Mario Livio Ph.D.


On Scientific Blunders

Blunders are part and parcel of progress in science.

Posted Aug 21, 2020

Why would anyone want to talk about mistakes made by famous scientists? There is one simple reason and one that is more profound. The simple reason is that it is sometimes comforting for the rest of us to discover that even the greatest luminaries have made some serious mistakes. The second reason is that we have to realize that mistakes are part and parcel of the scientific process. I will discuss this point further towards the end of this piece.

In this note, I will only briefly describe and analyze two major blunders, one committed by the legendary physicist and astronomer Galileo Galilei, and the other by chemist and Nobel Laureate Linus Pauling.

Galileo made his blunder in the context of his theory of ocean tides. The idea for that theory must have sprung from his observations of water sloshing back and forth at the bottom of the barge that took him regularly from Padua (where he lived and worked for 18 years) to Venice. Galileo noticed that when the barge was speeding up, the water piled up at the back, and when it slowed down, it accumulated at the front. To him, this to-and-fro motion of the water resembled the tides.

At the time, Galileo was desperate to provide a proof for the Earth’s motion around the Sun. His astronomical observations had already all but destroyed the old geocentric model, in which the Sun and all the other planets were assumed to revolve around the Earth. However, there was still no direct proof that the Earth itself was moving. Connecting the tides to accelerating and decelerating motion gave him a new idea.

In January 1616, he suggested that the speeding up could occur when the diurnal spin of the Earth around its axis was in the same direction as the Earth’s motion around the Sun (which happens once a day at a given point on the Earth’s surface). The deceleration, according to this scheme, was supposed to occur (also once a day) when the velocity associated with the spin was in opposite direction to that of the orbital motion. Galileo thought that while the continents would not respond to the combination of these two motions, the oceans would slosh. He, therefore, believed that he found an elegant way to connect the Earth’s revolution around the Sun with the phenomenon of tides, “taking the former as the cause of the latter, and the latter as a sign of and an argument for the former.” Unfortunately, elegant or not, Galileo’s theory for the tides was completely wrong!

The tides are produced by the combined actions of the forces of gravity of the Moon and the Sun, as Isaac Newton eventually showed.

How did a great scientist such as Galileo make such a serious blunder? It seems that at least two elements combined in his mind to lead him astray. One was an engrained bias and the other a feeling of pressure. The bias had to do with Galileo’s general disbelief in the action of unseen forces (such as gravity) acting across space. Consequently, he erroneously ignored the fact that the Flemish mathematician Simon Stevin and the German astronomer Johannes Kepler had already suggested that the tides may be associated with the attraction of the Moon. The pressure he felt to produce a proof for the Earth’s motion had to do with the fact that just a month after Galileo outlined his theory, theologian consultants to the Catholic Church’s Holy Office issued a statement declaring that the proposition of the Sun being at the center of the solar system “is foolish and absurd in philosophy, and formally heretical since it explicitly contradicts in many places the sense of Holy Scripture.” Biases and pressure produce a recipe for blunders.

The second blunder I want to discuss concerns Linus Pauling’s flawed model for the structure of DNA. Pauling started to work on DNA at the end of November 1952. What was known at the time was that DNA consisted of three components: four bases (labeled for short “A," “T," “C," and “G”), sugars, and phosphate groups. It was also known that in any section of DNA the number of A units was equal to the number of T units, and the number of C units was equal to the number of G units. These relations were known as Chargaff’s rules (after chemist Erwin Chargaff).

On the last day of 1952, after having worked on it only a little over a month, Pauling and his assistant already submitted a paper in which they proposed a model for the structure for DNA. Pauling’s model had a three-stranded helical architecture, in which the phosphate groups were in the middle, with the sugars surrounding them and the bases on the outside, projecting radially outward. This triple helix was supposed to be held together by hydrogen bonds between phosphate groups of different strands.

There were numerous problems with this model. First, the phosphate groups are negatively charged, and cramming all of them at the center, they would have electrically repelled each other, literally driving the entire molecule apart. Second, the model violated the Chargaff rules. Finally, DNA is a nucleic acid, meaning that in water, it should have released its hydrogen. This was impossible in Pauling’s model since hydrogen bonds were holding the molecule together.

When we examine the causes for Pauling’s blunder, a few puzzling questions arise. Why was he in such a rush to publish [he had spent 13 years on his previous model for certain proteins]? Why didn’t he care about violating the Chargaff rules, or the acidity of DNA? We shall never know the precise answers to these questions, but there is no doubt that he operated with data he knew to be inferior to that obtained by his competitors at Cambridge and London. He therefore didn’t want to get scooped. There is also the impression that he wasn’t altogether convinced that DNA (rather than the proteins) was really “the secret of life.” Even his personal dislike for Chargaff may have played a role. Perhaps most important, he was a victim of his own previous success. He took a long time to publish his model for proteins only to discover that his original hunch had been correct. He thought that the same will happen again and that the remaining issues would turn out to be insignificant details.

The key lesson we should take from these two stories (and many similar ones) is the following. Unlike the way it is often described in textbooks, the road to discovery is rarely a straight line from A to B. It is usually a zigzag path, with many false starts and blind alleys. While we should discourage mistakes that happen because of sloppiness or lack of experience (the inexperienced should seek guidance), if we want to encourage “outside the box” thinking, we should realize that blunders are inevitable. Breakthroughs can come from thinking in unconventional, out of the mainstream ways. Blunders that result from such attempts at originality are the ones I dub “brilliant blunders,” and those should be appreciated.


Livio, M. (2020). Galileo and the Science Deniers. New York: Simon & Schuster

Livio, M. (2013). Brilliant Blunders: From Darwin to Einstein. New York: Simon & Schuster