Life on Other Planets

Much of the public interest in space has always revolved around the idea of life on other planets. We know that there are other planets, even around other stars, some of them even “Earth-like”, in some optimistic definitions of the word. But the current lack of detailed information about such places makes fertile ground for imaginative speculation. I will try to refrain from speculation here, and stick to the factual.

We have many inborn instincts that deceive our minds about the matter. For one, we think that recognizing life and intelligence is easy. Just bring it before us and we will categorize it as either:

  1. alive and intelligent (example: elephants, some whales, great apes)
  2. alive and non-intelligent (example: bacteria, lichen, viruses)
  3. non-living and intelligent (example: ?)
  4. non-living and non-intelligent (example: vacuum, atoms, radiation).

It is of course our generalist diet and dependence on social behavior that make recognizing life and intelligence so important and instinctive to us. It takes a lot of effort not to anthropize everything that we encounter, not to react to what our brain thinks is a face for example.

Our ancestors walked for thousands of kilometers, encountered new environments and ecosystems, and survived. We are all descendants of surviving colonists. Our species has traveled just about everywhere on the surface of this planet, and marked all the habitable places. That is, habitable for humans. As we have expanded the reach of our scientific equipment, we have found life in places where we never though there would be life: at the bottom of the ocean at thousands of atmospheres of pressure, in scalding heat or acidity, living with no direct access to sunlight. We call these kind of beings “extremophiles”, because they live in environments that are extreme compared to our human views of habitability.

What makes life, and indeed intelligence, so interesting is that it breaks molds, defies definition, and jumps from host to another, forever in between destinations. Life, as we understand it, exists in the interstitials, in the sweet spots between states and phases, conversing in an endless dialogue between solid and fluid. As much as we humans like categorizing things, life itself cannot be contained in any box (or if it can, it will die inside it).

Life, as we understand it, exists in the interstitials, in the sweet spots between states and phases, conversing in an endless dialogue between solid and fluid.

As a species, we have traveled thousands of kilometers vertically, but move just ten kilometers straight up or down, and the Earth becomes hostile; with either too much or too little pressure for human habitation. It is not the planet as a whole that is habitable, just certain zones within a thin layer of it are. Our senses evolved to this thin layer between the earth and the sky, and until modern science did not even become aware of the many invisible layers and processes above and below this one, that our lives depend on: the ozone layer, the magnetosphere, ground water, deep ocean currents.

The circulatory systems of the Earth, the water cycles, the carbon cycles, and various mineral cycles, all must align at sweet spots for life to flourish. Such fertile locations include of course the alluvial plains, where human city-cultures arose some ten thousand years ago. But there are also two especially active locations on Earth: the Amazon, and the Great Barrier Reef.

Gravity presses tons of bioavailable minerals to the bottom of the oceans, where the lack of sunlight prevents plants from making use of them. Only deep ocean currents, or continental drift can bring these nutrients back to the surface. By the rotation of the Earth, nutrient dust is regularly carried in the air from Africa to Southern America, where it meets water vapor coming from the Pacific (both wind directions driven, paradoxically, by the very same rotation of the planet). Where they meet, the Amazon.

The Great Barrier Reef, the largest structure created by life on Earth, was born when a large slice of coastal plain became flooded about ten thousand years ago. The edge of the continental shelf stays close enough to the surface to receive plenty of sunlight, creating large lagoon-like areas between it and the current coastline. Like they do for ships that sink, corals started to metabolize the trees and other matter from the moment they became submerged, slowly covering them in an accumulation of rock-like deposit. In addition to material flowing in from land, nearby ocean currents such as the Capricorn Eddy help sustain the ecosystem by bringing up nutrient-rich waters from the seabed.

When we now look to the Solar system, our colonist intuition tells us to look for solid surface, terra firma, somewhere to raise a flag and stake a claim. But to truly make humans a multiplanetary species, we need to build, grow, or transport an entire ecosystem capable of sustaining both itself and us humans at the top of the food chain. Quite a few species will have to become multiplanetary in order for that to happen.

As it happens, one of the most promising location for humans discovered outside of Earth exists about 50 km above the surface of Venus, where the levels of temperature, pressure, gravity and radiation are all comparable to the thin layer of Earth we call home. There is of course nothing solid or liquid at that altitude, nowhere to plant anything, not even the intrepid explorer’s flag. A conceptual project (HAVOC) has been proposed to study the conditions in that altitude in Venus (and possibly to invent a flagpole adapted for clouds). But to make that layer into a permanent second home for humans requires designing the ecosystem from scratch. This idea is daunting, but also liberating. I for one am excited to imagine the steps needed to grow our own “Great Reef” to float in the sky of another planet. Most of the building materials should already be present; if you think about it, trees on Earth create solid wood almost entirely out of air, out of thin air. On Venus, CO2 and sunlight are in abundance.

In the same way as when life arose from the seas and moved onto land, moving life into space will have to be at least as much adaptation as conquest. Climbing the formidable gravity wells accommodate travelers best when packed into the smallest mass possible. Ideally, just the instructions how to grow life could be packed into small “seeds” that could then adapt to the local conditions when they arrive (or it is thinkable that this has already happened long ago, and we are the result of panspermia).

