Deep Time: Targeting Another Galaxy

by Paul Gilster on June 24, 2014

Interstellar flight isn’t about possibility as much as it is about time. We know we can launch a payload to another star if we’re willing to burn up enough millennia — about seventy — to get there in the form of a Voyager-style flyby. That’s with today’s technology, and we can extrapolate how the time frame can be shortened with improved materials and propulsion techniques. So as Robert Forward always pointed out, it’s not that interstellar flight is impossible — it’s that it’s very difficult, and our expectations of the kinds of missions possible have to adapt to that fact.

Intergalactic flight, though, is such an immense undertaking that I’ve rarely discussed it in these pages. Is there any conceivable technology that might make such a thing possible? Well, Carl Sagan and Iosif S. Shklovskii considered the situation in Intelligent Life in the Universe (Holden-Day, 1966), working with the opportunity for time dilation opened up by special relativity. Accelerate at 1 g continuously and time dilation helps you to reach nearby stars in just a few years as time is measured aboard your spacecraft.

The numbers get more and more mind-boggling as you continue to work the equations. With that same 1 g acceleration (and just how you achieve that is of course the grand question), you can make it all the way to the center of the Milky Way in about 21 years — tens of thousands of years would have passed on Earth by the time you arrived at the galactic core. Or go for the ultimate journey: A voyage to the Andromeda galaxy. To reach M31 in a ship of this sort would take 28 years ship-time as you nudged ever closer, but never reached, the speed of light. As always, I point to Poul Anderson’s Tau Zero as the novelistic embodiment of Sagan and Shklovskii’s musings, as fresh today as when it ran in Galaxy in 1967.


Image: M31, the closest major galaxy to our own. Continuous acceleration at 1 g would allow a human crew to reach it, but what conceivable technology would allow such a craft to be built? Image credit & copyright: Lorenzo Comolli.

Yesterday Adam Crowl mentioned Martyn Fogg’s paper “The Feasibility of Intergalactic Colonisation and Its Relevance to SETI,” in the context of Robin Spivey’s ideas on galactic migration. Fogg runs through the possibilities for intergalactic journeys including constant 1 g acceleration of the kind Sagan and Shklovskii talk about. Robert Bussard had proposed in 1960 that this kind of acceleration could be achieved through a fusion-powered ramjet design that fed off the interstellar medium. It would be a tough engine to light but once you got the ship moving fast enough, a self-sustaining reaction seemed to be possible, and it’s more or less the concept that Anderson used in Tau Zero for his starship.

But Fogg nails the problem with the Bussard ramjet, or I should say, the problems, there being several intractable issues to be faced. Robert Zubrin and Dana Andrews have shown that as the ramjet accelerates, the vast electromagnetic ‘scoop’ being used to collect fusion fuel actually begins to act as a brake. See Starships: The Problem of Arrival for more. And as early as 1972, A. R. Martin had discussed structural limitations that would prevent such a ship from sustaining accelerations this close to the speed of light.

Surmount even these difficulties and you run into perhaps the biggest showstopper. Gas density between the galaxies is, in Fogg’s estimate, 10-5 lower than what the ramjet would encounter within a galaxy. Gaining enough fuel, then, would be the challenge, and as we’ve learned more about the interstellar medium, it seems clear that a ramjet would have problems even within the Milky Way depending on the local density of interstellar material. That leaves only David Froning’s suggestion of a ‘quantum ramjet’ using quantum fluctuations of the vacuum, an idea that would assumedly not be constrained by the Bussard ramjet’s fuel problems.

Is there any other way to save the idea of intergalactic travel close to c? Fogg doesn’t think so. From his paper:

…irrespective of the propulsion system used, hyper-relativistic intergalactic travel would be fundamentally limited. The velocity of the ship at midpoint would be so close to c that no interaction with intergalactic matter would be permitted. Dust grains would impact like cannon shells and hydrogen atoms would take on the characteristics of a lethal and penetrating form of cosmic radiation.Thus, leaving aside the feasibility of a “quantum drive”, the use of time dilation to significantly reduce elapsed intergalactic voyage times would not be practical unless a way could be found of preventing impacts from oncoming particles.

That’s a pretty good list of seemingly insurmountable problems, all generated by the fact that we’re trying to get the crew that set out from Earth all the way to its destination. Give up on that constraint and a number of other possibilities open up that make us weigh interstellar and intergalactic flight against our concepts of deep time and the lifetime of civilizations. Sagan and Shklovskii didn’t pin their entire argument on Bussard-style craft. They also explored the potential of human hibernation on journeys lasting thousands of years. But there are other possibilities, some of them discussed by Adam Crowl yesterday, that I want to explore tomorrow.

The Fogg paper is “The Feasibility of Intergalactic Colonisation and its Relevance to SETI,” Journal of the British Interplanetary Society Vol. 41 (1988), pp. 491-496 (available online). Robert Bussard’s ramjet paper is “Galactic Matter and Interstellar Spaceflight,” Astronautica Acta 6 (1960), pp. 179-194. Andrews and Zubrin’s paper on the Bussard ramjet and drag is “Magnetic Sails and Interstellar Travel,” International Astronautical Federation Paper IAF-88-5533 (Bangalore, India, October 1988), although I’ll also point you to Zubrin’s Entering Space: Creating a Spacefaring Civilization (New York: Tarcher/Putnam, 1999). The Froning paper is “Propulsion requirements for a quantum interstelllar ramjet,”JBIS, 33, 265-270(1980).



A View of the Deepest Future

by Paul Gilster on June 23, 2014

Adam Crowl first appeared in Centauri Dreams not long after I opened the site to comments about nine years ago. His insights immediately caught my eye and challenged my thinking. I have always admired auto-didacts, and Adam is an outstanding example: “I don’t work in this field nor did I especially train in it,” he writes. “I did physics/maths/engineering study but my astrophysics, astrodynamics, planetology and interstellar propulsion knowledge is self-taught.” The list of books in the various disciplines — as well as science fiction — by which he did this will, I hope, become a future Centauri Dreams article. Adam writes the Crowlspace blog, is active in Project Icarus, the re-design of the 1970’s Project Daedalus fusion starship now in progress at Icarus Interstellar, and is a frequent participant on this site, often pointing me to papers I would otherwise have missed. The one he discusses today is, typically for Adam, a true mind-bender.

by Adam Crowl


The long-term fate of Life in this Universe is rarely contemplated. A few landmark studies, by Freeman Dyson, then Fred Adams, Peter Bodenheimer & Greg Laughlin, have looked into Deepest Time, long after Matter itself fails and the Void becomes unstable. How far can biological Life extend into the Long Dark? A study by Robin Spivey extends Life’s tenure, in neutrino-annihilation warmed Ocean Planets, to 1025 years – and Beyond. That’s 100 times longer than the 1023 years we’ve reported here previously and some 1,000 trillion times longer than the time the Universe has presently existed. If the current Age of the Universe was a clock tick – a second -, then those 1025 years would be 20 million years.

Spivey discusses his new finding here: Planetary Heating by Neutrinos: Long-Term Habitats for Aquatic Life if Dark Energy Decays Favourably [Open Access article]. Outer-shell electrons of 56Fe (iron) inside the cores of Ocean-Planets become ‘catalyzers’ of Inverse Photo-Neutrino Process (IPP) reactions, annihilating neutrinos and creating a steady heat-flow sufficient to warm the planet at ~0.1 W/m2. This Figure, published in the paper, illustrates the flow:


Perhaps coincidentally, the inexorable processing of stellar materials in Type Ia Supernovae leads to a chemical mixture which makes Earth-like planets. Each Type Ia Supernova masses about 1.4 Solar Masses, or about half a million Earths, with the ejecta debris being mostly iron, then oxygen and silicon. Earth-stuff. Thus the ‘ashes’ of stars can produce a multitude of Ocean Planets.

To quote Spivey:

Observations have determined that the ejecta of a typical SNIa are, by mass, 18% oxygen, 15% silicon, 13% iron, and 49% nickel (almost all in the unstable form 56Ni which decays radioactively to 56Fe), along with smaller amounts of carbon, calcium, sulphur and magnesium. Elements emerge from SNIa in strata, with the lightest occupying the outermost layers. This provides the oxygen-rich outermost shell with the best opportunities for reacting with hydrogen in the interstellar medium, resulting in the formation of water molecules. On cooling to temperatures found in deep space, ice XI is obtained, whose ferroelectric self-aggregation may be relevant to comet formation [38-40]. The bombardment of protoplanets with comets would be important to the formation of oceanic planets, deferring the delivery of water to their surfaces.

Notice that the iron component is 62% by mass, thus the very large core in the illustration. Quoting Spivey again:

Based on the composition of type Ia supernova ejecta, a hypothetical oceanic planet of one Earth-mass is projected to consist of a large iron core of radius ~4240 km surrounded by a silicate mantle of thickness ~1300 km through which heat would be transported by advection. External to this inner mantle would be an outer mantle of ice consisting of strongly convective ice VI and VII phases of combined depth ~320 km. A liquid ocean ~50 km in depth covered by a solid crust of ice Ih upwards of 50 m in thickness would overlie the hot ice mantles.

Spivey’s new paper focuses on how the supply of neutrinos can be maintained at the right density to keep planets warm for the maximum amount of time. He posits several, as yet, unobserved processes – the decay of dark energy into neutrinos in less than ~70 billion years and the accelerated decay of black holes, also preferably into neutrinos. Other researchers have posited the existence of ‘sterile’ neutrinos, which Spivey shows improves the characteristics of the neutrino halo surrounding a Galaxy cluster, enabling planets to be warmed in a life-friendly manner in a sphere of 400 thousand light-years radius.

