Roko's Basilisk in the Form of a Metal Song

When Metallica writes a song about the singularity, it's probably close. "Stop breathing, and dedicate to me - stop dreaming, and terminate for me."

Prediction: Venusian Phosphine is a Metabolic Product of Living Cells Already Detected As Unknown Absorbers

The last two years have provided us with the strongest evidence ever assembled of extraterrestrial life:

1. Prior theories about relic ecosystems surviving in the more Earth-like parts of Venus's atmosphere.
2. Detection of UV absorbers the size of bacteria in Venus's atmosphere, with no explanation as to their identity.
3. Prior, independent advancement of phosphine as a biosignature gas.
4. Detection of phosphine in the Venusian cloud decks with no explanation for its persistence.

Here I propose that Venus had an iron-sulfur ecosystem with a chlorophyll-equivalent that absorbs closer to the UV spectrum rather than visible light - essentially, "UV-synthetic" Venusian cyanobacteria. The oceans boiled away and Venus became hotter and more acidic from volcanism and possibly, their own Great Sulfuration (or Sulfur Oxidation, equivalent to Earth's Great Oxygenation.) The only survivors were the UV-synthetic Venusian archaebacteria that now live in the upper atmosphere. Today these have a life cycle like that described by Seager et al (2020), powered by UV and producing phosphine - Unknown Absorber Phosphine Producers (UAPPs.) They are likely related at great time depths to life on Earth. Initial research question is to see if areas of unknown absorbers correlates with phosphine, which can be done from Earth. Probes that collect material in the upper atmosphere could fairly straightforwardly check for aspects of biochemistry using an onboard instrument, and a sample return mission could be extremely productive.


Phosphine Production in the Clouds of Venus

If you're reading this you likely know that phosphine (PH3) was detected in the atmosphere of Venus - Vox explainer here; original paper by Greaves et al here. The measured concentrations are at biology-consistent levels, at an elevation where the pressure and temperature are similar to Earth's. This is by far the strongest evidence of extraterrestrial life yet discovered, with evidence from multiple sources.

Phosphine has been advanced as a possible seed compound delivered to Earth on comets or asteroids early in its history. But the chemistry of its formation in space (or on gas giants) is not mysterious. It's in the Venusian atmosphere where so far we can't explain its presence without some process that continuously replenishes it. One criticism of speculation about possible Venusian biochemistry is that just because we don't know how to make phosphine under Venusian conditions, doesn't mean we're looking at alien biology. True; but among these criticisms have not been any suggestions so far about what it might be. (Either way, we're about to learn something.) It's suggestive that this data is not completely unexpected - it can be fitted to prior hypotheses. We've been speculating more and more concretely for decades about how life might survive in the atmosphere of Venus for decades (see Morowitz and Sagan 1967.) A fairly elaborated model of microbial life in the atmosphere of Venus was advanced recently by Seager et al, consistent with observations so far. This should also increase our confidence in the Venusian-cloud-life hypothesis, that even before phosphine was detected, Sousa-Silva et al suggested phosphine as a biosignature molecule, independent of finding it on Venus.


A Related Mystery? The Unknown Absorbers



In visible light and false-color UV absorption. It's unusual to have such contrast in absorption at different wavelengths. Image credit syfy.com

For decades we have known that there are partciles about 10^-6 meters (the size of bacteria) in the Venusian atmosphere at a similar altitude (at 47 to 64km) as the phosphine detection above (at 57km and above). The dark bands we can see with the naked eye in the Venusian atmosphere contain more of them, but as you can see above in the UV image, they are much higher contrast (more absorbant). As with the origin of Venusian phosphine, the identity of the absorbers remains controversial, and Venusian biology had been advanced previously as a candidate explanation (Limaye et al 2018). The phosophine paper points out that there is more phosphine at mid-latitudes than the equator or poles, which by naked-eye examination of images of Venus, seems also to be where the absorbers are. It seems a relatively straightforward study to correlate the two, but as the absorbers move on a scale from minutes to days, data would have to be collected simultaneously. The stronger the correlation (especially within the same latitude) the more our confidence in the UAPP hypothesis of Venus cloud life would be increased.


What About Bacterial Life in Earth's Cloud Decks?

Earth's clouds do indeed contain lots of bacteria, and not just incidentally - some of them clearly evolved to take advantage of the precipitation cycle and indeed to deliberately cause ice to enucleate around it, like Pseudomonas syringae (this is actually economically relevant as the water ice-enucleation proteins produced by this species is used in the water fed into snow guns at ski resorts.) Bacteria have been found all the way up to 28 miles above the surface, where the pressure and temperature are both much lower and considerably less hospitable even to Earth's own life than the cloud decks on Venus. While we can't say there is an actual bacterial ecosystem in Earth's clouds (one which persists without interacting with the surface), we haven't really looked for one either; most of our interest in these organisms thusfar comes from studying plant pathogens that spread through weather events. It's worth pointing out that there is phosphine in Earth's upper atmosphere as well, with no clear mechanism for how it forms there. It should be noted that there is less in Earth's upper atmosphere by about 3 orders of magnitude; the levels in Venus's atmosphere are more similar to that found immediately around actively metabolizing bacteria on Earth's surface.


Toward an Evolutionary History of Venus

Why would life exist on the most hellish world in the solar system? The answer is that for at least 75% of its lifespan, Venus was a much more Earth-like planet with cooler temperatures and oceans.

There are two possible, not mutually exclusive stories that explain how this planet came to be the Venus we know today.

The first is that Venus was a little too close to the Sun, which caused its oceans to evaporate, plate tectonics to cease, and subsequent cataclysmic volcanism. As the oceans evaporated, the water vapor trapped the heat and accelerated the process. The deuterium/hydrogen ratio on Venus is about 150 times higher than Earth, where comets have at most a 3 times higher ratio than Earth, suggesting a very gradual loss to space of hydrogen from water and preferential retention of the heavier nucleus. Water lubricates plate tectonics, per Solomatov 2001. Climate modeling suggests that Venus may have had a habitable climate with liquid water at the surface until 715 MA ago (Way et al 2016.) The subsequenct evaporation of the oceans resulted in a planet where plate tectonics ground to a halt, and with no crustal mechanism to dissipate heat, and finally between 700 and 500 MA ago, Venus erupted in planet-wide massive flows that resurfaced the planet, utterly dwarfing any similar events on Earth (like the Siberian Traps.) This released the massive amounts of sulfur that we see today. This is the received wisdom and could entirely explain the modern state of Venus, and may alone be enough to explain all the sulfur.

There is another version of the story which reverses the causality - eruption causing evaporation, advanced by Way and Del Genio in 2019. It's worth noting that Venus has a thicker crust than Earth, owing to its lack of a large moon; therefore we should expect that the flows, when they do finally cause the crust to fail, are much stronger than in the parallel situation on an evaporated Earth.

