[Sanzig]

Provided we don't wipe ourselves out, there's no technical reason why we can't go interstellar. It's just way harder and more energy intensive than most people imagine, so I doubt it's happening any time in the next few hundred years.

But we already understand the physics and feasibility of "slow" (single-digit fractions of c) interstellar propulsion systems. Nuclear pulse propulsion and fission fragment rockets require no new physics or exotic engineering leaps and could propel a probe to the stars, if one was so inclined. Fusion rockets would do a bit better, although we'd have to crack the fusion problem first. These sorts of things are well out of today's technology, but it's not unforeseeable in a few centuries. You could likewise imagine a generation ship a few centuries after that powered by similar technology.

The prerequisite for interstellar exploration is a substantial exploitation of our solar system's resources: terraform Mars, strip mine the asteroid belt, build giant space habitats like O'Neill cylinders. But if we ever get to that point - and I think it's reasonable to think we will, given enough time - an interstellar mission becomes the logical next step.

Will we ever get to the point where traveling between the stars is commonplace? No, I doubt it. But we may get to the point where once-in-a-century colonization missions are possible, and if that starts, there's no limit to humanity colonizing the Milky Way given a few million years.

[TheOtherHobbes]

Nuclear pulse and fission fragment designs require no new physics in the same way that a Saturn 5 didn't require new physics when compared to a Goddard toy rocket.

It's easy until you try to actually build the damn thing. Then you discover it's not easy at all, and there's actually quite a bit of new physics required.

It's not New Physics™ in the warp drive and wormhole sense, but any practical interstellar design is going to need some wild and extreme advances in materials science and manufacturing, never mind politics, psychology, and the design of stable life support ecologies.

The same applies to the rest. Napkin sketches and attractive vintage art from the 70s are a long way from a practical design.

We've all been brainwashed by Hollywood. Unfortunately CGI and balsa models are not reality. Building very large objects that don't deform and break under extremes of radiation, temperature changes, and all kinds of physical stresses is not remotely trivial. And we are nowhere close to approaching it.

[Sanzig]

I thought I was pretty clear that I don't see this happening for hundreds of years at least.

The engineering problem is insurmountable today. But there doesn't seem to be any reason it couldn't be done eventually, given our technological trajectory, unless we believe we are truly on the precipice of severe diminishing returns in most science and engineering fields, and I just don't see that right now.

George Cayley figured out how to build an airplane in 1799, but it wasn't for another century until materials science and high power-to-weight ratio engines made the Wright Flyer possible.

There are plenty of depths to plumb in space systems engineering that we haven't even really had a proper look at yet. A Mars mission with chemical propulsion is hard, but could be made substantially easier with nuclear thermal propulsion - something we know should work, given the successful test fires on the NERVA program back in the 60s. First stage reusability was fantasy 15 years ago, today it's routine.

Obviously, I'm extrapolating a long way out, and maybe at some point we'll run against an unexpected wall. But we'll never know until we get there.

[willguest]

My idealistic part says that a combination of AI-driven technical orchestration (much more than just coding) and orbital/langrange manufacturing facilities could, perhaps, get somewhere in the not ridiculously distant future (centuries rather than millenia)

A more pragmatic me would point out that the required energy and materials needed would mean we would need breakthroughs in space-based solar capture and mining, but this is still not New Physics.

I think the solution will come from exponentially advancing self-assembling machines in space. These can start small and, given the diminishing cost of getting things to space, some early iterations of the first generation could be mere decades away. There are several interesting avenues for self-assembling machines that are way past napkin-sketch phase. Solar arrays are getting bigger and we have already retrieved the first material from an asteroid.

The quality and reliability of AI agents for processes orchestration and technical reflection is now at a stage where it can begin to self-optimise, so even without (EDIT) a "take-off" scenario, these machines can massively outperform people in manufacturing orchestration, and I would say we are only some years from having tools that are good enough for much larger scale (i.e. planetary) operations.

Putting humans there is a whole other story. We are so fragile and evolved to live on Earth. Unsurprisingly, this biological tether doesn't get much of a look-in here. Just being on the ISS is horrible for a person's physiology and, I am guessing there would be a whole host of space sicknesses that would set in after a few years up there or elsewhere. Unless we find a way to modify our biology enough so we can continually tolerate or cure these ailments, and develop cryo-sleep, we're probably staying local - both of these are much more speculative that everything above, as far as i can tell.

