The Astronomer, the Physicist, and Worlds Colliding

There may be some earth-shattering collisions ahead, but we know from Faith that the Church will be left standing, battered and bruised, perhaps, but ready for her glorious resurrection and consummation at the end of time.

(Image: Greg Rakozy/

What have ancient Greek philosophy, a prophecy of Christ and COVID in common, and might this commonality be used to find common ground?

For people once on familiar speaking terms are now no longer, as battle lines are drawn, in what seems a fulfillment of Christ’s warning that He came to set a man against his father, and a daughter against her mother, and a daughter-in-law against her mother-in-law; and a man’s foes will be those of his own household. (Mt 10:35-36). Such has likely transpired within the halls of your own home, as opinions – we will call them so, for now – on everything from vaccines, to masking, to climate change, to every moral issue under the sun divide families. It may well be good to take a step back, breathe and ponder things from a more philosophical, even theological, stance. Might this offer some small patch of middle ground, where peace may be sought?


The ancient Greeks – Plato and Aristotle, especially – made a distinction between two approaches to science. (And, by science, they meant anything that could be known by reason): The method of the astronomer and that of the physicist.1 (Don’t be misled by these terms, for these ‘methods’ apply to any science, not just astronomy. It just happens that astronomy, sometimes called cosmology – the study of the heavens and the earth and their inter-relation – was the primary ‘science’ of the ancient world, right up to the modern era.)

Their primary impetus, besides human wonder, was to predict, and to some extent explain, the motion of the planets – whose Greek name means ‘wanderers’ – including the Sun and the Moon, as they traced their oft erratic orbits around the Earth. The astronomer, also called a ‘mathematician’, since much of that was involved – attempts to provide a ‘model’ of this motion, which should do two things: First, to trace out and predict their paths, which would help with such necessary things as timekeeping, setting the monthly and yearly calendars, and for navigation. Second, and more controversially, the model should also, as Plato puts it, ‘save the phenomena’, the ‘phenomena’ being what appeared to our senses, from our perspective here on Earth. By ‘save’, the model should also preserve the a priori assumptions which the astronomer holds as inviolably true.

These assumptions, or principles, may be derived from various sources: theology and religion; or from some other source of authority; or from what seems ‘obvious’ and ‘common sense’; or, to use modern jargon, what is held by consensus. The ancient Greeks held as true, even sacred, the following principles:

  1. That the Earth was immobile and at the center of the cosmos. This very much seemed to be the case, from the evidence of our senses (and it is still very difficult to prove the Earth moves while standing on the planet). Also, the center was the only fitting pace for the abode of the gods and men.
  2. That all the planets – including the Sun and Moon – moved around this stationary Earth on perfect circles and at a uniform, constant speed (which, again, is only fitting the perfection of the celestial orbs – how dare they move on imperfect ellipses or at erratic speed!)
  3. That all the stars and planets were made of ‘quintessence’ (‘fifth’ essence) which, unlike Empedocles’ terrestrial four elements of earth, air, fire and water, was unchanging, perfect and eternal.

These the Greeks were held to be physically true, in accord with how the cosmos must be in accordance with its nature (physis being the Greek words for ‘nature’). A scientific model was held to ‘work’ when it successfully ‘saved all the phenomena’ within the confines of these assumptions.

Here is Simplicius, a sixth century Neo-Platonist (+560), summing this up for us:

Plato lays down the principle that the heavenly bodies’ motion is circular, uniform and constantly regular. Thereupon he sets the mathematicians (that is, the astronomers) the following problem: What circular motions, uniform and perfectly regular, are to be admitted as hypotheses, so that it might be possible to save the appearances presented by the planets?


Yet, science cannot stop there, for to complement the model-building method of the astronomer, we must add the method of the physicist, whose task is to seek the actual nature of the cosmos, the ‘reality’ behind the model. The physicist’s task is also two-fold: To provide the a priori principles that guide the elaboration of our models, as for the Greeks and their perfect circles and stationary earth.

Yet the physicist also – or should also – gather evidence to test the model as time goes on, and experience builds up, through senses (whether or not assisted by technology, such as telescopes and microscopes and such). Are the assumed a priori principles actually true? Does the model hold up against the evidence? How far can we adapt a given model to ‘save the phenomena’ of our dearly held models, before it just breaks down, and must be declared, alas, false?


