Other way around. Europe started HBP started first, then US announced the BI. The HBP is centered around Markham's big sim project. The BI is more like a bag of somewhat related grants, focusing more on connectome mapping. From what I remember, both projects are long term, and most of the results are expected to be 5 years out or so, but they are publishing along the way.

We are in a vast, seemingly-empty universe. Models which predict the universe should be full of life should be penalised with a lower likelihood.

The only models which we can rule out are those which predict the universe is full of life which leads to long lasting civs which expand physically, use lots of energy, and rearrange on stellar scales. That's an enormous number of conjunctions/assumptions about future civs. Models where the universe is full of life, but life leads to tech singularities which end physical expansion (transcension) perfectly predict our observations, as do models where civs die out, as do models where life/civs are rare, and so on. . ..

But this is all a bit off-topic now because we are ignoring the issue I was responding to: the evidence from the timing of the origin of life on earth

If we find that life arose instantly, that is evidence which we can update our models on, and leads to different likelihoods then finding that life took 2 billion years to evolve on earth. The latter indicates that abiogenesis is an extremely rare chemical event that requires a huge amount of random molecular computations. The former indicates - otherwise.

Imagine creating a bunch of huge simulations that generate universes, and exploring the parameter space until you get something that matches earth's history. The time taken for some evolutionary event reveals information about the rarity of that event.

"Anthropic selection bias" just filters out observations that aren't compatible with our evidence. The idea that "anthropic selection bias" somehow equalizes the probability of any models which explain the evidence is provably wrong. Just wrong. (There are legitimate uses of anthropic selection bias effects, but they come up in exotic scenarios such as simulations.)

If you start from the perspective of an ideal bayesian reasoner - ala Solomonoff, you only consider theories/models that are compatible with your observations anyway.

So there are models where abiogenesis is 'easy' (which is really too vague - so let's define that as a high transition probability per unit time, over a wide range of planetary parameters.)

There are also models where abiogenesis is 'hard' - low probability per unit time, and generally more 'sparse' over the range of planetary parameters.

By Baye's Rule, we have: P(H|E) = P(E|H)P(H) / P(E)

We are comparing two hypothesises, H1, and H2, so we can ignore P(E) - the prior of the evidence, and we have:

P(H1|E) )= P(E|H1) P(H1)

P(H2|E) )= P(E|H2) P(H2)

)= here means 'proportional'

Assume for argument's sake that the model priors are the same. The posterior then just depends on the likelihood - P(E|H1) - the probability of observing the evidence, given that the hypothesis is true.

By definition, the model which predicts abiogenesis is rare has a lower likelihood.

One way of thinking about this: Abiogenesis could be rare or common. There are entire sets of universes where it is rare, and entire sets of universes where it is common. Absent any other specific evidence, it is obviously more likely that we live in a universe where it is more common, as those regions of the multiverse have more total observers like us.

Now it could be that abiogenesis is rare, but reaching that conclusion would require integrating evidence from more than earth - enough to overcome the low initial probability of rarity.

I assume by 'algea-like', you actually mean cyanobacteria. The problem is that anything that uses photosynthesis creates oxygen, and oxygen eventually depletes the planet's chemical oxygen sinks, which inevitably leads to a Great Oxygenation Event. The latter provides a new powerful source of energy for life, which then leads to something like a cambrian explosion.

The largest uncertainty in these steps is the timeline for oxygenation to deplete the planet's oxygen sinks. This is basically the time it takes cyanobacteria to 'terraform' the planet. It took 200 million years on Earth, but this is presumably dependent on planetary chemical composition and size.

From the known exoplanets, we can already estimate there are on the order a billion-ish earth-size worlds in habitable zones. By the mediocrity principle, it's a priori unlikely that earth's chemistry is 1 in a billion. Especially given that Mar's composition is vaguely similar enough that it was probably an 'almost earth'.

We keep finding earlier and earlier fossil evidence for life on earth, which has finally shrunk the time window for abiogenesis on earth down to near zero.

The late heavy bombardment sterilized earth repeatedly until about 4.1 billion years ago, and our earliest fossil evidence for life is also now (probably) 4.1 billion years old. Thus life probably either evolved from inorganics near instantly, or more likely, it was already present in the comet/dust cloud from the earth's formation. (panspermia)

With panspermia, abiogenesis may be rare, but the effect is similar to abiogenesis being common.

I don't see why the usual infrared argument doesn't apply to them or KIC 8462852.

If by infrared argument, you refer to the idea that a dyson swarm should radiate in the infrared, this is probably wrong. This relies on the assumption that the alien civ operates at earth temp of 300K or so. As you reduce that temp down to 3K, the excess radiation diminishes to something indistinguishable to the CMB, so we can't detect large cold structures that way. For the reasons discussed earlier, non-zero operating temp would only be useful during initial construction phases, whereas near-zero temp is preferred in the long term. The fact that KIC 8462852 has no infrared excess makes it more interesting, not less.

