Three Paradigm Shifts About Rocks: Ridicules Which Turned Into Cherished Scientific Truths
John Lennon’s song `Imagine’ ends with the words: “I hope someday you’ll join us/And the world will live as one”. In fact, science tells us that this is not a fantasy and the world did live as one for early dinosaurs. Going back in time by just 5% of the Earth’s history, we could have traveled on land between America, Europe, Africa, Asia, Australia and Antarctica. The scientist who suggested this idea publicly 112 years ago, was ridiculed for forty years and died in 1930, two decades before his idea was recognized as true.
Alfred Wegener, born in Berlin in 1880, was not a geologist. He studied physics, meteorology and astronomy, and his thermodynamics teacher was Max Planck. In 1904, Wegener completed his doctoral dissertation in astronomy on the application of computational methods to astronomical data. In 1905, he joined the Royal Prussian Aeronautical Observatory, where he used kites and balloons to study the upper atmosphere. His work in meteorology earned him an invitation in 1906 to join an expedition to Greenland’s unmapped northeast coast. Upon his return in 1908, he became a lecturer on meteorology, astronomy and “astronomic-geographic position-fitting for explorers,” at the University of Marburg. His lectures gained popularity among students and professors because of his exceptional ability to explain complex topics and difficult concepts in simple terms intuitively and without loss of accuracy. The physics professor Hans Benndorf, wrote: “He would often, after a long pause for reflection, say `I believe such and such’ and most times he was right, as we would establish several days later after rigorous analysis.” At age 30, Wegener collected his lectures into a meteorology book in 1911, titled `The Thermodynamics of the Atmosphere,’ which soon became a standard textbook throughout Germany. After reading the book, the distinguished Russian climatologist Alexander Woeikoff wrote that a new star had risen in meteorology.
Following the completion of his first book, Wegener noticed that different continents on Earth fit together like a jigsaw puzzle, with the continental shelf of the Americas fitting Africa and Europe, and Antarctica, Australia, India and Madagascar fitting the tip of South Africa. After reading a paper in 1911 which criticized the prevalent hypothesis that a bridge of land used to connect Europe and America, he decided to advocate the idea of a continental drift. Wegener was not the first scientist to notice the jigsaw-puzzle-fit of Brazil with the west coast of Africa. However, his predecessors’ ideas only came to Wegener’s attention after he had formulated his thesis.
Wegener’s future father-in-law, the well-known meteorologist Wladimir Köppen, warned Wegener, in vain, not to delve into matters of geology because he was a meteorologist and therefore an outsider. Ignoring this well-intended advice, Wegener gave a lecture on January 6, 1912, titled: `Development of the Main Features of the Earth’s Crust (Continents and Oceans) on a Geo-Physical Base’, at the annual general meeting of the Geologische Vereinigung in Frankfurt, thereby making his hypothesis public for the first time. Shortly afterwards, Wegener completed two manuscripts on the subject.
Later, Wegener reasoned correctly that both sides of the Atlantic Ocean share the same rock type, geological structures and fossil plants. He combined evidence from various fields to theorize that Earth’s continents were once part of an enormous, single landmass. This primal supercontinent was later coined `Pangaea,’ a name which means `All land’ in Greek. However, Wegener’s revolutionary thesis also contained some initial errors and omissions. One of the errors was his assumption “that the salic crust once covered the entire surface of the whole earth,” and his main omission involved identifying the actual driver of the proposed continental drift.
Wegener’s hypothesis was met with ridicule and skepticism from geologists, who viewed him as an outsider and resisted change to their traditional views. The distinguished Harvard scientist Andy Knoll states in his book `A Brief History of Earth’: “Wegener summarized his ideas in a 1915 book, `The Origins of Continents and Oceans’. To say the response to his hypothesis was “mixed” understates the vigor of the debate that followed. Prominent North American and European Earth scientists, retrospectively labeled “fixists,” rejected Wegener’s ideas because they couldn’t conceive of a mechanism by which continents could flow across ocean basins… Of course, the fixists held prestigious professorships in European and North American universities, trumping those poor southern souls who simply looked at the rocks.”
The German geologist Max Semper wrote in 1917 a critique of Wegener’s theory, ending with ridicule and mockery of Wegener as an outsider: “… so one can only ask for the necessary distance to be maintained and the request to stop honoring geology in the future, but to visit specialist areas that have so far forgotten to write above their gate: “Oh holy Saint Florian, spare this house, set others on fire!”