The second possibility is obviously more speculative, a parallel to the Great Oxygenation in the history of life on Earth. In Earth's history, anaerobic cyanobacteria produced so much oxygen that they effectively poisoned themselves, but also set the stage for aerobic life. This could have been a great coincidence - there may just have happened to be genes close enough in design space to assemble oxyidation defenses and an aerobic metabolic pathway, and without such a coincidence, that may have been the end of life on Earth, or it may have settled into a simple bloom-and-bust oscillation as our bacterial mats may have for hundreds of millions of years evidenced by banded iron formations found in ancient rocks where they persist at the surface. (See discussion of endogenous extinctions here, which this section partly recapitulates.)

While an interesting idea, by Occam's razor we should spend no further time considering a possible Great Sulfuration, as we can explain the death of the Venusian surface ecosystem entirely based on abiotic meteorological and geological processes as above. It's also the case that the presence of increased CO2 relative to Earth can be easily explained by abiotic processes as well. Using ingenious reasoning about the necessary atmospheric pressure for flying dinosaurs' wings to function as well as the known rates of deposition of CO2 as carbon in continents and the ocean, we can arrive a figure of the equivalent of 85-100 bars' worth of CO2 trapped in the Earth's crust, similar to what is currently in the Venusian atmosphere. Presumably the atmospheric pressure of Venus was lower during its oceanic period owing to the same process, and rose subsequent to the evaporation, but I am not aware of any modeling retrodicting from oceanic evaporation 500-700 MA ago to the current pressure and mass of CO2 on Venus.

All this is to say that life on Venus may have gone a different way, but started quite similarly. We're now fairly confident the first metabolism on Earth was sea vent iron sulfur organisms, using sulfur in what is now oxygen's chemical role. The Great Oxygenation may have only happened when it did, a full 1.5 billion years after the first life and at least 800 million years after photosynthesis appeared, because an asteroid delivered molybdenum, allowing nitrogen fixation and more efficient anaerobic metabolism. Whatever the reason, had this happened prior to photosynthesis, we may have ended up with an Earth poisoned with sulfur or at least with a massive amount of oxidized sulfur.


Two Obvious Problems for the "UAPP Cells" Hypothesis for Life on Venus

There are two major hurdles to overcome in any argument that there is life in the cloudtops of Venus. The first is the question of how life operates without water, or with very little water; this would actually be a more stunning find than merely life which can tolerate high acidity! The second is the failure thusfar to detect any organics in the atmosphere. Without water and organic molecules, it's very hard to see how this won't end up being an interesting abiotic route to phosphine production along with some crystal we weren't anticipating at that altitude. That said, organic compounds on Venus may not be as unlikely as one might think - there was a Venusian equivalent of the Miller-Urey experiment performed, where under conditions of the Venusian atmosphere, organic compounds including amino acids were produced.

Furthermore, there remain arguments for an abiotic explanation for the unknown absorbers, specifically ferric chloride (Petrova 2018). Interestingly, this is partly advanced to explain another mystery which is the presence of rainbows ("Venus glory"), first observed in 2014 in the Venusian atmosphere.


Implications for Evolution in General and the Future of Life of Earth

It is more likely than not that life on Venus will be distantly related to life on Earth. A massive amount of material has been transferred between bodies in the solar system, with actual numbers calculated here; at that same link you will see reference to the survival of uncontrolled re-entry during the Columbia crash by not just bacteria, but animals (C. elegans worms, found alive on the ground weeks after the crash.) This is actually the more boring possibility, because we would learn much more about the basic principles of evolution and the possibilities of biochemistry beyond Earth's provincial commitments, if we really had a novel origin. Either way, if there is life on Venus, the likelihood of life on Mars, Europa, Enceladus and even Titan jumps dramatically, even if it's "just" a long-lost relative. I expect that ultimately the impact of finding life on Venus will be some neat new biochemistry (the old extremophiles will seem quaint) and a bit more information about how evolution can proceed.

It is unclear how we should feel about Venusian cloud UV-cyanobacteria in terms of the Great Filter, which suggests that the more life we find in the universe and the closer in terms of evolutionary stage to humans, the more concerned we should be - because the more likely our own extinction is before we can colonize planets beyond our own. If further exploration of Venus yields trilobites or vertebrates and these cells are all that are left, we should worry much more. In contrast, if Venus never got past vast floating bacterial mats (either in its clouds or ancient oceans). that's a bit more comfortable for us.


REFERENCES

Bains W, Petkowski J, Sousa-Silva C, Seager S. Trivalent phosphorus and phosphines as components of biochemistry in anoxic environments. Astrobiology 19, 7 (July 2019): p. 885-902 doi 10.1089/AST.2018.1958

Glindemann D, Edward M, Kuschk P. Phosphine gas in the upper troposphere. Atmospheric Environment Volume 37, Issue 18, June 2003, Pages 2429-2433

Greaves JS, Richards AMS, Bains W, Rimmer PB, Sagawa H, Clements DL, Seager S, Petkowski JJ, Sousa-Silva C, Ranjan S, Drabek-Maunder E, Fraser HJ, Cartwright A, Mueller-Wodarg I, Zhan Z, Friberg P, Coulson I, Lee E, Hoge J. Phosphine gas in the cloud decks of Venus. Published: 14 September 2020. Nature Astronomy (2020)

Levenspiel O, Fitzgerald TJ, Pettit D. Was the Atmospheric Pressure Different at the Time of Dinosaurs? Chemical Innovation, December 2000 Vol 30, No.12, 50 – 55

Limaye SS, Mogul R, Smith DJ, Ansari AH, Słowik GP, Vaishampayan P. Venus' Spectral Signatures and the Potential for Life in the Clouds. Astrobiology. 2018 Sep 1; 18(9): 1181–1198. Published online 2018 Sep 12. doi: 10.1089/ast.2017.1783

Morowitz H & Sagan C. Life in the Clouds of Venus? Nature volume 215, pages1259–1260(1967). 16 September 1967.

Otroshchenko V.A., Surkov Y.A. (1974) The Possibility of Organic Molecule Formation in the Venus Atmosphere. In: Oró J., Miller S.L., Ponnamperuma C., Young R.S. (eds) Cosmochemical Evolution and the Origins of Life. Springer, Dordrecht. https://doi.org/10.1007/978-94-010-2239-2_40

Petrova EV. Glory on Venus and selection among the unknown UV absorbers. Icarus Volume 306, 15 May 2018, Pages 163-170

Seager S, Petkowski JJ, Gao P, Bains W, Bryan NC, Ranjan S, Greaves J. The Venusian Lower Atmosphere Haze as a Depot for Desiccated Microbial Life: A Proposed Life Cycle for Persistence of the Venusian Aerial Biosphere. Astrobiology. Published Online:13 Aug 2020. https://doi.org/10.1089/ast.2020.2244

Sousa-Silva C, Seager S, Ranjan S, Petkowski JJ, Zhan Z, Hu R, Bains W. Phosphine as a Biosignature Gas in Exoplanet Atmospheres. AstrobiologyVol. 20, No. 2. Published Online:31 Jan 2020 https://doi.org/10.1089/ast.2018.1954

Way MJ, Del Genio AD, Kiang NY, Sohl LE, Grinspoon DH, Aleinov I, Kelley M, Clune T. Was Venus the First Habitable World of our Solar System? Geophysical Research Letters. First published: 11 August 2016 https://doi.org/10.1002/2016GL069790

All Attempts to Broadcast Our Presence to Nearby Stars Should Be Forbidden

Here you can find a list of when there might be a response to known prior contact attempts within a century, assuming immediate light-speed response, and whether there are known terrestrial planets around the stars. This is incredibly dangerous and reveals the presence of intelligence on Earth to anything that might be listening, and should be immediately stopped (see Stephen Hawking's take on this here.) Granted, astronomers' definition of habitable - "terrestrial planet orbiting in liquid water temperature zone" - leaves a lot to be desired.

