Now there are 2 caveats to this - first, there is a measurable density difference as you get closer to the galactic plane. And second, globular clusters do do their own thing.
What this means for fiction is that you must commit to either:
* The overwhelming majority of systems must be irrelevant; relevant systems are hundreds of lightyears apart (it is trivial to disappear into uncharted systems assuming you can maintain your spacecraft), and galactic structure does matter. Or,
* If even a modest percentage of systems are to be relevant, then you can't care about galaxy-scale structure at all. And you need to have something stopping people from gratuitously flying out of bounds (this might be as simple as "no compatible languages and no compatible fuel pumps").
But that means that galaxy-scale structure actually does matter, right? A hundred thousand sun-like stars isn't all that much, I'm guessing only a small percentage-points of those would have a planet in the correct orbit for terraforming, and you'd need to go outside your proposed 1000 LY volume?
However say red dwarfs with moons of closely orbiting gas giants, and many other combinations could in theory be sustain life easily .
We can learn from history on earth, economics is the reason why cities or outposts form and die, even when they are very hostile or very unsuitable and expensive to make it work.
Space would be no different, people would be happy to setup an outpost on Betelgeuse despite its impending supernova if they can say get away from regulation or it cheaper to make things for some other reason, or there is ideal low gravity planet with the right conditions for growing some thing even it would normally be considered hostile .
If there were galactic empires like you see in science fiction, the amount of administration required to deal with that many systems would be mind boggling, the volumes of data would be staggering.
At the scale of interstellar empires machines are have to do most of the administration. You cannot centralize so much bureaucracy without computers involved .
I understand the need for science fiction to focus on the human drama, but trying to have empires and be anti-machines is unrealistic.
Then I like to say the nearest next start is roughly 4 light years away. So even at 17km per second, or about 10.5 miles per second, it will still take approx 72,000 years for it to reach the nearest star.
That star is 4 light years away and our galaxy is about 100,000 light years across. The next galaxy is about 2.5 million light years away!!! So at the incredible speeds of one of our fastest man made objects it would take something like 45 billion years to just get to the next galaxy!
Seeing how the known universe is estimated at over 46 billion light years in size and looking back on the other numbers I wrote it quickly becomes apparent that to travel across the galaxies one would need to be able to reach unbelievably unimaginable speeds. Even the speed of light as you mention would not be even close to fast enough to get anywhere significant.
On a side tangent I was always a trekie back in the day. I know their warp drive was faster then light but now I almost want to go back and look at the math of how fast they must have been going to be going the distances they were going.
While there's a rough polynomial (v =~ c * w^3, I think) for post-TOS Star Trek warp factors, the only consistent rule: a starship travels at a velocity that helps tell a good story.
It's fun to try mapping Star Trek stories, anyway; it helps you ponder how much time they must have spent in transit. They have to find things to occupy their time.
But I absolutely loved the show growing up so not here to knock them. I am sure in hindsight they may have come up with a better definition of how warp speed works and how they can travel great distances. I won't think about it too much.
I have never seen anyone writing about us having solid reference points to travel that far in case we can reach those speeds.
If you miss you end up in some empty space you won’t be able to mine anything for fuel to have more shots.
I'm not sure if the CMB itself will decay fast enough with the expansion of the universe to avoid 1g eventually getting you hull eroded by positron-electron pair production from photons blueshifted above 1022 keV, but that's in the set of things you need to think about.
This just shows a juvenile and naive level of thinking. You can't spend 72,000 years with our current brains in full conscience without going insane.
Estimating time-to-arrival when your destination is also moving at ludicrous speeds is incredibly difficult.
The crazy part is that this 3D game was programmed in 68k assembly, ran smoothly on Amiga and Atari ST home computers, and fit on a single 1.44MB floppy. The massive universe with realistic solar systems was almost entirely procedural.
If you go close enough to the speed of light, what you actually see is that space appears to shrink (in the direction of travel) and the trip seems to take less time than light would, because you've apparently covered less distance. Of course what those on the planets would see is that time has been moving oh so slowly on your otherwise speedy ship. There are equations you incorporate into a simulation that would account for this. If the game mechanics were such that you could could see what day/month/year it is in local time, vs your ships time, it would quickly become apparent that bashing through the void is no way to get anywhere.
Time dilation is just shortcut to say you are no longer sharing the same frame of reference. If everyone has their own frame of reference there is no difference between single player game and multi player one
To me, it's a pitty that Braben finally dropped realistic newtonian physics (limited velocity is simply a plague in 99% of space games, period... and sure, I don't talk about FTL travel) in such realistic scales. Complete paradox.