Author: Adam

What to do Before the Sun dies…

A couple of posts ago I fast-forwarded to the year 400 trillion, found an utterly abyssal darkness, and thus pondered Infinity. Infinity may or may not exist, but in either case it can be studied mathematically. Whether any of that transfinite mathematics refers to anything beyond our concepts remains firmly “unknown”.

In the next 5.5 billion years – the time to the end of the Sun’s Main Sequence – we might know whether Infinity exists or otherwise. We might also go extinct. Almost certainly our current genetic makeup, as Homo sapiens, will no longer exist, even if our human-like descendents are still thriving “in the Light of the Sun”. Genomes change endlessly and without positive selection to prune them, they’re likely to fill up with “junk” – like the Australian Lungfish, Neoceratodus, whose genome is huge, but mostly “junk”. Likewise its African and South American kin – for example, humans have 3.5 picograms of DNA per cell, while the Lungfish can have +132 picograms. Many other species have similarly junked up genomes, with some oddities but generally the animals with slower metabolisms have bigger genomes, perhaps because there’s no selective disadvantage when the genome doesn’t have to be read in a hurry.

So genomes change, continually. We can either help the process, by positive engineering, or be victims of it, when mutations produce undesirable outcomes like disease. At present this is an ethical battleground, but the long-term instability means that our genomes will change. But how will we change? Presently we’re making our own environments out of what we encounter, but this isn’t the only approach. Humans could be remade for new environments – we may well subtly change even if we try to reshape other worlds to suit us. I don’t think complex DNA life can be endlessly adapted to empty space, high radiation, strange atmospheres and so forth, but large complex beasts like us might be “tweaked” to thrive where we might otherwise struggle.

On a terraformed Mars we might be adapted to handle high levels of carbon dioxide. We might be given better cold adaptations on a partially terraformed Titan, given wings to fly on low gravity worlds, or adapted to breathe the oxygenated waters under the ice of Europa, tolerate high levels of ammonia on defrosted moons, lower levels of oxygen when more methane is needed, or even learn how to photosynthesise in the clouds of Venus. Cryptic fungal growths on the walls of reactors might teach us how to thrive on x-rays, thus allowing colonisation of planets around flare-stars. We might learn to extract biological energy from the radiation belts of Jupiter, repair our genomes and make air-tight skins to stand in the warmth of Io’s volcanoes.

I’m not saying that’s what we will do tomorrow, but in the gigayears between now and the End of the Main Sequence, someone may do such things.

What about re-engineering the Worlds themselves? Just about anything is feasible given the timescale we’re contemplating, but what is desirable? To me the vast vistas of the Solar System are meaningless without Life taking hold of them. We have no evidence – yet – of Life anywhere else, and we might find nothing in our Solar System that didn’t originate on Earth. If panspermia means all Life in our Solar System is related, then we would be doing what Life does and reshaping our environment to suit us.

With that in mind: what’s the best use of planetary resources for Life’s sake? Some 413 Earth masses of material is stuck inside the two biggest planets as energy-rich fusion fuels – hydrogen and helium. Currently we can’t fuse either very effectively, but assuming we eventually learn the trick the energy store in both is about 375 Earth masses (just over 0.1% of the Sun’s mass) and useful for several billion years. If we turned either world into mini-Suns we could then orbit large numbers of terraformed bodies around them in complex, but dynamically stable, multi-planet orbital configurations. Imagine raiding the Oort cloud for all those Moon-to-Mars sized bodies to terraform, slowly positioning them over millions of years, and setting them into elaborate orbital dances around the mini-Suns.

How much room would that make? Mars is 0.532 Earth’s radius, thus has an area of 0.283 Earths. 350 of these would have a collective area of 99 Earths, while just massing 35 Earths. The Moon has a radius of 0.273, area of 0.0745 Earths, and would have an area of 212 Earths for the same mass. How big should a practical planet be? Or how small? It’s clear that the smaller we go, the more area we get, for the same mass. At some point the artificial planets are too small for useful surface gravity and might as well be reformed into rotating Cylinder Cities. I have a bias towards real planets and not rotating hollow surfaces, mainly because of the rotational energy tied up in large Cylinder Cities means they’re liable to fly apart if structurally compromised.