Until now. Measurements of terrestrial planets can now show if there is an atmosphere and it contains hydrogen, oxygen, and N2, making at least some water quite likely (Konatham et al 2020.)

We can update the list of stars where we've already broadcast contact attempts, with these new stricter criteria. There are two planets with atmospheres and likely water that we have deliberately broadcast to: Teegarden's Star, a red dwarf (with two planets with likely water), with a response possible by 2036; and GJ273b (Luyten's Star), with a super Earth with likely water, responding at earliest 2043.

Two facts to modify our enthusiasm:

• Both are red dwarfs, which have a habit of flaring. However, Luyten's Star is quiet by these standards.
• Also, aliens looking at our solar system using the same definition would keep both Mars and Venus on this stricter habitable list. Both do have atmospheres and some water.

Proxima Centauri is the closest star but in this more-strict list of habitable planets, but we haven't deliberately targeted it. It's worth pointing out that even if there were a twin Earth there, we still wouldn't be able to hear them (the C-index - a rule of thumb, assuming that strength of a civilization's emissions and ability to detect increase in concert.)

(Encouraging to amateurs: Teegarden's Star was discovered by a group of non-professional astronomers poring over data online, without access to telescopes.)

Konatham S, Martin-Torres J, Zorzano M. Atmospheric composition of exoplanets based on the thermal escape of gases and implications for habitability. Published:09 September 2020https://doi.org/10.1098/rspa.2020.0148

Unexpected Ejection of Material from Asteroid Bennu

Of obvious interest to any panspermia hypotheses, especially those which favor replicators (Von Neumann probes or otherwise) using organics on low-gravity bodies as building blocks. Paper here. Abstract:

In early 2019, the OSIRIS‐REx spacecraft discovered small particles being ejected from the surface of the near‐Earth asteroid Bennu.sww Although they were seen to be ejected at slow speeds, on the order of tens of cm/s, a number of particles were surprisingly seen to orbit for multiple revolutions and days, which requires a dynamical mechanism to quickly and substantially modify the orbit to prevent re‐impact upon their first periapse passage. This paper demonstrates that, based on simulations constrained by the conditions of the observed events, the combined effects of gravity, solar radiation pressure, and thermal radiation pressure from Bennu can produce many sustained orbits for ejected particles. Furthermore, the simulated populations exhibit two interesting phenomena that could play an important role in the geophysical evolution of bodies such as Bennu. First, small particles (less than 1 cm radius) are preferentially removed from the system, which could lead to a deficit of such particles on the surface. Second, re‐impacting particles preferentially land near or on the equatorial bulge of Bennu. Over time, this can lead to crater in‐filling and growth of the equatorial radius without requiring landslides.

McMahon JW, Scheeres DJ, Chesley SR, French A, Brack D, Farnocchia D, Takahashi Y, Rozitis B, Tricarico P, Mazarico E, Bierhaus B, Emery JP, Hergenrother CW, Lauretta DS. JGR Planets. Dynamical Evolution of Simulated Particles Ejected From Asteroid Bennu. First published: 18 May 2020 https://doi.org/10.1029/2019JE006229

San Francisco 2020 With Blade Runner 2049 Score

H/T Mr. Black

New Approaches on What the Fermi Paradox Means for the Future of Humanity

I was lucky to attend a video lecture by James Miller, economist at Smith College, facilitated by Joshua Fox. Thanks for having this event! I contacted James to let him know I would be posting this and to let him proofread my recapitulation of his argument so as to avoid mis-paraphrasing him; my thanks to him for taking the time to correct me on several points. Of course any errors are mine.

Much of this is familiar terrain for those of us who spend our time considering X-risk and the Fermi paradox. Miller's thesis is that we are at a critically important point in human history, a window where we think that in the near future we can start colonizing the galaxy (the year 2614 at earliest, by this calculation) but at the same time where we are smart enough to destroy ourselves. Since it is not obvious that the galaxy has already been colonized by other civilizations, there may be a Great Filter stopping this from happening. Miller uses the analogy of a person about to climb a mountain, believing that everyone else who has attempted it has died in the process.

Several challenges were discussed by attendees. (If you attended the lecture and want to claim credit for your question, please comment below, thanks.)

1. It's too early to say there are no civilizations; it may not be so easy to detect them or rule them out. We're still discovering metazoans in Manhattan so it seems a little early to rule out von Neumann probes on low gravity bodies in the solar system. We've barely begun to catalog the fauna of our own ocean floors. We could not detect a twin Earth emitting the same radio energy (the C-index), even if it was orbiting Alpha Centauri. Miller points out that even if there were only a few civilizations in the Milky Way preceding us, "the galaxy is older than it is big", and these earlier civilizations could have colonized it already.
   
   
2. He made the point that the things which prove advantageous in the midst of evolving on a single planet might have no such advantages in terms of galactic colonization. Very true; I would argue that we are much more likely to find alien artifacts, than the aliens themselves, as all of us meat-creatures might be stuck on our planets while our machines colonize the galaxy. To that end, (my point) it's entirely plausible that the Solar System could be littered with space probes and we haven't found any yet, or did, and just didn't know what we were looking at.
   
   
3. I would therefore extend Miller's analogy like this. Only in the process of climbing the mountain, does our climber develop wilderness skills and begin to see things that resemble his own boot tracks, etc. and finally as he approaches the summit realizes that lots of people have climbed it, come down the other side, and their descendants have built large villages which due to his previous ignorance he has not been able to locate. (Or, maybe just some of their livestock, trained birds-of-prey, etc. have made it.)
   
   
4. Active attempts to bring ourselves to the attention of aliens have occurred (METI) and been roundly criticized. Miller notes that the risk of extinction from aliens over the next few centuries is lower than eg bio-terrorism or an intelligence singularity. True; but we still may be making life more difficult for our descendants. Related to this, he proposes an ingenious experiment that for a month we should shout our heads off electromagnetically, and see if there is any strange activity. While I agree it's unlikely we'll get invaded next week, I still think the risk:benefit does not work out and there are just too many unknowns, and we may be screwing our distant descendants. Miller suggested that enforcing a moratorium on METI-like activities is probably impossible.
   
   
5. He argues that technological singularities of the paperclip maximizer variety are unlikely to be a major contributor to the Great Filter, because we would be able to see the boundary of it as it expanded (unless it was doing so at light speed.) My concern with this is that, while an AGI might be much smarter than its creators, it is still not omniscient, and the impact of its actions could in principle still outstrip its ability to predict that impact. This is the story behind the rise of human intelligence and the sixth great extinction that we're living through, but has happened in pulses of endogenous extinctions throughout Earth's history (the rise of superpredators every fifty million years or so, the Oxygen Catastrophe). The lesson of evolution here on Earth is that the smarter things are, the faster their behavioral plasticity "catches up with them" in exactly these sorts of disasters, so to suppose that alien paperclip maximizers are immune to this problem is to argue that a qualitative change in ecological dynamics has occurred.
   
