Theatre, Stage, Actors and Eyes
It is time to break down the ground covered so far into a series of prerequisites for and interconnections between the cosmological, biological and sentient dimensions of our lives in ways that help to place visual perception in context.
The building blocks introduced already mark out large-scale connections between our contemporary everyday experience and the most distant reaches of space and time. To conceive of this sense of connection from the largest to the smallest scales has required massive feats of imagination and has drawn on the genius of some of the world’s greatest minds including familiar names such as Charles Darwin, Albert Einstein and Stephen Hawkin among many others. But today, appreciation of the structural interconnections between the Big Bang and the world as we see around us is in evidence wherever concepts such as universe, cosmos, evolution, and emergence are found. Whilst each one of these has already been used in previous sections, let’s summarise each in turn as we get down to the business at hand.
The Universe includes the whole of space and all forms of energy and matter. In more descriptive terms we can talk about the totality of existence, which is to say everything that exists now, plus everything that has existed or will exist. The inclusion of thoughts, emotions, feelings and physical sensations add a human sense of scale.
The term cosmos treats the Universe as complex but orderly inter-related systems. It implies the accumulation and variation of generative and developmental changes over time in the composition and assembly of radiation, matter and life, including humankind. What Neo-Darwinism does for the biological evolution of plants and animals and their intimate interconnections, cosmic evolution does for larger categories and entities. Cosmic evolution provides a continuous framework within which to consider the systemic properties and sequential relationships between the describable properties of the universe.
Cosmic evolution might be broken down into sub-divisions such as the following:
- Evolution of primal energy into elementary particles and atoms
- Evolution of those atoms into galaxies and stars
- Evolution of stars into heavy elements
- Evolution of those elements into the molecular building blocks of life
- Evolution of those molecules into life itself
- Evolution of advanced life forms into sentience
- Evolution of intelligent life into cultured and technological civilizations.3
To provide a sketch suited to present purposes it is sufficient to simplify the overall span of these divisions into just three eras:
The era of matter begins with the emergence of space-time, as discussed above. It encompasses the period during which elementary forms of matter became evident and includes their progressive differentiation and chemistry. This era is inclusive of the appearance of the first stars and of all the properties of the Universe we see and study in astronomy and the other physical sciences.
By comparison, the era of life is a more recent phenomenon. Life, as we know it, is very localised but forms an overlay of properties both dependent on and distinct from matter. Life has emerged, flourished and evolved the ability to entirely reshape and add novel properties to its material origins.
What might be called the era of sentience, includes but is not limited to our very anthropocentric sense of things. It emerged only recently compared to the overall duration of the eras it overlays. The speed and degree to which sentience has gained sway over both the material world and life accounts for the introduction of a new geological term, the Anthropocene. It is from this location and with the aid of its emergent properties that we trace our cosmic heritage – its origins, chains and sequences of events, and a virtual blueprint that maps our survival over time.
In what may seem to be an unreasonably ambitious task, let’s try to treat the notion of life to the same scrutiny.
Life is in addition to the ways matter differentiates itself, it is energetic, material and chemical but has properties that cannot be accounted for in those terms alone. Life, in this sense, is a process internal to matter, not a force or a property applied from outside in the way strings are used to manipulate a puppet. Life is then not a vital force but rather a supplementary property inherent to matter.
Life differentiates itself from nature from within, a dynamic self-containment functioning across a porous boundary. It feeds upon and feeds back into its surrounding. It folds materials and their chemistry into itself, whilst unforeseen properties emerge that it uses to continue the process, folding within folds. Life in this sense can be understood as parasitic on matter as it draws from its chemistry the forces and information it needs to reproduce the impetus to persist, so exist. Living things are all variations of life, each one uniquely different from another and in every case able to adapt to or re-adapt its material conditions, regenerating itself from within before its wilfulness is exhausted. The common impetus all its forms carry is that of materiality itself, the capacity to extend the extant, to reach out and recreate itself in new and unforeseen forms.
Sentience supplements life and inorganic matter just as matter supplements space-time. But running in the other direction, space-time is meaningless without matter to fill it. So equally, space-time, the inorganic and life are all meaningless without sentience. So with sentience comes yet another supplement, meaning itself.
Now let’s put this framework into effect.
It helps if we think of human life as a play. Here we are, living out our lives and getting on with things as best we can. Then there is the stage on which we find ourselves – the natural world and our ecological niches within it. Housing all that is the theatre.
Electromagnetic radiation preceded the formation of the first stars. What we call the Cosmic Microwave Background was the first manifestation of light and the first evidence we have of its earliest workings. For this reason, light is enmeshed into those laws of physics that help us account for the consistent forms and properties of the heavens across all space and time.
