Lemaitre Sheds Light and Creates Conflict

Georges Lemaitre was born in 1894.  He began studying engineering but, like Friedmann, his studies were interrupted by World War I.  In the trenches he observed first-hand the effects of German mustard gas and won the Croix de Guerre.  After the war he returned to his studies but switched to theoretical physics.  He also enrolled in the seminary and was ordained a priest in 1923.  For the remainder of his life he pursued two careers, physics and the priesthood, saying “There were two ways of arriving at the truth.  I decided to follow them both.”

Georges Lemaître is credited with proposing th...

Georges Lemaître is credited with proposing the Big Bang theory of the origin of the universe in 1927. (Photo credit: Wikipedia)

In 1923 after spending two years in Cambridge with Arthur Eddington, Lemaitre returned to Belgium and began his own cosmological quest for truth.  He adopted Einstein’s general relativity but, like Friedmann, rejected the notion of the cosmological constant.  Without knowing anything about Friedmann’s work, Lemaitre resurrected the expanding universe model.  Unlike Friedmann who was a mathematician, interested mainly in the numbers of the theory, Lemaitre wanted to understand the reality behind the numbers.  If the cosmos were expanding, Lemaitre decided to run the clock backwards.  An expanding universe implied that things were closer together yesterday, closer still 100 years ago and still closer 1 million years ago.  Run the clock backward enough and the inescapable conclusion was that everything was together at one point.

Perhaps influenced by his theological training, Lemaitre realized that general relativity implied a moment of creation.  He concluded that the universe began in a relatively small, compact region that suddenly expanded and evolved into what we observe today.  He refined his theory into what he called the primeval atom that contained all of the matter that eventually became the stars and planets.  Though a moment of creation was central to his theory, Lemaitre was interested in the evolution of the universe from the primeval atom to the stars and galaxies.

Lemaitre published his theory and was met with the same deafening silence that greeted Friedmann.  To make matters worse, Lemaitre also had a run-in with Einstein who rebuffed him, saying that his mathematics were correct but his “physics is abominable.”  Einstein had thus been offered two chances to accept an alternative to the steady state view of the universe and rejected both.  As the world authority on cosmology, Einstein’s words had the force of law.  It is ironic that, having challenged authority in his early career Einstein had now become the authority behind whom virtually all scientists fell into line.  It probably didn’t help Lemaitre that he was a priest and his theory smacked of a Creator.  Though it had been nearly four centuries since Galileo was forced to confess, the wounds science felt from religion were still tender.

The truth is, both theories were appealing and both had flaws.  The flaw in the steady state theory was the cosmological constant, which, as we have seen, is nothing but a fudge factor to make the theory conform to the accepted view of how things are.  The flaw in the nascent big bang theory (it still had not been thus named) was that there was no evidence to support the theory of a sudden explosion, other than the logic behind an expanding universe.  For that matter, though, there was no evidence to support a steady state model other than the belief that this is how things are.  The theorists needed evidence to support their various theories so they turned to the experimental physicists, the astronomers.

Friedmann’s Models of the Universe

Alexander Friedmann was a brilliant mathematician who also had a penchant for science and technology.  After enduring both the First World War and the Russian revolution in 1917, Friedmann was eventually introduced to Einstein’s Theory of General Relativity.  It may have been a combination of his delayed exposure to the theory and Russia’s relative isolation from the rest of the world that allowed Friedmann to ignore Einstein’s (and most other physicists’) view of the universe as static and formulate an entirely new and radical approach.

While Einstein started with the assumption that the universe is static and introduced the cosmological constant to counter the effect of gravity, which, under his view, would eventually lead to the collapse of the universe, Friedmann ignored the cosmological constant and then looked at general relativity to see what kind of universe it predicted.  First of all, Friedmann’s model was one of a dynamic universe, one that had started with an initial expansion (the term Big Bang wouldn’t come along for some 30 years).  This initial expansion led to three possible results:

friedmann models

friedmann models (Photo credit: Wikipedia)

First, if the initial expansion wasn’t great enough, gravity would eventually pull the universe back in on itself.  Like a ball thrown upward, the universe would at first move quickly, then slow to a complete and brief (in cosmological terms) time, and then begin to contract ever faster.  Friedmann envisioned it then expanding again, endlessly like a bouncing ball.

