Tag Archives: Lemaître

History of Science & Epistemology, My books & articles, Sciences

The Big Bang Revolutionaries

Leave a comment

The Big Bang Revolutionaries  : The Untold Story of Three Scientists Who Reenchanted Cosmology

by Jean-Pierre Luminet

Many widely read scientific writers of our day mistakenly attribute the concepts of the expanding universe and the Big Bang to Edwin Hubble and Albert Einstein. Hubble did provide evidence of an expanding universe, but he neither discovered such evidence nor accepted the radical idea that space itself was expanding. As for Einstein, he held out against the idea of an expanding universe for more than a decade, and ceased working in the field as soon as he had to amend his view. The real heroes of the Big Bang revolution are the Russian Alexander Friedmann and Belgian priest Georges Lemaître. That they are virtually unknown to the general public is one thing. That their contribution is underestimated by astrophysicists and cosmologists is another, for the concepts they promulgated are among the most remarkable achievements of twentieth-century science. The Big Bang Revolutionaries amends the record, telling the remarkable story of how these two men, joined by the mischievous George Gamow and in the face of conventional scientific wisdom, offered a compelling view of a singular creation of the universe in what Lemaître termed a “primeval atom.”

Publisher : Discovery Institute Press
Published : April 23, 2024
ISBN : 978-1-63712-040-8
Pages : 254
Retail Price : $18.95

Jean-Pierre Luminet, a French astrophysicist specializing in black holes and cosmology, is emeritus research director at the French National Centre for Scientific Research. He is a member of the Laboratoire d’Astrophysique de Marseille (LAM) and Laboratoire Univers et Théories (LUTH) of the Paris-Meudon Observatory. Luminet has been awarded several prizes. These include the Georges Lemaître Prize (1999) for his work in cosmology, the UNESCO Kalinga Prize (2021), and the Einstein medal for the Popularization of Science (2021). He has published more than twenty science books, eight historical novels, and eight poetry collections. The asteroid 5523 Luminet was named in his honor.

Advance Praise

This excellent and well-illustrated book convincingly puts into a clear focus the key original contributions of Friedmann and Lemaître in the early twentieth-century revolution in our understanding of the large-scale physical universe.

Roger Penrose, Emeritus Rouse Ball Professor of Mathematics at the Mathematical Institute of the University of Oxford, Emeritus Fellow of Wadham College at Oxford, fellow of the Royal Society, and recipient of the Wolf Prize (1988) and the Nobel Prize in Physics (2020)

The author brings together many aspects of thinking about the large-scale nature of our world from the points of view of concepts, theory, observation, and culture. The account starts with Albert Einstein’s thought that a philosophically satisfactory universe has no boundary, a bold conjecture that proved to fit well with Einstein’s new gravity theory and now agrees with the observational evidence. You will find fascinating details of the evolution of ideas, evidence, and the cultural situation between that time and the early steps by which George Gamow’s brilliant intuition took him to the realization that an even better picture of our universe is that it expanded from a hot dense state.

Jim Peebles, the Albert Einstein Professor in Science, emeritus, Princeton University, and recipient of the 2019 Nobel Prize in Physics

It is rare to find an internationally distinguished astrophysicist who is also a searching and meticulous historian. It is rarer still to find such a person who is also a gifted prose stylist. Jean-Pierre Luminet is such a man. The Big Bang Revolutionaries is invaluable reading for anyone fascinated by the history of the big ideas that have shaped and reshaped Western science and civilization, and for anyone who wants a front row seat to witness the all-too-common character of scientific revolution—messy, full of unexpected twists and turns, and not without its casualties. In the present case and as Luminet dramatically shows, the revolution occurred in the face of sustained prejudice from some of the finest minds in physics and astronomy. As for the wider implications of the Big Bang revolution, Luminet leaves those for the reader to contemplate.