[Jweb_Guru]

Yeah this is something I think a lot of people tend to overlook. People are far too quick to rewrite "we don't know of any reason why it would be impossible" to "we know how to do it" in their heads.

[throwway120385]

The other thing we could do to explore the galaxy is to become biologically something we would no longer recognize. We're viewing this from the lens of "humanity must remain biologically static" but I want to point out that that's not physically necessary here and that there is life on Earth that can stop its metabolism for decades and things like that.

[stickfigure]

Or even explore with something nonbiological.

Humans evolved to live on earth. Our bodies fare poorly in low gravity, not to mention vacuum. Given sufficiently advanced technology, I'm pretty sure we could evolve some form of intelligence better suited to the environment.

[_fizz_buzz_]

We don’t have to completely wipe ourselves out to regress or stagnate. There have been many civilizations that have regressed.

[rishabhaiover]

The child within me likes to dream and this is the dream I have!

[shagie]

PBS Space Time has a hoodie for that... (the T-shirts are sold out). https://crowdmade.com/collections/pbsspacetime/products/pbss...

Why Antimatter Engines Could Launch In Your Lifetime https://youtu.be/eA4X9P98ess (3 weeks ago) ... with that T-shirt. ... and the bit about theoretically possible warp drives (4 years ago) https://youtu.be/Vk5bxHetL4s

[bena]

Yes, it's incredibly easy to do these things once you've done all these other, incredibly difficult things first.

The furthest a human has been is 250k miles (far side of the moon). The fastest a human has traveled is only 0.0037% the speed of light.

The ISS is about 260 miles from the Earth. At that height, the gravity is actually roughly the same as on the surface, it's only because it is in constant freefall that you experience weightlessness on it.

Mars is 140 million miles away. And not exactly hospitable.

I like how you treat "the fusion problem" with a throwaway, "Yeah, we'd have to solve that" as if we just haven't sufficiently applied ourselves yet.

All of those incredibly difficult things we have not even begun to do are the technical reasons we have not gone interstellar and may be the reason we will never do so.

And even if we solve the issue of accelerating a human being to acceptable speeds to reach another star, the next closest star is 4 light years away. That means light takes 4 years to reach. Even if you could average half the speed of light, that's 8 years, one way. Anything you send is gone.

[Sanzig]

It's 2025. The first heavier than air flight was barely more than a century ago. The first human in space was less than 70 years ago.

These enabling technologies are very, very hard. No doubt about it. That's why we can't do this today, or even a century from now.

But the physics show it's possible and suggest a natural evolution of capabilities to get there. We are a curious species that is never happy to keep our present station in life and always pushes our limits. If colonizing the solar system is technically possible, we'll do it, sooner or later, even if it takes hundreds or even thousands of years to get there.

> I like how you treat "the fusion problem" with a throwaway, "Yeah, we'd have to solve that" as if we just haven't sufficiently applied ourselves yet.

If you'd read my comment, you'd see I didn't say that. Fusion rockets would help, but we don't need them. Nuclear pulse propulsion or fission fragment rockets could conceivably get us to the 0.01-0.05c range, and the physics is well understood.

> And even if we solve the issue of accelerating a human being to acceptable speeds to reach another star, the next closest star is 4 light years away. That means light takes 4 years to reach. Even if you could average half the speed of light, that's 8 years, one way. Anything you send is gone.

Getting to 0.5c is essentially impossible without antimatter, and we have no idea how to make it in any useful quantity. Realistically, we're going there at less than 0.1c, probably less then 0.05c. Nobody who leaves is ever coming back, and barring huge leaps in life sciences, they probably aren't going to be alive at the destination either. It'd be robotic probes and subsequent generation ships to establish colonies. But if you get to the point where you are turning the asteroid belt into O'Neill cylinders, a multi-century generation ship starts to sound feasible.

[7952]

And once you have done those incredibly difficult things it is possible that the game changes entirely. A significant number of humans could live in space and have limited contact with planets.