People often talk about colonizing the galaxy, but today we are going to ask justhow far away humanity can stretch its reach
We have discussed many times how you might travel to another solar system and colonizeit, if you were constrained by the speed of light.
Indeed we tend to assume moving at only a fraction of that speed.
To do that, especially with classic humans rather than some robotic probe or seed ship,requires massive vessels that are almost miniature planets themselves, able to contain everythingyou need to start up an ecosystem at your destination and keep thousands of people aliveeither during the flight or in some sort of stasis to be awoken on arrival.
We saw that was possible, maybe even with modern science and technology, that you couldsend out ships for century-long journeys.
What’s interesting is that in most fiction, where they often have Faster Than Light orFTL travel methods able to move someone across a whole galaxy in maybe moments or maybe afew years, almost none of those sprawling galactic empires ever seems to settle othergalaxies.
That does makes sense when you have a galaxy already full of other intelligent life forms,since you can assume other galaxies will have their own too and not welcome colonists fromoutside, and it is a long trip just to say hello.
However we see it even in fiction where humanity has the whole galaxy to itself and no specialreason to think neighboring galaxies will have existing civilizations.
When that’s the case, it makes a lot less sense.
If you’ve got a spaceship able to cross the whole galaxy in a year, crossing to anothergalaxy should not be a problem.
Distances between galaxies don’t scale up like distances between planets or stars.
Stars are typically hundreds of thousands of times further away from our Sun than otherplanets are from Earth, and the distance to the Moon, still the only world a human hasset foot on, is about a hundred millionth the distance to the nearest star.
Alternatively galaxies are a lot closer together, relatively speaking.
The Magellanic Cloud Dwarf Galaxies are closer to some stars in our galaxy than they areto stars on the other side of the galaxy from them, and even Andromeda, the nearest largegalaxy to ours, is only about 20 times further away than the galaxy is wide.
So there’s no reason why, if you thought the neighboring galaxy was empty of civilizations,you couldn’t make that trip if you’ve got spaceships that can cross the galaxy ina year, because they can get to Andromeda in 20.
That would barely count as a generational ark ship, something we can almost do now,and should be child’s play for most galactic civilizations we know from fiction.
The other big thing to keep in mind is that the space between us and other galaxies isnot empty.
If we view galaxies as continents, with intergalactic space as the ocean, there are plenty of littleislands to use as waypoints.
There are a lot of stars in between, and galaxies don’t have firmly defined edges either.
Also, stars are often ejected from the galaxy, much like how planets can get ejected froma solar system.
We aren’t sure how many of these stars there are yet, I’ve seen estimates as high ashalf of stars being intergalactic, but there’s decent confidence of it being 10% of stellarmass or higher.
Equal or lesser populations than galaxies, it’s still spread over a much larger volume,so these stars are much farther apart, light centuries not light years, but they make potentialwaypoints on a trip.
Decent ones too, because while most stars on the outskirts of a galaxy have low metallicity- and so probably not a lot of rocky material nearby - often these ejected ones were tossedout by passing near the central black hole of our galaxy and are higher in metallicity.
Add to that, while an ejection of a planet from a system or a star from a galaxy oftenstrips it of its satellites, it also often does not, and the closer the satellite isto its parent, the less likely it will be ejected.
So the rockier inner planets of a system are more likely to be retained.
That means these waypoints could have plenty of raw materials to use to refuel and repair,and potentially have planets to settle on.
You don’t necessarily have to go sundiving to capture fuel and raw materials on someIcarus-like plunge into the star to pick up material, like we saw from the spaceship Destinyin Stargate: Universe, one of the few scifi franchises to seriously tackle intergalactictravel and timelines.
You can do stuff like that too, as we’ve discussed in the Starlifting episode and willlook at more next week in Colonizing the Sun.
Today we don’t care about that though for three reasons.
First, as mentioned we have discussed before how it can be done if you need to, second,odds are many of the stars will host planets which you can mine more conventionally.
But third, you normally don’t stop on interstellar voyages to refuel.
Oh, in fiction you often do, they tend to have FTL systems that are non-inertial, awarp drive that requires constant power input to maintain its speed rather than just coastingalong, or wormholes or gates or hyperspace jumps with maximum ranges that leave you stoppedrelative to the local area, rather than needing to burn a ton of fuel to slow down and thenmore to speed back up when you’re done.
Normally in interstellar space you head to your destination without stopping, becausedoing so costs you time and gains you nothing.
And while I always say it would be nice to have FTL, it doesn’t really look like itis in the cards, nor do we really know the logistics involved if it was, since they aredifferent for every hypothetical drive system.
So we always try to look at the future assuming no new physics and see if we can tackle aproblem anyway.
Normally you wouldn’t want to stop a ship en route to another galaxy, or so we’d assume,since it will tend to involve a not-quite straight path between various intergalacticstars and that wouldn’t seem to make sense, but we’ll be giving that a second look today.
We also do have an existing precedent for stopping an interstellar spaceship.
In the Life in a Space Colony series, we examined a ship called Unity, a large interstellarvessel kilometers long carrying hundreds of thousands of passengers.
After they arrived at their destination they realized that they did not really need tostop and stay there.
They had all the manufacturing ability needed to take raw materials and build anything inthe ship’s structure or colonizing inventory.
This was up to and including the colonists themselves, since they were making journeysof many decades and could easily replenish their colonist pool simply by keeping a decentportion of them on the ship to breed more colonists for the next stop.
We gave them both life extension and the ability to freeze people and thaw them out.