   
6. There were two (possibly unappreciated) related questions asked: one about civilization perhaps being bad for sustaining civilization (witness declining birth rates in the developed world) and another that intelligences might prefer virtual reality - involution - to expanding into space. Miller points out the passive version of the "baseball bat" problem: you can live in heaven, but if a bad guy comes and bashes your server with a club and you as you sleep in your VR pod, that's the end of it. (Related: dynamic complex systems like minds, in principle, tend to drift toward delusion and suffer inherent cyclic crises.) It's a thesis for someone in psychology or a related field to note whether there is causation or just correlation between the increasingly encompassing virtual reality-like entertainments available in the developing world, and declining birth rates.
   
   
7. One questioner asked about the distinction between intelligence and civilization - humans have had a "civilization" only since agriculture. This was a really original line of thought. Therefore, there could be many alien intelligences, but few or no civilizations. One solution for humans avoiding the Great Filter would be to abandon civilization and go back to hunting-gathering - not directly suggested, but this is the only implication of such an argument I could think of. The extreme number of assumptions built in to discussion of alien civilizations should always be pointed out - civilization is something that collections of human nervous systems do, and it is not clear it is a necessary consequence of intelligence. (As a physician I ask: do we assume the aliens will have similar EKG waveforms and liver enzymes as us? No, because that's ridiculous. So we do we assume that the even more complex activity of another organ, that we don't even share with other animals on this planet, is automatically going to be meaningfully similar?)

There's also a psychological point to be made about "big picture" arguments (the singularity, the Fermi paradox, the simulation argument, etc.) They have a tendency to converge on either prophetic religion-like conclusions (e.g. the singularity as the rapture for nerds) or Lovecraft (the estivation hypothesis, which was mentioned in a question and made me think about this.) When we talk about these things, there are many many unknowns. In such discussions, I think there is a tendency for the resulting arguments to resemble the internal contours of the human mind, more than any future events in the actual external world; hence their regression to religion-like conclusions. This does not mean such an argument must be incorrect, but it should make us suspicious when a big-picture argument hews too close to our "ontological test pattern. "

Consider in contrast cosmologists' models of the distant future of the universe, which concern physical objects which we can now observe and characterize, using rigorous mathematical rules. These models often seem boring, meaningless, difficult to understand, and unsatisfying. This is exactly how we should expect most models will seem of things outside our own and our ancestors' experiences, or beyond the scale of time and space to which we are accustomed and which we are built to perceive; the further outside their experience, the moreso. This occurred to me when we were discussing the estivation hypothesis, though overall Miller's arguments do not set off many alarm bells for this quick-and-very-dirty heuristic.

Lazerhawk - Redline, 2013

Origin of Life in RNA Computing: Independent Suggestion of Organic von Neumann Probes

Previously I had advanced the idea that, if intelligence has arisen elsewhere in the galaxy, it is likely to have colonized the galaxy in some form, and therefore we are more likely to find their artifacts here in our solar system than hear or understand their EM signals.  Specifically I argue that von Neumann probes are more likely to be entities of organic chemistry we find on low gravity bodies, that as natural selection is universal law that such entities - even if dispatched to gather information - would eventually be selected for fecundity; that is, they would inevitably become cancerous.  If the water that seeded the early Earth contained such entities, whether or not they were intact, the tumor detritis of these cancerous von Neumann probes would provide the template for life on ancient Earth.  

We have not nearly approached the amount of solar system exploration, or elaborated an abstract theory of how to recognize life or its artifacts, to be able to say we have absence of evidence.  Indeed we find nucleobases on asteroids, though so far we have no evidence so far that they originated from processes beyond the natural ones we are aware of.  

In a new paper, Hessameddin Akhlaghpour makes the observation that while the RNA information processing behavior of life on Earth is not Turing complete, with some additional (not implausible) molecular machinery, it would be.  He then argues that life originated with such a molecular machine and we have not yet found it.  (H/T Marginal Revolution)

Akhlaghpour H.  A Theory of Natural Universal Computation Through RNA.  arXiv:2008.08814

Evergreen - Eye in the Sky (2018) (Cover of Alan Parsons Project Song from Eponymous Album, 1982)

Here's the original for comparison. It's interesting how many really well put-together songs tolerate export to other genres, and others which just fail (as in an otherwise great band covering themselves here.)



And while we're at the game of metal versions of 80s songs, just for fun here's Leo Moracchioli featuring Rabea and Hannah.

The Earth Has Not Been Disassembled for Computation - Percent Utilization of Phosphorus and Nitrogen on Earth by Living Things

A 2015 paper by Landenmark et al estimates the total number of DNA bases in nature as 5.3x10^31 megabases. This of course leads to questions like: how much of the elements on Earth is life on Earth using? I'm aiming for an answer within an order of magnitude. This has implications for concerns about AI takeoff that I will return to at the end.


NITROGEN

Living things occupy slightly more than a billionth of the planet's nitrogen in our DNA (0.000000115%). Living things occupy 0.0023% of the planet's nitrogen overall, the lion's share of which of course is in protein. (See my assumptions below if you like.)


PHOSPHORUS

Living things are using only 0.00047% of the planet's phosphorus in our DNA - but that expands to 4.7% of the planet's phosphorus in living cells overall. This is a much more significant fraction.


Does this difference exist because life on Earth has chosen phosphorus as, effectively, energy currency to manipulate gradients? Or because nitrogen is harder to make biologically available? Even now we rely on relatively few bottlenecks to fix it.



IMPLICATIONS FOR AI TAKEOFF

There's no reason to assume that these numbers represent a global, rather than local optimum for resource utilization for replicators on Earth. That said, we've had four billion years to optimize. This is relevant because of the concern that AI taking off without regard to human welfare would disassemble the Earth into atoms for computation - the farther we are from truly optimized resource utilization, the more an intelligence explosion would be disruptive to the status quo. I found the Bar-On paper on amount of DNA in the biosphere from a link in a discussion about the computational efficiency of nucleic acids in cells. The latter paper suggests that protein translation is several orders of magnitude faster than the fastest current computers, and only an order of magnitude under the Laundauer limit. Of course, resource utilization and computing speed are two different variables, but it seems computation is getting near optimized already - and yet, no disassembly of the Earth for phosphorus. Not even 5% of the energy currency atoms are put to work! Of course, an AI would be qualitatively and quantitatively different in unpredictable ways from what came before, in which case there is no point in discussing this - but the replicators that exist in reality make the best starting point for such a discussiong.

What's more, protein translation is computation in the service of replication. It is quite likely that AIs would end up being selected in much the same way as cells have, with limited resources to be dedicated to refining the model of the universe (getting smarter.) The ivory tower AI super-minds would be dominated by the silicon bacteria. Of course, this is still no reason to think a hard AI takeoff could be disastrous for all life on Earth, an extinction like we've never seen - which the AIs themselves might not have the foresight to survive - but if they do, the best bet is that they will "revert to the mean" of all replicators, with making copies as the goal.




