46 Fun Facts About Nicolaus Copernicus

Why did Copernicus do all his observing with the naked eye?

No telescopes existed. The first appeared about 65 years after his death, so Copernicus never saw the sights that later won his system support, such as the moons found circling Jupiter in 1610.

Which philosopher likened his own new theory of knowledge to Copernicus's change of viewpoint in astronomy?

Immanuel Kant. In 1787 he proposed that objects must conform to our knowledge, not the reverse, just as Copernicus had explained the turning sky by making the observer move.

In which city was Copernicus born in 1473?

Toruń. The trading town had passed from the Teutonic Knights to the Polish crown only seven years before, which is how a merchant's son there was born a subject of Poland's king.

What did Copernicus's father, also named Niklas, trade in as a merchant?

Copper. He sold it mostly in Danzig, and his death when Nicolaus was about ten left the boy's schooling and career in the hands of a well-connected uncle.

Which Italian friar, a champion of Copernicus's moving Earth, was burned at the stake in 1600?

Giordano Bruno. Historians still argue over which of his ideas condemned him, and the Church left Copernicus's own book untouched for another 16 years.

At which university did Copernicus begin his studies in 1491?

Kraków. He left without a degree, which was common then, but its courses in mathematics and astronomy had already set him buying books on the heavens.

Which reddish star did Copernicus watch slip behind the Moon at Bologna in 1497?

Aldebaran. It is his first recorded observation, made while he lodged with the Bologna astronomer Domenico Novara, and he was still citing it in his great book 46 years later.

In which subject did Copernicus receive his doctorate at Ferrara in 1503?

Canon law. He collected the degree from Ferrara, a university where he had never studied, and it was the only one he ever earned, for he never completed his medical course.

Which cathedral chapter gave Copernicus a seat in 1497 that he kept for the rest of his life?

Warmia. His uncle, the bishop there, arranged the seat, and its income kept Copernicus financially secure for life while he pursued astronomy in his spare time.

As a medical student, Copernicus would have been taught which subject, then thought essential for doctors?

Astrology. Physicians believed the stars shaped a patient's constitution and the right moment for a treatment, so the medical schools of Italy taught it as a matter of course.

Copernicus's first printed book, in 1509, was his Latin translation of letters written in which language?

Greek. The letters were by the Byzantine writer Theophylact Simocatta, he dedicated the little book to his uncle, and it was the only thing the great astronomer published himself until his masterpiece 34 years later.

Copernicus circulated a short handwritten outline of his theory before 1514, known today by which title?

Commentariolus. Copernicus never had it printed and let only a few handwritten copies pass among trusted colleagues, so the full text stayed unpublished for more than three centuries.

In which Baltic cathedral town did Copernicus settle around 1510 and make most of his observations?

Frombork. Its frequent fogs made it a poor place to watch the sky, yet he bought a tower in the cathedral walls and went on observing from the town for some thirty years.

Copernicus made few observations of his own and leaned heavily on the data of which ancient astronomer?

Ptolemy. Only a few dozen of Copernicus's own observations are on record, so the man who overturned Ptolemy's universe built much of his case on Ptolemy's own 1,400-year-old measurements.

When the Teutonic Knights attacked Olsztyn around 1520, Copernicus took charge of what?

The castle's defence. He was living in Olsztyn Castle as the cathedral chapter's administrator when the attack came, and the stronghold he organised held out against the Knights.

Which economic principle did Copernicus set out in an essay on coinage, decades before the man it is named for?

Gresham's law. Copernicus wrote that bad money drives out good while advising on a debased local coinage, and the idea took its present name only in the 19th century, in honour of the Tudor financier Thomas Gresham.

In 1536 a cardinal wrote from Rome urging Copernicus to do what?

Publish his new theory. Cardinal Nikolaus von Schönberg begged for a copy 'at the earliest possible moment', and Copernicus later thanked him by name in the book's dedication.

Which historian of science, who later made 'paradigm shift' famous, wrote The Copernican Revolution in 1957?

Thomas Kuhn. It was his first book, and working out how astronomers came round to Copernicus gave him ideas he built into The Structure of Scientific Revolutions five years later.

Rheticus, the young professor who sought out the Catholic cleric Copernicus in 1539, taught at which Protestant university?

Wittenberg. He arrived from the birthplace of the Reformation and stayed two years, yet Copernicus left his Protestant pupil unnamed when he dedicated the finished book to the pope.

In which city was De revolutionibus printed by Johannes Petreius in 1543?

Nuremberg. It was a leading centre of printing and Petreius its top printer, a long way from Copernicus's home on the Baltic, which is one reason so large and technical a book waited years for a press.

According to legend, what happened on the very day Copernicus died in May 1543?

He saw his printed book. The story goes that he woke from a stroke-induced coma to find the finished volume in his hands and then died, a tale one biographer says has the air of a saint's life.

Which reformer reportedly scoffed at dinner in 1539 that Copernicus wanted to turn astronomy upside down?

Martin Luther. He is said to have added that Joshua commanded the sun, not the earth, to stand still, in a remark noted down by a dinner guest four years before the book was even printed.

In 1838 Friedrich Bessel finally measured which effect, long demanded by critics as proof that the Earth moves?

A star's parallax. The tiny yearly shift of a nearby star against the background shows that the Earth is moving, and its apparent absence had been a leading objection to Copernicus for nearly 300 years.

Which ancient astronomer had proposed a Sun-centred system eighteen centuries before Copernicus?

