## Tuesday, November 25, 2014

### PRL: life in 90% of galaxies is killed by GRBs

Science Magazine describes a provoking paper by Piran (HUJI Jerusalem) and Jimenez (U. Barcelona, Harvard) accepted for publication to prestigious Physical Review Letters two weeks ago:
Complex life may be possible in only 10% of all galaxies (Science)

On the role of GRBs on life extinction in the Universe (arXiv, PRL)
The basic claim is rather simple.

This extraterrestrial citizen works with Alza.cz and Alza.sk and spreads tablets and other things all over our homelands. The negative feedback suggests that the Czechoslovak folks may suffer from green xenophobia, after all.

The extraterrestrial ethnic minorities face another problem: (long) gamma-ray bursts, likely to be close to centers of small enough galaxies, take place too often and kill (the ozone layer and) complex life too early. Only 10% of galaxies – typically those that are large enough and sufficiently metallic, similarly to the Milky Way – has a chance to pass this cataclysmic test, and life seems to have a chance far away from the center only.

If true, it has far-reaching consequences. Not only complex life is rarer in the Universe than many people think. But SETI is in double trouble because they are selectively focusing on communication with places that seem to be sterile due to this GRB-induced Holocaust.

As faithful readers of this blog know, I am among those who believe that the null results of our observations of the extraterrestrials should be taken somewhat seriously and life is probably rare. Moreover, life on Earth might have needed some "panspermia" – preevolution on comets or cosmic dust of some kind, just like the working hypothesis behind the Rosetta mission assumed.

The number of similar conditions – what has to happen in the environment for life to collect all the prerequisites to start; and what mustn't happen if the life is supposed to survive for a long enough time – may be rather high and it may reduce the estimate of the density of complex living civilizations by orders of magnitude and perhaps dozens of orders of magnitude. The number of promising galaxies may be much smaller than the 10% announced in the articles above, and the regions of such promising galaxies that are sufficiently hospitable and safe may be very rare, too.

The anthropic principle in the form that prevails in the literature is completely irrational.

But "similar thoughts", while speculative in character and lacking the precision and rigor we expect in physical sciences, could be interesting and could have some true answers. While the anthropic people believe that their principle is trying to maximize the overall number of observers – and that's another reason why they tend to believe, ignoring the observations, that life is literally everywhere (the first reason is that these people are almost always leftists and the idea of life as omnipresent trash seems to strengthen their political prejudices) – I think it is more likely that a similar but corrected principle actually implies that the number of living civilizations is "of order one" in the visible Universe so that our life has barely emerged.

At any rate, if someone is expecting a clear detection of intelligent extraterrestrials within 10 years, I am happy to make a 200-to-1 bet against him or her.

1. Two observations. In our galaxy, there is life. That presumably rules out a GRB event killing it off. So searching in our galaxy makes sense.

Next, the Drake equation. What's missing is a r^-2 term. The probability of detecting life depends on distance.

2. I haven't thought of the Drake equation from that angle before. It really seems to assume that we'd see a civilization emitting radio waves anywhere in our galaxy.

3. Ahh, but for "small" assumption. Proper conclusion should have been: "Life similar to Earth example is likely to be damaged by GRBs in 90% of galaxies". Couldn't there be a life feeding on high radiation that would actually thrive in 90% of galaxies?
Basic physical (entropy must rise and do so through maximum number of microstates) and evolutionary principles combined assure that life of some type, defined as systems of ever increasing complexity, will emerge and self-improve over time anywhere remotely possible, finding basis on which to emerge in local conditions. Adjusting to local conditions and resources. Responding to local catastrophes and adjusting to them, improving. Life and intelligent life defined like that is not rare. Our particular local conditions and type of life are rare (maybe even each type of life itself is rare). But not life in general and intelligent (as self-aware) life. Very basic Physics principle make it inevitable, yes over long time-but inevitable.
Why are we not finding evidence of it? - Because we indeed use anthropic principle and look for human-like intelligence based on DNA-like biology, depending on Carbon/Oxygen/water... We are looking for Star Trek or Star Wars approximations. What is out there is more like Solaris (as one particular plausible example). What would communication even mean to a single, planet sized intelligent organism? (Plausible even in Earth-like conditions as recent finding that life on Earth indeed started as super-organism, freely exchanging and improving DNA and RNA within itself on planetary scale, small change here or there and Earth could turn to have "Solaris" like single planetary organism...). To underline "Solaris" example is there just to underline how completely different a concept of life can be, with infinite other, equally different possibilities out there.
Life and intelligent life is out there in loads but we are the ones looking with blindfolds only for particular infinitensimal example of it that looks like us.

4. Dear Dušane, strong high-energy ionizing radiation is damaging to the stability of any genetic code that would remotely resemble the DNA code on Earth. The survival of complex organisms requires the genetic code to remain sufficiently unchanged for quite some time, and any "qualitative cousin" of the DNA we know is only able to tolerate a certain limited flux.