The existence of Dark Matter itself has been called into question by physicists, such as Mordechai Milgrom, who think the evidence for invisible Dark Matter can be equally well explained by modifying Newtonian Gravity to have a minimum gravitational acceleration. This Modification of Newtonian Dynamics (MOND) theory neatly explains the structure of galaxies, but hasn’t been as successful on a cosmological scale. Intriguingly if Galactic haloes are made of sterile neutrinos, then MOND and Dark Matter physics are equivalent in outcomes: Reconciliation of MOND and Dark Matter theory with giant ‘Neutrino Stars’ forming around each large Galaxy. Spivey suggests that a key research priority is determining the properties of neutrinos, to confirm the IPP heating mechanism. Such neutrino studies are important for refining the Standard Model of particle physics – and possibly discovering new physics, such as the masses of the various neutrinos, something not predicted by the Standard Model.

Spivey’s most audacious suggestion is the strategy that Life should adopt in the next few aeons to extend its lifespan. Unfortunately for Life in this Galaxy, our local Group of Galaxies is insufficiently massive to form a large enough neutrino ‘star’ before Dark Energy spreads galaxies too far apart. To survive, Life in our Local Group needs to emigrate to the Virgo Super-Cluster. Although our Milky Way is heading towards Virgo at ~200 km/s, cosmic acceleration, from Dark Energy, is presently pushing us away from Virgo at ~1,000 km/s. Thus we need to launch towards Virgo faster than the Dark Energy pushing us away. Yet the reward is 10 trillion trillion years of Habitable planetary environments, which may well be worth intergalactic migration.

Spivey suggests using antimatter rockets to launch modest payloads. Essentially small Life-seeds, like those proposed by Michael Mautner to seed Life in our own Galaxy, but launched on intergalactic journeys of a hundred or more billennia. Whether the cosmic-ray flux between the Galaxies can be endured for geological epochs is presently unknown and while I wouldn’t rule it out, it seems unlikely at best. A good reference, available online, is still Martyn Fogg’s “The Feasibility of Intergalactic Colonisation and its Relevance to SETI”, which suggests how a mere 5 million year intergalactic voyage might be survived by a bio-nanotech seed-ship.

But we’ve discussed other options in these pages previously. In theory a tight white-dwarf/planet pair can be flung out of the Galactic Core at ~0.05c, which would mean a 2 billion year journey across every 100 million light-years. A white-dwarf habitable zone is good for 8 billion years or so, enough to cross ~400 million light-years. It’d be a ‘starship’ in truth on the Grandest Scale. Perhaps other Intelligences have begun their preparations earlier than us and we should look for very high-velocity stars leaving the Milky Way and Andromeda’s M31. Over the next aeon we might observe many, many stars flinging towards Virgo from the nearby Galactic Core black-holes.


Woven Light: Lesson Arcs

by Paul Gilster on June 20, 2014

Heath Rezabek continues his experiment in possible futures, science fiction with a collaborative bent exploring the archives that may one day preserve the story of our world and the sometimes mysterious processes that may bring them into being.

by Heath Rezabek


This is the fifth installment in a continuing series of speculative fiction here on Centauri Dreams. Feedback from prior installments helps shape the themes and direction of subsequent entries, but the purpose and focus of these pieces is to explore a timeline (or timelines) in which comprehensive, resilient archives of Earth’s biological, scientific, and cultural record — deep archives for deep time — are developed through unexpected means.

Woven Light (I) – Vessel Haven

Woven Light (II) – Adamantine

Woven Light (III) – Augmented Dreamstate

Woven Light (IV) – Proteaa

Woven Light (V) – Lesson Arcs

- – - – -

In my last installment, we launched the Centauri Dreams Vessel Survey, beginning community curation of a core booklist embodying Centauri Dreams‘ themes and influences. I discussed my work with the Long Now Foundation, showcasing their work and discussing my pending trip to be present for the opening of The Interval. We will return to both of these topics in a future installment. This week, however, I’ll continue the speculative fiction arc of Woven Light here on Centauri Dreams.

2013 was a tremendous year of change and evolution for the Vessel project; in the span of that year, the Vessel proposal moved from being a conference presentation to a published proceedings paper. After joining Icarus Interstellar to help organize the first Starship Congress, the Vessel project was summarized and presented at the event. A monograph version of that session should ultimately find its way to the JBIS special issue on SC2013.

At that conference, I met Paul Gilster, and introduced him to Nick Nielsen: There began a collaboration which continues today. Perhaps the biggest advancement of all, for me, was the opportunity to serve as an Intern with the Long Now Foundation as they began the community curation process for their Manual for Civilization collection. Although this Internship is drawing to a close, the effort has planted seeds that will continue to sprout for years to come.

With clarity can sometimes come a contradictory confusion. Even as progress on the Vessel proposal assured me that this effort had much in store, I soon discovered a large complication: To make progress on the practical proposal — the Vessel Open Framework, a specification document which could help pave the way for a unified approach to very long term archives — I realized I would need time and a team. Neither of these things are easily secured. My time remains split between these efforts and my livelihood.

Sometimes, however, help comes in unexpected forms. In this case, my conflicted feelings on how to proceed with the Vessel proposal led to a rediscovery of fiction as a vehicle for evoking and envisioning possibilities that remain unreachable in reality. My work on the Woven Light story arc continues, and if anything, is picking up steam.

Likewise, with this realization has come another shift in my perspective. While I continue to feel that a practical proposal for scalable, widespread archival efforts of all kinds is necessary, I have also come to realize that equally important is the collective role of storytellers as living archives of potent possibilities. One path forwards with Woven Light is to create a kind of fiction which can be approached from many directions, including by those inspired enough by it to try their hand at its themes and scenarios themselves.

Should humanity fail in its task in the short term, and Vessel Archives (or their like) not be constructed or created in time to forestall scattered cultural collapse or stagnation, it becomes crucially important that the stories with which humanity is left retain a trace of incentive towards rebuilding. Some would say that our advancements will soon outpace our challenges. Others would say that cases of permanent stagnation and flawed realization are already underway, in nations around the world which struggle against tides of poverty or political despair.

Where, then, is the wellspring of inspiration needed to renew a belief in the possible? Even as I continue to work at the Vessel proposal as a practical deliverable, I am working more and more on a way of storytelling which above all else plants seeds of potential in the gaps between what we can foresee and what we collectively doubt is possible.

It was a surprise, in writing, to find Thea Ramer revising the first sections of Woven Light in response to the entreaty that her robots and starships were never going to make it far in the fictional world of her present-day (an alternate-timeline 1990s), which was in turn a response to the overarching suspicion of previous comments. The resurgent myth which emerged at that point is going somewhere — Vaachez descends into the bazaar in search of a guide and map to even deeper passages, and not all in the storyline is as it seems.

As we move forwards, the number of timelines at work may begin to collapse and merge a bit — and other, unexpected ones may open up. With silence in the comments, I forge ahead sounding out the way based on the echoes already at work in the world of the story. Always, of course, comment is welcomed — it’s no longer expected: All of us, perhaps, are in unexplored territory.

One thing I do foresee is that the Vessel Open Framework will begin to unfold again, from within the world of the fiction. I take as an inspiration the experience I had in 1991 when, well after the original TV series of Star Trek: The Next Generation had ended, I encountered the ST:TNG Technical Manual, by Sternbach and Okuda. Though this kind of metafictional resource had been published before, something about the depth of thought and description in this work inspired me towards a new kind of fiction, one in which the only limits are those of our own vision, deduction, and imagination. [1]

I am thankful in the extreme to Paul Gilster, for his constant encouragement and support of this effort, a form of serialized fiction perhaps not seen before on Centauri Dreams, but now belonging thoroughly to it. I am grateful for his patience as I work my way towards a myth of possible futures that somehow includes as many possibilities as we can foresee, and asks us as readers to choose between them. Which will we accept or reject? Which will we create through our vision, or our blind spots?

Even for me, there is only one way to know, and that is to follow the work where it goes.

[1] Okuda, M and Sternbach, R. Star Trek: The Next Generation Technical Manual (Pocket Books, 1991).

- – - – -


[Image 1 - ‘Manuscript: The Tracer Guild Book 1 by Thea Ramer.’ Adaptation of photography CC BY-SA Cory Doctorow ]

1994. Thea Ramer continues her work on a novel that will be called The Tracer Guild. It will be her only published work, and will reflect but a sliver of the world she is to sketch out between now and its publication in December, 1996. These two years will be spent, for her, in a frenzy of creation, drawing upon notes she has been reworking for several years already.

The Tracer Guild — planned as the first of a series — goes so confidently astray as to float the working titles of six more planned volumes. It enjoys a brief period of uptake, before becoming overwhelmed by the market. After its publication, exhausted and bemused, Thea will put aside the work, only to return many years later, by another route entirely. And she will go through many changes.

For one, she will determine to pick up her scientific pursuits again, and return to academia. This will ultimately result in her team’s development of hologlyphic syntax, and from its hologlyphic origins, the synthetic mind called Avatamsaka.

For another, she will bear a son. His name will be Aben.

- – - – -


[Image 2 - ‘CU Boulder: Resilience, Remembrance, and the Future of Humanity Symposium 2024.’ Adaptation of photography CC BY-SA devnulled 2010 ]

2023. Aben Ramer returns to Denver from the Playa, prepared to dedicate his energy to a community knowledge and resiliency center, and grassroots version of specification document known as the Vessel Open Framework. The next year, a chance meeting at a conference at CU-Boulder introduces him to Professor of Computational Psychology, Dr, Jota Kaasura.