An imperfect analogy. In nature, you have to make do with what's there. The shapes aren't friendly for efficient packing and there are a lot more holes.

Assumptions:

I could not find estimates of the overall mass of nitrogen and phosphorus in the biosphere, so I used the percentage weights in living cells, and derived from a paper estimating the mass of carbon in the biosphere at 5.5x10^14 kg (Bar-On et al 2018), along with carbon being 18% of the atoms in living things.

For both I used 2884.6 kg/m^3 mass of the Earth's crust (weighted the differently dense continental and oceanic crusts at 0.3 and 0.7 resp.) My number for nitrogen comes from nitrogen in the atmosphere, plus nitrogen in the top meter of the Earth's crust, estimating mass of the atmosphere as 5.15*10^18 kg, of which 78.09% is nitrogen, and abundance in the crust as 0.002% by mass (there was some conflict over this between sources actually of up to an order of magnitude; but there is so little nitrogen in the crust compared to the atmosphere, about 347,000 times less using this number, that it's still a rounding error. I assume that there are an equal number of A T C and G which means 3.75xnitrogen atoms per base.

For phosphorus, I used a crustal abundance of 0.1% mass, ignoring the negligible phosphorus in the atmosphere. There is 1xphosphorus atom per base. The major "slop" in this figure occurs because different organisms have different fractions of phosphorus, for one thing since phosphorus is used in structural molecules like bone (85% of phosphorus in humans is in bone; even the same organism at different ages differs substantially, e.g. 0.5% in infants, close to 1% in adults.) Bacteria come in at 0.9% (3% dry weight, assuming 70% water mass per cell) so I used that figure, since bacteria outweigh us by a factor of a thousand, and the number is intermediate even for the values for vertebrates.


REFERENCES

Bar-On YM, Phillips R, Milo R. The biomass distribution on Earth. PNAS June 19, 2018 115 (25) 6506-6511.

P. Kempes CP, Wolpert D, Cohen Z, Pérez-Mercader J. The thermodynamic efficiency of computations made in cells across the range of life. Philos Trans A Math Phys Eng Sci. 2017 Dec 28; 375(2109): 20160343.

Landenmark HKE, Forgan DH, Cockell CS. An Estimate of the Total DNA in the Biosphere. PLoS Biol. 2015 Jun; 13(6): e1002168. Published online 2015 Jun 11. doi: 10.1371/journal.pbio.1002168

Michael Schirber. Chemistry of Life: The Human Body. Livescience.com. https://www.livescience.com/3505-chemistry-life-human-body.html#:~:text=Oxygen%20(65%25)%20and%20hydrogen,%25)%20is%20synonymous%20with%20life.

New Estimate for Number of Active Civilizations in the Milky Way

A summary:

• At a lower bound, it's estimated on average there is one 17,000 LY away. The number that is being reported is that this means at least 36 civilizations in the galaxy.
  
  
• They mention the problem of relying on M-class stars as abodes for life - because they're quite unstable (flares). I have not read the paper in detail, but it seems hard to understand, if there are only 36 star systems, why those couldn't all be G-class stars.
  
  
• They also estimate a lower bound of communicating for only a century (since we've been communicating for that long so we know it's possible.) If it's only a 100 year period, if we're hearing them now, they were active before agriculture.
  
  
• There's also the problem of being able to discern signal from noise at that distance - and not knowing what type of signal we're looking for. A useful thought experiment is the C-index, which is the distance at which we could detect a twin Earth with identical EM emissions. By most estimates, even if there were a twin Earth orbiting Alpha Centauri, we still today could not hear them. This leads the authors to conclude that interstellar communication is for all intents and purposes impossible.
  
  
• Therefore, any persisting civilization is plausibly more likely to be detected by self-replicating artifacts. This all reinforces the greater relative importance of looking for artifacts in our own solar system, which is something we can conceivably do with known technology in the near future, with less of a signal-to-noise problem.
  

Westby T. and Conselice CJ. The Astrobiological Copernican Weak and Strong Limits for Intelligent Life. The Astrophysical Journal. 2020 June 15.

The Asimov Library, and the Idea Catalog

Hat tip Marginal Revolution for both of these.

1. the nucleus of it is starting with this man, who as a labor of love is collecting/cataloging all of Asimov's work. Thank you Steven Cooper!
   
   
2. Catalog of science fiction ideas by year appearing - I've linked to the nineteenth century.

Review: Ad Astra

Initially I was excited to see this, not sure why it got so little fanfare, and now I know. Critics were surprisingly positive. I notice that any time Brad Pitt is in something, they give the film as a whole an inflated grade, even if he turns in consistently good performances. I can see why critics get a warm glow from his projects - he's a good actor, he's good-looking, he's a nice guy and he takes his profession seriously. But that can't save everything, and a movie with him, Donald Sutherland and Tommy Lee Jones that isn't a home run strongly suggests there's a problem with the script.

And there is. This is a movie that can't make up its mind. Are we a near-future hopeful thriller, or a nostalgia film, or a dark reflection on the qualitative differences of the new frontier and whether humans are up to the challenge. (It is possible to be all three, but this film ended up with a few confused moments of each and executed on none of these themes.) Do we want to be a plot coupon-collecting adventure, or a psychological exploration? (It's hard to tell which was central in the writers' minds, and which was added to support the other, because both are so unsatisfying.) The reasons many scenes take place are thin and barely coherent.

Keep in mind SPOILER ALERT I only watched to the part where he contacts his father from Mars, and read about the rest of it online to avoid investing another hour of my life in it.

1. The most realistic portrayal of space travel in film? That's a serious assertion made by the creators of this? 73 days to Neptune and a week or so to Mars...come on. Very little in the way of considering automation. It seems like they took the aesthetic of the Apollo era and extended it to the late 21st century, except the rockets were magically faster.
   
   
2. Action sequences are overall, again, crow-barred in as well, to keep it interesting. The only one that seemed interesting was the fall from the exploding antenna at the beginning. Reminds you of the drop onto Vulcan in the first Star Trek reboot-meets-Baumgartner and Kittinger.
   
   
3. The journey across the Moon is where it really started to lose me. Why again do they not just land there initially, or failing that, at least take a rocket? Oh yeah, the Moon pirates. Surviving on the Moon takes a massive amount of infrastructure. So where are these Moon pirates hiding out that they're undetected, and how do their supplies get to them without detection? Within minutes of their appearance they're wiped out from over-the-horizon artillery, so it's hard to explain how a major operation like a Moon-base could get very far. Apparently it took a human seeing them to detect them (and not a satellite - ???) It's this and many other things that make the movie just seem like a cobbled-together set of action sequences with very little thought. We have almost zero background on the world situation at the time, which is made most obvious by these events (if the Moon is a war zone, who's at war? Over what?)
   
   
4. Why does a biomedical station have to be in interplanetary space between Earth and Mars? What do they get out there that they can't get in Earth orbit? This is where the movie more or less lost me.
   
   
5. Why again do they have to go to Mars to transmit to Neptune? And at closest, the one-way light speed communication time is four hours. Even if there is some hint I missed that in fact he's sitting there for hours, this is not conveyed well.
   
