Tag Archives: Galileo

Skepticism, Science and Scientism

By Tim Harding B.Sc.

(An edited version of this essay was published in The Skeptic magazine,
September 2017, Vol 37 No 3)

In these challenging times of anti-science attitudes and ‘alternative facts’, it may sound strange to be warning against excessive scientific exuberance.  Yet to help defend science from these attacks, I think we need to encourage scientists to maintain their credibility amongst non-scientists.

In my last article for The Skeptic (‘I Think I Am’, March 2017), I traced the long history of skepticism over the millennia.  I talked about the philosophical skepticism of Classical Greece, the skepticism of Modern Philosophy dating from Descartes, through to the contemporary form of scientific skepticism that our international skeptical movement now largely endorses.  I quoted Dr. Steven Novella’s definition of scientific skepticism as ‘the application of skeptical philosophy, critical thinking skills, and knowledge of science and its methods to empirical claims, while remaining agnostic or neutral to non-empirical claims (except those that directly impact the practice of science).’

Despite the recent growth of various anti-science movements, science is still widely regarded as the ‘gold standard’ for the discovery of empirical knowledge, that is, knowledge derived from observations and experiments.  Even theoretical physics is supposed to be empirically verifiable in principle when the necessary technology becomes available, as in the case of the Higgs boson and Einstein’s gravitational waves.  But empirical observations are not our only source of knowledge – we also use reasoning to make sense of our observations and to draw valid conclusions from them.  We can even generate new knowledge through the application of reasoning to what we already know, as I shall discuss later.

Most skeptics (with a ‘k’) see science as a kind of rational antidote to the irrationality of pseudoscience, quackery and other varieties of woo.  So we naturally tend to support and promote science for this purpose.  But sometimes we can go too far in our enthusiasm for science.  We can mistakenly attempt to extend the scope of science beyond its empirical capabilities, into other fields of inquiry such as philosophy and politics – even ethics.  If only a small number of celebrity scientists lessen their credibility by making pronouncements beyond their individual fields of expertise, they render themselves vulnerable to attack by our opponents who are looking for any weaknesses in their arguments.  In doing so, they can unintentionally undermine public confidence in science, and by extension, scientific skepticism.

The pitfalls of crude positivism

Logical positivism (sometimes called ‘logical empiricism’) was a Western philosophical movement in the first half of the 20th century with a central thesis of verificationism; which was a theory of knowledge which asserted that only propositions verifiable through empirical observation are meaningful.

One of the most prominent proponents of logical positivism was Professor Sir Alfred Ayer (1910-1989) pictured below.  Ayer is best known for popularising the verification principle, in particular through his presentation of it in his bestselling 1936 book Language, Truth, and Logic.  Ayer’s thesis was that a proposition can only be meaningful if it has verifiable empirical content, otherwise it is either a priori (known by deduction) or nonsensical.  Ayer’s philosophical ideas were deeply influenced by those of the Vienna Circle and the 18th century empiricist philosopher David Hume.

James Fodor, who is a young Melbourne science student, secularist and skeptic has critiqued a relatively primitive form of logical positivism, which he calls ‘crude positivism’.  He describes this as a family of related and overlapping viewpoints, rather than a single well-defined doctrine, the three most commonly-encountered components of which are the following:

(1) Strict evidentialism: the ultimate arbiter of knowledge is evidence, which should determine our beliefs in a fundamental and straightforward way; namely that we believe things if and only if there is sufficient evidence for them.

(2) Narrow scientism: the highest, or perhaps only, legitimate form of objective knowledge is that produced by the natural sciences. The social sciences, along with non-scientific pursuits, either do not produce real knowledge, or only knowledge of a distinctly inferior sort.

(3) Pragmatism: science owes its special status to its unique ability to deliver concrete, practical results: it ‘works’.  Philosophy, theology, and other such fields of inquiry do not produce ‘results’ in this same way, and thus have no special status.

Somewhat controversially, Fodor classifies Richard Dawkins, Sam Harris, Peter Boghossian, Neil de Grasse Tyson, Lawrence Krauss, and Stephen Hawking as exponents of crude positivism when they stray outside their respective fields of scientific expertise into other fields such as philosophy and social commentary.  (Although to be fair, Lawrence Krauss wrote an apology in a 2012 issue of Scientific American, for seemingly dismissing the importance of philosophy in a previous interview he gave to The Atlantic).

Fodor’s component (1) is a relatively uncontroversial viewpoint shared by most scientists and skeptics.  Nevertheless, Fodor cautions that crude positivists often speak as if evidence is self-interpreting, such that a given piece of evidence automatically picks out one singular state of affairs over all other possibilities.  In practice, however, this is almost never the case because the interpretation of evidence nearly always requires an elaborate network of background knowledge and pre-existing theory.  For instance, the raw data from most scientific observations or experiments are unintelligible without the use of background scientific theories and methodologies.

