This week’s entry: Superseded scientific theories
What it’s about: Scientific inquiry is often a messy process. For every theory that becomes accepted—gravity, evolution, climate change, Han shooting first—there’s a theory that doesn’t pan out. Some are flat-out wrong, and some are merely incomplete pictures put into clearer focus by later generations of scientists.
Strangest fact: Our ancestors were more than willing to judge a book by its cover. Physiognomy was a theory that personality was related to appearance. The theory may have originated with Pythagoras, who once rejected a student who looked like a shady character. Leonardo Da Vinci dismissed the theory in the 1500s, and Henry VIII outlawed the use of physiognomy as a form of fortune telling. But it came back into vogue in the 1700s and remained popular for another century or so. Even as late as the early 20th century, adherents included Glinda The Good Witch of the South (in the book she is from the South; in the film, the North), who believed “only bad witches are ugly.”
Biggest controversy: While the scientific community is generally happy to embrace a more accurate theory and discard one demonstrated to be false, the lay public isn’t always so eager. Even in modern times, there still exists a Flat Earth Society, willfully ignorant of the findings of everyone from Magellan to Neil Armstrong. While schoolchildren were long taught that medieval Europeans believed the Earth to be flat until they were proven wrong by Columbus, in fact both Europeans and Indians found the world to be round in around the 4th century, and sailors long before Columbus’ time knew the horizon curves and that the earth casts a round shadow on the moon. Despite this, after more than a millennia and a half, a small but dedicated group of Flat Earthers still claim the world is disc-shaped, with Antarctica a wall of ice that surrounds the edges—never mind the vast distances this model creates between landmasses in the Southern Hemisphere. So take heart: It will only be another 1,400 years or so before climate change deniers are down to a small handful of kooks.
Thing we were happiest to learn: Louis Pasteur did more than just make your milk safe. He also debunked the theory of spontaneous generation, the theory that some forms of life weren’t born or hatched, but instead appeared from inanimate matter. According to this theory, fleas came from dust, maggots came from dead flesh, and tapeworms and other parasites simply appeared within their hosts. No less an authority than Aristotle believed many insects “come from putrefying earth or vegetable matter.” The 17th century scientist Jan Baptist Van Helmont made legitimate advances in chemistry, but also attempted to grow mice using wheat and a piece of dirty cloth. Finally, in 1859, Pasteur put spontaneous generation to rest, when he put meat broth—thought to generate its own parasites—into a long-necked flask that didn’t allow particles to easily enter. The broth remained uncontaminated. When he adjusted the neck so the broth was more exposed to the air, it became cloudy. While he still had a few doubters, most scientists considered the matter settled.
Thing we were unhappiest to learn: Back in the old days, there were even more ways to supposedly screw up your kids. One such was maternal impression, the idea that strongly negative thoughts by a pregnant woman could affect her unborn child. People used this theory to explain away birth defects, even as recently as the late 1800s, when Joseph Merrick, known to this day as the Elephant Man, believed his deformities were the result of his mother being scared by an elephant while he was in utero, and this explanation was widely accepted. Around that same time, the ideas of Gregor Mendel, the father of genetics, became accepted by the scientific community, and by the early 20th century had displaced maternal impression for good.
Also noteworthy: A whole periodic table could be created out of substances once thought to exist that don’t. Heat was once thought to exist as a fluid called caloric, and before that fire was thought to be created by an element in the air called phlogiston. Light supposedly shone in the form of luminiferous aether. And while the four classical elements, fire, earth, water, and air, do exist, they do not comprise all matter, as ancient societies including Greece, Babylon, India, and Japan each believed. Likewise, human health isn’t determined by the balance of the four humors, as the ancient Greeks and Romans believed.
Further down the wormhole: One wrong theory may eventually become right. Explorers in the 16th century sought an open polar sea, an ice-free expanse of the Arctic Ocean that would allow sailors to travel north of North America. While explorers continued to search for such a sea until the late 19th century, such a body of water might exist by the end of the 21st thanks to climate change. While humanity has not been terribly successful at reducing carbon emissions, science is developing multiple strategies for carbon dioxide removal, removing some of the greenhouse gas from the atmosphere, in an attempt to set the climate back into balance. We’ll take a look at how that might be done next week.