The fact that photons of light began to escape the preceding torrid, isotropic mass of super-dense plasma and traverse the empty spaces between emerging atomic structures accounts for the fabric of space-time. Both space and time are the fundamental prerequisites for a material Universe. All forms of matter, including every living thing, must have geometric coordinates and be capable of negotiating trajectories between things if they are to exist, and this is exactly what space-time provides. Space-time is the dynamic theatre that determines the physical and temporal dimensions of the stage on which we find ourselves and thus the locations from which we participate in the play into which our lives are woven. Each of us is in that sense an actor, swept forwards by the tides of time, caught in the action as things emerge, evolve, change and become different.
It would be billions of years after space-time emerged that sentient creatures evolved on planet Earth able to reflect upon their place in this matrix and trace its history back over aeons. But eventually, generations including our own, can see and consciously appreciate that our very existence is predicated upon conditions that began to emerge in the earliest phases of the evolution of the Universe. How remarkable that we can describe ourselves in these terms!
Another crucial detail, if we are to properly account for ourselves as sentient, concerns our bodies and their existence among other things. In other words, what are the preconditions for the embodied existence of anything? As we extrapolate the inter-connections between light and vision, we need to keep in mind this very material fabric of our existence! To grasp this, we must target the physical matter that everything from our own diminutive skeletons to the celestial bodies above our heads is constructed from.
All of the material mass of matter in the universe emerged along with the massless energy of the Cosmic Microwave Background. CMB radiation was emitted as atoms of hydrogen and helium formed. Initially, these were the only forms of matter and even today, hydrogen is the most abundant element in the Universe. Because of their mass, hydrogen atoms began to clump together under the effect of their own gravitational attraction forming sheets, walls and filaments, separated by immense voids, creating the vast structures sometimes called the cosmic web.
As ever-larger quantities of hydrogen were drawn together, gravitational attraction increased, accelerating great clouds into every smaller and hotter regions until the first stars and galaxies were born. Stars are balls of burning matter undergoing nuclear fusion within their cores and forcing atomic nuclei to fuse and produce new, heavier elements. During the fusion of two hydrogen nuclei to form helium, for example, a little less than one percent of their mass is emitted as energy. This process, which continues today, is the source of all the light that overlays the CMB. Within our own solar system, it is this same process of fusing hydrogen nuclei that releases the radiant energy that bathes our world in light every day.
The Periodic Table. Ninety-four elements occur naturally and combine to produce the world around us. The lightest by atomic weight is hydrogen and the heaviest is plutonium. Credit: Adapted from https://commons.wikimedia.org/wiki/File:Periodic_table_large.svg
Whilst the first stars were composed solely of hydrogen and helium, the rest of the elements found in nature are the result of nuclear fusion within later generations of stars and from catastrophic stellar explosions known as supernovae. The most common elements, like carbon and nitrogen, are created in the cores of all stars as they age, the ageing of larger stars produces heavier elements such as iron but it is supernovae that produce the remainder of naturally occurring elements seen in the Periodic Table.
During the greater part of their lives, gravity pulls the contents of stars together whilst fusion pushes them apart. The two balance each other perfectly until fusion stops. When stars over a certain size run out of fuel it causes the outer layers to explode and the core to implode producing a core-collapse supernova. It takes about a quarter of a second for the entire core of a sun to collapse in on itself in this way. The massive increase in pressure in the extreme conditions of this type of supernova adds new and even heavier elements to the list – cobalt (Cb) to plutonium (Pm). As well as immediately producing massive pulses of light that can outshine a whole galaxy in an instant, their remnants spread far and wide to seed the formation of new generations of stars.
Without preceding generations of stars and supernovae, planet Earth would be a very different place and life as we know it would not be possible. Without all the naturally occurring elements of the Periodic Table, there would be no rocky spheres like our own, only gas giants like Jupiter and Saturn – no seas, no mountains, no solid core, and no bodies. We need all the elements within our atmosphere to breathe. We need carbon to build bones. Our blood has iron in its haemoglobin which carries oxygen to every single cell. Nitrogen enriches the soil and is a vital component of chlorophyll. Chlorophyll, in turn, is the compound by which plants use the energy provided by sunlight to produce sugars from water and carbon dioxide (photosynthesis). Nitrogen is also a major component of amino acids, the building blocks of proteins, and without them, plants and bodies wither and die.
To fully appreciate the materiality of our bodies we must remember that the idea we are stardust is not just a poetic metaphor. The entirety of our solar system is composed of material from the cosmic web and past generations of stars. Every atom in our human frames has an extra-terrestrial origin. And when people muse about whether there are aliens out there in space, they forget that our bodies are where the real aliens are hiding. Its just that the aliens are the building blocks of every molecule and compound from which each of our organs and sinews are constructed. But whilst the matter that forms the bodies we live in is extra-terrestrial in origin, there is, as yet, no compelling evidence that life itself originated elsewhere.
Bodies, beings, organisms, entities, and multicellular life-forms, these are some of the names we give to the living creatures we share our bio-physiology with. Every plant and animal is distinguished by an individual material existence bounded by birth at one end and death at the other. This is life as we know it, and every instance represents another extension and elaboration of matter and energy. All the different things living organisms do with light account for the sheer abundant volume of our shared biosphere, its spread, diversity and evolution. We must look once again to light to account for the animation of matter, the emergence of life and for our entire biosphere. It is photosynthesis that has been at the heart of that interface for the last 4.6 billion years.
