In our era, most people are pretty confident that when science is correctly applied, it should come up with plausible conclusions. The scientific method, after all, is a rigorous means of testing hypotheses. But there wasn’t always a scientific community with standards of evidence and peer review, and scientists of old were certainly working with less accurate, less technologically advanced tools. That’s why it’s forgivable–even understandable–why these ludicrous-sounding theories used to be espoused by the most eminent scientists:
Where do bugs come from? Today, everyone would say the answer is “from parent bugs of the same species.” Since this is how most animals are born, you’d be forgiven for assuming that people have always known this, just as they’ve always known where, say, sheep, birds, or humans come from. But since the ancients had apparently never seen two insects mating, but did see insect larvae in certain places, they drew some erroneous conclusions. Some examples: Maggots, and later flies, can be observed in the flesh of a dead horse. Therefore, when a horse dies it begins to turn into maggots which grow into flies. Sometimes, the sand is full of sand fleas. Therefore, grains of sand must occasionally come to life and become sand fleas at random. Aristotle thought this, said our ancestors, and how could someone as smart as Aristotle be wrong? Of course, with the advent of microscopes, scientists like Robert Hooke were able to prove that insects actually laid tiny eggs in these types of environments, and exposed spontaneous generation as the ridiculous idea it is.
Changes in the makeup of the Earth–the rise and fall of mountain ranges, forests becoming deserts and vice-versa, islands emerging from the sea floor–tend to take a long time without outside intervention. Thanks to tectonic plate theory, we know that the planet is in constant but slow flux. Continents move fractions of centimeters per year, but over millions of years drift far and wide. Concepts like these make up the “geological time scale,” which everyone who knows even a little about Earth science is familiar with. But scientists weren’t always so patient when it came to alterations to our very world. Indeed, the prevailing model once held that change could only come in moments of sudden and powerful disaster. This “catastrophism” theory was put forth during a time of other reactionary forces in science, when history was likewise held to be influenced by individual “Great Men” rather than socio-cultural or economic factors and many Christians thought the Bible was literally true. Hence, catastrophism was seen as neatly fitting a world where masculine, conquering heroes determined all and things like Noah’s flood and the fall of the Tower of Babel “had” to have truly happened. Nowadays, though, it’s known that catastrophism can account for only a tiny number of changes to the planet.
Franz Mesmer, a German doctor in the 1800s, is still remembered today as one of the pioneers of hypnotism, considered a legitimate medical phenomenon which is used in some forms of psychological therapy. However, today, we know that hypnotism works by the power of suggestion alone, and it’s really using the subject’s own thoughts. Mesmer himself became convinced that it was powered by “animal magnetism,” an invisible and imperceptible fluid that ran through all living things. By the right techniques, Mesmer said he could move this fluid around, and by the resulting friction, produce electricity, which he then claimed to use to heal people or control their bodies and minds. So, in other words, he thought he could use the Force–and, just like Star Wars, his claim turned out to be total fiction.
It’s hard to believe that we once didn’t know what oxygen was. After all, it’s probably the thing we need the most–one can only survive for a few minutes without breathing. But all the gases that make up air are colorless, odorless, and tasteless, and without a way to separate them, who could tell the difference? Not the creators of phlogiston theory–who, it must be noted, believed in the four classical elements of earth, fire, air, and water as the building blocks of the universe. How phlogiston was supposed to work was utterly tortuous and against the principle of Occam’s razor. Basically, phlogiston was some kind of material that was in flammable objects. Lighting something on fire supposedly released the phlogiston from the burning thing into the air. Because flames in enclosed spaces can die off without carbonizing the entire burning material, this meant that the air was completely “phlogisticated” and couldn’t absorb any more phlogiston, just like no more liquid water can be evaporated into saturated air. And, of course, breathing removed phlogiston from the body. When the components of air were finally isolated, scientists like Daniel Rutherford were able to show that oxygen burned as a fuel, and the theoretical mess of phlogiston was finally thrown away.