It is Fodor’s components (2) and (3) that are likely to be more controversial, and so I will now discuss them in more detail.

The folly of scientism

What is ‘scientism’ – and how is it different from the natural enthusiasm for science that most skeptics share?  Unlike logical positivism, scientism is not a serious intellectual movement.  The term is almost never used by its exponents to describe themselves.  Instead, the word scientism is mainly used pejoratively when criticising scientists for attempting to extend the boundaries of science beyond empiricism.

Warwick University philosopher Prof. Tom Sorell has defined scientism as: ‘a matter of putting too high a value on natural science in comparison with other branches of learning or culture.’  In summary, a commitment to one or more of the following statements lays one open to the charge of scientism:

  • The natural sciences are more important than the humanities for an understanding of the world in which we live, or even all we need to understand it;
  • Only a scientific methodology is intellectually acceptable. Therefore if the humanities are to be a genuine part of human knowledge they must adopt it; and
  • Philosophical problems are scientific problems and should only be dealt with as such.

At the 2016 Australian Skeptics National Convention, former President of Australian Skeptics Inc., Peter Bowditch, criticized a recent video made by TV science communicator Bill Nye in which he responded to a student asking him: ‘Is philosophy meaningless?’  In his rambling answer, Nye confused questions of consciousness and reality, opined that philosophy was irrelevant to answering such questions, and suggested that our own senses are more reliable than philosophy.  Peter Bowditch observed that ‘the problem with his [Nye’s] comments was not that they were just wrong about philosophy; they were fractally wrong.  Nye didn’t know what he was talking about. His concept of philosophy was extremely naïve.’  Bill Nye’s embarrassing blunder is perhaps ‘low hanging fruit’; and after trenchant criticism, Nye realised his error and began reading about philosophy for the first time.

Some distinguished scientists (not just philosophers) are becoming concerned about the pernicious influence of scientism.  Biological sciences professor Austin Hughes (1949-2015) wrote ‘the temptation to overreach, however, seems increasingly indulged today in discussions about science. Both in the work of professional philosophers and in popular writings by natural scientists, it is frequently claimed that natural science does or soon will constitute the entire domain of truth. And this attitude is becoming more widespread among scientists themselves. All too many of my contemporaries in science have accepted without question the hype that suggests that an advanced degree in some area of natural science confers the ability to pontificate wisely on any and all subjects.’

Prof. Hughes notes that advocates of scientism today claim the sole mantle of rationality, frequently equating science with reason itself.  Yet it seems the very antithesis of reason to insist that science can do what it cannot, or even that it has done what it demonstrably has not.  He writes ‘as a scientist, I would never deny that scientific discoveries can have important implications for metaphysics, epistemology, and ethics, and that everyone interested in these topics needs to be scientifically literate. But the claim that science and science alone can answer longstanding questions in these fields gives rise to countless problems.’

Limitations of science

The editor of the philosophical journal Think and author of The Philosophy Gym, Prof. Stephen Law has identified two kinds of questions to which it is very widely supposed that science cannot supply answers:

Firstly, philosophical questions are for the most part conceptual, rather than scientific or empirical.  They are usually answered by the use of reasoning rather than empirical observations.  For example, Galileo conducted a famous thought experiment by reason alone.  Imagine two objects, one light and one heavier than the other one, are connected to each other by a string.  Drop these linked objects from the top of a tower.  If we assume heavier objects do indeed fall faster than lighter ones (and conversely, lighter objects fall slower), the string will soon pull taut as the lighter object retards the fall of the heavier object.  But the linked objects together are heavier than the heavy object alone, and therefore should fall faster. This logical contradiction leads one to conclude the assumption about heavier objects falling faster is false.  Galileo figured this conclusion out in his head, without the assistance of any empirical experiment or observation.  In doing so, he was employing philosophical rather than scientific methods.

Secondly, moral questions are about what we ought or ought not to do.  In contrast, the empirical sciences, on their own, appear capable of establishing only what is the case.  This is known as the ‘is/ought gap’. Science can provide us with factual evidence that might influence our ethical judgements but it cannot provide us with the necessary ethical values or principles.  For example, science can tell us how to build nuclear weapons, but it cannot tell us whether or not they should ever be used and under what circumstances.  Clinical trials are conducted in medical science, often using treatment groups versus control groups of patients.  It is bioethics rather than science that provides us with the moral principles for obtaining informed patient consent for participation in such clinical trials, especially when we consider that control groups of patients are being denied treatments that could be to their benefit.

