I often think about how stars come within 1 light year of our Sun every 300,000 years. It's pretty wild. And then I have to worry about rogue planets, meteorites, and obfuscated stars going supernova. What are the odds we're here?
At least I think that's what they meant. It's an interesting idea for sure.
There could be a good measure of good luck needed too. eg the spaceship is lucky enough to get some gravitational assistance from a large body or two in the target system
If the time between encounters is a million years, at 30 km/s the stars will have separated by 100 light years.
Given the likely time scales, do you reckon that'd be challenging?
To me, that sounds like an awful lot of acceleration would be needed.
https://www.wolframalpha.com/input?i=%2830+km%2Fs%29%2Fg&ass...
If you could teleport a fully fueled Saturn V into orbit, it could speed up by about 18 km/s. More if you reduced the payload.
Of course going from 18 to 30 exposes you to the tyranny of the rocket equation: to go faster you need more fuel, which makes your rocket heavier, which means it needs more fuel, which makes your rocket heavier, ... Any small efficiency increase matters a lot here. It might be possible with today's tech if you build the rocket in orbit (which gets rid of aerodynamic constrains), or alternatively with orbital refueling and a couple more decades of progress in more efficient engine types (which you could greatly accelerate by throwing money at it).
Solar sails released at perihelion can also achieve very high speeds.
Slowing down in the target system could be done with solar sails or electrodynamic sails (working on the stellar wind).
Ion or plasma engines are another possibility, with nuclear power plants.
We're talking about stellar visitors that arrive every 20 million years or so. We have no evidence of any civilization that lasted much more than 1,000 years.
So you're going to hitch a ride with a stellar visitor, with a view to colonizing the galaxy? Suppose the visitor comes as close as a few thousand AU, and the colonist ship can reach it in a hundred years or so; cool. But how long before the visitor reaches the next star on its tour? That's going to be millions of years.
So the colonists set up camp on a planet orbiting the visitor; the hypothesis is "a very long-lived" civilization, so we assume they have brought their knowledge with them to this camp, from the home planet, and are able to conserve it (strong assumption). But for tens of millions of years?
Civilizations evolve much more quickly than organisms, if Earth history is anything to go by. It seems far-fetched that a civilization might survive the evolution of the underlying organism; there's something Canute-like about trying to preserve a civilization in the teeth of genetic evolution. Evolution is going to happen, even during the initial journey to the visitor.
I'm very sceptical about this notion of "very long lived extraterrestrial civilizations".
There's been this great (relatively) short story, both humorous and profound, by Stanisław Lem; "The Twenty-first Voyage" in "The Star Diaries". It's based on that exact premise.
Yeah, but would anyone do that to an entire civilization? Evolution leads to greater 'fitness' - improved adaptation to the environment. The travellers are jumping from $HOME_PLANET, into a generation ship, onto a new planet presenting novel adaptation challenges. That planet's star-system then eventually sets off on a long journey, until it encounters a new star. Each of these stages takes many times the time humans have existed on Earth. If you consider only modern humans, we've only been around for 50,000 years, maybe.
And "modern humans" isn't a civilization; it's really all of the different, successive human civilizations.
If you could imagine that, in addition to making stone tools and animal-hide clothes, neanderthals had also learned how to freeze evolution, do you think those guys would be well-adapted to a planet-hopping future? I don't.
Eventually there would be selection for colonies that can produce faster and/or longer lived colony ships, so they can plant new colonies faster. This will eventually shade over into the more conventional galactic colonization scenarios where stars can be treated as near stationary.
A star inside the Oort Cloud might start another inner system bombardment.
This blew my mind. I never considered that stars are moving relatively each other in this way. Or more precisely, what it meant for our solar system.
The question is, can you make a ship fast enough to catch a star going past, or do you have to launch ahead of time. And do you have enough time in either case to decide if this one way trip is suicide or not.
Practically the window of opportunity for a favorable launch may not might not be that different than launching for Proxima Centauri. But at least you can soak up solar power and mine resources while you wait, instead of sitting in the dark the entire time.
A few years ago, research using Gaia data indicated that the last such close encounter was about 70,000 years ago, when the star WISE J072003.20-084651.2 — also called Scholz’s Star, after the discoverer — passed just 0.8 light-years from the Sun.
- https://www.syfy.com/syfy-wire/bad-astronomy-several-stars-h...