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Sean's SAP post seems oddly shallow-what's happening?

  1. Aug 9, 2007 #1

    marcus

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    Sean's SAP post seems oddly shallow--what's happening?

    This post over at Cosmic Variance blog.
    BTW currently it says discussion will be closed on 6 September (but those time limits sometimes get extended.)

    ==quote==
    Unusual Features of Our Place In the Universe That Have Obvious Anthropic Explanations
    Sean at 5:02 pm, August 7th, 2007

    The “sensible anthropic principle” says that certain apparently unusual features of our environment might be explained by selection effects governing the viability of life within a plethora of diverse possibilities, rather than being derived uniquely from simple dynamical principles. Here are some examples of that principle at work.

    * Most of the planetary mass in the Solar System is in the form of gas giants. And yet, we live on a rocky planet.
    * Most of the total mass in the Solar System is in the Sun. And yet, we live on a planet.
    * Most of the volume in the Solar System is in interplanetary space. And yet, we live in an atmosphere.
    * Most of the volume in the universe is in intergalactic space. And yet, we live in a galaxy.
    * Most of the ordinary matter in the universe (by mass) consists of hydrogen and helium. And yet, we are made mostly of heavier elements.
    * Most of the particles of ordinary matter in the universe are photons. And yet, we are made of baryons and electrons.
    * Most of the matter in the universe (by mass) is dark matter. And yet, we are made of ordinary matter.
    * Most of the energy in the universe is dark energy. And yet, we are made of matter.
    * The post-Big-Bang lifespan of the universe is very plausibly infinite. And yet, we find ourselves living within the first few tens of billions of years (a finite interval) after the Bang.

    That last one deserves more attention, I think.
    ==endquote==
    For starters here's a little semantic point. By googling "selection effect" one can learn, e.g. from Wikipedia, that:
    SELECTION EFFECTS DONT GOVERN the viability of life
    on the contrary, THE VIABILITY OF LIFE GOVERNS certain kinds of SELECTION EFFECTS
    .
    And selection effects are a source of error in human reasoning---they are not physical effects occurring in nature.
    I'll get to that in the second post and give some sources.

    Then just as a general observation, should this proposed "SAP" be called the Shallow Anthropic Principle, or would it be more accurate to call it the Silly Anthropic Principle? Does this post have any scientific content? Would someone like to interpret?

    It begins with a false dichotomy "... explained by selection effects governing the viability of life within a plethora of diverse possibilities, rather than being derived uniquely from simple dynamical principles."

    Let's compare apples with apples---don't say "derived uniquely" in one case and simply "explained" in another. Lets put it fairly:

    certain apparently unusual features of our environment might be explained by selection effects governing the viability of life within a plethora of diverse possibilities, rather than being explained from simple dynamical principles.

    This is still not straight-talk. "Selection effects" as ordinarily understood do not "govern the viability of life". PHYSICS governs the viability of life, however you define it.
    Life is a physical phenomenon and, however you define it, will be subject to limitations as to environment.

    There is no dichotomy between explaining by whatever effects govern the viability of life, and explaining by simple dynamical principles.
    ===============

    ORDINARY PHYSICS (and derived chemistry) can explain why one can expect to find life more where there is a rich chemistry and phase structure (solid liquid gas). Some places are too hot or chemically too monotonous or too limited in phase structure for one to expect life. If one found some analog of life existing in the sun, it would be unexpected and one would be surprised.

    So the beginning of the post has a certain sleaz- or sloppiness----it begins by taking certain cases of explanation by simple dynamical principles (governing viability of life) and RENAMING them explanation by "sensible anthropic principle".
    Then it declares a false contrast between the two kinds of explanation (one of which has a phony name and actually a case of the other.)

    ========================

    once past the initial false dichotomy one sees 9 statements. The first 8 seem shallow or trivial to me. Maybe someone would like to explain why they are not explainable by ordinary dynamical principles, to whatever extent they need explanation.

    There is, after all, a search for extrasolar planets going on motivated in part by curiosity about extrasolar life. For good physical reasons, one wants especially to find rocky watery exoplanets because one expects them to harbor life with greater liklihood than other planet and nonplanet environments. Whatever life is, people consider it more apt to be found (if at all) in rocky habitable-zone wet places.
    And one reads of people already deciding on what signatures to look for.

    Each of those first 8 question strikes me as a self-absorbed way of phrasing a practical question. Practical versions of the questions are, for instance:

    Why should we look for life on habitable zone planets instead of on the surfaces of stars?

    Why would we look for life-signs on rocky terrestrial-size planets instead of on gas giant planets?

    Why would we look for life at planetary systems around stars, instead of in interstellar space, or even intergalactic space?
    ==============
    BECAUSE FOR SIMPLE PHYSICAL REASONS WE ARE MORE LIKELY TO FIND IT THERE.
    ("It's the Chemistry, duh")
    Formulated as a question of how you spend research money, and observatory time, there are direct answers.

    But the SAP post phrases these questions like the child's question "WHY AM I ME" appealing to everyone's latent narcissism.

    "Why do I live here instead of on the sun? The sun is so much bigger, Mommy!"

    "Why do I live here instead of on Jupiter? Jupiter is bigger, isn't it, Dad?"
     
