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The Theory of Interstellar Trade (fermatslibrary.com)
107 points by alokrai on July 16, 2018 | hide | past | favorite | 180 comments

Any civilization that has mastered interstellar travel will almost certainly also have mastered atomic transmutation as well. So as long as all the interesting stuff is made of atoms, and the atoms over there are the same as the ones over here (which AFAWCT they are), there are only two possible "goods" that could be worth transporting between star systems: information, and free (in the physical, not the economic sense) energy. You don't need a space ship to transfer either of those, you just convert them into photons and let Maxwell do the work. The idea that it might be worthwhile to actually ship something (including ourselves) to another star system is based on very quaint notions of identity binding and what it takes to produce things.

Sending light across interstellar distances is not a trivial affair. No light source is perfectly collimated; per wikipedia [1] "The divergence of high-quality laser beams is commonly less than 1 milliradian, and can be much less for large-diameter beams". Not clear how "much less" is (and I couldn't find other sources), but let's say it's 2-3 more orders of magnitude. That would make it about 1 arc second (~5 microradians). The closest star is at a distance of about one parsec, which means that two photons starting here and having an angle of 1 arc second between them end up at a distance of 1 AU (astronomical unit ~ 150 MM km) between them. Assuming you can make an antenna the size of Jupiter at the target, for every photon that passes through that antenna you need to send 1 million photons. Every order of magnitude lower in the size of the antenna requires you to send two orders of magnitude more photons. In other words, an antenna 1% the size of Jupiter requires you to send 10 billion photons for each photon received.

You can get around that by setting up a system of relays, but you will end up needing lots of relays, and that's a complex infrastructure you need to maintain.

In any case, even after we master inter-stellar travel, don't think we'll have channels of communication of terabytes/second, every byte will be expensive to send across.

Sending information in the quantities needed to 3d-print stuff at atomic level will most likely be prohibitively expensive; remember 1 gram of hydrogen contains 10^23 atoms, while one terabyte only contains 10^12 bytes. If a little latency is acceptable, it will always be many times cheaper to just send the stuff you need rather than the information to 3d-print it at atomic level.

[1] https://en.wikipedia.org/wiki/Collimated_light

> Sending light across interstellar distances is not a trivial affair.

I never said it was. But it's a hell of a lot easier (to say nothing of faster and more efficient) than sending matter.

Not necessarily. Remember, photons have mass. Sending a lot of them means you perform mass transfer. Since photons are not parallel, that transfer is not efficient. It's probably much more efficient to send a small package equipped with a large solar sail and push it from behind with a big laser until it reaches a relativistic speed, then decelerate it on the other side with another big laser.

The concept that photons are massless entities is founded in obsolete information. It has long since been determined that photons do in fact carry mass.

When photons were initially conceptualized, the capacity to estimate their mass was too small to measure and thus prove to experimentalists. Theorists, therefore, focused on other concepts and problems.

Taking a look at the link you've provided actually reaffirms this fact. Mote that it is a question from a novice, and the very first answer refutes the idea that photons lack mass.

  In other words, a photon does have 
  relativistic mass proportional to its 

  And here we have it: photons have 'mass' 
  inversely proportional to their wavelength! 
  Then simply by Newton's theory of gravity, 
  they have gravitational influence.
Keep in mind that the top google results for stack overflow style Q & A forums aren't always going to line up in favor of your search queries.

You should read the top answer, since it's more likely to contain reliable facts, and not presume that the ideas expressed by the question are essentially correct.

Sorry I was trying to make the point that photons do not have mass in the same sense as other particles, they have no rest mass.

Hm, that's a good point. Doing the math on that would make an interesting exercise.

Ok, here's the math.

Solution 1: send information with a highly collimated laser. Assume 1 arc second divergence of the light beam and a distance to the nearest star of 1 parsec (the actual distance is 1.3). The diameter of the circle of light at the target is 1 AU. Assume there is a listening antenna at the target of the same size as the largest radio telescope today, which is 500m [1]. The ratio of the area of the telescope and the area of the light disc coming from the source laser is (500m/1AU)^2 = 10^(-17). You want to send about 1Tb/s of information. 1 bit/s requires about 4zW of power [2], so you need the antenna to receive about 10^12410^(-21) = 4e-9 W. You need to send about 10^17 more at the source, that means about 4e8W, or roughly 400MW. Let's make that 1GW, to account for various other inefficiencies. That's actually not so bad.

Solution 2. Send a package in a solar sail powered vehicle. I don't know how to do the math, but fortunately wikipedia has some examples [3]. A randevouz with Alpha Centauri for a vehicle with a final mass of 71 tons can be done in 41 years, and requires a power of 7200 GW here and 26000 GW in Alpha Centauri (for the braking stage). Let's say out of the 71 tons vehicle at the end of the trip, only 1 ton is useful cargo, and you fill that with SSD drives. Currently the largest SSD drive is about 100 TB, and it weights about 100 grams. That's 1TB/g, or 10^6 TB/ton. That's about 100 days worth of transmission at 1 Tb/s. So it wouldn't seem remotely comparable with Solution 1. However, by the time we reach the stars, I can easily see the information density going up by a factor of 10^20 or so.

So that's that. If you want to send information at limited bandwidth, you can send it using a big laser. If you can afford some latency (40 years instead of 4y), then you can send it by putting a lot of hard drives in a package.

[1] https://en.wikipedia.org/wiki/Five_hundred_meter_Aperture_Sp... [2] https://en.wikipedia.org/wiki/DBm [3] https://en.wikipedia.org/wiki/Solar_sail#Swing-by_maneuvers

Uh, aren’t you just sending billions of photons then?

Sorry, I must be missing something, as this seams like you’re spending photons to move a package rather than just sending photons.

The problem is that all light sources are to some degree divergent. You can accelerate a package to a relativistic speed over a distance of the order of 100AU, which is thousands of times less than the distance to the closest star. Consequently, the light beam that you send spreads out thousands of times less over this distance. It’s still a lot, but you have a fighting chance.

> will almost certainly also have mastered atomic transmutation as well

I don't see any reason to think that's true.

Why not? If stars can do it, why not a sufficiently advanced civilization?

What indicates that Interstellar travel requires a technological level that includes arbitrary transmutation? It seems to me travelling these distances is much simpler, it basically just requires current technology plus organisations that can hold together for more than a century or so. If you take the only known civilisation as an example: Ever since the invention of atomic bombs we have the propulsion part of what's required to go to ~40% the speed of light (or ~20% and then break). The most difficult challenge yet to overcome would probably be the front shield (at relativistic speeds, space dust can really mess things up), but that seems far from unsolvable. The main thing missing is political will to take the required risks. We were well on a path to such a machine in the 60ies, what failed was mainly politics in the two organisations large and advanced enough to do it (USGov/UdSSR).

> What indicates that Interstellar travel requires a technological level that includes arbitrary transmutation?

It seems likely to me that mastering fusion will be a pre-requisite for interstellar travel. But you're right, that's probably the weakest part of my argument. So maybe there will be a market for rare shipping rare elements across interstellar distances.

That seems likely - my guess is you'll need sufficiently efficient energy to power electromagnetic shielding. Although an old Submarine-style nuclear fission reactor might be just fine for that as well, and you won't have to worry about just venting spent fuel rods into vacuum (in a nuclear pulse type spaceship that bit of radiation is going to be the least of your worries...).

Why not? We started atomic transmutation with fire.

Chemical reactions are a subset of atomic transmutation. Arbitrary atomic transmutation is likely a superset of all possible atomic transmutations

Categories. It's all categories.

It's likely the superset of some transmutations. Categories or not, one precedes the other (for anything that we understand).

I used to think that was true. But then I researched practical interstellar travel methods (not quite relativistic, 0.1c), and they seem doable from a physics and engineering perspective (if you controlled the world's wealth), but we have no real executable plan to build a transporter.

We could probably build an interstellar probe if we redirected the world's defense spending into the project for a decade or so. Nuclear pulse propulsion looked viable fifty years ago and the projects were only stopped because of the test ban treaty. A ship powered by nukes can reach single digit percentages of the speed of light. That's enough to reach the nearest stars in one or two generations.

I was thinking of a crewed vehicle. And yeah, redirecting defense spending should do it.

For a mere probe, especially a microprobe, Breakthrough Starshot is probably the best approach and it is potentially 10% to 30% c and cheap per probe. Wouldn't necessarily cost that much, either, although the engineering is pretty... aggressive. If the engineering issues could be solved, might be able to do it for the same cost as ISS ($100 billion).

Animation: https://www.youtube.com/watch?v=xRFXV4Z6x8s

Not to mention that transporters (disassembler/reassemblers) are (a) murder machines, and (b) cloning machines.


As far as I can tell, this "me" and that "you" exchanging thoughts right now, are one offs, a delicate state, aware.

One day, cloning, assumung we can do it in a non destrucrive way, and I am not convinced that will ever be true, would make another one.

That one will diverge quickly from us as it's experiences would differ.

I am not convinced it is possible to avoid that happening either.

The transporter is such an interesting idea! But, using it would have to come with a bit different idea and acceptance of identity.

The idea of a "me" continuing on, doing what I would have done, is plausible. The shared experiences make for a reality, also shared.

