The Big Bang theory is believed to be one of the most popular scientific theories today. According to this theory, the universe began as an extremely hot and dense substance which expanded and cooled down with time until, 14 billion years later, it acquired the form that we can observe today whenever we look towards the sky on a clear night. The theory is well supported by experiments and represents a good example of the almost incredible capacity of modern science for taking a small number of data gathered on our small planet and reconstructing the history of the entire universe from the first moments on.
Despite the popularity of the Big Bang theory only a few people today are aware that the first to describe it was a Belgian priest called Georges Lemaître who, in addition to preaching, dedicated his time to science and was among other things a friend of Albert Einstein himself. Einstein accepted the primeval atom theory, as Lemaître called his idea about the development of the universe which was later given its much more resounding name, the Big Bang, with great interest which was not followed by the larger scientific community until the 1960s. That was when two American scientists accidentally discovered that microwave radiation, which can only be explained by the notion that the universe was once much hotter than today, was reaching us from all the directions of the universe.
The universe as a radioactive atom
Of course, Georges Lemaître was not merely an amateur scientist. Even though he was ordained a Catholic priest in the fall of 1923, he always remained true to science. After earning his doctoral thesis in mathematics the same year he was ordained, he started his postdoctoral studies at Cambridge where he furthered his knowledge under the tutelage of Arthur Eddington who was believed to be one of the most eminent astronomers of the time. It was with him that Lemaître became acquainted with the latest discoveries and the newest research methods in astronomy as well as cosmology which was already gradually becoming a branch of science within which experimentally verifiable theories could be formed.
After a year spent in England, he left for Harvard in the USA where he collaborated with Harlow Shapley, another great name of contemporary astronomy. In Boston, which is believed to be one of the most important academic centers of the world due to its elite universities, he also perfected his knowledge at the prestigious MIT, where he became even more drawn to cosmology and started to study models of the universe implied by Einstein’s completely new general theory of relativity. He obtained his doctoral degree at MIT before returning to Belgium and becoming a professor at the Catholic University of Leuven.
Soon after his return, he published the first drafts of his theory of the origin of the universe. Even though one might have expected that, as a Catholic priest, he would look to the biblical story of creation when forming his idea about the Big Bang, this was far from so. His inspiration came from neither astronomy nor the theory of relativity, but from at the time completely new quantum physics. More specifically, he became inspired to form his idea about the primeval atom when studying the phenomenon of radioactivity.
Is the creation of the universe a mere coincidence?
It is known that radioactive elements are not stable, but decay with time, releasing energy. Even though one can not predict exactly when a particular radioactive atom would disintegrate completely it is possible to predict with great precision when, for instance, one half of the radioactive atoms in a multitude of identical atoms would disintegrate. When getting acquainted with the principles of quantum physics, Lemaître asked himself whether it might be more than a mere coincidence that the half-life of some radioactive elements comes very close to the estimations of the age of the universe, based on the measurements of the expansion rate of the universe. Could it be that we are living in some worn out version of a radioactive universe?
According to Lemaître’s original idea the universe began as a kind of a “large radioactive atom” which is why we can determine its exact age. The analogy between the universe and radioactivity was also of key importance in terms of overcoming the famous problem of explaining the very beginning of the universe. If we wanted to give a causal explanation of the first moment, we would have to refer to an even older event, but we can not do so for the very reason that we want to explain the very first event. Many different thinkers throughout history have dealt with this problem at length, but its most well-known formulation probably came from Immanuel Kant who described it as the first antinomy of pure reason.
The essential thing that one should keep in mind when dealing with radioactive atoms is that their disintegration is completely coincidental. It is impossible to predict when exactly a particular atom would disintegrate which is also why there no exact cause for its decay can be determined. It is completely unpredictable, only the probability that the decay will take place within a certain period of time can be predicted. Lemaître expanded his idea about the coincidental decay of the radioactive atom to his idea about the universe as the primeval atom to which all the laws of quantum physics must apply as well. Even though it does not describe exactly the same type of event, the analogy that Lemaître tried to establish is quite obvious. Just as a particular decay has no cause, even though it is dictated by exact laws of quantum physics, the universe as a whole might lack a cause, which still does not mean that exact physical laws do not apply to it.
The universe began shortly before the beginning of time
In 1931 he described his idea in an article published in Nature magazine in which he wrote, among other things: “If the world began with a single quantum particle, the concepts of time and space had no particular meaning in the beginning; they only acquired meaning when the original quantum particle multiplied to a substantial number of quanta. If this idea is correct, the beginning of the world took place just before the beginning of space and time.”
At first glance, this way of thinking might be something that one would never expect from a Catholic priest, but anyone who is familiar at least some of the history of the Christian theological thought will quickly realize that the similarity with the famous doctrine of creation is evident. Just as God, according to the doctrine of creation, is absolutely free in his creation of the world and is not subjected to any kind of limitations, thoughts or higher purposes, Lemaître’s primeval atom is completely free in terms of the moment it “chooses” to disintegrate.
Although the analogy with the coincidental radioactive disintegration was of key importance at the beginning, it became less and less relevant while the theory was being perfected. Lemaître himself developed his theory in the years to follow, founding it on the general theory of relativity, but it was considered to be much too unusual at the time to be accepted within the wider scientific community as a serious description of the actual universe and not merely as one of many hypotheses. In science, a rule exists that the more a theory is unusual, the stronger arguments and experimental proofs it needs in order to be accepted by the scientific community. As we have already mentioned, cosmic microwave background radiation, which meant a great contribution to the acceptance of the Big Bang theory, was only discovered a couple of decades after the Second World War, and the idea about the primeval atom was long regarded as an exotic hypothesis rather than a description of the actual history of the universe. Lemaître died soon after he had received the news about the discovery of cosmic microwave radiation which confirmed his visionary idea about the origins of the universe.
In 1936 he was elected member of the Pontifical Academy of Sciences which advises the Pope on matters relating to science. In 1960 he even became its president and kept the post until his death in 1966. He always defended the belief that there is no ideological conflict between science and religion. He claimed this to be true as a high dignitary of the Church as well as one of the most esteemed scientists of his age.
He was not pleased when Pope Pius XII referred to science, including the cosmology of the Big Bang which had been his area of expertise all along, to try and prove that scientific and divine truths were actually one and the same. Even today, high Church dignitaries often declare that science has been coming to similar conclusions as those described in Church doctrines. According to them, The Big Bang theory is supposed to describe the development of the universe all the way back to the beginning of time with the exception of the first moment which is of course said to be the work of God
Lemaître strongly disagreed with such interpretations which have also been defended by later Popes: “In my opinion, the theory (of the primeval atom) remains beyond all metaphysical or religious questions. It allows the materialist to deny the existence of any transcendent Being. (…) At the same time it corresponds to the words of the prophet Isaiah who spoke of the ‘hidden’ God who was not even seen at the beginning of the universe …”
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