By A. S. Deller | 10 June 2021
Medium
Using the newest data from the European Space Agency’s GAIA spacecraft, the ESA created a map of our galaxy that pinpoints the brightness and positions of nearly 1.7 billion stars.
Our Milky Way is roughly 100,000 light years across. To cross our galaxy end-to-end would take 100K years moving at light speed. Ridiculous. That’s just to cross it in a straight line. Covering the actual volume of space enclosed by the Milky Way in our fictional “U.S.S. Enterprise” would require hundreds of millions of years.
And yet, despite our galaxy’s immense scale, the future of life on Earth ultimately depends on the human race taking to the stars and settling other worlds.
If we don’t undertake this fateful mission, it is only a matter of time before man made or cosmic threats kill most or all of humanity and all other living things on Earth. Whether nuclear war or biological plague, major asteroid impact, supernova explosion or gamma ray burst, some disaster WILL befall our planet sometime between now and a few thousand years in the future.
Humanity needs to prepare for this inevitability now, before something terrible occurs that reduces our capacity to do so, like a high energy solar flare or series of supervolcano eruptions.
One Small Step
We began, with that first “small step”, on July 20th, 1969, when the Apollo 11 lunar module fell into our Moon’s gravity well. Buzz Aldrin and Neil Armstrong became the first human beings to land on another celestial body. Today, several plans are underways to take the next steps in our journey outward into the cosmos. These primarily involve setting up bases, and eventually cities, on Mars.
Settling Mars will be the test case that allows us to prove we can live on a world significantly different than Earth. The two organizations that are likely to be the first to send humans to Mars are NASA and the private corporation SpaceX. SpaceX, led by entrepreneur Elon Musk, plans to place the first humans on Mars by 2030, with the hope that a permanent settlement will be thriving by 2100.
Looking to the stars for humanity’s ultimate salvation has many detractors, people who believe we should focus solely on solving the problems we face on Earth before we consider the enormity of outer space. While these problems are indeed terrible and need the attention of great minds and philanthropists (such as Bill and Melinda Gates’ work), we cannot entirely ignore the long-term promise of expanding the presence of humanity across multiple locations in the galaxy.
For those who believe we should be stewards of the rest of Earth’s life, since we have presided over so much of its devastation, settling the galaxy offers a chance to also save ALL other life on Earth. Humans will not go alone into the depths of space. We will take with us many, if not most, of our companions on Earth, in the form of DNA samples, embryos and seeds. Some day, perhaps 100,000 years from now, there may be a dozen other very Earth-like planets safely distributed throughout the Milky Way, locations chosen specifically to ensure that any single cosmic catastrophe could never devastate them all at once.
In order to reach such a point, we will need to drastically advance our space technology. This will take money and time. As we proceed, every step of the way must result in the creation of a new economy in the place of settlement, since trading actual material goods back and forth between planets will be incredibly costly in every way.
How Do We Go Further?
After our first settlements on Mars become somewhat self-sufficient, the process of terraforming can begin: releasing water and carbon dioxide from the planet to thicken its atmosphere and raise its temperature while providing sustenance for plant life that has been genetically modified to thrive in hostile conditions. Over centuries, Mars will become a green, wet world with an oxygen-rich air that perhaps some of our great⁴ grandchildren might breathe.
As new bases are established, ever further from the Solar System, only information will be relatively cheap to transfer. New inventions and thought that results from our explorations and adaptations will benefit everyone, but every successive settlement will need to be able to survive on its own.
One way we can help ourselves in this course is to build and program a fleet of smart robots to pave a path for us into the stars. These would be similar to the the idea of Von Neumann machines, named after 20th century Hungarian physicist Jon von Neumann. Such machines would be robust AI-driven creations whose programming sends them to worlds which have the highest possible compatibility with Earth life. For now, we refer to such worlds as being located in a star’s habitable, or “Goldilocks”, zone: Orbiting at just the right distance from its sun to allow the existence of liquid water. Not only is water a necessity for life, but the planet needs to contain the right mixture of elements that will allow animals and plants to thrive. It will also need a strong magnetic field – presumably due to a molten core of iron – to foster a proliferation of low molecular weight gases like hydrogen, nitrogen and oxygen. This same magnetic field also acts to deflect a large proportion of deadly solar radiation.
After arrival on such a world, the Von Neumann machine would begin mining the planet for raw materials and then use the most advanced 3D printing technology to turn those materials into fuels and more machines. These resources, in turn, would go about building bases for humans and starting the long process of terraforming the planet.
Later, perhaps a century or a millennium after the Von Neumann machine had begun its work, a starship containing humans held in cryonic suspension, or perhaps just human embryos, would arrive to populate the new world.
How long might a process like this take?
Based on data from NASA’s Kepler spacecraft, there may be as many as 40 billion Earth-sized planets orbiting inside their star’s habitable zone in our galaxy.
Far-Off Planets Like the Earth Dot the Galaxy https://t.co/lop55osDbF
— Church and State (@ChurchAndStateN) June 15, 2021
If exponential growth could be applied to settling the galaxy, complete settlement of every habitable exoplanet may happen within the next 500,000 to 10 million years. However, according to Seth Baum, current Director of the Global Catastrophic Risk Institute:
“The problem is that this kind of growth may not be possible, and they look at Earth as an example. For any expansion to be sustainable, the growth in resource consumption cannot exceed the growth in resource production. And since Earth’s resources are finite, and it has a finite mass and receives solar radiation at a constant rate, human civilization cannot sustain an indefinite, exponential growth.”
The better question may be: How long will it take for humanity to place a stable population on enough planets to ensure the existence of Earth-originated life for a million years?
