In 1543 two books appeared that would change how Europeans understood the universe and the human body. Both depended on printing in ways that manuscript culture could not match. Historians still debate how much print caused the Scientific Revolution, but few doubt that it shaped it.

Copernicus and the heavens

The Polish astronomer Nicolaus Copernicus argued that the Earth and the other planets move around the Sun, rather than the Sun and planets moving around a stationary Earth. His book, On the Revolutions of the Heavenly Spheres, was printed in Nuremberg in 1543, the year of his death. Its mathematical tables and diagrams had to be reproduced exactly; in manuscript, they would have been corrupted by copying errors. In print, astronomers across Europe could check the same calculations and compare them with their own observations.

Vesalius and the body

That same year, the anatomist Andreas Vesalius, teaching at the University of Padua, published On the Fabric of the Human Body in Basel. Based on his own dissections, it corrected many errors in the ancient medical writer Galen, whose works had dominated medicine for over a thousand years. Its greatest strength was its detailed woodcut illustrations, showing bones, muscles and organs with unprecedented accuracy. Because the illustrations were printed from the same blocks, every reader saw exactly the same images. A hand-copied drawing, by contrast, degraded with each copy.

Fixity and standardization

In an influential 1979 study, The Printing Press as an Agent of Change, the historian Elizabeth Eisenstein argued that print transformed knowledge in several ways. First, standardization: identical copies allowed scholars in different places to work with the same texts, tables and maps. Second, preservation: with many copies in circulation, knowledge was less likely to be lost. Third, error correction: readers could send corrections to printers, and later editions could fix mistakes, so knowledge could accumulate and improve over time rather than decay.

The critics

Other historians have challenged Eisenstein's picture. In The Nature of the Book (1998), the historian Adrian Johns argued that early printed books were often far from reliable. Printers pirated each other's books, rushed out editions full of errors, and sometimes altered texts. Readers had to learn which printers and editions to trust. On this view, reliability was not automatic; it was built over time through reputation, regulation and scholarly communities. Many historians now combine the two views: print made fixed, shared texts possible, but people had to work to make them trustworthy.

Networks of scholars

Print also helped scientists form communities. The Danish astronomer Tycho Brahe set up his own printing press at his observatory so he could publish his observations and control their accuracy. Scholars across Europe exchanged books and letters, building on each other's work. In 1665, two of the first scientific journals appeared: the Journal des sçavans in Paris and the Philosophical Transactions of the Royal Society in London. Journals allowed new findings to be shared quickly and openly, with the name of the discoverer attached, which encouraged scientists to publish rather than keep their methods secret.

Galileo and the danger of print

Print could also bring danger. In 1610 the Italian scientist Galileo Galilei published The Starry Messenger, describing what he had seen through his telescope, including moons orbiting Jupiter. In 1632 he published a dialogue that, despite his assurances, plainly favored the Copernican view. Because it was printed in Italian and widely read, the Roman Inquisition saw it as a public threat. In 1633 Galileo was tried, forced to recant and sentenced to house arrest for the rest of his life. His book was placed on the Index. It was still read: copies smuggled to Protestant countries spread his ideas.

Worked example: fixing an error

Imagine an astronomer in 1560 notices that a table of planetary positions in a printed book contains a mistake. Compare what happens in manuscript and in print culture.

• Manuscript. She corrects her own copy. Other copies, in other cities, keep the error, and some copyists add new mistakes. Her correction may never reach anyone else.
• Print. She writes to the printer or publishes a note. The next edition includes a corrected table. Readers everywhere can see the correction and check it.
• But beware. A pirate printer might reprint the old, uncorrected edition because it is cheaper. Readers must know which edition to trust.

The example shows both sides of the debate. Print made it possible for knowledge to be corrected in public, which is the heart of science. But that possibility depended on people: printers who took care, readers who checked, and communities that kept track of which sources were reliable. The same is true of information today. Technology can spread corrections or errors equally fast, and trust depends on the habits of those who use it.