To clear any misunderstandings, I am interested not in the gossipy aspect of the matter (i.e. conflicts that had mainly to do with character-clashes and idiosyncratic psychs) but rather in conflicts that today are characterized by the following:

1) Both scientists (or groups of scientists) that were involved are widely recognized as important contributors to their science.

2) The conflict lasted, and represented a deeper methodological or philosophical distance.

As for the "final result": Either some sort of synthesis has emerged, during their life-time or later, or, if not synthesized, their respective and apparently conflicting positions/approaches have come to be understood as "complementary", in some sense. But it may also be the case that the one side eventually "lost definitely the argument".

Sensibly, I am looking to cases considered "settled" by the contemporary scientific community at large, and not for current scientific debates/controversies.

One example I have to offer is from Statistics: The [Fisher] / [Neyman-Pearson] conflict regarding Hypothesis Testing (one can check this SE post on Cross Validated for stimulus). This controversy satisfies the two criteria above. The "synthesis" that has emerged is criticized by many, while there is another view that considers the two approaches as complementary.

PS: I am not sure what tags would be appropriate for this question.

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    $\begingroup$ This question received a downvote. I believe it would be useful if the downvoter shared his or her thoughts on the matter, especially because this is a new site, and so things are still under formation. After all, (s)he may have a point and the question may be characterized by some flaw that goes against the purpose of the site. $\endgroup$ Commented Nov 12, 2014 at 14:03
  • $\begingroup$ I agree, but you might not have a lot of luck. Many people support the SE "you-don't-have-to-explain-downvotes" policy. But I'm curious as to why this was downvoted; it doesn't make sense. $\endgroup$
    – HDE 226868
    Commented Nov 12, 2014 at 19:49
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    $\begingroup$ @HDE226868 I also accept the stated SE policy, which is an obvious compromise in order to avoid flame wars. Personally, I rejoice with upvotes, but I am really interested in downvotes -and I do think that for a site in its infancy, airing opinions that explain downvotes could be overall useful. And I don't see anybody here looking for a fight... $\endgroup$ Commented Nov 12, 2014 at 20:09
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    $\begingroup$ @VicAche Why having a thread with many answers collecting (but also providing information on) important scientific controversies, is "clearly not OK" here? Just trying to understand the concept. $\endgroup$ Commented Nov 22, 2014 at 16:01
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    $\begingroup$ @VicAche: could you explain (on Meta) why "catalogue" questions are not OK on your opinion? Is this stated somewhere in the site policies? On other SE sites where I participate they are OK, and there is even a special tag for them. $\endgroup$ Commented Nov 25, 2014 at 14:50

8 Answers 8


Probably the most famous conflict that satisfies your requirements is the conflict between "Ptolemy system" and "Copernic system", though few people understand this even today:-)

This conflict became so famous because of the intrusion of a non-scientific authority, that is catholic church. From the point of view of astronomy, there are two aspects:

a) the choice of coordinate system. We are taught in elementary physics courses that this is indeed a matter of choice, of convenience. Some coordinate systems are good for one purpose, others for another purpose. Heliocentric system is by far more convenient when you want to write equations of motion. But geocentric system is more convenient in navigation, where they do not care about "how planets really move" but in "how this looks from the Earth".

b) the more important question whether the orbits are combinations of circles with uniform motion, or Kepler ellipses and the motion obeys Kepler laws. Of course, the discovery of Kepler's laws was a really great discovery (probably more important than the Heliocentric system), because they led to the discovery of the law of gravity, etc., and because they have much simpler mathematical formulation. However when people try to solve the equations of motion for more than 2 bodies, they obtain a solution in a form of a trigonometric series of functions depending on uniformly changing angles, which is essentially the same as Ptolemy did.

So you can think of the final result as a representation of the motion as a combination of epicycles.

So in this case we really have a kind of synthesis after a long controversy.

Of course this conflict had also other significance beyond astronomy. I don't want to discuss philosophical consequences. The interference of the church into purely scientific matters undermined the church authority, so I would say it lost the cause in the long run.

On the other hand, Galileo is also not so innocent in triggering this conflict. (Copernicus and Kepler did not have any conflict with the church). And the main "proof" that Galileo presented for "moving Earth" was wrong. So it would be much more reasonable on the part of Galileo to hold Copernicus view that the difference between the two systems is mathematical, the choice of the coordinate system, which after all is closer to the truth.

Galileo's main "proof" was based on his totally incorrect theory of the tides which contradicted principles of mechanics he discovered himself in the young age.