I think that you misunderstand the relationship between life and entropy. The second law of thermodynamics surely makes it harder, not easier, for life to evolve. The development of organized structures increases the organization and therefore reduces the disorder, a part of the entropy, and it's only possible - allowed by the second law - because a much greater amount of entropy is produced at the same moment, and it's produced because of the thermal gap - few high-energy photons from the Sun are reradiated as many low-energy thermal infrared photons from the Earth. Without this temperature difference similar to the difference between the Sun and the Earth, life wouldn't be allowed.

5. You can't buck r^-2. However you can mitigate it by beaming the transmission.

Problem is, why would anyone beam at us? You would have to know where we are when the signal is received.

6. Europa, one of Jupiter's moon, seems to harvest life in its oceans. They say that there is no more reason to think that there is no life on Europa.

7. Vis-a-vis alien life, one of the terms from the Drake equation that most likely are very small is the probability of life emerging.

I'm talking about the probability of emergence for the first molecules that can self-replicate somewhat reliably.
Darwinian evolution can't help here; you need self-replicating entities for natural selection to operate.

Which leaves only luck.
Let's assume that, for the creation of a self-replicating molecule, one needs 50 environments to follow each other in a precise order (a self-replicating molecule is already VERY complex; I'm being very optimistic).
In this case, the chance of life emerging is lower than 1 in 50! (1 chance in 3,04*10^64).
I said 'lower' because I already assume that each of these 50 environments will appear, that no destructive environments appear between them, etc. On the other hand, there may be more than one way for self-replicating molecules to appear naturally (but there aren't many ways - we know enough chemistry and tried to obtain life in the laboratory for long enough to be all but certain of this).

In any case, there are 10^78 to 10^82 atoms in the observable universe. The vast majority of them forming structures unsuitable for life.
If I were a betting man, I would bet we're the only life that appeared within the observable universe.

8. Earth is in an orbital nice place, it has a magnetic field so its hydrogen is not scrubbed by solar wind (Venus and Mars re deuterium abundance), It has a big close moon to stabilize its spin axis. It enjoys mass extinctions, ice ages; and the Third Word locally and outsourced. Gamma ray burstars toss of a coin are small stuff compared to mandated charity being wholly antithetical to the survival of intelligent life,

http://donsnotes.com/reference/images/pop_growth.gif

9. "...the pedagogical usefulness of the Bell's theorem..."

I think that's a good point.

For people like me (not a physicist) for example, who have only the very barest of cursory acquaintances with QM (state vectors in Hilbert space, observables as operators, measurement as 'collapse' onto an eigenvector of the operator with probability determined by the corresponding coefficient of that eigenvector component of the state vector), Bell's inequality adds a nice topping to further bring home how thoroughly different the ideas in QM are from the notions underpinning classical mechanics.

Just saying ...

10. Regarding pedagogical usefulness, I prefer Hardy's work, Schordinger steering, ghost interference/imaging and Popper's experiment.

11. I never quite got this stability argument and now i found this:

12. Me thinks you might be far too optimistic! ;-)

13. To me, free will has to be a physics issue - were it to exist it would have to act on the world and change something. If the world operated according to Newtonian mechanics, there is very clearly no room for anything like 'true' free will, and emergence couldn't change that.

14. Yes, I was even reading it just before posting. The issue there is that while it disallows hidden variables theories for things like position/momentum, it still takes QM as 'truly random'. Which indeed it should. But that doesn't allow free will in any humanly understood way. The way I have been musing about it is by analogy to energy. In Newtonian mechanics, energy is fixed. In QM, there is allowed some 'give and take', but on average the energy is constant. Now extend that to probability: in QM/ST, probability is taken as a given, but let's imagine that there could be some 'give and take' in that. Could there be some factor that does the choosing of outcomes (let's call it 'William' :) ), so that on average the probabilities come out right, but there may be some skewing allowed. So one day, for the fun of it, William decides that all electrons will be measured with spin up for the day. This skews the probabilities, so that needs to be 'given back' - more electrons must be measured with spin down for the next week in order to bring the probabilities back. This may happen in any case due to pure randomness, but let's give William a bit of extra freedom in the matter. So William is a bit like a hidden variable, but one for probability rather than for giving definite values to observables (which only brings back determinism and no free will anyway). Yeah, yeah, lots of speculation, but with a purpose in mind, and I'm not unaware that it will cause problems elsewhere. I post it here in the hope of knocking it on the head :)

15. Thank you to talk about Shrödinger steering and ghost imaging : both provide nice opportunities to think about QM problems in modern terms and to translate them in interesting experiments where "naive experimentalists can contribute" to quote Alain Aspect.

16. As yet, there is no evidence of life on Europa. And, if I recall correctly, we are not allowed to go there.

17. But SETI is in double trouble because they are selectively focusing on communication with places that seem to be sterile due to this GRB-induced Holocaust.

I haven't yet read the linked articles, but I guess you mean that SETI focuses toward the center of the Milky Way. If that is what you mean, how much difference can it make in GRB effects? I thought SETI was only interested in "nearby" places, say, within 2,000 LY.

18. Which leaves only luck.

I wouldn't bet on that. There may have been a kind of evolution going on, i.e., something with a strong enough "preference" for some of the needed structures to make for a decent likelihood that the needed steps would occur.