Stephen C. Meyer, Director of the Center for Science and Culture and author of Signature in the Cell, named a Book of the Year by the Times (of London) Literary Supplement, Return of the God Hypothesis, and the New York Times bestseller Darwin’s Doubt

The twentieth century represents an exceptional period in the study of the cosmos. But this century will be remembered above all as the one in which physics, for the first time, made it possible to study the universe and its evolution. Jean-Pierre Luminet, an eminent cosmologist, takes the role of historian in this analysis of the emergence of ideas, and pays tribute to the physicists who contributed to this dizzying scientific adventure.

Michael Mayor, Swiss astrophysicist and professor emeritus at the University of Geneva; a recipient of the Viktor Ambartsumian International Prize (2010), the Kyoto Prize (2015), and the Nobel Prize in Physics (2019)

An inspiring overview of the history and physics of our modern view of the universe by the brilliant scientist Jean-Pierre Luminet, who was first to simulate black hole silhouettes. The reader is introduced to the scientific insights that revolutionized the perception of our cosmic roots and future. A fascinating read!

Abraham (Avi) Loeb, Frank B. Baird Jr. Professor of Science and Director of the Institute for Theory & Computation, Harvard University, and director for the Breakthrough Initiatives of the Breakthrough Prize Foundation

This book is a very careful discussion of the work of three less-known key figures who laid the foundations of modern cosmology—Alexander Friedmann, Georges Lemaître, and George Gamow. It does a great service in detailing the contributions that each of them made to the topic. I particularly appreciate the discussion of the pioneering work and personality of Lemaître, who can justly be called the father of scientific cosmology. With its discussion also of cosmic topology, the book is a unique contribution to the history of cosmology.

George Ellis, emeritus distinguished professor, University of Cape Town, co-author with Stephen Hawking of The Large Scale Structure of Space-Time, former president of the International Society on General Relativity and Gravitation, fellow of the Royal Society, recipient of the Templeton Prize and the Georges Lemaître International Prize

The Big Bang Revolutionaries is one terrific book. And one, I might add, of historical importance inasmuch as it restores to their rightful place two fascinating figures whom the standard history of physics in the twentieth century has shamefully neglected. Lucid? Of course it is lucid. Luminet is a fine astrophysicist. Moving? Very much so, not only for what it says about Friedmann and Lemaître, but for what it reveals about the author’s sensitive intelligence on encountering the story of men whose position of prominence was denied them. It is, all in all, a splendid restoration—something very French, I might add, in that it describes men who should have been monarchs reacquiring their thrones.

David Berlinski, Senior Fellow of the Center for Science and Culture, and author of A Tour of the Calculus, The Advent of the Algorithm, Newton’s Gift, The Devil’s Delusion: Atheism and Its Scientific Pretensions, and Science After Babel

Finally a book that brings the credit of the great cosmological revolution of the twentieth century to where it is properly due: the Russian Alexander Friedmann and the Belgian priest Georges Lemaître.

Carlo Rovelli, founder of the quantum gravity group of the Centre de Physique Théorique (CPT), Aix-Marseille University, and author of the bestselling Seven Brief Lessons on Physics

Big Bang theory has become a popular topic, but who knows the scientists who first proposed the outrageous concept that our entire universe started as an ultra-dense fireball? Theoretical physicist Jean-Pierre Luminet, well-known for his pioneering work on the visualization of black holes, takes the reader through a pedagogical, and historically accurate, tour of the conceptual vistas opened by the inventors of Big Bang theory, namely: the Russian mathematician (and meteorologist) Alexander Friedmann, the Belgian cosmologist (and priest) Georges Lemaître, and, last but not least, the eclectic genius physicist George Gamow. A must-read for any person eager to understand one of the major scientific breakthroughs of twentieth-century physics.

Thibault Damour, Institut des Hautes Études Scientifiques, recipient of the Einstein medal, the Galileo Galilei medal, and the Balzan prize

Astronomy

The Rate of Expansion

Leave a comment

There, where worlds seem, with slow steps,
Like an immense and well-behaved herd,
To calmly graze on the ether’s flower.
Giovanni Pascoli, Il Ciocco

A question often asked by the general public interested in cosmology about the expansion of the Universe is the distance scales on which it effectively acts. Before commenting on this, let me recall first some historical facts.

