6 Prior to discovering oxygen and its role in combustion, scientists proposed that a substance called “phlogiston” did exactly the opposite—was released by burning fuel, squelched fire when it saturated airtight spaces, and was even expelled from the body through breathing.

More than 100 years ago when oxygen hadn’t been discovered, scientists and philosophers believed that fire was an element. All combustible objects contained a fire-like element which was released into the atmosphere during combustion. This element was called “phlogiston.” The phlogiston theory was first stated by Johann Joachim Becher in 1667. This theory was used to understand processes such as combustion and rusting.

Until the 1770s, the phlogiston theory was the most widely accepted theory. Its popularity can be understood by the fact that when Joseph Priestley discovered oxygen in 1774, he called it “dephlogisticated air.” (1, 2)

7 Before the concept of vacuum came into existence, physicists believed that there was no empty space in the universe, and light traveled through a medium called “aether.” It was considered a fifth element along with earth, wind, fire, and water.

According to the ancient and medieval science, the space above earth’s terrestrial sphere was filled with a material called “aether”, also known as “quintessence” and now referred to as “ether.” It was believed to fill the universe and act as a medium for the propagation of light. Until the 19th century, various physicists conducted numerous experiments but couldn’t find any physical evidence that could prove the existence of ether. Its end came after Einstein’s “Theory of Relativity” was published as it solved many theoretical problems related to ether. Since then, ether has been considered to be non-existent. (1,2,3)

8 In the 19th and early 20th centuries, benzene was used as an after-shave because it smelled nice. Also, it is one of the best organic solvents, so organic chemists used to wash their hands with benzene even though it is actually highly carcinogenic.

In the days gone by, scientists didn’t know that benzene is carcinogenic (can cause cancer) in humans. That’s why it was used in various ways. Benzene was used as an after-shave lotion in the 19th and early 20th century. In 1903, benzene became popular in industries as it was used to decaffeinate coffee. Before the 1920s, it was used as an industrial solvent.

Historically, benzene was a significant component of many consumer products such as rubber cement, paint strippers, spot removers, and liquid wrench. It was even used by chemists to wash their hands. But, as the toxicity of benzene became obvious, its use was slowly discontinued. (1, 2)

9 Until recently, it was a popular scientific belief that different sections of your tongue react to different tastes.

Almost everyone who had attended their biology class had at one time or another seen the tongue diagram, also known as the “taste map.” It contains the image of a pink tongue with regions marked for various tastes. It shows that there are particular regions in our tongue which can detect a particular taste only. In reality, the tongue diagram is completely wrong. Chemosensory scientists have debunked the myth, yet it is still taught in some schools.

The tongue diagram originated from a paper published in 1901 by a German scientist, David P Hanig. He found that different parts of the tongue have a lower threshold for perceiving certain tastes. But the differences are extremely minute. The diagram sketched by him was the artistic interpretation of his measurements. The diagram was wrongly interpreted and later accepted by the world as the taste map. (1, 2, 3)

10 Up until the mid-19th century, it was commonly believed that placing dirty underwear in a bucket with wheat grains would “generate” mice. This was called “spontaneous generation,” the idea that life could be created from nonliving objects.

Many centuries ago, it was a common “knowledge” that non-living objects can give rise to living organisms by “spontaneous generation.” This theory materialized from daily observations of people and scientists. Farmers noticed that an otherwise empty barn would be brimming with rats and mice when grains were stored in it. So, they thought that rats and mice generate from grains. Similar observations gave rise to beliefs such as rotten meat creates maggots and flies, and muddy soil gave rise to frogs, worms beetles etc.

The theory of spontaneous generation held its ground firmly until the 18th century. After that, various experiments by scientists suggested that higher organisms could not be produced by nonliving objects. The end of this theory came later in the 19th century when Louis Pasteur showed the world that microorganisms such as bacteria can reproduce. (1, 2)