Comment by cellbioguy on Genetically Modified Humans Born (Allegedly) · 2018-11-30T03:14:30.920Z · score: 13 (6 votes) · LW · GW

Quotes from people in the field now that more information was divulged:


' “It’s even more appalling and abhorrent now,” Liu, cofounder of the genome editing company Beam Therapeutics, told STAT. “His responses displayed a deeply disturbing naivete about the issues involved. I have a deep fear that this could set back the field [of therapeutic genome editing] so badly that patients won’t get the therapies they desperately need.”

Other experts in the audience were equally critical. “Having listened to Dr. He, I can only conclude that this was misguided, premature, unnecessary, and largely useless,” said bioethicist Alta Charo of the University of Wisconsin, a member of the summit organizing committee. '


' I would add “criminal” to that list myself, because it does appear that the consent forms that the parents signed told them that this was an HIV vaccine research project. It appears that Dr. He was the only person to explain the experiment and the consent form to the patients, and God only knows what he told them or what they understood of the work itself. By American legal standards, he has (I’d say) exhibited depraved indifference to human life, and in a better world he’d stand trial for it.

It’s hard to see how this could have been done much worse. It’s obvious that human embryonic gene editing is not ready for use yet, and this is not the work of some brave pioneer because we already knew that. Going ahead with this experiment was reckless, dangerous, counterproductive, and arrogant beyond belief.'


' We work with worms and zebrafish to generate precise point mutations. The amount of screening required to find a precise edit among the mix of indels and complex rearrangements/insertions makes me shudder at the thought of attempting this so brazenly in patients. '


'The technology is immature, this was an inappropriate modification, AND HE DID IT INCOMPETENTLY. I have no words. '

Comment by cellbioguy on Genetically Modified Humans Born (Allegedly) · 2018-11-30T03:02:28.921Z · score: 17 (7 votes) · LW · GW

Coming out of hibernation specifically to comment on this.

There is now reported gene sequencing info. The 'edit' is an unmitigated disaster hack-job - random insertions and deletions caused by desperate DNA-repair machinery, not a clean adjustment to a known allele. Just like what tends to happen a lot of the time when you try to CRISPR mammals that love non-homologous end joining rather than microbes that like to use homologous recombination. It is a LOT easier to just take a chainsaw to a genome and break stuff rather than actually edit cleanly. For lab animals you can just keep trying until you get it right then breed it. But now the two sequenced people (both apparently are MOSAICS of multiple different mutations!) have alleles never before seen that we have no idea what the immunological impacts of are.

Responsible research, this is not. Ghoulish tinkering with human subjects.

Comment by cellbioguy on Security Mindset and the Logistic Success Curve · 2017-11-27T15:37:30.467Z · score: -20 (17 votes) · LW · GW

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Comment by cellbioguy on Open thread, October 2 - October 8, 2017 · 2017-10-04T21:36:26.373Z · score: 2 (2 votes) · LW · GW

Latest results on KIC 8462852 / Boyajians Star:

After comparing data from Spitzer and Swift - an infrared and ultraviolet telescope - whatever the heck the three dimensional distribution of the material causing the brightness dips, the long-term secular dimming of the star is being caused by dust. Over the course of a year of observations the star dimmed less in the infrared than in the ultraviolet, with the light extinction dependent upon wavelength in a way that screams dust of a size larger than primordial interstellar dust (and thus likely in the star system rather than somewhere between us) but still dust.

Still a weird situation. There cannot be a very large amount of dust in total since there is no infrared excess, so we must be seeing small amounts of it pass directly between the star and us.

The dipping is also semiperiodic, to the point that a complex of dips beginning in May was predicted months in advance.

Comment by cellbioguy on Open thread, September 25 - October 1, 2017 · 2017-10-01T00:39:41.401Z · score: 0 (0 votes) · LW · GW

One coming this approaching spring will. This one was livestreamed but not sure if it was recorded.

An update to this was presented:

Comment by cellbioguy on Open thread, September 25 - October 1, 2017 · 2017-09-30T07:26:31.966Z · score: 1 (1 votes) · LW · GW

Attended my first honest to god Astrobiology meeting/symposium/conference. Wow, it was amazing...