Wegener died in 1930. In 1943, the most influential paleontologist of the 20th century, George Gaylord Simpson, wrote a long paper that strongly criticized Wegener’s theory and argued that similarities of plants and animals between the continents could be explained by fixed land masses which over time were connected and disconnected by periodic flooding.
In the early 1950s, new evidence on prehistoric magnetic fields recorded in rocks supported Wegener’s theory. A decade later, geological discoveries of seafloor spreading, seismic zones associated with down-going slabs in subduction zones and maps of ocean floors, established a paradigm shift to plate tectonics with Wegener as its founding father. Today, it is recognized that continents rest on massive slabs of rock called tectonic plates, which are moving and interacting. The North American and Eurasian tectonic plates are separated by the Mid-Atlantic Ridge at the rate of about 2.5 centimeters per year. Continental landmass is ripping apart along rift valleys. Africa, for example, is expected to split along the Great Rift Valley system, making a new Somali continent, with the Horn of Africa and Madagascar its largest landmasses. It is believed that several supercontinents have formed and broken up during the Earth’s history, including Pannotia — which formed about 600 million years ago, and Rodinia — which existed more than a billion years ago.
This was not the first paradigm shift regarding rocks. Prior to the 18th Century, the notion that rocks might fall from the sky was ridiculed. The paradigm shift in this context was triggered by testimonies from residents of the French town of L’Aigle, who witnessed more than 3,000 stones falling from the sky on April 26th, 1803.
Just a decade before this meteor shower, a physicist named Ernst Chladni published in 1794 a book suggesting that meteorites came from space. The historian Ursula Marvin writes that Chladni was hesitant to publish, because he knew that he was “gainsaying 2000 years of wisdom, inherited from Aristotle and confirmed by Isaac Newton, that no small bodies exist in space beyond the Moon.” Reaction to Chladni’s book ranged from skepticism to ridicule. Today, Chladni is regarded as the founding father of meteoritics
A few months after the meteorites fell in L’Aigle, the physicist Jean-Baptise Biot traveled there for nine days to analyze the event. Biot was a strong believer in the power of science communication, and his literary report on the L’Aigle meteor fall was echoed in popular media as well as in the scientific community, amplifying his conclusion that “stones fell around L’Aigle.” Because his report relied on evidence from many independent witnesses, it raised wide public interest.
The researcher Matthieu Gounelle notes that “Biot distinguished two kinds of evidence of an extraterrestrial origin of the stones.” First, the kind of stone that had fallen was totally different than anything else available locally — but it was similar to the stone from the Barbotan meteor fall in 1790. Biot wrote: “The foundries, the factories, the mines of the surroundings I have visited, have nothing in their products, nor in their slag that have with these substances any relation.” Second, unlike earlier meteor falls, there were multiple witnesses “who saw ‘a rain of stones thrown by the meteor,’” Gounelle writes. The witnesses came from different backgrounds, and so Biot reasoned that it would be ridiculous to think they had all conspired to report on something that had not actually taken place.
Fast forward to the third paradigm-shift about rocks that we might be witnessing right now. On January 8, 2014, sensors aboard U.S. Government satellites detected a fast-moving fireball from a meteor. The data was shown to imply in a paper I wrote with my former student Amir Siraj, that the meteor was interstellar in origin based on its velocity. Even though the velocity measurement was double-checked by the U.S. Space Command, the interstellar origin was repeatedly ridiculed by meteor experts who published a paper claiming that the data must be wrong and that this meteor is from the solar system. In June 2023, I led an expedition to the Pacific Ocean site of the meteor’s fireball, which resulted in a paper detailing our findings of material of unusual chemical composition. The critics argued that this material is coal ash. We analyzed 55 elements from the periodic table and published a research note demonstrating that it is not coal ash. At the same time, I also published a paper with my postdoc Morgan MacLeod, suggesting a natural astrophysical origin for the properties of this interstellar meteor. The critics ignored this explanation altogether and subsequently argued that we went to the wrong place, because if they ignore the U.S. Government data, which they refuse to believe, the localization uncertainties are too large. I wrote a response paper that our expedition surveyed the location identified by the U.S. Space Command based on the fireball light, which is more accurate than other data sets.
As the philosopher George Santayana said: “Those who cannot remember the past are condemned to repeat it.”
ABOUT THE AUTHOR
Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. His new book, titled “Interstellar”, was published in August 2023.
