The Universe doesn’t care. Really what I mean is…

How the universe operates and how we understand and analyze it are entirely different.

The universe…

• doesn’t define or categorize things, like mammals vs reptiles, or life vs non-life
• doesn’t calculate things, like quantum mechanics or relativity or three-body problems
• can’t be divided into holistic vs reductionistic situations, or matter vs space

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DOESN’T DEFINE OR CATEGORIZE THINGS

Most people are comfortable with this idea in some areas, but it’s much more widely true than we realize. It’s universal, in fact, and I have to remind myself all the time. Humans are built to categorize things – it’s a dramatic help in operating in the world.

So everyone knows about mammals vs reptiles. Although the example we all know and love, platypuses, aren’t really in between – they’re squarely within the mammal lineage, they just evolved a little differently. So nature doesn’t care – it makes what it makes. Most quadrupeds fall comfortably into our mammal or reptile or amphibian categories, but a few don’t, such as amniotes >. There’s something stable about those three forms in currently existing ecosystems on Earth, but those three forms are not things are far as nature is concerned, and there have been many other forms throughout history.

Ditto for life vs non-life – nature doesn’t care. There are many degrees of life, and it’s not a matter of suddenly something is across the threshold for life, and now it’ s a different type of thing with new special properties.

Humans categorize: you’re labelled as depressed therefore you have these qualities and need this treatment (that’s way overgeneralizing); that thing is living therefor it’s special (it is to us, but not to the universe); etc. You have a crazy red sore throat therefor you have a strep infection and need this antibiotic. It’s useful when  it’s useful, but it’s not when it’s not, and the universe doesn’t do it. It only helps us, kinda like holistic vs reductionistic thinking, or calculating things symbolically.

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DOESN’T CALCULATE THINGS

A good example is the three-body problem. In classical mechanics (ignoring the even more complex real-life of relatively and quantum mechanics), you can exactly solve the equations of motion for a two-body system, but not a three-body system (when the force is 1/r2 like electricity or gravity). We can write an equation and solve it analytically to come up with a closed-form solution for a two-body system, like a hydrogen atom (classical mech version) or two stars. Then you can plug in any time you want with any precision you want and get the locations of the bodies to any precision you want. But for a three-body system, like a helium atom (classical mech version) or three stars orbiting each other (or two planets orbiting one star, though that’s less challenging numerically ‘cuz it’s almost though not quite two separate two-body problems), you can’t solve the equation analytically, so you don’t end up with a closed-form solution – no equation you can plug in an exact time and get exact positions. You have two choices: an approximate equation, or a numerical simulation.

That’s how we do it. But how does the universe do it? Basically it’s running an infinite-precision numerical calculation. See How the Universe Does It

Back to what it doesn’t do. It doesn’t know anything about equations of motion. It has no notion of what the trajectory will be, nothing about the future. It can’t plug in a time number and get positions and momenta. The future doesn’t exist and neither does the past. All it knows is the present. So this applies even, in fact especially noticeably, to the two-body problem! We want equations of motion, we feel good, like this is how it’s supposed to be, this is a well-described situation. But the universe doesn’t care and can’t do that even. Read about the one-, two-, and three-body problems.

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DOESN’T DIVVY THINGS UP

We think of matter (or waves) as things in space; they’re different things, though of course they interact. But to nature the boundaries aren’t so clear.

We also like to think reductionistically or holistically. Cells, atoms, fundamental particles and forces – that’s reductionistic thinking, building things up from there. Conservation of energy, the entropy principles, yin-yang balance of complementary things, etc – that’s holistic thinking, knowing that the microscopic combines to obey these big laws. Well, that’s for our convenience, and nature isn’t divided up that way.

Read more about holism vs reductionism.

NEXT IN THIS SERIES: How the universe does it