Although both technologies were handy for growing the colonists’ numbers, they weren’ttruly necessary since people weren’t dying off and could continue to have children andmaintain a crew with the same goals and traditions.
So this ship, Unity, decided it could transform itself from a regular interstellar arkshipwith one destination in mind into what we called a Gardener Ship, one that stops ata system, builds a colony, picks up new raw materials and fuels, and heads off to a newdestination.
During the flight, they would breed up their numbers again, and work on turning all thoseraw materials into colonial gear or replacement parts and supplies for the ship.
We ended up revisiting the crew in the episode Interstellar Travel Challenges to upgradehow fast they could go and talk about all the problems one can encounter moving throughspace that fast.
We also visited them again in the Dead Aliens episode but I consider that non-canon to theirtale, which we’ll pick up again today because it’s handy to have a narrative framing device.
So our gardener ship Unity has been slowly working its way out to the galactic rim, ashave various sister ships, and indeed every so often the ship divides itself up like anamoeba.
They can make every part the ship needs so they can make a new twin ship and do upgradesas new science comes in from home.
However, we will still limit them to the 20% of light speed we gave them in our last visit.
We will also ignore that the ship, which first went to the Tau Ceti than Epsilon Eridani,was headed in the wrong direction for Andromeda, so they’ve kind of cork-screwed around.
Handily Andromeda is in the direction of the region of the galactic edge closest to us,so we don’t have to cross the whole galaxy to get there.
It’s not quite the fastest route the galactic edge, which would lie more in the directionof Orion, and we need to head more toward Perseus to aim for Andromeda, but it is fairlyclose and a lot better than crossing the whole galactic disc.
That’s also true of both Magellanic Clouds, we’re closer to them than most of the galaxyis.
That’s worth mentioning because ‘intergalactic’ is a bit relative.
Andromeda is the nearest big galaxy to us, but the Magellanic clouds aren’t much furtherfrom us than the furthest parts of this galaxy, and they are no longer the closest known dwarfgalaxies.
The Sagittarius Dwarf Spheroidal Galaxy is considerably closer, just 70,000 light yearsfrom Earth, and the Canis Major Dwarf Galaxy, whose status as a galaxy is still debated,is only 25,000 light years away.
In all 4 cases, colonizing them is not really any harder than colonizing the more distantparts of our own galaxy, and there are plenty of stars in between to use as way points.
I will be ignoring them today though beyond pointing out that they would tend to be settledalong with the rest of the galaxy, though in many cases you will need to cross someareas fairly devoid of stars and pick your path accordingly.
But it also means our ship Unity has arrived at the galactic rim a long time later, onthe path they took it would be at least 30,000 light years and they’ve only been going20% of light speed, not to mention stopping for at least a few years once or twice a centuryto set up a colony.
So we last saw them sometime around the 26th century AD, centuries ahead of us in the twenty-firstcentury, but it is now closer to the twenty-first hundredth century.
They are fifty times further ahead in history than the pyramid builders are back in history.
They are parked at a last lonely star near the galactic rim, the Terminus System, andthe captain is deciding if they dare jump farther off and head for Andromeda or abandonthe mission, finally stay at a planet unlike the many hundreds she’s colonized and leftbehind.
Truth be told, she’s been planning this for millennia, captain of one of humanity’sfirst interstellar colony ships, even if it’s been rebuilt and subdivided dozens of times.
They could turn around, they could get back to Earth a good deal faster with the laserhighways between stars many worlds have been creating as they got bigger.
They could settle here or turn perpendicular and help colonize the galactic rim.
Indeed they could do all of the above.
Spending decades to build new ships, one to head off on each direction of the rim, oneto head off to Earth for those wanting to see home again, and one to head off to Andromeda.
The science officer points this out and that they probably want a much bigger ship or fleetof ships to do the job.
He also points out that individuals don’t actually have to choose, it’s the year 200,000AD, none from the original crew are entirely human anymore, and copying their minds ontosome clone bodies or androids isn’t too hard.
They’ve done that before, for a crew member or colonist who wanted to travel on but alsowanted to settle down, folks who had a spouse or kids who wanted to stay and they couldn’tdecide if they wanted to stay or go, so they did both, making a copy of themselves.
Or when the ship subdivided, building a twin to head off at a different angle to colonizeother systems.
They have some crew members who have done that many times, same as they have otherswho sleep most of the journey.
This is the original ship, for a given value of original, that headed out from Earth 200,000years ago, and the original captain, for a given value of original, who piloted it out,and the original science officer, for a given value of original, who has been nitpickingher plans since Unity was on the drawing board.
But the ship can’t make the journey on its own, so the science officer says.
This ship is immense, bigger than when it left Earth and you could have crammed a majormetropolis into that one.
But to do this right, they are going to want a whole fleet and they need to build thathere at Terminus.
Now we say Terminus is the last star at this edge of the galaxy but that’s not entirelytrue.
It’s actually an extragalactic system sent on its way many millions of years ago andjust now getting out of the galaxy.
In fact with a little bit of nudging, it could be aimed to reach Andromeda.
They could colonize it and just wait.
Andromeda is, after all, set to merge with the Milky Way galaxy in a few billion yearsand they could get this whole system to arrive there a good deal sooner than that.
There is a highly advanced technology called a Shkadov Thruster, whose design is actuallya very simplistic one.
It calls for trillions of cheap mirrors to be placed around a star so that they bounceall its light in one direction, providing thrust and allowing you turn a whole solarsystem into an interstellar spaceship.
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