Georges Lemaître in 1927

In 1927, Georges Lemaître published a revolutionary article in the Annales de la Société scientifique de Bruxelles entitled “Un univers homogène de masse constante et de rayon croissant, rendant compte de la vitesse radiale des nébuleuses extragalactiques” (“A homogeneous universe of constant mass and increasing radius, accounting for the radial velocity of extragalactic nebulae.” As the title suggests, Lemaître showed that a relativistic cosmological model of finite volume, in which the Universe is in perpetual expansion, naturally explains the redshifts of galaxies, which at that point were not understood. In particular, the article contained a paragraph establishing that forty-two nearby galaxies, whose spectral shifts had been measured, were moving away at speeds proportional to their distances.

Lemaître gave the numerical value of this proportionality factor: 625 km/s per megaparsec, which means that two galaxies separated by 1 megaparsec (or 3,26 million light-years) moved away from each other at an apparent speed of 625 km/s, and that two galaxies separated by 10 megaparsecs moved apart at a speed ten times greater.

The paragraph of Lemaître’s paper in which he derives the law of proportionality between recession velocity and distance, later called the Hubble law.

This unit of measurement, the kilometer per second per megaparsec, shows clearly that the speed of recession depends on the scale. In 1377, in his Book of the Heavens and the World, the scholar Nicole Oresme had noted that, at dawn, one would not notice anything if the world and all living creatures had grown by the same proportion during the night. In Lemaître’s theory, on the contrary, the recession velocity between two points in space grows faster with greater separation, which renders it perceptible.

Eddington and Lemaître

Lemaître’s article, published in French, passed unnoticed until 1931, when it was finally read by Arthur Eddington, who published an English translation. Unfortunately, this version omits the paragraph in which Lemaître established his law of proportionality, see this article for all the details. Meanwhile, in 1929 the great American astronomer Edwin Hubble had published the experimental results he obtained with his collaborators and described a general law, according to which the speed of recession of a galaxy is proportional to its distance. This law, identical to Lemaître’s, with the same proportionality factor, would from now on carry the name of “Hubble’s law.” It forms the experimental basis for the theory of the expansion of the Universe, of which the big bang models are the fruit. Continue reading →

Astronomy, My books & articles, Sciences

Galaxies in Flight

Leave a comment

This post is an adaptation of a chapter of my book  “The Wraparound Universe” with many more  illustrations.

 

Galaxies in Flight

                     The spawning galaxy in flight is a rainbow trout which goes
back against the flow of time towards the lowest waters, towards the dark retreats of duration.
Charles Dobzynski (1963)

Since the time of Newton, we have known that white light, passing through a prism, is decomposed into a spectrum of all colors. Violet and blue correspond to the shortest wavelengths or, equivalently, to the largest frequencies; red corresponds to the largest wavelengths and to low frequencies. In 1814, the German optician Joseph von Fraunhofer discovered that the light spectrum from stars is streaked with thin dark lines, while that from candlelight has bright stripes. These phenomena remained puzzling until 1859. It was then that the chemist Robert Bunsen and the physicist Gustav Kirchhoff analyzed the light created from the combustion of different chemical compounds (burned with the now-famous Bunsen burner) and saw that each of them emitted light with its own characteristic spectrum.

Fraunhofer lines in the solar spectrum

At nearly the same time, Christian Doppler discovered in 1842 that moving the source of a sound produced shifts in the frequency of sound waves, a phenomenon experienced by anyone listening to the siren of an ambulance passing by. The French physicist Armand Fizeau noticed the same phenomenon with light waves: depending on whether a source of light was moving closer or farther away, the received frequencies are either raised or lowered with respect to the emitted frequencies. The shift becomes larger as the speed of displacement is increased. If the source is getting closer, the frequency grows, and the light becomes more “blue”; if it moves away, the frequency lowers and the wavelengths stretch out, becoming more “red,” with respect to the spectrum of visible light. Since this shift affects the whole spectrum by the same amount, it is easily quantified by looking at the dark or bright stripes, which are shifted together, either towards the blue or towards the red, and it furnishes an incomparable means of measuring the speed of approach or retreat for light sources.