    Resilience, Remembrance, and the Future of Humanity. Symposium 2024.

    Lunch Keynote: From Active Imagination to Synthetic Minds: Preserving Ancestral Symbology through Jungian Design Discovery in a Computational Matrix.

After the talk, by the side of the stage as the audience mills towards afternoon, Aben reaches the presenter. Records show him young and eager, an anxious spark in his eyes. Recovered from video, this transcript remains:

Ramer: Doctor — Dr. Kaasura, I wanted to thank you. I’d never thought about it quite that way — the synthesis […unclear…] meaning through visualization — thanks for painting the picture. Oh — I’m Aben.

Kaasura: Yes, thank you. Call me Jota. I appreciated your question, ah.., Aben.

Ramer: Thanks. Ok, well so, you also mentioned that your team was seeking volunteers for the Thematic Sampling phase of input. I’ve practiced Active Imagination before, just a little, and I’d love to participate. I’m in Denver, so getting to CU’s not a problem.

Kaasura: Ah! You have? Well, excellent! It’ll be a bit yet as we gather applications. Here’s the lab’s card. We can certainly explore the possibilities. We’ll take your application and history, and we’ll go from there.

Ramer: Great. Great!

Kaasura: Out of curiosity, how did you run across Active Imagination?

Ramer: My mother used to use it for creative inspiration. She was a writer, years back — she’s actually in AI research as well, now — holography, holographic syntax. Dr. Thea Ramer?

Kaasura (brightening): Ah! Yes, yes, I know her work. Small world! She’s — didn’t she break some new ground, so to speak, in New York last year?

Ramer: Well, yes, that’s — yeah, I guess it was a breakthrough, really. But after what happened, she’s actually on sabbatical now. She says she’s not sure if she’ll return to it. I’m not quite clear on why. But she’s writing it up, so there’s time. She’s here, in fact! Well, not here-here. She was’t up for the conference, too soon she says. But she’s staying with me in Denver. We’re going through her old fiction, her drafts, trying to catalog.

Kaasura: (…) Interesting. Yes, you know, I’d actually love the chance to speak with her, if the chance comes up. Holographic syntax holds great promise. It’d be a shame for her to let it go. I mean, work goes on, always, of course, but sometimes there’s a spark, and it’s always worth perking up when that’s so. Something worth doing, there.

Ramer: Yeah. I’ll tell her. She’ll appreciate it. Maybe we can set something up. I mean she’s right here, really… Too near for a miss, right?

Kaasura: Right. Right. Good way to put it! Well, there’s my card — I do have to go, but we’ll look forward to –

Ramer: Absolutely. Thank you. I really appreciate what you’re doing, and especially why you’re doing it. Thanks for sharing that.

Kaasura: Well, thanks for such an interesting question. The unexpected ones are the best, aren’t they?

Ramer: I’ll bet they are. Great. See you soon!

Kaasura: Yes. See you soon.

- – - – -


[Image 3 - ‘Proteaa: Dyson Eggs, Living Archives’ (Detail) Heath Rezabek. Adaptation of photography CC BY-SA Wikimedia. ]

Timeframe Unknown. A reflective, refractive sphere, brimming with a maelstrom of living matter, drifts through endless night, tracing the edge of gravity’s embrace. Though utterly alone, it is not lonely, as the Protean cells which form its very quanta are entangled with many other such vessels, peer civilizations spiraling in affinity. True entanglement is a strange thing. Most of these entangled peers are smaller than itself. Most do not share the same origin. Most do not share the same gravity (which means locality, or galaxy), or space, or time.

Some, though not all, have sails; and all such sails stream ancient light.

At least one of these bears passengers, deep in stasis, living — ponderously, glacially, but metabolically living — archives.

At least one of these living archives bears the name of Ramer.

And each Ramer contains the rest.

How did this come to be?

- – - – -


[Image 4 - ‘Pendulum: Lesson Arc’. Adaptation of photography CC BY John Morgan 2013. ]

It was possible to become lost in here.

This much was well known, and all were taught the telltale signs of probability sickness early on. Vaarea Ramer did well in her lesson arcs, the small worlds adrift in fog on which she had learned to discern Realia from its echoes and shadows and subcreations.

She tracked the arc of the pendulum, swinging, swinging above an ancient pool, reflecting a blinding blue sky with each pass. Ancient, it seemed. Swinging, she felt. It was easy, seeing such a simple scene, to believe it grounded and absolute.

But she stood upon a sort of observation deck, and between her and the pool lay a gap too wide to leap, filled with fog. And beside her stood her family’s Mentor, Tuavaadha, nodding behind her veil.

~Yes, Vaarea. The pendulum would stop in time, if we waited here long enough. But there is much more to do, and even I might become bored waiting so long as that.~

Vaarea lifted her eyes, scanning the clouds for signs of anything but stasis. Her thoughts felt like a sound she heard, unspeaking, though she was the one projecting. She was used to this by now. ~What else is there to do?~

~After the Pendulum Pool comes the Grotto; at least for you. And all of your line, stretching back and back, have found it more interesting a place to be.~ Tuavaadha smiled, she knew without seeing.

And of course, she knew that she was being nudged, poked and tested, gently but inevitably. Vaarea felt a familiar irritation, which resolved itself in its familiar way into a motion of the hand. Lifting from her sash a small shard of smooth stone, she rubbed it twice with her thumb, and felt its weight shift to signal that a beacon had been placed. She’d be back, she was sure.

~As sure as your father. As sure as your son.~ Tuavaadha strode forwards, holding out her palm. A Mentor’s palm seems as wide as night, when it’s open, thought Vaarea.

She placed the stone there, and waited for the blink. But this time was different. To her right, out of eyeshot, she felt something shift and slide, and turned to see a panel of the observation platform falling away. Underneath, familiar lines of woven light interlaced and parted, indexing the scene and retracing the Voronoi frame around them.

~What about the Grotto?~ she quested, following Tuavaadha below.

~We’ll get there, impatience. We just can’t from here.~

Vaa stopped, furrowed. ~Since when can’t we get to one pattern from another?~

~Since the time it was woven that way, which means everfore.~

They were moving now, wisdom bodies flowing past the index lattice, passing pods where her peers slept and drifted, suspended in the weave.

~How far, then?~

~Not far.~

~A different lattice?~

~A different loom.~

A different loom! Now surely there was no reason they couldn’t trace a thread from one pattern to any other while remaining in the same loom. Unless by design, but why?

~Security, for one part,~ rang Tuavaadha. ~But only one part. There is something to the journey, sometimes. Something worth doing. You should know this better than most, being spun as you have from the thread of all Ramers.~

The Ghemaai were not prone to resentment, but an ancestor of Vaarea’s might have felt something sharper at the reminder that great choices had been made for her, long before her, which as far as she knew she could not unchoose. But she knew that she was also here, and alive, and flowing starwards with them all, in a way she could not be had different choices been made. And she had her vows, and they were resilient.

~So what is this, then? This Grotto we can’t reach from anywhere?~

~Anywhere else~ adjusted Tuavaadha. ~The Grotto is a family weave. ~ They were passing, now, lightflows that would have led them off towards the flowing cores, or the gathering cores, or the sinking cores; but none of these did they follow.

Tuavaadha said nothing, but smiled beneath the quiet; and Vaarea followed. So they went, in silence, weighing the memory of her shardstone, lacing it between her fingers as their footfalls silenced the deck.

Up ahead, in time, they reached a branching, and another, and a last; and there Tuavaadha stopped, as she had many times before, and waited for Vaarea to read the weave before them. It was old, but always the first time it felt fresh to new eyes. In time, Tuavaadha knew, familiarity would bring a kind of slow sorrow more like joy, keen enough to earn a name. But this time was new time.

Vaarea blinked, reaching out to touch the woven pattern of this tale. There at its center was something she’d heard of, but never seen. A cubic lattice the size of her fist was held tilted and sunken in the center of a circular plateau. Leading out from it, threads spun and raveled, and shoots reached up from loamy soil, sheltering the small camp arrayed there. This close to the fabric, she could see that the lattice stood in for a fire.

Vaarea had learned of shelterfires not two lessons prior, and shivered at the glacial cold she thought they’d left behind in a liminal valley beset by frozen seas. Around this fire sat and stood a dozen, maybe fewer, maybe more; a handful huddled – but against what cold she couldn’t see.

These grassy trees seemed city walls for them, golden green and thriving. And their tips brushed at a dusted, starry sky.

She knew better than to trace too long the lines between these diamonds, but she couldn’t help seeing the similarity – a kinship she’d never noticed in these tapestries before – between the lattice at the heart of this little shelterfire, and the splaying array of stardust beyond these trampers’ reach.

These trampers, she guessed, had tramped the path to this pattern here and now. Why so huddled? Why so intent upon the fire, if not for warmth? It shimmered and billowed, a tiny curtain, golden and ghostly above embers.

She wished she could see one in Realia. She wished she could see one patterned here and now.

~But you can, Vaarea Ramer. And you always will be able.~

So reaching out, she brushed it gently with one fingertip. And sometimes, in such places, the slightest touch is enough.