Life has been shaped and driven by photosynthesis and it forms a key part of the root of life’s family tree. Photosynthesis harnesses the electromagnetic energy carried by photons of sunlight and turns it into chemical energy. There are two types, oxygenic and an-oxygenic photosynthesis. The general principles of both are similar, but oxygenic photosynthesis is the most common and powers all plants, algae and cyanobacteria.
Chlorophyll within leaves and stems of plants absorbs the light and synthesizes carbohydrates such as sugars using carbon dioxide and water drawn from the environment. Different wavelengths within the visible spectrum, corresponding with particular colours, play an important role in photosynthesis but plants don’t absorb all colours evenly. Chlorophyll absorbs violet-blue and red but all green wavelengths are reflected, hence the apparent greenness of nature.
If evolution hadn’t come up with photosynthesis, there would be no oxygen in the atmosphere, no protective ozone layer above it, and probably no life on dry land. Planet Earth minus the intervention of photosynthesis would be anathema to the higher life-forms around today and would be populated only by primitive bacteria in oceans or deep in the soil.
Since the advent of photosynthesis, organic life and the planet have co-evolved. Forests turn to coal. Seashells turn to limestone. Plants draw the nutrients and water they need from the soil. Even plate tectonics may play a critical role in nourishing life. Organisms and bio-systems draw upon what remains of the light absorbed by the generations of life-forms that have preceded them. The continuity and unity of life that we know today is evident in the uniformity of genetic systems, the molecular composition of living cells and the chemistry that folds in and out of living things.
But it seems that photosynthesis has its limits. Is there a boundary in terms of complexity and the concentration and transmission of information that plant-life cannot achieve? Animals don’t produce chlorophyll, nor do they rely on photosynthesis for energy. All observable forms of sentience and self-awareness fruit on the higher branches of our evolutionary tree and it is up there that we find animals with eye holes.
|4.6 billion years ago||Earth forms|
|3.4 billion years ago||First photosynthetic bacteria appear|
|2.7 billion years ago||Cyanobacteria become the first oxygen producers|
|2.4 billion years ago||Earliest evidence (from rocks) that oxygen was in the atmosphere|
|1.2 billion years ago||Red and brown algae become structurally more complex than bacteria|
|750 million years ago||Green algae outperform red and brown algae in the strong light of shallow water|
|470 million years ago||First land plants – mosses and liverworts|
|200,000 years ago||Homo Sapiens|
Photosynthesis has played a central role in the evolution of life. (https://en.wikipedia.org/wiki/Evolution_of_photosynthesis)
New connections between light and life emerged along with the animal kingdom. Even though the kingdom is diverse, animals share common features that distinguish them from other organisms. Animals are incapable of photosynthesis but rely wholly upon it as they ingest living or dead organic matter and each other. Almost all animals have specialized tissues that form organs not least of which is the central nervous system. Offspring pass through developmental stages that establish a determined body plan, unlike plants, for example, in which the exact shape of the body is indeterminate. At one end of every animal body is the head where the nervous system is most densely concentrated and from which cords of neurons extend towards the surface breaking out into a profusion of light-sensitive tips. It is as if the central nervous system reaches outwards to sense the world beyond itself, but not just to see its surroundings but also to search for some evidence by which to account for its own existence.
In On the Origin of Species, Charles Darwin noted:
How a nerve comes to be sensitive to light, hardly concerns us more than how life itself first originated; but . . as some of the lowest organisms . . are known to be sensitive to light, it does not seem impossible that certain elements . . should become aggregated and developed into nerves endowed with this special sensibility.
Some of the early forms of eyes looked like small spots before evolving into concave cups and then developing lenses and so a more successful and competitive organ for sight. The process probably required 364,000 generations, so as short a period as half a million years. Our eyes are exactly tuned to respond to the band of energy between red and violet that can make its way through the atmosphere. It is this same range of wavelengths that powers the entire canopy of life that covers the planet on land and at sea. When light strikes a photo-sensitive rod or cone cell in the retina of the eye, it releases energy and triggers a chemical reaction which in turn produces an electrical impulse that, after processing, is transmitted to the brain. It seems likely that from the moment the chemical reaction begins that the energy received contributes in one way or another to visual perception and, in humans so to conscious experience. Initially, eyes probably could distinguish between light and dark. But it is theorised that the prototypical ability to distinguish between organism and environment may have also been an early function.
If you have seen the film 2001: A Space Odyssey you will have your own conception of the point at which animal species began the long haul from the distant reaches of sentience towards tools, artefacts and images – the right of passage to the last in our series of prerequisites for and interconnections between the cosmological, biological and sentient dimensions of our lives that helps to place visual perception in context. Imagination!