Shortly after this discovery, astronomers began an ambitious program of spectroscopy, with the aim of measuring the speed of the planets and stars by using their spectral shifts. Continue reading →

My books & articles, Sciences

Expansion and the Infinite

Leave a comment

This post is an adaptation of a chapter of my book  “The Wraparound Universe” with many more  illustrations.

Expansion and the Infinite

Space alike to itself
that it grows or denies itself
Stéphane Mallarmé

The Universe is expanding. What does this really mean? Most people imagine an original huge explosion, as the term “big bang” suggests, and the metaphor is constantly used in popular accounts. Some speakers even have the tendency to mime a gesture of expansion with their hands, as if they were holding a piece of space or an immaterial balloon in the process of inflating. The public imagines some matter ejected at prodigious speeds from some center, and tell themselves that it would be better not to be there at the moment of explosion, so as not to be riddled through with particles.

A misleading view of the expanding universe commonly used in popular science

None of all this is accurate. At the big bang, no point in the Universe participated in any explosion. Put simply, if one considers any point whatsoever, we notice that neighboring points are moving away from it. Is this to say that these points are animated by movement, given a speed? No, they are absolutely fixed, and nevertheless they grow apart.

To unravel this paradox, it is necessary to make more precise what one exactly means when speaking of a fixed point. The position of a point is fixed by coordinates: one number for a line (the miles along a highway), two numbers for a surface (latitude and longitude), and three for space in general (length, width, and height). A point is said to be fixed if its coordinates do not change over the course of time. In an arbitrary space, curved or not, the distance between two points is given by the so-called metric formula, which depends on the coordinates and generalizes the Pythagorean theorem. In principle, therefore, the distance between two points does not vary. In an expanding space, on the other hand, this distance grows, while the points do not move, even by a millimeter, meaning that they strictly conserve the same coordinates. These fixed coordinates are known as “comoving” coordinates. In relativistic cosmology, galaxies remain fixed at comoving positions in space. They may dance slight arabesques around these positions, under the influence of local gravitational fields, but the motion which moves them apart from each other resides in the literal expansion of the space which separates them. Continue reading →

Astronomy, History of Science & Epistemology, My books & articles, Sciences

Cosmogenesis (9) : The Big Bang Discovery

1 Comment

Sequel of the preceding post Cosmogenesis (8) : The Nebular Hypothesis

Star Clusters and Nebulae. This page from "Telescopic views of Nebulae and Clusters by the Earl of Rosse and Sir J. Herschel" (1875) includes a variety of drawings of nebulosities by different observers. There are star clusters and gaseous nebulae (now known to belong to our own galaxy) as well as other galaxies. Observational techniques of the time were unable to distinguish between these very different types of objects.
Star Clusters and Nebulae. This page from “Telescopic views of Nebulae and Clusters by the Earl of Rosse and Sir J. Herschel” (1875) includes a variety of drawings of nebulosities by different observers. There are star clusters and gaseous nebulae (now known to belong to our own galaxy) as well as other galaxies. Observational techniques of the time were unable to distinguish between these very different types of objects.

In the first quarter of the 20th century cosmology became a distinct scientific discipline, thanks in part to the theoretical advance made in 1915 by Einstein with his theory of general relativity and in part to the revolution in observational techniques which revealed the true extent of the universe. Having at last been able to measure the distance of certain spiral nebulae, Edwin Hubble could confirm in 1925 that there existed other galaxies like our own.

His colleague Vesto Slipher had previously discovered that the radiation from these galaxies was constantly shifting towards the red end of the optical spectrum, which suggested that they were moving away from us at great speed. This movement was not understood until scientists came to accept an idea based on the theory of general relativity and first proposed by Alexandre Friedmann in 1922 and independently Georges Lemaître in 1927: that space was constantly expanding and consequently increasing the distance between galaxies. This idea proved to be one of the most significant discoveries of the century[i].

