Atomos

A tantalizing thought occurred to Democritus: What would happen if you kept cutting a substance in half?

Take that half, then cut that in half, too. Keep going, all the way down.

Democritus gave it some thought. There must be a smallest thing down there, some kind of particle so tiny as to be indivisible, or atomos, as the ancient Greeks called it.

This thing would be the building block of everything we see.

Around 2400 years ago, this Greek philosopher proposed a primordial version of atomic theory, the scientific understanding that the world around us is made of tiny, fundamental particles called atoms. The way these atoms interacted, Democritus said, determined how everything looked, smelled, felt, or tasted.

Then, for 2200 years, atomic theory languished unseen. Nobody much took it seriously or even remembered it.

While Democritus’s way of coming up with atomic theory was purely theoretical, Dalton’s was based entirely on experiment and observation. By the turn of the 19th century, it was possible to study gases of specific elements, and to record meticulous, accurate information about what happened when two gases mixed.

John Dalton was interested in the physical world from an early age, having grown up watching the weather change in his native Cumberland, England. As a teenager, he thought about atmospheric pressure, and how that caused rain and other weather patterns to form and dissipate. He built his own tool to measure atmospheric pressure, and he kept meticulous records.

Dalton’s work on meteorology helped to lay the foundation for modern weather predictions.

As a young scientist, he kept thinking about the same phenomenon: how the pressure of different gases caused them to interact differently. Dalton wanted to know why.

He began to carefully record measurements of gases in the lab. By mixing gases together, he noticed that the total amount of pressure exerted by several different gases was the same as if you took them one gas at a time, measured them, and added them up.

Each gas seemed to act like it didn’t even notice the other gases were there. It pushed on the walls of the container just as much. Dalton concluded that gases are made up of individual particles that do not interact significantly with each other.

Even more curious, the gases combined in simple ratios by volume, and this ratio was always the same. This became known as the law of multiple proportions, and it provided strong evidence for the existence of atoms. If matter were truly infinitely divisible, then it should be possible to combine elements in any proportion.

However, the fact that elements only combine in whole-number ratios suggested that there must be some fundamental unit of matter that cannot be further divided. Water is always H₂O, never H_2.5O.

Atomos.

Dalton’s atomic theory was revolutionary, not because the theory was new (Democritus just poked his head up above his grave), but because Dalton brought receipts. His careful observations lent credence to the tenets of the theory, that matter is composed of incredibly tiny building blocks, and that these building blocks are indivisible.

Dalton’s work meant that most mainstream physicists gradually came to accept atoms as a real concept, but many scientists remained skeptical, accepting atomic theory as a very useful framework, but doubting the actual existence.

Einstein helped Democritus and Dalton bring the story home. Up until then, a mysterious phenomenon had been observed: when pollen was put into water, the microscopic particles danced around. Nobody could explain why this happened.

This Brownian motion (named after a botanist named Robert Brown) perplexed scientists for the better part of a century, but Einstein developed equations that described the motion perfectly. These equations imagined that fundamental blocks of matter were the cause of these micro-collisions.

Years later, these equations were verified by French physicist Jean Perrin. Perrin precisely tracked the paths of tiny suspended particles through time. They moved exactly as Einstein predicted, finally validating the whole concept of atoms and molecules as more than just theories.

Imagine how fundamentally different the world is today, thanks to our understanding of the existence of atoms. Virtually all of the technology we use today relies on the knowledge gained since then.

Think about how Democritus asked the right question 24 centuries ago, and how that question was buried for 22 of the last centuries. What can we do to make sure we don’t stop asking the right questions?

What sorts of questions should we be asking today about the fundamental nature of reality?

Let’s think a little today!