The ArcBuilder Universe


TimeLine of the ArcBuilder Universe


The Post Angelic Era

5.42 to 3.2 billion years ago


5.00 billion years ago:  A vast emission nebula some 80 light years across, formed from the birth and death of previous generation stars, is located within the Milky Way Galaxy.  It is no different from thousands of other such complexes within the Galaxy, some of which are of greater or lesser extent than this cloud.  Like those many other nebulae, this one is influences by the passage of stars, by their deaths, and by the gravitational influence of the Milky Way itself.  Over a long period of time the nebula is twisted and pulled, and great knots of matter begin to condense and collapse upon themselves.  Many of these fragments are loosely gravitationally bound to each other.

This was the Prometheus Nebula, long since lost to the passage of time.  In no way was it remarkable unto itself.  Indeed, it might have been easily lost within the folds of other, greater molecular clouds, had it been near any.  Yet there was a single defining aspect to it that set it apart.  From here would form the Sun and her siblings.  From here would come the materials which would give rise to the Earth and all life upon it.

Singular knots of collapsing clouds would move through the nebula like eggs.  Some of these would come to be grouped together, prenatal families within dusty wombs.  As the Galaxy turned, so would more be born, and Prometheus itself would lessen.
4.568 billion years ago:  Amidst numerous supernova in the Prometheus Nebula, as the deaths of massive O-type stars light up the entire Galaxy, the shockwaves from the titanic explosions cause even more knots of dust and gas to contract in upon themselves, forming pre-solar nebulae.  In one dusty corner of Prometheus, a section of cloud some 20 light years in diameter begets thousands of these embryonic stars.  This is the Janus Cluster.  One such presolar nebula within the Cluster has, like most of its siblings, a diameter somewhere over three light years.  This is the future Sun.  This is where all that Humanity is will originate.  It is from here that all that we are, or will become, springs.

During this very early period, the earliest solid materials in the system form.  Small asteroidal bodies coalesce from the gas and dust, many of which survive to the present.  Etched deep into the chemical make up of their bodies are the signatures of nearby supernova occurring elsewhere in Prometheus, of close encounters with other young suns, and impacts with bodies born around other stars.  It was a chaotic time, and the Janus Cluster was constantly disturbed by the gravity of its inherent components.
4.566 billion years ago:  The Pre Solar Nebula, continuing to collapse under its own gravitational weight, begins to spin faster and flatten out, even as it contracts in size under the influence of angular momentum.  A protoplanetary disk forms, some 200 AU in size.  At its center is the still-to-be-born Sun, a hot and dense protostar, glowing angrily under the heat of its own formation.

It was at this point that the Sun became a T-Tauri star, a star powered by gravitational collapse alone.  With a central temperature still too low for hydrogen fusion, it and its siblings could still be considered prenatal.  Mottled with vast star spots, bursting with immensely powerful explosions of x-rays, this was a violent time.  Worlds had already begun to form around the Sun, small and wracked by the tantrums of stellar formation, cratered with collisions from the countless other worlds struggling to form in their own right.

It did not take long, however, for this phase of the Sun to move on to a new one.  With temperatures ever growing, it would finally burst on to the Main Sequence and erupt with its blinding light.  The birth of Sol was marked by a vast stellar wind, sweeping out the Inner Solar System and revealing a family of worlds that numbered in the thousands.  All around it, the other members of the Janus Cluster were likewise igniting.  The Prometheus Nebula, much depleted by many such acts of stellar life, became brightly illuminated by these tempestuous young siblings.

It would not take long for the cluster to be scattered, however.  Already the member stars were much more widely spread.  And in the tens of millions of years to come, they would eventually spread out into the arm of the Galaxy itself, to be swept along like grains of pollen in a mighty torrent.

4.550 billion years ago

  • The young Earth has formed to nearly its current mass.  Long since accreting while the Sun still labored to be born, at this early point in its own life the planet already possesses regions of liquid water.  Hydrogen and helium wrap the planet in a thick atmosphere, the leavings of the presolar nebula itself.  But much of this atmosphere is being lost to the intense solar wind.  Billions of tons of the gases escape the feeble gravitational grasp of the young Earth.  At the same time, as the interior of the planet writhes with an unquenchable heat, outgassing from the crust will actively replace what was lost with carbon dioxide, nitrogen, ammonia, methane, and water vapor.