Comment by cellbioguy on Open thread, September 11 - September 17, 2017 · 2017-09-12T17:49:37.105Z · score: 5 (5 votes) · LW · GW

People usually point to there actually being hydrogen and carbon accessible on the surface of Mars, in the form of widespread permafrost/humidity and the CO2 atmosphere, whereas the only biomass/fuel precursor element that exists in large quantities on the moon is oxygen (in the rock, along with various metals and ions, just like rock on Earth, requiring interesing chemistry and/or molten rock electrolysis to get it out). Not much in the way of precursors to organic material on the moon.

Personally I think both places are kind of absolute shit-holes for canned monkeys. Both are science bonanzas, the moon for information on the proto-Earth, and Mars for looking at a body which has had much less geological recycling since Hadean times and an ancient second hydrosphere and for all we know biosphere.

Comment by cellbioguy on Is life worth living? · 2017-08-31T01:58:40.581Z · score: 2 (2 votes) · LW · GW

I don't see the difference between the two.

To answer the question of the title: Yes.

Comment by cellbioguy on Sam Harris and Scott Adams debate Trump: a model rationalist disagreement · 2017-07-20T21:46:16.699Z · score: 1 (1 votes) · LW · GW

Only recently seen two instances of sleazier self-promotion.

Comment by cellbioguy on Open thread, Jul. 17 - Jul. 23, 2017 · 2017-07-19T18:05:25.951Z · score: 0 (0 votes) · LW · GW

What with the way the ASIC mining chips keep upping the difficulty, can a CPU botnet even pay for the developer's time to code the worm that spreads it any more?

Comment by cellbioguy on Open thread, Jul. 17 - Jul. 23, 2017 · 2017-07-18T23:41:41.676Z · score: 4 (4 votes) · LW · GW

I have spoken to someone who has spoken to some of the scientific higher ups at Calico and they are excited about the longer-term funding models for biomedical research they think they can get there for sure.

I have also seen a scientific talk about a project that was taken up by Calico from a researcher who visited my university. Honestly not sure how much detail I should/can go into about the details of the project before I look up how much of what I saw was published versus not (haven't thought about it in a while), but I saw very preliminary data from mice on the effects of a small molecule from a broad screen in slowing the progression of neurodegenerative disease and traumatic brain injury.

Having no new information for ~2 years on the subject but having seen what I saw there and knowing what I know about cell biology, I find myself suspecting that it probably will actually slow these diseases, probably does not affect lifespan much especially for the healthy, and in my estimation has a good chance of increasing the rate of cancer progression (which needs more research, this hasn't been demonstrated). Which would totally be worth it for the diseases involved.

EDIT: Alright, found press releases.

Comment by cellbioguy on Open thread, Jul. 03 - Jul. 09, 2017 · 2017-07-06T23:07:25.390Z · score: 9 (9 votes) · LW · GW

Postdoctoral position acquired. May be doing some work off a NASA astrobiology grant, eventually.

Comment by cellbioguy on Dissolving the Fermi Paradox (Applied Bayesianism) · 2017-07-05T06:56:00.468Z · score: 2 (2 votes) · LW · GW

The perils of posting quickly in the middle of rapid apartment hunting (for a new postdoc position at a university with a bunch of yeast cell biologists AND astrobiologists! YES!).

I was referring to slide 27, with the various probability distribution graphs conditioned on various observations. The 'no colonization' conditional graphs all leave the left low-number tail intact while chopping off the probability bulge to the right of 'one in our galaxy' in various different ways. But this is only valid under the assumption that exponential colonization/galactic scale visibility with a few decades of rather poor observations against the screaming burning backdrop of the astrophysical universe is POSSIBLE. (Allow me to preemptively counter the 'but only one has to be able to' argument, this is an event that would be extraordinarily correlated across everybody). There are vast numbers of possibilities for the fate of intelligent systems that are not rapid extinction or consuming the universe that are insufficiently explored by so many people.

Without these conditional probability bounds, the given probability distribution is distinctly uninformative. It basically says 'with the distribution of probabilities that can be extracted from literature on the subject, no intelligent systems in the visible universe is as likely as thousands to a billion in our galaxy', that little bump on the right side of the distribution is pretty intense). I also happen to think that the given abiogenesis probability distributions are far too wide to the low side, that we have not excluded the possibility of multiple completely independent biospheres in our own solar system at all, and that complex life has some possibility of being limited more by geological/orbital/energetic issues than evolution which introduces interesting bimodality to that probability distribution, but that's just me (and the people whose work I follow).

