"Considering a sentient species which is at the physical scale of chemical molecules, what would their higher limit of observation be?"
This sentient species survives at the molecular scale and is capable of manipulating their environment by ingesting/ engulfing their environmental molecules and electrodynamically manipulating them with other chemical resources available within them, basically like a sentient cellular organism but it is not cellular, it is an alien ensemble of several chemicals that come together.
Given this species has the "chemical" tools at it's disposal, I'm thinking it is capable of manipulating molecular structures to tinker light-matter interactions (photons and electrons).
How far would this species be able to observe their concept of the "Universe"?
I assume it would depend on the local environment (whether the optical paths are scattered/ diffused) and the information storing capability (assume the sentience stores information in chemical compounds/ chirality/ dipoles/ molecular resonant vibrational frequencies/ larmour precession factors/ collective angular momenta of electrons in a bond etc. other suggestions?)
Thank you for this question, as I feel it has merit not only in literary works intended for entertainment and amusement but also in various fields of medicine and hints (albeit peripherally) at my own (IRL) research.
Technically speaking, such a species could have as its upper limit of perception whatever is the upper limit of reality; stated differently, such a species could have no arbitrary maximum limit to its perceptions; however, such interpretation and answer both involves and is dependent upon collaborative communication between individuals within the species.
How closely do you want this organism to approximate biological reality?
Much of what you intimate in the first explanatory paragraph is already well understood to involve sensing and subconscious responsive mechanisms; in other words, sentience exists on a level profoundly more simple than is required for even the most rudimentary form of intelligence.
Let's thusly restate your question: "For a sentient species which is at the physical scale of chemical molecules, what would be the higher limit of observation?"
In order to understand the OP's question, we must first answer several related other questions; to wit:
[don't worry: I'm not going to use sources likely beyond the ordinary reader's understanding]
1. "What is a species?"
(Google) "noun // 1. // BIOLOGY // a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding. The species is the principal natural taxonomic unit, ranking below a genus and denoted by a Latin binomial, e.g. Homo sapiens."
The article at Wikipedia is informative beyond a simple definition as might be found in a dictionary; a partial quote of which reveals:
"In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity.
A species is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction.
Other ways of defining species include their karyotype, DNA sequence, morphology, behaviour or ecological niche. In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined."
"While the definitions given above may seem adequate at first glance, when looked at more closely they represent problematic species concepts.
For example, the boundaries between closely related species become unclear with hybridisation, in a species complex of hundreds of similar microspecies, and in a ring species.
Also, among organisms that reproduce only asexually, the concept of a reproductive species breaks down, and each clone is potentially a microspecies.
Although none of these are entirely satisfactory definitions, and while the concept of species may not be a perfect model of life, it is still an incredibly useful tool to scientists and conservationists for studying life on Earth, regardless of the theoretical difficulties.
If species were fixed and clearly distinct from one another, there would be no problem, but evolutionary processes cause species to change continually, and to grade into one another."
It would be helpful if the omniscient thought police would reveal to everyone exactly what they believe is meant by the OP, but I doubt they know anything at all, except how to hate and how to wrongly blame others for their own ignorance and prejudice. We shall see whether my suspicion is correct.
2. "What is sentient?"
Webster defines sentient as "responsive to or conscious of sense impressions."
The article on sentience at Wikipedia thus begins:
"Sentience is the capacity to be aware of feelings and sensations. The word was first coined by philosophers in the 1630s for the concept of an ability to feel, derived from Latin sentientem, to distinguish it from the ability to think. In modern Western philosophy, sentience is the ability to experience sensations."
Importantly, the definition in the dictionary does not require consciousness or anything properly resembling actual thought; for example, reflexive responses prove sentience, but do not involve the brain or any complex neural pathways or structures in the generation of the reflexive response.
3. "What is meant by the phrase 'at the physical scale of chemical molecules?'"
To understand this question, we must first answer two questions: (a) "What is meant by the term 'physical scale'" and (b) "What is meant by 'chemical molecules?'"
As the term 'physical scale' seems to have no formal definition readily available, I propose that it combines the meanings of the words from which it is formed; to wit:
"physical" refers to the natural world, and in the OP's usage, it may additionally mean somatic; and
"scale" — in the context herein used — apparently refers to the relative magnitude of the dimensions describing an object.
Thus, the OP is asking about the perception limits of a (hypothetical alien) sentient organism — in one or more of its measurable corporeal dimensions approximating — one or more "chemical molecules."
