Consider the Great Red Spot of Jupiter. It is a storm that has been around for two centuries. It’s a vortex big enough to contain two or three planets the size of the Earth. But is it a thing?
What does it mean to say that a thing exists? In what sense are plastic cups or rocks things? And are living things also ‘things’ in the same sense? To work towards a better understanding of ‘existence’, let us examine our intuition about the properties of things. A thing has a location in space and time, and a boundary that separates it from all that it is not. A thing can move around and morph its shape and size, but it retains some degree of integrity, so that as it undergoes transformations, it can still be recognized as the same thing. An apple remains the same apple as it decays, changes shape, and rolls around, until it crumbles and decays. These changes can be quite dramatic. When a caterpillar becomes a butterfly, we say that it has changed, and not that some new flappy thing mysteriously replaced the creepy-crawly that was there a few days before.
Another property of a thing that we might propose is that it is always composed of the same stuff. The atoms and molecules in a rock do not change much. You could make a little etching on the rock, and then find it later on, confident that you had found the same thing.
But I think this kind of material consistency is the exception rather than the rule for many of the things we are interested in. Let’s go back to the Great Red Spot. Surely it is a thing? It has been around since long before you or I were born. Astronomers are readily able to identify it and talk about its shape and location. But a storm like the Great Red Spot does not generally retain all the material contained in it. Stuff comes in, stuff goes out. Back on Earth, we know that a storm can pick up gas molecules, water, houses, people and cows, and dump them elsewhere. Perhaps some molecules stick around with it for the duration of its destructive dance, but plenty of others just hitch a ride for a little while.
A storm is a process. And it is also a thing. It has position, velocity, shape and size, but it does not have a constant configuration of atoms and molecules. In this it is like a wave. There’s a lot you can learn about wave motion from a rope or a string. If you tie one end of a rope to a stationary object, you can send a wave along it by making the right sort of up-and-down shake on the other end.
I recommend playing around with this handy web applet that let’s you send waves along a virtual rope. And here’s a picture of some scientists doing the real thing in a classroom:
What I’d like to draw your attention to is the fact that when a wave moves horizontally along a rope, the particles in the rope do not move horizontally. If they did move horizontally, the rope would eventually break! In fact, they move up and down. What moves along the horizontal direction is the movement itself. If we want to consider the wave a thing, we have to concede that it is not made up of a specific set of particles. It is a process, and the particles are just the medium by which the process flows.
What applies to waves also applies to human beings. The oldest particles in your body have been with you for perhaps seven years. The body is not a constant set of particles, it is a wave, a travelling pattern, a Great Spot whirling around the surface of the Earth. And in a sense, you already knew this. You take in food, air and water every day, and yet you maintain the same weight. (Well, more or less the same weight.) Cells die and are replaced by new ones that are made up of the matter you ingest. You are what you eat.
I like the way Richard Feynman gets this point across. “So what is this mind of ours: what are these atoms with consciousness? Last week’s potatoes! They now can remember what was going on in my mind a year ago—a mind which has long ago been replaced. To note that the thing I call my individuality is only a pattern or dance, that is what it means when one discovers how long it takes for the atoms of the brain to be replaced by other atoms. The atoms come into my brain, dance a dance, and then go out—there are always new atoms, but always doing the same dance, remembering what the dance was yesterday.”
So we are not what we are made of. We are what we do.
When we realize that all things are also processes, the concept of existence can take on a new meaning. Perhaps we should shift our focus from the idea that existence is about things. What exists is what is happening. No process goes on forever, and thus we can’t really speak of the things that exist for all time and in all places. Things, people, societies, ideas… these are all dancing patterns, and when the dancing stops, only stillness remains.
I began thinking about the ‘wave’ nature of human beings when I read an article from the Edge Foundation by Tor Nørretranders. “I have changed my mind about my body. I used to think of it as a kind of hardware on which my mental and behavioral software was running. Now, I primarily think of my body as software. [...] 98 percent of the atoms in the body are replaced every year. 98 percent! Water molecules stays in your body for two weeks (and for an even shorter time in a hot climate), the atoms in your bones stays there for a few months. Some atoms stay for years. But almost not one single atom stay with you in your body from cradle to grave.”
All the matter in us and around us was produced inside the furnaces of stars. If you believe in modern science, the phrase “we are stardust” is not a metaphor! But of course, we are more that just stardust. We are waves that use stardust as a medium for propagation.
If you use a spring instead of a rope, you can see two types of wave motion: transverse and longitudinal. Transverse waves are like the ones on a rope, with the particles moving in a up-and-down direction. In longitudinal waves, the particles do move back-and-forth in the horizontal direction, but still do not travel with the wave.
Wave-particle duality suggests that at a very fundamental level, the distinction between particle and wave can be blurry. Also, condensed matter physicists often find it useful to characterize the systems they study in terms of “quasiparticles“. You could go as far as saying that the a particle can be redefined as a type of phenomenon or interaction, rather than a thing. From here we can question the meaning of the word “fundamental”, perhaps be opposing it with the word “useful”. More on this later.