That is where identity would lie.

To understand if we are talking to a Kirk, post transport, our validation would basically be done with what is known, shared among those asking the question.

It is all like sleeping, only to wonder if the same person awakens.

In terms of a body holding a state, stream of experiences, yes. But, in terms of that person, as in would they pass the "talking to Kirk?" test, perhaps not.

Ever meet someone after a coma, or even long surgery and experience a lack of congruence? Does not always happen, but it can.

That is an example of that state being changed, yet the stream of experiences remaining intact. (As much as it can during times of long sleep, coma, and so forth)

Not to trivialize the great unsolved question of WTF is consciousness... I think it's a bit easier to reason about this problem than you think.

For example, generally Star Trek wants us to presume the murder and cloning occur simultaneously. Let's say they don't. In the case that the murder occurs before the cloning, the waters are admittedly still muddy. Is it, in fact, like waking up from a sleep? Not very easy to tell.

However, if we presume that the murder occurs after the cloning, things become quite clear. There can definitely only be one physical me in which I am conscious -- I feel comfortable rejecting an assertion that I would experience multiple simultaneous consciousnesses of a sequence of atomwise clones.

Therefore, we work backwards. If I can't experience more than one consciousness simultaneously, then I can't experience two. If you clone me, I am not that clone, I am still the original. As the time between cloning and murdering (t) approaches zero, the same holds true. I am comfortable asserting there's nothing special about consciousness that would cause instantaneous consciousness transfer as (t) reaches zero and then becomes negative. Therefore a transporter clone will not be me from my perspective. Therefore the murder is my death, and the cloning is a birth of a new completely separate consciousness that I will never experience.

> If I can't experience more than one consciousness simultaneously, then I can't experience two.

One of you can't, but two of you might be able to :-) Kind of like how one core can't do real simultaneous multi-tasking, but two cores can.

Right. From a purely material standpoint, I agree that from the outside perspective, there are two identical MEs and any claims to legitimacy, originality, or specialness will be completely dubious.

But I think it's easy to demonstrate that it would not be like waking up and the "true original" would definitely die in that it would not experience the clone's consciousness

> it's easy to demonstrate that it would not be like waking up

Really? How would you demonstrate that?

If you do not believe the parent of your last comment does so I would like to hear your thoughts

Imagine that we have the technology to cryogenically freeze and revive you with your subjective sense of self intact. Now consider two scenarios:

Scenario 1: We freeze you, move your body to a different location, and revive you.

Scenario 2: We freeze you, make an atomic copy of the frozen version of you, move the copy to a new location, and revive the copy.

(The reason I want to freeze you rather than simply anesthetize you is that I want there to be no possibility of any physical changes to your body or brain while you are unconscious.)

Unless you are a dualist, you must concede that your external behavior after being revived must be the same in both scenarios. So any experiment we do on you must have the same outcome in both scenarios. So no experiment can determine whether your subjective sense of self is the same or different in the two scenarios.

It's very inexpensive to create nearly exact replicas of artwork, yet people are still willing to pay a lot of money for the original.

So maybe people will be willing to pay lots of money for hand-crafted alien artwork.

That is similar to the answer I came up with in high school, about 40 years ago.

Artwork, objects of note, curiosities with provenances, tourists, off the grid information that needs to remain _really_ secure, spies, traitors, patriots, displaced peoples, artefacts bound to a religious, gifts, bodies, deceased bodies, prenatal bodies, slaves, sex objects, objects of devotion, objects of derision, pariahs.

I actually wrote a short story about a trade empire that was built by a race of aliens (they looked like lizards) that had odd religious beliefs that required them to build monasteries all over the galaxy, and staff them with praying monks.

The monk's duties were very simple, each day they had to silently read from a small paper prayer, then burn the strip of paper over a candle. The rest of the day they partied, got drunk, had sex (monks could be of either gender), or wrote non-prayer literature.

Writing prayers was an unforgivable sin, the prayers had to come from the home planet. There was a huge fleet of trade ships created to deliver the paper prayer strips in bulk.

In return for the land for the monasteries, the alien lizards would give rides on their space fleet. They had single use vouchers that went from point to point, and they had travel passes which allowed general travel. Basically a bus pass for the galaxy. And since they had a monopoly on FTL ships, they delivered mail.

One day the prayer ships stopped coming. Everybody goes bananas. Nobody travels. Economies collapse.

Plus somebody has to feed the monks, and keep them entertained or else they go on party binges. Can't let them starve, because the ships might start coming again.

A generation later the ships start showing up again. No explanation given, and it's impolite to ask. The kind of impolite that gets you cut out of the prayer circuit.

That was all backstory, the actual story starts with an undercover agent from Earth getting sent to the lizard homeworld to try and find out WTF. He only has partial passage and a small consignment of trade goods. The backstory got backfilled as the agent wheeled and dealed his way towards the home world. I did have an ending, but I think I'll not spoil it in case I ever want to try and rewrite the story.

My 17 year old prose stank, unsurprisingly; even at that tender age I could smell it. Not sure I can do better now, but who knows.

Well I think the idea and world you’ve described is awesome, so I encourage you to give it another go if you have the time!

Indeed, I would love to read a story like that!

Get writing. I think I might pay a dollar or two to read that.

Write. I believe people would read. I would.

Perhaps that's the great filter before us: can we learn to appreciate sans ownership?

Art with provenance from a dead artist is proof-of-work for an inflation-proof durable store of value.

(It remains subject to supply and demand -- the market for the particular work, artist, genre, or overall art market. But the piece itself is a one-off, and cannot be diluted.)

>The idea that it might be worthwhile to actually ship something (including ourselves) to another star system is based on very quaint notions of identity binding and what it takes to produce things.

I often think that the forms we take on now aren't suited for space travel (unless you consider living on a planet that is in motion through space as space travel) much less staying in low earth orbit for a year. We have to bend backwards to engineer materials to shield our presently fragile bodies, imo quite futilely, from the harshness of space. I think we'd be much better off modifying our bodies (or even rethinking what constitutes a body/form) to be able to withstand this harshness, at least in the interim before we can build a system that can somehow propagate energy FTL, though I definitely think we should pursue the latter, as the benefits could be realized on earth.

Some people would value getting an original whatever item and would pay a premium for shipping, rather then just getting it replicated. Extremely wealthy people would show off all the original non replicated items they posses from far away civilizations.

That is only true because we don't yet have the technology for making atomically perfect copies of physical objects. No one pays a premium for "the original" of a digital image.

And human beings, and good luck convincing anybody to jump into one of those things...mostly because doing so is more or less dying.

You're probably right but arguably sending traditional sense goods is in a certain sense sending information and energy i a single package. With enough density it might make more sense to ship the good then the energy and information used to create it.

Cells might be worth transporting. Although the DNA can be sent as data and reconstructed, de novo reconstruction of the rest of the cellular machinery needed to run the DNA might not be practical.

A seed universal constructor would be worth transporting. If that is a machine or a ship with cryogenically frozen human of all ages is a topic for another day.

Why humans of all ages? Young humans could grow into old ones, but not vice versa.

It's easier to use human to raise other humans than to hope an AI gets it right.

If you need them quickly, like ‘human to go’.


"As far as we KAN tell"?

I probably started out thinking "As Far As We Know" and then mentally veered at the last moment. Thanks. Fixed.

Would have been well retconned as as far as we know today

Where I think you're wrong is that you seem to assume there's a path to arbitrary transmutation. It may not be possible, and I would argue, almost certainly isn't.

Do you see some fundamental limit other than energy?

Containment, which is somewhat of a practical limit, and somewhat fundamental.

Now I'm no fusion expert, and frankly neither is any human since we can barely get tiny amounts of hydrogen to fuse at all. But point being, I'm not a physicist, I'm in software. So take my understanding with a grain of salt.

However, while we theoretically can fuse arbitrary elements (and add neutrons for heavier elements so they don't instantly decay), I'm pretty sure there's no known, theoretical, or speculated material or process that can contain and capture the results of fusing some elements to, say, uranium. The extraordinary energy levels required pretty much means you need a supernova. And I'm not one to suggest that in the future we'll magically be able to engineer something to contain supernovae. Quite the opposite, I'm comfortable saying no civilization will ever do this no matter how many quintillion years they try.

All this being said, there is definitely an inflection point where it costs orders of magnitude less energy to mine an element and rocket it to a destination than to fuse it on demand.

Sometimes people complain that this takes time and we need the thing now, but that's fine. Once you set up the supply line, all that really matters is throughout and interruptions, since arbitrary latency can be overcome by a continuous stream of material floating to you. I mean, sure, it'll cost latency to ramp up or down the stream, but if engineering is One Thing, it's trade offs. Reality's a bitch like that.

> I'm pretty sure there's no known, theoretical, or speculated material or process that can contain and capture the results of fusing some elements to, say, uranium.

Producing heavy elements in a lab is most certainly possible right now. You don’t need a supernova, just a particle accelerator. Many elements heavier than uranium have been created artificially this way.


You're right. But synthesizing enough material to be relevant to an industrial effort is a leap of engineering so large as to be beyond our capacity to imagine its possibility.

