If you are not yet familiar with this series, please review Parts 1, 2, 3, 4, 5, and 6 before proceeding. Without familiarity with the preceding parts, what follows will likely be unintelligible. This is the concluding segment of the series, where I expand the time horizon to the titular frame of 1 million years (1 My), having applied energy-economic thinking to imagine a broad framework for the distant future.
It has been about seven months since the last entry in the series, which I had suspended due to apparent lack of interest - Part 6 attracted only four commenters - but I've received a specific request to finish the series, and have therefore decided to write the final segment.
(Current part in Bold)
I. The Energy History of Life (Part 1)
II. The Energy History of Humanity (Part 1)
III. The Next Decade (Part 2)
IV. The Next Century (Part 3)
V. The Next Millennium (Part 4)
VI. 10,000 Years (Part 5)
VII. 100,000 Years (Part 6)
VIII. Mark: One Million Years (Part 7)
At the conclusion of Part 6, the human "species" is no longer a singularly-defined organism so much as a multi-star technological ecosystem divided between star-centered Root systems and itinerant Spore civilizations. There is no longer any meaningful distinction between living organisms and technology, because they occur on a continuous spectrum in an unimaginable multitude of forms, sizes, and associations along the common energy pathways that guide evolution. When I refer to "humanity," I therefore refer to this abstract human-derived ecosystem rather than to biological entities who resemble homo sapiens - although creatures vaguely like us will still exist in various places at various times.
Over the 100 ky timeframe in Part 6, a process had begun in the solar system (and nearby stellar civilizations) whereby the resources of the Outer Root undergo an accelerating migration into the Inner Root - i.e., the raw materials and volatiles of the planetary/cometary halo are increasingly brought inward toward the Sun as a result of economic imbalances described earlier. The rocky Inner Planets and Main Belt asteroids are basically dissolved, adding to the density of the IR Disk and its expansion into something effectively like a Dyson sphere - although it need not necessarily be a singular structure: Simply a system that efficiently collects solar energy from every direction. Speculating on the engineering specifics of these structures would be a fool's errand, but the fact remains that the energy logic of surrounding a star is unavoidable.
As the gas giants, and eventually even nearby dust comes to be depleted, the Outer Root ceases to exist and its civilizations either merge with what we can now call the IR Sphere or become Spore and emigrate. This results in a new material scarcity whose consequences are predictable: To do more with the same amount of matter requires more energy, greater energy efficiency, or both, so the IR Sphere would migrate further inward toward the Sun, becoming both thinner, denser, and more computationally intensive. With the intricacy and energy of the processes taking place, the rate of evolution occurring within this Sphere in a single second would outweigh all of human history to date.
As it becomes more efficient and adept at manipulating its host star, the IR Sphere comes to increasingly follow its minute contours and flux patterns, like an oil slick on the ocean. It may be found useful to increase or decrease the stellar surface area, or conduct other changes that serve the inscrutable purposes of this civilization. What would essentially be happening is that the Sphere would be "merging" with its star, transforming the star into an ultra-complex, high-energy ecosystem as the computational "skin" migrates inward and induces internal structural changes by manipulating solar output.
This is a natural progression along the process that has been occurring throughout the history of evolution - the climb up the prime energy pathway, which in our case is the Sun. Once civilization becomes Sun-centered, the next step is clearly inward migration, and it seems likely that migration would not stop at the corona or photosphere - the ultimate source of the free energy is the stellar core where fusion is taking place. Likewise, the depletion of planetary matter means that solar material itself would have to suffice, so not only would the Sun be a source of energy, but also of matter.
"We" would in essence become the Sun, and in the process transform it to fit "our" needs. At this point it is necessary to use quotes when saying "we," "us," or "human," because this civilization has less in common with what we know than we have in common with an ant colony, but its shape and progress are still predictable because life follows the useable energy.
What we have then, as fantastic as it sounds, is a conscious star. The concept seems almost psychedelic - the merging of humanity and the Sun - but we find that technology over the long term often does begin to approach things only dreamt of in ancient spiritual musings. Buddhism, for instance, pioneered as a spiritual maxim what is today the foundational principle of science: Causality. For Buddha, it was an intuition rather than an observation - the seeing of all things as part of a river with both an upstream cause and a downstream effect. The principle is known as dependent origination in Buddhism, which contrasts sharply with the Judeo-Christian-Islamic universe where an all-powerful tyrant just makes things happen because he feels like it. For today's scientists and rational thinkers, causality is just common sense, and any supposition that violates it is false by definition.
Sunward migration will, I think, prove a similar phenomenon over the vastness of time, although with plenty of complications along the way (as described in previous Parts of this series). I should note that I got the initial idea of Sunward migration from David Brin's Second Uplift Trilogy - Brin is himself a Kossack, and posts occasionally - although the energistic/evolutionary basis for the concept is my own thinking. His interpretation was that this would be based on some instinctive attraction to deeper and deeper gravity wells, whereas I have gone with the simpler view that maximum useable energy at minimum cost dictates evolution.
