4. Let there be light

Centre of the Milky Way (image - ESO)The account focuses on the Earth before anything else. Having been created, the Earth was initially without form (not yet differentiated into land, seas and sky); void (empty of life); and dark. The heavens were also dark and without form.

Time began from the first moment of creation, but it could not be measured until there was light. Light was spoken into existence on the first day and divided the first day, a cycle of dusk and dawn as the Earth revolved before the light. ‘God spoke and it came to be.’ The energising of the heavens, the imposing of form and the impartation of life took place over the first six days of measured time. He made the firmament (the space occupied by the solar system, bounded by an envelope of water), the sun, moon and planets, the concentrations of ultraluminous matter that would later spawn galaxies, and living creatures to inhabit the Earth.

In the Middle Ages, the general opinion was that the Earth stood at the centre of the solar system, with the sun revolving around it. Further out, the fixed stars and the wandering stars – what we would now call planets – also revolved around the Earth. To scientists and churchmen alike the Bible appeared to support this view. Ecclesiastes, for example, stated, ‘The sun rises and the sun goes down, and hurries to the place where it rises.’ However, Copernicus showed that it was mathematically simpler to conceive the sun as at the centre of the universe, and Galileo strengthened the case with optical evidence from the newly invented telescope. He could see that the solar system was not some quasi-mechanical system of crystalline spheres beyond the realm of mutability. Moons revolved round Jupiter just as the Moon revolved round the Earth, the mountains of the Moon cast shadows, and Venus as it orbited the sun went through phases just as the Moon did. Although the Galileo affair is often portrayed as a clash between biblical religion and free-thinking science, historically the clash was between defenders of the then scientific paradigm (an Aristotelian/ Ptolemaic world-view, with the Bible interpreted so as to concur with it) and others who, venturing outside the paradigm, had found scientific reason to question it. To men like Galileo it seemed clear that in contrasting the endless repetition of natural cycles to the brevity of human life, the writer of Ecclesiastes was illustrating how ‘all is vanity’, not making a scientific statement – any more than that the Earth was to be understood as literally ‘under the sun’. Ecclesiastes was using the idiomatic language of appearance.

Heliocentrism itself, moreover, did not turn out to be correct. We now know that the sun is situated 25,000 light years from the centre of a galaxy of billions of suns, so it no longer makes sense to say that the sun is at the centre of the universe. This is not to imply that conceiving of the Earth as a fixed point and the rest of the galaxy as moving relative to it is impossible. All motion is relative to a frame of reference, and in theory one could make the frame of reference a stationary Earth. However, any mathematical description that claimed that this corresponded to reality would violate the test of parsimony (‘Occam’s razor’), which prefers, other things being equal, the simplest explanation. Copernicus’s work prevailed over the Ptolemaic model because it was simpler. More than that, it was closer to the truth.

In modern usage the ‘Copernican Principle’ refers to something rather different: a philosophical assumption that not even the Milky Way occupies a privileged or central place in the universe. Such a view may not be closer to the truth. As Stephen Hawking conceded in A Brief History of Time,

We have no scientific evidence for, or against, this assumption. We believe it only on grounds of modesty: it would be most remarkable if the universe looked the same around us in every direction [which it does], but not around other points in the universe!

Indeed, whether because of this assumption or because (according to some) space-time is curved and stops you from looking in a straight line, it is thought there is no centre anywhere, just as if the world were infinite. The increase in the wavelength of light proportional with distance (known as redshift) is interpreted to be the effect of galaxies receding from each other, like points on the surface of an inflating balloon, and this scattering movement, in turn, is interpreted to be due to space itself expanding. In contrast to the Doppler effect, where wavelengths are not themselves stretched, cosmological redshift occurs because wavelengths are stretched by the expansion of space between bodies that are themselves stationary in space. (But would there not be a Doppler effect, if the objects are indeed receding from each other?)
From a purist point of view one cannot help but deplore the expression ‘big bang’, loaded with inappropriate connotations …, which conjures up a false picture of a bounded universe expanding from a center in space. In modern cosmology, the universe does not expand in space, but consists of expanding space.

E. Harrison, Astrophysical Journal 403:28-31 (1993)

It is the redshift-inferred expansion of space that is extrapolated backwards to a primordial ‘Big Bang’.

If you find such concepts difficult to comprehend, you are not alone. Nearly everyone finds the lack of a centre impossible to visualise, and a few might dare to suggest that the impossibility (which even cosmologists overcome only by analogy, e.g. an inflating balloon) is an indication that the concept of expanding space is misconceived. Distinguished astrophysicists such as Steven Weinberg and Martin Rees come close to saying just that:
Popular accounts, and even astronomers, talk about expanding space. But how is it possible for space, which is utterly empty, to expand? How can ‘nothing’ expand?
“Good question,” says Weinberg. “The answer is: space does not expand. Cosmologists sometimes talk about expanding space, but they should know better.” Rees agrees wholeheartedly. “Expanding space is a very unhelpful concept,” he says. “Think of the Universe in a Newtonian way – that is simply, in terms of galaxies exploding away from each other.”