With the way that resource allocation seems to be bound by presently, if there was a war, and one/some group could some how get the resources to scale up such processes if they could seriously convince the war planners of its "super weapon" capabilities, I could see it happening even if it took a couple years to get a working prototype at scale (depending on its ability to not compete sufficiently with other resources for war to not purse such project at all). And seeing that humans haven't came up with the abilities to avoid war completely, it's only a matter of time (which may be a lot for an individual humans lifespan).

You don't think there would be any trade in antiques? Even in the modern world, just because we can reproduce something exactly doesn't mean there are many people willing to spend lots of money on something that is unreproducible.

Well, I hope that any civilization that masters interstellar travel would have moved beyond such foolishness. If you can produce an atom-by-atom duplicate, what does it even mean for something to be "the original"?


As an ex-antique dealer the difference is "the original" existed in the past and has a recorded history. In the antique business it's call provenance. A piece of rusty steel pipe mounted on a brass stand and labeled "A piece of the Maine" is worth an order of magnitude less than the exact same object owned by the ancestor of an investigator of the Maine explosion with a photo of the object with the ancestor on the wrecked ship supporting its authenticity.

Value is created by humans and something being an original definitely has an unambiguous meaning to most people. I think value comes partly from a reverence of history and I would hope that is something any civilization would cherish.

> something being an original definitely has an unambiguous meaning to most people

That's only because of current limitations of our technology. Did you read the article I linked to?

> Replace the word "planks" with "atoms" and you have a modern version of this puzzle: if you replace every atom in an object with a different but identical atom, do you end up with the same object or a different object? The collection of atoms you end up with after the replacement process will be completely indistinguishable from the collection you started with, so on what possible basis could you call the new collection "different"?

What's different is their history. Sure, one couldn't distinguish them through examination. But with authenticated chain of custody, they are distinguishable. In a word, metadata.

You don't quite understand the argument here. This is not about provenance, this is about physics. Atoms are just as indistinguishable from each other as a copy of digital data. If you take one atom and replace it with another it makes no more sense to call one the original the other not than it does to call one copy of Microsoft Word "the original".

Suppose we wanted to sell "the original" Mona Lisa to an interstellar society. How would they be able to satisfy themselves that we had in fact sent "the original" and not a perfect copy? And given that there is no experiment that they could possibly perform whose outcome would be different, why should they care?

It's not about objects. It's about meaning. Owning a "Da Vinci original" is not about owning some bunch of atoms. It's about owning the particular bunch of atoms that Da Vinci put together.

As far as the interstellar trade goes, they would need to trust the seller. Or trust third-party experts to authenticate it. That's all that any art buyer can do.

Regarding some particular release of Word, perhaps there is a disk somewhere containing the original compiled binary. I doubt that anyone has considered such stuff memorable, but who knows? Also, given how disk storage works, that arrangement of atoms wouldn't have persisted very long. So it's not such a useful distinction for software.

> It's about owning the particular bunch of atoms that Da Vinci put together.

But that's the whole point: if you can make atomically perfect copies, then "the particular bunch of atoms Da Vinci put together" becomes meaningless. There is no such thing as "a particular bunch of atoms" in a world where the technology exists to make atomically perfect copies. "A particular bunch of atoms" is every bit as meaningless as "a particular bunch of bits", and for exactly the same reason: atoms, like bits, are actually states, not things.

In "a world where the technology exists to make atomically perfect copies", people would still pay a huge premium to have the first instance. Some forgers have managed to produce copies that were, at the time, indistinguishable from originals. But that didn't lead collectors to ignore the distinction. It just made them more nervous ;)

Edit: Another issue is that objects aren't immutable. Let's say that we could make "atomically perfect copies". But those copies would remain "atomically perfect" only briefly. And then they'd be historically distinguishable. And OK, I borrowed that from Hoffstadter's I Am a Strange Loop.

> In "a world where the technology exists to make atomically perfect copies", people would still pay a huge premium to have the first instance.

Do you see people paying huge premiums for "the first instance" of a digital image?

I have no clue. I can imagine that some collector might pay a premium for the workstation, shut down at the moment that the image was last saved. Or the dated disk image.

It doesn't become meaningless to the person who ascribes meaning to the original that Da Vinci put together. It's irrelevant to that person if perfect copies can be made, if they don't want the copies. You can't just arbitrarily claim something universally lacks meaning like that.

> It doesn't become meaningless to the person who ascribes meaning to the original that Da Vinci put together.

It does if that person understands physics. If you can make an atomically perfect copy, then insisting on "the original" is just as silly as insisting on having "the original" of a digital image.

> You can't just arbitrarily claim something universally lacks meaning like that.

I am not "just claiming" it. I have cited an extensive argument in support of that position:


Yes, is it unintuitive. But there are a lot of unintuitive things in physics that are nonetheless true.

OK, so how do you address the spacetime argument? An "atomically perfect copy" is not a perfect copy of the spacetime object. Because they diverge at the moment of copying.

It is, by definition, a perfect copy at the time it is made, albeit potentially displaced in time and space. Yes, after that they diverge, but so what? The situation is exactly analogous to making a copy of a digital image, where there is no economic value attached to "the original" because the very concept is correctly recognized as meaningless.

Value is a wholly human created concept. If humans value it, then it is valuable. Yes, one could try to re-educate people about a "more true" view of the world using the theory of quantum mechanics. Then humans would value an exact copy (how would making the perfect copy ever be possible, really) the same as the original. You don't seem to be convincing even the more scientifically minded people here on HN, but good luck with you evangelicalism. Maybe a better way to get converts is to suggest people to read Richard Feynman's book "QED : The Strange Theory of Light and Matter" for a difficult but technically correct and simple introduction to quantum mechanics. Your linked essay is quite convoluted and reads like a bunch of gobbledygook. I think most people would get more out of the Feynman book and maybe come over to the idea that reality is a very strange and anti-intuitive at the lowest, most fundamental level.

The original is more rare than a large number of perfect copies. If the aliens have had a long time to interact with people on Earth, there will be some people they "trust" more than others. The most trusted humans will be the ones who the aliens will trust to determine which artifacts are "original" and which ones are copies. The aliens will value the original, more rare, art work higher than the identical copies that less trusted people send. Similar to how the art world works today.

This original and perfect copy stuff is mostly about status and the monkey-human desire to get to the top of hierarchies. Aliens might not care about that, but they might not care about anything we have.

> If the aliens have had a long time to interact with people on Earth, there will be some people they "trust" more than others.

And how exactly will that trust be built up? Keep in mind that it takes 8 years to do one round-trip communication to the closest star. The closest inhabited star will almost certainly take longer than a human lifetime to complete a round-trip.

> How would they be able to satisfy themselves that we had in fact sent "the original"

Well, for starters, they might determine that there is no other version of the painting on Earth or nearby that is said to be "the original".

They could additionally investigate the chain of custody of "the original" as far back as is feasible. It's getting hard to fool investigators here-and-now about these sorts of things; a sufficiently advanced interstellar civilization could have all sorts of additional investigative tools at its disposal.

This is simply accepting the premise that aliens have a preference for the oldest purported original over the most recent exact forgery, or alternatively have a preference for not being deceived and if promised the original want the original. If they don't care about acquiring the original, then maybe the forgery doesn't have to be that exact. "It's so exact that they should not care" is simply shifting the "that exact" line around a bit; physics doesn't quite let you abolish "provenance". Or, more finely, having promised to deliver "the original", if the seller ships "a perfect copy", has the seller committed fraud?

This is all hypothetical anyway; we have no evidence for aliens of any sort, let alone ones that want to acquire a human artifact for whatever reason. Imagining aliens sharing our own peculiar preferences with respect to art, but not granting that individual humans have different peculiar preferences, is the real problem in this thread. I don't think imagining yet more Star Trek technology is especially enlightening, but at least it's a little interesting.

Small nit:

> If you take one atom and replace it with another

This is a bit sloppy; for your argument you want to replace it with an identical atom -- no swapping of isotopes etc. -- and in an identical state with respect to its neighbours. Already historians do studies of Cs, Sr etc. isotope ratios at various depths, to study the mid 20th century history of various artifacts. They are already quite good at determining on which continent a painting was displayed or stored (or fabricated) at various times during 1945-1963.

Arguendo, the technology exists to make a "perfect copy" of an object like the Mona Lisa painting that is _locally_ indistinguishable in principle from the original. Arguendo, interstellar art forgery is profitable use of this technology. Arguendo, the knowledge of the technology and its utility in forging art is unknown to to the aliens, even though they know about the Mona Lisa and want it (that is, the one "universally" believed to have been painted by Leonardo da Vinci) rather than some traditional form of copy (that is not as perfect). That is, they care about provenance, but have not been offered (and have thus not rejected) a "perfect" copy in your sense.

The issue here is that provenance relates to the worldlines of the constituents of the macroscopic painting and whether they all converged around Leonardo da Vinci, for instance, rather than not converging around Leonardo da Vinci, but converging around the forgery machine. Since humans do not see macroscopic objects as worldtubes, human physicists are continually at risk of falling prey to a sort of slicing/threading chauvinism. In particular, the risk is that we assume that since electrons have spacetime-position independent (and covariant) characteristics, only those characteristics matter in a system involving multiple electrons. (cf. ideally we want to avoid considering large numbers of small contributions).