All currently known life forms, even extremophiles, have evolved and adapted into the wonderful thin layer of our planet, this “region of interaction” first named biosphere by Eduard Suess. What are the necessary characteristics of such a layer of interaction, and how do they contribute to life as we know it?

On first approximation, the surface of the planet is where the different phases of matter separate, the solid earth, the liquid water, and the gaseous air, like the concentric spheres of classical cosmology. But the solidness and fluidness of a substance is relative, and our senses experience them as such because we have evolved into this layer. It is thinkable that a lifeform adapted to a different layer, or with different mass and strength would see things differently. For example, a bird might sense air currents like a fish senses water, or an elephant senses vibrations in the ground.

The point of view also changes with timescale, and density. The smallest flying insects experience the air viscosity differently, and their flight is more like swimming than gliding. If you are made of gossamer you experience more things as hard and solid than if you were made of diamond. The slower your perception is, the more foggy movement appears, and so on.


Courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.

The spherical shape of a planet’s surface is the result of the opposing forces that act on its mass: Gravity pulls everything together, while pressure pushes outward in all directions. The total sum of countless trillions of small collisions eventually separate the mass of the forming planet into layers, of which the separation between “surface” and “atmosphere” is just one.

The end result of the separation process could be just a lifeless set of perfect concentric spheres, like the rings of Saturn. But on Earth, the separation is not complete, there are continuous cycles of matter, interacting over the layer boundaries. An example is the water cycle, continuously evaporating, condensing, raining, sublimating, diluting and conveying all over the biosphere.

This spontaneous layering to spheres follows density, so it does not necessarily result in ordering by phases of matter. In addition, increasing pressure towards the center can melt material that would otherwise solidify. The current theory about the internal structure of our planet is that it has a solid inner core, surrounded by liquid outer core, surrounded by viscous mantle, with a mostly solid crust on top

And of course at planetary scales, solidity is relative. Also gases, when they are thick and viscous enough, can behave more like liquids.


Gored Clump in Saturn’s F Ring (Image Credit: NASA/JPL-Caltech/Space Science Institute)

Chain reactions must triggered by something. Just like a snowflake cannot form without a seeding speck of dust, the complex biochemistry of life cannot appear if all base materials are just cleanly separated. Some flaws must be present in the interface, it cannot be a perfect mirror. Crystallization cannot start without a seed, and crystals do not naturally grow into perfect spheres. Exterior solid crusts inevitably erode into uneven rocks and sands, due to to tidal forces, winds and waves, even meteor collisions if nothing else.

The concentric spheres of matter must interact, even interpermeate to some extent, to make them more fertile places for life to evolve. Reservoirs, niches, potentials and flows should be present, with local variations in temperature, flow speed, density and such. Growth can then slowly adapt to different situations, as long as the overall conditions are stable enough.

Such interactive layering does not happen only on planets. The surface of the Sun is also wildly active and complex, but due to its heat cannot sustain the kind of complex biochemistry that we associate with life. The valencies of the chemical bonds in an organism need to be compatible with the ambient energy levels (including radiation) of the environment, so that macromolecules can be both synthesized and broken down near each other.

By a big stretch of the imagination, we might theorize a system of life not based on macromolecule synthesis, or even molecules. For example, we don’t really know what happens in the layers of quark soup in the pressures of a rotating neutron star. But for now, such things are beyond what is known, clearly in the realm of speculation which I said I would try to avoid here.

Even if we stay within the realm of chemistry, we should be looking for life in the shapes and forms that are expressed through it, rather than reducing it to any kind of quantitative process. Otherwise there would be no other purpose to life than “to hydrogenate carbon dioxide”.

gold coins, in stacks on the lowest row of a wooden chessboard

Powers of Two

Place one gold piece in the first square, double the number in the second square, double again in the next square, and so on, filling all 64 squares of the board. How many gold pieces is that in total?

In real life, you should not try this indoors, since the stacks of coins will soon increase in height beyond any roof made by man. The board should also be sturdy, to support the tons of weight placed on it. Due to shearing winds at higher altitudes, the coins would need to be fused together pretty soon, turning from stacks into solid rods of gold.

Barely halfway through the board, at square 35, all gold ever refined by humankind so far, 180 thousand metric tons, would have been cast into coin-rods and placed on the same chessboard. Around the same time, the rods are no longer pressing all their weight against it, since their center of mass would be orbiting the Earth at ever higher altitudes. Eventually the rods would become tethers, their rotating inertia pulling away from the board game with more force than Earth’s gravity pressing them against it.

In the end, assuming enough gold is refined, the stack of coins in the final square would reach well into the Kuiper belt, beyond the orbit of Neptune. Even if the gold is welded into a solid rod, it would not stay straight, or even in one piece, for very long. Light would take over four hours to travel from one end to the other, and local pulling forces would not be able to balance out along the whole rod.

The whole exercise is of course just an educational story, meant to reveal the poor grasp of numbers and magnitude that human intuition is cursed with. It is not known where or by whom it was originally told, but most versions of it are told with grains of wheat or rice, or salt, all things that come in small sizes.

But what if instead of doubling the amount in each square, you were to halve the amount of gold in each square? Start with a single gold coin, cut it in half, move the half into the next square, then a quarter, and so on? Would it be possible to have a piece of gold in each 64 squares of the chessboard?