A Dyson sphere helps with moving matter around, potentially with elemental conversion, and with cooling.

Moving matter - sure. But that would be a temporary use case, after which you'd no longer need that config, and you'd want to rearrange it back into a bunch of spherical dense computing planetoids.

potentially with elemental conversion

This is dubious. I mean in theory you could reflect/recapture star energy to increase temperature to potentially generate metals faster, but it seems to be a huge waste of mass for a small increase in cooking rate. You'd be giving up all of your higher intelligence by not using that mass for small compact cold compute centers.

If nothing else, if the ambient energy of the star is a big problem, you can use it to redirect the energy elsewhere away from your cold brains.

Yes, but that's just equivalent to shielding. That only requires redirecting the tiny volume of energy hitting the planetary surfaces. It doesn't require any large structures.

Exponential growth.

Exponential growth = transcend. Exponential growth will end unless you can overcome the speed of light, which requires exotic options like new universe creation or altering physics.

I think Sandberg's calculated you can build a Dyson sphere in a century, apropos of KIC 8462852's oddly gradual dimming. And you hardly need to finish it before you get any benefits.

Got a link? I found this FAQ, where he says:

Using self-replicating machinery the asteroid belt and minor moons could be converted into habitats in a few years, while disassembly of larger planets would take 10-1000 times longer (depending on how much energy and violence was used).

That's a lognormal dist over several decades to several millenia. A dimming time for KIC 8462852 in the range of centuries to a millenia is a near perfect (lognormal) dist overlap.

So it may be worth while investing some energy in collecting small useful stuff (asteroids) into larger, denser computational bodies. It may even be worth while moving stuff farther from the star, but the specifics really depend on a complex set of unknowns.

You say 'may', but that seems really likely.

The recent advances in metamaterial shielding stuff suggest that low temps could be reached even on earth without expensive cooling, so the case I made for moving stuff away from the star for cooling is diminished.

Collecting/rearranging asteroids, and rearranging rare elements of course still remain as viable use cases, but they do not require as much energy, and those energy demands are transient.

After all, what 'complex set of unknowns' will be so fine-tuned that the answer will, for all civilizations, be 0 rather than some astronomically large number?

Physics. It's the same for all civilizations, and their tech paths are all the same. Our uncertainty over those tech paths does not translate into a diversity in actual tech paths.

You cannot show that this resolves the Fermi paradox unless you make a solid case that cold brains will find harnessing solar systems' energy and matter totally useless!

There is no 'paradox'. Just a large high-D space of possibilities, and observation updates that constrain that space.

I never ever claimed that cold brains will "find harnessing solar systems' energy and matter totally useless", but I think you know that. The key question is what are their best uses for the energy/mass of a system, and what configs maximize those use cases.

I showed that reversible computing implies extremely low energy/mass ratios for optimal compute configs. This suggests that advanced civs in the timeframe 100 to 1000 years ahead of us will be mass-limited (specifically rare metal element limited) rather than energy limited, and would rather convert excess energy into mass rather than the converse.

Which gets me back to a major point: endgames. For reasons I outlined earlier, I think the transcend scenarios more likely. They have a higher initial prior, and are far more compatible with our current observations.

In the transcend scenarios, exponential growth just continues up until some point in the near future where exotic space-time manipulations - creating new universes or whatever - are the only remaining options for continued exponential growth. This leads to an exit for the civ, where from the outside perspective it either physically dies, disappears, or transitions to some final inert config. Some of those outcomes would be observable, some not. Mapping out all of those outcomes in detail and updating on our observations would be exhausting - a fun exercise for another day.

The key variable here is the timeframe from our level to the final end-state. That timeframe determines the entire utility/futility tradeoff for exploitation of matter in the system, based on ROI curves.

For example, why didn't we start converting all of the useful matter of earth into babbage-style mechanical computers in the 19th century? Why didn't we start converting all of the matter into vaccuum tube computers in the 50's? And so on....

In an exponentially growing civ like ours, you always have limited resources, and investing those resources in replicating your current designs (building more citizens/compute/machines whatever) always has complex opportunity cost tradeoffs. You also are expending resources advancing your tech - the designs themselves - and as such you never expend all of your resources on replicating current designs, partly because they are constantly being replaced, and partly because of the opportunity costs between advancing tech/knowledge vs expanding physical infrastructure.

So civs tend to expand physically at some rate over time. The key question is how long? If transcension typically follows 1,000 years after our current tech level, then you don't get much interstellar colonization bar a few probes, but you possibly get temporary dyson swarms. If it only takes 100 years, then civs are unlikely to even leave their home planet.

