Context: Lost’ interview of Georges Lemaître rediscovered. The VRT has found in its archives an interview with Georges Lemaître that was thought to be lost. The cosmologist from Louvain was the founder of the big bang theory in the 1920s and 1930s. Now the entire 20-minute interview has been found.
What is Big Bang Theory?
- In 1927, an astronomer named Georges Lemaître had a big idea. He said that a very long time ago, the universe started as just a single point. He said the universe stretched and expanded to get as big as it is now, and that it could keep on stretching.
- Big Bang hypothesis states that all of the current and past matter in the Universe came into existence at the same time, roughly 13.8 billion years ago. At this time, all matter was compacted into a very small ball with infinite density and intense heat called a Singularity. Suddenly, the Singularity began expanding, and the universe as we know it began.
- Although this type of universe was proposed by Russian mathematician Aleksandr Friedmann and Belgian astronomer Georges Lemaître in the 1920s, the modern version was developed by Russian-born American physicist George Gamow and colleagues in the 1940s.
- While this is not the only modern theory of how the Universe came into being – for example, there is the Steady State Theory or the Oscillating Universe Theory – it is the most widely accepted and popular. Not only does the model explain the origin of all known matter, the laws of physics, and the large scale structure of the Universe, it also accounts for the expansion of the Universe and a broad range of other phenomena.
Assumptions
- The big-bang model is based on two assumptions :
- The first is that Albert Einstein’s general theory of relativity correctly describes the gravitational interaction of all matter.
- The second assumption, called the cosmological principle, states that an observer’s view of the universe depends neither on the direction in which he looks nor on his location.
- This principle applies only to the large-scale properties of the universe, but it does imply that the universe has no edge, so that the big-bang origin occurred not at a particular point in space but rather throughout space at the same time.
- These two assumptions make it possible to calculate the history of the cosmos after a certain epoch called the Planck time. Scientists have yet to determine what prevailed before Planck time.
Details of the Big bang theory
- According to the big-bang model, the universe expanded rapidly from a highly compressed primordial state, which resulted in a significant decrease in density and temperature.
- Soon afterward, the dominance of matter over antimatter (as observed today) may have been established by processes that also predict proton decay.
- During this stage many types of elementary particles may have been present. After a few seconds, the universe cooled enough to allow the formation of certain nuclei.
- The theory predicts that definite amounts of hydrogen, helium, and lithium were produced.
- Their abundances agree with what is observed today.
- About one million years later the universe was sufficiently cool for atoms to form. The radiation that also filled the universe was then free to travel through space.
- This remnant of the early universe is the cosmic microwave background radiation—the “three degrees” (actually 2.728 K) background radiation—discovered in 1965 by American physicists Arno A. Penzias and Robert W. Wilson.
- In addition to accounting for the presence of ordinary matter and radiation, the model predicts that the present universe should also be filled with neutrinos, fundamental particles with no mass or electric charge.
- The possibility exists that other relics from the early universe may eventually be discovered.
About Steady State Theory
- The steady-state theory, in cosmology, a view that the universe is always expanding but maintaining a constant average density, with matter being continuously created to form new stars and galaxies at the same rate that old ones become unobservable as a consequence of their increasing distance and velocity of recession.
- A steady-state universe has no beginning or end in time, and from any point within it the view on the grand scale—i.e., the average density and arrangement of galaxies—is the same. Galaxies of all possible ages are intermingled.
- The theory was first put forward in 1948 by British scientists Sir Hermann Bondi, Thomas Gold, and Sir Fred Hoyle.
- It was further developed by Hoyle to deal with problems that had arisen in connection with the alternative big-bang hypothesis.
- Observations since the 1950s (most notably, those of the cosmic microwave background, which was predicted by the big-bang model) have produced much evidence contradictory to the steady-state picture and have led scientists to overwhelmingly support the big-bang model.
Georges Lemaître
- Georges Lemaître, Belgian astronomer and cosmologist who formulated the modern big-bang theory, which holds that the universe began in a cataclysmic explosion of a small, primeval “super-atom.”
- It was because Lemaître was the originator of the Big Bang theory of the universe’s origin and derived an important law that cosmologists still use to understand the motion of galaxies away from each other.
- In 1927, the year he became a professor of astrophysics at the Catholic University of Leuven (Louvain), he proposed his big-bang theory, which explained the recession of the galaxies within the framework of Albert Einstein’s theory of general relativity.
- Although expanding models of the universe had been considered earlier, notably by the Dutch astronomer Willem de Sitter, Lemaître’s theory, as modified by George Gamow, has become the leading theory of cosmology.
- Lemaître also did research on cosmic rays and on the three-body problem, which concerns the mathematical description of the motion of three mutually attracting bodies in space.
- First, Lemaître discusses the arguments by which the Big Bang theory replaced steady state theory, under which Fred Hoyle and others claimed that the universe was static, that the galaxies that were there had always just been there.
- His works include Discussion sur l’évolution de l’univers (1933; “Discussion on the Evolution of the Universe”) and L’Hypothèse de l’atome primitif (1946; The Primeval Atom: An Essay on Cosmogony).