- – -


[Image 5 - ‘Woven Fire’. Adaptation of photography CC BY-SA Mathias Erhart 2009. ]

    Aben Ramer sat before the fire, stirring its coals. “I am old, now… But once I was young, like you, and you as well,” he began.
    Young eyes looked up, in awe at their elder. They had heard this beginning before, many times; always – every time – it ran on from there differently than the time before. And always – every time – it ran on like a new stream down the same mountain.
    As old Aben Ramer spoke, the children gazed and rested, their eyes sifting firelight, and then lost themselves in patterns ever changing, never changed, woven of golden light; and in through its murmuring cracks could be glimpsed the most ancient of archives, finding itself revealed again, deciphered again, read out and comprehended, voiceless and booming.
    Up reached Old Ramer’s arms,
    and as tall as the shoots far above them he seemed;
    and as full seemed the sky as their hearts and their eyes;
    and the stars seemed as close as the sparks which there met them;
    and as sure seemed the song of Old Ramer as morning.
    And in the morning, the children awoke from dreams of a dragonfly in the night, flowing starwards, wings like sails unfurling, ringed about with an arcing bowl of starlight. And among them was a girl, whose name was a new one; they just called her V.

- – -

Vaarea, stunned, hours or years later, stood just as she had before the weave, finger fading from the cubic lattice turned to fire before her. Tuavaadha smiled. ~This place – can I come here?~

~Of course; any time. All you need to do is seek it, awake or asleep, and remember that you’re seeking.~ Tuavaadha paused. ~But it helps to have some methods. In the Grotto, you will learn them.~

~That wasn’t the Grotto?~

~It was, reflected. But emulators are for studies; this place is for dreaming. We can go there tomorrow. Tonight, your assignment is just to ponder one thing, while you rest and you wait.~

Vaarea looked up, still not fully present.


~The fire: Where did it come from? Where is it going? What does it preserve? What does it destroy? Is memory stored there? And if not there, then where?~

Vaarea looked at the lattice, shimmering softly, woven into this meshwork, and closed her eyes to recall true flame, true flame unseen but everthere. She furrowed; she sighed; she looked to her Mentor for more.

~These seem like different questions, but they are not. They are conjoined. Why? For matter–

–is slumbering light~ Vaarea concluded.

Tuavaadha nodded contentedly, as any Mentor would. ~Now rest.~

- – - – -


[Image 6 - ‘Edits’. CC BY-SA Heath Rezabek 2014. ]

Thea Ramer, digging through old boxes, finds a fraying printout from long before. Old habits: Reading through it, although the time for revision is long gone, she watches herself scratch through a few words, and watches her outbreath as she does so.

If there had been a reason, these crew in theory could have navigated the actual physical spaceframe of Saudade IV.

She writes above:

    DNA (zygosphere)

She writes below:

    Reality = Bilateral (transpose?)

Thea Reamer closes her eyes, old threads of a story unwinding; and in a blink, she’s far away.

Time shifts and adapts, enfolding again all around her.



Outer Planet Exploration Strategies

by Paul Gilster on June 19, 2014

I’ll wrap up this week’s outer planet coverage with a look at recent Cassini flybys of Titan, but I also want to put these accomplishments in the context of what we might do with future missions to the ice giants Uranus and Neptune like the proposed ODINUS missions we looked at yesterday. One-off missions to explore a planet and its satellites collect highly detailed data, but comparative studies of the giant planets require accumulating datasets separated by decades. Are there alternatives?

Let’s hold that thought as we look at Cassini in this light. The flyby designated T-101 occurred on May 17 and was highlighted by Cassini beaming radio signals over Ligeia Mare and Kraken Mare, the two largest seas on Titan. The idea here is to bounce the signals off the surface of the lakes so that they are received by the ground stations of the Deep Space Network here on Earth.


Image: Signals bounced off Titan can reveal important details about the moon’s surface. Credit: NASA/JPL-Caltech.

Called a bistatic scattering experiment, the radio signals encode information about Titan’s surface, including its solidity, reflectivity and composition. The attempt using the two seas in May demonstrated that specular reflections of the radio frequencies could be detected by the DSN. Essam Marouf (San Jose State), a member of the Cassini radio science team, describes the result: “We held our breath as Cassini turned to beam its radio signals at the lakes. We knew we were getting good quality data when we saw clear echoes from Titan’s surface. It was thrilling.”

The June 18 flyby, T-102, performed the same bistatic scattering experiment, during an approach that took the spacecraft just 3659 kilometers above the surface of the moon. Both flybys also experimented with radio occultation, as this NASA news release explains. Here a signal from Earth is sent through Titan’s atmosphere toward the Cassini spacecraft, which responds with an identical signal. Temperature and density differences can be teased out of the transaction, a method that has been used for several earlier occultations of Saturn.

The May flyby demonstrated that signal lock could be achieved quickly, making the method a useful tool in our efforts to track atmospheric variations during Titan’s changing seasons.

“This was like trying to hit a hole-in-one in golf, except that the hole is close to a billion miles away, and moving,” said Earl Maize, Cassini project manager at NASA’s Jet Propulsion Laboratory in Pasadena, California. “This was our first attempt to precisely predict and compensate for the effect of Titan’s atmosphere on the uplinked radio signal from Earth, and it worked to perfection.”


Image: Cassini team members react with excitement to the successful receipt of radio signals bounced off of Titan during a flyby on May 17, 2014. Credit: NASA/JPL-Caltech

If only we had a spacecraft as capable as Cassini orbiting Uranus and Neptune, as at least one commentator here noted after yesterday’s post on ODINUS, twin spacecraft that would orbit the two worlds in a new proposal for the European Space Agency. We could then imagine repeated flybys of Triton, that mysterious geologically active moon that circles Neptune in a retrograde orbit, while performing a variety of studies on the satellite system at Uranus. I want to drop back into the ODINUS paper to cite its statements on this matter, which remind us how little data we have on these moons since our only close encounter has been through the Voyager flybys:

The satellites of Uranus and Neptune are poorly known, mostly due to the limited coverage and resolution of the Voyager 2 observations. The Uranian satellites Ariel and Miranda showed a complex surface geology, dominated by extensional tectonic structures plausibly linked to their thermal and internal evolution… Umbriel appeared featureless and dark, but the analysis of the images suggests an ancient tectonic system… Little is known about Titania and Oberon, as the resolution of the images taken by Voyager 2 was not enough to distinguish tectonic features, but their surfaces both appeared to be affected by the presence of dark material.

As for Triton, it is itself a prime inducement to put such a mission together:

The partial coverage of the surface of Triton revealed one of the youngest surfaces of the Solar System, suggesting the satellite is possibly more active than Europa… Notwithstanding this, the surface of Triton showed a variety of cryovolcanic, tectonic and atmospheric features and processes… The improved mapping of these satellites, both in terms of coverage and resolution, would allow to study their crater records and their surface morphologies, which in turn would provide a deeper insight on their past collisional and geophysical histories.

Both Galileo and Cassini have given us in-depth looks at a gas giant and its satellites, and we now ponder the kind of follow-ups that will investigate specific areas like the interior of Jupiter (Juno) and specific Jovian moons like Ganymede, Callisto and Europa (the JUICE mission). Cassini’s successes have been spectacular, but I like the approach that Diego Turrini and his colleagues take when they observe that comparative studies of the gas giants involving separate missions demand the completion of each before a full assessment of their data can begin.

Instead, Turrini argues for ODINUS as “…two M-class spacecraft to be launched toward two different targets in the framework of the same mission.” The tradeoff is likewise obvious: While we get comparative planetary data — in this case on the ice giants Uranus and Neptune — in a shorter timeframe, we also need to produce two spacecraft and manage them simultaneously, likely limiting the amount of instruments in the scientific payload of each. Can we find a way to do this while still achieving the high-quality science we expect from separate dedicated missions?

It’s an open question, and every Cassini success speaks to the value of the more traditional approach, but we should be looking at ways to speed up the comparative data return in future missions. It will be interesting to see how ODINUS fares among its ESA critics. The Turrini paper cited here and yesterday is “The Scientific Case for a Mission to the Ice Giant Planets with Twin Spacecraft to Unveil the History of our Solar System,” submitted to Planetary and Space Science (preprint).



Return to the Ice Giants

by Paul Gilster on June 18, 2014

Once New Horizons has performed its flyby of Pluto/Charon and, let’s hope, its reconnaissance of a Kuiper Belt object (KBO), what comes next in our exploration of the outer Solar System? Pushing further out, Innovative Interstellar Explorer grew out of a NASA ‘Vision Mission’ study and has been developed at Johns Hopkins University Applied Physics Laboratory by Ralph McNutt and team. Boosted by a Jupiter gravity assist, IIE would explore the interstellar medium some 200 AU and further from the Sun, using a plutonium-fueled 1 kW electric radioisotope power supply.

And then there’s Claudio Maccone’s FOCAL mission, which would target the Sun’s gravitational focus beginning at 550 AU, continuing well past 1000 AU for observations exploiting gravitational lensing effects. FOCAL has been the subject of intense study — Maccone’s 2009 book Deep Space Flight and Communications grew out of this decades-long work — and with both IIE and FOCAL we have the prospect of making observations of the medium through which any future interstellar mission would pass, having exited the heliosphere inflated by the solar wind from the Sun.

But there is much to do in the region between the gas giants, with their astrobiologically interesting targets Europa and Enceladus and the seductive Titan, and the inner edge of the Kuiper Belt. Here we are in the domain of the ice giants last visited by the Voyagers in the 1980s. A new paper from Diego Turrini (Institute for Space Astrophysics and Planetology INAF-IAPS, Italy) and colleagues makes the scientific case for a mission to Neptune and Uranus, to be flown by two identical spacecraft. The ESA-funded mission would have a launch date of 2034.