Comment by cellbioguy on Dissolving the Fermi Paradox (Applied Bayesianism) · 2017-07-03T18:30:05.853Z · score: 4 (4 votes) · LW · GW

I was talking more about things like the great oxidation (reduced atmosphere and iron in the water to a very little oxygen in the air and hydrogen sulfide in the water) and the proterozoic/phanaerozic transition (low-phosphate oceans with some hydrogen sulfide and low oxygen levels to oxic, high-phosphate very productive oceans and lots of atmospheric oxygen that supports an ozone layer).

The great oxidation is looking like it almost certainly was NOT due to the recent invention of oxygenic photosynthesis, but was instead a geochemical tipping point that came when the slowing geology of the earth and the steady oxidation of crustal sinks could no longer absorb all the biogenic oxygen and the very-small-compared-to-the-crust atmosphere whipped into a new state long after the oxygenic photosynthesizer drivers that ultimately caused it were in place, triggering massive biochemical shifts across the biosphere in a short time.

The proterozoic/phanerozoic transition is looking more and more like it could have been an interesting earth-system-scale flip that had something to do both with a major increase in exposed above-water landmass (coming from the growing continents and steadily thinning oceanic crust causing a sudden shift when the ocean level fell to a level that exposed large plains rather than just mountains) and an intrinsic bistability of ocean chemistry such that there are two stable states, one with low primary productivity/oxygen and one with high, that you can only flip between via some kind of shock. Multicellular animals as we know them may simply not be a viable strategy in the low-productivity low-oxygen state, and predators that can drive evolutionary arms races of the sort that probably drove the Cambiran explosion certainly are not. As such, the late emergence of multicellular heterotrophs on Earth (there is evidence for multicellular photosynthesizers for over a billion years, last I saw) is not necessarily due to them being HARD, but due to the need for the geosphere and the chemical environment to go through some phase transitions first, some driven by slow buildups of material over time and some possibly more stochastic. They show up remarkably fast after those phase transitions are complete.

EDIT: I don't understand the assertion in the linked slides having to do with abiogenesis that genetic systems that were precursors to ours could've been more stable than ours. LUCA had our genetic system, full stop, and is certainly older than 3.7 gigayears at the VERY least, for all we know it could be back to 4.4 gigayears. Our genetic code also bears the imprint of an explosive period of waaaaay pre-LUCA evolution in which it was optimized to be literally one in a million in terms of resistance to mutational damage. What came before LUCA was unstable and fell into a stable state, not the other way around. Furthermore there could be other stable biochemistries, without the need to posit going directly here (though I will go out on a limb and say I suspect protein will be everywhere there is water as a solvent and that genetic polymers are likely to have phosphates, hah).

EDIT 2: Okay now I see what you are referring to about transitions in abiogenesis, treating it as a chemical event with some odds per unit volume per unit time. A reasonable analysis, better than most, but neglecting it as a self-reinforcing PROCESS rather than a singular event. There are other schools of thought, though. There are others who, treating living things as dissipative systems that are a channel through which to discharge persistent chemical disequilibrium and our core biochemistry as being able to do so at a remarkably low level of organization, see abiogenesis as a form of breakdown into the preferred state of a planet out of equliibrium and under chemical stress. The idea being that even though the breakdown is stochastic, it is still the preferred state you are pushing the system into via putting a stress on it. See Dr. Eric Smith for a discussion of the idea from one direction (there is a lot of diversity in ideas on this front):

EDITED VIDEOS, wrong but still relevant link earlier

Comment by cellbioguy on Dissolving the Fermi Paradox (Applied Bayesianism) · 2017-07-03T16:41:22.008Z · score: 0 (0 votes) · LW · GW

This analysis remains predicated on the assumption that a long-lasting intelligent system is easily visible over cosmological or galactic distances with the sorts of investigations that have already been performed by us.

EDIT - BTW, there's a lot of interesting evidence coming out for the ease of abiogenesis, and that thinking of earth's biosphere evolution in terms of 'it took 4 gigayears to get to get X, what if thats just rare' is the wrong way of thinking about things - that you need to talk about geochemical phase transitions rather than accretion of innovations, after which you get explosive changes.

