things like the cold, the flu, strep throat,

came from wandering clouds of poisonous vapor?

You'd probably think that absurd, and, don't worry, it's completely wrong.

Yet that's actually what people thought caused diseases for several centuries.

They called it miasma theory,

and everyone from the public to the medical establishment accepted it.

But by the 1840s, in the midst of devastating cholera outbreaks in London,

a small group of scientists had grown skeptical.

Early microscopes had revealed the existence of tiny microorganisms,

and they proposed that it was actually these germs that cause diseases,

hence the name germ theory.

Though most people held onto their assumptions

and strongly resisted this theory,

its supporters were determined to prove them wrong

by collecting compelling data.

Leading the charge was a physician named Dr. John Snow.

Dr. Snow observed that cholera-infected patients

experienced severe vomiting and diarrhea,

symptoms of the gut as opposed to the lungs,

and thought that perhaps the disease was transmitted through food or drink,

not the air.

After investigating previous outbreaks,

he became convinced

that cholera was spread through contaminated water sources.

Then, late in the summer of 1854

when cholera suddenly struck the Soho district,

a neighborhood in London very close to his own,

Dr. Snow was hot on its trail.

He requested the records for the deceased,

and within the first week, there had already been 83 deaths.

He mapped out where each of the deceased had lived

and found that 73 of them resided close to the water pump on Broad Street.

Dr. Snow strongly recommended shutting down the pump,

and because he knew how unpopular germ theory was,

he suggested that cholera was spread through a poison in the water

instead of microorganisms,

when presenting his case to governmental officials.

They were unconvinced,

but agreed to shut down the pump as an extra precaution.

Almost immediately, new cases of infection subsided.

Bolstered by his success,

Dr. Snow was determined to connect the contaminated pump water

to the disease.

He found the story of a widow who had died of cholera

and lived far away from Soho,

but had a servant bring her water from the Broad Street pump daily

because she liked the taste.

He also discovered a workhouse

located around the corner from the Broad Street pump

that housed hundreds of people, but only a handful had become infected,

which Dr. Snow attributed to the fact

that the workhouse had its own private well.

Finally, Dr. Snow heard of an infant

who may have been one of the earliest victims of the outbreak.

He learned that the child's dirty diapers

had been thrown into a cesspool

right next to the public water pump on Broad Street.

Again, Dr. Snow presented his case,

but even then, city officials spurned his theory,

not wanting to admit that there was human waste in London's water supply,

or that they were wrong about miasma theory,

which was, after all, hundreds of years old.

It wasn't until 1884 that Dr. Snow's efforts

were vindicated by Dr. Robert Koch,

who isolated the cholera-causing bacterium.

Koch developed a technique to grow pure cultures,

and through a series of experiments,

definitively proved that a specific bacterium

directly cause disease.

Major contributions to germ theory

also came from prolific scientist Louis Pasteur,

whose study of microorganisms led to the development of the first vaccines.

By challenging assumptions with data-driven research,

these scientists discredited an age-old theory

and sparked a revolution that was incredibly beneficial to public health.

But all of this raises the question,

what are the widely held scientific beliefs of today

that our descendants will find ridiculous?

And as any scientist would tell you,

a question is an excellent place to start.