by Sophie Pelland
You were there at the Big Bang, but at that time, each of your particles
was living its independent life. Hubert Reeves, a nuclear astrophysicist
best known to the public for his popularization of cosmology, gave about
60 fascinated listeners a short course in the history of the universe
on Oct. 7.
His presentation, called The Universe Has a History, was the
first of this years Montreal Inter-University Seminars on the History
and Philosophy of Science, organized by Concordias Science College.
For about an hour, Reeves discussed what he considers the most important
scientific discovery of the 20th century: that our universe is not static,
but has a varied history.
Before this discovery, scientists from Aristotle to Einstein considered
the cosmos to be an essentially changeless backdrop disconnected from
the bustle of life on Earth. Questions about how stellar objects formed
were considered meaningless or beyond the scope of science.
Starting in the 1920s, evidence to the contrary began to accumulate. In
1929, Edwin Hubbles observations of galaxies revealed that the universe
Viewed in reverse, this expansion becomes a contraction. Extrapolating
the contraction back in time provides the framework of the Big Bang theory:
an early universe that was extremely dense, hot and bright expanding over
time to become progressively darker, cooler and less dense.
Although the Big Bang model had been derived independently by Friedmann
(1922) and Lemaître (1927) by the time of Hubbles discovery,
the model was not accepted until decades later. As Reeves emphasized,
observational evidence was crucial in overcoming opposition and indifference
to the model.
Penzias and Wilson provided a key piece of evidence in its favour in 1965,
when they accidentally discovered a relic of the Big Bang predicted by
Gamow (1948) and Alpher and Herman (1949): microwave radiation at a temperature
of 2.7 degrees Kelvin (or 270.5 degrees Celsius) pervading all of
With the discovery of the so-called cosmic background radiation, the community
of physicists and astronomers truly began what Reeves describes as the
exploration of time, or the systematic mapping of the history of
The current standard model of cosmology, based on the Big Bang scenario,
provides a coherent account of how structure gradually emerged from collisions
between the individual elementary particles that made up the early universe.
As Reeves explained, the universe is structured like language, with elementary
particles playing the role of letters. As the universe cooled, the elementary
particles were able to form stable structures ranging from nuclei and
atoms to stars and galaxies, much like letters organizing into words and
sentences. Reeves smiled as he told his audience, You are made of
When Reeves had finished his presentation, the question period threatened
to go on indefinitely, as members of the audience clamoured for clarifications
and opinions. Typically, Reeves answered the questions with the simplicity
and clarity that has won his popular science books and television programs
An expert on the production of light elements in the early universe, Montreal-born
Hubert Reeves is the retired director of the prestigious Centre National
de la Recherche Scientifique in Paris, and the recipient of numerous prizes
and awards, including the Order of Merit of the French government and
the 2001 Einstein Prize.
Although he is 70 and retired, Reeves is still active as a teacher, researcher
and public lecturer. Not content to study the universes past, he
is also deeply interested and concerned about its future, and is well-known
for his involvement in environmental protection.
In fact, he delivered a talk on Global Environmental Governance (the importance
of the Kyoto protocol) on Oct. 15 at Montréals Palais des
Congrès as part of an international conference on Civil SocietyGlobal
The next Interuniversity Seminar on the History and Philosophy of
Science will take place on Nov. 11 at 4:15 p.m. in Room H-609 of the Henry
F. Hall Building.