If you take a moment to look around you, it’s a gorgeous world. Every single thing you see that is solid has a shape, and the liquids and gases swirl and wave in ways that are wonderful to watch. The macroscopic world is not only beautiful but it is functional. The shapes, sizes and colors have function and meaning and in most cases, purpose.
But even the young school children know something like a tree is not one solid piece. There are at the very least, bark, leaves and branches. Right now if you look around wherever you are, you will probably easily notice that most things are made of pieces. As I write, I am at my desk and in front of me I see pens, my computer screens and a couple of speakers. The pens have caps and clips and I know inside I will find a thin pipe and inside that I will find ink. The screens have a variety of plastic pieces all with different purpose and I know there are circuit boards and wires inside. The speaker has a variety of buttons and knobs and the different kinds of materials are obvious. Without really thinking about it, we see a pen, a screen and a speaker – the whole – but upon closer inspection, most things can be decomposed into parts.
That continues down to the microscopic level. The problem with this idea comes when we can’t rely on our eyes or sense of touch to differentiate the parts. It’s an easy concept to handle when the different parts can be placed in front of you. We can be aided by tools such as lenses and microscopes to extend our vision to smaller dimensions. It becomes much harder when we are left only with our imagination but that is what we are forced to do when we break things down beyond a certain size – when we move into the realm of atoms and molecules, which are the building blocks of everything we can touch and see. No one has ever seen a single molecule, not even the best scientist. They are simply too small for the light we respond to with our eyes to interact with an atom properly and return that light to our eyes. It’s never going to happen.
So it seems we are required to use our imagination on order to “picture” an atom or molecule. This activity of imagining is common in science and we call it model building. We collect as much knowledge and information we can about an object, like an atom, and we create a picture in our head, or some other kind of representation, that includes those pieces of knowledge. If the model builder knows a lot, the model can be very detailed. If the builder knows little, the model will be less complex. Whether complex or simple, we rely on imagination to see the things our eyes cannot.
This idea of a basic building block of matter has been around for thousands of years. The simplest arguments still are valid. If one takes a very sharp blade and cuts any object in half, then again in half, then again, at some point the process must end. At some point, there will be an object that cannot be divided and this is where the idea of the atom came from. In those early days, there was little information about this basic building block other than it must exist, so the model, or the “imagining” of this building block was very simple. It’s enough to say that the building block is like a spherical marble (or much like a billiard ball if you prefer the larger scale) and the marbles that make up one material, say carbon, are different from the marbles that make up nitrogen. I may not know how they are different, but because a chunk of charcoal (carbon) is very different from the inert atmosphere I breath (nitrogen) they must be different because carbon is very different from nitrogen.
With passing time and more thought and investigation, the differences in these atoms became clearer and in future posts we will discuss those differences. But for the vast majority of the science problems you will probably encounter, thinking that atoms are these simple spherical marbles will take you far. This is our most simple but useful model of the physical universe. All things are made of atoms and those atoms are represented by tiny marbles so small they will never be seen. Whenever you consider an object, think about smashing it with a magic hammer with the result being the object is reduced to these very tiny marbles we call atoms. Every thing in the physical universe can be smashed into atoms.
Of course, this creates all kinds of questions. For example, if all things are made of these marbles, why does a brick feel so solid? Why can’t I push my finger through the middle like I do with a bag of baseballs? And in fact, I can do that with water, so why with water but not the brick? And what about those differences between carbon charcoal and nitrogen gas? Does this mean my model is wrong?
No, it does not mean the model is wrong but it does mean the model, when used at this level, does not describe everything. For me, this is the fun in science: To imagine a model, and then find the failures of that model. That’s really the work of science, to build better and better models. We’ll talk about this more in future posts.
Main Points: All things we can see and feel in the physical universe are made of parts or pieces. If we take one of those pieces and cut it in half, then again in half, and again and again, eventually we will find the basic building block of matter called the atom. We will never see an atom with our eyes, so we must imagine its structure. We call this imagining a model. A very simple and useful model of the atom is that of a spherical marble, or billiard ball. All things in the universe are made of these marbles. Any object, when struck with a very special and magical hammer will produce nothing but marbles which are the atoms.