Boiling that down a bit, I think you're arguing in this thread that we should only consider some "present" values surface (e.g. one in which the aliens begin a test of all the traits of the Mona Lisa painting with those they have come to learn through research) and that everyone can and will ignore the surfaces on one timelike side of that.

Take the spacelike hypersurface on which the perfect copy and the original both exist but the copy only exists in one of the adjacent spacelike hypersurfaces. I think you are essentially arguing that the only choices of gauge on that surface all throw away (as "redundant degrees of freedom") the information necessary to reconstruct hypersurfaces on the "no copy exists" side, forming an information horizon.

(Geroch has a few things to say about this sort of argument in various papers, given the mild assumption of hyperbolization, and there is a wider literature on the initial values / Hamiltonian formulation of General Relativity. To be clear, I don't think you necessarily need recourse to O(h^n), n > 1 effects to poke holes in a formalization that imposes information loss; you get it only from the causal structure of a Lorentzian manifold with a tiny handful of mild additional constraints, all of which are well supported experimentally.)

Accepting for the sake of argument that a perfect copy in your sense can be made, I'd agree in an instant that we do not have the in practice ability to distinguish between copy and original if we threw both into a tumble dryer and ran the latter inside a thick-walled lead box for a couple of hours. I'd accept that nature with its Gauss-Laws provides similar (partial[1]) screening of "provenance", even. However, I'm not sure I'm convinced that a sufficiently advanced alien society could not see through these in principle, given enough effort; here we could add yet more Star Trek technology in the form of transporters, scanners, extremely long range telescopes ("enhance!"), FTL travel, etc.

Finally, if neither party can see through these in practice, the salient point is that at least one forgery exists, as does an effort by the seller of the "original" Mona Lisa to make it maximally difficult to tell that that forgery is a forgery. Caveat emptor.

- --

[1] Distinguishing between information conserving systems and Hawking's semiclassical information-destroying black holes.

> This is all hypothetical anyway

Really? And here I was thinking that the original paper was meant to be taken seriously. (Who is William Proxmire anyway?)

> for your argument you want to replace it with an identical atom -- no swapping of isotopes etc. -- and in an identical state with respect to its neighbours.

That's right, to the limits of what is measurable anyway.

> the knowledge of the technology and its utility in forging art is unknown to to the aliens

No, I'm assuming the aliens have this technology. So they have a choice: they can receive a scan of the original, from which they can construct an indistinguishable copy, for $X, or they can receive "the original" sent to them as a bundle of atoms for $Y, with Y>>X. There is no deception involved. My claim is simply that if the aliens have any sense at all they will choose the first option.

> My claim is simply that if the aliens have any sense at all they will choose the first option.

Does Homo economicus really exist? And even if it did, the ends optimized for are chosen subjectively, aren't they? If the aliens' goal is to possess the original fsvo original, that's their business. Just as it is the vendor's business to set the price of the original at $Y at a price of $X.

AFAICT you introduce "... as a bundle of atoms ..." here. Are you proposing that rather that to "actually ship" original or copy, rather than packaging up the original carefully to keep it intact on its journey, you ship a dust that the buyer can reassemble, IKEA-style ("Interstellar Kamprad")? (Even still, they may decide that destroying the original in this way is worth the price premium you're demanding above destroying the atomically-identical copy; who's to say?)

Finally, there is some circularity in you asking $X rather than $Y, Y >> X in this case -- if you don't see the difference yourself, why would you have priced them so differently, instead of charging either $X for both or $Y for both, and then randomly choosing to send the copy or the original at that price? For instance, "Because that is the price they are willing to pay? Because that is the price the market will bear?" involve some assumptions about your a priori market knowledge.

> Does Homo economicus really exist?

Not here. Not yet. But maybe somewhere.

But even here, no one pays a premium for "the original" of a digital image. Originals command a premium only in the absence of technology to make perfect copies.

> Who is William Proxmire anyway?

He has an interesting wikipedia page. I can't for the life of me figure out why his campaign paid Krugman for this paper. Perhaps he gave the campaign (and it's anti-space-exploration platform) something they weren't expecting, and they had paid in advance. :-) More likely it was Krugman making a joke. There are several others in the paper.

Krugman's paper is interesting in arguing whose clock should be used for the calculation of compound interest and makes the perfectly reasonable argument that if a common frame of reference between the planet-bound sender and receiver is avaialble, that should be used, otherwise the receiver's (and certainly not a relativistically moving transport vessel). There's really not that much physics in it, which he cheerfully admits.

He also argues that the interest rates of the trading parties would equalize with trade. Again, perfectly plausible (and, it turns out, in the intervening decades that has essentially happened on Earth). He does have a relativistic take on this, though, doing roughly a Lorentz transform on interest rates. Maybe it partially anticipated the investment into low-latency/high-frequency trading that has been popular recently?

Ah, I see you have completely missed the point here. William Proxmire was famous for handing out "golden fleece" awards to acadmics who, in his judgement, were wasting government money by doing useless research. That acknowledgement isn't real. It's a signal that the paper was meant to be a joke.

Unless they want to purchase the authority of the original.

It's about the story and the people behind the objects. You could create an exact atomic replica of the Mona Lisa, but it still wouldn't be THE Mona Lisa that Da Vinci sat in front of and painted with his own hands. From a purely material perspective they're the same, but from the perspective of historical narrative there's a big difference, and that matters to some people.

In other words, people aren't placing value in the arrangement of atoms, they're placing value in the context of how those atoms came to be arranged that way. The original object is a token of that context.

Yes, for the Mona Lisa, what's special is that Da Vinci painted it.

Quoting lisper (at the article on his website), 'All you have to do is to try to define what "the same thing" actually means.' (emphasis his).

He is trying to define it in a way that the people who he is interacting with here don't agree with.

It's a bit incongruous to point to an article that claims, "Arrangement is everything" (emphasis his), and then proceed to consider the arrangements of atoms in a painting without considering the arrangement of the painting with respect to other things, and especially not with respect to everything. At a chosen time coordinate, the painting and its replica (down to their subatomic constituents) occupy a non-overlapping range of coordinates in space. They are different because of the arrangement. Yet his argument is that they are the same because of arrangement (but only of the atomic components of each).

More importantly, at a time coordinate in which Leonardo da Vinci was alive and the original Mona Lisa painting existed, there was only one such painting -- any atomically perfect duplicate comes much later, and it's that arrangement in time that is important in your arguments, which I agree with.

More generally, otherwise-identical extended composite objects differ because the average of their components' worldtubes are essentially non-overlapping and diverge (or converge, depends on which way you want to think about timelike directions in this context) at different points in spacetime. In the case of our paintings the divergence happens at the tip of the paintbrush Leonardo da Vinci applied his completing stroke with, versus in the Star Trek style replicator.

The value of these paintings are position-dependent, and history-dependent. Position and history (combined they are the worldline, or worldtube for extended objects) are degrees of freedom that does not vanish by physics tricks, although it is easy to neglect them when their effects are small, and neglecting them makes calculations much simpler. But the effect of position and history on the paintings' value is not small, or at least I think it would not be small for most assessors of value (although lisper claims he would value them equally).

> More generally, otherwise-identical extended composite objects differ because the average of their components' worldtubes are essentially non-overlapping and diverge (or converge, depends on which way you want to think about timelike directions in this context) at different points in spacetime.

This is a great way to express the historical aspect in physics-speak. That is, the object isn't just a spacelike thing at some particular time. It's a spacetime thing. I can't quite imagine how one could duplicate that.

> This is a great way to express the historical aspect in physics-speak.

Well, it's 'worm theory' (Balashov's terminology[1]), which is one way of defining at objects in relativity (curvature is not necessary, so you can do this in Special Relativity too). It unfortunately still imposes all sorts of human chauvinism in terms of what an object is, and what a worldline (or worldtube, for "objects" that aren't strictly pointlike) is.

An alternative is to take fields (which take on some value at every point in spacetime) seriously, and declare that the universe-pervading fields on the background spacetime (curved or flat) are the only "objects". Then, if you find a characteristic pattern of field values that appears in a region of spacetime wherein its components obey some adjacency function, you can describe the pattern as a worm or as a 3d object evolving in time.

Let's consider a piece of flat 2d Lorentzian spacetime, with a single scalar field drawn as a 5x5 matrix:

  1 0 0 0 0
  0 1 0 0 0
  0 0 1 0 0
  0 0 0 1 0
  0 0 0 0 1 
Aha! A pattern! There's a characteristic value (the set of "1"s) that we want to treat as a 'worm', or worldline, of a single object represented as a "1" somewhere in space (at a given time). This means we have to slice our 2d spacetime into 1d spaces at different times.

Take the bottommost row as a spacelike 1-d hypersurface at some early time, then the next row up as a similar surface at a later time, and the next row up at an even later, and so forth. We won't lay down coordinates, and won't be precise about scale beyond "this is a small region of a larger spacetime".

Let's complicate the picture:

  1 0 0 0 1
  0 1 0 1 0
  0 0 2 0 0
  0 1 0 1 0
  1 0 0 0 1
What's this? Well, like before it's just a scalar field on a patch of 2-d flat spacetime, with a different set of values.

