Stories from the Cosmos: Georges Lemaître, the Priest Who Blew Up the Universe

There are discoveries that, although they radically transformed our view of the cosmos, reached the world with the secrecy of ideas ahead of their time. And there are people who, despite being responsible for these silent revolutions, remained above the noise, faithful to a calling deeper than fame.

Georges Lemaître is one such figure. A Catholic priest, physicist, and brilliant mathematician, he imagined, long before the Big Bang was even mentioned, a universe emerging from an initial point of infinite density , which he poetically called the "primitive atom."

The year was 1927, and many physicists, including the famed Albert Einstein , who had published his theory of general relativity just over a decade earlier, still clung to the idea of ​​a motionless universe, as if stillness were a natural condition of the cosmos. But Lemaître, with his trademark mathematical acumen, solved Einstein's equations without the cosmological constant that the German physicist had introduced to enforce the stability of the universe . The result was unexpected and suggested a dynamic, expanding universe.

Lemaître published his results in a Belgian journal of modest circulation and his article went unnoticed by almost everyone, although in its pages was already found what would later be known as Hubble's law .

Two years later, in 1929, the American astronomer Edwin Hubble presented observations that empirically demonstrated this same expansion. But Hubble didn't use the equations of relativity or propose a cosmological model; he simply observed and measured that distant galaxies exhibit a redshift in their light spectra—that is, their light is stretched toward longer wavelengths. Furthermore, he found that the farther away a galaxy is, the faster it is moving away from us.

The true synthesis, however, had already been made by Lemaître, who was the first to unite theory and observation, showing that the expansion of the universe was a natural consequence of general relativity and that the data confirmed it .

Einstein, upon learning of Lemaître's results, reacted with skepticism. "Your calculations are correct, but your physics is abominable," he told the young priest. But time, like the universe, would spread the recognition. Years later, Einstein himself would admit his error in trying to fix a universe that refused to stay still, and would recognize Lemaître as a pioneer.

But the story didn't stop there. In 1931, Lemaître proposed that all matter in the known universe had, in the distant past, been concentrated in a single point of unimaginable density and temperature . An initial state that gave rise to space, time, and everything else in existence. He called this idea the "primitive atom," not with dogmatic intent, but as a scientific metaphor.

In the years that followed, Lemaître continued to develop his ideas while working as a professor, mathematician, and active member of the Pontifical Academy of Sciences, with a humility as expansive as his theories.

When the term 'Big Bang' first came into use, it was often used by its detractors, especially astrophysicist Fred Hoyle , a proponent of the steady-state model. Yet, observations continued to point in Lemaître's direction. Until, in 1965, the accidental detection of cosmic background radiation dealt the final blow to alternative models. It was an echo of the birth of the universe that Lemaître had imagined decades earlier.

For a long time, Lemaître's name was relegated to footnotes. It wasn't until 2018 that the International Astronomical Union finally decided to rename Hubble's law as the Hubble-Lemaître law. Justice had been done to the man who saw the origin of the universe before anyone else.

Astronomical Observatory of the National University