. Cracks and fissures appear faintly, then harden, leaving a veined appearance. Guth found that if you apply that transformation mathematically to the conditions of the early universe, the phase transition would have produced a temporary vacuum. That vacuum, in turn, would have produced a negative pressure—a strong gravitational repulsion—that would have expanded space exponentially. The universe would have doubled in size, then doubled in size again, then doubled in size yet again. It would have done this at least a hundred times, and it would have done so over the course of 10−35 seconds (or 1/1035).