Gold is soft and malleable enough to cut, at least when pure (this is why real gold coins are usually not pure gold; but let’s assume purity here, for the sake of the argument). In fact, with stone-age tools it is possible to beat gold to such thinness that its edge becomes invisible: it is thinner than the shortest wavelength of visible light. Already on the second row of the chessboard it becomes necessary to use gold leaf instead of nuggets. This is good for the visibility of the remaining gold; it also helps that gold foil naturally attaches itself to the underlying surface, making it less likely that a light breeze blows away the invisible gold dust in the lower squares.

Gold was considered the noblest substance by the ancients, embodying the idea of material permanence. If gold can be beaten so thin that sunlight is visible through it, why not beat it even thinner, until it becomes as thin and light as the Emperor’s new clothes? What is the internal force that makes thinning the foil ever harder, the thinner it gets? And could we, in theory, continue dividing the gold forever, if we had the means to see it and the power to thin it?

In the middle of 19th century, the great experimentalist Michael Faraday attached gold leaf to glass plates, and studied it under the most powerful microscopes available. He was looking for, among other things, hints of any fine structure, such as the existence of atoms or molecules, strongly suggested by the works of Dalton, Avogadro, Berzelius and others. In his Bakerian lecture from 1856 he writes

“Yet in the best microscope, and with the highest power, the leaf seemed to be continuous, the occurrence of the smallest sensible hole making that continuity at other parts apparent, and every part possessing its proper green colour. How such a film can act as a plate on polarized light in the manner it does, is one of the queries suggested by the phenomena which requires solution.”

Faraday had a knack, and was already famous, for making unusual experiments and finding strange natural phenomena for other, more theoretical-minded scientists to then try to explain. It was only a few years later, in 1865, that Jacob Loschmidt referred to Faraday’s experiment, in a paper that, for the first time in history, made a reasonable estimation for the mass of a single atom: a trillionth of a milligram [he used trillion in the long scale, meaning 1018].

Applying Loschmidt’s estimation to the chessboard, assuming the coin is a solid 8 grams of Au, it could easily be divided 63 times, with still hundreds of gold atoms left even in the last square (8×1021 / 263). There is indeed plenty of room at the bottom, as Dr. Feynman said. Since then, we have of course made more accurate measurements of the atomic mass, but Loschmidt’s estimate was very close to the mark [the actual number of atoms in 8 grams of Au is about 2.4×1022, just three times higher].

We have had the knowledge about the approximate size of atoms for more than 150 years, and have made steady progress in the precision and accuracy of our instruments. But the sight of the apparently empty lower half of the chessboard really demonstrates how much about the physical world is hidden from the senses we were born with.

The gold leafs in squares 38-50 are of the diameter of typical living cells, and visible with a microscope. Optical microscopes become useless pretty soon after square 50, because the diameters become smaller than the wavelengths of visible light. All the complex biochemistry of life, with practically infinite variations of form, happens at a scale too small for us to see. But there is plenty of room for the variations; every view in a microscope is like choosing one asteroid in a galaxy cluster of star systems to look at.

Taking the hint from Feynman, the world-wide electronics industry has proceeded down the ladder, doubling the transistor count of production chips about every 18 months since the mid nineteen-sixties, by miniaturizing components. After fifty years, this so-called Moore’s Law has an unknown future, but the incredible impact to human society of affordable computing has been achieved by traversing just half-way down the chessboard of magnitude.

The problem of accuracy is not just with the instruments used, it is also in the amount of raw data needed to process the information. Every new bit of information doubles the number of possible combinations. To represent measurements of 22 digits of accuracy, for example the recent discovery of gravitational waves, more than 64 bits of precision is needed. For comparison, all the pictures in this post were created with blender, which uses single-precision floats internally, with just 24 bits of precision. This is enough for human vision, and requires less hardware.

Even with trillions of pixels in quadruple-precision accuracy, the human brain would not have the internal bandwidth to grasp both ends of the chessboard of magnitude at the same time. The most common way to display physics magnitudes is to use the zoom effect, as famously done in the Powers of Ten film in 1977. The zoom is a compromise, with the apparent motion as if traveling to other worlds, and no intuitive way to gauge the logarithmic speed of movement; but it seems no better way to convey differences in magnitude has been invented, so far.


What are we made of?

The obvious answer is that we are made of atoms, like everything else physical in the Universe. Some of these atoms were made from other atoms inside stars that then exploded.

This is of course correct, but it misses a lot of crucial points. For example, the atoms in a living body are being continuously replaced with new atoms, a process called metabolism. Like the Ship of Theseus, our bodies are continuously being rebuilt, with none of the original atoms remaining in place.

Not all the atoms in the body get replaced over time. There are things that do not take part in normal metabolism, yet are considered parts of our bodies, like tooth enamel, or the lenses of the eyes. DNA material in post-mitotic cells, like most brain cells of an adult, could also remain essentially the same atoms in the same molecules for decades.

But as the brain is the most metabolically active organ in your body, the atoms that remember an event that happened ten years ago are, for the most part, not the same atoms that experienced it at the time.

Single atoms have no memories, and no identities, only large collections of them do. But not just any heap of matter is alive.