I have given the above examples not to criticise science in any way, but simply to point out that science has limitations, and that there is a place for other fields of inquiry in addition to science.

Is pragmatism enough?

Coming back to Fodor’s component (3) of crude positivism, he makes a good point that a scientific explanation that ‘works’ is not necessarily true.  For instance, Claudius Ptolemy of Alexandria (c. 90CE – c. 168CE) explained how to predict the behavior of the planets by introducing ad hoc notions of the deferent, equant and epicycles to the geocentric model of what is now known as our solar system.  This model was completely wrong, yet it produced accurate predictions of the motions of the planets – it ‘worked’.  Another example was Gregor Mendel’s 19th century genetic experiments on wrinkled peas.  These empirical experiments adequately explained the observed phenomena of genetic variation without even knowing what genes were or where they were located in living organisms.

Ptolemy model

Schematic diagram of Ptolemy’s incorrect geocentric model of the cosmos

James Fodor argues that just because scientific theories can be used to make accurate predictions, this does not necessarily mean that science alone always provides us with accurate descriptions of reality.  There is even a philosophical theory known as scientific instrumentalism, which holds that as long as a scientific theory makes accurate predictions, it does not really matter whether the theory corresponds to reality.  The psychology of perception and the philosophies of mind and metaphysics could also be relevant.  Fodor adds that many of the examples of science ‘delivering results’ are really applications of engineering and technology, rather than the discovery process of science itself.

Fodor concludes that if the key to the success of the natural sciences is adherence to rational methodologies and inferences, then it is those successful methods that we should focus on championing, whatever discipline they may be applied in, rather than the data sets collected in particular sciences.

Implications for science and skepticism

Physicist Ian Hutchison writes ‘the health of science is in fact jeopardised by scientism, not promoted by it.  At the very least, scientism provokes a defensive, immunological, aggressive response in other intellectual communities, in return for its own arrogance and intellectual bullyism.  It taints science itself by association’.  Hutchinson suggests that perhaps what the public is rejecting is not actually science itself, but a worldview that closely aligns itself with science — scientism.  By disentangling these two concepts, we have a much better chance for enlisting public support for scientific research.

The late Prof. Austin Hughes left us with a prescient warning that continued insistence on the universal and exclusive competence of science will serve only to undermine the credibility of science as a whole. The ultimate outcome will be an increase in science denialism that questions the ability of science to address even the questions legitimately within its sphere of competence.


Ayer, Alfred. J. (1936), Language Truth and Logic, London: Penguin.

Bowditch, Peter ‘Is Philosophy Dead?’ Australasian Science July/August 2017.

Fodor, James ‘Not so simple’, Australian Rationalist, v. 103, December 2016, pp. 32–35.

Harding, Tim ‘I Think I Am’, The Skeptic, Vol. 37 No. 1. March 2017, pp. 40-44.

Hughes, Austin L ‘The Folly of Scientism’, The New Atlantis, Number 37, Fall 2012, pp. 32-50.

Hutchinson, Ian. (2011) Monopolizing Knowledge: A Scientist Refutes Religion-Denying, Reason-Destroying Scientism. Belmont, MA: Fias Publishing.

Krauss, Lawrence ‘The Consolation of PhilosophyScientific American Mind, April 27, 2012.

Law, Stephen, ‘Scientism, the limits of science, and religionCenter for Inquiry (2016), Amherst, NY.

Novella, Steven (15 February 2013). ‘Scientific Skepticism, Rationalism, and Secularism’. Neurologica (blog). Retrieved 12 February 2017.

Sorell, Thomas (1994), Scientism: Philosophy and the Infatuation with Science, London: Routledge.

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Amanda Vanstone on university students

‘Universities, once the bastions of freedom of thought, the place above all others where one could express contentious views have become beacons of political correctness. Students now need to be warned if there is something in a lecture which they might find difficult. Guest lecturers cancel speeches because students disapproving of their views threaten disruptive demonstrations. If we think the Catholic Church giving Galileo a rough time was medieval what do we think of students, rather than the university, deciding what they are prepared to hear.’ – Amanda Vanstone

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The Galileo gambit and other stories: the three main tactics of climate denial

The Conversation
Stephan Lewandowsky, University of Bristol

The recently elected One Nation senator from Queensland, Malcolm Roberts, fervently rejects the established scientific fact that human greenhouse gas emissions cause climate change, invoking a fairly familiar trope of paranoid theories to propound this belief.

Roberts variously claims that the United Nations is trying to impose world government on us through climate policy, and that CSIRO and the Bureau of Meteorology are corrupt institutions that, one presumes, have fabricated the climate extremes that we increasingly observe all over the world.

