The Tangled History of Big Bang Science

For a theory of the universe as successful as the Big Bang, it may come as a surprise to realize how many complications its promoters had to stumble through. Let’s begin with the unfortunate figure of Alexander Friedmann, the brilliant Russian mathematician and meteorologist who was the first to exploit something remarkable about Einstein’s “field equations,” the set of ten equations that reimagined gravity as an outcome of curved spacetime.

In 1917, Einstein, perhaps to not seem too out-there, argued that one could use the field equations to derive a model of the universe very much like the traditional Newtonian view—an eternally static, or “steady-state,” cosmos. The difference in Einstein’s model was that it was finite in size where Newton’s was infinite.

Universes like Friedmann’s could only be “curiosities,” Einstein said, never true descriptions of reality.

This was too conservative of Einstein, Friedmann thought. He instead viewed Einstein’s model as just one example of many, Friedmann derived three kinds of cosmological models that were much more dynamic than Einstein’s: One was a finite universe of positive curvature—like a sphere—that expanded from a singularity and then eventually stopped expanding and collapsed back to a point; the second: an open infinite universe of negative curvature, which could be pictured like a saddle of infinite size; and finally: a universe of zero curvature—a flat plane—that expanded at an ever slower and slower rate, coasting into infinity.