Aristarchus of Samos. His own account is lost and the idea survives only in reports by later writers such as Archimedes, and Copernicus cut a mention of him from the final manuscript of his own work.

Which great observer admired Copernicus yet built a rival system that kept the Earth motionless?

Tycho Brahe. He admired Copernicus's mathematics but could not accept a moving Earth, so he devised a compromise in which the Sun, carrying the other planets with it, still circled a motionless Earth.

Owen Gingerich's census of early copies of Copernicus's book disproved which old jibe, later borrowed for his own title?

Nobody read it. The margins of copy after copy were crowded with their owners' handwritten notes, proof that astronomers had closely studied the book a popular writer had called unread.

The Church suspended Copernicus's book in 1616 during the affair of which scientist?

Galileo Galilei. His loud defence of Copernicus brought the decree, which suspended the book only until a few sentences were reworded to present the moving Earth as a hypothesis, not a fact.

Which 1851 experiment let the public watch the Earth turn, just as Copernicus had said it does?

Foucault's pendulum. The swinging weight slowly changed direction against the floor as the Earth rotated beneath it, the first simple, direct demonstration of the daily spin Copernicus had argued for.

Geometric tools in Copernicus's models, such as the Tusi couple, were first worked out by astronomers of which civilization?

The Islamic world. The astronomers of Maragheh and Damascus wrote in Arabic, which Copernicus could not read, and whether he reinvented their methods or learned them through some lost link is still unknown.

Copernicus rearranged the heavens but kept which ancient assumption, later overturned by Kepler?

Orbits are perfect circles. Insisting on uniform circular motion forced Copernicus to keep small epicycles, so his system was no simpler than the old one until Kepler swapped the circles for ellipses.

Which Renaissance ruler summoned Copernicus to Königsberg in 1541 to treat his sick counsellor?

Duke Albert of Prussia. Twenty years earlier he had been the enemy, the last grand master of the Teutonic Knights whose war reached Copernicus's own walls, and now he sent for him as a doctor.

How did forensic experts first link a skull found in 2005 to Copernicus?

A facial reconstruction. The skull was that of a man of about seventy, the age at which Copernicus died, and the face rebuilt from it pointed to him before any genetic test was run.

How was DNA from the skeleton found in 2005 finally matched to Copernicus?

Hairs in a book he owned. No relative's grave could be found to test against, so the match came from two hairs caught between the pages of an astronomy book he had used for years.

Copernicus ranked the planets by the time each takes to circle the Sun; which did he find slowest, at 30 years?

Saturn. With the Sun at the centre, the planets fell into order by the length of their years, from swift Mercury out to Saturn, tying them into one system for the first time.

The name copernicium for element 112 became official in 2010 on the anniversary of which event?

Copernicus's birth. The element's discoverers chose him partly because his picture of planets circling the Sun is echoed in the atom, with its electrons orbiting a nucleus.

The 'Copernican principle' of cosmology assumes that our place in the universe is what?

Nothing special. The principle stretches Copernicus's demotion of the Earth into a rule that no observer anywhere has a privileged view, an assumption cosmologists can test but never prove outright.

Poland honours Copernicus as its own, but which language did his family speak?

German. His merchant family spoke it in a town that owed loyalty to the Polish crown, and at university in Italy he signed into the 'German nation', the club for students whose mother tongue was German.

In Copernicus's theory, what makes a planet such as Mars seem to drift backwards in the sky for weeks?

The Earth overtaking it. Seen from a faster planet on an inner track, a slower outer one appears to slip backwards for a while, so Copernicus could call the looping an illusion of our own motion.

Which organisation named its Earth-observation satellite programme after Copernicus?

The European Union. The programme turns his gaze around: where Copernicus looked up to find the Earth's place among the planets, its Sentinel satellites look down to track our land, seas and climate.

At which Italian university did Copernicus study medicine from 1501 to 1503?

Padua. His chapter gave him two years' leave so that he could come home as its medical adviser, too short a time to finish the degree, yet he practised as a physician for the rest of his life.

In his dedication, Copernicus held up the Church Father Lactantius as a warning for having ridiculed which idea?

A round Earth. Lactantius was a learned Christian writer of the fourth century who still scoffed at a spherical world, and Copernicus used him to warn theologians off ruling on the heavens.

Copernicus's moving Earth left the physics of his day unable to explain what?

Falling objects. Aristotle had heavy things dropping toward the centre of the universe, so once the Earth was moved away from that centre, there was no saying why a stone should still fall to it.

In 1514 Copernicus was invited to advise a Church council in Rome on the reform of what?

The calendar. Julius Caesar's reckoning had drifted badly out of step with the Sun, throwing the date of Easter into doubt, and the invitation shows how far the reputation of a provincial churchman had spread.

How did Copernicus's pupil Rheticus treat the unauthorised preface in the copies of the book sent to him?

He crossed it out. Rheticus struck through the page with a great red X, and a bishop friend of Copernicus demanded a corrected reprint from the printer's city council, which refused.

What did Erasmus Reinhold call his 1551 astronomical compilation based on Copernicus's work?

They were sponsored by the Protestant Duke Albert, who had been Copernicus's military adversary during the Teutonic war.

Copernicus's system had six planets circling the Sun; which planet, unknown until 1781, is missing from it?

Uranus. It is so dim and slow that ancient skywatchers never recognised it as a planet, and the count stayed at six until William Herschel found it more than two centuries after Copernicus.