   
6. The "psychological" aspect to the movie - the father-son relationship, the protagonist's personality structure - is so trite and ham-fisted and again feels so crow-barred in that it's simultaneously irritating to have to sit through, and annoying at how ineffective it is. I thought the psych evals were going to be a clever plot twist and Pitt's character was fooling them.
   
   
7. Antimatter flares heading toward Earth and destroying all life? Even if this were the most realistic depiction of space travel, the liberties taken with other aspects of science dominate. It's a poor man's Interstellar, right down to its less effective attempts to carry on in the tradition of 2001.
   
   
8. The philosophical implications of being the only, or the first intelligence - unless there's something really subtle that the summaries missed, this movie really missed an exploration of a theme that's under-explored in science fiction in general and especially in movies.
   
   

Reinstate George Anderson at Oakland Music Center

This is George in Down Factor and From Hell. (Second from right - next to Paul Bostaph from Slayer.) I had the good fortune to know George, wow, over 15 years ago through a series of coincidences. He's a really good guy and a huge part of the East Bay metal scene. (Here's Walking Dead off Ascent From Hell.)

He should remain at Oakland Music Center. You should help make this happen - Change.org petition is here.

The Singularity Will Be An Extinction Event, and an Endogenous One

There have been exogenous extinctions, ie not from an ecosystem's "internal contradictions." Examples are massive magma flows like the Central Atlantic Magmatic Province at the Triassic-Jurassic boundary, or the asteroid strike like the K/T Boundary. These were at least partly caused by out-of-context events that life on Earth did not influence. Then there are endogenous extinctions, which were caused entirely by the actions of the system itself, with no external disturbance. The best example is the Great Oxygenation Event, where the cyanobacteria inadvertently poisoned themselves, and paved the way for a whole new kind of metabolism. About every 26 million years, a superpredator develops and kills everything – humans are filling this role currently – and even if there's not an extinction, there's a local minimum in biodiversity and ecological robustness.

Since we're the aerobic beneficiaries of the Great Oxygenation, we like to narrativize this in the form of a teleologic happy ending. That is: the story becomes, yes the cyanobacteria poisoned themselves, but it was to make way for the glory of oxygen-breathing life. That oxygen they fatally polluted themselves with turned out to be an improvement, a new fitness landscape. Any endogenous extinction clears the way for evolutionary progress!

This is false. Of course the Great Oxygenation Event turned out to be survivable, because we're here looking back on it. But choose any other model example of a closed ecosystem where the endogenous activity of the local organisms is rapidly changing their environment, and you are unlikely to find that the majority of them are success stories. Things poison themselves, and end up with no descendants that can survive. (There is no argument to exclude humans from this phenomenon. Both deforesting Easter Island and the ongoing Great Carbonization Event are good examples.)


Two implications follow:

1. The reason for the Great Silence (ie the Fermi paradox) could be that there are many watery worlds out there which evolve local cyanobacteria, but they have their own endogenous shocks, and these do not result in a survivable planet, or at least in a richer potential fitness landscape. As in Conway's Game of Life, if they're lucky they either settle into a simple oscillating system (bloom, mass extinction, bloom, same kind of mass extinction, ad infinitum) or the ecosystem collapses completely and ends.

Speculation regarding this: we're fairly confident the first metabolism on Earth was sea vent iron sulfur organisms, using sulfur in what is now oxygen's chemical role. The Great Oxygenation may have only happened when it did, a full 1.5 billion years after the first life and at least 800 million years after photosynthesis appeared, because an asteroid delivered molybdenum, allowing nitrogen fixation and more efficient anaerobic metabolism. Whatever the reason, had this happened prior to photosynthesis, we may have ended up with an Earth poisoned with sulfur or at least with a massive amount of oxidized sulfur.

In an interesting parallel observation: we're also confident that Venus was once a wetter, cooler world that had a runaway greenhouse effect. One of the mysteries of Venus is the origin of all the sulfur in its thick atmosphere; to a first approximation all sulfur on Earth's surface is assumed to be from volcanoes, but why so much more on Venus? Another mystery is the identity of the small UV absorbers (about the size of bacteria) that form the dark bands in its atmosphere; one idea is that they're cells descended from ancestors that evolved at the surface and now can only survive in the more benign lower temperatures and pressures of the high clouds. If indeed these are the survivors of a Great Sulfuration Event, while the event did not result in total extinction, it limited the Venusian ecosystem to oscillate on a barren fitness landscape, just from the bad luck of having richer crust contents or earlier impacts with potential-enzyme-cofactor-bearing asteroids that allowed more efficient iron-sulfur metabolism.

(Recent evidence however suggests a massive volcanic event 700 MA ago that resurfaced the planet after massive flows; this which may be enough to explain all the sulfur. A gradual boil off of water remains quite likely, for two reasons – the D/H ratio on Venus is about 150 times higher than Earth, where comets have at most a 3 times higher ratio than Earth, suggesting loss to space of hydrogen from water and preferential retention of the heavier nucleus; and that such a massive volcanic event could have been caused by the loss of water, and the cessation of plate tectonics which allow a cataclysmic buildup of heat. It's interesting that the Siberian trap flows and CAMP happened during a period on Earth when the continents were crammed together and perhaps less efficient at letting out volcanic heat, though these events were still nowhere near what happened on Venus.)

2. If a technological Singularity occurs, it would be an endogenous extinction. In this case we are the cyanobacteria, and our extrasomatic adaptations are the contradiction internal to the system, and the AIs are our oxygen-breathing descendants. Like them, we produced the conditions that destroyed us and paved the way for the next phase of life. It's true that cyanobacteria and anaerobic organisms persist but do not dominate the world as they did in the Archaean. Even if cellular life survives the Singularity, being relegated to the role of cyanobacteria is unappealing for most.

But then there is another possibility, in which the AIs drive themselves extinct too. Think of this as the super-pessimistic case. Singularity optimists think we can benefit from or at least co-exist with superintelligence (becoming the equivalent of cyanobacteria is actually optimistic in this scheme.) Singularity pessimists think the event will kill all biology. Here, I suggest the super-pessimist position, which is that the Singularity may kill us, then also itself, in the final, most spectacular ecocide of Earth's history. Why? One theory is that any self-improving superintelligences will necessarily disassemble matter, including whole planets, into atoms that can be used for computation. But there is no principle stating that intelligence must always exceed power; that is, that impact of behavior must grow more slowly than ability to predict impact of behavior. Certainly it didn't happen with cyanobacteria, and given the sluggishness of our response to global warming it might not be happening with humans. Even if the AIs are in fact superintelligences, they are still not omniscient. As they're disassembling everything, they may get to the end of a predictive computation and realize that part of the code has gone cancerous and is replicating out of control (and consuming matter in the process) and can't be called back, or they're going to run out of power before they get to the next planet or star system, or overheat, or whatever problem an AI might run into.

