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Comment by glomgril | Hacker News Reader

Very cool. Got a silly sci-fi question for you. IIUC, with current technology it would take on the order of tens of thousands of years for a vessel to physically travel to the closest known Earth-like planet (correct me if I'm wrong).

So any thoughts on what kinds of hypothetical breakthroughs would be needed to make the trip doable in (say) less than a human lifetime?

And related, what do you think about the plausibility of the [Breakthrough Starshot](https://en.wikipedia.org/wiki/Breakthrough_Starshot) initiative? Aware of any alternative approaches?

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A different stab at this is to ask what it would take to build a telescope that could image some of these Earth-like planets, a project that turns out to be easier (in a very loose sense of that word) than sending cameras there.

The idea is you send a camera very, very far out in the Solar System (hundreds of AU) and then use the Sun's gravity well as your lens. Neat stuff and, unlike the interstellar probes, potentially doable in our lifetime.

https://en.wikipedia.org/wiki/Solar_gravitational_lens

Normally, diffraction and the effective aperture are what limit optical resolution. How does that work with gravitational lensing? Does the effective aperture become the diameter of the sun?

I'm too ignorant to answer that, but the technical paper here [https://arxiv.org/pdf/2002.11871] goes into a wealth of detail, and includes an image of Earth as it would appear to such a telescope (before and after post-processing) from 30 parsecs away. The optical properties of the solar gravitational lens are pretty astonishing.

Self replicating automata as described by Von Neumann able to repair and duplicate themselves, and other things like electronic components. ICs keep getting faster (so far) but use smaller and smaller features of silicon and could wear out from metal migration and all components will be under much more cosmic radiation than on earth. This makes a large shield of heavy material on front of vehicle to minimize this effect but that increases the energy/fuel needed. The space shuttle only took maybe week long trips but it had four computers for flight control , three extra in case of failure in different parts of the shuttle along with IIRC a separate backup backup computer in for use as last resort.

* Research faster interstellar travel, especially using something like a Buzzard engine to utilize interstellar hydrogen as resection mass. Required nuclear fusion power plants / engines and ridiculously strong magnetic fields; both seem attainable.

* Slow down human body metabolism and allow humans to stay asleep at near-freezing temperatures for a long time. If bears and chipmunks can do it, chances are humans could learn it, too.

* Invent sets of machines that can reliably self-replicate, given most basic inputs like minerals, water, and sunlight. Advanced semiconductors are going to be the tricky part.

* Study psychology, sociology, history, game theory, etc, so that the early society that will form on the new planet, isolated from Earth, would avoid at least some of the pitfalls that plagued human history on its home planet.

> Buzzard

That's a bird, the engine is named after a person and is spelled differently:

https://en.wikipedia.org/wiki/Bussard_ramjet

Also, it won't work unless scaled up to the sort of thing only a Kardashev type II could do — 4000 km diameter — and at that level you've got other options that mean they probably won't:

https://arstechnica.com/science/2022/01/study-1960-ramjet-de...

The reason being the interstellar medium is way less dense than we thought in 1960.

>Slow down human body metabolism and allow humans to stay asleep at near-freezing temperatures for a long time. If bears and chipmunks can do it, chances are humans could learn it, too.

The thing is - our current bodies can't live in space for long. So either we will have to build new bodies for us somehow or build a ship that can have gravity inside and protection from space outside (and we are talking about very heavy protection here)

In any other case there is no point in slowing down metabolism or whatever. You will die rather soon.

With a big enough ship, pseudo-gravity can be easily produced by rotation, especially if we expect the crew to spend 95% of time asleep.

Time dilation means that the closer you get to the speed of light the less time you experience passing. So even a 12000 year long journey as seen from earth, if moving fast enough, could feel to the travelers like a much shorter amount of time.

And we don't have to send people, we should do our job as a Von Neumann probe and send frozen rna to distribute across the surface.

In space culture this is widely considered a dick move.

and in that 10,000 year blink, a civilization progresses from bronze metalworking to digital computers, awaiting our arrival

Yes, but practically with todays technology there is no feasible way of getting to a speed where time dilation matters over that distance, we run out of fuel so we need some external power source like a laser or solar wind that have other issues, iirc one only gets to 2x time dilation at 0.9 c. That’s a lot of acceleration.

We need to think about where we want the knowledge and what knows it. We could use humanoid AIs. We could hatch humans "just in time". Run them in a sim to 18 then release them on their mission. Ethics would need to accept this. Maybe we would be happy slowly expanding across the universe and an decendant talking to 'the aliens'.

I am not totally serious. But you wanna meet aliens? Gotta do something a bit radical.

If you haven't, you should read Accelerando, it's a collection of short stories IIRC that were put into a novel by the author. I didn't want to start with that, but that is in there. :)

I'm reading Accelerando right now and there's some unnecessary weird sex stuff at the start.

Good book despite that though, some very interesting ideas.

My one-sentence review of Accelerando is "VASTLY better than the first couple chapters will make you believe."

If I may suggest another read: Perfect Imperfection by Polish author Jacek Dukaj. It's definitely weirder, than Accelerando, as the book drops you straight into the last parts of evolution curve, but definitely worth reading if you have liked Accelerando.

The story is super weird, but what I found out is that piecing together a picture of a far-future society from this story was very exciting.

I imagine fuel isn't that big a problem until you care about being able to decelerate once you arrive.

Can't pulse nuclear get there? Or does it require antimatter catalyzed fission?

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