In the world of Malcolm Roberts, these agencies are marionettes of a “cabal” of “the major banking families in the world”. Given the parallels with certain strands of anti-Jewish sentiment, it’s perhaps an unfortunate coincidence that Roberts has reportedly relied on a notorious Holocaust denier to support this theory.

It might be tempting to dismiss his utterances as conspiratorial ramblings. But they can teach us a great deal about the psychology of science denial. They also provide us with a broad spectrum of diagnostics to spot pseudoscience posing as science.

The necessity of conspiracism

First, the appeal to a conspiracy among scientists, bankers and governments is never just a slip of the tongue but a pervasive and necessary ingredient of the denial of well-established science. The tobacco industry referred to medical research on lung cancer as being conducted by an “oligopolistic cartel” that “manufactures alleged evidence”. Some people accuse the US Central Intelligence Agency (CIA) of creating and spreading AIDS, and much anti-vaccination content on the web is suffused with conspiratorial allegations of totalitarianism.

This conspiratorial mumbo jumbo inevitably arises when people deny facts that are supported by an overwhelming body of evidence and are no longer the subject of genuine debate in the scientific community, having already been tested thoroughly. As evidence mounts, there comes a point at which inconvenient scientific findings can only be explained away by recourse to huge, nebulous and nefarious agendas such as the World Government or Stalinism.

If you are addicted to nicotine but terrified of the effort required to give up smoking, it might be comforting instead to accuse medical researchers of being oligopolists (whatever that means).

Likewise, if you are a former coal miner, like Malcolm Roberts, it is perhaps easier to accuse climate scientists of colluding to create a world government (whatever that is) than to accept the need to take coal out of our economy.

There is now ample research showing the link between science denial and conspiracism. This link is supported by independent studies from around the world.

Indeed, the link is so established that conspiracist language is one of the best diagnostic tools you can use to spot pseudoscience and science denial.

The Galileo gambit

How else can science dissenters attempt to justify their contrarian position? Another tactic is to appeal to heroic historical dissenters, the usual hero of choice being Galileo Galilei, who overturned the orthodoxy that everything revolves around the Earth.

This appeal is so common in pseudoscientific quackery that it is known as the Galileo gambit. The essence of this argument is:

They laughed at Galileo, and he was right.

They laugh at me, therefore I am right.

A primary logical difficulty with this argument is that plenty of people are laughed at because their positions are absurd. Being dismissed by scientists doesn’t automatically entitle you to a Nobel Prize.

Another logical difficulty with this argument is that it implies that no scientific opinion can ever be valid unless it is rejected by the vast majority of scientists. Earth must be flat because no scientist other than a Googling Galileo in Gnowangerup says so. Tobacco must be good for you because only tobacco-industry operatives believe it. And climate change must be a hoax because only the heroic Malcolm Roberts and his Galileo Movement have seen through the conspiracy.

Yes, Senator-elect Roberts is the project leader of the Galileo Movement, which denies the scientific consensus on climate change, favouring instead the opinions of a pair of retired engineers and the radio personality Alan Jones.

Any invocation of Galileo’s name in the context of purported scientific dissent is a red flag that you’re being fed pseudoscience and denial.

The sounds of science

The rejection of well-established science is often couched in sciency-sounding terms. The word “evidence” has assumed a particular prominence in pseudoscientific circles, perhaps because it sounds respectable and evokes images of Hercule Poirot tenaciously investigating dastardly deeds.

Since being elected, Roberts has again aired his claim that there is “no empirical evidence” for climate change.

But “show us the evidence” has become the war cry of all forms of science denial, from anti-vaccination activists to creationists, despite the existence of abundant evidence already.

This co-opting of the language of science is a useful rhetorical device. Appealing to evidence (or a lack thereof) seems reasonable enough at first glance. Who wouldn’t want evidence, after all?

It is only once you know the genuine state of the science that such appeals are revealed to be specious. Literally thousands of peer-reviewed scientific articles and the national scientific academies of 80 countries support the pervasive scientific consensus on climate change. Or, as the environmental writer George Monbiot has put it:

It is hard to convey just how selective you have to be to dismiss the evidence for climate change. You must climb over a mountain of evidence to pick up a crumb: a crumb which then disintegrates in the palm of your hand. You must ignore an entire canon of science, the statements of the world’s most eminent scientific institutions and thousands of papers published in the foremost scientific journals.

Accordingly, my colleagues and I recently showed that in a blind test – the gold standard of experimental research – contrarian talking points about climate indicators were uniformly judged to be misleading and fraudulent by expert statisticians and data analysts.

Conspiracism, the Galileo gambit and the use of sciency-sounding language to mislead are the three principal characteristics of science denial. Whenever one or more of them is present, you can be confident you’re listening to a debate about politics or ideology, not science.