The smallest collection of atoms and molecules that can be said to be alive is the cell. We are made of cells that have grown together, and specialized into the different parts of our bodies. In biological sense, the correct “atom” of the human body is the cell.

But this division is not truly atomic either. We cannot take apart a human at cellular level, and reconstruct him again from individual living cells (By the way, there is one class of animal that can spontaneously do exactly this, the sponge). Individual cells in our bodies are not just in different positions, they are also specialized to very different tasks. Even if all cells in the body shared the same DNA, cellular specialization occurs by turning different genes on and off, based on inter-cellular communication.

Individual cells in our bodies die all the time, and are replaced with new ones. In fact, most of what you see when you look at any bigger animal is the dead tissue covering the surface. Yet the organism lives.

Life is not made or designed, it exists through growth, and refuses to be confined to any single level of definition. As conscious beings we take all the unconscious processes in our bodies for granted. As apex predators, we live on top of a pyramid of life which we mostly take for granted. As social and specialized animals, we live as dependent members of the global economy, which we mostly take for granted.

In the end it makes little difference what parts our bodies consist of at any moment. As growing things our bodies are not finished. Nothing alive ever is.

Sorting trees

The oversized brain of the hunter-gatherer never stops categorizing whatever it encounters, from the moment it is born. In infancy, everything is a surprise and whole new taxonomies get created and destroyed daily. As adults, we are expected to be independent and survive on our own in new situations; it is a common thing that a short time after reaching biological sexual maturity, many humans become suddenly convinced that they know everything they need to know about the world.

These categorizing systems, internal taxonomies if you will, are kind of sorting trees that grow inside the skull. New data enters the main trunk, and through consecutive decisions is routed towards smaller and smaller branches, until there are now more branches. At least, this is conceptually how we think intelligence would work, if it was artificially engineered by us.

The growing networks of trees in our heads are revealed through language. Human natural languages need to be sophisticated, to efficiently transmit the complex multi-level nuances of our internal classification engines. Languages are alive, and any human born today will be immersed in the living linguistic environment of their homes. Through language, both the differences and the similarities of our internal world-models can be exposed.

Words can be set in stone, but language changes constantly. Not just new words are invented; As time passes, old words and phrases take new meanings and connotations, while old meanings are lost or systematically misunderstood.

It is comfortable to think that some inborn building blocks of language are built into the brain at birth; that there is some rudimentary “natural language” common to all humans, that we then learn to fluently translate into the real languages we use. All forests in the world cannot be simplified into just one “true” tree, without losing most of the information. This applies also to the jungle that we call human language: there is no true language able to express everything we use language for.

This actually means more than just spoken language, something that most of us learned before the beginning of our earliest memories. Some exceptional people do not learn language this way, but are still able to “high-function” in society as adults. Even when thinking is mostly visual-sensory, there seems to exist and internal model of the world, with categories and simplifications and associations. Influencing (educating, commanding, negotiating) another mind is just harder without a shared island of language.

As adults, we would like to think that our internal models are fairly correct and consistent. And they are usually good enough for the challenges of normal daily life. That is why it is so surprising to find out that there can be polarizing disagreements on some subjects between otherwise agreeing persons. After all, logic is all about consistency, isn’t it? Perhaps if we lived in a world without surprises, internal consistency of model would suffice. But this is not the case. Sometimes it is necessary to learn to live with paradoxes, or even accept the existence of dialetheia.

Our categories are not naturally exclusive either, they are fuzzy, adaptive and biased in many ways. We humans often desire that our internal categories be clean-cut and exact, and this obsession takes us farther than other animals. By refining categories with ever smaller subcategories, rules of thumb with exceptions, the desire for cleanness leads, paradoxically, to increased complexity.

The internal trees are living things, and adapting on many levels. Languages also evolve, but more slowly. Some computer engineers of the past century (but not Marvin Minsky) may have naively thought that human thought could be replicated by writing a program using logical calculus, and simply run it on a very fast computing machine. Only recently have we started to tentatively adapt our formal models of thought, with fuzzy logic, paraconstistent logic, bayesian inference, to name only a few.

Atoms or gunk? The chessboard rice-halving challenge

We know today that every physical thing consists of atoms, particles so small that we cannot see them with our eyes. The idea of atoms was invented thousands of years before the particles named after them were discovered by scientists. For most people, seeing is believing, so how did the early atomists argue about the existence of the practically invisible?

The numbers of atoms in small everyday objects, like drops of water, are so ridiculously large that the hunter-gatherer mind has no intuitive grasp of them. For example, if I had a gold coin for every atom in one gold coin, they would fill so many olympic-size swimming pools that it would be impossible to walk, or even run, past all of them in a single human lifetime.

Start from the first square, cut the rice grain in half, take the smaller half and move it to the next square. Continue until you have a piece of rice in every square.

An ancient story about grains of rice doubling each step on a chessboard can be changed slightly, so that it is about splitting things in halves, instead of doubling them. All that is needed is a small object, and a sharp knife. Start from the first square, cut the rice grain in half, take the smaller half and move it to the next square. Continue through the squares until you have a piece of rice in every square.