Image: Neptune as captured by Voyager 2 in 1989. Credit: NASA/JPL.

I want to focus on Turrini and team’s discussion of planet formation this morning, because this is where the scientific payoff for a return to Uranus and Neptune is the most profound. The rising tide of exoplanet research is uncovering more and more planetary systems showing us that the old view of planet formation as an orderly process producing stable, well-spaced systems is incorrect. Systems around other stars are not necessarily patterned on what we see in the Solar System. In fact, it is we who seem to be the outliers, confronting a cosmos that produces a bewildering array of planetary configurations in which migration surely plays a major role.

Thus the ‘Jumping Jupiters’ mechanism that involves close gravitational encounters that occur after the original circumstellar disk has dispersed. In our Solar System, our changing views have led to the ‘Nice Model,’ which involves our own jumping Jupiter scenario, one tied to the era known as the Late Heavy Bombardment. Here we have a series of encounters between the giant planets, with interactions with what the paper calls a ‘massive primordial trans-Neptunian region.’ The end result is to take giant planets once closer to each other and to move Jupiter inward while migrating Saturn, Uranus and Neptune outward. The paper describes this scenario:

The importance of the Nice Model lies in the fact that it strongly supports the idea that the giant planets did not form where we see them today or, in other words, that what we observe today is not necessarily a reflection of the Solar System as it was immediately after the end of its formation process. Particularly interesting in the context of the study of Uranus and Neptune is that, in about half the cases considered in the Nice Model scenario, the ice giants swapped their orbits (Tsiganis et al. 2005). The success of the Nice Model in explaining several features of the Solar System opened the road to more extreme scenarios, also based on the Jumping Jupiters mechanism, either postulating the existence of a now lost fifth giant planet (Nesvorny et al. 2011) or postulating an earlier phase of migration and chaotic evolution more violent and extreme than the one described in the Nice Model (Walsh et al. 2011).

Mixing of the solid materials that make up the primordial Solar System would have occurred, with both inward and outward fluxes of ejected material affecting the composition of primordial planetesimals. When we look at the satellites of the gas giants today, we may be seeing material that was originally extracted by these processes from the inner Solar System and incorporated in their systems.

Uranus and Neptune would have been strongly affected by these events, with a giant impact involving Uranus that explains its sideways rotation. And we can see other evidence in the capture of Triton by Neptune, Triton being a moon that orbits in the opposite direction to its host planet. The paper continues:

…our view of the processes of planetary formation and of the evolution of the Solar System has greatly changed across the last twenty years but most of the new ideas are in the process of growing to full maturity or need new observational data to test them against. The comparative study of Uranus and Neptune and their satellite systems will allow to address the problems still open, as the ice giants were the most affected from the violent processes that sculpted the early Solar System and yet they are the least explored and more mysterious of the giant planets.

Turrini and team also make the case that based on data from the Kepler mission, about one star in every five should have a Neptune-class planet, but the only up-close data we have on this class of planet comes from the Voyager 2 flybys of Uranus and Neptune performed in the 1980s. Here the authors have to pause, for Kepler’s candidates have short orbital periods because of the nature of Kepler’s operations. Kepler can only detect ‘warm’ or ‘hot Neptunes,’ whose composition and dynamics will differ from the ice giants in our own Solar System. Even so, characterizing our ice giants is something we can do with existing space technologies, and it can offer up templates for interpreting the data returned from future exoplanet observations.

From observation of the satellite systems around the ice giants to study of planetary interiors, there is much to investigate in the outer Solar System. The ODINUS mission described in the paper would put a spacecraft into orbit around both Neptune and Uranus, an ambitious goal that would allow measurements with the same set of instruments in both systems, as well as studies of the interplanetary medium from different angular positions during cruise. The ESA’s Senior Survey Committee has already stated that exploration of the ice giants “appears to be a timely milestone, fully appropriate for an L class mission,” assuming financial support emerges.

There is no question we are going to get payloads back to Uranus and Neptune at some point, and the Turrini paper makes a strong case for the scientific validity of the effort in helping us understand our own system’s violent past and the results of our planet-hunting observations in other systems. The comparatively well studied Jupiter and Saturn are composed mainly of hydrogen and helium, while Neptune and Uranus are dominated by water, ammonia and methane along with metals and silicates, with hydrogen and helium making up a scant 25 percent. We obviously have much to learn about such planetary formation outcomes.

The paper is Turrini et al., “The Scientific Case for a Mission to the Ice Giant Planets with Twin Spacecraft to Unveil the History of our Solar System,” submitted to Planetary and Space Science (preprint).



New Horizons: Hubble Hunts KBOs

by Paul Gilster on June 17, 2014

My guess is that the public thinks of the Hubble Space Telescope largely in relation to deep space objects. The Hubble Ultra Deep Field is a case in point, a region of the sky in the constellation Fornax that is no more than a tenth of the width of a full moon, but one that contains 10,000 galaxies. An image of the HUDF augmented by near-ultraviolet data has had considerable play in the media, showing star birth in galaxies five to ten billion years ago. It’s too lovely not to show here.


Image: The Hubble Ultra Deep Field with near-ultraviolet data, a false-color image that is the result of data acquisition from 841 orbits between 2003 and 2012. Credit: NASA/ESA/Caltech/Arizona State.

The HUDF attests to Hubble’s range, but we also know from Hubble’s studies of objects in our own Solar System that it can support ongoing planetary missions. Astronomers will now use the space observatory to help find tiny objects against the background of an immense starfield in Sagittarius. After consideration of the mission and the value of the data it will return, the Hubble Space Telescope Time Allocation Committee has recommended that the instrument be used to search for a Kuiper Belt Object that New Horizons can visit after its flyby of Pluto/Charon in 2015, a search contingent upon results of a pilot observation program using Hubble data.

We have two Voyagers still sending data as they push into interstellar space, but only New Horizons has a fully functioning set of instruments and the capability of making the necessary course alterations to perform a KBO flyby. The problem has been to identify the target, a hunt that could begin no earlier than 2011 because KBO candidates needed to be converging on the region of space that New Horizons can reach after the Pluto/Charon encounter. The 8.2-meter Subaru Telescope in Hawaii and the 6.5-meter Magellan Telescopes in Chile have so far been deployed on the task but it looks like it will take Hubble to make the call.

For of the roughly fifty new KBOs that the Subaru and Magellan instruments have thus far identified, none is within range of the spacecraft’s ability to maneuver. This is an extremely difficult search field, one that looks into the plane of the galaxy toward Sagittarius, and astronomers are searching for something that is both small and likely to be as dark as charcoal. But finding a target is important — the Kuiper Belt consists of debris from the Solar System’s formation, and we’ve never had the opportunity to get a close-up look at one of these objects.


If Subaru and Magellan haven’t been able to find the right KBO, Hubble will try something different, turning at the rate that KBOs are predicted to move against the background stars. As this Space Telescope Science Institute news release explains, the result will be that KBOs will show up as pinpoint objects amidst a swarm of streaky background stars. Assuming the initial test observations — 40 orbits of Hubble observing time — show that the telescope can find at least two KBOs of the specified brightness, additional observing time covering a period of 156 orbits will be allotted to search a field of view the angular size of the full Moon.

Let’s wish Hubble success because New Horizons is the successor to the Voyagers, like them involved in a journey that should captivate and inspire our culture. The more science we can get out of it, the better, even though putting a payload past Pluto/Charon is itself a grand accomplishment. As for Hubble, its efforts on behalf of New Horizons point to its previous discovery of four small moons in the Pluto/Charon system as well as its search for dust rings that might have compromised the mission. Just as Hubble has proven its worth again and again in terms of planetary science (and don’t forget its contributions to the Dawn mission), we can hope for equally impressive accomplishments from the coming James Webb Space Telescope.



What to Look for at Charon

by Paul Gilster on June 16, 2014

Let me suggest that you mark August 25th on your calendar. It’s the day we celebrate the 25th anniversary of Voyager 2’s closest approach to Neptune in 1989. That would be reason enough to look back and remember — marveling all the while at the Voyagers’ continuing mission — but it’s also the day when New Horizons will cross the orbit of Neptune. At work, as principal investigator Alan Stern points out in his latest PI’s Perspective, is ‘cosmic coincidence not design,’ but what a moment it will be as New Horizons moves at last into ‘Pluto space.’

90 percent of the long journey is over, with a bit more than 300 million miles to go before the encounter with Pluto/Charon next summer. Newly awakened from hibernation, the spacecraft will be put through a complete checkout of its onboard systems and scientific instruments, as well as conducting its first optical navigation campaign to study the approach into Pluto. Stern also reports that the upcoming cruise science will include imaging Pluto and its moons to study their light curves, seen by the spacecraft at a different angle than can be observed from Earth.

One more period of hibernation will occur before New Horizons is awakened in December, at which point the beginning of the encounter phase will be closing in. Recent work out of NASA GSFC, and an accompanying paper in Icarus, thus comes against the backdrop of a mission that will soon be answering many of our questions about this distant system. Alyssa Rhoden and team have developed a model that points to how we can study the possibility that Charon once had an underground ocean. Says Rhoden:

“Our model predicts different fracture patterns on the surface of Charon depending on the thickness of its surface ice, the structure of the moon’s interior and how easily it deforms, and how its orbit evolved. By comparing the actual New Horizons observations of Charon to the various predictions, we can see what fits best and discover if Charon could have had a subsurface ocean in its past, driven by high eccentricity.”