Preserving Humanity and Earth Life for Eternity
Outside of Mars, the best bets for a sustainable settlements in our own solar system are long shots at best: several moons of Jupiter (Callisto, Ganymede, Europa) and Saturn’s moon Titan. However, those locations are not especially amenable to terraforming due to their great distance from the Sun, which is what is needed to truly preserve human and other Earth life.
The nearest rocky exoplanet that orbits within the habitable zone of its star is Proxima Centauri B, at 4.2 light years away. This world would be our first candidate for settlement and terraforming outside of our Solar System. If we can reach speeds of even 1/10th C (the speed of light, 186,000 miles/second, as in E = MC²), getting any spacecraft to Proxima Centauri B would take 42 years.
The Breakthrough Starshot project is an initiative to propel a small fleet of one-gram nanospacecraft the size of a postage stamp – what they’re calling a “starchip that is really just a super-miniature computer – to 1/5th C (100 million mph) on a journey to Proxima Centauri B and other planets in the Alpha Centauri system. This acceleration will be accomplished via directed light beams at solar sails, allowing the speeds to be reached without any onboard engine of any kind.
We are very limited with how we get into space and continue accelerating currently. Propellent technology only gets us so far. At our present pace, it would take ~30,000 years to reach Proxima Centauri B. The trifecta of fusion, fission and antimatter propulsion are the focus at this point, all believed to be capable of getting us to the 10% C mark. As speeds increase, so do the inherent dangers of space travel, such as radiation and micrometeoroids, which makes 10% of light speed both a safety limit as well as a practical limit on how fast we might be able to travel in the near future.
There are just under 50 exoplanet candidates known right now that could be sites for settlements, and also be in the habitable zone and therefore allow for eventual terraforming. The distances from Earth range the gamut between Proxima Centauri B’s 4.2 light years to Kepler 443b’s 2540 light years. These are only worlds that we’ve discovered up until now: There is no doubt we will discover more potentially habitable exoplanets on the nearer side of that range within the next few decades.
If we want to make certain humanity cannot be completely wiped out in any one cosmic disaster, we need to eventually have settled worlds that are at a sufficient distance from one another to avoid such possibility. To this end, we look at the largest scale cosmic event we know of: a supernova explosion. According to this article, a minimum safe distance from a supernova is 30 light years, though the size and effects of such an event can vary so much that in order to be certain we should include a buffer of 150%…so let’s say 45 light years.
Aside from a catastrophe on a galactic scale that we could never defend against, this means that we need to reach a point where humanity has settled at least 45 light years from Earth. The closest candidate world that fits this case is Gliese 163c, at 49 light years away. A journey of 49 light years, at an average speed of 10% C, would take approximately 490 years.
Out of our list of ~50 known potentially habitable exoplanets, about 20 of them are within that 45 light year range of Earth. A few are contained in the same star system, most notably 4 worlds in the Trappist-1 system 39 light years away.
Without a doubt, our first goal must be to create a second home for humanity and Earth life on Mars. The world’s close proximity, gravity and water offer our best bet for a sustainable settlement and eventual terraforming. Establishing a stable settlement on Mars may take until 2100, while a truly thriving population that is no longer dependent on Earth might take another century to develop.
And what if we find alien life along the way?
The discovery of native alien life forms on any world that we explore will offer a wealth of unique opportunities, as well as perils.
Alien life may be compatible in some ways with our own, on some planets. For example, perhaps DNA is a requirement for life and all living things in the universe use it as the basis for their genetic code. If this is the case, then we may be able to find a way to live alongside such life, integrating our own biological needs with that of an alien biome. However, this is questionable at best because even on Earth there are things that make us question if DNA could ever be a limiting factor for “life”, such as viruses which don’t contain DNA at all and instead hijack other living cells to use theirs. Being compatible could also mean we would be vulnerable to alien disease and pathogens and vice versa, which would be very bad for both sides.
And then there is possibly the more likely scenario in which alien life is very different from Earth biology. Perhaps it is silicon based, or is a million-year-old civilization that has completely transferred its consciousnesses over into machine or energy forms. If the alien life we encounter is either vastly more primitive than us or vastly more advanced, we might be entering a situation much like that seen when explorers from Europe arrived in the Americas in the 1500s: a terrible cycle of intentional and unintentional mass deaths. If humanity ends up being the “primitives” in these scenarios, it would be us in danger of becoming extinct.
For both our sakes and the sake of other intelligent life in the cosmos, it may be most prudent for us to try our best to avoid direct contact with any sentient galactic neighbors for a long time, until our technology develops to a point where we can be very sure of our military and medical security.
And onward into the future…
During the middle centuries of this millenium, humanity will be focused on building smaller human stations on moons of Jupiter and Saturn, as well as perhaps on the massive Ceres asteroid in the Asteroid Belt. This time will be one of advancement in our ability to survive for long periods in space without many negative side effects, learning how to terraform Mars, and also developing true starships and medical technology that will empower us to make the jump to Alpha Centauri.
By 3000 AD, humanity should be established on Proxima Centauri B, and dozens, if not hundreds, of other ships should be on their way to the other 50-odd potential settlement worlds, all much farther away, containing either humans and other Earth life in suspended animation or in the form of embryos and seeds.
By 12000 AD, humanity could be firmly rooted on a dozen worlds, some of them separated by enough distance from Earth to ensure that a single supernova could never drive Earth life into complete extinction.
At this point, the children of Earth, all life born here, will have a true chance at immortality: The rest of the Milky Way galaxy awaits.
Reprinted with permission from the author.
A. S. Deller is a Sci fi, Fantasy and Science writer. Follow him at Medium and Twitter.
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