But what's "happened" here under our slicing? Is one "1" always going left and the other always going right, and they just pass through each other? Or, alternatively, do they bounce off one another, with the "1" on the left scattering leftwards at t=3 and moving rightwards at t=4? The "1"s are indistinguishable, so it could be either! We need an interaction rule for the field, deciding when "1"s pass through each other and when "1"s bounce off each other.

We could complicate this further, by adding more fields (and more complicated fields, and interactions among the fields) on the same spacetime. Indeed, we could add all the fields (and their mutual interactions) of The Standard Model of Particle Physics. This requires specifying a set of values for each of the fields at each point in spacetime, everywhere throughout the spacetime. And indeed, the Standard Model, on flat spacetime, allows one to do exactly that.

Our conversation's Mona Lisa is in this way of thinking "just" a recognizable characteristic pattern of a vast number of values across several fields in a region of spacetime. But "recognizable" here is critical: it's not the theory picking out an object; it's a user of the theory first spotting a pattern and then deciding how that pattern evolves or moves, by fixing a gauge[2]. In the 4-d fields on 4-d spacetime block universe, there is no motion or evolution. We only get that by making choices that let one talk about what's past and what's future, and what's separated spatially within a 3d space at some time t.

When one does not have at hand all the values for all the fields across the whole of spacetime, one wants to fill in the blanks using already-known values and adjacency rules. The typical human only has access to a small range of observables, so is missing a lot of detail locally as well as knowledge about what's further away on her or his left, right, front, back, above, below, future and past. Fundamental theoretical physics to some extent is about finding useful rules that let one accurately fill in missing detail near to a point in spacetime, and about predicting the detail further away from that point. It's also about things like accurately connecting a crystallized blockworld formalism with a deterministic Hamiltonian formalism for the same spacetime with the same field content.

> I can't quite imagine how one could duplicate that

Original Mona Lisa is qualitatively characterized by some set of values that that "hang together" across a region of spacetime. One has to say pattern adjacent to Leonardo's studio and pattern adjacent to Louvre wall are "close enough to be the same". That requires deciding that many values in the spacetime between those are "noise". Cosmic microwave background photons, solar and cosmic neutrinos, and so on, don't "hang together" with the core painting pattern across such a large region. Also, one has to coarse grain somewhat, since the values of quark and gluon and electron fields at positions within the pattern (relative to something we pick out as it's centre, say) are far from the same at small scales over large spacetime regions.

Likewise, Original Mona Lisa and Duplicate Mona Lisa can only ever be "close enough", or "identical within the limits of our ability to measure, and deliberately ignoring measurable differences in position, orientation, ...".

Indeed, even comparing Original Mona Lisa complete-and-with-Leonardo and Original Mona Lisa complete-and-being-appreciated at the Louvre by President Macron, the painting at the latter point in spacetime has outgassed, dropped off flakes or chips, had environmental pollutants adsorbed onto it, and so on, and thus is not atomically the same.

- --

[1] Balashov, Y. (2002), "On stages, worms and relativity", in Callender, ed., _Time, Reality and Experience_, Cambridge University Press, pp. 223–252

[2] in the relativity sense, https://terrytao.wordpress.com/2008/09/27/what-is-a-gauge/ cf. https://en.wikipedia.org/wiki/Coordinate_conditions?oldforma...

> You could create an exact atomic replica of the Mona Lisa, but it still wouldn't be THE Mona Lisa that Da Vinci sat in front of and painted with his own hands.

Actually, it would. That is the definition of "exact atomic replica".

Did you read the article I linked to?

Yes, it's an "exact atomic replica". But it's still a replica, and not the original.

And really, "did you read" gets boring quickly.

Well, if you had read it you would understand why there really is no difference between an original and an exact atomic replica. Just as it makes no sense to distinguish between two copies of Microsoft Word and call one "the original", it makes no sense to distinguish between two atomically identical objects. (Or at the very least you would know that there is an argument for this position, to which you might have actually been able to muster a counter-argument rather than simply proclaiming with no supporting evidence whatsoever that "it's still a replica and not the original." No, an exact atomic replica is not "just a replica". But I'm not going to recapitulate the entire argument here.)

Dude, of course I read it. I just disagree. And with you.

> ... muster a counter-argument rather than simply proclaiming with no supporting evidence whatsoever that "it's still a replica and not the original."

It's you who are missing the point. One can have supporting evidence about which is the original.

I mean, just consider the Mona Lisa. How do we know which of the many copies of that painting are the original? We arguably don't know that through any sort of measurement. Because Da Vinci and the early owners didn't have the technology to make necessary measurements. So what would we compare our results to? Maybe one could get at it through radiochemical dating, but even that's iffy.

Anyway, how we know which is the original is through the chain of custody. And that also applies to atomically exact copies.

> How do we know which of the many copies of that painting are the original? We arguably don't know that through any sort of measurement.

Of course we do. We can, for example, carbon-date the wood that the original is painted on. We can do chemical analysis of the pigments. There are a lot of ways to distinguish a real Rennaissance painting from a modern copy. But (and this is the main point) only because the technology we have for making copies of paintings is not yet perfected. If we could make an atomically perfect copy of the Mona Lisa, it would be absolutely indistinguishable from the original.

> If we could make an atomically perfect copy of the Mona Lisa, it would be absolutely indistinguishable from the original.


The painting is an off-axis bump on a slowly rotating roughly spherical planet; consequently it sheds gravitational radiation. The painting is effectively a rigid extended object, and thus the gravitational radiation has a corresponding characteristic mode depending on the painting's position and orientation. The mode propagates to infinity. Sure, it would take an ultra-super-hyper-advanced gravitational wave detector to pick it out at interstellar range, but it is possible in principle.

Before forgery: one Mona Lisa mode; after forgery: two Mona Lisa modes. The modes will differ because of different position and/or orientation on Earth. The position and orientation of the "original" has changed over time, pretty substantially; the latter's position and orientation is likely to change over time too. Anyone observing the relevant bits of Earth's gravitational radiation spectrum (over time, if you want to think of it that way) would be able to distinguish the two. Trouble if the buyers are already accomplished gravitational wave astronomers (we've just barely started) and keep detailed records.

I think it's easier to handwave an extremely tuned gravitational wave detector than an exact atomic duplicator or a device which determines that a pair of ~ 8kg paintings are atomically identical (especially one that does not render them atomically non-identical).

> I think it's easier to handwave an extremely tuned gravitational wave detector than an exact atomic duplicator

Well, lets look at the current state of the art with respect to each.

We can make non-destructive 3-D scans of objects, and we can image and manipulate individual atoms. We can fabricate 3-D structures with feature sizes a few atoms wide. That's not quite at the level of a 3-D atomic duplicator, but it seems to me to be well on the way. The machines that do these things are not yet household items, but they are not uncommon, and the technology is improving all the time.

By way of contrast, the state of the art in gravity wave detection lets us see nothing less energetic than the collision of two black holes, and there are two devices that can do this on the entire planet.

So a 3-D atomic duplicator seems much more plausible than a device that can track an 8kg object through a gravitational field at interstellar distances.

> We can make non-destructive 3-D scans of objects

Of their surfaces. What about the internal components?

The Mona Lisa is many things but it is not very thin or flat.

There are pigments and bindings involved that are sensitive to protein structure, as well; it's not just the count of atoms (and subatomic components; there are metals involved too, and isotope ratios are fingerprints), or even their relative position sensu stricto that matters.

I'm not sure how you could go about non-destructively determining (for example) potassium radioisotope differences in the original painting's layers between the optical surface and the canvas.

> state of the art in gravity wave detection ... black holes

We can detect gravitational waves of much closer much smaller systems just fine, and did so about 105 years before Poincaré proposed them formally. It was almost eighty years later that they were cast into the current perturbative formalism though.

The amplitude isn't really the critical factor with LIGO. It's sensitive to a particular frequency band (~ Hz - kHz) that is far from that of a small off-axis bump on a planet (~ microHz). It would totally pick up a set of deadlift weights spun around by a dental drill, if you could make that work in practice. (The amplitude difference between the sites would exclude it as an astronomical signal; the final inspiral of binary black holes and neutron stars have enormous amplitude, but that falls off linearly with distance, and they are very very far away, so the amplitude difference between sites is basically nil).

> track an 8kg object through a gravitational field

Given that one knows a number of things about the object including rough position and its surrounding environment (notably one wants to know its background metric exactly, or at least the exact model metric for Earth and some subleading-order non-Mona-Lisa contributions to perturbations thereof), it gets much easier. For a painting it's not something we could do today even if we had a spaceborne observatory sensitive to the relevant bits of Earth's GW spectrum, but it is plausible that we could observe the GWs shed by Olympus Mons with current technology, for example. (It'd be expensive to build).

We have good lunar masscon data so can watch the GWs shed by those as the moon relaxes into a more spherically symmetric shape; we have decent masscon data for Earth so can in principle with today's technology watch seismic events using gravitational wave Earth observation (as opposed to astronomy) (earthquakes make Earth rounder and spin faster, so the remaining masscons shed even more gravitational radiation).

> Of their surfaces. What about the internal components?