Alexander Friedmann in 1922
Alexander Friedmann in 1922

In an article which appeared in 1922, entitled “On the Curvature of Space“, Friedmann took the step which Einstein had balked at: he abandoned the theory of a static universe, proposing a “dynamic” alternative in which space varied with time. For the first time the problem of the beginning and the end of the universe was couched in purely scientific terms. Friedmann suggested that the universe was several tens of billions of years old, much older than the earth (then estimated to be about one billion years old) or the oldest known celestial objects. It was a remarkable prediction, the most recent estimate for the age of the universe being between 10 and 20 billion years.

In 1927, in a seminal article entitled “A Homogeneous Universe of Constant Mass and Increasing Radius Accounting for the Radial Velocity of Extra-Galactic Nebulae“, Lemaître explained the observations of Hubble and Slipher by interpreting them, within the context of general relativity, as manifestations of the expansion of the universe. This expansion was taking place uniformly across the entire universe (which might be finite or infinite), not outwards from a particular point (in this sense the often quoted analogy of a balloon being inflated is misleading). It was not a case of matter moving within a fixed geometric framework, but of the framework itself dilating, of the very “fabric” of space-time stretching. Continue reading →

History of Science & Epistemology, Sciences

The Rise of Big Bang Models (4) : Lemaître

1 Comment
Sequel of previous post : Dynamical solutions

In this series of posts about the history of relativistic cosmology, I  provide an epistemological analysis of the developments of the field  from 1917 to 2006, based on the seminal articles by Einstein, de Sitter, Friedmann, Lemaître, Hubble, Gamow and other main historical figures of the field. It appears that most of the ingredients of the present-day standard cosmological model, including the accelation of the expansion due to a repulsive dark energy, the interpretation of the cosmological constant as vacuum energy or the possible non-trivial topology of space, had been anticipated by Lemaître, although his papers remain mostly  unquoted.

The discovery of expanding space

The 1920’s were precisely the time when the experimental data began to put in question the validity of static cosmological models. For instance, in 1924 the British theorist Arthur Eddington pointed out that, among the 41 spectral shifts of galaxies as measured by Vesto Slipher, 36 were redshifted ; he thus favored the de Sitter cosmological solution while, in 1925, his PhD student, the young Belgian priest Georges Lemaître, proved a linear relation distance-redshift in de Sitter’s solution. The same year 1925, Edwin Hubble proved the extragalactic nature of spiral nebulae. In other words, he confirmed that there existed other galaxies like our own, and the observable Universe was larger than previously expected. More important, the radiation from the faraway galaxies was systematically redshifted, which, interpreted as a Doppler effect, suggested that they were moving away from us at great speed. How was it possible ?

Arthur Eddington (1882-1944)
Arthur Eddington (1882-1944)

Young-Lemaitre
The young Georges Lemaître

It was Lemaître who solved the puzzle. In his 1927 seminal paper Un univers homogène de masse constante et de rayon croissant, rendant compte de la vitesse radiale des nébuleuses extragalactiques, published in French in the Annales de la Société Scientifique de Bruxelles, Lemaître calculated the exact solutions of Einstein’s equations by assuming a positively curved space (with elliptic topology), time varying matter density and pressure, and a non-zero cosmological constant. He obtained a model with perpetual accelerated expansion, in which he adjusted the value of the cosmological constant such as the radius of the hyperspherical space R(t) constantly increased from the radius of the Einstein’s static hypersphere RE at t = – ∞. Therefore there was no past singularity and no « age problem ». The great novelty was that Lemaître provided the first interpretation of cosmological redshifts in terms of space expansion, instead of a real motion of galaxies : space was constantly expanding and consequently increased the apparent separations between galaxies. This idea proved to be one of the most significant discoveries of the century. Continue reading →