Nearly a century after a Belgian priest proposed the “Big Bang” theory, astronomers peer back in time to the first galaxies
By Christopher M. Graney
Question: A Catholic priest and the James Webb Space Telescope both look at the universe. What do they see?
Answer: A day without a yesterday!
If that sounds like a bad attempt at a “dad joke,” it’s not. It is actually true — and something we should keep in mind when we look at the spectacular images from the JWST, the space telescope NASA launched in 2021.
A century ago, Father Georges Lemaître, a Belgian priest who was also a physicist, looked at what was being learned about the universe. He also looked at the then-new ideas of Albert Einstein. Father Lemaître concluded that science suggested there was once a beginning to everything — even time itself. There was once, in his words, a “now which has no yesterday.”
Scientists had long thought of the universe as beginningless, changeless and eternal. “We [scientists] expected the universe to be static,” Father Lemaître stated in a 1964 interview. “We expected that nothing would change. It was an a priori idea that applied to the whole universe … for which there was no experiment.”
An a priori idea — an assumption. Since at least the time of Aristotle, several centuries before Christ, scientists had operated on this assumption. The changeless universe just went through endless (and beginningless) cycles. This makes some sense. The sun rises and sets daily. The moon goes through its phases — crescent, quarter, full — every month. The stars seen in the evening sky change in a yearly cycle; the deepening twilight of every Christmas Eve always reveals Orion rising in the east. We see the same sun, moon and stars that our great-grandparents saw. Even Job in the Bible knew the constellations we see today:
God alone stretches out the heavens
and treads upon the crests of the sea.
He made the Bear and Orion, the Pleiades
and the constellations of the south. (Job 9:8-9)
The changeless night sky suggested a changeless universe.
SCIENCE ‘VERSUS’ RELIGION
The idea that science challenges religious ideas is a commonplace. As Pope Benedict XVI noted in his spiritual testament, “Often it seems as if science … has irrefutable insights to offer that are contrary to the Catholic faith.” However, Pope Benedict understood that the challenge is not new, and he emphasized that these seeming contradictions, viewed over the longer term, vanish with further understanding.
They even vanished in the case of Aristotle’s changeless universe, which presented a real challenge to the biblical image of creation.
Across much of Church history, theologians held that there was no contradiction between the Book of Genesis and the view that the universe had no beginning in time — because God still created, and continually creates, the universe. Yes, there are some mental gymnastics in that, with God being outside of time, with Genesis being a metaphorical description of creation, and so on. Of course, as Father Lemaître noted, there was no hard evidence that the universe was unchanging, no experiment that said Aristotle was right. It’s just that Aristotle’s ideas made some sense, and he was so widely respected that theologians had to take his ideas seriously, even if they seemingly conflicted with Genesis.
A tougher problem was in the biblical description of God creating “the two great lights” — the sun and moon — and the stars (Gen 1:14-16). As early as the days of St. Augustine, in the late fourth century, astronomers concluded that even though the stars look small in the night sky, they are in fact much larger than the moon, just much more distant. This conclusion that the moon was not so “great” involved hard evidence — careful measurements and applied geometry — and not merely a priori assumptions.
However, St. Augustine was unconcerned about this apparent conflict. It may be true, he wrote in On the Literal Interpretation of Genesis, that the stars are large, and merely “seem small because they have been set further away.” But, he said, “at least grant this to our eyes … it is obvious that the sun and moon shine more brightly than the rest upon the Earth.” St. Thomas Aquinas, writing in the 13th century, was not concerned either. “The two lights are called great, not so much with regard to their dimensions as to their influence and power,” he wrote in the Summa Theologica. “For though the stars be of greater bulk than the moon … as far as the senses are concerned, its apparent size is greater.” With a little of that further understanding that Pope Benedict described, namely that Genesis is not written to provide a scientific description of the physical dimensions of the moon and stars, any contradiction between Genesis and science here vanished.
(Then why did Galileo so famously run into difficulty? His discoveries were striking, and all confirmed by church astronomers. But his interpretation of those discoveries as supporting a moving Earth — Scripture spoke of Earth as fixed — was much less persuasive than the case for the greatness of stars.)
FATHER LEMAÎTRE’S THEORY
By Father Lemaître’s time, what scientific discoveries were contradicting was the long-established idea of a beginningless, changeless universe. Heat energy flow, fossils, Einstein’s theory of gravity, the motions of galaxies — they all suggested that the universe changed over time.
Building on Einstein’s ideas and supported by Edwin Hubble’s evidence that the universe is expanding, in 1931 Lemaître proposed what he called “the hypothesis of the primeval atom,” in which the universe and time itself all begin at once. He later described his hypothesis in the 1964 interview noted above: “There is a beginning very different from the present state of the world … described in the form of the disintegration of all existing matter into an atom. What will be the first result of this disintegration, as far as we can follow the theory, is in fact to have a universe, an expanding space filled by a plasma, by very energetic rays going in all directions.” This universe continued to expand and change, becoming in time the universe we see today.
In the 1940s, the astronomer Fred Hoyle dubbed Lemaître’s idea the “Big Bang.” Hoyle was not paying a compliment, but with time, the name stuck.
Father Lemaître’s Big Bang idea aligned with Genesis better than Aristotle’s unchanging universe; in both Genesis and the Big Bang there is a beginning! Indeed, in a 1951 address to the Pontifical Academy of Sciences, Pope Pius XII stated that science might be “entirely reconcilable” with the idea of creation, since “It seems that the science of today, by going back in one leap millions of centuries, has succeeded in being a witness to that primordial Fiat Lux [Let there be light], when, out of nothing, there burst forth with matter a sea of light and radiation, while the particles of chemical elements split and reunited in millions of galaxies … [although] the facts pertinent to natural sciences … still wait for further investigation and confirmation.”
The story goes that Father Lemaître quietly cautioned the Holy Father after this statement. What if further investigation showed Lemaître’s theory to be wrong, just as science had shown the long-standing changeless universe theory to be wrong? Indeed, the seemingly solid, persuasive astronomy of St. Augustine’s time, about the star and moon sizes, turned out to be wrong (yes, today we know that stars are large, but we know that based on entirely different evidence than the astronomers of Augustine’s time used).
Science is not like math. Pick up a 150-year-old math textbook and you can still learn from it the Pythagorean theorem or how to divide fractions. Pick up an astronomy text of that age, and it will explain neither what galaxies are nor that nuclear reactions power stars. Indeed, the Webb telescope exists so we can discover new things and thus modify our science based on new evidence.
Nevertheless, the JWST is built on the hope that changes in the study of astronomy are bringing us toward a truer view of the universe. The telescope is specifically “tuned” to Father Lemaître’s ideas. It is designed to see the most distant objects, whose light waves have been “stretched” by the expansion of the universe to now appear as longer-wavelength infrared light. Because of the time it takes light to travel such distances, the JWST will be seeing those objects as they appeared in the early days of the universe — showing us, we hope, the first stars and galaxies to form after Father Georges Lemaître’s Big Bang, on that dazzling “day without a yesterday.”
CHRISTOPHER M. GRANEY is an astronomer and historian of science with the Specola Vaticana (the Vatican’s astronomical observatory) in Rome and Tucson, Ariz. He is a member of St. Louis Bertrand Council 10682 in Louisville, Ky.