Hollow planets might be possible with sufficiently strong and dense materials. The gravity field of a hollow sphere, outside the sphere, is the same as if all the mass was concentrated at the centre in a point. Inside there is no gravitational force from the shell itself, as it all cancels out. Imagine if Jupiter’s mass was made into a shell at the 1 gee level – now it would be 110,000 km in radius and have an area of 300 Earths. Since the shell isn’t rotating to make gravity it doesn’t suffer from the liability that Cylinder Cities are inherently prone to. To provide 1 gee gravity the shell, if made of diamond, would be 3,600 km thick and thus probably not strong enough for the task. Some kind of dynamic support will be needed – gas or Paul Birch’s “Dynamic Compression Members”. That’s an engineering detail for the year +1,000,000 or so.

If we were really starved for mass, and didn’t want to wait for Jupiter & Saturn to be fused into carbon/oxygen, then Sun-mining via ramscoops would allow a ~20 Jupiter masses of heavier element to be extracted. Imagine if 1/6th gee, Lunar gravity, is enough for the Shell-worlds. Thus ~120 Shell-Worlds can be made, with an area of 36,000 Earths.

Of course if we really bit the bullet and adapted to zero-gee then non-rotating gas-filled spheres could be built for habitable area. A proper Dyson Swarm/Cloud could be built, perhaps multi-layered with Life-processes on each layer being powered by the waste heat of the next layer in. Thus Robert Bradbury’s Matrioshka Brain might be the end state of Solar System life, with all individuated Life living as emulations in the collective Solar Mind. Or perhaps the Mind would be distributed as the Habitat Itself, a kind of Super-Gaia (Solaria?) My physical suspicion is that Life, to be Life, needs the physics of real molecules and thus can’t be mere emulations, except as emulated by real particles. Thus a Living World might be the preferred end-state for “Computronium”, a true merger of Technology (Mind) and Physics (Nature)…

Deuterium Fusion Rockets

Back in the 1950s a lot of work was done on the practical aspects of triggering fusion in various bomb designs and fuels. A relevant fuel is deuterium. Friedwardt Winterberg was a nuclear physicist involved in the very secret work on triggering fusion reactions without using fission bombs to create the solar-interior conditions needed for the reaction. Now some of that work has been declassified and Winterberg has put two new papers on the arXiv…

Deuterium microbomb rocket propulsion

Ignition of a deuterium micro-detonation with a gigavolt super marx generator

…which might allow nuclear fusion Orion-style rockets to launch from Earth without the fallout.

What to do after the Sun dies

A recent posting to the Physics arXiv asks how best to save the Earth from the Sun’s demise. While the Sun is on the Main Sequence, and in the Redwards Traverse, a soletta shade in the Earth-Sun L1 point should suffice. But when the Sun starts puffing up into a Red Giant, peaking at about 2730 times present insolation levels, the authors suggest building an artificial sun, from brown dwarfs, and parking Earth (and other planets) in orbit around it. A mammoth undertaking and, to my mind, not the most efficient use of resources. One possibility is to enshell Earth, and other useful planets, in a variably reflective shell and control surface temperatures by reflectivity. Thus, when insolation has climbed to 2730 times the present day, a reflectivity of 0.999 will be needed – the Sun’s 33.2% mass loss will put Earth 1.5 AU out and so the insolation will be ~1,218 times present day levels.

But that mass-loss will be a problem – a solar wind some 380,000 times present levels. Remember just 1,000 times present day stripped ancient Mars of ~90-95% of its atmosphere. In fact the problem is so bad it might cause the Earth to deccelerate and end up in the Sun – if it doesn’t, tidal forces might well. So what to do? The current solar wind exerts a force of roughly 17.2 MN against the Earth’s magnetic curtain (about 10 times bigger than Earth), so that will rise to 6.54 TN as the Sun blows itself away. A reflective shell deflecting 1,000 times present day sunlight and the same size might add 120 TN to that. Coupled mechanically to the Earth this will exert an outward acceleration of 2.11E-11 m/s^2… more than enough to push it outwards during the 60 million years of solar mass-loss.

