Democritus and Atomic Theory

So this week we will be looking at what we believe are some of the most vital inventions and discoveries in science throughout history, and when looking at important discoveries or inventions throughout history it is impossible to ignore the significance that the proof of atomic theory has, with it being so fundamental and part of the most ambitious and advanced scientific discoveries to this day, all while still not being exactly figured out yet.

Atomic theory as we know it today is the product of hundreds, or possibly thousands of different insights, with each scientist building upon previous work, mostly in the 19th and early 20th century, until we get to the understanding of atoms and what they do that we have now. But the idea surely had to start somewhere didn’t it? While it is impossible to say with certainty that no one before had ever had the idea that things had some sort of limit to how small they can be, the first evidence we have of anyone having this thought comes from ancient Greece, primarily from the pre-Socratic philosopher Democritus, and perhaps with some credit owed to his mentor Leucippus.

According to ancient reports, Democritus was born in about 460 BC.  His work has survived only in secondhand reports which are sometimes unreliable or conflicting. Most of the best evidence comes from Aristotle, who regarded Democritus as an important rival in natural philosophy. Of what Aristotle wrote about Democritus only a few passages survive, and those are also quoted in other sources themselves. But from these sources it appears Democritus took over and developed the views of his elder mentor Leucippus, of which very little is known about. Although it is possible to distinguish some of the work as that of Leucippus, the overwhelming majority of reports refer to either both Democritus and Leucippus, or to Democritus alone. The developed atomist system is often essentially considered to be Democritus’ own work.

Ancient sources describe Democritus’ atomism as one of a number of attempts by early Greek natural philosophers to respond to the challenge made by Parmenides, another of the philosophers. Today it is accepted that this is the reason for Democritus to start considering the theory of atoms. Parmenides argued that it is impossible for there to be change without something coming from nothing. Since the idea that something could come from nothing was generally agreed to be impossible at the time, Parmenides then stated that change is merely an illusion. In response, Leucippus and Democritus, along with other philosophers developed systems that made change possible by showing that something should not need to come from nothing. These responses to Parmenides suppose that there are multiple unchanging material principles, which persist and merely rearrange themselves to form the changing world of appearances. In the atomist version by Democritus, these unchanging material principles are indivisible particles, the atoms. The atomists are said to have fundamentally taken the idea that there is a limit to the number of times something can be divided, which tackles the paradox of the impossibility of traversing infinitely divisible magnitudes.

The atomists held the view that there were two fundamental parts of reality that make up the natural world, atoms and void. Atoms, from the Greek adjective atomos or atomon, which means ‘indivisible,’ are infinite in number and vary in size and shape, and are perfectly solid. They move about in an infinite void, repelling one another when they collide or combining into clusters by means of tiny hooks and barbs on their surfaces, which become entangled. Other than changing place, they are unchangeable, ungenerated and indestructible. All changes in visible objects of the world are brought about by relocations of these atoms. As Aristotle then described, the atomists reduce all change to the change of place. Macroscopic objects in the world that we experience are really clusters of these atoms and therefore changes in the objects we see such as growth are caused by rearrangements or additions to the atoms composing them. These atoms were considered to be eternal, but the objects made of them were not. They said that our world and the species within it have arisen from the collision of atoms moving about in such whirl, and will all disintegrate in time.

Much of this is obviously a sort of philosophical stab in the dark, with them at the time being completely unable to observe or test the theory without something like an electron microscope. Although we can see that at a base level Democritus had a surprisingly similar idea to the Atomic theory that was developed thousands of years later. Even though we know, or maybe think we know far more today, we also know that we aren’t quite done figuring it out yet. And anyway, when you start considering these things with quantum theory, who even knows what we know? For now all I can say is that Democritus had a good idea and it took about 2300 years before anyone properly looked into it.

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