The ConversationStephan Lewandowsky, Chair of Cognitive Psychology, University of Bristol

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.

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Galileo gambit

The Galileo gambit (also Galileo fallacy; users of the fallacy are Galileo wannabes) is a logical fallacy and/or a rhetorical tactic that asserts that if your ideas provoke ‘the establishment’ to ridicule or vilify you, then you must be right.

It refers to Galileo Galilei‘s famous persecution at the hands of the Roman Catholic Church for his defence of heliocentrism in the face of the orthodox Biblical literalism of the day.  The fallacy is an appeal to the minority and a conditional fallacy.

The structure of the argument is:

Premise 1: A is X and Y
Premise 2: B is X.
Conclusion 1: B is Y.

For example, ‘They made fun of Galileo, and he was right. They make fun of me, therefore I am right’. A common rebuttal is ‘They also made fun of the Three Stooges’. An additional irony arises when we consider that if the maverick idea does manage to amass enough evidence to win over the majority, it will become the new consensus — at which point, by the fallacy’s own invalid reasoning, the idea must become wrong!


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Jupiter at its best for 2015

The Conversation

By Tanya Hill, Museum Victoria

This month is a great time to catch Jupiter shining brilliantly in the evening sky. And for the next few weeks it will be its best and brightest for the year.

The planet reaches opposition at 5:09am on Saturday morning, February 7 (AEDT). At that time, the sun is located on one side of the Earth and Jupiter is found directly opposite, on the other side of the Earth.

This positions Jupiter opposite the sun and on the the night-side of the Earth. Hence, the planet rises as the sun sets, is overhead around midnight (when the sun is directly below us) and sets as the sun rises. But not only do we get to see Jupiter all night long, we also see it at its brightest.

Being the largest planet, Jupiter is always easy to see. It is only rivalled by Venus, which is brighter than Jupiter because it is much closer and its thick atmosphere reflects sunlight really well.

But around the time of opposition Jupiter really dazzles. This is because, with both Earth and Jupiter located on the same side of the sun, the two planets are closest together for the year. This year they will be separated by 650-million km.

By August, Earth will have swung around the sun, but Jupiter won’t have moved that far. This will bring Jupiter into solar conjunction.The two planets will be found on opposite sides of the solar system, taking them furthest apart for the year. At that time the distance between them will be almost 960-million km. And of course, we won’t see Jupiter because it will appear with the sun in the daytime sky.

Not all oppositions are created equal.

The best oppositions occur when Jupiter is near perihelion or closest to the sun. It makes sense, because if Jupiter is slightly closer to the sun, then opposition will also bring the planet a little closer to Earth.

Jupiter’s last perihelion passage was in March 2011 and the next will be in January 2023, in step with its 11.9 year orbit.

So for the next few years, oppositions aren’t as favourable as they could be. But don’t let this put you off. Look towards the north-east in the evening and it’s a beautiful sight to see Jupiter shining so brightly.

Jupiter is easily the brightest object in the north-eastern sky at sunset. Source: Museum Victoria/Stellarium

It’s also really easy to notice that Jupiter’s light is much steadier than the light from any nearby stars. Jupiter’s increased angular size makes it less susceptible to turbulence in our atmosphere. Or in other words, stars twinkle easily, but planets don’t.

Moon shadows

We now know of 67 moons orbiting Jupiter, but the planet’s four largest moons – Io, Europa, Ganymede and Callisto – are worlds in their own right. They are easily seen in a good pair of binoculars or a small telescope, as tiny star-like objects, strung in a line that can cross either side of Jupiter.

On January 23, the Hubble Space Telescope (HST) captured a rare triple transit shadow – the shadows of Europa, Callisto and Io were seen moving across the surface of Jupiter.

Triple transit shadows can only occur if Callisto is one of the moons involved. This is because, Io, Europa and Ganymede – which all orbit closer to Jupiter than Callisto – are locked in a 1:2:4 orbital resonance. Hence, it is impossible to have all three moons suitably positioned together.

However, there is a problem with needing Callisto for a triple transit. Callisto’s orbit is slightly tilted so that a lot of the time its shadow misses the planet. Shadow transits of Callisto occur in seasons – the current one began in 2013 and will continue until 2016. A list of shadow transits can be found here, although currently they favour North America and are not visible across Australia.

Eclipses and Occultations

What’s more, this triple shadow transit occurred during a period when the Earth and sun are crossing Jupiter’s equatorial plane. This occurs, about every five to six years and during this time Jupiter’s moons can appear to overlap one another.

Sometimes an eclipse is produced when the shadow of one moon passes across another. At other times, the line-up causes an occultation when one moon passes in front of another and obscures it from sight.

