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)…

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