The Copernicus case / Dennis Danielson and Christopher M. Gurney

It is known that Copernicus claimed that the earth revolved around the sun. But the opposition to this revolutionary idea came not only from the religious authorities. There was also evidence to support a different cosmology.

In 2011, a team of researchers from CERN sent a beam of neutrino particles on a journey of 730 kilometers to the Gran Sasso National Laboratories in the Italian city of L'Aquile. When the researchers measured the duration of this journey, it was seen that the neutrino particles moved at a speed slightly greater than the speed of light in a vacuum. How did the scientific community react to this surprising result?

Almost all of them preferred not to abandon the well-established theory of Albert Einstein, who claimed that nothing can move faster than the speed of light, and instead claimed that the researchers' measurements were fundamentally wrong (as it turned out in the end).

Now imagine yourself in the future, four hundred years from now, a future where Einstein's ideas have been disproved; Already a long time ago, scientists proved in experiments that neutrino particles can indeed move at a speed greater than the speed of light. At this point in time, when we look back at the physicists of our time, how do we interpret their resistance to accepting this testimony? Do we conclude that physicists in the 21st century lacked mental flexibility? Were not open to new ideas? Perhaps they were motivated by non-scientific considerations, a gang of narrow-minded "Einsteinists" aligning themselves to the line dictated by tradition and authority?

Let's hope that the refusing scientists of the present will be treated more fairly. Their refusal to abandon seemingly logical conclusions, even though these conclusions were ultimately proven to be incorrect (in our scenario), is scientifically acceptable and not a sign of a bow-necked prejudice.

Such stories are not uncommon in the history of science. Astronomers in the 19th century, who assumed that the Milky Way galaxy was the entire universe, examined the first images of the Andromeda galaxy and believed, rightly so, that they were looking at a single star surrounded by a nascent solar system, and not, as we know today, a distant collection of about a trillion stars. Similarly, Einstein was sure that the universe was static, so he introduced a cosmological constant in his equations to keep it that way. Both assumptions made sense. Both were wrong. And as David Kaiser of the Massachusetts Institute of Technology (MIT) and Angela N. H. Krieger of Princeton University demonstrated above these pages in the October 2012 issue, it is possible to make mistakes and still be of great benefit. And everything always seems clearer in retrospect.

In the matter of the fast neutrino particles we already have a view from the future to the past. Another famous story, whose legacy we already know, is that of Nicolaus Copernicus and his heliocentric theory. He claimed that the earth rotates on its axis in a diurnal cycle and orbits the sun every year, a theory we all accept today. The Copernican system challenged the old belief, formulated by Ptolemy in the second century AD in his "Great Book", the Almagest, according to which the sun, moon and stars revolve around the earth, which is fixed in its place at the center of the universe.

Copernicus proposed his revolutionary ideas in his book "On the Motion of the Heavenly Bodies", which many scientists of the time read, admired, commented on and used to improve their astronomical predictions. However, even by the year 1600, 57 years later, no more than a dozen serious astronomers had given up the belief that the earth was fixed in its place. Most scientists continued to favor the geocentric theory, which suited common sense. Even today, when we talk about the rising and setting sun, we sound like those who support it.

Sometimes this cosmological "planetary" is presented as a prejudice and it is claimed that it was disproved by Galileo in 1609, when he built a telescope and began using it to observe the stars, the moon and the planets. Both things are not true. Long after 1609 astronomers still had compelling scientific reasons to doubt Copernicus's claims. This is an impressive demonstration of good reasons for scholars' resistance to revolutionary ideas—even ideas that turn out to be spectacularly correct.

Brahe's new cosmology

The Danish astronomer Tycho Brahe has kindly created a well-spring and powerful source of doubt. In 1588 he proposed a new type of geometric system [see figure on the right]. His "geo-heliocentric" cosmology had two advantages that supported it: it fit deep intuitions about the way the world seemed to behave and fit the information available at the time, and it did so better than the Copernican system.

Braha was a man above his level. He ran a research program in a castle-like observatory, managed a research budget the size of a NASA research budget, and was equipped with the finest instruments and the best research assistants money could buy. Brahe's information about Mars was used by Johannes Kepler, one of his research assistants, when he discovered the elliptical shape of the planets' motion. Evan Gingrich, a historian at Harvard University, often demonstrates the importance of Brahe through the collection of all astronomical information since antiquity compiled and edited by Albert Curtius in the 17th century: most of the astronomical information of two thousand years came from Brahe.

