Lemaître was born in Charleroi in 1894. In 1911 he came to Leuven to study mining engineering. Three years later, when the Germans invaded Belgium, he enlisted in the army. He fought on the Yser Front, where he witnessed the first gas attack – in the 1920s he was decorated for his efforts.

The war must have given him food for thought, because after the armistice he took two important decisions: he started to prepare for the priesthood and he stopped studying engineering and started studying physics and mathematics. In 1920, he received his doctorate and was ordained a priest in 1923. During the next two years, he received research assignments at prestigious universities such as Cambridge in Great Britain and Harvard and MIT in the USA. He then returned to Leuven to teach physics.

EINSTEIN’S TRICK

Lemaître is particularly intrigued by Albert Einstein’s general theory of relativity. Published in 1915, it offers a revolutionary new explanation of gravity and the structure of the universe. The mathematics is very complex and not many people understand all the implications of the theory at that point. Lemaître, however, gets it: Einstein’s formulas, he says, indicate that we live in an expanding universe. He also immediately understands that this idea has a very important consequence.

If you play the film of the expanding universe backwards, the universe gets smaller and smaller, until it is all concentrated in one point. Lemaître calls this point the primeval atom. In 1927, he publishes an article in which he explains his reasoning, but hardly anyone reads it. Most of the scientists who do read it reject his idea. 

For centuries, the prevailing opinion has been that we live in a static universe – a universe that has always been like this and will always remain like this. Even Einstein is convinced of this. Like Lemaître, he recognises that his formulas make a static universe impossible, so he uses a mathematical trick: he adds a constant, a quantity that makes the whole thing static. He has no proof for this ‘cosmological constant’, it just fits his intuition – and that of most physicists of his time.

Lemaître failed to convince his fellow physicists. At a scientific meeting, he discusses it with Einstein, but the latter responds with irritation. “Your calculations are correct, but your physics is abominable,” he bites Lemaître. 

SPOT NAME

The big change came in 1929. In the American Mount Wilson Observatory, the astronomer Edwin Hubble has the most powerful telescope in the world at his disposal. With it he observed that the stars and the galaxies move away from us at great speed, in whichever direction you look. The further away they are from us, the greater the speed. Exactly what Lemaître had predicted in 1927. 

Lemaître’s article now gets the attention it deserves, and more and more colleagues change their minds. Including Einstein. Following a lecture by Lemaître in January 1933 he stands up and starts applauding – you could not get much more recognition as a physicist in those days. American journalists also record a statement from Einstein: “This is the most elegant and satisfactory explanation of creation I have ever heard.” He calls the cosmological constant “the greatest mistake of my life”, and he promptly deletes it from all his formulas. 

In the course of the 1930s and 1940s, Lemaître’s primeval atom began to find acceptance in scientific circles, although there were still opponents. One of them, the respected British physicist Fred Hoyle, mockingly called the theory the ‘big bang’ in 1949. The name stuck.

SEPARATE WORLDS

In 1951 Lemaître again enters into a discussion with a world authority. This time with his big boss, Pope Pius XII. During a speech, he claimed that the Big Bang theory is a confirmation of the creation story in the Bible. Lemaître was horrified: the Bible knows nothing of physics, and physics knows nothing of God, he argued. Religion and science must not be mixed. The message is received. The Vatican has not commented publicly on the matter since.

NEW LAWS

Contemporaries consistently describe Lemaître as a modest, gentle man. He never laid claim to the Big Bang theory, and when he died in 1966, his name was all but forgotten. Over the years, other scientists had taken the credit. Edwin Hubble, for example, was long regarded as the father of the Big Bang theory. The expansion of the universe as described by Lemaître was even named ‘Hubble’s law’. 

It was not until the end of the 20th century that scientists began to see again what a phenomenal contribution Lemaître had made to our knowledge of the cosmos. In 2018, almost 80% of the members of the International Astronomic Union voted to change the name ‘Hubble’s law’ to ‘Hubble-Lemaître law’.

FESTIVAL!

From 16 October 2021 to 30 January 2022, the festival ‘BANG! City festival of the Big Bang’ will take place in Leuven. It focuses on our fascination for the cosmos and its impact on science and culture. Central to the festival are three large exhibitions. 

Imagination of the Universe’ at M highlights the way the cosmos has been represented in art and thought, from classical antiquity to the 19th century. 

M will also open a solo exhibition with Richard Long, the British land-art artist who is inspired by nature, the cosmos and the universe.

During his many walks, he looks for natural elements such as earth, stones and wood, which he then rearranges

In the university library, you can see ‘Beyond the Big Bang’, an exhibition at the intersection of science and contemporary visual art. It tells the story of modern cosmology, taking Georges Lemaître’s pioneering scientific research as its starting point. 

BANG! City Festival of the Big Bang’ is an initiative of KU(N)ST Leuven, the collaboration between the City of Leuven and KU Leuven.