Therefore, if the Singularity does happen, it would be just one type of endogenous extinction. If in a hundred million years, aliens or their self-replicating probes visit the solar system (if such things ever occur in the history of the universe) they might find its dusty, partly-disassembled remains, and file the data under "ecosystems that ended with behavioral/artifactual singularities" and then move on. Interestingly, we have already found old planetary systems that are far dustier than we would expect, with no explanation for the inner dust ring and a some constant replenishment process. Even this assumes that the self-replicating alien probes can get there before becoming cancerous dead-ends themselves.

Gamma Ray Bursts as a Reason for the Sterility of the Universe

One answer to the Fermi paradox is that we are in fact alone, because life - at least intelligent life - is vanishingly rare or completely absent. If we ever get probes to other star systems, we may well find that any water world has its local cyanobacteria, but nothing beyond that.

And what exactly is it that this star system has been so lucky to avoid by accident? Gamma ray bursts are an obvious candidate. A 2014 paper by Piran and Jimenez use the known frequency and distribution of GRBs and calculate the likelihood of an ecosystem-annihilating one. What they find is that for systems within 13,000 LY of the galactic center, there is a 95% chance of a lethal GRB in the last 500 million years, and out where we are it's about a 50% chance. They speculate that some of our past mass extinctions may well have resulted from a GRB (the Ordovician-Silurian extinction event has been speculated without much evidence to be such an an extinction.)

So, it may well be that the Great Filter, or at least a major component of it, is not something endogenous to the sequence of evolution, but rather something completely random and external. It is therefore meaningless to talk about the Great Filter being "in front of" or "behind us."

This may also mean that we really are alone in terms of intelligences which, though boring, is the options we should wish for, it were up to us.

Phantom Hound, Northern Face (2019)

Terraforming Venus; Venus-forming Earth

Terraforming Venus would require taking almost all of the CO2 out of its atmosphere, so it becomes breathable, doesn't crush us (currently 90 atm pressure) and cools the planet down. Using our current mechanical carbon scrubber technology may seem simplistic and unimaginative, but the other options that have been discussed feature similar science-fiction-level ideas (crashing outer solar system ice moons into it, locking carbon into the crust down to a kilometer deep, or getting theoretically present hydrogen out of the mantle.)

This is less likely to happen than being able to move moons around the Solar System. Image from reddit.com/r/mapporn.

Let's make many optimistic assumptions:

That we can build self-replicating independent carbon sequestration plants; this minimizes transport costs and covers the planet.

That they can build and fuel themselves from materials available on the surface of Venus.

That they can withstand conditions on Venus (when the longest any machine we've put down has lasted is on the order of an hour.)

Current carbon sequestration plants are the size of a cargo container, and sequester 900 tons of carbon per year. Assume that this is the rate at which they operate on Venus, and that self-replicating carbon sequesterers are 100x bigger than the real, non-self-replicating ones we have.

Assuming near 100% working replicas, and a one-year self-replication cycle, it would take 40 years to cover the entire surface of Venus with these - after which they would take 2000 years to clean the atmosphere of CO2. (This would still leave a nitrogen atmosphere several times higher pressure than Earth's.)


Venus is not the best candidate for terraforming or habitation, and humans will not settle its surface for thousands of years at least. We should concentrate on terraforming planets in our solar system, building self-replicating technologies, and having humans in isolation from Earth in case of some sort of collapse (most easily, on the Moon.)


On the other hand, here on Earth, just to keep even with carbon emissions at the 2017 level, we would need 40 million of the scrubbers we currently have. That means no matter where you went on Earth, there would be one within less than two and a half miles of you.

We do have machines that are Venus-forming Earth, by making more CO2. They aren't self-replicating, but they seem to have a relationship with one species (unclear if parasitic or symbiotic) and in places they cover the surface just the same.

Star Wars Episode IX Review (CONTAINS SPOILERS BUT MAY NOT MATTER SINCE I'M THE LAST ONE TO SEE IT)

It's the best of the three new ones, and I think the second best in the entire franchise after Empire. I'm lazy, so some of these things would be easy to look up but I didn't. In no particular order:

• Overall, a fitting end to the saga. Much better than Episode VIII. Glad JJ Abrams is back; he's the master of playing well in others' universes. You walk out feeling that you saw a good Star Wars movie, much like Episode VII.
  
  
• As a Star Wars movie, at some point there will be: a desert planet, a cantina, a scummy trading city with a motley assortment of criminals, and people rescuing their friends and admitting how zany they are because they’re making it up as they go.
  
  . But it's not dwelt upon, and there were so many types of planets in this one that the desert planet doesn't stick out. Also, I hope I'm not turning into a social justice warrior, but the colorful festival on the planet with "third world" aliens did bug me a little bit, just because it seems so obvious.
  
  
• In that spirit: Star Wars movies are fantasy movies in space: knights, sword-fighting, wizards. A horseback attack on a starcruiser is therefore not only cool and original, it completely fits. Also, it stuck out in Episodes I through III that a) there was no improvement in technology across 30 years and b) that late 90s cell phones were about as good as Obi Wan's communicator. Some of the tech in this one looks positively 1980s - wired headsets, colored wires in C3PO's head that look like a Commodore 64 console - and that's great. It fits Star Wars perfectly. It's a fantasy movie, and these are set pieces to maintain the tone - it's not about technology at all.
  
  
• I noticed in the end credits for animation, there was a group of 8-10 names together that looked Thai or Lao. I tried to look up whether a studio in one of those places was used but couldn't find any mention. Always good to see more talent in the game, it benefits film-goers.
  
  
• I couldn't remember if Carrie Fisher died before they made this (she did), and couldn't tell if she was live, computer-generated, etc., and wasn't particularly worried about it either way. It's that last part that says the most I think.
  
  
• The introduction of matter transmission through force connections (and its continuing use) is quite a good cinematic trick. It's creepy as hell when Ren grabs Rey's necklace, and then this trick is used in the final battle with the Emperor (unlike some inventions in Episode VIII like hyperspace missiles.)
  
  
  
• The action starts immediately at the beginning and doesn't let up for quite a while. It's also full of plot twists. Nothing like the (pointless, non-plot-advancing) dead space in Episode VIII.
  
  
• Plot holes, discontinuities, and other jarring moments must be taken in context with the franchise. I'm a fan of hard science fiction (i.e., real physics) to the core but if I ever directly overhear someone complaining that "it's unrealistic because there's hyperspace" I will punch them. That said, no one came to help in the second one, but Chewie and Lando can magically raise a rebellion in a few hours by flying around in person? Doesn't seem required to advance the plot, though it does feel good and advance a nice moral ("they win by making you feel alone") so it didn't bother me so much. Also, where has Lando been?
  
  
• I'm going to come out and say it. Grown-up Daisy Ridley is much, much more attractive than at the start of this trilogy (and she wasn't bad then either.) She's also come into her own as an actor.
  
  
• Good performances also from Adam Driver (duh) and Oscar Isaac. I always wonder how hard it is for Boyega to stay in-accent when he's working with other English actors. As time goes on, he gets by more on his innate charisma, which is fine because he's just likable anyway (honestly, it's the very rare actor who actually masters another character and doesn't just enhance his innate personality. I like watching Robert Downey Jr. and Anthony Hopkins, but come on, how different are they on-screen from their actual personalities? Gary Oldman and Christian Bale actually get outside their personalities for their characters, which carries a penalty of not being as "follow-able" as they might otherwise be.)
  
