The Day Without Yesterday
The year was 1929 and for many Americans it seemed like a day with no tomorrow. Hardly noticed in the midst of the socio-economic cataclysm was the work of an obscure Belgian priest-scientist who was making history of an altogether otherwordly sort. Georges-Henri Lemaitre’s new cosmology predicted “a day without yesterday.”
The story begins several years earlier when Albert Einsten, having already rocked the scientific world with his theory of Special Relativity, published a new theory that demolished Newton’s hugely successful 1687 law of Universal Gravitation.
In 1915, Einstein presented a series of lectures before the Prussian Academy of Sciences in which he described a new theory of gravity known as General Relativity wherein Einstein’s field equations replaced Newton's law of gravity. In General Relativity, gravity is no longer a force but is a consequence of the curvature of space-time that is in turn determined by mass and energy. Einstein’s equations written in compact form are
R - (1/2) R g = T,
where R is the Ricci tensor, R is the Ricci scalar, g is the metric tensor and T is the energy-momentum tensor. Suffice to say that the equations immediately predicted the observed but non-Newtonian precession of the planet Mercury. Then in 1919, during a solar eclipse, Arthur Eddington took measurements of the bending of star light as it passed close to the Sun, resulting in star positions appearing further away from the Sun. These observations also match the predictions of General Relativity.
But what else did the new General Relativity reveal? Since the field equations are non-linear, Einstein assumed that they were generally insoluble. Then in 1916 Karl Schwarzschild discovered an exact solution for the case of a spherically symmetric spacetime surrounding a massive object. Encouraged by that exact solution, in 1922, Alexander Friedmann found a solution in which the universe may expand or contract.
However, Einstein did not believe in a dynamic universe. After all, since Aristotle it had been thought that the universe was uniform and unchanging. Einstein was so sure that was the case that he mofified his field equations through the addition of a cosmological constant Lambda (L) that, with the correct value, yields a static universe. The modified equations read:
R - (1/2) R g + L g = T.
However, in addition to being an ad hoc assumption, the additional term made the equations unstable since the slightest deviation from an ideal state (a particular value of L) would still result in the universe expanding or contracting.
Then came the year of the stock market crash. But the other noteworthy event in 1929 was the publication by Edwin Hubble of convincing evidence for the idea that the universe is expanding. This resulted in Einstein dropping the cosmological constant L, referring to it as "the biggest blunder in my career".
What was not known in America at that time was that Fr. Georges Lemaitre had published a paper in 1927 in which he derived what became known as Hubble's Law, two years before Hubble.
In 1930, Eddington published an English translation of Lemaitre’s 1927 article with a long commentary. Fr. Lemaître was then invited to London in order to take part in a meeting of the British Association on the relation between the physical universe and spirituality. There he proposed an expanding universe which started with an initial singularity and the idea of the Primeval Atom which was later to be coined (by Fred Hoyle, a critic) as the Big Bang theory. Fr. Lemaître himself liked to describe his theory as the Cosmic Egg exploding at the moment of the creation.
In 1933, Fr. Lemaitre and Einstein traveled together to California for a series of seminars. After the Belgian detailed his theory, Einstein stood up, applauded, and is supposed to have said, This is the most beautiful and satisfactory explanation of creation to which I have ever listened.
But Lemaitre’s work was to have an even more profound impact on cosmology. He showed that for L slightly greater than the critical value Lc, the universe erupts from R = 0 at t = 0 but then slows down for a long time near R = 1/sqrt(Lc) before once again expanding at an accelerating rate. The period of slow expansion is now thought to be necessary for the creation of stars and planets.
Fr. Lemaitre died on June 20, 1966 shortly after having learned of the discovery of cosmic microwave background radiation, a remnant of the Big Bang and proof of his intuitions about the birth of the Universe.
In 1998, astronomers in Berkeley, California, made a startling discovery. They were observing supernovae — exploding stars visible over great distances — to see how fast the universe is expanding, expecting to find the rate to be decreasing. Instead they found it to be increasing — a discovery which has since “shaken astronomy to its core” (Astronomy, October 1999).
This discovery would have come as no surprise to Georges Lemaitre who described the beginning of the universe as a burst of fireworks, comparing galaxies to the burning embers spreading out in a growing sphere. He believed this burst of fireworks was the beginning of time, taking place on “a day without yesterday.” He argued that the Big Bang was a unique event and he predicted that the expansion would eventually begin to accelerate, just as the Berkeley astronomers had found.
Lemaitre was a “priest of the cosmos,” a first rate cosmologist and mathematician and a first rate Catholic priest. His story is told in book form for the first time in The Day Without Yesterday: Lemaitre, Einstein and the Birth of Modern Cosmology by John Farrell.
posted by Bill Lama at
8:14 PM
4 Comments:
Bill,
I just knocked this out for your reading pleasure.