A molecule is one or more atoms existing as an electrically neutral group; in the case of polyatomic molecules (viz.: molecules comprised of two or more atoms), the atoms of the molecule are held together by chemical bonds:
A "chemical molecule" is therefore any molecule comprised of one or more atoms.
Why is this problematic?
A molecule (or a "chemical molecule") is not a standard unit of measure. Having an atomic radius about 3.10E-11 meters, the smallest molecule is (naturally monatomic) helium (He); however, at roughly 2.016 grams per mole, the least massive molecule is (naturally diatomic) hydrogen (H₂).
Obviously, the OP intends by "chemical molecule" something larger than either of these; however, we have no useful specific guidance to determine the upper limit of what the OP intends by "chemical molecule."
Arguably, the OP either did not contemplate an upper limit or deliberately avoided imposing an upper limit, whether for ignorance or in order to solicit answers providing the greatest reasonably plausible extreme upper limit;
regardless any opinion or perception regarding the intelligence and sophistication of the OP, the latter explanation seems the more likely case, as evidenced in the fact that the OP specifically declared that the question is intended to identify the extreme upper limit
(of sentient perception in — viz.: "characteristic of" — the alien species subject of the OP's inquiry). Therefore, we should ask neither "What is the smallest molecule," nor "What is the average size of a molecule," nor "What is the median size of a molecule?"
Competence in the formulation of an answer to the OP's question both indicates and requires that our inquiry must begin with the largest molecule, and —
because of the context provided in the OP's supporting material regarding the OP's request — we should limit our examination of molecules to only those that are stable.
"PG5" is a fifth generation dendronized polymer comprised of about 17 million atoms: it is an extremely large molecule (a host of sources from 2011 announce that PG5 was then the largest stable artificial molecule ever assembled;
PG5 has a mass about 2.00E+8 grams (200,000 kg) per mole, or roughly 3.3223E-16 grams [0.33223 fg (femtograms)] per molecule; each PG5 molecule is roughly cylindrical in form, has a diameter about 10 nm (nanometers) and has a length of "up to a few micrometers."
Larger non-artificial molecules exist (A beryl crystal measuring 18 meters long, 3.5 meters diameter, having an estimated volume of 143 cubic meters and an estimated weight of 380,000 kilograms is the largest documented mineral crystal);
However, given the focus of the OP's inquiry, PG5 seems to provide the least unreasonable starting point presently available for establishing the approximate size of the proposed "molecular-scale" organism.
4. "What is meant by the phrase 'higher limit of observation?'"
Both the supplementary information provided by the OP, and the question asked by the OP, strongly suggest the phrase 'higher limit of observation' is a term offered in contradistinction to the term 'lower limit of observation,' therebetween and including such limits being the entire range of perception available to the organism
(or, in the case of the OP's question, "species"); "upper" indicating physical maxima, and "lower" indicating physical minima.
Three responses are immediately apparent:
(a) The "Smart Alec's" answer:
"It's science fiction: the limits are whatever you want them to be."
(b) The answer limited only by physics (which answer is mostly not helpful):
The reason why this is not particularly helpful is not easily expressed when we're talking about complex multicellular organisms; it is vastly more difficult to explain when the subject is a subcellular arrangement of chemicals that may not initially (or ever) be recognized as an organism.
To illustrate, these are the most basic requirements for organic life (viz.: for something to be perceived as being an organism, it must demonstrate these characteristics):
All living organisms have certain characteristics that distinguish them from non-living forms. The basic processes of life include organization, metabolism, responsiveness, movements, and reproduction. In humans, who represent the most complex form of life, there are additional requirements such as growth, differentiation, respiration, digestion, and excretion. All of these processes are interrelated. No part of the body, from the smallest cell to a complete body system, works in isolation. All function together, in fine-tuned balance, for the well being of the individual and to maintain life. Disease such as cancer and death represent a disruption of the balance in these processes.
The following are a brief description of the life process:
At all levels of the organizational scheme, there is a division of labor. Each component has its own job to perform in cooperation with others. Even a single cell, if it loses its integrity or organization, will die.
Metabolism is a broad term that includes all the chemical reactions that occur in the body. One phase of metabolism is catabolism in which complex substances are broken down into simpler building blocks and energy is released.
Responsiveness or irritability is concerned with detecting changes in the internal or external environments and reacting to that change. It is the act of sensing a stimulus and responding to it.
There are many types of movement within the body. On the cellular level, molecules move from one place to another. Blood moves from one part of the body to another. The diaphragm moves with every breath. The ability of muscle fibers to shorten and thus to produce movement is called contractility.