Comment by cellbioguy on Open thread, June 26 - July 2, 2017 · 2017-06-28T21:50:29.823Z · score: 0 (0 votes) · LW · GW

Is a solution in which control of the network is secured through the same private keys that secure the stores of value an option?

Comment by cellbioguy on What useless things did you understand recently? · 2017-06-28T21:24:41.025Z · score: 9 (9 votes) · LW · GW

Most of the interesting-tasting or psychoactive chemicals that plants make are there to ward off being eaten or infected. Caffeine and mint oil are among the plant insecticides, all sorts of other things are toxins to vertebrates. By virtue of being megafauna we can tolerate amounts of toxic stuff that will kill smaller organisms by mixing them with other foods, and our particular biochemistry happens to be particularly strong against some (and weak against others, just try to eat hemlock). Stuff we can tolerate but still has effects on us (caffeine, capsaicin) can be interestingly psychoactive, stuff that doesn't hurt us can be interesting to taste (mint, cinnamon, garlic), and there's interesting correlations between spice use and parasite load in food (that could be confounded six ways to mars)...

Comment by cellbioguy on What useless things did you understand recently? · 2017-06-28T21:14:59.053Z · score: 0 (0 votes) · LW · GW

Why so many of our spices are toxic to other animals and insects.

Comment by cellbioguy on Are conferences an inefficient/terrible discussion forum (in addition to academic papers)? · 2017-05-28T15:01:35.938Z · score: 0 (0 votes) · LW · GW

There's a lot of that here.

Comment by cellbioguy on Open thread, May 22 - May 28, 2017 · 2017-05-25T21:25:01.359Z · score: 1 (1 votes) · LW · GW

Can you buy it in liquid form? Then you can dilute it to whatever dose you want.

Comment by cellbioguy on That is not dead which can eternal lie: the aestivation hypothesis for resolving Fermi's paradox · 2017-05-18T02:43:16.277Z · score: 2 (3 votes) · LW · GW

More to the point, anything that DOES use matter and energy would rapidly dominate over things that do not and be selected for. Replicators spread until they can't and evolve towards rapid rates of growth and use of resources (compromising between the two), not things orthagonal to doubling time like computational efficiency.

Comment by cellbioguy on Fermi paradox of human past, and corresponding x-risks · 2017-05-08T17:12:35.248Z · score: 2 (2 votes) · LW · GW

Of interest

Comment by cellbioguy on LW mentioned in influential 2016 Milo article on the Alt-Right · 2017-04-17T13:51:18.801Z · score: 0 (0 votes) · LW · GW

...Sometimes I REALLY wish downvoting still happened.

Comment by cellbioguy on Astrobiology IV: Photosynthesis and energy · 2017-04-09T09:18:23.892Z · score: 1 (2 votes) · LW · GW

I am continually confused as to why people find seven hundred million years (4.4 to 3.7 billion years ago, the date at which we have both the oldest intact rocks on earth and not coincidentally the oldest good evidence for living things) an insufficient time to develop biochemical complexity. The Hadean is more unknown (due to no solid rocks surviving from that era due to geological reprocessing) than hellish, at least to a microbe over evolutionary time. There was liquid water and hydrothermal systems, there was basalt, there was more granitic rock, there was an atmosphere, and equilibrium temperatures were almost certainly not exactly extreme. The late heavy bombardment would NOT have touched the subsurface biosphere, there should be continuity of livable environments for that whole time, and could've actually increased the number of interesting hydrothermal environments that chemosynthetic bacteria love overall. Major biochemical inventions and evolutionary transitions can indeed happen remarkably fast, especially when there is no competition to constrain you to a particular ecological niche or established players crowding out newcomers to a process. The genetic code itself shows evidence of an extremely rapid period of evolution with many divergent lineages, of which only one survives in a runaway winner-take-all fashion (more on this in a later post on the nature of LUCA). I see no need to invoke panspermia especially when you have the deep domain split between the bacteria and archaea on Earth, which might be a relic of some deep differences between lineages that invented some important stuff separately.

This being said, GOD YES I want sequencers on other planets in case there is life there with a common biochemistry. Spread of microbes from world to world is not an impossible thing within our solar system. I would highly HIGHLY doubt it between star systems.