Aristotle, Plato’s erstwhile student and colleague, posited that the planets rotated around the Earth in concentric, crystalline spheres. The problem is, the planets don’t appear to move in perfect circles, nor at uniform, regular motion, from our vantage point. (That is, the phenomena escape the model, and must therefore be ‘saved’). Rather, they speed up, slow down, even move backwards – so Aristotle had to add more spheres, eventually up to 57 of them, to account for these phenomena, that is, to maintain the hypotheses of ‘circular, uniform and constantly regular’ motion.

A half-millennium later, the great astronomer Claudius Ptolemaeus, ‘Ptolemy’ (fl., 150 A.D.) wrote the most influential – not the most true, mind you – astronomical treatise of all antiquity, the Syntaxis or Almagest. By this time, more and more data – phenomena – from the planetary motions piled in, and the complexities of their motions (again, from what we could perceive) was horrendously complex. Ptolemy hence strove to ‘save’ the a priori principles – the centrality and immobility of the Earth, the uniform motion, the circular orbits – with ever-more complex mathematical tricks. He added eccentrics (center of orbits that were not at the actual center, to account for apparent changes in distance); epicycles (orbits on top of orbits, to account for changes in speed and retrograde motion); as well as equants (points around which the planets moved in uniform angular velocity, sacrificing uniform linear motion, to account for irregularities in the shapes of the orbits).

Ptolemy’s model was generally held still to be physically true – despite its cumbersome mathematical tricks. Others did not care much whether it was true or not, just so long as it ‘worked’, and could predict the heavenly motions (which it did, reasonably well).

Copernicus in 1543 published, on his deathbed, his famous heliocentric model, placing the Sun at the center of the cosmos, and the Earth whirling around it at great speed, while spinning on its axis. Galileo would champion Copernicus’ model, with great controversy.

The problem was that no one could test any of these models, to prove by physical evidence which of them was true (not even the mighty Galileo had such, which was in large part what got him in trouble). They could not go ‘outside’ the system to see the Earth and planets moving, or not, but had to trust their senses, which were limited, conflicting and open to interpretation. What happens when more than one model might ‘save the phenomena’? How does one tell whether one is more true – more in accord with nature – than another?

One way, still much ballyhooed in science, is the ‘razor’ attributed to the 14th-century Franciscan William of Ockham (but which, like many things, goes back to Plato): That the truest model is the simplest one. Natura amat simplicitatem, wrote Newton in his Principia, nature loves simplicity, and, he added with flourish, suffers not the pomp of superfluous causes. We will return to this in a moment.

Another, perhaps more convincing, sign of the truth of a model was the physical evidence that could be gathered, for or against it. For the astronomer should also seek to correct, adapt, even discard, the model, as new evidence from nature comes to light. How the planets really move, and where the Sun and the Earth really were, was a controversy, prompted by Galileo, that helped build the methodology of modern science. Modern physics may now tell us that our planet is spinning at about 1000 miles per hour (at the equator) and whizzing around the Sun at a mind-boggling 67,000 mph, but few of us could prove that from where we’re standing, for various, yes, physical reasons.

We now also know that the other a priori principles of the Greeks are all wrong, or at least not fully right. Copernicus and Galileo got closer to the truth by placing the Sun at the center, but, mesmerized by their master Pythagoras, who held all reality to be number and mathematics, they could not let go of perfectly circular orbits and uniform motion. (And, anyway, Einstein with his theory of relativity would claim that the ‘center’ of any system depends upon one’s frame of reference). Kepler got even closer to the physical truth with his elliptical orbits (although most planets move on almost perfectly circular, they are not quite so), and his three laws of planetary motion are still held dear by NASA. But even Kepler requires further refinement, for the planets all influence each other, and there are precessions, wobbles and weaves. Reality – physics – is infinitely complex.

That is why, as Pope Saint John Paul II was to state quite rightly in his 1996 commentary on the Galileo affair, that this complexity of our cosmos “indicates precisely that, in order to account for the rich variety of reality, we must have recourse to a number of different models.”

In other words, no univocal model can possibly account for all the phenomena, and we will always need multiple models to account for reality. The more we peer into God’s creation, as our microscopes see ever-smaller, our telescopes ever-farther, with ever-new phenomena, the more we will have to refine, reform and even at times reject our models, along with the a priori principles on which they are predicated and built, even if we hold them very dear indeed.