When the Red Giant Branch of the Sun’s evolution is over, its core explodes in a runaway fusion reaction heaving the rest of its mass onto the Helium Main Sequence, some 50 times brighter than at present, where it happily burns for 100 million years. Now at 2.25 AU Earth’s reflective shell needs to reflect ~90% of the incident light to remain pleasant for current DNA-based life-forms. At the end of the Helium Main Sequence the core turns into a soon-to-be White Dwarf and about ~0.13 Solar Masses is blown away, while the luminosity jumps again into the thousands. This extreme behaviour lasts mere millions of years and by the end, some 7.7 billion years from now, the Sun is a Carbon/Oxygen white dwarf massing ~54% of its present day mass, shining only by its immense store of heat. Fusion reactions of carbon/oxygen can’t proceed because the core is too light-weight. The core needed to be ~0.9 solar masses to initiate the next stage, but it would do so nearly uncontrollably, proceeding to burn incredibly fast at ~1000 times brighter than today.

But a White Dwarf isn’t merely a dead star. It’s a very dense object with high gravity – given the right encouragement it’s a gigantic fusion reactor waiting to happen. If our descendents feed it (call it the X-Sun) hydrogen/helium from interstellar space, burning at a sedate x1 present levels, then the X-Sun can burn another ~0.36 solar masses up to the carbon/oxygen fusion mass-limit. That much hydrogen/helium fused represents ~40 billion years. If the carbon/oxygen fusion can be controlled, another 0.54 solar masses can be burnt before the Sun hits the Chandrasekhar Limit – the mass at which it can collapse in an implosive runaway into a neutron star/Type Ia supernova. If the fusion can be controlled further, burning carbon/oxygen all the way to Iron/Nickel, then 0.9% of the total mass-energy of the X-Sun can be liberated. At the sedate x1 output that means about 100 billion years total.

Enough for some, but can we do better? Greg Laughlin recently posted a graph on the Galaxy’s Deep Future… That Sunday Afternoon Feeling …which shows the Galaxy staying roughly as bright as it is today for next 800 billion years, due to stars aging and becoming brighter as they become Red Giants. Eventually the stars stop becoming Red Giants (at 0.3 solar masses) and instead brighten slightly and fade out as helium white dwarfs – they can’t hit the Helium Main Sequence. Conceivably this can be remedied by merging stars or feeding the helium to White Dwarf X-Stars of higher masses, but even such titanic efforts will eventually come to naught if we stick with fusion powered stars alone.

So what next? Two options –

  • catalysed proton-decay, via small black-holes, could allow the total mass energy of stars to be used up. In the case of the X-Sun that’d be another 20 trillion years of shining bright before all the mass is gone.
  • Dark-Matter burning. Some Dark-Matter models have self-annihilating particles which produce real, visible energy. These could, theoretically, be channelled in to old stars to power them. Assuming x10 dark-matter to star-matter, this might power a bright Galaxy for ~400 trillion years.

    • By then all that’s left is a slowly expanding cloud of leptons and a swifter bubble of photons shooting away at lightspeed. Just a bit chilly, unless some other energy source can be found. While 400 trillion years sounds like an Eternity, it’s really a speck in a vast sea of Time. Matter itself – protons and neutrons – can persist 10^40 years or so before virtual black-holes cause proton-decay. The ratio of 400 trillion years to 10^40 years is the same as the ratio between the Universe’s current age and the first 0.2 of a micro-second. Freeman Dyson, in 1979, suggested Life needed to scale itself to the natural processes of cosmic evolution – essentially running its clock ever slower as energy sources became more attenuated. Assuming long periods of inactivity (though how do you mark the time?) his equations suggested Life could ‘think’ an infinite number of thoughts with finite energy supplies during Endless Time.

    The ‘Clock problem’ and, more recently, the Waste Heat problem, mean that Dyson’s first version of the argument is disproven. Infinite subjective time will need either infinite energy or will result in endless repetition of thoughts if non-dissipative computing is used, thus effectively being ‘finite time’ anyway. Infinite energy can only become feasible if the Universe is collapsing AND space-time is infinitely divisible. The first is open to falsification, and thus is meaningful scientifically (even if eventually disproven), but the latter is a philosophical issue that’s hard to turn into meaningful physics. Frank Tipler thinks he has done so, and his Omega Point Theory posits one way that Life might have an Infinite Subjective Life, but with the curious result that it all happens in a hot, dense speck growing ever smaller in a finite “objective” time.

    A lot of physicists like infinities – either Singularities, or Infinite Space, Parallel Worlds or whatever. I find them rather mind-boggling, but that doesn’t necessarily make them unreal. But none of them are open to scientific verification – they can only ever be falsified by running up against a finite Limit. And there’s no telling where or when that’ll happen…

Carnival of Space #81

Yep, it’s up at Tiny Mantras… diverse as always. Check out David Portree’s Altair VI and his two-part post on Phil Bono’s MarsGlider of 1960 (and Part 2) which landed, in some other Universe, in 1971.