The Asgardian archaea are indeed fascinating. They somewhat overstate the case that there are major eukaryotic components in these guys a bit (a lot of the domains are separate rather than strung together the way they are in eukaryotes). There are so many eukaryogenesis models that are consistent with these guys existing though that a lot more research is needed. An alternative hypothesis to them being 'primed to be complex' is that they are abortive linages that peeled away from the eukaryogenesis pathway that lead to us and underwent reductive evolution back towards a standard archaean niche. Things can simplify too over evolutionary time.

Comment by cellbioguy on Open thread, Apr. 03 - Apr. 09, 2017 · 2017-04-07T19:30:56.482Z · score: 6 (6 votes) · LW · GW

Final version of thesis going out within 4 days. Getting back into a semi-regular schedule after PhD defense, death in the family, and convergence of job-search on a likely candidate in quick succession. Astrobiology writing likely to restart soon. Possible topics include:

  • schools of thought in life origins research
  • the nature of LUCA
  • recent work on the evolution of potentiated smart animal lineages on Earth
  • WTF are eukaryotes anyway
  • the fallacies of the Fermi paradox/ 'great filter' concepts
  • the fallacies of SETI as it is currently performed
Comment by cellbioguy on The Ancient God Who Rules High School · 2017-04-07T19:20:08.557Z · score: 0 (0 votes) · LW · GW

I for one had to get up at 5 AM and do homework until midnight most weekdays.

Comment by cellbioguy on The Ancient God Who Rules High School · 2017-04-07T19:16:07.400Z · score: 6 (7 votes) · LW · GW

The phase-response curve of the circadian rhythm to light shifts with age, with the equilibrium position of the wake point latest in the late teens and earliest in early childhood and old age.

Comment by cellbioguy on Open thread, Mar. 20 - Mar. 26, 2017 · 2017-03-24T22:20:18.129Z · score: 10 (10 votes) · LW · GW

PhD acquired.

Comment by cellbioguy on Open Thread, March. 6 - March 12, 2017 · 2017-03-12T02:19:35.873Z · score: 1 (1 votes) · LW · GW

It is in! Now 2 days to put together final edits for my committee, 2 weeks to seminar/defense, and then a week or so for final revisions... interesting to see 6 years in 133 pages.

Comment by cellbioguy on Open Thread, March. 6 - March 12, 2017 · 2017-03-09T17:27:15.593Z · score: 10 (10 votes) · LW · GW

27 hours to PhD thesis submission. Science is hard.

EDIT first allnighter in a long time.

Comment by cellbioguy on Open Thread, Feb. 27 - March 5, 2017 · 2017-02-27T08:53:38.953Z · score: 1 (1 votes) · LW · GW

Why is the end of a PhD maintained as such a stressful and panic-filled process?

Comment by cellbioguy on Stupidity as a mental illness · 2017-02-11T04:59:31.234Z · score: 4 (4 votes) · LW · GW

But it still sticks around. Simple adaptationism is wrong and all kinds of other processes are also at work in evolving systems, especially in multicellular animals with structured populations and piddlingly tiny population sizes compared to microbes.

Comment by cellbioguy on Dan Carlin six hour podcast on history of atomic weapons · 2017-02-11T03:02:16.350Z · score: 1 (1 votes) · LW · GW

Nothing lasts forever, especially global hegemony.

Comment by cellbioguy on Stupidity as a mental illness · 2017-02-11T02:58:52.380Z · score: 2 (2 votes) · LW · GW

Humans are FULL of weird shit that is not adaptive.

Comment by cellbioguy on Fermi paradox of human past, and corresponding x-risks · 2017-02-07T00:48:21.082Z · score: 0 (0 votes) · LW · GW

I've managed to find someone overlaying the ice core records of the last few interglacials for their own purposes, and although I think this diagram is poorly calibrated in terms of absolute temperature I think it is a reasonable diagram for comparing stability:

It certainly looks to a first glance like our interglacial is significantly FLATTER in terms of average temperatures (in the particular place in Antarctica that this core was taken) than those of the last 500,000 years. The ~23k year age of the reported seeds falls in the middle of the flattish bit of the red line before the rise at the start of the interglacial.

Interesting question if there is a hysteresis to agriculture.