> We can detect gravitational waves of much closer much smaller systems just fine

So what? We're talking about interstellar commerce here.

> today's technology watch seismic events using gravitational wave Earth observation

Seismic events are many, many orders of magnitude more energetic than a painting being moved around.

Even if you had the technology, all it would take to foil it would be for the copy to move close to the original at any point in time.

(And I have to emphasize here that the point here is not that it would be easy to execute a deception. The point is that no sensible being could possibly care whether or not they have "the original" if they have to resort to such extreme measures to figure it out.)

> X-ray microtomagraphy

Neat! But, can it work in principle to pick out the structure and arrangement and composition of molecules? (I'd guess yes, but am not sure).

> We're talking about interstellar commerce here

Interstellar distances are ~ pc distances; the GWs we are looking for with LIGO are >> Mpc or << pc with GRAIL/GOCE/GRACE and their follow-ons. These observatories are sensitive to sources at radically different distances, but since such sources are not what's under study (and in particular it is hard to correlate their GW signals with other observables), their signals are excluded.

One could build a GW observatory to study an exoplanet in pretty fine detail (down to whatever the appropriate word for its seismology would be); there are a lot of unknowns about exoplanets, but their mass quadrupoles are determinable independently, and GW observatories essentially just look for changes in mass quadrupoles. What's responsible for any given change is the hard part, after one has built the (distributed) observatory.

GRAIL II would have done exactly that for the moon and (it was hoped) for a couple of other objects in the solar system. GRAIL itself was an approximation of this broad technique for the moon.

> Seismic events are many, many orders of magnitude more energetic than a painting being moved around

Sure, amplitude-wise. They have very distinct frequencies though. The argument you want to advance is that there are lots of similar objects (8kg rectangles, roughly) that generate a lot of noise, and worse, some of them are in the same art gallery (and with similar orientation) as the subject of observation. Worst of all, picking it out if it never leaves the Louvre wall is implausibly difficult; but if it's moved around the gallery, and in particular, it's back does not always face the gallery wall it normally hangs on, that opens a lot of "technology will improve" arguments, such as you use with the "perfect copier".

> all it would take to foil it would be for the copy to move close to the original at any point in time

The emissions from a bump on a rotating sphere is strongly determined by the bump's position. I happily admit that you can contrive ever-greater screening, though, but the cat would be out of the bag that you were deliberately trying to frustrate distinguishing between the original and the copy.

Which rather raises the question, why? Why not just hang the copy and ship the original to the aliens as agreed?

> no sensible being could possibly care ... if they have to resort to such extreme measures

I think you have the ordering wrong; they might resort to such extreme measures because they care. Their valuation function might not be identical to yours (why the Mona Lisa rather than any other Earth painting? or any painting they could make locally, in the style of an arbitrary Earthling?).

Or, more pointedly, maybe when 'all you have to do is to try to define what "the same thing" actually means', you, other people, and aliens' efforts might lead to different definitions.

> when 'all you have to do is to try to define what "the same thing" actually means', you, other people, and aliens' efforts might lead to different definitions.

Well, yeah, they might. But I'm assuming the aliens understand physics, in which case only one definition makes sense. You can snooker the irrational and the ignorant into paying for anything regardless of what species they are.

On which note, I have this nifty bridge you might be interested in? It's available at a great price. And it is the original!

Incidentally, we seem to be discussing the plot of _City of Death_, Douglas Adams's Doctor Who story. :D

First, we don't know exactly when the Mona Lisa was painted. From Wikipedia:

> ... It had been believed to have been painted between 1503 and 1506; however, Leonardo may have continued working on it as late as 1517. Recent academic work suggests that it would not have been started before 1513. It was acquired by King Francis I of France ...

So what we rely on here is custody records, all the way back to King Francis I. Also, why limit the discussion to modern copies? Again, from Wikipedia:

> A version of Mona Lisa known as Mujer de mano de Leonardo Abince ("Leonardo da Vinci's handy-woman") held in Madrid's Museo del Prado was for centuries considered to be a work by Leonardo. However, since its restoration in 2012 it is considered to have been executed by one of Leonardo's pupils in his studio at the same time as Mona Lisa was being painted.

Basically, it was a copy, painted at about the same time. Now imagine that King Francis I liked the Mona Lisa so much that he had one or more copies created. How would we know now which was the original? Only via records.

You're still missing the point. Your argument assumes current copying technology. I'm assuming perfect copying technology, so that the copy is identical to the original in every possible detail, as identical as one copy of a software application is to another. One Mona Lisa goes in to the duplicator, two come out. Each of the ones that come out are indistinguishable from the original.

There is a difference, it's not the original. And that's in an authority chain of custody human sense.

To ignore that would ignore the change of things over time in the meeting associated with them. Whoever has the original is the authority on the state of the original, the copies are copies derived from that Authority. They have context in meaning only because of that original.

Whoever owns that, owns the culture and the story behind the original. That is something one can purchase and it does have value even though there are no physical differences. The original will diverge from the copies if anything just because how it's capped and where it exists in the universe.

Say there was a pan galactic radiation blast of some kind. And the original. Slightly contaminated. That's part of its history now, the copies wouldn't have been similarly tainted. Just one example.

People value stories, and we work to maintain them in their continuity. That is what the original represents. It can be purchased it does have value. This is not a physical thing.

All that is true only because of the current limits of our ability to duplicate physical objects.

Would you pay a premium for "the original" of a digital image?

An original digital image isn't the same thing as an original physical object.

The difference lies in the state of the object. Over time, it will degrade, change, be impacted by it's environment.

A copy, can be thought of like both the photo and a physical object.

In the photo sense, a capture sufficient to exactly reproduce the object is no different from the photo. That's just data.

In the physical object sense, the moment a duplicate exists, it begins to diverge from the original, which makes the original an authority. Future copies will differ from prior ones.

Only because we have the technology to make perfect copies of digital images, but not perfect copies of physical objects. If we had that technology -- and there is nothing in the laws of physics that prevents it -- they would be exactly the same. That's the whole point.

They would only be exactly the same at a precise moment in time, and given the source data is timely.

From there, they would diverge.

Three things happen:

One, the data capture representing the object gets dated, and would represent the original at some point in time, not as it is today.

Two, the copy objects would also diverge from both the data and the original.

Finally, the stories related to the objects differ.

The original remains the authority on that particular object. For many things, nobody would care, and I agree with you on all of that.

However, you very seriously under estimate the value history and culture have. And you also are ignoring how a story becomes intertwined with a given object.

As an extreme example, one could say there was some war, and one of the copies of a famous painting was damaged in the war, but owned by someone who won that war at great personal cost.

Now, we've got the original, with historical value, and one copy in particular with value, both above and beyond that value any other copy may have.

For those interested in, perhaps involved in, that war, the relevance of that specific copy, with the damage marks on it, where it's at, who owns it, all differentiate that copy from all other objects.

Things that are exactly the same do not remain the same.

And where that is true, originals will have value above and beyond copies.

I understand your argument. But you are underestimating the impact that my hypothetical atomic copy technology would have.

Consider this scenario: instead of scanning the object, sending the information to some remote location, and recreating the copy at the remote location, the copier works like this: you put an object in, and after some time two objects come out, each atomically identical to the original. Now you really can't tell which is which.

In the case of remote-copy you can tell the difference. But would an alien race really care enough to be willing to pay a lot more for "the original"?

There's actually a similar situation going on right now in the diamond market. DeBeers has spent a lot of money trying to convince people that natural diamonds are somehow better than artificial ones despite the fact that they are absolutely indistinguishable from one another (and so DeBeers is putting a lot of money into developing technology that can mark "authentic" diamonds). IMHO this is a pretty transparent scam, and people fall for it largely out of stupidity or ignorance of chemistry. I believe (or maybe "hope" is a better word here) that any society that can travel to the stars will have moved beyond such foolishness.

History is not foolishness.

I believe the impact will be profound, and in the majority of cases, will play out like you say.

There are some where it won't.

It means that it has history attached to it and that it's traveled in time. Humans will most certainly not abandon things of affectional value our lives and most value in life is built up around that.

Why do you think you have different levels of friends? History is very important to us.

You clearly did not read the article I linked to.

I did, why don't you think I read it?

Because the article contains within it the refutation of your argument. In fact, that's the whole point of the article.

"... the universe has played a trick on you by supplying you with a continual stream of overwhelming evidence that the universe is populated by material objects that exist in particular places at particular times, and that have a continuity of identity such that it makes sense to say things like, "The vase on that table exists." The reason that continuity of identity matters is that it's required to make sense of the phrase, "The vase on that table." For that phrase to make sense, the vase that is on the table now has to be the same vase that is there a microsecond from now. If this were not so, then the vase on the table at time T0 might have existed at T0, but at time T0+epsilon it no longer exists. Instead, it's a different vase that exists at T0+epsilon (and a different one yet again at time T0+2epsilon)."

"This probably sounds like I'm being pedantic, because it's just obvious that material objects like vases do have continuity of identity. The evidence for it is just overwhelming. But despite the overwhelming evidence, it is in fact not true..."

May I suggest that you didn't read my comment then? That's not what I was answering.