This astronomer, who had supreme achievements, was very impressed by the elegance of the Copernican system. However certain aspects of it bothered him. One thing was the lack of a physical explanation for the movement of the earth. (Brah lived more than a century before the invention of Newtonian physics provided just this explanation.) The dimensions of the earth were reasonably known, and the weight of a sphere made of rocks and dirt thousands of kilometers in diameter was clearly enormous. What could move such a body around the sun? After all, even pulling a loaded cart down the street is very difficult.

In contrast, it is easy to explain the movement of celestial bodies such as stars and planets. Since the time of Aristotle, astronomers have assumed that heavenly bodies are made of ethereal matter that is not found on earth. This material has a natural tendency to move in a rapid circular motion, just as a cart has a natural tendency to stop if it is not pulled vigorously. Barha said that the Copernican system "expertly and completely bypasses all that is unnecessary and jarring in Ptolemy's system... and yet attributes to the earth, this clumsy and lazy body that is not suitable for movement, movement as fast as that of the heavenly torches." In this respect, the ancient astronomers had something in common with the modern astronomers, that in order to explain what they see, they assume today that most of the universe consists of "dark matter" or "dark energy" that is unlike anything we know.

Another thing that bothered Brahe was the stars in the Copernican system. Ptolemy said that the number of the stars is "infinitely great" because we cannot discern the daily shift (parallax), that is, it is impossible to discern the difference in their positions or appearance caused by changes in the viewing angles or distances of an observer on Earth as the stars move from one horizon to the sky and to The other horizon. The conclusion from this observation is that the diameter of the earth is nothing compared to the distance of the stars; The land is "like a point," wrote Ptolemy.

However, Copernicus knew that we would not even be able to notice the shift annual: Changes in the relative positions of the stars caused by the movement of the earth in its orbit around the sun. If the earth does revolve around the sun, the absence of an annual shift means that the diameter of its orbit (Copernicus called it in Latin magnus orbit, the great orbit) itself is zero, "as a point" compared to the interstellar distances. The dimensions of the universe become something that is hard to believe, "infinitely large".

Moreover, as Brahe well knew, Copernicus' proposal had far-reaching implications not only in terms of the dimensions of the universe But also Regarding the dimensions of each and every star. When we look up into the night sky, each star appears to have a fixed diameter. These diameters were measured by both Ptolemy and Braha. We now know that the distant stars are, practically speaking, points of light, and the measurements of their apparent diameter are an error caused by the passage of light waves through a circular opening, such as that of a telescope or the pupil of the eye.

But at that time astronomers knew nothing about the wave nature of light. Brahe used simple geometry to calculate the diameters of the stars. According to this calculation, if the stars are at Copernican distances, their diameter will be of the order of The big track. The smallest star will dwarf even the sun, as a grapefruit dwarfs the period at the end of this sentence. Believing even that was too hard to bear and Braha said that such huge stars were absurd. According to the historian Albert van Helden, "Brah's logic was without any flaw; His measurements were perfect. Every Copernican had to accept his claims."

When the Copernican theory was confronted with physical evidence that seemed irrefutable, they preferred not to give it up and had to turn to the heavenly Almighty. "It cannot be argued that these things, which mass types see as absurd at first glance, are indeed absurd, because the heavenly reason and majesty tower above their understanding." So wrote the Copernican Christoph Rothman in a letter to Brahe. "Be the expanses of the universe and the dimensions of the stars as great as you desire, they will still bear no match for the infinite creator. But it makes sense that the bigger the king, the bigger and bigger the palace is for his majesty. So what is the size of the palace that you think is suitable for God?"

Brahe, who was not persuaded by such reasoning, proposed his system: the sun, the moon and the stars revolve around the earth, which does not move, as in Ptolemy's system, while the planets move around the sun, as in the Copernican system [see box on page 75]. Breha's system preserved the advantages of geocentrism. The earth does not move in this system, thus avoiding the need to explain the movement of this clumsy and lazy body. Also, the disadvantage of an annual shift is avoided, the explanation of which requires the existence of huge and distant stars. The stars in Brahe's system rested just beyond the planets and were of reasonable size. And yet, as far as the planets were concerned, Brahe's system and Copernicus' system were mathematically identical. And so Brahe's system also preserved the mathematical elegance of the Copernican system, which in Brahe's opinion bypassed everything that was unnecessary or jarring in Ptolemy's system.

When Galileo began observing the heavens with his telescope, he made some findings that directly contradicted Ptolemy's ancient cosmology. He saw that Jupiter had moons, thus proving that the universe could carry within it more than one center of motion. He also observed the appearances of Venus and showed that this planet revolved around the Sun. However, these findings did not lead to the understanding that the Earth revolves around the Sun, as they were consistent with Braha's system.