Image: This artist concept shows Pluto and some of its moons, as viewed from the surface of one of the moons. Pluto is the large disk at center. Charon is the smaller disk to the right. Credit: NASA, ESA and G. Bacon (STScI).

Both Europa and Enceladus show evidence for interior oceans, each experiencing tides that cause the interior to flex and heat enough to keep water under the ice in liquid form. What happened in the Pluto/Charon system depends upon its history. Charon could have had a highly eccentric orbit in the past that generated large enough tides to produce surface fractures. As tidally induced friction occurred in the interior of both Pluto and Charon, Pluto’s rotation would have slowed while Charon’s speeded up as the moon moved further away. Rhoden continues:

“Depending on exactly how Charon’s orbit evolved, particularly if it went through a high-eccentricity phase, there may have been enough heat from tidal deformation to maintain liquid water beneath the surface of Charon for some time. Using plausible interior structure models that include an ocean, we found it wouldn’t have taken much eccentricity (less than 0.01) to generate surface fractures like we are seeing on Europa. Since it’s so easy to get fractures, if we get to Charon and there are none, it puts a very strong constraint on how high the eccentricity could have been and how warm the interior ever could have been.”

So we have one more thing to look for as we approach Pluto/Charon next year. Bear in mind that Charon is unusually massive when compared to the body it orbits, about one-eighth of Pluto’s mass. Scientists believe the moon formed much closer to Pluto as the result of an impact that ejected material from Pluto to form the system of moons. Charon’s orbit is now circular, with a rotation rate that keeps Pluto and Charon showing the same side to each other at all times. Without significant tides in its present orbit, the odds are that any underground ocean inside Charon is long frozen.

The paper is Rhoden et al., “The interior and orbital evolution of Charon as preserved in its geologic record,” Icarus, published online 30 April 2014 (abstract). This NASA news release has more.



Andreas Hein, who has appeared in these pages before on the subject of worldships, here speculates about a much different kind of traveling: The uploading of consciousness. Andreas is Deputy Director of the Initiative for Interstellar Studies (I4IS), as well as Director of its Technical Research Committee. He founded and leads Icarus Interstellar’s Project Hyperion: A design study on manned interstellar flight. Andreas received his master’s degree in aerospace engineering from the Technical University of Munich and is now working on a PhD there in the area of space systems engineering, having conducted part of his research at MIT. He spent a semester abroad at the Institut Superieur de l’Aeronautique et de l’Espace in Toulouse, working on the numerical simulation of the hypervelocity impact of space dust on spacecraft antennas, and also worked at the European Space Agency Strategy and Architecture Office on stakeholder analysis for future manned space exploration. Today’s essay is drawn from his chapter in the upcoming book Beyond the Boundary, to be published by the Initiative for Interstellar Studies.

by Andreas Hein


In the movie “Transcendence”, Dr. Will Caster’s consciousness, played by Johnny Depp, is “uploaded” into a quantum computer. This feat unleashes a cascade of rapidly accelerating technological changes, culminating into a “technological singularity”. It is probably the first time that the technological singularity plays a central role in a Hollywood blockbuster. However, the hypothetical concept of uploading one’s consciousness into a computer, also called “mind uploading” or “whole brain emulation”, has been a topic in science fiction for decades. Seemingly far-fetched, mind uploading might be actually not very far from reality. Recently, the European Union’s Human Brain Project has formulated its objective to simulate the human brain. With an anticipated budget of over one billion Euros, it is the largest project of this kind ever conducted. Although the Human Brain Project’s objective is to simulate the human brain, it has spurred discussions about the prospects of mind uploading. Mind uploading might have truly transformative consequences for our civilization. Among them are the potential for digital immortality and the creation of emulated minds which might transform knowledge work, as they can be copied and used on-demand for intellectually demanding tasks (Hanson, 2008a & 2008b).

Mind uploading also opens up exciting opportunities for interstellar flight.

Image 1

Image: Part of a poster for the movie “Transcendence.” Credit: Alcon Entertainment / DMG Entertainment / Straight Up Films.

In this article, I will try to give a brief overview of existing concepts for using mind uploading for interstellar travel, as well as proposing novel concepts, which might radically change the way humans would travel to the stars. Furthermore, potential mission architectures are presented, having profound consequences on the way such a mission accomplishes its objectives.

First of all, I clarify what is meant by “mind uploading” in this article. “Mind uploading” is understood here as the transfer of mental content, for example long term memory, or consciousness, from the brain substrate into an artificial device, a digital, analog, or quantum artificial neural network (Sandberg & Bostrom, 2008). Once uploaded, the mental content can be “run” on the device as a simulation or simply stored. Analogously, “mind downloading” is defined as the transfer of mental content from an artificial device to brain substrate. Mind downloading goes hand in hand with the recreation of the human body in its entirety. Otherwise, mind downloading would not make a lot of sense for interstellar travel. If the whole body is up- and downloaded, this can be termed “human uploading” or “whole body emulation”. In this article, the boundaries between “mind uploading” and “human uploading” are often blurred. They are therefore considered to be exchangeable.

The main objective of manned interstellar travel is transporting humans to another star system and starting a new civilization there. The basic idea of using mind uploading for interstellar travel is to upload the human mind and/or body and to recreate it at the target destination. To jump-start a new, thriving civilization at the target destination requires the transfer of knowledge for performing all necessary activities. Transporting humans in digital form has huge benefits for interstellar travel: Firstly, it leads to extreme mass savings. No longer are large habitats and complex life-supporting systems needed. At the same time it offers the capability to “resurrect” living humans at the target destination, including their knowledge and thus culture, thus greatly facilitating the start of a new civilization. Knowledge and technology is transferred from the emulated brains at the target destination, either by education or “hard-wiring” emulations into biological brains.

Of course, one could speculate about the radical possibility of the complete replacement of biological life by artificial life. In this scenario, the spacecraft would be rather the “seed” for a non-biological civilization (Kurzweil, 2005).

Interstellar colonization concepts based on mind uploading can be categorized as shown in Table 1.

Table 1: Colonization tasks mapped to interstellar colonization concepts based on mind uploading

Concept 1
Concept 2
Concept 3
Concept 4
Concept 5
Transport HumansHardware static storageBrain emulationsHybrid: genetic material + emulationsElectromagnetic wavesTransmit electromagnetic waves / nano spacecraft via wormholes
Construct colonyMacroscopic replicatorsMicro / nano replicators
Establish civilizationEmulations + biological humansCyborgsEmulations + biological humansEmulation cities (Hanson, 2008a, 2008b)Matrioshka brain (Bradbury, 2001)

In order to transport humans as emulations, they need to be uploaded. Uploading might be accomplished by some advanced form of scanning. Hans Moravec was one of the first to envision a form of brain scanning, by which the human brain would be incrementally uploaded in a destructive way (Moravec, 1988). Kurzweil and others envisioned non-destructive ways of uploading, for example by using nano-scale robots that scan the brain from within (Kurzweil, 2005, p.145).

Creating a copy of the brain is a daunting task. It is far more than copying just the structure of the brain, but also the structure of individual neurons and their linkages to other neurons. What is further needed is to copy the behavior of individual neurons and larger structures in the brain. This is similar to a technical system. The understanding of how the parts of a car are related to each other does not prescribe how they work together to perform the desired function of transporting passengers. It can only be inferred by painstakingly assessing how individual components and larger groups of components perform subfunctions. These subfunctions together perform the top-level function. This reverse engineering method is called a bottom-up approach. As an alternative, one can analyze functions top-down, by first decomposing the top-level functions into subfunctions. Similar reverse engineering approaches were proposed for creating brain emulations (Sandberg & Bostrom, 2008).

After an emulation has been created, it could be switched, copied, run, and also switched off as desired (Hanson, 2008a & 2008b). For an interstellar mission, emulations could be stored and first activated at the target destination. This would save energy for running emulations during flight. Having arrived at the target destination, one can imagine how activated emulations first assess the environment within the target star system and determine the best strategy for beginning colonization. Maybe a whole population of emulations is activated, which debates possible strategies and analyzes their potential outcomes. Robin Hanson imagines various types of emulations which also form hierarchies, depending on their simulation speed. Such emulation cities on Earth would consume a huge amount of power to sustain the emulations and their virtual environment in which they exist. Manipulations of the physical world are performed by various types of manipulators and robots (Hanson, 2008a & 2008b). A strategy for an interstellar mission would be the reactivation of an initial small population of emulations which make the initial decisions of how to proceed with colonization. Then, resources would be mined and processed, in order to increase computational capability and to create a larger number of emulations, which then create biological humans along with their habitats. Another option is the simultaneous transportation of zygotes and emulations.

A more advanced version of such a mission is the initial creation of an infrastructure within the target star system by using replicators and the construction of a receiver for electromagnetic signals, for example a laser beam. Once established, data for objects could be transmitted with light speed. This is the concept of teleportation. Teleportation was often deemed infeasible, as the amount of information to be transmitted for assembling a human body molecule by molecule would be prohibitive. For example, Roberts et al. argue that a total of 2.6*1042 bits are necessary for recreating the human brain (Roberts et al., 2012). The data for recreating the rest of the human body is insignificant compared to that number (1.2*1010 bits). With a data rate of about 3.0*1019 bits per second, it would take 4.85 trillion years to transmit a human. However, a close look into the assumptions made in the paper reveals that the so-called Bekenstein bound was used for calculating the data required to recreate the brain (Bekenstein, 73), (Lokhorst, 00). The Bekenstein bound describes the maximum information that is required to recreate a physical system down to the quantum level. It is doubtful that such an extremely detailed description is necessary. Current estimates for describing the brain down to a molecular level are rather in the range between 1022 – 1027 bits (Sandberg, 2008, p.80). This amount of data could be transmitted within an hour to ten years, assuming the same data rate of 3,0*1019 bits per second. Thus, teleportation might not be as far-off as suggested by the current literature. A mission architecture based on teleportation is shown in Figure 3.

