Black and white photograph of Georges Lemaitre

Belgian priest and astronomer Georges Lemaître published a paper on the expansion of the Universe in 1927. Credit: Emilio Segre Visual Archives/AIP/SPL

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 the 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 before 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 seems to be the first time an organization has voted to alter the name of a 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 general secretary 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.

More to come

Still, the move could prompt further attempts to right the historical record by renaming scientific laws, says Stephen Stigler, a statistician and historian at the University of Chicago in Illinois. Stigler’s own ‘law of eponymy’ — conceived in 1980 — states that no discovery is named after its original discoverer. (Fittingly, and deliberately, the work behind Stigler’s law is better attributed to sociologist of science Robert Merton, rather than to Stigler himself.)

The names of scientific laws usually emerge from a community over time. Less-formal attempts to retrospectively give scientists credit have been attempted, says Stigler. For example, after the Higgs particle — named after physicist Peter Higgs — was discovered in 2012, some called for a name change to acknowledge the handful of other theorists who also predicted its existence.

Stigler questions whether it is the IAU’s role to change names in this way. “If this were my field, I’d be objecting to the imposition of an organization, however noble and useful they may be, into what should be a question of more general agreement within the profession,” he says.

Stigler also suspects that, despite the formal vote, the change will have difficulty sticking. “I have a huge drawer full of examples of Stigler’s law, and I don’t expect that to change.”

Universally acknowledged?

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 showing that galaxies seem to be moving away from Earth. Writing in a little-known journal called Annales de la Société Scientifique de Bruxelles, he showed that galaxies’ velocities seemed to be proportional to their distance — a relationship that became known as the Hubble 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 might 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.

Ideology and language

Disputes over names are often ideological, says Helge Kragh, a historian of science at the University of Copenhagen. Countries often differ in how they refer to scientific laws to give credit to their own nationals, he says. For example, Boyle’s law, which links a gas’s pressure and volume, is often known in France as Mariotte’s law, after the seventeenth-century physicist Edme Mariotte, who discovered it independently of the Anglo-Irish Robert Boyle.

Historians have known about Lemaître’s role in the Hubble law for decades, but the name change was driven by Benvenuti, who pitched the idea with supporting evidence to the IAU’s executive committee. He says that he wanted to honour Lemaître’s intellectual integrity, which made the Belgian value the progress of science more than his own visibility. Benvenuti also says that he admires Lemaître’s work to dispel the “pseudo-conflict between science and faith”, although he notes that this was not a factor in suggesting the change.

The resolution has courted some controversy. Kragh says that the IAU seems to conflate the Hubble law — which describes the apparent receding of galaxies — and its later use as an expression of cosmic expansion. Kragh also questions the accuracy of the documents given to members ahead of the vote. He challenges, for instance, the assertion that Hubble and Lemaître met in 1928 at an IAU assembly in Leiden in the Netherlands and exchanged views — something that Benvenuti and the IAU stand by.

The latest vote is not the union’s most famous decision. In 2006, its ballot on the definition of a planet controversially relegated Pluto to a dwarf planet.

The IAU has no plans for any further name-change campaigns, says Benvenuti, but if someone were to submit a resolution with sufficient supporting evidence, it would be considered.

Some possible misnomers in science include Halley’s comet, which astronomers had observed for more than a millennium before Edmond Halley calculated its orbit, and Fourier transforms, a mathematical technique used by French scholar Pierre-Simon Laplace before fellow French mathematician Joseph Fourier published on the topic.

Kragh also doubts whether scientists will heed the latest change. “As Fred Hoyle said, words are like harpoons. Once they go in, they are very hard to pull out,” he says.