Comment by cellbioguy on Fermi paradox of human past, and corresponding x-risks · 2017-02-05T21:33:06.298Z · score: 0 (0 votes) · LW · GW

Potentially of interest:

Comment by cellbioguy on Open thread, Jan. 30 - Feb. 05, 2017 · 2017-02-03T06:23:37.140Z · score: 3 (3 votes) · LW · GW

People like to think of their brains as some kind of separate regulating thing compared to the rest of their bodies. They're not. Everything is mushed together in a common mileu and the sheer degree of crosstalk between your nervous system and everything else is enormous, through both the general chemical environment and fibers that have nothing to do with the consciously available senses.

Humans did not evolve sitting around writing theses. They evolved spending energy in an active way, possibly with wide variation from day to day. It is completely unsurprising to me that there is an amount of energy use that makes one feel clearer and more productive compared to the sedentary graduate student, and that that can vary from person to person and over time in the same person as their physiological state adapts and changes.

Comment by cellbioguy on Open thread, Jan. 30 - Feb. 05, 2017 · 2017-02-02T02:28:17.497Z · score: 2 (2 votes) · LW · GW

When you bring the paper up it indicates that they are talking about a lack of density in a region, not a repulsive force.

You can treat it as a repulsive force, in the same way you can treat the absence of an electron in a semiconductor as a particle with a positive charge (a 'hole'). With matter density from the bulk of the rest of the universe all around it, the gravity of that matter pulls things near the edge of the low density region away from it and this is functionally similar to repulsion away from the void. The paper finds that the flow away from the low density region towards the generalized rest of the bulk universe is about as important for our galaxy's motion as the attraction towards the local overdensity of the various nearby attractors.

Comment by cellbioguy on Open thread, Jan. 23 - Jan. 29, 2017 · 2017-01-29T05:56:00.231Z · score: 2 (2 votes) · LW · GW

In a crack of time between doing my last data analysis for my PhD and writing my thesis, I couldn't stop myself from churning out a brief sparsely-sourced astrobiology blog post in which I argue that the limited lifespan of planetary geospheres and the decay of star formation rates means that even though the vast majority of star-years are in the distant future around long-lived small stars, we are still a typical observer in that we are occurring less than 15 billion years into an apparently open-ended universe.

Comment by cellbioguy on Fermi paradox of human past, and corresponding x-risks · 2017-01-29T02:49:56.683Z · score: 1 (1 votes) · LW · GW

Aaaaand I just saw a talk in which researchers found what look like barley starch grains in 150k year old Neanderthal dental plaque. Probably from wild-grain porridge.

Comment by cellbioguy on Open thread, Jan. 23 - Jan. 29, 2017 · 2017-01-24T23:47:06.100Z · score: 0 (0 votes) · LW · GW

To say the least.

Comment by cellbioguy on Projects-in-Progress Thread · 2017-01-22T20:31:42.907Z · score: 1 (1 votes) · LW · GW

My internet presence and my IRL presence among my friends has fallen to about zero as I am doing a final push to graduate with my PhD in cell biology and genomics. On a job interview right now for a position studying something I am passionate about for real. Thesis being written (and Latex being learned) for, hopefully, a defense at the end of March.

Its remarkable how much data I have when I actually dig everything up from the last 3 years and lay it out side by side.

Comment by cellbioguy on X risk update, Gliese 710 will pass thru Oort in 1.35 my · 2017-01-17T15:09:24.873Z · score: 0 (0 votes) · LW · GW

Which paper?

Comment by cellbioguy on X risk update, Gliese 710 will pass thru Oort in 1.35 my · 2017-01-17T14:21:52.077Z · score: 0 (0 votes) · LW · GW

You get infall at speeds like that by falling close to the star - it is the strongest gravitational field in the system and the closer an orbit takes you to it the faster you go. Something falling from the Oort cloud to the surface of the sun reaches a speed of 600 km/s at the moment of impact, and at four solar radii away it is moving 300 km/s. Speed goes down with the square root of distance. Sungrazing comets do this all the time in our solar system, but they are for the most part smallish. The data seeing cometary material moving across the face of another star at that speed was interpreted to mean that there were large numbers of large sungrazing comets falling very close to the star at that point in that star system's evolution. Keep in mind that at the distances you are looking at, the entire star system is basically a pixel for most instruments so you are seeing the whole thing superimposed over itself.

