An Evolving Universe
On the Curvature of Space (1922)
The true scale of the cosmos is enough to beggar even the greatest mind.
Take a second and consider from your own experiences the vastness of the Earth—its numerous continents, oceans, and nation-states. Over a million Earths can fit into the sun alone and that is to say nothing of the gaping expanse of the solar system out to the Oort Cloud. There are approximately 100 billion stars in the Milky Way, a moderately sized galaxy; there are as many as 2 trillion galaxies in the observable universe.
The immensity of the cosmos is only understood when one fails to understand it. Nonetheless, it is possible to mathematically describe the evolution of the universe as a whole. In 1922 Russian physicist, Alexander Friedmann, published a pioneering paper titled On the Curvature of Space which laid the foundation for modern cosmology.
At a time when the prevailing cosmological models envisioned a static universe, Friedmann introduced an alternative picture: a dynamic spacetime, the fate of which is determined by its matter and energy content.
Competing Cosmological Models
Friedmann's work emerged against the backdrop of Albert Einstein’s and Willem de Sitter’s provisional models of the universe. Both scientists had applied general relativity to cosmology, but with a few conceptual differences. Einstein’s approach proposed a cylindrical geometry where the size of the universe remained constant over time. This required the addition of a cosmological constant, Λ, to counteract gravitational collapse.