That's what it sounded like to me:

"It means that it has history attached to it and that it's traveled in time"

For this statement to be true, or even meaningful, there has to be a meaningful referent for "it", and that referent has to have continuity of identity if the word "history" is to be meaningful. In this case "it" is a painting, which is a physical object. But physical objects do NOT have continuity of identity.

Put this another way: consider the following two scenarios:

1. Take every atom in the Mona Lisa and replace it with a different atom of the same element and isotope in the same physical location.

2. Take the Mona Lisa and grind it up into sawdust.

I think you will agree that the end result of #1 can me more reasonably regarded as "still the Mona Lisa" than #2. And yet #1 is "different atoms, same arrangement" while 2 is "same atoms, different arrangement." So it's not the atoms that matter, it's the arrangement.

That it has history attached to it is what makes it valuable. Thats why an original is worth more than a copy. It's the one thing you can't replace the "it's" history.

A vase owned by Djengis Kahn is worth more than the same type of vase owned by some no-name.

In other words it's not the atoms or the arrangement that matter but the history of the object. It's not the inherent value of the object but the value of the history of the object we assign to it.

You are not hearing what I am saying. "The history of an object" is a concept that ceases to make sense in the presence of atomic-level replication, just as (for example) "simultaneous events" ceases to make sense in the presence of high velocities.

I am hearing what you are saying its just not true. Its me knowing what the original is thats valuable, the second you replicate it you diminshes the value to me.

I.e. the one shipped from earth is more valuable than the one replicated no matter the level of fidelity because I know the difference.

How could you be sure the one shipped from earth was not replicated on earth?

You can't but that doesn't change much because it's still from earth which makes it more valuable than if it's been made in front of me. Of course you can get scammed you can do that today too. But that has nothing to do with how value is created.

Again it's not the object that is valuable it's you deciding it's valuable. Living in a world like that we would find other ways to ensure that we track the authenticity to the extent we can. So value will always be ensured because it's created in the brain not in the object.

> > How could you be sure the one shipped from earth was not replicated on earth?

> You can't but that doesn't change much because it's still from earth

How do you know that? You just conceded that there's no way to know if the thing was replicated before being loaded onto the cargo ship. How do you know that it wasn't replicated on the cargo ship shortly before arrival?

> Living in a world like that we would find other ways to ensure that we track the authenticity

No, you wouldn't. That's the whole point. In a world with replication technology, the whole concept of "authenticity" becomes every bit as meaningless for physical objects as it already is for digital ones.

> So value will always be ensured because it's created in the brain not in the object.

This is essentially saying that you will always be able to find suckers. Which may be true, but I would hope that any member of a space-faring species would have a basic understanding of physics, cognitive bias, and logical fallacies.

You are still too focused on the object. A Ming vase has no inherent value, we apply value to it.

I am saying that there will be fraud but also plenty of normal decent people who do not cheat, just like today.

I could hire someone to make sure there was no replicator on the ship just as an example. There could be procedures in place on earth to make sure its still the original.

You are completely disregarding the human part which is why you end up with the conclusion you do.

No, I get that humans can attach value to things for irrational reasons. But you don't seem to grasp the impact that replication technology would have. Look at the diamond market, which is collapsing because of the advent of artificial diamonds. DeBeers tried to rescue it by promulgating the myth that natural diamonds are somehow superior to artificial ones, but this failed because they are indistinguishable. The exact same thing will happen to art when replicas can be made that are indistinguishable from the originals.

The only reason humans care about old things is that at the moment they are still hard to replicate, and that makes them scarce. As soon as it's easy to make something that is equivalent to an old thing in every measurable way they will no longer be scarce and their value will plummet just like everything else that can be mass-produced.

I do grasp the impact. You are assuming that there would be built no legitimate business which would not make it their thing to send original objects to earth.

The diamond market was created to begin with, just because the market is going down doesn't mean that the value of a diamond is which any visit to a diamond store would tell you and certain historic diamonds certainly haven't gone down in price.

You can't recreate the history of an original ming dynasty vase just because you can replicate it down to it's atomic structure that's the point.

You can't see this because you keep thinking about the object as having value. It never had value it's us who attach value to things and we will continue to do that even if we can replicate, in fact that would just increase the price even more for originals.

> I do grasp the impact.

I don't think so.

> You are assuming that there would be built no legitimate business which would not make it their thing to send original objects to earth.

No, I'm not assuming that. I'm presenting an argument for that. Not the same thing.

The argument is: in the presence of perfect replication technology, it is no longer possible to track the provenance of objects (and it is certainly not possible across interstellar times and distances).

If you think it's possible, tell me how you would do it. Suppose I own an original and you want to buy it. How can I convince you that what I am handing over to you is in fact "the original" and not a perfect copy?

I gave you several ways it could be done, but as long as you are so fixated on the object you can't see it.

Humans apply value. Today the Mona Lisa has no value inherent you can say that someone who pays 400milion for a painting is being scammed even if it's original.

But even if you can replicate the atomic structure the human perception of the value of the original does not go away and that means there is a market for that.

Claiming that it's not possible to send something created from earth which itself would be valuable even if it was something which was replicated on earth without being scammed is simply misrepresenting humans and that's the important part here humans, not the object.

> I gave you several ways it could be done

Sorry, you'll have to refresh my memory.

> If you can produce an atom-by-atom duplicate, what does it even mean for something to be "the original"?

Extracting from my longer reply, "the original"'s constituents' worldtubes diverge around Leonardo da Vinci. The atom-by-atom duplicate's atoms' worldtubes mostly do not -- they diverge around the forger(s) in their workshop instead.

A lot of the value of antiques comes from the lost knowledge they represent, whether that's just sentimental "you just had to be there" experiences or more concrete "you don't know how to make the varnish on a Stradivarius" lost knowledge.

For that matter, the distances between systems creates a sort of time-travel effect. You receive their knowledge hundreds of years after the fact, making it implicitly "antique lost knowledge."

So I think the point still stands that all trade would be done using photons.

I would be very interested to discuss how "trade done using photons" is such a 21st-century concept and that it bears as much resemblance to interstellar trade as the black pepper trade of the 13th-century proscribes capital markets today.

Vaguely on topic - the novel A Deepness in the Sky by Vernor Vinge touches on this subject a fair bit.

potential spoilers follow

Essentially, no spacefaring civilization is stable over long time scales, a culture (the Qeng Ho) get by through predicting which planetary system will have the economy to support refueling an interstellar craft (in the centuries-later future when they arrive). Trade advanced/secret technology development info for said refueling. The story has way more to it, but I loved it as a known-physics-following scifi story. I expect the audience of this site would also love it (and probably, many have already read it)

Love this book. The prologue is one of my favourite beginnings to a book and hints at how epic/vast the book's universe is:

> The manhunt extended across more than one hundred light-years and eight centuries. It had always been a secret search, unacknowledged even among some of the participants. In the early years, it had simply been encrypted queries hidden in radio broadcasts. Decades and centuries passed. There were clues, interviews with The Man's fellow-travelers, pointers in a half-dozen contradictory directions: The Man was alone now and heading still farther away; The Man had died before the search ever began; The Man had a war fleet and was coming back upon them. With time, there was some consistency to the most credible stories. The evidence was solid enough that certain ships changed schedules and burned decades of time to look for more clues. Fortunes were lost because of the detours and delays, but the losses were to a few of the largest trading Families, and went unacknowledged. They were rich enough, and this search was important enough that it scarcely mattered. For the search had narrowed: the man was traveling alone, a vague blur of multiple identities, a chain of one-shot jobs on minor trading vessels, but always moving back and back into this end of Human Space. The hunt narrowed from a hundred light-years, to fifty, to twenty - and a half-dozen star systems. And finally, the manhunt came down to a single world at the coreward end of Human Space.

I am going to read that book.

Thanks for posting that excerpt. It is a near perfect, "and then ehat happened?" Hook!

Software archeology! I adored that book. Highly recommended to anyone on HN that hasn’t read it, it’s well worth it. Quite enjoyable too, outside the neat hard sci-fi and cute extrapolations of modern day software engineering.

Loose prequel to my favourite book of all time A Fire Upon the Deep. Vinge is a brilliant author with a background in maths and computing and it shows in his writing.

Thanks for the recommendation, I just got it on Audible and I'm looking forward to listening to it.

One of Larry Niven's 'Draco Tavern' short stories has the economics of interstellar traveling sales-aliens as its plot device. I don't recall the name.

>A solution is derived from economic theory, and two useless but true theorems are proved.

>This paper represents one small step for an economist in the direction of the theory of interstellar trade.

>These complications make the theory of interstellar trade appear at first quite alien to our usual trade models; presumably it seems equally human to alien trade theorists.

This is wonderful and hilarious and full of cheeky fun (so so much more than I've quoted). It's perfect for the sigbovik crowd. Thanks for posting!

>This paper, then, is a serious analysis of a ridiculous subject...

Interstellar travel will consist of information travelling at the speed of light. Pretty much nothing else is practical.

The real problem is bootstrapping it. Because weight is so incredibly expensive to send interstellar, the only thing that could work is sending a nanorobot with an ability to self-replicate and build a receiver and a factory once it arrives.

Then information is sent to the factory, which proceeds to bootstrap a civilization.