The halving version of the chessboard challenge is much more practical than the doubling challenge, since less rice is needed. It is also quick and easy to perform in practice, and if all the rules are followed (“always take the smaller half”), quite impossible to perform for all 64 squares.

Here is a quick attempt with some modeling clay. After 16 steps, the pieces become smaller than the flecks caught in the knife blade.chessboard1

In theory, it is possible to cut a 1 oz gold coin in half 78 times before reaching individual gold atoms. In practice, filling even the 64 squares of a chessboard would still require more than a steady hand and sharp eye (by square 50 the nuggets become smaller than the wavelength of visible light, making optical microscopes useless). Halfway down the board, the remaining pieces would probably need to be attached to some larger object, to keep them from floating away with other dust. (But when an object is attached to another, do they not then together form a new object? According to atomism, yes they do.)

It is of course much easier to dilute the gold coin with another substance than to cut it into individual atoms. Metals can be worked together by stretching and folding repeatedly, without actually melting them into liquid form. Applying pressure, such as with a smith’s hammer, stretches the material nicely when it is at the right temperature.

This picture demonstrates the principle, again using colored modeling clay. It has a doughy consistency, always somewhere between fluid and solid, and easy to mold with hands.folditIf the component pieces were not consisting of atoms that attach to other atoms, then the process could be reversed, by separating and unfolding, even after being stretched and folded together 16 times, or even 64.

This number of foldings is only possible with a material that stretches, folding a paper more than 7-8 times requires a very large piece of paper. (Baking also provides practical examples of repeated folding and stretching. There is a natural limit to how many times dough can be folded to make the finest noodles.)

The patterns caused by repeated folding and stretching are similar to what can be seen in Damascus or Wootz steel. Although the original methods were kept secret and lost, ingots are usually folded a number of times when worked into a blade. Mixing iron with impurities, mainly carbon, then folding repeatedly produces a material that is stronger than any of its component materials. How can that be explained without atoms?

The historical origin of the game of chess happened in the same place where atomism was first mentioned, somewhere in India. The same region was also first to produce these steel blades, and I wouldn’t be surprised if they also thought of the rice-halving challenge, and presented it as an argument for atomism.

I have no knowledge of any reference to this kind of challenge actually being presented back then, and if anyone reading this can provide links I would be grateful. The closest thing that I know are the various paradoxes of Zeno, where distance or time is repeatedly divided. Zeno does not present his paradoxes in the context of atomism, either for or against. Then again some atomists apply the principle to matter only, and therefore would accept empty space/time as being infinitely divisible “gunk“.

Flow control

From hunters and gatherers to farmers and citizens, we are conditioned to be consumers of continuous physical flows. Water and air, food and warmth, these are just some of the things we need to receive regularly to sustain our existence. Our bodies can adapt to changes in flow to some extent, like a thermostat, but too much or too little of a good thing can still kill us.

Always ready to invent a simple model to explain complex realities, in the past we have explained the workings of the body as a balanced reservoir of essential fluids, or taken to extreme the idea that anything physical can be either poisonous or beneficial, depending on dosage. Although we retain some reservoirs inside, our bodies are primarily not bottles, to be filled or emptied. We are processes, and we must continue to consume as long as we live.

Modern man has learned to store materials outside of his own body. When hunting was unfavourable, and weather destroyed plant life, caches of food would help ensure survival for the tribe. As gatherers collected foods that seem to preserve best, some of these caches of foods will have started growing, all on their own. Curious beasts that we are, we discovered what seeds are, by trial and error.

More and more we relied on stored food, and gradually became obsessed with the logistics of it: How much water is in that waterskin? How much grain can we store in that cave? Can you make those clay pots bigger? Is there a way we could extract just the most nutritious parts of the plant, so we can store more of it in the same volume? And also make it last longer without spoiling? And so on, until most of us forgot that we used to hunt our food in the wilderness.

Resource anxiety, the worry that we might at any time run out of something that we need, has never left us, even though we live in the midst of historical abundance. The precursors of such ideas as ownership, budgets, and trading, might have existed in some form in the tribal era, but it was our transformation to farmers and citizens that made them real.

Economy is all about controlling the flow of goods and consumables. But to properly understand the flow of materials around the world, we need to represent them in a more handy form: currency. Even though we constantly compare incomparables, like apples and oranges at the market, we think we can compare against something that stays fixed and solid: the value of money. But of course there is nothing that is infinitely solid and fixed, all assets can be liquidized, given time.

There is one physical resource that we need to live, that cannot be stored or traded. Even the richest man in the world only has a finite time to live, and the clock ticks for everyone alive. Even though we do not know exactly how much time we have left, we know we cannot live forever.

But flow control is not just about quantitative logistics. By controlling flow as it solidifies, forms and patterns can be stored: Ink flows onto paper and dries, storing words and pictures in solid 2-D form. With some more work, we can cause clay, wax, resin, and various polymers to solidify in a desired shape (with 3-D printers, if nothing else).

Life forms are processes that consume and produce resource flows with intricate, and often efficient patterns. Evolution makes individuals compete on resources, so that natural selection can improve resource usage among the survivors. In the broadest sense, anything that is limited, acts between individuals, groups of individuals, or between them and the non-living environment, can become a contested resource for the purposes of evolution.