New Scientist 17 April 1993.

Nonetheless, space is said to be expanding because galaxies are supposedly receding from each other rather than from a centre. A galaxy at twice the distance from us is moving away at twice the speed – quite unlike the pattern of real explosions, such as the explosion produced by a bomb or a volcano.

One does not have to assent to what, in the normal world, would be logical nonsense: an explosion where objects all flee from each other as if each one was a centre of explosion. Nor does one have to accept the other nonsense that offers itself as scientific understanding: such as the idea that all matter was initially concentrated in a sphere smaller than a pea, ‘infinitesimally small and infinitely dense’ in Hawking’s words; or the idea that the Big Bang had no cause; or the idea that entropy was then at a minimum; or the idea that in the first trillion-trillionth of a second after the Big Bang the pea expanded into an ocean of energy larger than the visible universe; or the idea that in the course of subsequent expansion the force of gravity overcame the expansion and caused matter to clump into galaxies. The Big Bang model is mystical mumbo-jumbo. It does not have the qualities of a normal scientific explanation.

In the creation account the Earth certainly is the focus. The universe consists of the heavens and the Earth, implying that these two categories represent the poles of reality. The Spirit of God broods over the earth. It is the centre of his attention and everything is done in relation to it. The sequence of creative acts climaxes and ends with the creation of man, and when everything is finished on Earth, the whole creation is said to be finished. One can understand why medieval Europe should have supposed the Earth to be at the centre.

But there is also another duality, between light and darkness. The earth being originally in darkness, it is possible to conclude that the true centre must have been whatever gave the Earth light. In medieval astronomy, this had to be the sun, since no other light source known came close to the sun in brightness. The function of the sun was to be a light-giver, so the centre was the obvious place for it, just as the centre was the most efficient place for a lamp in a room:
In the middle of everything is the sun. For in this most beautiful temple [the universe], who would place this lamp in another or better position than that from which it can light up the whole at the same time? For the sun is not inappropriately called by some the lantern of the universe, its mind by others, and its ruler by still others. [Hermes] the Thrice Greatest labels it a visible god, and Sophocles’ Electra, the all-seeing.

Nicholas Copernicus, De Revolutionibus Orbium Coelestium (1543)

The heart of the issue was what lay at the centre of the universe, not merely whether the Earth revolved around the sun. Eventually astronomers realised that Copernicus had been wrong. The fixed stars that supposedly also revolved round the sun were in fact suns in their own right. Although Copernicus believed in intelligent design, his inspiration was neo-Platonism rather than Scripture (hence his citation of Hermes Trismegistus) and he assumed that the Pope, to whom he dedicated his work, would assess the proposal from the same point of view. Genesis, by contrast, was anything but heliocentric. It stated that the sun was not formed until day 4, before which time there was another source of light. Citing Scripture could not have helped Copernicus’s cause. As yet, heliocentrism and geocentrism were the only options, and many scholars (believing that the ‘straightforward’ sense was to be preferred) understood Genesis to be positively geocentric. No one could have predicted, on the strength of Genesis’s incompatibility with heliocentrism and Copernicus’s disproof of geocentrism, that both would turn out to be wrong.

In Genesis the source of the light that initially marked off day and night was unnamed and unknown. It was not the sun. It was an extraordinary position to be taking for a document not younger than the first millennium BC, when people knew of only one major light source. Nonetheless, could it be tenable? Could it be that our much more profound understanding of the universe, where the sun nestles among billions of stars and there are billions of galaxies beyond that, enables us now to suggest the identity of that light source? The only light-generating objects in the universe apart from stars are quasars. Quasars are the massive ultra-luminous furnaces at the hubs of galaxies. So the most plausible identification seems to be that the source was a quasar, from which, as with other nascent galaxies, streams of gas subsequently shot forth like fire from a catherine wheel. Possibly the reason why the text left it unnamed is that, by the time it was written, the quasar had long since ceased to exist. As a result of an increase in inertial mass and a corresponding deceleration in the speed of light (discussed in section 8) it collapsed and became a black hole. Just how brightly the sphere might have shone may be gauged from the present mass of the black hole: the equivalent of 4.5 million suns.

Although a quasar no longer illuminates the Milky Way, invisibility is not the normal fate of a black hole. All massive galaxies have black holes, and paradoxically most still do radiate massive amounts of light, as the mass of the accretion discs around them gets sucked back in and converted into electromagnetic energy. Known as active galactic nuclei, they produce more light than the entire output of the stars that make up the rest of the galaxy. They are the oldest objects in the universe, visible as far back in time as telescopes can take us. By comparison with most black holes, the one at the centre of our own galaxy is tiny.