To apply this to a sort of current example, in light of Our Lady of Fatima and her ‘Miracle of the Sun’. When those thousands of spectators, huddled in the rain on October 13, 1917, saw the Sun dancing, careening, spinning in the sky, beaming out multi-colored rays of light, hurtling towards the Earth and back, some screamed, others prayed, while still others ran for the caves. They all interpreted these phenomena – the method of the physicist – according to their a priori principles. For some, it was definitely a miracle of divine origin; for others, an atmospheric disturbance; still others, mass psychosis; and I just heard a short documentary that claimed it was aliens warning us.

We could apply this to any phenomena we like: Was Adam a Cro-Magnon man? When did he live? What cause global warming (if the Earth’s really be warming, still hypothetical)? Do masks and lockdowns reduce the risk of infection? Are they proportionate? How dangerous is COVID? Do the ‘vaccines’ work, and how so? Are there side effects? What is herd immunity, and should it be sought? What would happen if we lifted the restrictions?


We may extend this distinction beyond astronomy, or even science itself, all the way to our very modus vivendi itself – our way of living, our morals, based not just on our perspectives on not just on this life, but our belief (or disbelief) in eternity.

When such a model encompasses our basic worldview, we might call in a religion, or one’s ‘system of values’, our metaphysical model. Islam has quite a different view of God and heaven than does Catholicism, and they both differ from the atheistic views of Hume, Huxley and Dawkins. Is sex binary, and did God create us ‘male and female’? Do humans have eternal souls? Do things go dark after death, as though we had never been born, or will we meet our Saviour and Creator? Is there an objective moral order, a natural law? Will we be judged on how we have lived in this life, the decisions we have made? For much depends on the answer we give to such questions, and a plethora of others, pondering which is much of what makes us human.


What has this to do with keeping peace and harmony, if at all possible? (I will provide a final note on that). For now, here are some conclusions and applications of what may seem an abstruse distinction between the ancient, and the new, astronomer and the physicist:

  1. The only ‘model’ we Catholics hold as inviolably and irrevocably true is that of our Faith, whose revealed truths we hold and profess by divine authority. Christ did indeed rise body and soul from the dead, and Our Lady was assumed the same into heaven. Hence, they will never find the ‘bones’ of either of them. The Eucharist is the true ‘substance’ of Christ. God is in His heaven, and we all have angels guardian. We will not prove these by phenomena (barring the exceptional miracle), but we hold them nonetheless, because God revealed them through His infallible Church.
  2. About all our other models, scientific and otherwise, we should have some level of healthy doubt, even if a smidgen, and should not be too wedded to our scientific and hypothetical models, but be open to new evidence and phenomena as they arrive (but not so open that everything falls out, as Chesterton warned). That gravity exists is beyond doubt, but why and how it does so depends on one’s model of cosmology (the current Einsteinian four-dimensional curved-space theory being the current predominant one, and likely physically true).
  3. A helpful distinction here is between what Cardinal Newman called certainty – the objective truth of our arguments, our models, our worldviews – and certitude, the degree of confidence with which we hold them. We should keep these firmly distinct – believing something to be true does not make it so, and the same holds for what we might hold to be false. Evidentiary truth eventually wins the day. David Hume died a stubbornly professed atheist, but he was no longer one when he crossed that veil, and beheld the Son of God, whose existence he had denied.
  4. We must avoid vague generalities and sentimentality, whether in science or morals – precision and clarity are essential in whatever ‘models’ we hold, and what they imply. What does ‘evolution’ really mean? Darwin did not know of genes, DNA, alleles and such, and to get down to the molecular basis of the diversity of species is a complicated and controversial business. ‘The devil is in the details’, but more properly, the truth is often found therein.
  5. We should be free to pick or choose only some aspects or principles of any given model. Galileo could have adopted Copernicus’ heliocentrism, without his perfect circles (but, remember, he was hypnotized by Pythagorean mathematical perfection). We also may accept aspects of Darwinian evolution – species adapting to their environments – without the entire enchilada of his agnostic, blind-nature-working-by-random-chance. Someone may be in favour of some societal restrictions, but not all of them.
  6. Beware of models that extend beyond phenomena we can now perceive, and predict into the future – for if present phenomena are complex enough, the future phenomena are exponentially more so. This is what many scientists often mean by computer ‘modeling’, and many of the claims made on such – from population to resources to climate change – have already fallen far more into the realm of fiction than science. Neil Ferguson’s doomsday numbers are off by orders of magnitude, evincing either incompetence or insidiousness (but that’s just my model). Yet, he’s still held to be some sort of authority, alas.
  7. And, to return to John Paul II on a final and perhaps most important note, we need many models to account for the rich complexity of reality. If the cosmos cannot be reduced to one, bland ‘univocal’ model, far less can the great mystery of Man made in God’s very image!