One of the more speculative approaches to enable manned interstellar travel with almost no travel time is to use some form of faster-than-light approach. There is a whole plethora of conjectured faster-than light approaches (Davis et al., 2009). Sending pure data or nano probes through shortcuts in space-time is far easier than doing so with large manned spacecraft. Kurzweil speculates how microscopic wormholes might enable the transmission of data or nano probes to another place in the Universe (Kurzweil, 2005, p.354-355). A mission architecture based on this concept is shown in Figure 4.

Mission architectures

Digital interstellar missions open up a space of interesting mission architectures. Depending on the available technologies, various architectures are feasible, as shown in Table 2.

Table 2: Digital mission architectures and their enabling technologies

Replicator technical systemsrequiredrequiredrequiredrequired
Replicator / Grow biological systemsrequiredrequiredrequiredrequired
Brain emulationrequiredrequiredrequiredrequired

Architectures A to D can be seen in the figures below, along with their mission sequence.

Architecture A

1. Send replicator + emulator / storage spacecraft
2. Create colony and resurrection infrastructure
3. Create population

Figure 1

Fig. 1: Single spacecraft mission with digital and replicator payload. This so-called “bat chart” shows the mission sequence from left to right. The inclination of the arrows indicates how fast the spacecraft arrives at the target. The steeper, the faster.

This is the simplest mission architecture for an emulation interstellar mission. The spacecraft consists of the emulator payload and a replicator payload which bootstraps local resources to manufacture the initial space colony. The emulations are subsequently downloaded and human bodies are created.

Architecture B

1. Send replicator
2. Create colony and resurrection infrastructure
3. Send emulator / storage spacecraft
4. Create population

Figure 2

Fig. 2: Split mission with separate replicator and digital payload

Architecture B is based on two spacecraft. The replicator spacecraft is launched first, in order to initiate colony construction way before the emulator spacecraft arrives. This architecture makes sense if colony construction takes decades or centuries. The main advantage is the reduction of risk from a failure to construct the initial colony. The emulator spacecraft could be launched only if the colony is operational. Another advantage is the use of a different propulsion system for the emulator ship, allowing for a shorter trip duration than the replicator ship. A shorter trip duration reduces the risk of failures of on-board systems, which is more critical for the emulator ship as it has in principle a human payload on-board.

Architecture C

1. Send replicator spacecraft
2. Create receiver dishes in target star system
3. Receive data for creating technical systems & humans

Figure 3

Fig. 3: Replicator mission which builds up a receiver for technologies and humans to be created within the star system

In order to teleport data, a receiver has to be constructed within the target star system first. This is done by the replicator spacecraft’s payload. Apart from the receiver, a molecular assembly facility or universal 3D-printer has to be constructed, which then recreates the original objects. The main advantage of this architecture is the travel duration for the objects transferred, as the data is transmitted is the speed of light.

Architecture D

1. Send replicator spacecraft
2. Build receiver
3. Use wormholes to transmit information to receiver
4. Create technological systems & humans

Figure 4

Fig. 4: Using a worm hole for transmitting data for technologies and humans with faster than light speeds

After the construction of a receiver and molecular assembly facility, data is transferred almost instantly through a worm hole or other exotic means.


The concept of brain emulation is often associated with the occurrence of the so-called technological singularity, which is often associated with the emergence of general artificial intelligence and its exponentially increasing capabilities. Whether or not it is reasonable to expect such a singularity to happen is the matter of intense debate among scholars (Sandberg, 2010), (Sandberg & Bostrom, 2011), (Goertzel, 2007). Personal conversations with a range of brain researchers have rather revealed a skeptical outlook on progress in creating brain emulations in the near future. Nevertheless, there is no doubt that progress is being made. Brain emulation and general artificial intelligence should not be discarded on the grounds of current or near-future infeasibility, as we are dealing with timeframes of decades to centuries until interstellar missions are conducted.

As a final remark, Launius & McCurdy point out that a posthuman civilization does not necessarily possess the motivation to conduct an interstellar mission (Launius & McCurdy, 2008, pp.218-219). Thus, one has to keep in mind that changing the human condition so profoundly will certainly have consequences for its behavior as well.

Although the prospects of mind uploading are controversial, its realization within the 21st century should not be deemed infeasible. It is even imperative to think about possible implications of this technology, as its realization would drastically change our civilization as well as it would revolutionize interstellar travel. How would it then feel to travel to the stars? After being scanned, would we suddenly wake up in a new body on an exoplanet? Would we instead pass our time in a virtual world crossing the space between the stars, finally transforming into a biological existence again? Fascinating but also somewhat chilling thoughts…


Bekenstein, J. D. (1973). Black holes and entropy. Physical Review D, 7(8), 2333.

Davis, E. W., & Millis, M. G. (2009). Frontiers of propulsion science. American Institute of Aeronautics and Astronautics.

Goertzel, B. (2007). Human-level artificial general intelligence and the possibility of a technological singularity: A reaction to Ray Kurzweil’s The Singularity Is Near, and McDermott’s critique of Kurzweil. Artificial Intelligence, 171(18), 1161-1173.

Hanson, R. (2001). Economic growth given machine intelligence. Journal of Artificial Intelligence Research.

Hanson, R. (2008a). Economics of brain emulations. In Tomorrow’s people – proceedings of the james martin institute’s first world forum: EarthScan.

Hanson, R. (2008b). Economics of the singularity. Spectrum, IEEE, 45(6), 45-50.

Kurzweil, R. (2005). The Singularity Is Near: When Humans Transcend Biology, Penguin Books.

Launius, R. D. (2008). Robots in space: technology, evolution, and interplanetary travel. JHU Press.

Lokhorst, G. J. (2000, May). Why I am not a super-Turing machine. In Hypercomputation Workshop, University College, London (Vol. 24).

Moravec, H. (1988). Mind children. Cambridge, MA: Harvard University Press.

Sandberg, A., & Bostrom, N. (2008). Whole brain emulation: A roadmap. Future of Humanity Institute, Oxford University. Available at: Accessed July, 3, 2010.

Sandberg, A. (2010). An overview of models of technological singularity. In Roadmaps to AGI and the future of AGI workshop, Lugano, Switzerland, Mar. 8th. http://agiconf. org/2010/wp-content/uploads/2009/06/agi10singmodels2. pdf.

Sandberg, A., & Bostrom, N. (2011). Machine intelligence survey. Technical Report, 2011-1. Future of Humanity Institute, University of Oxford. pdf.



The Worldship of 1953

by Paul Gilster on June 12, 2014

Les Shepherd’s 1952 paper “Interstellar Flight” appears in the Journal of the British Interplanetary Society,” a fitting place given Shepherd’s active involvement in the organization. He would, in fact, serve the BIS as its chairman, first succeeding Arthur C. Clarke in that role in 1954, and returning in 1957 and again in 1965 for later terms of office. “Interstellar Flight” is one of those papers that turns people in new directions after they have read it, and we can see the gradual acceptance of travel between the stars as a possibility that does not violate the laws of physics beginning in its pages.

Much less heralded but more widely seen was an adapted version of “Interstellar Flight” that appeared in Science Fiction Plus in April of 1953. The magazine was a revival of Hugo Gernsback’s career as a science fiction publisher that ran for seven issues before its demise in December of the same year. Gernsback’s name was revered in science fiction circles as the founder of Amazing Stories in 1926, and for his later career with Science Wonder Stories and Air Wonder Stories, magazines he would eventually merge before selling his interest entirely in 1936. In contrast to these earlier titles, Science Fiction Plus was printed on slick paper and featured glossy covers, though many of the writers Gernsback used had worked with him in the Amazing Stories days.


Science Fiction Plus was an interesting venue for Shepherd because it exposed his work to an audience that had already encountered science fiction treatments of interstellar concepts like the generation ships he wrote about in the following paragraph:

At first sight the idea of advancing mankind’s frontiers to points requiring hundreds or even thousands of years to reach, might seem hopeless. It cannot indeed be regarded as a particularly satisfactory picture of interstellar exploration. However, regarded in terms of geological eras, centuries or millennia are small intervals, and provided that human life can be sustained in exploring vehicles for long periods, there is no reason why interstellar expansion should not proceed on this basis.

I can envision the Gernsback audience soaking this up, familiar as many of these readers would have been with stories like Robert Heinlein’s “Universe” and Don Wilcox’s “The Voyage that Lasted 600 Years.” The latter, which appeared in Amazing Stories in October of 1940, tells the tale of one Gregory Grimstone, who spends an interstellar voyage in a state of hibernation, but is wakened once every hundred years as the ‘Keeper of Traditions,’ the one contact the crew still has with the Earth left behind many generations before. Here we have the same theme of lost knowledge and a crew gradually losing the meaning of their journey that we find in Heinlein’s Orphans of the Sky and a variety of later tales.

Image: Pioneering physicist Les Shepherd, whose work on interstellar flight has influenced generations of subsequent researchers.

