The Milky Way is 13 billion years old, and some of our galaxy’s oldest stars were born near the beginning of the universe itself.
And if we really are about to send life to other possible worlds, shouldn’t the Milky Way be teeming with alien ships and colonies now?
Recent computer simulations by Jason T. Wright and others reveal that the best place to look for ancient alien civilizations may be in the galactic core, a relatively unexplored goal in the search for additional Earthly intelligence.
Ancient mathematical models of space colonization attempted to determine the time required for a civilization to spread throughout the Milky Way. Given the size of the Milky Way, large-scale galactic colonization may take longer than the age of the galaxy itself.
When a ship arrives in a hypothetical habitable world in the simulation, the world is considered a colony and can launch another craft every 100,000 years if there is another uninhabited world in range.
The spacecraft simulator has a range of 10 light years with a maximum travel time of 300,000 years.
Since the galaxy was formed from the inside out, the center is filled with ancient planets that provide more time for life to evolve.
And if you want to send a signal to the rest of the galaxy, you can do it from the center to cover the disk of the Milky Way. Likewise, if you wanted to find a signal, you might look at the center itself.
The researchers hypothesized that an advanced civilization might be able to harness the energy of the Milky Way’s central supermassive black hole to power a galactic-wide signal beacon.
They also noted that during colonization, an advanced civilization had developed new propulsion techniques that shortened the time needed to propagate. However, initial radio scans of the galactic nucleus did not reveal any signals.
Simulations show that it is possible that some parts of the galaxy will never settle, despite eons of time.
Over time, some colonies die and are lost, possibly due to resource depletion or a catastrophic event. Instead of going further from space, colonies choose to repopulate a dead colony from a closer distance.
Groups of inhabited colonies are formed surrounded by uninhabited planets that have never been colonized. A “stabilization state” is achieved where the habitable regions of the Milky Way’s worlds are too ineffective for colonization.
Perhaps long-lived civilizations are destined to grow more slowly than expected. If there were multiple colonial civilizations, they might compete for resources or move away from each other.
Civilizations may be careful not to interfere with inhabited planets like ours, or be wary of potential biological incompatibility with other worlds.
The simulations show that, given our location in the galaxy, there is an 89 percent chance that at least 1 million years will pass without visits from interstellar vehicles — enough time to erase signs of earlier colonization.
There are so-called globular clusters (GCs), which are huge, ancient groups of stars that orbit the galactic center at distances of up to tens of thousands of light years. The effects of a period of intense star formation that stimulated galactic mergers, are about 150 known global centers in the Milky Way, ranging in age from 10-13 billion years.
GCs are incredibly dense with stars much closer to each other on average than in the Milky Way’s disk.
However, the unique feature of this new simulation is its calculation of the motion of the stars of the galaxy.
The Milky Way is not static, as assumed in previous models, but rather a swirling mass. The new simulation reveals that stellar motion aids in colonization and contributes to a common effect in the spread of civilization.
The simulation builds on previous research by Jonathan Carroll-Nlenback and others, who suggested that a hypothetical civilization could spread at sublight speeds across a moving galaxy. The simulation assumes a civilization using ships traveling at speeds similar to our spacecraft (about 30 km/s).
However, a civilization within a GC would experience interstellar travel time in the order of only a few years with contact times of months or even weeks.
There is also the possibility that the planets that have been removed from the systems can still host a civilization due to the combined ambient energy the planet receives from all the stars in the mass – especially if the civilization has advanced solar capture technology.
The researchers suggest that even if only 10% of GC stars have habitable planets, 1% of them support intelligent life.