Io lines up with Callisto’s shadow. Source: NASA, ESA, Hubble Heritage Team

Just before the HST began observing the triple shadow transit, Io had been eclipsed by Callisto. The first image taken by the telescope shows Io just after it has moved out of Callisto’s shadow.

It’s always interesting to follow the changing positions of Jupiter’s moons through a telescope. I like to imagine what it must have been like for Galileo, as he tracked the moons for the very first time.

On early Saturday morning, around the time of opposition, Europa and Ganymede will be very close together. Europa is set to occult Ganymede (or move in front of it) around 6am (AEDT).

Jupiter’s largest moons appear as four tiny points of light through a telescope. On Saturday morning Europa will pass by Ganymede as shown in the close up on the right. Source: Museum Victoria/Starry Night

The Institute of Celestial Mechanics and Calculation of Ephemerides, in Paris, runs an international campaign to collect data obtained by amateur astronomers during occultations and eclipses of Jupiter’s moons. The observations are used to track how the orbits of Jupiter’s moons are slowly changing over time, as the moons interact gravitationally with each other and Jupiter.

The ConversationThis article was originally published on The Conversation. (Reblogged by permission). Read the original article.

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The Astronomical Renaissance

by Tim Harding

(An edited version of this essay was published in The Skeptic magazine, March 2015, Vol 35 No 1, under the title ‘Rebirth of the Universe’.  The essay is based on a talk presented to the Mordi Skeptics, Tuesday 11 November 2014).

This article follows on from my previous one on ancient astronomy and astrology (‘An Eye to the Sky’, The Skeptic, Vol. 33, No. 4, December 2013).  That story began about 4000 years ago in Babylon, then moved to the first scientific revolution in ancient Greece, ending with Ptolemy’s complicated geocentric (Earth-centred) model of the cosmos in the 2nd century CE.

We now make a great leap forward to the second scientific revolution beginning with the publication of Nicolaus Copernicus’ heliocentric (Sun-centred) model of the cosmos in 1543 CE.  Why the huge gap?  Because astonishingly, nothing much happened in cosmology for about 1400 years between Ptolemy and Copernicus.  (The reasons for this are complex and best left to a possible future article).

After the Fall of Constantinople in 1453 CE, there was a rediscovery of ancient Greek texts written by philosophers and scientists such as Plato, Aristotle, Aristarchus, Archimedes and Ptolemy.  That is why this subsequent period is described as an astronomical renaissance (alongside the cultural renaissance), from the French word meaning ‘re-birth’.  The midwives of this re-birth were the development of scientific methods and the invention of printing, which would improve access to learning, allowing a faster propagation of new ideas.

Copernicus’s astronomical observations were complemented and improved in accuracy by those of Tycho Brahe.  His heliocentric model was later adopted by Galileo Galilei and then refined by Johannes Kepler.

Nicholas Copernicus (1473- 1573 CE)

Copernicus was born 1473 in the Polish city of Torun.  His father was copper merchant – the name ‘Copernicus’ is thought to be derived from this occupation.  He studied mathematics, philosophy and astronomy at the University of Krakow; then medicine at Padua in Italy.  He was also a lawyer, physician, classics scholar, translator and economist.

copernicusatwork2 crop

Nicolaus Copernicus

As well as being a polymath, Copernicus was also a polyglot, which gave him access to the ancient Greek texts.  From these writings he would most likely have known that Aristarchus of Samos had some 1800 years earlier proposed a heliocentric model of the cosmos in the third century BCE.  Aristarchus had also calculated the diameters of the Sun and Moon, as well as their distances from the Earth in Earth radii.  This regression from the correct heliocentric to the incorrect geocentric model presents a serious challenge to our notions of inevitable human progress.

In around 1510, Copernicus moved to one of the defensive towers of the cathedral town of Frombork on the Baltic Sea coast, where he did most of his astronomical observations and writing.  His attempts at retrofitting cosmological theory to seemingly endless observational anomalies eventually became just too complex.  Simplification became a major motivation for Copernicus to construct his revolutionary heliocentric model.  His colleague Andreas Osiander, a Lutheran theologian, wrote an anonymous preface to Copernicus’ published major work De Revolutionibus.  This preface stated that Copernicus’ system was merely mathematics intended to aid computation and not an attempt to declare literal truth.  Both Copernicus and Osiander probably feared the reaction not only of other astronomers but also the Roman Church – a fear that was later justified by the trial of Galileo, of which more will be said later.  The delay in publication until the eve of Copernicus’ death is thought to be due to these fears.