For most people, reproduction refers to the formation of a new person, the birth of a baby. In this way, life is transmitted from one generation to the next through reproduction of the organism. In a broader sense, reproduction also refers to the formation of new cells for the replacement and repair of old cells as well as for growth. This is cellular reproduction. Both are essential to the survival of the human race.
Note that in the "non-cellular chemical alien life-form," this concept would still apply, if only in the sense of repairing damage to the organism; however, such an organism could mutate, evolve and devolve — conceivably, countless times within a single generation; in the span of minutes or hours, its mass could change up and down by several orders of magnitude — so, regardless whether it reproduces in the sense of procreating through division or some other process, it must have the survival capability of repairing incidental damage to itself.
Growth refers to an increase in size either through an increase in the number of cells or through an increase in the size of each individual cell. In order for growth to occur, anabolic processes must occur at a faster rate than catabolic processes. [addressed earlier, elaborated here]
Differentiation is a developmental process by which unspecialized cells change into specialized cells with distinctive structural and functional characteristics. Through differentiation, cells develop into tissues and organs.
Respiration refers to all the processes involved in the exchange of oxygen and carbon dioxide between the cells and the external environment. It includes ventilation, the diffusion of oxygen and carbon dioxide, and the transport of the gases in the blood. Cellular respiration deals with the cell's utilization of oxygen and release of carbon dioxide in its metabolism.
Digestion is the process of breaking down complex ingested foods into simple molecules that can be absorbed into the blood and utilized by the body.
Excretion is the process that removes the waste products of digestion and metabolism from the body. It gets rid of by-products that the body is unable to use, many of which are toxic and incompatible with life.
The ten life processes described above are not enough to ensure the survival of the individual. In addition to these processes, life depends on certain physical factors from the environment. These include water, oxygen, nutrients, heat, and pressure.
Granted, the material presented from the link is intended to inform regarding extant cellular life originated on earth; however, the underlying principles nevertheless apply.
The morphogenetic characteristics of an alien organism such as the one postulated by the OP are such as to present an incredibly complex and perhaps unsolvable matrix of iterative forms: the proverbial "blended frog" has all the right ingredients in all the right quantities and proportions, but it will never again live.
(c) The "Goldilocks" Answer:
We can begin by assuming that the proposed creature has a range of perception in some or another way similar to that of organisms native to earth and having the approximate same body plan, mass, linear and volumetric measurements.
Alas, the proposed creature seems to be amorphous, which complicates the matter somewhat: the measurement least likely to be unreliable, by which the proposed alien species can be characterized, is mass; however, as previously mentioned, even mass is unlikely to be truly definitive.
In sci-fi plots, such assumptions usually have fatal consequences; nevertheless, humans in real life tend to rely on the notion that evolution has done the intellectual "heavy lifting" for them.
WHEREFORE PREMISES CONSIDERED
Witness the following quote from the Encyclopedia Britannica (edited for paragraph length; numbers formatted for consistency):
The smallest free-living cells include the pleuropneumonia-like organisms (PPLOs). Whereas an amoeba has a mass of 5.00E−7 gram (2.00E−8 ounce), a PPLO, which cannot be seen without a high-powered electron microscope, weighs 5.00E−16 gram (2.00E−15 ounce) and is only about 100 nanometres across.
PPLOs grow very slowly. Other, even smaller organisms that grow even more slowly would be extremely difficult to detect. An organism the size of a PPLO that has room for only about a hundred enzymes depends entirely upon the animal tissue in which it lives.
A much smaller organism would have room for many fewer enzymes. Its ability to accomplish the functions required for autopoiesis in living systems would be severely compromised.
Were there, however, an environment in which all the necessary organic building blocks and such energy sources as ATP were provided 'free,' then there might be a functioning organism substantially smaller than a PPLO.
The inside of cells provides just such an environment, which explains why infectious agents, such as prions, plasmids, and viruses, may be substantially smaller than PPLOs. But it must be emphasized that viruses and their kin are not, even in principle, autopoietic."
The contemplated alien organism might therefore exist in a profound variety of organizational states, and some of its environment might include relatively fungible modular chemical aggregates — any particular one of which (a) might ("or might not") be sentient, and (b) might ("or might not") enable or provide gain of function.
It is not necessary for such a species to have evolved in symbiosis with one or more others: it could provide every necessary mechanism and process except for the generation of energy; however, the combination of solar energy and geological processes should suffice for all that.
Such a community could exist as an exoplanet or as an asteroid, and the range of its perceptions would be incalculably great: conceivably, it could teleport hypermassive celestial bodies — or even entire systems — interdimensionally, and even that might to it be considered a mundane exercise.