So we see that science is not a belief system or a dogma but actually a system for observing the universe and attempting to place those observations into a reasonable framework for understanding the underlying causes for those observations.
Let’s follow just one path of the scientific method through history. To see how this works out in the real world.
We have our first recorded instances of something like science in ancient Greece. There, people started to give credence to the idea that natural occurrences might have natural causes. There wasn’t really much in the way of experimentation back then. This embryonic science was actually more like philosophy. But they were attempting to explain the universe without resorting to explanations involving gods or the supernatural. They still believed in gods and the supernatural, they just thought that there might be some explanations that didn’t involve them directly. This is sometimes referred to as natural philosophy. One of these early ideas was that things weren’t each completely individual. That all matter (though they didn’t call it that) might be made up of a simple material or small number of materials. The first person we know of that hit upon this idea was a fellow named Thales who, at the end of the 6th century BC, decided everything was made of water. Over the next century or so other Greeks got into the act. Anaximenes thought that basic substance was air. Heraclitus decided it was fire. Finally, by the middle of the 5th century BC, Empedicles hit on the diplomatic solution that everybody might be right and instead of one thing, the world was made up of a few things. They had no way to test any of this, but it seemed reasonable. Aristotle added a final basic substance, called Aether, to account for the stuff that bright extraterrestrial objects such as the sun and the stars were made of. The Greeks called these basic materials Elements.
So if everything is made up of earth, air, fire, and water (aether being different because it was for celestial objects), how were they mixed? At the start of the third century BC, Leucippus speculated that if you were able to take the smallest component of anything you would find something so small as to be impossible to divide further and that there was space between these tiny particles even in the densest substance. One of his students, Democritus, thought that the idea of tiny particles surrounded by voids (empty spaces) explained how things could move and change. He decided to call these smallest bits of anything Atomos (unbreakable). Not everybody bought into this however. Aristotle and another big brain of the time, Plato, thought that what made primary elements primary was that they were infinite. Not made up of smaller particles but a basic part of the fabric of the universe. And since they were considered among the wisest men in Greece, their theory carried popular opinion (remember, no body had figured out how to do experiments on this stuff yet).
Nevertheless, in spite of popular opinion others thought what Leucippus and Democritus had said made a lot of sense. Among these was Epicurus (who is familiar to us through the term Epicurean) who was the leader of one of the philosophical schools in Greece around the start of the third century. He made this idea that everything was made up of extremely small, indivisible particles with space between them a basic part of his teachings. Titus Lucretius Carus, a Roman follower of the Epicurean school in the first century BC, wrote a poem explaining Epicurus’ views on the subject in great detail. While none of the writings of Epicurus survived into modern times (there are indications that he wrote over 300 books), Lucretius’ De Rerum Natura (On the Nature of Things) was a smash hit in old Rome and wound up being extensively copied. Unfortunately, a few centuries later the Christian church decided that Lucretius was an atheist and the copies of his book were burned or lost.
Then, in 1417, a single copy of the poem was found and a few years later was one of the first books published with that modern wonder of the time, the printing press. Once again the poem was a smash hit. At the time people in Europe were crazy for any learning from the Ancient World and the fantastic idea that everything was made up of tiny particles with space in between was the 14th century version of The Matrix. French philosopher Pierre Gassendi became a major proponent of the idea and through his extensive writing one of the budding new experimental scientists, Robert Boyle, decided to see if he could put it to the test.
Boyle figured that if everything was made up of tiny particles then the difference between states of matter must be how far apart those particles were. If that was the case there must be some way to press the particles closer together. He did this in 1662 by taking a hollow glass rod shaped like a “J” with the small end closed and pouring mercury into the open end. The mercury trapped air in the short end of the cylinder and by pouring more mercury into the open end he could compress the air and increase the pressure. Taking careful measurements of how the air was affected, he was able to figure out that increasing the pressure of a gas caused a proportional decrease in the volume of the gas. This made perfect sense if the gasses were made of tiny particles with space between. Squeezing the particles closer together made the gas smaller. It also led to the conclusion that, if everything was made up of tiny particles with space in between, the reason that a given volume of lead was heavier that the same volume of air was because the particles were closer together.
Not everybody was convinced. But there were no better explanations of the experimental results and anybody could do the experiment for himself (or herself) if they didn’t believe the results. Atomism provided a logical and simple explanation of what was going on.
(Now I know what you’re thinking. Big whoop. But it turned out to be important in all sorts of ways. For instance, if you scuba dive. In the 1940’s a Frenchman named Jacques-Yves Cousteau invented the demand-valve aqualung allowing divers to inhale freely in spite of the increasing pressure found at any significant depth underwater. Advanced SCUBA divers can calculate Boyle’s Law in their heads knowing that about 33 feet of water is equal in density to all the air in the atmosphere over their heads at sea level. And yes, it’s THAT Jacques Cousteau, the one who made all those underwater documentaries.)
So two thousand years after the debate started, Boyle proved that Lucippus was right and the representatives of the common wisdom, Plato and Aristotle, were wrong. It seemed that everything was made up of little particles. Ah ha, but what were the little particles made of?
Well, if the Greeks were right about atom perhaps they were right about elements. But it was pretty obvious by this time that the elements they had picked weren’t actually elemental. It was already known that a lot of things could be broken down into simpler things by chemical reactions. But how far could this be carried? How would you know when anything had been broken down as far as it could go? Boyle thought that the whole question could only be proved by experiment and in 1661 wrote a book, called The Skeptical Chemist, in which he said so. So for years after that, chemists took chemical compounds and did everything they could think of to break them down chemically.
In 1789 chemist Antoine Lavoisier realized that whenever a compound when through a chemical reaction the end products weighed the same as the compound did originally. And that it worked both ways. Whether a reaction combined things or disassociated them, you wound up with the same amount of stuff as you started with. This led him to decide that matter was conserved through the reaction. Nowadays we call this the Law of Conservation of Mass.
Ten years later, in 1799, a chemist named Joseph Louis Proust was working with copper carbonate. True to form, he never lost any copper, carbon, or oxygen whether he was adding them together or breaking them down. But he realized that he also wound up with the same proportions every time the reaction occurred. This led him to surmise that certain elements combine with other elements in constant proportions.
But nobody knew why.
Because nobody knew the nature of the particles themselves.
And the answer to that mystery was waiting for a fellow named John Dalton to unravel it.