A page completely covered in ink is as void of information as one left blank

For example, space for storing patterns can become a contested resource, but how to measure it? It is not possible to optimize for quantity and quality at the same time: a page completely covered in ink is as void of information as one left blank. Shapes cannot be stored from just one resource, at least two are needed, like paper and ink, or wax and empty space.

Life stores its patterns efficiently, in molecules so small we cannot see them with the naked eye. To control its flowing patterns, life as we know it fluctuates somewhere between liquid and solid. DNA is a one-dimensional strand, folded for storage into big 3-D bundles, called chromosomes. The machinery of the cell will unwind these strings regularly for copying, or for protein synthesis.

Grossly simplified, the copying or expressing of DNA is a process of controlled solidification. The surrounding liquid floats abundantly with assorted building blocks, free amino acids or nucleotides. The machinery of the nucleus guides them to connect one after the other in the order determined by the strand being copied, to grow into a long 1-dimensional floating crystal chain, a transcript or copy of the original. After synthesis, proteins twist and fold into space-filling 3-D knotty shapes, to be able to perform their tasks inside or outside the cell.

The inner machinery of the cell is contained inside the cellular membrane, which is a flexible 2-D liquid crystal forming the walls of the cell. Unlike the folding-unfolding 1-D strings inside it, the cellular membrane is not a copy of anything, it is one half of the original membrane that broke in two as the parent cell divided. Like a soap bubble that keeps growing and dividing forever, the cellular membranes inside our bodies are all pieces of a cell that lived and died billions of years ago.

What does change about the walls of different cells is the intricate system of gates and filters straddling it, bundles of 3-D-folded 1-D macromolecules that the cell manufactures. These gates decide what material can flow in or out of the cell. For example, distant parts of a complex multicellular organism can communicate by sending or receiving messenger chemicals via the bloodstream. The immune system can also order cells to stop molecules it considers harmful from entering, by programming the gates in the membrane.

With our mechanistic intuition, we think of gates as solid mechanical objects and flow as matter in a liquid state. These are the kind of machines we build: silicon crystals printed with intricate systems of billions of tiny gates controlling the flow of electricity. Such machines can be very precise and efficient, but they are not very adaptive. We probably expected to find such a mechanistic system inside the cell as well, engineered to precision. That is one of the reasons why molecular biology has baffled our expectations so many times during its short existence.

For example, unlike simpler life forms, most of the DNA in a human cell is not genomic, or blueprints for proteins. Instead we have discovered in the ‘junk‘ parts a complex RNA-based regulation system for deciding what genes the cell should be expressing, and when.

We have also discovered what can only be described as life fragment parasites, lonely strands of macromolecules that travel from host cell to host cell, hijacking their replication systems to produce copies of themselves. Although these parasites usually only harm their host when in the process of jumping from one species to another, we somehow decided to call them viruses, meaning poison. (But as noted earlier, the difference between poison and medicine is dosage, not chemical composition)

Most of the cells in our bodies are not even human cells at all: the colonies of billions of single-cell organisms that live in our gut.

Proteins can apparently also be more dynamic than previously thought. Instead of folding into a deterministic 3-D shape, some proteins that our genes express do not have a native shape, but are said to be intrinsically unstructured.

Misfolded and tangled proteins get produced by our cells all the time, mistakenly or on some not-yet-understood purpose. As these proteins cannot be consumed as signals at their destinations, they accumulate as plaque in our central nervous system, which can be very harmful. But it seems that evolution has already created a mechanism, the recently discovered glymphatic system, that cleans our brains when we are not using them, during the deeper phases of sleep.

All in all, the programming language of life seems more like lisp than Fortran, in that separation between what parts are programs and what parts are data is not clean. Also, a lot of hidden garbage collection seems to be required, to recycle finite resources and thus hide the quantitative flow regulation from the reproducing parts of the organism.

The pressure to separate

We spend our lives pressed against it, and take its stability for granted. To us, Earth is the most solid foundation of all our endeavours. It provides us with various materials to build our tools from, and anchors all our structures. To contain or separate, we use walls, made from the solid substances available to us.

This kind of solidity is useful, but it has limits. Even the most rigid materials will bend and sway like rubber in large scale constructs. To move the Earth, Archimedes would need more than a place to stand on, he would need a lever of supernatural solidity. At large scales, all known materials, even so-called solids, will start behaving like fluids.

The spheroid form of a planet is the result of the fluid-like behaviour of its substance. The surface of the Earth pushes against our feet not because it is so rigid, but because the combined pressure of the planet’s own weight cannot compress the atoms inside to any smaller volume. There is nowhere for the pressure to go except outwards, and by diffusion it all evens out into a spherical form, or actually concentric spheres of different pressures and densities. Pressure increases towards the middle of the planet, up to millions of times normal atmospheric pressure; but at the same time the relative pull of gravity diminishes to none in the middle.

At the surface, where gravity is strongest, the layering is present all around us, even where we do not see it: in the strata under our feet, or above us in layers of clouds moving in different directions. The seas have layers also, with surface currents at odds with deeper ones.

Pressure is nothing more than the combined effect of countless billions of atoms colliding with one another. In free-fall, gravity gives each particle equal acceleration regardless of mass, as famously demonstrated by Galileo. But equal speed gives the larger particle a larger momentum, which is what matters in collisions.

