It is common knowledge that Einstein (according to George Gamow) called his 1917 addition of a “cosmological term” to his gravitational field equations his “biggest blunder.” He had done that to make possible a static universe, but within a few years it was found that the universe isn’t static but expanding, and he then abandoned the cosmological term. If Einstein hadn’t altered his equations he might have been able to predict this expansion.
Einstein’s added “cosmological term” has the effect of a repulsive aspect of gravitation. His original idea was that this could balance ordinary attractive gravitation so that matter could remain at rest. Without the cosmological term we would expect an expanding universe to be continually slowed by gravity, though the expansion might never stop.
The finding in the 1990s that cosmic expansion is not slowing but in fact speeding up, a discovery that has just earned Perlmutter, Schmidt and Riess the Nobel Prize in Physics, requires reconsideration of Einstein’s “blunder.” Several theoretical suggestions have been made for the “dark energy” that causes this acceleration but the simplest, Einstein’s cosmological term, explains the data satisfactorily. Is this serendipity, just dumb luck, or something deeper? In spite of considerable discussions, there are some aspects of this question that have not gotten adequate attention.
Why did Einstein think that the universe was static? In the early 20th century that was the common belief. (While traditional Jews and Christians thought that the universe had been created at a finite time in the past, God was thought to have brought it into being in pretty much its present form.) It seems, however, that Einstein was not just succumbing to popular prejudice. Max Jammer, in his helpful book Einstein and Religion, pointed out that Einstein’s commitment to the pantheism of Spinoza may have been significant here. For Spinoza, “God” and “nature” were simply two ways of speaking about the same thing – Deus sive natura. And if, as Spinoza believed, God is immutable, so is the natural world.
So it’s possible that Einstein’s belief in a static universe was an expression of his religious faith. Perhaps his blunder was, at bottom, religious.
That possibility is strengthened by the fact that it’s difficult to maintain that it was a scientific blunder at all. Observational data in 1917 gave no reason to think that the universe was expanding. Astronomers at the time were still debating the status of what we know today to be galaxies outside the Milky Way. And as far as theory is concerned, the cosmological term is in accord with the basic ideas of general relativity and satisfies the criteria Einstein originally used to establish his gravitational equations. If he hadn’t introduced it when he did, some other theorist would soon have suggested it simply as a logical possibility.
After Hubble’s announcement of the general recession of galaxies many workers in relativity abandoned the cosmological term, in spite of the fact that there was no evidence against it. There was pretty wide scope for a non-vanishing value of this term because uncertainties in the speed of cosmic expansion and its rate of change were large. Some physicists seem to have rejected it in deference to Einstein’s authority. But there were always some – Eddington and his students were notable – who refused to go along.
More importantly, some attempts to go beyond general relativity required a non-vanishing cosmological term. The affine theory developed by Schrödinger in the 1940s (described in the last chapter of his Space-Time Structure) is the best example. A change in the rate of cosmic expansion in addition to that produced by ordinary gravitation is thus a natural part of this theory, although we cannot say a priori whether the cosmological constant would be positive or negative. This contrasts with other models of dark energy that have been developed only to explain the observational results.
What lessons can we draw from this? Some might say “Don’t be a Spinozan pantheist,” and it’s true that biblical faith has to reject an equation of God with the universe. (Spinoza was placed under the ban by the Amsterdam synagogue.) But in the present case the problem is not just that but the idea that God is immutable, utterly unchanging, a view that much of traditional Christianity has also accepted.
Perhaps more to the point would be a warning to be careful about the way we try to correlate scientific cosmology with our theology. Some Christians have seized upon big bang cosmology as a proof that there was a beginning of time, the essential truth of Genesis 1, and/or the doctrine of creatio ex nihilo. It is now quite certain – as the intro to a popular sitcom reminds us each week – that about 14 billion years ago the whole universe that we can observe was in a hot, dense state and then expanded to its present condition. But this does not prove that time had a beginning or that there was a singularity (somewhat misleadingly designated t = 0) that we can’t get beyond.
There are presently viable cosmological models, such as the one developed by Paul Steinhardt and Neil Turok and described in their 2007 book Endless Universe, which go back before the big bang. Christians should have learned from their long attachment to Aristotelian physics not to tie their theologies too closely to any cosmological model. Today they need to think about how to formulate their doctrines of creation to take into account the possibility that the big bang isn’t the last word.
And scientists need to be willing to reconsider old theories if earlier objections to them turn out to be unfounded. Theories like Schrödinger’s that were dismissed because they required a cosmological term deserve a second look.
Those familiar with current cosmology will note that I have said nothing here about quantum vacuum energy which apparently yields an effective cosmological term that is far too large. I have some ideas about how to deal with that but this is not the place to present them.