A 200-year dispute

In the middle of the 17th century, long after the deaths of pioneers such as Copernicus, Brahe and Galileo, an Italian astronomer named Giovanni Battista Riccioli published an encyclopedic assessment of cosmological possibilities that he called (following Ptolemy's great work) the Almagest Novum. Ricioli considered various arguments for and against the Copernican system, which dealt with astronomical, physical and religious issues. But he stated that two arguments tipped the scales against Copernicus. Both were based on scientific objections. Both stemmed from Breha's ideas. Not one of them received an answer close to its publication, but only a few hundred years later.

One argument was based on the inability to notice certain phenomena that a rotating planet, in Riccioli's opinion, was have to create in its effect on projectiles and falling bodies. Brahe believed that a rotating earth had to deflect a projectile from a straight line trajectory. Such sets were not observed until the 19th century, when French scientist Gaspard Gustave de Coriolis developed a full mathematical description of such effects.

Another argument was the one formulated by Brahe regarding the dimensions of a star and updated by Riccioli through telescopic observations. (Brahe worked without a telescope.) After devising the Dire process for measuring the diameters of stars, he found that the stars appeared smaller than Brahe's estimates. However, the telescope increased the sensitivity to the annual shift, which they had not yet been able to detect, thus implying that the distances of the stars must be much greater than Brahe's assumptions. Hence the stars must have huge dimensions, as Braha claimed.

Riccioli complained that Copernicus appealed to the heavenly Almighty to circumvent this scientific problem. Riccioli, who was a Jesuit priest, could not deny the power of God. But he rejected this approach saying: "Even if this fraud cannot be refuted, it cannot satisfy... the cautious person."

Acceptance of the Copernican system was delayed by the lack of conclusive scientific evidence to support the almost unbelievable claims about the dimensions of the universe and the size of the stars. In 1674, Robert Hooke, curator of experiments at the British Royal Society, admitted that "Whether the earth moves or stands still, it has been a problem that has exercised the minds and reason of the best modern astronomers and philosophers since Copernicus revived it. Despite this, there is not one of them who has found clear evidence one way or the other."

In Hooke's time, a growing majority of scientists accepted Copernicanism, although to some extent they did so in the face of scientific difficulties. No one had convincingly reported an annual stellar shift until Friedrich Bessel in 1838. Around the same time, George Airy created for the first time the complete theoretical explanation for the fact that the diameter of stars appears larger than reality, and Ferdinand Reich was able to notice for the first time the shift caused by falling bodies due to the rotation of the Earth. Also, of course, Isaac Newton's physics, which did not fit Brahe's system, long ago provided an explanation for the ability of Brahe's "clumsy and lazy" Earth to move.

However, in the earlier days of Galileo and Riccioli, there was a fairly respectable, coherent, observational science on the side of the opponents of Copernicanism. In the end, they were proven wrong, but that doesn't mean they were bad scientists. In fact, rigorous refutation of strong arguments was and still is part of the challenge, and the pleasure, of doing science.

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in brief

Copernicus' revolutionary theory according to which the earth moves around the sun became according to him a treasure of scientific and religious wisdom collected over more than a thousand years.

Most scientists refused for decades to accept this theory - even after Galileo's historic telescopic observation.

Their objections were not merely religious. Observational evidence supported Tycho Brahe's competing geo-heliocentric cosmology.

About the authors

Dennis Danielson is a professor of English at the University of British Columbia who studies the cultural significance of the Copernican revolution. He recently served as visiting fellow in the Department of History of Science at the Ludwig Maximilian University in Munich.

Christopher M. Graney is a professor of physics and astronomy at Louisville, Kentucky Community Technical College. He and his wife, Christina, translate astronomical writings from Latin.

More on the subject

Measuring the Universe: Cosmic Dimensions from Aristarchus to Halley. Albert Van Helden. University of Chicago Press, 1985.

The Telescope against Copernicus: Star Observations by Riccioli Supporting a Geocentric Universe. Christopher M. Graney in Journal for the History of Astronomy, Vol. 41, no. 4, pages 453–467; November 2010.

Ancestors of Apollo. Dennis Danielson in American Scientist, Vol. 99, no. 1, pages 136–143; March–April 2011.

Stars as the Armies of God: Lansbergen's Incorporation of Tycho Brahe's Star-Size Argument into the Copernican Theory. Christopher M. Graney in Journal for the History of Astronomy, Vol. 44, no. 2, pages 165–172; May 2013.

The article was published with the permission of Scientific American Israel