The separation of different materials to concentric layers is the result of the continuous struggle, the harmony of battle lines. The way “up” and “down” is one and the same, only relative to the pressure of the opposing forces. Indeed, many substances circulate endlessly between layers, like the water cycle which we depend on.

"Even the posset separates unless stirred" -- Heraclitus, according to Theophrastus

“Even the posset separates if it is not stirred” — Heraclitus, according to Theophrastus

As it happens, the zero point of gravity is actually never in the exact middle of our planet. The combined center of mass of the Earth-Moon system is inside the surface of Earth, but off-center towards where the Moon happens to be at that moment. As the Earth rotates, the change in direction of the pull of the Moon causes water tides in surface waters, but also tidal movement of the earth itself.

Particles do not have to be invisibly small to behave collectively like a fluid. All that is needed is some way for the particles to flow past each other. When a container of different size objects, such as flour, nuts, or sand, is jostled or shaken, the contents get shifted so that the larger pieces are on top, and smaller ones at the bottom. Continuous vibration helps overcome static friction, but the resulting fluid is still quite viscous. It should be noted that with these kind of every-day particles, the size of the container relative to particle size would be called capillary with molecular fluids.

"Even mixed grain separates when vibrated"

“Even mixed grain separates if it is shaken” — Heraclitus paraphrased

In our solar system, we can see an even more spectacular example of solid objects arranging themselves to concentric layers over time: the rings of Saturn. In space, particles do not need to actually touch to interact with each other, they can affect each other’s orbits just by passing closely.

Substance and Form

As generalists, we constantly interpret our sensory inputs, improving on our raw senses by relying on our internal model of the world. In our mind’s eye, we typically model the physical world as objects, of various materials and shapes.

In addition to our senses and our big brains, we are uniquely equipped with hands, with which we interact with the various objects that surround us, from the moment we are born. Our hands can turn things around, bring them closer to our eyes or nose, hold them still, or discard them when they no longer hold our interest. We can use our hands to point to the thing that we are talking about, cup water in them, throw and catch objects, dig. Once we have learned to use our hands, they become almost thoughtless extensions of our will in the world.

With our hands, we can change the shape of objects. Cave paintings, bone flutes, stone tools have been discovered, tens of thousands of years old, much older than recorded history. And no doubt most of what we created then has not survived the ages: most pliable materials available, such as wood, leather, feathers, hair, will have rotted long ago and lost its form.

Any ethnographic or anthropological study of the different human tribes reveals the bewildering variety of shapes and forms that humans pose, even on their own bodies. Clothes, dyes, jewellery are a given in any society, visible embodiments of the social drive of humans. But more permanent modifications to the body can also happen, like ornamental scarring or filing of teeth, and even dangerous adjustments of the growing skeletal structure like skull-binding or neck-stretching.

It is natural for us to understand the world in terms of hylomorphism: Take a piece of some readily available material, like wood (hyle), and work (morph) it until it looks like some other object. All things that are real and physical are always combinations of material and form. In other words, matter cannot appear out of nowhere, nor disappear; it can only change form.

The internal model of the world inside the human mind is of course not subject to these restrictions. In the mind’s eye we can easily separate the shape of an object, or the properties of materials, from an object, and regard them as abstract categories of existence. An important feature of the internal model is the ability to consider possibilities that are not actually present. For example, to successfully craft an object to a desired shape we need to have some kind of a plan or idea of how it should look when it is finished.

Now in the 21st century, we can use computers to create just about any object we can think of, from a city to a molecule, view its shape on the screen while doing so, try on different materials and arrangements until we are satisfied; before sending it to a fab, perhaps on the other side of the planet, to be “3D-printed” into an actual physical object. We are not yet even close to the accurate placement of individual atoms in the manufacture of molecules, and we don’t entirely understand how arbitrary DNA might fold into a protein, but these and other details are being worked on.

Since we can use information technology to manipulate non-existing objects, and transmit their shape to the other side of the world, it would seem that information has consumed the ‘form’ part of hylomorphism. In a larger sense, the blueprints of the objects we can manufacture can also be considered mathematical formulas, or some extended category of language. In practice, digital information can be used to represent both.

The part of ‘hyle’ is played by energy in modern physics.

The part of ‘hyle’, the primary substance of all physical objects, is played by energy in modern physics. The quantity of energy in a closed system is constant, only its form can change. All matter is composed of elementary particles, quantums of energy with either mass-like or radiation-like appearance (or both).

Even with these modern refinements, the basic paradigm of hylomorphism stands: in the physical world, substance and form are always intrinsically entangled. Even though it seems that the information we store on a computer and transmit across the globe is completely immaterial, in practice the process of reliably storing or transferring digital information always consumes energy, our new hyle, in some form and quantity.

Galaxies in bullet-time

Our ancestors, lacking artificial lights and thus light pollution, would have seen the stars in the sky more clearly than most people today can. A few of them would have seemed to move continuously, what we now call planets, but most of the stars were fixed, never moving from their place in the solid, rotating canopy. Apart from the occasional falling meteor or comet, this wonderful canopy of stars would remain the most constant and unchanging part of their world.