  
• Lots of nice parallelisms in this and tying up of themes. The Empreror as master manipulator tries to rise above the paradox of the Sith by having his death be the key to the rise of the Sith (and if Rey doesn't do it, her friends die and the fleet takes over anyway.) The balance brought back to the Force requires the dyad, with Ren and Rey. Ren, again Ben with the same words he said when he killed his father. Leia's death as she kills her son by distracting him (Ren killed Solo where Vader couldn't bring himself to kill Luke, twice.)
  
  
• Kylo Ren has to announce that Han Solo is a memory so we don't get confused. Luke has sparkly blue outlines so we know the difference between a memory and a Force ghost.
  
  
• There's a little bit of babbling of the sort that annoyed Alec Guinness, which annoys me mostly because you don't know where things are going and you can talk your way (in an unsatisfyingly unpredictable way) out of any plot knot. Then again, the Force is if nothing else a script writer's dream to resolve what would otherwise be massive plot holes by appealing effectively to magic.
  
  
• Much better psychology in this one, thinking about the characters' motivations (e.g., Hux being a spy because he hates Ren.)
  
  
• At the end where there's a crowd watching Palpatine and Rey: where did all these mystery Sith come from? And why have we never seen other Knights of Ren before? What is their connection to the Sith?
  
  
• The creator of Darth Maul said that Lucas came to him and said "I want you to use your worst childhood nightmare as inspiration." He described to Lucas a pale face slowly revealed by flashes of lightning. Sound familiar? I was happy that they used this.
  
  
• I didn't notice any lens flare, but there is a shot of Kylo Ren standing in front of the heaving ocean after Rey leaves, a bit fuzzy and shaky as if shot from far away, that gives it more immediacy. Adam Driver also looked genuinely cold, and I wouldn't be surprised to learn that he insisted on being cold and wet in reality for these shots.
  
  
• Rey being a Palpatine is somewhat of an obvious plot twist, just because if she IS the daughter of someone significant, the only decent move left is for it to be Palpatine (with intervening parents; why did they turn out so lame?)
  
  
• I was annoyed that a non-Jedi (Leia) could magically continue Rey's training. ("Hey, I'm a surgery resident. My attending just died. His sister is going to come continue to teach me surgery.") But they closed that loophole.
  
  
• Once Rey explained she gave a little bit of the force away to heal the giant snake critter, you could see a self-sacrifice (from someone) coming down Fifth Avenue in a cab. Same with the accidental force lightning, which immediately gave away what I suspected about Rey being a Palpatine. Good on the writers, I actually thought Chewie was dead. I'm sure that there are religious fundies somewhere all bent out of shape that Jedi can heal people.
  
  
  
  Above: Jedi Christ, who can heal the sick; only Sith can raise the dead. I bet Golgotha would have been a whole lot different with a light saber.
  
  
• Good coordination with trailers and writers. They know going in that everyone knows Palpatine is in it. I'm always amazed when trailers give away things in the movie and the film-makers expect you to be surprised (often this is no doubt marketing that's not in their control.)
  
  
• I thought C3PO was added to the list of main character deaths - a robot is its memory in a way that humans are not - but he was saved too.
  
  

Timeline of Manned Interstellar Travel, Based on Simple Economics: No Humans on Alpha Centauri Planets Until 2613

It has been estimated that a manned Mars mission would cost $100 billion. Compare this to the most recent unmanned lander, Insight, at $830 million; putting people on Mars then comes with a cost multiplier of 120.

The Initiative for Interstellar Studies estimates that an unmanned interstellar mission would cost at least "in the trillions"; Centauri Dreams cites Odenwald at $174 trillion. Assuming the same scaling, the lower and upper bounds on that then suggest that a manned mission would cost from $240 trillion to $21 quadrillion.

If on the other hand we take the projected cost of a manned mission to Mars, and assume it scales linearly with distance, a manned Mission to Alpha Centauri would cost $55 quadrillion.

It's worth pointing out here that world GDP is $80 trillion. Let's assume an annual economic growth rate over time of 2%. Let's also assume that starting tomorrow we put ALL of GDP toward such a mission - that is, every last human is working this mission and just barely otherwise just barely surviving as peasants eating crumbs.

Assuming an annual economic growth rate over time of 2%, then at earliest, we can launch a manned interstellar mission at the earliest by 2227; at latest, by 2501.

But forget about that. Because neither you, nor any other human on this planet will sign up tomorrow for their descendants being reduced to slavery for centuries for a space mission, which is what those numbers assume. So let's assume we continue to spend money on space exploration at the same rate that we in the US currently are - about 0.11% of GDP. This is already quite a generous assumption, given that most countries can't afford to dedicate such a fraction of wealth to endeavors that don't quickly return on investment. If you're more optimistic and want to set the relative rate of expenditure (over centuries) to the highest it has ever been (in a democracy - you said you were optimistic right?) that's 1966 USA, which is about twice what it is today, and only makes it happen 35 years earlier. (This is more dependent on economic growth than space program expenditure.) So let's stick with current NASA budget fraction, and assume that the future space program is ONLY working on this one mission.

By these assumptions, we can launch the mission at earliest by 2570; for the upper bound estimate, by 2845.

Our fastest spacecraft so far would take another 30,000 years after launch to get there. Let's be more optimistic and assume that the light sail technology we're talking about for unmanned probes also applies to manned craft, and can get the ship up to 10% of the speed of light. Therefore, taking into account travel time and speed-of-light delays, we wiill get the interstellar "Eagle has landed message" at an absolute cheapest earliest date of 2618.

Of course this is still unrealistic, because we're still assuming mission development starts in earnest tomorrow, assuming every government on Earth will let us use a NASA-sized fraction of their GDP for this, and that they will continue to cooperate for at least 550 years building the mission. Think of this in reverse: it's as if in 1470, the middle of the War of the Roses, and the Russians and Poles and Lithuanians still throwing off the Mongol yolk, everyone started spending money and cooperating on a project and continued to cooperate on it until this year.

I think it is unlikely, barring unforeseeable scientific revolutions, that human beings will leave the Solar System this millennium. I think it is likely that there will be civilization or species-threatening or destroying events in this millennium. This discussion of colonizing other planets to mitigate existential risks has a scatter plot listing a probability of event happening within 200 years/risk of civilizational collapse for nuclear war, coronal mass event, rogue AI, and nuclear war as 90%/20%, 70%/90%, and 95%/70%.

Using those same numbers, in the time period until launch there's a greater than a 96.6% chance of a rogue AI, and a greater than 99% chance of coronal mass event or nuclear war.

But fully automated probes could get out more quickly, particularly if we design self-reproducing von Neumann probes. We should start terraforming Mars now, as practice for remotely terraforming planets with von Neumann probes for when we eventually get there. We have time to terraform them, because if physical human bodies ever do get there, it will be in the distant future. But we do not have that much time to get the launch the hardware, which suggests we should at least colonize the Moon as insurance. Cryonics and hibernation technology at this point is still basically science fiction. These numbers are depressing given our previous dreams, but we calibrated on going from powered flight to standing on the moon in 2/3 of a century.