Astronomers are engaged in a lively debate over plans to rename one of the laws of physics.

It emerged overnight at the 30th Meeting of the International Astronomical Union (IAU), in Vienna, where members of the general assembly considered a resolution on amending the name of the Hubble Law to the Hubble-Lemaître Law.

The resolution aims to credit the work of the Belgian astronomer Georges Lemaître and his contribution—along with the American astronomer Edwin Hubble—to our understanding of the expansion of the universe.

While most (but not all) members at the meeting were in favor of the resolution, a decision allowed all members of the International Astronomical Union a chance to vote. Subsequently, voting was downgraded to a straw vote and the resolution will formally be voted on by an electronic vote at a later date.

Well that's a pretty clear majority in favour of renaming the Hubble Law as the Hubble-Lemaître Law. But the vote is not yet binding - online voting will occur in Sept & Oct #IAU2018 — Keith Smith (@DrKeithSmith) August 30, 2018

Giving all members a say via electronic voting was introduced following criticism of the IAU’s 2006 general assembly when a resolution to define a planet—that saw Pluto relegated to a dwarf-planet—was approved.

But changing the name of the Hubble Law raises the questions of who should be honored in the naming of the laws of physics, and whether the IAU should be involved in any decision.

An expanding universe

The expansion of the universe was one of the most mind-blowing discoveries of the 20th century.

Expansion here means that the distance between galaxies in general increases with time, and it increases uniformly. It does not matter where you are and in which direction you look at, you still see a universe that is expanding.

When you really try to imagine all of this, you may end up with a headspin or even worse. The rate at which the universe is currently expanding is described by the Hubble Law, named after Edwin Hubble, whose 1929 article reported that astronomical data signify the expansion of the universe.

But Hubble was not the first. In 1927, Georges Lemaître had already published an article on the expansion of the universe. His article was written in French and published in a Belgian journal.

Lemaître presented a theoretical foundation for the expansion of the universe and used the astronomical data (the very same data that Hubble used in his 1929 article) to infer the rate at which the universe is expanding.

In 1928, the American mathematician and physicist Howard Robertson also published an article in Philosophical Magazine and Journal of Science, where he derived the formula for the expansion of the universe and inferred the rate of expansion from the same data that were used by Lemaître (a year before) and Hubble (a year after).

Robertson did not know about Lemaître’s work. Given the limited popularity of the Belgian journal in which Lemaître’s paper appeared and the French language used, it is argued his remarkable discovery went largely unnoticed at the time by the astronomical community.

But the findings published by Hubble in 1929 were most likely influenced by Lemaître. In July 1928, Lemaître and Hubble met at the 3rd meeting of the International Astronomical Union, in Leiden. During the meeting they discussed the astronomical evidence suggesting the expansion of the universe.