In spite of the fact that Kelvin’s calculation of the age of the Earth was a blunder, I continue to regard it as absolutely brilliant. Kelvin had completely transformed geochronology from vague speculation into an actual science, based on the laws of physics. His pioneering work opened a vital dialogue between geologists and physicists—an exchange that continued until the discrepancy was resolved. At the same time, Kelvin’s parallel work on the age of the Sun pointed clearly to the need to identify new sources of energy.

Charles Darwin himself was very aware of the importance of eliminating the obstacle to his theory presented by Kelvin’s calculations. In his final revision of The Origin, Darwin wrote:

With respect to the lapse of time not having been sufficient since our planet was consolidated for the assumed amount of organic change, and this objection, as urged by Sir William Thomson [Kelvin], is probably one of the gravest as yet advanced, I can only say, firstly, that we do not know at what rate species change as measured by years, and secondly, that many philosophers are not as yet willing to admit that we know enough of the constitution of the universe and of the interior of our globe to speculate with safety on its past duration.

Darwin did not live to see how Perry’s idea of a convective Earth, the discovery of radioactivity, and the understanding of nuclear fusion reactions in stellar interiors swept away all of Kelvin’s age limits. The fact remains, however, that it was Kelvin’s calculation—erroneous though it was—that identified the problem that had to be solved.

From our perspective as humans, one of the key benefits of the Earth having enjoyed 4.5 billion years of energy from the Sun has been the emergence of complex life on Earth. But the building blocks of all life-forms are cells, and by the 1880s, scientists using ever-improving optics to examine the internal structure of cells coined the term “chromosome” for the stringy bodies found in the cell’s nucleus. Soon thereafter, Mendel’s work on genes (“factors,” as he called them) was rediscovered, and pioneering work by Thomas Hunt Morgan and his students at Columbia University allowed for mapping out the positions of genes along chromosomes. In 1944 a particular molecule—DNA—located on chromosomes, started to gain attention. Before long, biologists realized that all cells receive their instructions not from proteins but from two molecules, DNA and RNA nucleic acids. Biologists identified the DNA molecules as the bosses of all the frenzied activity in cells and the molecules that know how to make identical copies of themselves. RNA (ribonucleic acid) molecules were shown to be in charge of transmitting the instructions issued by DNA molecules to the rest of the cell. Together, these molecules contain all the information needed to make an apple tree, a snake, a woman, or a man function. The discoveries of the molecular structures of proteins and of DNA are two of the most fascinating stories in the search for the origin and workings of life. Yet these discoveries, too, involved major blunders.