When two objects interact gravitationally, the maximum physically possible delta V provided to a small object by the big object by a near miss is equal to twice the orbital velocity of the large object. From far away it basically looks like an elastic collision in basic mechanics, and that maximum speed is provided if it comes in and 'bounces off' exactly along the orbital vector of the larger object with an initial velocity of nearly zero. Planet 9, if it exists, has an orbital velocity on the order of low single digits kilometers per second and if it sent things into the inner solar system that 'elastic collision' would be very much not along the line of its orbit and impart rather less. The biggest thing that could impart velocity changes would be the other star and it would be passing through at 15 kilometers per second, at right angles to the radial direction towards the inner solar system at close approach. Furthermore, near misses would be exceptionally rare. These things are notable for stirring the orbital parameters of very slow moving oort cloud objects by providing a small far-away force for a short time over only a piece of its orbit and allowing some to approach the inner system on orbits with very similar energies rather than adding appreciable energy to the system.

Comment by cellbioguy on X risk update, Gliese 710 will pass thru Oort in 1.35 my · 2017-01-17T14:14:23.116Z · score: 0 (0 votes) · LW · GW

I recall seeing a paper with orbital dynamical simulations in which they found a 2 percent chance that over the remaining lifetime of the sun, the orbital eccentricity of Mercury would increase such that it interacted with Venus, either hitting Venus or getting boosted onto an Earth-interacting trajectory which could lead to a collision or eject it from the solar system altogether, and which puts Venus on a much more closely Earth-interacting orbit. In one simulation out of the 2,500 they did, Mars's eccentricity was perturbed until it became Earth-crossing.

Remember that there is a bit of a selection effect when it comes to looking at exoplanets - we see the compact large planet systems much more easily than systems like ours. The latest work I've seen has suggested that we are a less common class of star system but that stuff like ours might be something like 10% of star systems. Nobody REALLY has a handle on planet formation yet, and it looks like there may be several very different ways that planets and planet-forming material can migrate around the protoplanetary disc during the planetary accretion stage that people argue bitterly over in the literature.

Comment by cellbioguy on X risk update, Gliese 710 will pass thru Oort in 1.35 my · 2017-01-16T00:30:44.532Z · score: 0 (0 votes) · LW · GW

What do you mean by 'we have' 4-5 billion years? A lot happens in that time. Theres a several percent chance of destructive orbital dynamical chaos in the inner solar system during that timeframe coming from the eccentricity of Mars or Mercury, the Earth will almost certainly pop into Venus mode from the increasing solar luminosity by 1.2 gigayears from now (if some parameters are overly harsh maybe as little as 300 megayears and DEFINITELY by 2 gigayears from now). And amusingly enough if we have a longer period of time before popping into the runaway greenhouse, there is a reasonable chance of a carbon crisis in which atmospheric carbon falls low enough that it becomes the limiting factor in biomass production due to the slowing geosphere and increasing burial of carbonate rock. And the average mammalian genus lasts what, ten, twenty million years?

This being said, I again point out that events like this have almost certainly happened many times over the history of the solar system. Even if events like this are rarer than every few tens of megayears due to the larger than average mass of this star, the sun was only 1% dimmer a hundred million years ago. Runaway greenhouses aren't THAT easy to get going and I believe there is evidence from the KT impact that the atmosphere was only strongly disturbed for a short time, potentially single digit years. And there are large impacts not associated with mass extinctions, leading some paleontologists to suggest that they only are associated with mass extinctions when the biosphere was already strongly stressed by something chronic like a large flood basalt eruption. (I myself am partial to the idea that the KT event in particular represents an ongoing low-level flood basalt eruption that got kicked into high gear for a few thousad years by the more or less worldwide 9-pointer earthquake the impact would've generated, providing a double punch). The biosphere and complex life in general is not threatened by impacts.

Comment by cellbioguy on X risk update, Gliese 710 will pass thru Oort in 1.35 my · 2017-01-16T00:10:04.508Z · score: 2 (2 votes) · LW · GW

You can't have an oort cloud comet hit the Earth at 160 km/s. The absolute fastest that anything falling from an orbit bound to our sun (oort cloud comets being very lightly bound) in the outer solar system can hit the Earth is about (((1+ square root of 2)* the Earth's orbital velocity)^2 + Earth's escape velocity^2)^0.5, or about 73 kilometers per second. This is if it falls from basically infinity (oort cloud distances) to the Earth's distance from the sun, reaching solar escape velocity at our altitude (square root of two times our orbital velocity) and then hits us head on in our orbit. The true velocity would vary between 73 km/s and 16 km/s with most values somewhere in the middle. Those measured faster velocities came from comets that were falling closer than one AU away from their parent stars.

