94% of the universe’s galaxies are permanently beyond our reach

If this fact makes you uneasy just know that (nearly) 100% of the galaxy's solar systems except the one we're currently in are (likely) unreachable within your lifetime.

Though to be fair, I think the original title can't possibly know this, for instance if we live in a simulation, what's to say that some sort of algorithm (assuming we learn to meta-code our own existence) could put us in any galaxy we choose... Or warp drives, worm holes... light speed travel hardly seems worth the trouble, and unfeasable.. but if we can master warp drives, and bending space around us... then is there a limit on max speeds? If we can actually reprogram the universe would there be anything we couldn't do? have any other alien civilizations realized that at all?

Pretty much true for all other stars as well… we’re not visiting anywhere soon

That depends on whether the singularity people were right after all or not.

Mmmh. Probably.

I'd throw an asterisk on this... technology advances in ways we don't expect, and the definition of "lifetime" might become very fuzzy very quickly.

(I don't think I'd put 50/50 odds on it... but I wouldn't put 1/99 odds on it either).

Not with that attitude!

Longevity escape velocity is achievable within our lifetimes.

In case somebody doesn't get the joke: https://news.ycombinator.com/item?id=18120477

lmao bill gates

I would use magic for something more interesting than looking at rocks flying through empty space.

* or time travel / manipulate space-time

This is a really great question that embodies the hacker spirit of trying to find loopholes and edge cases. I'm not an expert, but I think the answer is that there are no half-reachable galaxies. If there is a galaxy that is only partially reachable, then it must eventually be torn apart by the expansion of the universe. We could theoretically send a ship to the reachable half, and if the galaxy was still in one piece, we could then take a quick jaunt from the reachable half to the unreachable half. So for the unreachable half to be actually unreachable, it would have to be far away from the reachable half. I'm guessing that all galaxies have strong enough gravity that they won't be torn apart by the expansion of the universe.

Reachable and visible are different things. There are plenty of galaxies that are visible, but not reachable. But I think a similar argument would apply to show that there are no half-visible galaxies. Light can certainly make it from one side of a galaxy to the other. If we can see the light emitted by the near side of the galaxy, then we can see light that originated on the far side of the galaxy and passed through the near side on its way to us. Both sets of photons will reach us, and both will have about the same redshift. The only difference will be that the the photons from the far side of the galaxy will be a few thousand years older than the near ones. (This is all ignoring the fact that we can see all the way back to the cosmic microwave background, which comes from a time in the universe's history when there were no galaxies at all. Anything we can see that looks like a galaxy isn't even on the visible/not-visible boundary!)

No. The proper boundaries are between galaxy clusters, which remain gravitationally bound to each other. If you can reach a cluster such that its gravity is strong than the expansion of the universe, then you can reach every part of that cluster.

> Something in my mind tells me that there must be more to it, the careful balance of universal constants that allow for matter and stars and life to exist surely would not allow it all to be destroyed forever in the end...

Keep in mind that we don't really understand this stuff.

"Dark matter" isn't a weird phase of matter, it's the name of the Keleven inserted because our observations of the universe don't match up with the theory. Ditto "dark energy."

The expansion of the universe is accelerating and we don't know why. If we don't know why, we don't know it isn't going to stop tomorrow, or reverse, or happen differently based on where you are in the universe. The things we've already observed about relativity and quantum mechanics are very counter-intuitive.

But at the same time, "I don't want it to" doesn't mean it's not going to happen. The arrow of time goes in one direction. We don't know how it ends until we get there.

> the careful balance of universal constants that allow for matter and stars and life to exist surely would not allow it all to be destroyed forever in the end...

Imagine a brute-force creation of x^y universes with varying cosmological constants. Surely some universes with the right ingredients for life also include a deep freeze or a Big Crunch.

Or, maybe our universe was created in a lab somewhere and they’re trying to figure out how to make a stable universe through experimentation. And we’re iteration #42.

I saw a video proposing that it might be possible that the universe collapses on itself again and everything is reset.

But there are more non reversible things going on than just expansion. I only just found out that all elements radioactively decay and will eventually be gone.

If we phrase it "we're permanently beyond the reach of 94% of potentially malicious alien cultures," does that help?

Just to add to it:

If you decided to travel to the furthest galaxies you could reach, at some point even they will move beyond the reach of Earth as space expands. To colonize them means to exile yourself from Earth permanently.

Traveling through an infinitely expanding universe is like traveling into a permanent headwind in every direction.

6% of galaxies ought to be enough for anybody. :)

My point is, the physics also apply to a smaller scale.

According to this image: https://bigthink.com/wp-content/uploads/2021/10/In-enough-Ti...

When you stand next to somebody and you look at this person, through the expansion of the universe and the amount of time the light needs to travel from the surface of that person, to your eyes; means that when you see this person in the original distance, you do not see that person at the actual distance. It's not possible to share a contemporary timeline with other persons, everything is a few nano seconds delayed, you are existing in everybody else's past.

Of course practically this doesn't matter.

If this does but life doesn't, you're doing well

why? it was never going to matter to you. any of us here will be outliers if we even make it to orbit

Why?

If we're in a simulation...couldn't we learn to reprogram/hack the sim, and just put our spaceships in another galaxy?

The expansion of space itself is not subject to the same constraints as travel through space.

Put another way: Nothing can travel through space faster than light. But the expansion of space itself isn’t a form of travel, and so it’s not subject to this limitation.

Expansion isn't objects in space moving farther apart through space it's the change in the geometry of space itself. A poor analogy might be a continuous zoom of a map map on your phone while something always moves less than a constant speed limit of pixels per second on the screen. It is easy to see this object can move around locations on the map but may not be able to reach most of the map if it is zooming in fast enough that far away portions !at get farther away faster than it can travel to them at the constant pixels per second.

The expansion of space doesn’t fall under that limitation. Spacetime isn’t a particle or collection of particles. It’s the gravitational field.