Thirty years earlier in about 1514, Copernicus had written the Commentariolus – an unpublished outline of his later De Revolutionibus. In this outline, he proposed seven axioms, all of which are true:

  1. Heavenly bodies do not all move around same centre.
  2. The Earth is not centre of the cosmos – only the Moon’s orbit.
  3. The Sun is the centre of the planetary system.
  4. The Stars are much further away than the Sun.
  5. The apparent daily revolution of the stars and planets is due to the Earth’s rotation on its own axis.
  6. The apparent annual motion of the Sun is due to the revolution of Earth around the Sun.
  7. The apparent retrograde motion of the planets has same cause.

Copernicus’ heliocentric model of the cosmos

However, Copernicus clung to the erroneous theological belief that all the orbits of celestial bodies must be perfect circles.  This forced Copernicus to retain Ptolemy’s complex system of planetary epicycles, thus leading him astray.  At first, Copernicus initially proposed that only 34 epicycles were needed in his model, but he was later forced to modify the model by increasing this number to 48 – eight more cycles than the 40 in Ptolemy’s model.  These anomalies led Kepler to subsequently propose elliptical rather than circular planetary orbits, as will be discussed later.

Copernicus also modified his model to account for the apparent absence of stellar parallax during the Earth’s orbit around the Sun.  He did this by postulating that the distance of the fixed stars was so immense compared to the diameter of the earth’s orbit that stellar parallax was unnoticeable by the accuracy of astronomical observations at that time.  This modification subsequently turned out to be correct in reality, but at the time it was an ad hoc modification made for the purpose of correcting an imagined observational anomaly.

Tycho Brahe (1546 – 1601 CE)

Tycho Brahe was a colourful character, born 1546 into an aristocratic family in Scania which was then part of Denmark but is now in Sweden. He studied law and astronomy at University of Copenhagen.  He is notorious for losing part of his nose in sword fight, so he had to wear a brass prosthetic nose.  Another piece of irrelevant trivia is that Tycho had a pet Elk that once drank too much beer at one of his friends’ dinner parties.  Sadly, the inebriated Elk fell down some stairs and died.

Tycho’s observatory on the island of Hven in Sweden

Tycho’s observatory on the island of Hven in Sweden

In 1597, Tycho fell out with Danish King Christian IV and became court astronomer to Holy Roman Emperor Rudolph II in Prague, who funded the building of a state-of-the-art new observatory for Tycho.  Johannes Kepler was employed as Tycho’s assistant, who later used Tycho’s more accurate observational data for his own astronomical calculations.  These more precise measurements clearly showed that the stars lacked parallax, thus confirming that either the Earth was stationary or the stars were a vast distance from the Earth.

Tycho proposed a hybrid ‘geo-heliocentric’ system in which the Sun and Moon orbited the Earth, while the other planets orbited the Sun (known as the Tychonic system). This system provided a safe position for astronomers who were dissatisfied with the Ptolemaic model but were reluctant to endorse the Copernican model.  The Tychonic system became more popular after 1615 when Rome decided officially that the heliocentric model was contrary to both philosophy and scripture, and could be discussed only as a computational convenience that had no connection to the truth.

Galileo Galilei (1564- 1642 CE)

Galileo Galilei was a physicist, mathematician, engineer, astronomer, and philosopher who arguably contributed more than anybody to both the second scientific revolution and the astronomical renaissance.  He was born 1564 in Pisa, Italy, and educated in the Camaldolese Monastery at Vallombrosa, 35 km southeast of Florence.  He enrolled at the University of Pisa for a medical degree, but switched to mathematics and natural philosophy.

Galileo Galilei

Galileo Galilei

Galileo’s contributions to observational astronomy include the telescopic confirmation of the phases of Venus, the discovery of the four largest satellites of Jupiter (named the Galilean moons in his honour), the roughness of the Moon’s surface, and the observation and analysis of sunspots. He also made contributions to physics, including the science of dynamics, leading to Newton’s laws of motion later on.

He championed Copernicus’ heliocentrism when it was still controversial – most astronomers at this time subscribed to either geocentrism or the Tychonic system.  They doubted heliocentrism due to the absence of an observed stellar parallax, without appreciating the enormous distances involved.

When confronted with this absence of stellar parallax, Galileo attempted an ad hoc modification to the Copernican model by incorrectly claiming that the tides are caused by the earth’s rotation combined with its orbit around the Sun.  This is despite the ancient Greek philosopher Seleucus some 1600 years earlier having correctly theorized that tides were caused by the gravitational effect of the Moon’s orbit around the Earth.  .