If possible, as our various models jostle for space, we might be considerate of others’ points of view. As the saying has it, in necesariis unitas, in dubiis libertas, in omnibus caritas – Unity in necessary things, freedom in doubtful things, and in all things, charity. So we might make true the prayer of the Psalmist: May peace reign in your walls, and in your palaces, peace.

Yet, as the prophet Jeremiah warns, They have healed the wound of my people lightly, saying,`Peace, peace,’ when there is no peace. Certain models and worldviews – Roman paganism, atheistic communism, Hitlerian fascist-socialism, radical Islam – are all incompatible with the ‘worldview’ of Catholicism, and now we have the coalition of critical-race theory, ecological extremism and uber-COVIDian zealotry. Where is this all headed, one wonders? There may be some earth-shattering collisions ahead, but we know from Faith that the Church will be left standing, battered and bruised, perhaps, but ready for her glorious resurrection and consummation at the end of time.

I have come not to bring peace, but a sword and to cast fire upon the earth, and would that it were already kindled.

Such, however, is a purifying fire, consuming the dross of falsity, and leaving the golden core of truth. And only in that truth will we ever have lasting, indeed eternal, peace and freedom.

You can take that as physically true, on divine authority.


1 We will outline this distinction using the thought of Pierre Duhem (1861-1916), who was both an eminent physicist, as well as one of the foremost philosophers and historians of science; and he is in turn dependent on the reminds us of the ancient distinction, as detailed in Simplicius (490-560 AD), one of the last of the neo-Platonists, and a commentator on Plato, from whose commentaries on Plato we take the following.

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About John Paul Meenan 8 Articles
John Paul Meenan, M.Sc., M.A., teaches theology and science at Our Lady Seat of Wisdom in Ontario, Canada, with a particular interest in the relationship between faith and reason, and how the principles of our faith should impact and shape the human person and modern culture.


  1. The Ptolemaic model, as later elaborated, was accurate 99 percent of the time. But, now, three supporting quotes to illustrate Meenan’s thesis:

    From THOMAS AQUINAS, in the 13th century:
    “Reasoning is employed not as furnishing sufficient proof of a principle but as showing how the remaining effects are in harmony with an already posited principle; as in astronomy the theory of eccentrics and epicycles [the Ptolemaic universe with the sun and planets rotating around a stationary earth] is considered as established because thereby the sensible appearances of the heavenly movements can be explained; NOT however as if this proof were sufficient, since some other theory [Galileo’s later telescope disclosing the sun at the center] might explain them” (Summa Theologica, I, 32, I, ad 2; cited in L.M. Regis, Epistemology, 1959, p. 455).

    In the late 15th century, LEONARDO DA VINCI wrote in his notebooks that “the sun does not move.”

    For his part, in the 17th century CARDINAL BELLARMINE (who had dealings with Galileo) actually wrote:
    “I say that if it were really demonstrated that the sun is at the center of the world and the Earth is in the third heaven, and that it is not the sun which revolves round the Earth, but the Earth round the sun, then it would be necessary to proceed with great circumspection in the explanation of Scriptural texts which seem contrary to this assertion and to say that we do not understand them, rather than to say that what is demonstrated is false” (cited by Cardinal Poupard, in Origins [22:22], 1992).

