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KU Leuven's Georges Lemaitre recognized in Hubble law name change

31 October 2018

Members of a major international organization of astronomers have voted to change the name of the Hubble law — which relates to the Universe’s expansion and underpins modern cosmology — to recognize a contribution made by Belgian priest and astronomer Georges Lemaître.


The International Astronomical Union (IAU) recommends that the law now be known as the Hubble–Lemaître law. In the 1920s, the Belgian described in French how the expansion of the Universe would cause galaxies to move away from Earth at speeds proportional to their distance. He did this two years earlier than US astronomer Edwin Hubble used his own data to establish the same relationship. Of the 4,060 astronomers who cast votes (out of around 11,072 eligible members) 78% were in favour of the change.

The move appears to be the first time a union has voted to try to alter the name of scientific law — although some scientists doubt whether the change will be noticed. The IAU has been the arbiter of planet and moon names since 1919 and oversees astronomers’ official catalogue of star names, but it has no formal mandate over the names of scientific laws.

Piero Benvenuti, a former IAU president who proposed the motion, says that the new terminology is a recommendation only. “If people will continue to use the Hubble law naming, nobody will object,” he says.


Historians have long studied who deserves credit for discovering the expansion of the Universe.

In 1927, when most believed that the Universe was static, Lemaître proposed that it was expanding, to account for observations that showed galaxies seem to be moving away from Earth. In a little-known journal called Annales de la Société Scientifique de Bruxelles, he showed that galaxies’ velocities appeared to be proportional to their distance — a relationship that became known as Hubble’s law. Using astronomical data collected by others, he also derived a rate of expansion, today known as the Hubble constant.

In 1929, Hubble described the same correlation using his own, improved experimental data and derived a more accurate constant, essentially confirming the law that eventually bore his name.

Lemaître’s contribution remained less well known, possibly in part because the 1931 English translation of his paper missed out the derivation of the constant. Some historians even suspected that Hubble or his supporters may have had a hand in selectively translating the work. But Hubble was cleared in 2011 after an investigation by astronomer Mario Livio, who found a copy of a 1931 letter by Lemaître in which he said that he had omitted the discussion about the constant from the translation because more reliable data had since been published.

Fans of the Belgian astronomer are happy with the decision. “Lemaître did not push much his results, so he should have deserved more fame than he had,” says Gabriele Gionti, an astronomer at the Vatican Observatory who voted for the resolution.


Georges Lemaître: Who was the Belgian priest who discovered the universe is expanding? And what's his connection with Leuven?

Georges Lemaître was an astronomer and professor of physics who is thought to be the first to have theorised that the universe is expanding.

His theory was observationally confirmed soon afterwards by Edwin Hubble in what is now known as Hubble’s Law. Lemaître is also credited with proposing what has now become known as the Big Bang theory – which says that the observable universe began with an explosion of a single particle.


A statue of Georges Lemaitre, revealed by the KU Leuven in 2017

The theory, which is now widely accepted, first appeared in 1931 in one of Lemaître’s academic papers and was a significant break from the orthodoxy of the time.

Born on 17 July 1894 in Belgium, he initially began studying civil engineering. His academic pursuits were however put on hold while he served in the Belgian army for the duration of the First World War. After the war, he studied physics and mathematics and was also ordained as a priest.

In 1923 he became a graduate student at the University of Cambridge before going on to study at Harvard and Massachusetts Institute of Technology (MIT).

In 1925 he returned to Belgium, where he became a part-time lecturer at the Catholic University of Leuven. Two years later, he published his groundbreaking idea of an expanding universe. His initial idea was not related specifically to the Big Bang, but his later research focused on the concept of the universe starting from a single atom.

In 1933 at the California Institute of Technology, some of the greatest scientists of the time from around the world gathered to hear a series of lectures.

After Lemaître delivered his lecture and theory, Albert Einstein stood up and said: “This is the most beautiful and satisfactory explanation of creation to which I ever listened."


He was elected a member of the Royal Academy of Sciences and Arts of Belgium and the Pontifical Academy of Sciences.

In 1951, Pope Pius XII claimed that Lemaître's theory provided a scientific validation for Catholicism – a claim that Lemaître resented, as he stated his theory was neutral.

He died in 1966, shortly after he discovered the existence of cosmic microwave background radiation, which added weight to his theory on the birth of the universe.

Sources: The Independent, Nature

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