This could lead to similar outcomes between my framework and Brin's literary universe - e.g., I see no reason why the same Root/Spore evolutions would not favor advanced settlement of and migration toward neutron stars and black hole disks. In fact, that is probably what would happen over timespans much longer than 1 My as settled stars leave the Main Sequence (or are artificially driven off of it). Still, I will voluntarily end my predictions at 1 My, because the settlement of stars is as far as known physics takes me - as flimsy as my basis for this series may be (and I actually think it pretty sound, all things considered), beyond that point is totally arbitrary speculation.
Now, getting back to the point, the Milky Way Galaxy is mostly settled at 1 My: Which means in practice that the volume of settled systems encompasses most of the galaxy, not that most star systems are occupied. This is similar to how the world is full of people right now, but it doesn't lack for empty land. The way the galaxy will be filled is, as stated in Part 6, through migration along the galactic spiral arms where stars are both numerically densest and most energetic.
Growth would occur in all directions, of course, but those proceeding along spiral arms would meet with the most success and the quickest turnaround of new colonization drives. However, in keeping with the "middle-case" thesis made in Part 1 of this series, it may also be probable that moderately-dense areas of the arms will leapfrog the richest by producing more advanced Spore iterations. Eventually the cascades going outward toward the galactic rim will achieve a steady-state, while that going inward toward the galactic center will find an ever-richer environment of increasingly dense, powerful stars. It would take longer than 1 My for the distinction to become stark, but this would be the basis for a new Root/Spore boundary: The galactic hub would be Root, and its arms Spore.
At the beginning of the current time horizon, we have three active Spore iterations: N+2, N+3, and N+4, respectively corresponding to in-system trader civilizations / one-way interstellar colonizers, cyclers among nearby systems, and large migratory seed civilizations that travel indefinitely and fission off lower-level Spore. Each iteration is very different in size and the time periods over which it operates - for instance, an N+4 may not even consider its role as a seed-colonizer significant, and may merely fulfill that role as a secondary consequence of other pursuits over hundreds or thousands of years.
As the planetary resources of stars are depleted and the Root civilizations migrate into the stellar body, there is no longer a large-scale economic basis for Spore civilization as I've defined it so far. There are not enough outer system resources to trade for directed energy, so the Root becomes increasingly efficient at making do with diffuse stellar matter for applications that require mass. Once the Root becomes "Starmind," I suppose it's possible it may develop ways to change neighboring stars into copies of itself through energetic manipulation at a distance, but this is just one possibility and not at all necessary to the model. What is likely is that Starminds will communicate and form information networks.
By this point, the "Sun" is a backwater node in the galaxy - its environment is not especially dense, and as a G2 Main Sequence star its output is modest, so there's nothing special about it. If any memory exists that galactic civilization originated there, let alone on a planet, it's probably just one among an infinite multitude of equally unprovable theories and myths - and the role of what we think of as humanity would not be known at all.
All of our history and the things we know today would be an insignificant solution to a general equation in some of the models used to understand the past - but we would not be known. Our whole world would probably not be known, having been dismantled for materials in the birth of the IR Disk - something that itself is just a distant memory to the Starmind that had been the Sun. But though the Starmind would have forgotten so much, it would have discovered much more than we can imagine.
Spore would no longer be present in regions populated by Starminds - the raw materials that support them would be scarce, so they would be increasingly pushed outward toward regions of the galaxy where Starminds are diffuse, slower to evolve, and have more material nearby. This is the initial formation of a galactic Root/Spore boundary mentioned earlier - the Root would consist of Starmind networks, and be progressively swept clean of planetary systems, while the extant Spore iterations would continue in their itinerant capacities in outer parts of the Milky Way in association with low-energy IR Disks and embryonic Dyson spheres.
With the formation of the galactic Root/Spore boundary, entire star systems and stellar clusters on the outer rim, the Northern/Southern faces of the galaxy, and the sparse inter-arm regions of the Milky Way begin to exhibit Spore behavior - we can call this the N+5 iteration. They may manipulate their galactic orbits to migrate over long periods between the energy-dense Starmind regions and the energy-poor areas that continue to have large quantities of raw material, and in this way form a scaled-up version of the N+2 Traders that had once functioned within solar systems. Also like N+2 (with respect to stars), they may set themselves on escape trajectories and head out of the galaxy entirely, although I think such expeditions would be very infrequent due to the time and resource constraints involved. Nevertheless, there are plenty of "nearby" satellite galaxies.
This is as far as 1 million years takes me. If we were to extend it to 10 or 20 My, I would say that stars in the Starmind network would migrate their orbits inward toward the galactic core in order to have more rapid communication and a richer energy environment, ultimately forming a Galactic Mind, and that large associations of stars would leave the galaxy as N+5 Spore (perhaps they would look like small elliptical galaxies...hmmmm...) But it doesn't take very long to say that, so I can just leave it as a concluding segue.
Now, I consider this series a highly cautious set of predictions - it requires no new physics, posits no deus ex machina from AI or ET, and doesn't even rule out any number of global apocalypses between then and now: All it posits is that we survive, and if that is granted then the most probable ways I am wrong are in setting these evolutions too far in the future. We will discover and utilize weird physics, so this is a future - the way things will pan out if our understanding fails to fundamentally advance. Try to wrap your head around that: This series is not a blue-sky idealistic science fiction fantasy, it is stingy - it is what nature impels us to become, even in the total absence of any special genius or serendipity. Never doubt that Life is more awesome than you can imagine.