Not at the Carnival, but worth a look is Murray Leinster’s 1946 (!) SF story that prefigured the Internet: A Logic Named Joe… he called it so well, even if his singular invention of the computer didn’t happen.

Just How Big Can They Make Them?

Paul Birch sprouted a few terraforming ideas in the early 1990s that deserve more attention in such discussions IMHO.

He has an unpublished paper online which discusses some very interesting technologies for terraforming Mars and Venus. He estimates that both planets could be given breathable atmospheres in ~20 years – Venus could be cooled sufficiently to cause its atmosphere to condense in about a decade using a clever cooling technique he describes. A vast system of planet-circling hollow balls with a bit of water inside would be enough to actively cool the planet, once a sufficiently opaque soletta is in place.

But, as he notes, three planets in one system isn’t much for a growing civilization. He proposes some very elaborate and clever ultra-structures one of which answers the post title: a SupraSelf. The object is a multi-layered structure 1.2 lightyears across which has one-gee surface gravity from its own mass. In my mind it’s physically the ultimate artificial habitat until we learn how to make pocket Universes – for that idea check out Greg Egan’s story Borderguards.

A habitable object 1.2 light-years across would mass 2 trillion solar masses – twice the Milky Way. Such an object would be visible via its waste heat, but the red-shift would make it almost invisible – thus making for a hefty “Dark Matter” Galaxy. Birch says the inner layers (it is composed of 30 million nested shells) could have a red-shift/time-distortion factor of 2,500 making for some very curious possibilities indeed. Total area is ~200 billion trillion Earths – all of it inhabitable, unlike most of Earth. A population of 10^35 would be feasible. Surely a worthy effort for a Kardashev Type III to create over a few billennia.

News-bites… 22 November 2008

Mars’s equatorial regions are covered in glaciers… Vast glaciers on Mars

Our ancestors had floppy, flexible gibbon feet …gibbons give a hint what our bipedal, but arboreal, ancestors were doing to get around. More Here

Villa living in 4,500 BC… 6,500-year-old village found in Greece

Did asteroid cause ancient N.Y. tsunami? …”Deep Impact” back in 300 BC.

Rain-making Bacteria and the Global Water-cycle …could be a whole biosphere in the upper atmosphere. If here, then why not Venus?

Mystery Source of Cosmic-Rays is less than 1,000 ly away …any further and the electrons being seen are dispersed and lose energy.

Concealed Glaciers Discovered On Mars At Mid-latitudes …more on the Mars Glaciers.

New Life Beneath Sea And Ice …new ecosystems surprisingly richer than imagined. one is deep beneath Antarctica’s glaciers, the other is in the interface between hypersaline lakes and regular seawater on the Mediterranean sea-floor. Both are full of life.

Always more news, but most of it you’ve doubtless seen yourself. The giant motile Protist is pretty amazing – potentially a “living fossil” nearly 2 billion years old. Not that the species itself existed, but the behaviour may have spanned the aeons.

Fossil Phantom is Exposed

Animals appear as fossils c.570 million years ago, back in the Ediacaran, but there are trackways preserved in old mud going back nearly 2 billion years. The trackways look somewhat like worm-trails, but no worm has been identified in the fossils from then, or known specimen from the present, as a likely culprit. Now it seems a new suspect is on offer and it’s not an animal…

Grape is Key to Fossil Puzzle

Discovery Of Giant Roaming Deep Sea Protist

Single-celled giant upends early evolution

Deep-sea protists may explain trace fossils

Discovery of giant roaming deep sea protist

…a giant Protist, as big as a grape apparently, makes trails on the sea-floor just like the old fossil trails. This would neatly explain why “animal” trackways can appear in PreCambrian sediments from the PaleoProterozoic (2.5-1.6 Gya) and makes protists even more dynamic than anyone had previously imagined. Macroscopic colonies of microbes are well known as fossils – stromatolites can be gigantic, for example – but few had imagined mobile microbial colonies. Which is a bit sad since we Animals are effectively very large bacterial/Archeal colonies. Our mitochondria were once purple bacteria, while our centrioles and undulipodium were once bacteria related to spirochetes. And even now your body contains at least 10 times more bacterial than living animal cells. In a real way land animals are life-support suits for bacteria trying to live on land.