Georges Lemaître: The Father of the Big Bang Theory

Education Between Science and Faith

Born on July 17, 1894 in Charleroi (Belgium), Georges Henri Joseph Édouard Lemaître (1894-1966) showed an early interest in mathematics and physics. After secondary studies at the Jesuit College of the Sacred Heart, he entered the Catholic University of Louvain in 1911.

Academic background:

• 1913: Began civil engineering studies
• 1914-1918: Military service during World War I (artillery)
• 1919: Resumed studies and obtained a PhD in physics and mathematics (1920)
• 1920: Entered the seminary of Mechelen and was ordained priest in 1923
• 1923: Studies at Cambridge University with Arthur Eddington
• 1924-1925: Stay at Harvard College Observatory and MIT

This unique training, combining science and theology, made him a thinker capable of reconciling faith and scientific reason.

The Primeval Atom Theory (1927-1931)

1. Initial Hypothesis (1927)

In an article published in 1927 in the Annales de la Société Scientifique de Bruxelles, Lemaître proposed a solution to Einstein's general relativity equations that implied an expanding universe:

• First to suggest that the universe began from a "primeval atom"
• Derived equations describing an expanding universe (before Hubble's observations)
• Proposed that the redshift of galaxies was due to this expansion

Einstein, initially skeptical, reportedly said: "Your calculations are correct, but your physics is abominable."

2. Confirmation by Hubble (1929-1931)

After Edwin Hubble's discovery of the velocity-distance relation in 1929, Lemaître published in 1931 in Nature a foundational article where he:

• Explicitly proposed the primeval atom theory (future Big Bang theory)
• Estimated the age of the universe at about 10-20 billion years
• Introduced the notion of cosmic background radiation (discovered later in 1965)

His article began with these famous words: We could conceive of space as having been initially filled with a kind of super-dense fluid...

Major Contributions to Cosmology

1. Cosmological Constant

Lemaître proposed an original interpretation of Einstein's cosmological constant:

• Suggested it could represent a vacuum energy
• Proposed a model of accelerating universe expansion (precursor to dark energy)
• These ideas were confirmed in 1998 with the discovery of the acceleration of expansion

2. Hubble-Lemaître Law

Although often attributed solely to Hubble, this fundamental relation also bears Lemaître's name:

• Linear relationship between velocity and distance: \(v = H_0 \times d\)
• Lemaître calculated the first estimate of \(H_0\): ~625 km/s/Mpc
• Proposed that this expansion implies a beginning of the universe

3. Other Scientific Contributions

Lemaître also worked on:

• Theory of cosmic tides
• Three-body problem in celestial mechanics
• Cosmic rays (with Robert Millikan)

Academic Life and Recognition

Professional career:

• 1925: Part-time professor at the Catholic University of Louvain
• 1927: Full-time professor and creation of a theoretical physics center
• 1936: Member of the Pontifical Academy of Sciences
• 1941: Elected to the Royal Academy of Belgium
• 1960: Received the Francqui Prize, Belgium's highest scientific distinction

International recognition:

• Foreign member of the Royal Astronomical Society (1927)
• Eddington Medal (1934)
• Member of the International Astronomical Union

Lemaître and the Relationship Between Science and Faith

As both a priest and scientist, Lemaître had a particular view of the relationship between science and religion:

• "Science and faith are two distinct domains that should not be mixed"
• Opposed the use of his theory to prove the existence of God
• Believed in a Creator God, but not in a "God of the gaps" to explain scientific unknowns

He stated: "The primeval atom theory is a neutral scientific theory, without religious implications."

Legacy and Posterity

Lemaître died on June 20, 1966 in Louvain, leaving an immense scientific legacy:

• Father of the Big Bang theory (term coined by Fred Hoyle in 1949)
• Pioneer of modern cosmology
• Inspiration for space missions like COBE (1989) and Planck (2009)
• His name was given to:
  • Asteroid (1565) Lemaître
  • Lunar crater Lemaître
  • Euclid space telescope (ESA mission, 2023)

In 2018, the International Astronomical Union officially renamed Hubble's law as the Hubble-Lemaître law to recognize his fundamental contribution.