(about falling trees, personal experience, reality, and Pokémon)
I saw this fallen tree limb recently while walking with my dog in Goodale Park. It brought to mind that classic “tree falls in the forest” question that Jeff Olen guided me through many years ago in a college philosophy class: “When a tree falls in the forest and no one is there to hear it, does it make a sound?”
As I thought about the fallen limb and Dr. Olen, it suddenly occurred to me that I had been in the wrong course for this question. This isn’t a philosophy question. It’s a physics question.
“Sound” is the result of pulses or waves of compressing and expanding air that reach my eardrums and are interpreted by my brain. Sound is also a subjective experience, my experience. If I’m not there to experience a falling tree, the air compressions and expansions still happen, of course. But if there’s no nearby sensory apparatus (an eardrum or a microphone) available to interpret them as sound, then they are just air waves — existing and very real, but not “sound”.
It’s kind of like how the printed pages from my copy of To Kill a Mockingbird are just ink markings on paper until I’m there to experience them as a story. Likewise, in order for sound to exist, someone (or something) needs to be present as an observer.
The truth about the sound of the limb falling is just one of many counterintuitive dimensions of what is real. Other senses lead to more questions about the tree. For example, it seems even weirder to realize that I only see the tree because it is made of stuff that reflects light in a wavelength that I can observe with my eyes and interpret as color and shape. What I experience as an accurate and genuine image of the tree is completely created by my brain. In reality, the light waves anonymously flow through the air with the rest of the spectrum until I am there to experience them as a tree.
And even stranger, as I walk up to the tree, I can feel the rough texture of the bark only because it’s made of stuff that interacts with me. I need to be the “right kind” of observer; not all physical objects experience each other in the same “solid” way. For example, imagine two straight magnets with their north poles pushed close to each other. We’re all familiar with the way they push each other away because of the magnetic field. I can push the magnets together, but when I let go they spring apart as if a piece of foam rubber was between them. This “foam rubber” field is real to the magnets, but not to me! I’m not the right kind of observer. I can pass my finger right between the two magnets, and as far as my body and mind are concerned, the “foam rubber” magnetic field is not real. But the magnetic field is real, and it is “personally” experienced by the magnets.
In the same way, neutrinos (super tiny particles) are constantly spewed out by the sun, and they pass through Earth (65 billion of them per square inch per second) as if it’s not even here. The entire Earth is like empty space to these neutrinos, just like the “foam rubber” magnetic field between the magnets is empty space to me. We need to be the “right kind of observer” in order to physically experience specific parts of the universe.
As I fall down this existential rabbit hole, I’m reminded of Alfred North Whitehead’s interpretation of reality, “Process Thinking”. From his perspective, there are no objects, only experiences of the “processes” of our interactions. For Whitehead, nothing actually “exists” until our interactive experience makes it so. I talked with a nuclear chemist friend last week who reminded me that quantum mechanics provides evidence for this same idea at the atomic level. It sounds crazy, but it’s true.
We saw the truth of this in the last two examples, in terms of the need for the right kind of physical observer. We can also see the truth of this from the perspective of “contextual reality”. The tree in Goodale Park is a simple example. When the observer is a robin, the tree might be experienced as a “nesting place” or a “perch”, but when I am the observer, the same tree is experienced as a “shade provider”.
Similarly, contextual reality exists everywhere — Goodale Park literally only exists when experienced by certain kinds of observers who interact with it in its context as a park, like those who intentionally enjoy the playgrounds, read under the trees, or talk with neighbors at the pond. Goodale Park doesn’t really exist for people who just experience it as a pass-through to the Arena District, or as a free (albeit illegal) all-day parking lot, or as a Pokémon gym.
In a literal sense, there is no “true” objectively real “Goodale Park”. Sure, it’s grass and flowers, and a pond, and trees, and sidewalks, but it’s only a “park” when experienced as one. There is no park without an intentional observer, someone there to experience it as a park.
Whitehead was right; everything is only as real as we make it.
(Special thanks to Rachel VanScyoc for photo editing)