Newton's Universe: Infinite, Static & Eternal

Kepler's ellipses and Galileo's telescope, covered in Chapter 4, finished off the geocentric model — but the new Newtonian universe that replaced it came with its own quiet, largely unstated cosmological assumption, one that would create a real, unresolved puzzle lasting for well over a century.

An Implicit Assumption Newton Never Fully Defended

Newton's law of universal gravitation, published in the Principia (1687), described how any two masses attract one another — but it raised an immediate structural question its own author had to address directly: if gravity pulls all matter together, why doesn't the universe simply collapse into a single central mass? Newton's real, documented correspondence with the classicist and theologian Richard Bentley, beginning around 1692 in connection with Bentley's own Boyle Lectures (delivered 1692 and 1694), took up exactly this question. The widely-discussed resolution attributed to this correspondence is that an infinite universe, with matter spread out roughly evenly in every direction, would feel gravitational pull equally from all sides — with no single center for everything to collapse toward.

Whatever its precise textual origin, the resulting cosmological picture — infinite in extent, static (neither expanding nor contracting), and eternal (with no real beginning or end in time) — became the working, largely unquestioned backdrop for physics for well over two centuries.

Olbers' Paradox: A Genuine Puzzle Hiding in Plain Sight

An infinite, static universe uniformly filled with stars creates a real, testable prediction: look in any direction, and your line of sight should eventually end on the surface of some star, however distant. If that's true, the entire night sky should appear as bright as a stellar surface — not dark at all. This is Olbers' Paradox, and its real history stretches back further than its own namesake.

Real Attempts at Resolution

Real, serious attempts to resolve the paradox came well before modern cosmology existed. Johann Heinrich von Mädler published the first genuine scientific resolution in 1858, proposing that a universe of only finite age — rather than a truly infinite, eternal one — would leave light from the most distant stars simply not having had time yet to reach Earth. Lord Kelvin, in 1901, is credited with the first fully satisfactory mathematical treatment of that same finite-age solution.

Looking Ahead

Chapter 6 covers Einstein's own real cosmological constant — a mathematical device added specifically to force his equations to describe a static universe, matching the Newtonian assumption this chapter has just traced — and his own later, real regret at having introduced it.

Reflect