Granted that's only a factor of 8 in maximum available energy per unit mass (difference between 73 squared and 160+earth's orbital velocity + dealing with earth's escape velocity as above). Still, this has almost certainly happened before over the Earth's history, many times, on ten to low tens of megayear timescales. Slightly less extreme events would be much more common - events with one tenth the calculated perturbation parameter would be ten times as frequent and come every 1-3 million years. EDIT stellar mass lessens this argument a little, this star is relatively large and thus its perturbation parameter is larger than the average stellar pass at this distance

Comment by cellbioguy on X risk update, Gliese 710 will pass thru Oort in 1.35 my · 2017-01-11T02:12:26.126Z · score: 1 (1 votes) · LW · GW

I think that events like this have happened before, many times. Question is the exact frequency.

Comment by cellbioguy on X risk update, Gliese 710 will pass thru Oort in 1.35 my · 2017-01-10T05:03:49.973Z · score: 0 (0 votes) · LW · GW

On another note, you can come up with an estimate of the hard maximum fraction of stars over Earth's history that bear self replicating systems capable of bridging different distance scales with something that can survive!

Comment by cellbioguy on X risk update, Gliese 710 will pass thru Oort in 1.35 my · 2017-01-10T04:56:35.726Z · score: 2 (2 votes) · LW · GW


I or businessinsider must be missing something with regards to the degree of danger posed by a star going through the oort cloud or with regards to it being a particularly extreme pass, what with businessinsider calling it the strongest perturbation in the future history of the solar system.

The density of stars in our local neighborhood is ~0.004 stars per cubic light year. This close approach is calculated to be ~0.21 light years (13,000 AUs, 440x the distance to Neptune). A sphere that wide has a volume of 0.04 cubic light years. Stars should be at least that close about 0.016% of the time, or for about 713,000 total years out of Earth's history.

Typical relative velocities of nearby stars are in the low tens of km/s. This one is 13.8 kilometers per second. Let's say it spends circa 0.1 LY on a 'close approach' within this volume. Thats a circa 2000 year encounter and you'd expect circa 356 encounters like this one over the solar system's history, one every 13 million years with more continuing into the future. Indeed the first paper mentions other recent approaches that are nearly as close.

Going back to first principles, if you assume a 15 km/s average encounter speed and an approach radius of 0.21 light years, you expect about ~127 encounters at least this extreme over the solar system's history, one every 36 million years or so. More frequently if the average velocity is higher or the spread of velocities is larger. You have to go down to a distance of 0.019 light years (1190 AUs, or 40x the distance to Neptune) before you're pretty sure you aren't going to get an encounter that extreme or more over the lifetime of our solar system so far. Granted one could argue there could be a bit of a selection effect.

This seems to suggest to me that stellar close approaches are likely less disturbing to inner solar systems and/or that impacts are less disturbing to biospheres than some claim. I know that the latter has some support - there are some pretty big impacts in the geological record not associated with mass extinctions, and those that are associated with mass extinctions seem to coincide with long term stressors like flood basalt eruptions.

EDIT i updated the numbers, the timescale comes to circa 10 million years not 3 million years, caught a math burp, but the point still stands. I still can't quite figure out why they're calling it so extreme.

EDIT 2 Actually read the paper. The popular press quotes them as saying this star is the "strongest disrupting encounter in the future and history of the solar system." They ACTUALLY state that the star has the biggest influence on our solar system for at least the last and the next ten million years which is the period of time they can project, not for all time. Events like this HAPPEN, with greater frequency than mass extinctions on Earth.

EDIT 3: Their units for perturbation on the oort cloud are in units of (solar masses / distance squared / velocity ). The perturbation is stronger the slower the star moves and the more massive it is. This relative velocity is on the lower slope of the curve and the mass is higher than many stars (half a solar mass - most stars are dwarfs and I believe the sun is larger than ~80% of stars) so I can see that the SIZE of the perturbation may be a bit larger than distance alone will indicate. I would need a better handle on the distribution of relative velocities and masses to get a good handle on these numbers.

On a related note, I now can't figure out how they're modeling the effects on comets...

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