You only get colonization outcomes if transcension takes long enough, leading to colonization of nearby matter, which all then transcend roughly within the timeframe of their distance from the origin. Most of the nearby useful matter appears to be rogue planets, so colonization of stellar systems would take even longer, depending on how far down it is in the value chain.

And even in the non-transcend models (say the time to transcend is greater than millions of years), you can still get scenarios where the visible stars are not colonized much - if their value is really low, compared to abundant higher value cold dark matter (rogue planets, etc), colonization is slow/expensive, and the timescale spread over civ ages is low.

So your entire argument boils down to another person who thinks transcension is universally convergent and this is the solution to the Fermi paradox?

No . .. As I said above, even if transcension is possible, that doesn't preclude some expansion. You'd only get zero expansion if transcension is really easy/fast. On the convergence issue, we should expect that the main development outcomes are completely convergent. Transcension is instrumentally convergent - it helps any realistic goals.

I don't see what your reversible computing detour adds to the discussion, if you can't show that making only a few cold brains sans any sort of cosmic engineering is universally convergent.

The reversible computing stuff is important for modeling the structure of advanced civs. Even in transcension models, you need enormous computation - and everything you could do with new universe creation is entirely compute limited. Understanding the limits of computing is important for predicting what end-tech computation looks like for both transcend and expand models. (for example if end-tech optimal were energy limited, this predicts dyson spheres to harvest solar energy)

The temperatures implied by 10,000x energy density on earth preclude all life or any interesting computation.

I never said anything about using biology or leaving the Earth intact. I said quite the opposite.

Advanced computation doesn't happen at those temperatures, for the same basic reasons that advanced communication doesn't work for extremely large values of noise in SNR. I was trying to illustrate the connection between energy flow and temperature.

You need to show your work here. Why is it unlikely? Why don't they disassemble solar systems to build ever more cold brains? I keep asking this, and you keep avoiding it.

First let us consider the optimal compute configuration of a solar system without any large-scale re-positioning, and then we'll remove that constraint.

For any solid body (planet,moon,asteroid,etc), there is some optimal compute design given it's structural composition, internal temp, and incoming irradiance from the sun. Advanced compute tech doesn't require any significant energy - so being closer to the sun is not an advantage at all. You need to expend more energy on cooling (for example, it takes about 15 kilowatts to cool a single current chip from earth temp to low temps, although there have been some recent breakthroughs in passive metamaterial shielding that could change that picture). So you just use/waste that extra energy cooling the best you can.

So, now consider moving the matter around. What would be the point of building a dyson sphere? You don't need more energy. You need more metal mass, lower temperatures and smaller size. A dyson sphere doesn't help with any of that.

Basically we can rule out config changes for the metal/rocky mass (useful for compute) that: 1.) increase temperature 2.) increase size

The gradient of improvement is all in the opposite direction: decreasing temperature and size (with tradeoffs of course).

So it may be worth while investing some energy in collecting small useful stuff (asteroids) into larger, denser computational bodies. It may even be worth while moving stuff farther from the star, but the specifics really depend on a complex set of unknowns.

One of the big unknowns of course being the timescale, which depends on the transcend issue.

Now for the star itself, it has most of the mass, but that mass is not really accessible, and most of it is in low value elements - we want more metals. It could be that the best use of that matter is to simply continue cooking it in the stellar furnace to produce more metals - as there is no other way, as far as i know.

But doing anything with the star would probably take a very long amount of time, so it's only relevant in non-transcendent models.

In terms of predicted observations, in most of these models there are few if any large structures, but individual planetary bodies will probably be altered from their natural distributions. Some possible observables: lower than expected temperatures, unusual chemical distributions, and possibly higher than expected quantities/volumes of ejected bodies.

Some caveats: I don't really have much of an idea of the energy costs of new universe creation, which is important for the transcend case. That probably is not a reversible op, and so it may be a motivation for harvesting solar energy.

There's also KIC 8462852 of course. If we assume that it is a dyson swarm like object, we can estimate a rough model for civs in the galaxy. KIC 8462852 has been dimming for at least a century. It could represent the endphase of a tech civ, approaching it's final transcend state. Say that takes around 1,000 years (vaguely estimating from the 100 years of data we have).

This dimming star is one out of perhaps 10 million nearby stars we have observed in this way. Say 1 in 10 systems will ever develop life, the timescale spread or deviation is about a billion years - then we should expect to observe about 1 in 10 million endphase dimming stars, given that phase lasts only 1,000 years. This would of course predict a large number of endstate stars, but given that we just barely detected KIC 8462852 because it was dimming, we probably can't yet detect stars that already dimmed and then stabilized long ago.