[Johnny555]

I'd be interested to know what possible commodity would be worth trading among star systems -- even if some star system has a planet made entirely of diamonds, surely it would take far less energy to made them here than to ship them between stars? Likewise, it seems that endless amounts of gold (platinum, rhodium, whatever) could be harvested from our own solar system before it's worth shipping here.

Even if there's some alien truffle delicacy that only grows in the shade of a tree bathed in UV light from an alien star, surely that could be cultivated here in an artificial habitat far easier than shipping it light years across the galaxy?

[ranger207]

The excellent Atomic Rockets site is designed as a reference for realistic sci-fi, and has a page on MacGuffinite, aka something that makes space exploration economically viable. The long story short is that there's really not all that much that can't be done here on Earth or at least in low orbit.

http://www.projectrho.com/public_html/rocket/macguffinite.ph...

[TaylorAlexander]

Information.

Personally I imagine we're better off when we share information for free, but I haven't tested the hypothesis.

[dghughes]

Aww dang it, I didn't see you wrote information first.

And here I am thinking I was being insightful.

[elihu]

Novel life forms and technology could be valuable, especially technology that's hard to replicate (due to proprietary processes/trade secrets or whatnot).

Fissionable materials might be valuable to planets that have none of their own and want to make use of nuclear power.

People are a resource of their own that may be wanted on sparsely inhabited planets (especially if birth rates on technically advanced planets are similar to those in developed nations here on Earth).

[icanhackit]

> what possible commodity would be worth trading among star systems

Apart from information which has been mentioned twice I'd say habitable and highly hospitable land (Earth-like planets) as well as access through or even ownership of territory. Space might be big but if we're limited by the speed of light then these things have immense value and still considerable value if we're somehow able to get around it.

[scarmig]

Thinking in the very long term... energy?

Though even that, it seems it'd be cheaper to transport the people to the energy than vice versa.

[Johnny555]

Every form of interstellar travel I'm aware of requires lots and lots of energy -- it seems hard to imagine a source of energy that's capable of being transported between star systems that's not dwarfed by the energy used to transport it.

[nickjarboe]

One time pads for encryption(Vernor Vinge's "A Fire Upon the Deep").

[dghughes]

Information.

[TheOtherHobbes]

I doubt this. In fact I doubt the idea of interstellar trade.

Beyond a certain point of post-scarcity, everything stops being scarce, including invention and innovation.

We're already at that point with artefacts like music. Aliens could turn up tomorrow with centuries of unique music, and after the initial decade or five of novelty the music would end up as yet another playlist on Spotify, among countless others - so many no individual human could ever listen to more than a tiny fraction of them.

That's a rather silly example, but the point is still valid: if you imagine the same trend occurring in physics, biology, and technology, you end up at a place only a few centuries from so much novelty and invention is being produced that it's no longer a scare commodity. External sources might add a few minor tweaks to the generation system, but when even game changer technology stops being scarce, what is there left to trade?

[icanhackit]

> I doubt the idea of interstellar trade [...] Beyond a certain point of post-scarcity, everything stops being scarce, including invention and innovation.

Right but wouldn't you need interstellar trade to reach this milestone of post-scarcity? Otherwise you'd have to assume all forms of invention are achievable with the resources you start with.

Wouldn't game theory make you want to limit the resources and capabilities of your neighbor in case they try to do the same thing to you? So this idea of post-scarcity is never met because the uncertainties of attack from any number of other space-faring civilizations requires that you invest a significant chunk of your resources into your military. You could also have internal turmoil - the human race splits into distinct civilizations with different political, social and technological goals.

[dghughes]

Maybe we would be so far behind they would find something lost to them hundreds of thousands of years ago.

It's funny you say music I've always thought every pop song has been made but then someone makes a new song that everyone loves.

[ieatkittens]

Spice