Galileo showing his telescope to the Doge of Venice

Galileo showing his telescope to the Doge of Venice

After the Roman Inquisition of 1615, works advocating the Copernican system were placed on the index of banned books and Galileo was forbidden from advocating heliocentrism.  This resulted in heated correspondence between Galileo and the Vatican.  Unfortunately, Galileo’s aggressive manner alienated not only the Pope but also the Jesuits, both of whom had tolerated him up until this point. He was tried by the Holy Office and found ‘vehemently suspect of heresy’, then forced to recant, and spent the rest of his life under house arrest.

At least Galileo did not suffer the cruel fate of the philosopher and cosmologist Giordano Bruno, who in 1600 was burned at the stake for heresy in Rome’s Campo de’ Fiori (a market square where there is now a statue of him).  Bruno had gone even further than the Copernican model, correctly proposing that the stars were just distant suns surrounded by their own exoplanets.  He suggested the possibility that these planets could even foster life of their own (a philosophical position known as cosmic pluralism).  Bruno also believed that the Universe is in fact infinite, thus having no celestial body at its ‘center’.

Johannes Kepler (1571- 1630 CE)

Johannes Kepler was a German mathematician, astronomer and astrologer (before these areas of study separated). A key figure in the second scientific revolution, he is best known for his three laws of planetary motion, which endure today. These laws also provided one of the foundations for Isaac Newton’s theory of universal gravitation.

Kepler was born in 1571 in Stuttgart area of Germany. At age six, he observed the Great Comet of 1577, and at age nine, the lunar eclipse of 1580.  These events inspired him to study philosophy, theology mathematics and astronomy at the University of Tübingen.  Here he learned both the Ptolemaic system and the Copernican system of planetary motion.  He later observed a bright supernova (exploding star) of 1604, which became known as Kepler’s Supernova.

After graduation, Kepler became a mathematics teacher at a seminary school in Graz, Austria. Later he became an assistant to astronomer Tycho Brahe, and eventually the imperial mathematician to Emperor Rudolf II and his two successors Matthias and Ferdinand II. He was also a mathematics teacher in Linz, Austria, and an adviser to General Wallenstein. Additionally, he did fundamental work in the field of optics, invented an improved version of the refracting telescope (the Keplerian Telescope).

Frontispiece to the Rudolphine Tables (Latin: Tabulae Rudolphinae) consisting of a star catalogue and planetary tables published by Johannes Kepler in 1627, using some observational data collected by Tycho Brahe

Frontispiece to the Rudolphine Tables consisting of a star catalogue and planetary tables published by Johannes Kepler in 1627, using observational data collected by Tycho Brahe

Kepler then set about calculating the entire orbit of Mars, using the geometrical rate law and assuming an egg-shaped ovoid orbit. After many failed attempts, in early 1605 he at last hit upon the idea of an ellipse, which he had previously assumed to be too simple a solution for earlier astronomers to have overlooked. Finding that an elliptical orbit fitted the Mars data, he immediately concluded that all planets move in ellipses, with the sun at one focus — which became Kepler’s first law of planetary motion.

He then formulated two more laws of planetary motion.  These are firstly, that a line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time; and secondly, that the square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit.

Because of his religious beliefs, Kepler became convinced that God had created the universe according to perfectly harmonious geometrical shapes and patterns. He began by exploring regular polygons and regular solids, including the figures that would come to be known as Kepler’s solids.  Unfortunately, Kepler wasted a lot of his time fruitlessly searching for this underlying ‘harmony of the spheres’, drawing all sorts of weird and wonderful diagrams.  He even (unsuccessfully) tried to relate these geometric shapes to musical harmonies.

Keplers solids

Kepler’s solids

Concluding remarks

The great physicist Isaac Newton was later able to build upon the pioneering work of Galileo and Kepler, leading him to make his famous quotation ‘If I have seen further it is only by standing on the shoulders of giants’.

In contrast, it is perplexing to observe two great human failures. Firstly, how science was repeatedly led astray by fruitless searches for perfection in ‘God’s design of the cosmos’.  Secondly, that astronomical knowledge not only progressed very little during the 1400 years between Ptolemy and Copernicus, but in some areas it actually regressed.  The ancient Greeks had not only proposed a heliocentric model of the cosmos, but they had also calculated the diameters of the Sun and Moon, as well as their distances from the Earth.  They also knew that the tides were caused the gravitational effect of the Moon’s orbit around the Earth.  This valuable knowledge was either forgotten or rejected until the astronomical renaissance some 1800 years later. So much for the notion of inevitable human progress.


Koestler, A (1959) The Sleepwalkers. London: Hutchinson.

Kuhn, T.S. (1962) The Structure of Scientific Revolutions 3rd ed. Chicago: University of Chicago Press.

Toulmin, S. and Goodfield, J. (1961) The Fabric of the Heavens.  London: Hutchinson.

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