19. OK, if one only looked 2,000 LY away, which is a few percent of the radius of the Milky Way, it would only make a few percent difference in the probability of finding life.

But I think that this assumption - that one finds something as close as 2,000 LY away – is rather implausible, a random guess someone made up. For example, some of the famous Kepler planets are over there.

Someone may expect life "really everywhere", so there should be life around these relatively nearby stars, indeed. I don't think it's likely. Looking at a significant fraction of the galaxy may be needed as the minimum, and then one doesn't want to discard the more distant places, and looking towards the center is a O(100%) reduction of the chances.

20. "There are more things [alive] in heaven and earth, Horatio, Than are dreamt of in your [Natural] philosophy" ;-)

21. Angry Safety BillNov 26, 2014, 4:33:00 PM

I always thought anyway that the window for intelligent technologically advanced organic life is very very small before AI comes along and takes over. I bet AI would likely be the kind of life we encounter if any at all.

22. I withdraw the moon-spin convenience and accept other benefits enumerated in the paper. Bottom line: pond scum everywhere, CPUs near nowhere.

Remove the Protestant Reformation and Earth is a forever slum. It was that close. The New World was an aboriginal slum. China was self-contained and starving, Japan was trapped within its own culture. India was hopeless. Catholicism and Islam are express elevators to Hell - and not to the good parts.

23. Well, great, but I think that this might be too Earth-centric view. The life civilizations outside Earth could potentially be so different from ours that you could be unable to say whether they're closer to our biological life or to AI.

If I offer a truly cool ID-like idea, even our biological life could be a "higher level" created as AI by someone more primitive than us. ;-) And whether life uses silicon or carbon etc. could be more variable than we think. On the other hand, our DNA code could be used in the whole Universe, at many other places. We just don't know.

24. DiamondsInTheDevilsBrewNov 26, 2014, 5:44:00 PM

Weren't you banned? Or did you admit to Lubos that your crackpot views of physics are a result of shit in the brain?

25. Would organisms like thermococcus gammatolerans and deinococcus radiodurans be able to survive in environments with frequent GRBs? If so, it seems to improve the odds of life in such extreme galaxies what, since it shows that life could overcome the GRB obstacle in principle. The only problem: sufficient time for evolution. GRBs would have to occur not too often, so some early lifeforms have enough time to evolve radiation resistance.

http://en.m.wikipedia.org/wiki/Thermococcus_gammatolerans

Tardigrades - a form of complex life - have formidable radiation resistance too, although not as much as the earlier mentioned bacteria.

26. There is life, but no intelligent life. ...oh wait a minute, this Europa you mean... Is that an Arthur C. Clarke reference?

27. Unfortunately, the internet amplifies everything, including those things that ought to be attenuated. We are still learning how to deal with the new reality, aren’t we?
I do think that people like your are contributing to the increase in intellectual discrimination that, ultimately, has to be the solution to the problem.

28. Operating within a chaotic world of chance, free will is only free if it's in principle repeatable. That doesn't make it deterministic from low level physics, necessarily. Given the lack of time machines and the fundamental inability to predict chaotic circumstance upon which free will acts, it's not a predetermined world of robots. Being repeatable with the same starting conditions, the same random circumstance doesn't destroy the agency of a conscious participant, necessarily. An emergent system with will can perhaps in principle override mere wiggly quantum and fluid dynamic chaos and have Newtonian physics merely be it's plaything as self-organization reaches very high order mathematical complexity in cause and effect that neither classical or quantum physics has anything goes to do with except as boundary conditions. I am not yet aware of proofs against high order emergent cause and effect, anyway.

29. You are making the same mistakes as Michael Behe does in his ID "irreducible complexity" arguments, which have been definitively demolished in the Dover School Board trial about teaching ID in the classroom (Which the judge called a move of "breathtaking inanity".) Also, you do not need "life" for self-replication to work. Also, natural selection is not based on random luck. A self-replicating molecule in no way has to be "VERY" complex--eg salt crystals. The Drake Equation is vastly over-quoted and entirely ad hoc, and can be used to predict a ridiculous spread in estimates of intelligent life depending on guesses on the frequency of the variables. It reminds me of sociological formulae.

30. Gordon, your post is full of pretty obvious errors:

First - I quite clearly said in my last post you need self-replication for darwinian selection (aka natural selection) to work. Until self-replication appears, you only have luck.
That you managed to misunderstand even this is quite a "feat".

Second - salt crystals can only "self-replicate" a very simple, non-changing pattern.
A self-replicating molecule that could give birth to more complex life through darwinian selection must be able to reliably self-replicate a very large variety of information. And yes, it DOES need to be VERY complex for this (that's why it's so tough to create an artificial one in a laboratory; that's why self-replicating nanites are far beyond our grasp; etc)

Third - I don't know about the "Dover School Board trial" you mention.
It's almost certainly a straw-man on your part (my guess - you confuse the road to the simplest self-replicating molecules with the road from those molecules to more complex life).
But hey - feel free to prove me wrong; present the arguments from those trials.

Fourth - the Drake equation is tangential, at best, to my post. Your opinion of it is, as such, doubly irrelevant.