Secondly, if the initial expansion was great enough, the universe would continue to expand infinitely.

The third view was a middle ground in which the initial expansion was enough so that the universe would continue to expand, though slower and slower, never quite stopping.  It is like the problem of the rabbit and the lettuce.  Each second a rabbit moves one-half of the remaining distance between himself and a piece of lettuce.  For example, the rabbit starts out four feet from the lettuce.  In the first second he moves two feet closer.  The second second he moves one foot closer.  The third second he moves six inches closer and so forth.  Does he ever reach the lettuce?  The answer is, no, he never covers the remaining half-distance to the lettuce.  Similarly Friedmann’s third model never quite reaches a point where gravity overcomes expansion, though the rate of expansion continually slows until, like the rabbit, the universe is creeping forward.

Friedmann thus proposed a model of the universe based on general relativity that did not match the model proposed by the creator of the Theory of General Relativity, Albert Einstein.  Although Einstein would admit that Friedmann’s view was mathematically correct based on general relativity, he claimed it was scientifically irrelevant because the universe was static.

Friedmann was eventually proven correct, but he did not live to see himself vindicated as Einstein had done with his theory.  Friedmann died of a serious illness, probably typhoid fever, in a delirium, reportedly lecturing to an imaginary audience.  Part of Friedmann’s problem was that his notion was too radical.  He suffered the same fate as Copernicus in that the scientific world simply wasn’t ready for his view of the universe.  Another problem was that he locked horns with Einstein himself, the world’s foremost cosmologist at the time.  Finally, Friedmann, a mathematician, was not an astronomer and was therefore an outsider to the cosmological world.  Though Friedmann’s papers were published during his lifetime they received almost no notice and would not until they were rediscovered by a Belgian scientist, Georges Lemaitre.

The Cosmological Consequences of General Relativity

In 1917 Einstein published a paper entitled Cosmological Considerations of the General Theory of Relativity. The title is significant.  Unlike Galileo, Copernicus, Kepler, Brahe and Newton, Einstein was concerned with the entire universe, not just the solar system.  Calculating the orbit of Mercury to predict its movement around the sun was hard enough, but Einstein had the audacity to attempt to predict the movement of stars and galaxies.  In order to do this he had to make an assumption.  His assumption, known as the cosmological principle, is that the universe is isotropic and homogeneous.  This means that the universe looks pretty much the same in every direction, and that it looks that way from whatever vantage point in the universe you have.  This means that we do not occupy a special place in the universe.

When he applied his theory to the universe, the result was unsettling to say the least.  General relativity predicted that the universe was destined to crash in on itself as a result of gravity’s relentless pull on the stars and galaxies.  Newton’s theory had predicted the same thing.  In the early 20th Century, the view of the universe was that it was stable, that it had always existed more or less as it is today.  But Einstein’s prediction was that things would start creeping slowly toward each other.  The creep would turn into a frantic dash as stars and galaxies collided.

Anxious to make general relativity consistent with the observed and accepted notion of what the universe is, Einstein realized that if he introduced a constant, which he called the cosmological constant into general relativity, he could keep the result from being a huge crunch at some point in the future.  The cosmological constant was a sort of anti-gravity that repelled matter, offsetting the natural attraction of gravity just enough to prevent collapse.  It was, in essence, a fudge factor similar to that found by proponents of Newton’s theory of gravity who were unwilling to accept general relativity.  Even Einstein was somewhat ashamed of the need for this fudge factor, saying that it was “detrimental to the formal beauty of the theory [general relativity].”

Most scientists were content to accept the cosmological constant as a “refinement” to general relativity because it made the theory fit with their notion of the universe.  Remember we began with the adage that things are what they are and if the theory doesn’t explain them we better get a new theory.  No one wanted to jettison general relativity after having just adopted it.

No one, that is, except Alexander Friedmann, a Russian scientist born in 1888.  Friedmann would tackle orthodoxy head on and come up with a radically different view of the universe, one that would not be confirmed for decades.