There is a force in the universe that never dies out; a force that reaches the furthest corners of the infinite cosmos; it’s a force that, once it has captured you, can crush you into annihilation; or it can project you to the most ethereal places. It’s an inescapable force that has sway on everything you do, anywhere you are.
This force is love. The same kind of love that unites our two beautiful Bride- and Groom-to-be tonight.
There is a similarly all-pervasive force that explains the motions of the heavenly bodies: that force is gravity. Isaac Newton was the first to realise that it is the same gravitational force that makes the apple fall from the fabled tree that also keeps the Moon on its orbit around the Earth. Later, Albert Einstein would explain gravity as geometry, as the shape of space time itself.
Both men would probably not have made such ground-breaking discoveries had it not been for the leap of genius of the person who changed forever the way we see our place in the cosmos: Nicolaus Copernicus (or Mikolaj Kopernik, in Polish).
Copernicus was born in 1473 in what is now the city of Torun. After the death of his father, Copernicus, aged 10, was taken in by his maternal uncle, the Prince-Bishop of Warmia, and was educated in astronomy, mathematics, geometry and philosophy at the University of Krakow. He then completed his studies in Italy, where he studied astronomy, canon law, philosophy and medicine, before returning to Warmia, aged 30, in 1503.
At that time, the accepted model of the working of the heavens was the Ptolemaic system: formulated some 17 centuries previously by Claudius Ptolomeaus, it held the Earth at the centre of the cosmos. All other heavenly bodies revolved around the Earth. We now consider this “geocentric model” hopelessly naive, but to do that is to forget the fundamental fact that it was actually in accordance with experience. To the ancient Greeks, it was a self-evident truth that the Earth could not possibly be moving, for if the Earth were to revolve on its axis (as it actually does), they reasoned that the speed at the equator would have to be around 1000 miles an hour. If this was so, how comes we do not get thrown about wildly by this exceedingly fast motion? (The answer is, of course, that the atmosphere also rotates together with the Earth!).
The Ptolemaic model was actually quite sophisticated: it needed to explain not only the regular East-West motion of the so-called “fixed stars”, but also many other quite refined astronomical observations, including the puzzling “retrograde motion” of some of the planets, which appear to reverse their direction of travel on the sky at certain points in time.
The geocentric Ptolemaic model explained all of that with a complex system of moving spheres: each planet is moved around a sphere (the epicycle), which itself moves around a fixed point (the deferent). Complex as it was, it worked beautifully for centuries, could predict the position of stars and planets throughout the year, and was in accordance with the literary interpretation of the Scriptures taken by the Catholic Church, for which, according to Psalm 104: “The Lord my God laid the foundations of the earth that it should not be moved forever.”
It is against this backdrop that Copernicus’ work has to be seen: not only as revolutionary (which it was), but as outright visionary. It is not known what influenced him to formulate his heliocentric model, around 1514. The notion that the Sun was at the centre of what we now call “the Solar System”, and that the Earth revolves around it while spinning on its axis, had been proposed before by Aristarchus of Samos in the third century BC. But there is no evidence to suggest that Copernicus was aware of Aristarchus’ work. Indeed, Copernicus independently rediscovered the heliocentric model, probably guided by the beautiful simplicity that it offered. We have to remember that Copernicus did not have access to sophisticated astronomical observations: the telescope would only be invented at the beginning of the 17th century. So necessarily his revolutionary thinking had to come out mostly of “pure thought”.
It is difficult for us to imagine the jolt of almost ecstatic pleasure that Copernicus must have felt when he realised that the heliocentric model, in one simple stroke, could explain all the observations on the complicated motions of the heaven. Place the Sun at the centre, and the planets (including the Earth) going around it in perfect circles — something we now know is not exactly true — in order of distance (Mercury, Venus, Earth, Mars, Jupiter and Saturn) and everything could be explained. No need for complicated epicycles: just the masterful dethroning of the Earth from its assumed special place in the cosmos, and everything would fall in line. Copernicus wrote: “In the center of all rests the sun, for who would place this lamp of a very beautiful temple in a better position than this wherefrom it can illuminate everything at the same time? In this ordering we find that the universe has a wonderful common measure [the size of the earth’s orbit] and a sure bond of harmony for the motion and size of the orbital circles such as cannot be found in any other way.” The far-reaching consequences of this bold idea are still ringing to this day.
Copernicus hesitated to present his model to the public, for he feared the backlash that his incomprehensible ideas would surely have generated. According to legend, the first printed copy of the book in which he explained his model “De Revolutionibus orbium coelestium” (On the Revolutions of the Celestial Spheres) was presented to him on his deathbed. He awoke from the coma in which he had fallen, saw the book containing his life’s legacy and died peacefully and content, on May 24th 1543, aged 70.
In his 1959 book “The Sleepwalkers”, the novelist Arthur Koestler called De Revolutionibus “the book nobody read”, for it didn’t appear to generate much interest, nor controversy. The opposite is in fact true: we now know that De Revolutionibus had been read and studied by Kepler (who owned a second-hand copy). A friend of Kepler brought on a trip to Italy two copies, destined to whomever might appreciate them, which ended up in the hands of none other than Galileo. The reason why De Revolutionibus escaped the Church’ censorship can be traced back to an un-authorized preface added by Andrea Osiander, the book’s proofreader, urging readers not to take the Copernican model as an actual description of reality, but merely as a convenient trick to compute orbits and positions of the planets in the sky.