EDIT. Some references. They are really abundant (any comprehensive history of astronomy). Some of my favorite in Latin aplphabet:

  1. Simon Gindikin, Tales of mathematicians and physicists. Springer, New York, 2007. (This is a collection of biographies written by professional mathematician for general public).

  2. Stillman Drake, Galileo at work. A very comprehensive scholarly analysis of Galileo's work and scientific biography, including all controversies. Based on his work and correspondence.

  3. Jean Meeus, Astronomical algorithms, Willmann-Bell, Richmond VA, 1998. How ephemerides are computed today, with complete formulas for the motion of Sun, Moon and planets, and other related calculations.

  4. John Louis Emil Dreyer, History of planetary systems from Thales to Kepler. Very good book for a beginner. Newer editions are called "History of astronomy from Thales to Kepler"

5.Jean Baptiste Joseph Delambre, Histoire de l'astronomie ancienne, Histoire de l'astronomie du Moyen Age, Histoire de l'astronomie moderne. These three books are for a serious student of history of astronomy.

  • $\begingroup$ Kuhn's The Copernican Revolution is another intersting source $\endgroup$
    – Seamus
    Commented Nov 24, 2014 at 16:45
  • $\begingroup$ I have not read this book, but I read other books of Kuhn and as a result I do not believe that his analysis of "Coperican revolution" is a good one. $\endgroup$ Commented Nov 24, 2014 at 21:19
  • $\begingroup$ If the book you've read is Structure of Scientific Revolutions, then let me reassure you that Copernican Revolution is more historical, less philosophical. Though I'd be interested to know what you objected to in what you've read of Kuhn. $\endgroup$
    – Seamus
    Commented Nov 25, 2014 at 9:45
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    $\begingroup$ Yes, it was the "Structure..." that I read. I object his whole view on "scientific revolutions", which contradict to my own views, but this is not the place to discuss this. This is a site for questions and answers, not a discussion club. And long discussions are discouraged. $\endgroup$ Commented Nov 25, 2014 at 14:42

Quite a famous example from modern physics deals with the inherent randomness of quantum theory. In the early years of quantum mechanics when the formulation in terms of wave functions was developed, the question of interpretation arose. Copenhagen interpretation, developed mainly by Niels Bohr and Werner Heisenberg became the most accepted of all the possibilities. It states that the wave function gives a full description of a system and an outcome of a measurement is random with probability distribution which can be determined by the wave function and form of measurement.

Albert Einstein was one of the scientists that did not like the idea of non-deterministic universe and argued that this randomness comes from some unknown parameters that we are not aware of. This local hidden variable theory would then be completely deterministic.

It was not until a few decades later, in 1964, when John Bell formulated inequalities that have to be obeyed by every deterministic theory but can be violated by quantum theory in an inherently random world. Since then, the violation of these inequalities has been observed many times showing that quantum theory indeed is fundamental and no deterministic theory can explain the effects that we observe.


Another famous controversy was about the age of the Earth. It was found long ago that the temperature in the very deep mines increases with depth. Using the model that the Earth evolved from a hot state when the rocks were melted, and was cooling down ever since, one could estimate the age from the known temperature of melting of the rocks and the current gradient of the temperature near the surface.

This was one of the main motivations of Fourier's seminal book Analytic theory of heat (where he invented the Fourier transform). Fourier's idea was further developed by W. Thomson (Lord Kelvin) who arrived at the estimate between 20 and 400 million years.

Geologists and Darwinists could not accept such a short time. By the way, it is interesting to now how exactly the Darwinists estimated the time necessary for the evolution in 19-th century. I will be glad if someone explains this.

As a result Thomson found himself in the camp of anti-evolutionists:-) On the other hand he was supported by such people as Helmholtz and astronomer Newcomb.

Lord Kelvin died in 1907, while radioactivity was discovered in 1896. It took a while to understand that it is radioactivity which causes additional heating of the Earth and makes Fourier and Kelvin correct calculations non-applicable. Such a sad story.


Let me also add to the list the long conflict between the wave theory and corpuscular theory of light. First serious corpuscular theory was due to Newton (correct me if I am wrong here), it was published in his Opticks. Huygens and Hooke were developing wave theory. Soon after the publication of Principia Newton become an absolute authority, first in England but some time later, when his gravity theory was brilliantly confirmed, also on the continent. This "cult of Newton" made substantial harm, especially in England. The wave theory was forgotten, almost for a century.

Only in the beginning of 19-th century, wave theory was resurrected and confirmed beyond reasonable doubt by experiment (Fresnel, Th. Young). Newton was "proved wrong" and the wave theory was widely accepted. See about "Poisson's spot" on Wikipedia about one of the most dramatic events in this story.