Sap
THERE is hardly a simpler law in physics than that according to which light is propagated in empty space. Every child at school knows, or believes he knows, that this propagation takes place in straight lines with a velocity c = 300,000 km./sec. At all events we know with great exactness that this velocity is the same for all colours, because if this were not the case, the minimum of emission would not be observed simultaneously for different colours during the eclipse of a fixed star by its dark neighbour. By means of similar considerations based on observations of double stars, the Dutch astronomer De Sitter was also able to show that the velocity of propagation of light cannot depend on the velocity of motion of the body emitting the light. The assumption that this velocity of propagation is dependent on the direction “in space” is in itself improbable. 1
In short, let us assume that the simple law of the constancy of the velocity of light c (in vacuum) is justifiably believed by the child at school. Who would imagine that this simple law has plunged the conscientiously thoughtful physicist into the greatest intellectual difficulties? Let us consider how these difficulties arise. 2
Of course we must refer the process of the propagation of light (and indeed every other process) to a rigid reference-body (co-ordinate system). As such a system let us again choose our embankment. We shall imagine the air above it to have been removed. If a ray of light be sent along the embankment, we see from the above that the tip of the ray will be transmitted with the velocity c relative to the embankment. Now let us suppose that our railway carriage is again travelling along the railway lines with the velocity v, and that its direction is the same as that of the ray of light, but its velocity of course much less. Let us inquire about the velocity of propagation of the ray of light relative to the carriage. It is obvious that we can here apply the consideration of the previous section, since the ray of light plays the part of the man walking along relatively to the carriage. The velocity W of the man relative to the embankment is here replaced by the velocity of light relative to the embankment. w is the required velocity of light with respect to the carriage, and we have w = c - v.
The velocity of propagation of a ray of light relative to the carriage thus comes out smaller than c. 3
But this result comes into conflict with the principle of relativity set forth in Section V. For, like every other general law of nature, the law of the transmission of light in vacuo must, according to the principle of relativity, be the same for the railway carriage as reference-body as when the rails are the body of reference. But, from our above consideration, this would appear to be impossible. If every ray of light is propagated relative to the embankment with the velocity c, then for this reason it would appear that another law of propagation of light must necessarily hold with respect to the carriage—a result contradictory to the principle of relativity. 4
In view of this dilemma there appears to be nothing else for it than to abandon either the principle of relativity or the simple law of the propagation of light in vacuo. Those of you who have carefully followed the preceding discussion are almost sure to expect that we should retain the principle of relativity, which appeals so convincingly to the intellect because it is so natural and simple. The law of the propagation of light in vacuo would then have to be replaced by a more complicated law conformable to the principle of relativity. The development of theoretical physics shows, however, that we cannot pursue this course. The epoch-making theoretical investigations of H. A. Lorentz on the electrodynamical and optical phenomena connected with moving bodies show that experience in this domain leads conclusively to a theory of electromagnetic phenomena, of which the law of the constancy of the velocity of light in vacuo is a necessary consequence. Prominent theoretical physicists were therefore more inclined to reject the principle of relativity, in spite of the fact that no empirical data had been found which were contradictory to this principle. 5
At this juncture the theory of relativity entered the arena. As a result of an analysis of the physical conceptions of time and space, it became evident that in reality there is not the least incompatibility between the principle of relativity and the law of propagation of light, and that by systematically holding fast to both these laws a logically rigid theory could be arrived at. This theory has been called the special theory of relativity to distinguish it from the extended theory, with which we shall deal later. In the following pages we shall present the fundamental ideas of the special theory of relativity.
Bill,
You must take into consideration,
that just as important as the quarks and leptons - the building blocks of matter are the forces that act between the particles and mould them into the forms of matter we observe. There appear to be four basic forces at work in matter - gravity, the electromagnetic force, the weak force and the strong force.
Gravity is the weakest of the four, but acts over great distances, binding stars and galaxies together. The electromagnetic force is stronger and is responsible for holding atoms and molecules together. As with gravity, its range is infinite. The weak force and strong force are by contrast limited in range, and operate only within the dimensions typical of an atomic nucleus. The weak force causes certain forms of radioactivity and underlies the nuclear reactions that fuel the Sun. Last but not least, the strong force - the strongest we know of - binds quarks and antiquarks together within the particles we observe. The strong force seems to act in such a way that quarks are always locked inside these more complex particles, so that we have never observed a single free quark.
Wow! I did not know that... thanks! I love the phrase, "The Day Without Yesterday."
-Mary G.
I love leptons! Liberals just make me GAG!
Rose
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