  • The rest of the Solar System continues to form.  The Inner System in particular was swarming with young worlds, many of which were the size of modern day Mars, or even larger.  The fate of most of these planets was eventual gravitational disruption and ejection from the Solar System.  Near impacts with other worlds, or the Sun itself, would send them careening into the interstellar void.  Others were swallowed by the Sun, a hungry parent that cared little for the fate of her worlds.  And still others would meet a more spectacular fate, colliding with one another in vast conflagrations that would leave behind countless fragments for the rest of the System's history.


  • The Pre-Noachian geological era of Mars began at this time.  While much of the geological record for this period has long since been lost, some of the more massive indications of the heavy bombardment remain.  Most notably is the great circular Hellas Sea, originally formed from a massive impact with one of the thousands of other young worlds.
4.533 billion years ago:  As the Earth and her siblings formed, hundreds of other planet-sized bodies formed along with them.  Most were ejected from the nascent Solar System, many more impacted the Sun itself.  But some eventually impacted the growing primary worlds of the Inner Solar System, often multiple times.  Records of these events can be inferred from craters, planetary rotational rates, even chemical signatures within the crusts of some of the planets.  Earth herself did not escape this violence; indeed, much of the planet's mass is believed to have come from such events.

However, there was a world that formed in tandem with the Earth.  Located at one of the LaGrangian points, where the gravitational forces of the Earth and Sun balanced out and created a stable zone, the world of Theia took shape.  Perhaps wrapped within primordial clouds as was the Earth, perhaps even possessing young bodies of water on her surface, she would have been an inviting place to visit, given a few billion more years.  Unfortunately, she and the Earth (as well as the rest of the planets) were still growing, absorbing mass from the planetary nebula.  With greater mass came greater unbalance, until Theia began to drift in a slow orbit from her long established spot.

Eventually the two planets were gravitational, and fatally, attracted to one another.  Theia impacted the Earth at a relatively low velocity, and at a 45 degree angle.  Her iron core was fully absorbed by the Earth, so suddenly stripped of its primordial atmosphere and with a surface turned into a vast molten sea.  Most of Theia's mantle was also absorbed.  However, a significant portion of her mantel, as well as the Earth's, were ejected into orbit about the two now coalesced planets, a burning ring of debris.  Within as little as a month, and certainly no longer than a century, most of this material swiftly coalesced into the young Luna.  A secondary moon some 1,000 kilometers in diameter formed at the new Earth-Moon LaGrangian point, and for thousands of years remained stable.  However, the loss of angular momentum eventually destabilized and shifted these points as the moons migrated away from the central planet.  The second moon inevitably, slowly, impacted the far side of Luna.  This resulted in the thickened far side crust.

The initial impact of Theia had grave consequences.  The rotational period of the Earth was spun up to some 5 hours in length, although as the young moons moved away the tidal energy lengthened this, resulting in a longer day.  The Moon still does so to the Earth to this day, although at a vastly smaller rate.  A long range benefit of the impact was the stabilization of the Earth's axial tilt, necessary for a long term stable climate that would be suitable for biological evolution.
4.45 billion years ago:  The Earth has cooled from its formation, and its impact with Theia, enough so that bodies of water once again begin to form on the surface.  The planet's secondary atmosphere has been forming since the Theian impact, and the land is now covered with an opaque sky filled with methane, ammonia, and water vapor clouds.  Continued impacts, many of which are titanic, deliver complex organic molecules and water to the surface, while eroding the thick atmosphere at the same time.

On Venus, a major impact occurs with another Mars-sized world.  Many tens of these objects still remain in the Inner Solar System, but their numbers are swiftly dwindling.  This particular object strikes Venus  a glancing blow, and like the Earth, the result is the formation of a relatively large moon.  However, a secondary moon does not form, and the Venusian-moon system begins to stabilize much more quickly than Earth's did.
4.04 billion years ago: It is an ocean-forming period in the Inner Solar System.  Venus, Earth, and Mars all begin to develop major seas and oceans, their atmospheres losing large amounts of methane and ammonia in the process.  Carbon dioxide and water vapor become the major components of their atmospheres, causing the worlds to warm considerably, despite the young Sun having a luminosity only around 70% of its modern value.
4.3 billion years ago:  One of the last planet-sized objects in the Inner Solar System impacts Venus.  This collision, occurring from a forward direction relative to the orbit of the planet, reverses Venus' rotation, which in turn begins to rob orbital energy from the existing moon.  The eventual result is the impact of the moon with the planet, which reduces Venus' rotational period to a near halt.  The existing oceans are once more obliterated, the planetary surface reduced to a vast sea of magma.  Outgassing produces a thick atmosphere of carbon dioxide, which will continue to build until the surface becomes a hellish, high pressure environment.  With the death of Venus' nascent biosphere, the Inner System now possesses only two habitable worlds, the Earth and Mars.
4.25 billion years ago:  The family of the Sun, the ancient Janus Cluster, had been breaking up ever since its formation.  Repeated close encounters with fellow cluster members, as well as near encounters with stars that formed elsewhere in the now nearly depleted Prometheus Nebula, and over all gravitational effects of the Milky Way itself made this inevitable.  By this point, most members of the Cluster were bright but unremarkable in the Earth's night sky.  While some members of the Janus Cluster would maintain courses through the Galaxy generally similar to that of the Sun, by and large the family would be scattered throughout tens of thousands of light years.