The canopy itself is for the most part darkest black, with some lighter smudges in places. In tribal legends, some anthropomorphic invisible giant would have spilled milk while moving over the perfectly black background, creating what we still call the Milky Way.

the flowing movement that we intuitively recognize in the spilling of the Milky Way never stopped

Since then, we have discovered that there is no solid canopy, and the stars are not fixed to anything at all. The universe by and large is not solid, and the flowing movement that we intuitively recognize in the spilling of the Milky Way never stopped, it is ongoing and continuous.

Perspective affects the way we perceive motion. To a human child looking up, a flying bird seems faster than an airliner, when in fact a jumbo jet is hundred times bigger than the bird, flying hundred times faster, hundred times more distant. Our senses are simply not equipped to grasp how big and how distant the objects we see in the night sky really are.

Even though the stars are actually moving faster than any bird or aeroplane, they are so distant from us that their angular velocity is negligible from our point of view. Luckily, they are also bright enough to shine over the vast distance, serving our ancestors as beacons to navigate their vessels; although the beacons were in fact moving faster than the vessels.

Everything in the sky is falling. But because there is no universal “down” or “up”, objects either fall in all directions, possibly colliding with others, or end up falling round and round each other, in rotating patterns.

Turbulent flow produces cloud-like shapes that we recognize, in vastly varying scales of magnitude, provided that the timescale is suitable. Stellar nurseries, planetary nebulae, supernova remnants, all have provided spectacular images through modern telescopes. The original exposure times have been in minutes, and many of the famous images are also false-color combinations of several exposures at different wavelengths. Yet these images look to our eyes more like short exposures of flow on Earth, than long exposures, because of the difference in scale of the flow.

Based on these astronomical images, special effects artists have produced dazzling visualizations of galaxies and nebulae, for TV shows like “Cosmos: A Spacetime Odyssey”. To break the illusion of a fixed 2D canopy, zooming into a static picture of the sky has been replaced with flying the camera into a computerized 3D model of a galaxy. This apparent motion can make the size of these celestial objects more magnificent to the human viewer, but the timescale of these fly shots is problematic.

Movement of the camera usually implies passing of time. When the imaginary camera slowly flies into the computer model of a galaxy, it moves the equivalent of thousands of light years a second. Yet the computer simulation of the galaxy in these shots is as static as the astronomical images they are based on, with no movement in the relative positions of the stars. The resulting fly shot looks as artificial as bullet-time, a galaxy frozen in mid-sneeze, with only the camera capable of any motion.

If instead the computer simulation was good enough to realistically animate long-term changes within the galaxy, time could be shown at the same enormous scale as distance in these computer generated shots. By compressing tens of thousands of years of galactic evolution into a few seconds, while the camera moves tens of thousands of light years, the fly shots would certainly look more lively. The apparent speed of ten thousand years a second would be long enough to make visible the proper motion of all the stars, along with multiple exploding stars, sparkling along turbulently flowing spirals. Like in the solar system, the fastest motion would occur near the center of the galaxy,  blurring the orbits of star systems into lines. At this timescale, a galaxy might resemble a cyclonic storm of sparkling fire.

It is unfortunately not possible to say how realistic such an animation would actually be. We humans have known about the existence of galaxies outside of our own for about a century now, so we cannot have any long-term data about how galaxies change. We don’t even know for certain how galaxies came to have the different shapes they do, and can only make plausible guesses. It also does not help that our current physics fails at simulating galaxies with any stability unless fudge factors are used.

Everything flows

On those stepping into the same river, ever different waters flow.

— Heraclitus of Ephesus

a flowing riverTaking a photograph of flowing water, so that it can be recognized as such, is not as simple as it may seem. A good rule of thumb that photographers use is that the exposure time should be somewhere between 1/100 and 1/20, to depict movement convincingly in the resulting image. A patient photographer will try several test shots with different exposure times, in order to achieve the wanted effect.river5river6

When the exposure time is too long, half a minute or more, instead of water the photograph will show heavy, oily fog creeping over the landscape. If the exposure is too short, in millisecond range and under, individual droplets float crisply in mid-air, and the viewer cannot tell where they came or where they are going.river4Only in the middle exposures, here at 1/100, we immediately see that the water is flowing from right to left.

Come to think of it, why should any still image be interpreted by the viewer’s brain as depicting motion? Is 1/20-1/100 the most natural exposure range because it corresponds well with the gamma wave frequency of the human brain?

In the real world, as revealed by modern physics, solidity is the illusion, not flowing movement.

In the real world, as revealed by modern physics, solidity is the illusion, not flowing movement. Every part of the world is in constant motion. What we sense as solid objects are in reality a hypermassive clouds of electrons and ions orbiting each other at ridiculously high speeds. Human cognition happens millions of times slower than electrons flow, giving plenty of time for random opposing fluctuations in their movements to cancel out, like individual droplets of water that disappear in the long exposure photograph. Because we experience time at a rate that is massively slower than the speed of elementary particles, we see only the stable overall shape of the object.

Movement is relative, we can measure the movement of individual droplets or particles only against a “solid” object. “The same river” is just the pattern of moving water that is stable enough for us to draw it on maps, even though it is formed from ever new water, rained down from ever new clouds. Raindrops and clouds are not drawn on maps, they are not solid enough at human perceptual timescale.