> Interstellar travel will consist of information travelling at the speed of light. Pretty much nothing else is practical.

What's your reasoning for this? You would only have to accelerate at 1g for 3 years to hit 99.5% of the speed of light. You can use an electromagnetic shield for dust. It seems conceivable that this will be possible eventually, even if warp drives are not possible.

Forgiving the problem of time dilation and the consequences it has on the expectations of conscious things...

You can't just accelerate 1g for 3 years. What are you burning? A chemical rocket can easily achieve 1g. For about 5 minutes. A nuclear rocket is great, you can get 1g easy enough, but you're shoving hot hydrogen out the back end to get that thrust.

The Rocket Equation teaches us that to get arbitrarily close to c, you need an exponential amount of your ship's mass to be propellant.

I recommend this website to everyone in this thread that hasn't read it yet


Edit: moreover, the problem of an EM deflector, or any kind of deflector, is that no matter what, no matter what, you must deal with the kinetic energy of the thing that just hit your deflector. It will (a) slow your ship down, and (b) cost you more energy, e.g. from your generator, to deflect it than it imparted on your vehicle. The energy numbers here are staggering. We have trouble theorizing how a relatively uncontrolled terawatt rocket might work, but imagine a terawatt reactor on your ship somehow powering a terawatt EMfield in front on your ship.

And then you have to worry about dust that's not charged and thus goes right through EM fields.

Indeed, and the benefit of traveling at 0.995 c is that a container of information doesn't suffer from degradation by the inverse square law as it travels over a large distance. It might actually cost less energy to transport information to far flung destinations that way, interstellar snail mail if you will. Some amount of information has to accompany the robot anyway, at the very least, its initial operating instructions.

Of course whoever can get there at 0.996 c can take advantage of a market arbitrage. ;-)

> a container of information doesn't suffer from degradation by the inverse square law

Neither does a well-focused laser?

EDIT: apparently it does, unless you manage to focus your laser very far away. Not sure how practical that is.

1kg matter at 0.1c has a kinetic energy of 4.5x10^14 J

It is certainly very expensive to spend this amount of energy. But is it also extremely challenging to even extract this out of an engine that has to accelerate itself.

1kg matter at 0.995c has a kinetic energy of 8x10^17 J

This is the amount of enery you get if you convert 9kg in pure enery. That seems impossible to reach, even with an anti matter drive.

A 9:1 ratio of fuel to mass doesn't sound particularly bad. Are there known theoretical limits to extracting the full E=mc^2 worth of energy from an object?

No, you can do this with an antimatter rocket.

Good luck capturing and containing antimatter and feeding/containing the explosion though. It's going to be practically impossible to get a 90% fuel ratio from an antimatter reactor, since literally 45% of your ship will be antimatter, by mass.

You can also do this by feeding a black hole with ordinary matter and using Hawking radiation for propulsion. That is probably more practical than carrying around large quantities of antimatter.


If you watch PBS Spacetime on the 'Kugelblitz' idea, it seems that one way to go about it (over the course of a couple hundred years) would be to convert Mercury into a solar energy collecting swarm by use of Von Neumann probes and essentially harvest much of what the sun has to give. That kind of energy apparently would suffice to create tiny black holes (simply by redirecting enough energy to a focused point), which is I think the theoretically most efficient battery (or star system destroying bomb, depending on how you go about it...).

I... can't.... Half of me recoils in horror at the impracticality, but the other half of me has a good enough armchair sense for the practicality of a high fuel ratio antimatter rocket, so I can't say you're wrong :P

You need to accelerate the fuel as well. And for a reaction engine, you need to carry reaction mass that you accelerate. And at some point you want to decelerate again.

Would be interesting to see whether this is at least theoretically feasible.

How would the economics change if we could only communicate at light speed, but had a functional Alcubierre drive (or other lightspeed technology) and could travel at FTL speeds?

Presumably you would just load up the your Alcubierre station wagon with a bunch of backup tapes and send it down the interstellar highway. You could restore your backups before the original data is written!

> you would just load up the your Alcubierre station wagon with a bunch of backup tapes

Tapes have mass. Unless we learn to suppress inertia, it would be easier to encase the message photons in an Alcubièrre field.

Not suppressing inertia is indeed a problem, unless the message the kind you intend to be understood primarily by virtue of its infinitely inverse ratio of complexity to fidelity.

The secret to time travel is to drive backwards.

The secret to time travel is to forget that you're moving forwards with time, so you'll float instead. Many people have paid other people to surprise them into forgetting that they're moving forwards in time, so they'll float instead.

Do you consider FTL plausible? If so, why?

[warning: serious layman imagination ahead]

FTL === back in time, and maybe we don’t observe it since it doesn’t happen often. Like in iPhones that don’t spontaneously in cosmos every 2^30 years. Another cue is QM entanglement that somehow resolves the inconsistencies by out-of-timeline ‘decisions’ of what ‘really’ happened once you checked the outcome. If nature works in mysterious ways, why couldn’t it resolve the fact of time travel by the same logic: yeah, an object appeared from nowhere, but it disappeared from somewhere, no brainer. Our puzzle is to create serious enough paradox for the nature for it to resolve it in a desired way. First experiments may resemble our first ‘friendship’ with the energy of atom, but then who knows.

Nature isn't commonly held to work in mysterious ways; it's generally held that nature is knowable.

Being able to travel faster than light, or send messages faster than light, would not involve objects popping in and out of existence. That's not even a particularly well-formed concept. You and everything else you know are already moving through time and space, and the rules for how that happens also suggest that if you bend the geometry of the universe sufficiently, you can move to a place in less time than it would take for light to cross it. If you then return, you can end up arriving at your origin before you left it. Relativity does not allow the universe to spontaneously warp itself into the kind of pretzel which would allow for things to travel instantaneously back in time, and if it did, the effects on anything else nearby would likely be catastrophic beyond ready imagination.

Much of your speculation is rooted in misunderstanding. It's more difficult to explain things because your conceptions don't map well to the actual physics. There's a series on YouTube by PBS called Space Time, which I would strongly recommend as an accessible guide to relativity and physics in general.

I know it, that’s in disclaimer!

Unfortunately so to my imagination. But I still hope that there is many orders of magnitude more quirks that could obsolete current well-proven models and open the world of possibilities. Honestly, modern physics restrictions are boring to death.

There's an austere beauty to the laws, but physics restrictions do take all the fun out of speculation, it's true. And it does place the stars out of reach of the individual, at least until we cure aging. Empirical truth has a heavy price.

Makes sense to me.

And even better, if you can exploit something at the destination to build your stuff. As in Carl Sagan's Contact and Peter Watts' Echopraxia.

I've read this before but this is the first time I noticed that Krugman wrote the paper in 1978 and the references include a paper about faster-than-light travel written by him, published 1987.

I read the Wikipedia article on this paper today and turns out Krugman wrote this when he was feeling quite low being embroiled in the rat race.

From the point of political economics, charging interest is not necessarily a given. Economies exist where interest is prohibited.

In name perhaps, but the concept of an economic good having potentially different values at different times is universal. An economic system that tries to pretend it doesn't exist may work in the sense that a mathematical system without a 0 works. We can still analyze the system using the concept and develop insights using it as a tool, even if they don't recognize it themselves.

> The ship's velocity can then be represented by a rotation of the axes; the rotation of the time axis is shown in Figure II. (Readers who find Figure II puzzling should recall that a diagram of an imaginary axis must, of course, itself be imaginary).

So riddle me this -- how did Adam Smith's work (published in 1776) influence the initial settlement of Virginia (1607) and Massachusetts (1620)?

I'm guessing Krugman hadn't actually read Wealth of Nations, since anyone who had couldn't possibly have made this mistake. That's pretty shocking.

Given the whole thing is tongue and cheek, one could read "Could this be as influential as Adam Smith's work on the initial settlement of Massachusetts and Virginia" be a tongue-in-cheek acknowledgement that this work is effectively pointless.

...you know, like the whole rest of the paper.

I'm guessing you parsed it wrong.

"Could this be as influential as Adam Smith's work on the initial settlement of Massachusetts and Virginia" refers to Adam Smith's work on the initial settlement of Massachusetts and Virginia, not to purported Adam Smith's work influence on the initial settlement of Massachusetts and Virginia.

Right, "on" here means "about". English can be annoying.

So what is that influential work written by Adam Smith and concerning the settlements in Virginia and Massachusetts?

The Wealth of Nations. He looked at what Spain, England, etc got out discovery and colonizing America.

That’s a very oblique way of referring to the Wealth of Nations. There are only 4 references to Massachusetts in a 750-page book.

OK, "peripherally about".

You’re suggesting that the winner of a Nobel Prize for Economics hasn’t read Adam Smith?

I’m guessing you’re wrong.

I doubt it. What fraction of Nobel Prize winning biologists do you believe have read Darwin?

Is that an apples to apples comparison? I also don't expect Nobel physicists to have read Principia Mathematica.

Ansibles allow violating causality

I was waiting for him to go there -- if he had, I'd have been sure it was a joke.

He's not that knowledgeable. I mean he claims to be a liberal yet advocates for impoverishing the laboring classes by giving them backdoor paycuts:


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