  2. There are a series of articles online that covers the Galileo controversy in some detail. The series is titled “The Great Ptolemaic Smackdown.” The URL for the table of contents is:
    These articles are very lively, and spirited. They make many of the same points that this article does.
    According to the articles, at the time of Galileo astronomy was a branch of mathematics, and that “the real Scientific Revolution in astronomy was to move astronomy from a branch of mathematics to a branch of physics.”
    At the time of Galileo there were a number of astronomers who were also Churchmen. Clavius for one. During the dispute both sides had played the scripture card, which led to the involvement of the Church. The articles said that there were seven competing models of the solar system at the time of Galileo. The articles said that some of the Pope’s arguments had merit. The articles bring up the Duhem-Quine Thesis and Popper when discussing competing models and the data used to support the models. It is my understanding that it took Kepler several years to do the manual calculations to resolve the orbit of the planet Mars, which, of course, proved to be elliptical.
    The physics of Galileo’s time couldn’t handle a heliocentric solar system. Newton and the physics that he developed that could explain the heliocentric model did not yet exist at the time of Galileo. Newton was born in the year that Galileo died. We moderns don’t realize how little real modern science existed at the time of Galileo.

  3. Many thanks John Paul Meenan: quality stuff indeed; very welcome.

    Increasingly the sciences are providing the lingua franca of humanity and articles like this help the ordinary Catholic begin to get a grip on that. Every follower of Jesus Christ has a duty to communicate His saving message and, today, that also often requires scientific literacy.

    We need to be careful though that science does not (scientistically) claim credit for what it has not achieved. There are 7 major questions that, despite the labors of many thousands of the smartest brains, equipped with instruments of truly amazing power, have not been satisfactorily answered. 1) what is the actual nature of matter? 2) what is the universe? 3) what can explain the serendipitous fine-tuning of everything? 4) how did the first living cell arise? 5) what has caused the amazing number of evolutionary convergences? 6) what is consciousness? 7) what is spirit?

    We’ve vast data-banks of information ABOUT all of these basics but it’s only with a lot of hand-waving that anyone claims to fully answer any of the 7 questions.

    Part of my work has been in trying to clarify the issues. A humble baby-step can be found at: “Ethical Ontology Harmonizes Science, Revelation and Human Lives: . . . ” free on the web.

    Hope you keep up the good work, John Paul. We’ve still got a way to go.

    Ever in the love of Jesus; blessings from Marty

  4. The author needs to study the history of ancient Greek thought more closely. While they were a minority, there were more than a few ancient helio-centrists. Not all of the Greeks agreed with Aristotle.

    • JMJ+

      Peace to you JAD,

      Thank you for your comment, and, yes, there were certain Greek thinkers who held to a heliocentric view – Aristarchus of Samos, Selecus of Selucia, and, most of all, the one whom Copernicus and Galileo followed, Pythagoras. But the generally held belief, the one that won the day in most people’s minds, and certainly in the minds of the mediaevals, was hellocentrism, encapsulated in the models of Aristotle and, eventually, Ptolemy.

      I hope this helps to clarify, and thank you for your own clarification.

      In Corde Mariae +

  5. I really loved your comment Dr. Rice. Humble and gentlemanly. The list of 7 things was important, but then again no science may ever be able to understand or thoroughly explain them. Thank you. John Pauls article was fascinating.

  6. “Reality – physics – is infinitely complex.” Reality? Yes. Physics? No. (Not in itself, in its principles and theories, although it may be infinitely complex — i.e., not strictly comprehensible from its “human” point of view — i.e., considered as an element in the world of changing things, as an historical and human phenomenon.) Conflating reality and physics? Don’t. That is the root cause of some of the most serious endemic confusion about science and its relation to reality, as well as to other disciplines. Reality is concrete. Physics is a science, sciences are abstract. Also at least some of your “a priori principles” look like they could be just best generalizations (abstractions) from currently available observations. I’d be interested in an argument backing up your claim that they are really “a priori principles,” starting with a non-anachronistic definition of the term. And finally, in the via inventionis, falsity is not just dross; rather, as Aristotle points out, we must be grateful to those who have come before us with less adequate views, for insofar as we have found the way to more adequate views, they have helped us along that road of discovery (including the reflexive, still contentious and controverted, discovery of science itself, and of its nature and methods, and of the role of a priori principles therein, which I think you’re not getting quite right yourself). God bless!

  7. Back in the late 1960’s an astronomy text I was using actually gave in Aristotle’s own words what he considered the most important argument against the heliocentric theory. This was the absence of stellar parallax. If the Earth were moving around the sun the stars would seem to shift position as it did. In his day they could could not conceive of the vast distances between the stars which masked this effect from naked eye astronomy. It was only at the end of the 60’s that telescopes finally became precise enough to measure this effect on the closest stars.

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