Everyone thought that the wave theory is the ultimate one until 1905:-) In 1905 Einstein's theory of photoelectric effect was published, which showed again that light consists of particles in some sense. The modern theory is a kind of synthesis of waves and particles, so this is perhaps the best example of what was asked:-)

  • $\begingroup$ I'm in the process of doing that. $\endgroup$
    – HDE 226868
    Commented Nov 25, 2014 at 2:27
  • $\begingroup$ Epicurus taught that light is made up of atoms. This is surely what you would call a corpuscular theory. $\endgroup$
    – fdb
    Commented Nov 26, 2014 at 10:27
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    $\begingroup$ I wrote: "first serious theory". Epicurus theory was pre-scientific. $\endgroup$ Commented Nov 26, 2014 at 14:06

You could argue that there are two big issues that have been argued:

  1. Tobacco and lung cancer: This is really a sad one. For years, the tobacco companies insisted that there wasn't a connection between tobacco and all the medical issue smokers began to have. There were some good early papers that found links, but they didn't gain much support until warnings began to be put on cigarette packs. A 1964 report established that there certainly was a link (text available here), and more long-term studies have now been done.
  2. Global warming: This is another sad story. The idea of global warming was opposed by those whom it hurt most - in this case, industry. Many scientists agree, but there are unfortunately large numbers who don't. Some quotes here are illuminating:

    It has become fashionable in some parts of the UK media to portray the scientific evidence that has been collected about climate change and the impact of greenhouse gas emissions from human activities as an exaggeration. Some articles have claimed that scientists are ignoring uncertainties in our understanding of the climate and the factors that affect it. Some have questioned the motives of the scientists who have presented the most authoritative assessments of the science of climate change, claiming that they have a vested interest in "playing up" the potential effects that climate change is likely to have.

Some assessments reports from the IPCC can be found at this site.

More important than either of those, though, was the debate about how the universe itself formed. There were originally two competing theories: the Big Bang theory and the Steady State theory. The Big Bang theory was originally conceptualized by Georges Lemaitre, who did work on the expansion of the universe in the 1920s. Decades later, George Gamow reincarnated it to compete against the other prevailing theory, the Steady State theory. Fred Hoyle was the most famous advocate of the theory (he coined the term "Big Bang" as a derogatory name). However, the dispute was settled in the 1960s, when Penzias and Wilson discovered the cosmic microwave background, which provided strong evidence for the Big Bang theory.

  • $\begingroup$ Thank you for contributing, but in your examples I don't see "two scientists", or groups of scientists, clashing on scientific grounds. These two example are the standard ones used in order to discuss how the integrity of science can be undermined, and how scientists may yield to pressure or financial lure. $\endgroup$ Commented Nov 12, 2014 at 16:29
  • $\begingroup$ @AlecosPapadopoulos Okay, true. I was working on an edit, and I think it does address your question. $\endgroup$
    – HDE 226868
    Commented Nov 12, 2014 at 16:33

Another famous controversy is the one about atomism. All German philosophers and some scientists (E. Mach, W. Ostwald) denied the existence of atoms as late as in 1904 (!) An information from Wikipedia:

In 1904 at a physics conference in St. Louis most physicists seemed to reject atoms and he [Boltzmann] was not even invited to the physics section.

Boltzmann died in 1906 (committing suicide), while Einstein and Smoluchowski theory of Brownian motion was published in 1905, and as a result the existence of atoms was experimentally proved by a series of experiments in 1908-1909, and Avogadro's number was measured; finally vindicating Boltzmann.


I am not sure whether it can be called a conflict or not, but a suitable approach to quantize gravity has caused many discussions.

Some scientists believe that spacetime itself must be quantized and someones say the bodies behave in a quantized way, not spacetime. Also someones believe that our number sets are incompatible with nature, and so on. As a result, there are several quantum theories of gravity and this problem is one of the greatest problems in physics (or maybe science, for it has a lot of influences on mathematics, astronomy and philosophy at the first level, and on biology at next levels).

These days, string theory (ST) and loop quantum gravity (LQG) with two different viewpoints are the most important candidates to solve the problem, but twistor theory, topos theory, non-commutative gravity and quantum field theory in curved spacetimes, are examples of other theories which have not been as successful as ST or LQG. Almost all of these theories have some inconsistencies or even if they are consistent, they can't be easily tested by experiment.


Mantell v/s Owen, UK, 1830's/1840's (which of them deserved the credit for discovering the dinosaurs in the 1830's? - Owen was the first to name them - but Mantell had laid the groundwork: see Debbie Cadbury 'The Dinosaur Hunters')


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