It was also during this period that the earliest indications for life on Earth are known.  Modern geological records for this era indicate unusually high amounts of carbon isotopes, a sign of biological activity.  The inference is that the very simplest of microbial unicellular forms had already managed to establish themselves in marine environments, spurred on by the constant churning of the oceans, powered by the then massive Lunar tides.

4.1 billion years ago

  • The beginning of the Late Heavy Bombardment of the Inner Solar System.  By this point in time, the constant impacts from the formative period of the Solar System had become less than a drizzle, and the plethora of rogue inner worlds had been depleted.  The Solar System was, at last, settling down.  However, in the Outer System, there were five Jovian worlds, all with relatively close orbits to one another.  Having formed in multi-resonant configurations, the planets seemed stable.  However, repeated encounters with the trans-Neptunian  belt of icy objects eventually lead to the elongation of one of the ice giant planet's orbit, until it began to have close encounters with Jupiter and Saturn.  These encounters lead to a widening of the orbits between the two largest members of the Solar System, the consequences of which was the redistribution of gravitational resonances throughout the Outer System, and the Asteroid Belt.
  • Asteroids by tens of thousands are shifted into eccentric orbits, many of which propelled them to the Inner System.  The Inner worlds were struck by a high proportion of these objects, and the young Earth and Mars both suffered serious environmental damage at least once a century.  However, while the surface of the planets might be sterilized by the larger of these impacts (an estimated 40 or so of which would have created impact basins larger than 1,000 kilometers in diameter, and several more exceeding 5,000 kilometers), subsurface hydrothermal sites would have remained largely unaffected, and provided safe havens for microbial life on both the Earth and Mars.
  • The Pre-Noachian geological era on Mars comes to an end, giving way to the Noachian.  Much of the modern surface of Mars was formed during this period, marked as it was by the massive, continuing impacts from space.  Tremendous amounts of volcanic activity continued as well, aiding to maintain the world as both wet and relatively warm.  The great Tharsis Bulge began to form during this era, and would become a key geological feature for the rest of Mars' history.
3.9 billion years ago:  Biological cellular life, closely resembling prokaryotes, appear on the Earth.  Chemoautotrophs in nature, they use carbon dioxide as an energy source and oxidize inorganic materials.  This early form of biological activity allows them to survive in the hellish conditions imposed by the massive impacts that were relatively common during this time.  Indeed, it is the pressure imposed by these impacts which help to spur on an evolutionary adaptive response for survival.
3.85 billion years ago:  In the Outer System, the rogue ice giant is eventually ejected from the Solar System entirely,  and the outer planets finally settle into their modern orbits.  At this point, the disruptive gravitational resonances have ceased, and the Late Heavy Bombardment comes to an end.  The surfaces of Mars and the Earth begin to settle once more, and the transient oceans that had been repeatedly boiled off partially or completely, become permanent.  The earliest life on these worlds, largely confined to subsurface hydrothermal regions, begin to spread outward into these oceans, swiftly adapting to the much cooler environments. 
3.7 billion years ago:  The Hesperian geological period of Mars begins.  Increased volcanism on the planet followed the continuation of the formation of the Tharsis Bulge, allowing for the proliferation of native Martian microbial life.  Shallow lakes and seas were filled with mats of blue-green algae analogues, and the skies were beginning to feel the first touches of free oxygen. 
3.5 billion years ago:  It is at this point that the last universal common ancestor of all life on earth lives.  These unicellular creatures are the last in a line that will lead to a split between the bacteria and archaea.  Some forms of bacteria will develop the earliest and most primitive methods of photosynthesis, which at this point does not produce free oxygen.  Nonetheless, this is a momentous step in the history of life, and the advancement of forms that will lead to all modern biological organisms. 

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The ArcBuilder Universe is a science fiction project established, authored, and copyrighted ©
by John M. Dollan 2002-2016
This page first uploaded in January 24, 2016
Most recent update for this page February 10, 2016