Osiander’s move, controversial as it was even at the time, proved prescient. When in 1632 Galileo published his own Dialogue on the Two Great World Systems, the controversy with the Church erupted fiercely. Copernicus’ book was placed on the list of banned books in 1664, where it would remain until 1835.
We can today look back at Copernicus as one of the founding fathers of the scientific revolution. There is a clear line connecting his work to Kepler, Galileo and from there, Newton. Rather like his book, for a long time Copernicus’ mortal spoils remained somewhat unrecognised. It was only a few years ago that his remains were identified in an archaeological excavation under Frombork Cathedral. Extraordinarily, a fragment of DNA extracted from a cranium matched the DNA found on 2 hairs collected from the gutters of a book that had been owned by Copernicus.
If modern forensic science and biochemistry were able to give Copernicus’ mortal remains proper recognition, it is in modern cosmology that Copernicus’ spirit lives on. Indeed, his ideas are at the centre of ongoing, cutting-edge research on what exactly is our place in the universe — or rather, in the Multiverse.
Copernicus is forever associated with the principle that today bears his name. In cosmology, the Copernican Principle states that we, as observers on the Earth, are in no special or privileged position in the Universe. This means that, statistically, all the observations that we make about the cosmos must be equivalent to those that would be made by alien astronomers on another Galaxy. True, the detailed view of the sky as seen from another galaxy would be different, but the large-scale, global properties of the cosmos that imaginary observers on other planets would deduce must be the same as our own. This Copernican principle is so fundamental that it is engrained in almost all analyses of the wealth of data that we have today at our disposal from telescopes and satellites. Whenever it has been tested, it has been found to hold true.
In other words, the Copernican Principle has fully dethroned Earth from being a special place in the Universe. However, the more speculative edges of theoretical physics have recently been putting the Copernican Principle in doubt. Their main argument goes under the name of the “Anthropic Principle” — the notion that the physical conditions that lead to the presence of sentient observers (such as ourselves) are, in some sense, special. Indeed we (or any life-form based on similar chemistry and physics as us) would not be able to exist were it not for the concurrent happening of a set of quite special circumstances: we need a stable, rocky planet located in the habitable zone of a long-lived star; for this to happen, we need heavy elements (like Oxygen and Carbon, which are not produced in the Big Bang) to have been manufactured in explosions of previous generations of stars; therefore, we must live in a relatively old Universe (our current estimates of the age of the universe put it at 13.798 billion years, give or take 21 million years); since the Universe is expanding and cooling off as it does so, the cosmos around us must be large, and cold. The Anthropic Principle thus states that we do occupy a special niche in time, space and even in the collection of the multitude of possible physical realities predicted by string theory. Because if we did not inhabit such a special corner of the Multiverse — one that allows for the presence of observers such as ourselves, a “Goldilocks universe” that is just right for us — then we wouldn’t be able to exist, and the question could not even be posed. Special or not special, this is the problem!
Copernicus would no doubt have been delighted by this debate at the frontiers of physics. He would have rejoiced at the prospect that perhaps our physical reality is but one of many possible alternative universes.
He of course only had a single example of a solar system to work from: ours. In Copernicus’ time, only 5 planets were known: Mercury, Venus, Mars, Jupiter and Saturn. William Herschel would discover Uranus in 1781, while Neptune would be discovered only in 1846, and Pluto in 1930. It wasn’t until 1995 that a planet orbiting another star but the Sun would be discovered. Today, new technologies and sophisticated observatories enable us to find solar systems orbiting around other stars relatively easily, something that Copernicus would have probably considered unimaginable. There are today 3,823 confirmed planets in 2,860 systems. And that’s only the beginning: estimates suggest that across our galaxy there might be 150 billion planetary systems, and a staggering 7500 billion systems in the whole Universe. And each one of them works exactly in the way Copernicus said.
Next time you find yourself under dark, clear skies, look up and find the constellation of Cancer (next door to Gemini, which can be recognised thanks to the bright Castor and Pollux). If you are lucky (or even better, with a good pair of binoculars), you might be able to spot a faint star: 55 Cancri A, which, since 2015, the International Astronomical Union renamed “Copernicus”. 55 Cancri A is a sun-like star, approximately 41 light years away. The star is in a tight orbit with a binary companion, a smaller red dwarf, and hosts its own planetary system, made of 5 planets, which of course orbit around it. One of them is thought to be a super-Earth within the habitable zone. Copernicus keeps good company up there: of the 5 planets orbiting it, three are named after illustrious astronomers (Galileo, Tycho Brahe, Thomas Harriot) and two after telescope makers (Lipperhey and Jannsen). A very fitting tribute for the man who changed forever our place in the cosmos.
Owen Gingerich, Copernicus: A Very Short Introduction, Oxford University Press (2016).