The magnitude of the journey in terms of space and particularly time is well captured in Shepherd’s essay:

The author is not competent to deal with the biological problems of life on an interstellar vehicle undertaking a voyage lasting for a millennium. Obviously they would assume a magnitude quite as great as the engineering problems involved. In the normal way, some thirty generations would be born and would die upon the ship. It would be as though the vessel had set out for its destination under the command of King Canute and arrived with President Truman in control. The original crew would be legendary figures in the minds of those who finally came to the new world. Between them would lie the drama of perhaps ten thousand souls who had been born and had lived and died in an alien world without knowing a natural home.

Now, as to those italics. They’re clearly Gernsback’s, a suspicion natural to anyone familiar with his editorial style. The JBIS paper containing the identical passage has no italics at this point, and it’s clear that Gernsback wanted to drive home the science fictional ‘sense of wonder’ of Shepherd’s remarks with his typesetting. I’m not sure the audience needed the hint. I still find the idea of multiple generations living and dying aboard an interstellar craft to be mind-boggling even when presented in the lean text of the average scientific paper.


Shepherd would go on to discuss worldship issues ranging from population control — for humans and journeying animals — as well as the huge problem of life-support systems in a self-contained world. He saw the only feasible way to make a journey like this would be in a ship of gigantic proportions, and for him, that meant hollowing out ‘a small planetoid,’ one of perhaps a million tons (excluding the weight of propellants and fuel). He believed artificial gravity should be induced by rotating the ship, and he pondered the question of maintaining an atmosphere over the course of ten centuries. On matters of sociology, he said this:

The passage of perhaps thirty generations would pose major problems of a sociological nature. The control of population would be only one of many. Children could only be born according to some prearranged plan, since overpopulation or underpopulation would be disastrous. The community would be subjected to a degree of discipline not maintained in any existing community. This isolated group would need to preserve its civilization, and hand on precious knowledge and culture from generation to generation and even add to the store of science and art, since stagnation would probably be the first step to degradation.

I don’t want to give the impression that Shepherd’s “Interstellar Flight” is solely about worldships, because the original JBIS paper was wide in its scope, examining nuclear fission, fusion and ion propulsion and going into depth on the possibilities of antimatter. Giovanni Vulpetti has pointed out that antimatter had been little studied in terms of propulsion at the time Shepherd wrote, and it was Shepherd who brought the concept out of the realm of science fiction and into the realm of serious physics with this single paper. We owe much to “Interstellar Flight,” published a year before Eugen Sänger’s famous paper on photon rockets, and I think Shepherd was wise to let Gernsback publish a version of it that could reach a broad popular audience.

As for Gernsback, he was canny to bring a serious study of interstellar travel into the pages of his young magazine, although not as successful when it came to story selection. Science fiction historian Mike Ashley has noted a certain archaism in the fiction here because of Gernsback’s reliance on writers from the previous generation. Even so, one Science Fiction Plus story still stands out. It’s Clifford D. Simak’s “Spacebred Generations,” from the August, 1953 issue. As the title implies, this is a worldship story that flows naturally out of Shepherd’s own speculations. We’ll take a closer look at what Simak has to say in an upcoming post.

Les Shepherd’s original paper on interstellar propulsion is “Interstellar Flight,” JBIS, Vol. 11, 149-167, July 1952, from which the article in Science Fiction Plus was adapted.



Cultural Evolution: The View from Deep Space

by Paul Gilster on June 11, 2014

I didn’t have the chance to meet Mark Lupisella at the first 100 Year Starship symposium in Orlando, but the publication of Cosmos & Culture: Cultural Evolution in a Cosmic Context in 2013 made me wish I had sought him out. Co-edited with Steven J. Dick (about whom there are so many interesting things to say that I’ll have to carry over into a future post with them), Cosmos & Culture offers essays from scientists, historians and anthropologists about the evolution of culture both on Earth and, most likely, beyond it.

These are, of course, issues we’ve been considering recently in the work of Cameron Smith and Kathleen Toerpe, and in a broader sense they inform many of the SETI and astrobiology discussions we have here. Then Clément Vidal, who is an author and a post-doctoral researcher at the Free University of Brussels, passed along the paper I missed in Orlando, Lupisella’s “Cosmocultural Evolution: Cosmic Motivations for Interstellar Travel.” To be fair to myself, we all missed plenty of papers at the first 100YSS, because there were five simultaneous tracks and it was impossible (at the current state of technology) to be in more than one place at a time.

NASA's Spitzer Space Telescope has captured a new, infrared view of the choppy star-making cloud called M17, also known as the Omega Nebula or the Swan Nebula.

Image: A Spitzer infrared view of the Large Magellanic Cloud, a satellite galaxy to the Milky Way. How we define the human role in a cosmos of such immensity has ramifications throughout our culture. Credit: Spitzer Space Telescope/JPL.

I want to draw on Lupisella’s work this morning because it intersects with an issue I often deal with: How do we state a rationale for expansion into the cosmos? Lupisella discusses a very interesting ‘cosmocultural evolution’ that I’ll get to in a moment, but let’s focus on the motivations for going off-planet that inform any discussion about space. I take it for granted, for instance, that one key driver for a long-term human presence in space is simple survival, the universe being a dangerous place, and our Solar System littered with evidence in the form of space debris and cratered terrain of what can happen when one astronomical body runs into another.

Not everyone agrees with this motivation. I’ve written before about one dinner party where, in the midst of a discussion about everything but the future, one of the guests suddenly asked me why I spent so much time writing about space. It soon became clear that the consensus at the dinner table held that money spent on space was wasted by being diverted from pressing needs on Earth. After I had explained my view that our species needed to insure itself against future catastrophe, my first interrogator said, “Why? I would think that if we found a huge object headed for our planet, we would be doing the universe a favor by letting it hit us and getting it over with.”

So you can’t count on survival as a trump card. And by the way, trying to get past the attitude just cited is probably impossible, because anyone that misanthropic isn’t going to give ground even when reminded that if he did let an incoming asteroid hit the Earth, he would be signing not just his own death warrant but those of his grandchildren and everyone else’s grandchildren as well.

Lupisella sees interstellar flight as “the ultimate insurance policy,” but he brings to the question an added ethical dimension. We should consider our survival as necessary, in this view, because of the possibility that we may ultimately play a role in the broader evolution of the universe. So maybe we want to thrive and prosper not just for ourselves but for the sake of the meaning we can bring to life’s experience in the cosmos.

I find this a heartening view, but let’s add to it some other factors Lupisella pointed to in Orlando. A human presence in space sets up the conditions for countless new experiments in culture and philosophy, which means experiments in everything from social organization to means of governance, all of which would be interesting in and of themselves as well as providing data that could be of use for those remaining on the home world. The cultural experimentation this implies could also be complemented by new contexts for biological evolution — Freeman Dyson has written often about what could happen to our species as we begin to live in radically different environments and essentially begin to fork into various branches of homo sapiens, while the aforementioned Steven J. Dick has explored the emergence of post-biological intelligence.

Cultural diversity flows naturally out of all this, surely healthy for the species, but so does what Lupisella calls a ‘cosmic promotion,’ the reverse of the great demotions we have undergone throughout history as we adjusted our views of the cosmos. We’ve accustomed ourselves to being dethroned from the center of the universe, from being the place around which the Sun revolves, from being at the center of the galaxy, from being in the galaxy as we learned how many of them there are, and so on. Lupisella’s view of cosmocultural evolution suggests that although life, intelligence and culture could arise by chance, they still might have cosmic significance, or as he says, “Modest origins do not imply modest potential.”

Here’s the argument in a nutshell:

If the universe didn’t have value and morality prior, it does now. If it didn’t have meaning and purpose prior, it may now. If it didn’t have intentional creativity prior, it does now. We may be a very small part of the universe that arose by chance, but nevertheless, strictly speaking, the universe now contains morality and a kind of intentional creativity it may not have had prior to the emergence of cultural beings like us. We cultural beings, in some nontrivial sense, make the universe a moral and increasingly creative entity, however limited that contribution may be for now. Increasingly, human culture is expanding its circle of creativity and moral consideration. Perhaps interstellar travel can help expand a circle of moral creativity to the whole of the universe.

Does this remind you of anyone? For me, this is strikingly similar to Michael Michaud’s calls to bring meaning to the cosmos. In one of our dialogues in these pages (see Spaceflight and Legends: A Dialogue with Michael Michaud), the author and diplomat said this:

The moral obligation to assure the survival of intelligence is not imposed on us by gods or prophets, but by our own choices. Call that anthropocentrism if you will. I prefer to think of us as independent moral agents, perhaps the only ones in the galaxy. Until and unless we discover another technological civilization, we have a unique responsibility to impose intention on chance.

I love that phrase ‘to impose intention on chance’ and have used it in several talks. You may have run into Carl Sagan using language a bit like this. When pressed on what happens to humanity in a universe that can seem without meaning, Sagan would reply “Do something meaningful.” I take this to mean, whatever your views, whatever your angle on life, shape events toward a meaningful outcome. Don’t, in other words, let that asteroid hit the Earth. And no matter how bewildered you may be about your place in the cosmos, go forward and do your best.

I draw strength from Lao Tzu: “You accomplish the great task by a series of small acts.” The things we do every day to give meaning to our lives matter. Make them count.

Lupisella notes that in 2007, a panel of experts meeting at the Future of Space Exploration Symposium at Boston University recommended that a 50-year global vision be developed to guide future human space efforts. I am all for such long-term thinking and believe it dovetails nicely with our growing understanding of the meaning we can bring into being as we work. How energizing it is to see the cultural issues of future spaceflight in active discussion. Clément Vidal, by the way, has a book of his own coming out. I look forward to seeing The Beginning and the End: The Meaning of Life in a Cosmological Perspective, just published by Springer.