    Last edited: Aug 9, 2007
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  3. Aug 9, 2007 #2

    marcus

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    I googled "selection effect" and got this Wikipedia entry
    http://en.wikipedia.org/wiki/Selection_bias

    "Selection bias is a distortion of evidence or data that arises from the way that the data is collected. It is sometimes referred to as the selection effect. The term selection bias is most often refers to the distortion of a statistical analysis, due to the method of collecting samples. If the selection bias is not taken into account then any conclusions drawn may be wrong."

    Does anyone have another online dictionary or encyclopedia reference?

    I'm not completely satsified with this Wikipedia definition---I might like it better if it explicitly included the UNCONSCIOUS bias arising from the observer's circumstances.

    How about this: A selection effect is a skewing of the observer's picture that arises from an unrepresentative sample---which could occur unintentionally because of who and where he happens to be.

    I'm not sure. Maybe someone else can offer a better. What I do feel sure about is that you can't honestly say
    "selection effects governing the viability of life" in various environments because
    SELECTION EFFECTS DONT GOVERN the viability of life
    on the contrary, THE VIABILITY OF LIFE GOVERNS certain kinds of SELECTION EFFECTS
    .
    the physical possibility of the physical phenomenon of life, restricting it with high probability to limited circumstances, will in part govern what we see when we wake up.
    we are fairly likely to be on a planet with plenty of different chemical elements and enough gravity to keep an atmosphere so that water can be liquid.
    ==========================

    I also don't like that "apparently unusual" in Sean's SAP post. Why wasn't I born in intergalactic space, Mommy? There is SO MUCH MORE SPACE out there between galaxies!
    That kind of reasoning depends so much on the PROBABILITY MEASURE that one puts on the space of possibilities. If one choses a frivolous or naive probability measure to begin with, one gets a silly result. In fact results can vary wildly.

    The first 8 questions do not strike me as science---but as a kind of candy for the imagination. What is going on? It sounds like soft-core propaganda for something. For what? Why should Sean (who used to be thought of as a scientist) be peddling kindergarten versions of Anthropery?

    Does anyone have any explanation or comment? Am I the only one who is troubled by this CosmicVariance post?
    =================
    Bee Hossenfelder had a pithy comment here
    http://www.math.columbia.edu/~woit/wordpress/?p=582#comment-27314
    that I find relevant:
    ...What I notice - and what I welcome - is that there is more discussion about the question what is science, pseudoscience, and where we are headed. I find that a healthy development. I hope there will be a practical outcome of that which allows researchers to refocus their efforts on real science, and not to waste time on politics, networking, or advertisement. One has to ask why pseudo-scientific ideas gain popularity. Because they are cheap to produce and they sell well. It’s the Walmart of science. You get everything, it looks okay, but if you try to use it will fall into pieces.
    ================

    George Orwell has a great essay called Politics and the English Language about how the corruption of language, the distortion of the meanings of words, can make for a decline of politics.
    One thinks of current leaders with their slogans and clichés manufactured by Think (about how to lie effectively) Tanks.
    Maybe we need an essay on Science and the English Language.
    Bee just needs a little more experience---maybe by the time she is 50 she will be able to write one.
     
    Last edited: Aug 10, 2007
  4. Aug 9, 2007 #3

    marcus

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    the special case of puzzle #9

    #9 is different because it is a TIME question. The other questions had obvious practical correlatives "where would you point your telescope to look for life" because they were essentially WHERE problems.

    The reason you point your telescope at a wet rocky is not "because we exist" or "because of the Anthropic Principle". That would be a sappy answer. You point your telescope at a wet rocky because that's where you expect to have the most chance of finding life. There are sound dynamical principles underlying this---so it seems like a soft-sell for some grander version of Anthropery to give the Anthropic name to this case of straight physics.

    That covers the first 8 examples, but now we have a TIME example, the ninth one.

    "The post-Big-Bang lifespan of the universe is very plausibly infinite. And yet, we find ourselves living within the first few tens of billions of years (a finite interval) after the Bang."

    Personally I don't find this an unlikely time to be alive. I would say that on good physical grounds.
    This is as likely a time as any other and a lot more likely than some.
    I expect the universe will be cold dark and virtually uninhabitable in its old age.

    So what's the problem? Charles Lineweaver has an interesting recent article that goes quite a bit further than I need to go here. According to him the ILLUSION OF UNEXPECTEDNESS of a certain "cosmic coincidence" was caused by a selection bias. And he explains the coincidence away as something that 68 percent of all observers would see----not unusual after all.

    http://arxiv.org/abs/astro-ph/0703429
    The Cosmic Coincidence as a Temporal Selection Effect Produced by the Age Distribution of Terrestrial Planets in the Universe
    Charles H. Lineweaver, Chas A. Egan
    (Submitted on 16 Mar 2007)

    "The energy densities of matter and the vacuum are currently observed to be of the same order of magnitude: [tex](\Omega_{m 0} \approx 0.3) \sim (\Omega_{\Lambda 0} \approx 0.7)[/tex]. The cosmological window of time during which this occurs is relatively narrow. Thus, we are presented with the cosmological coincidence problem: Why, just now, do these energy densities happen to be of the same order? Here we show that this apparent coincidence can be explained as a temporal selection effect produced by the age distribution of terrestrial planets in the Universe. We find a large ([tex]\sim 68[/tex] %) probability that observations made from terrestrial planets will result in finding [tex]\Omega_m[/tex] at least as close to [tex]\Omega_{\Lambda}[/tex] as we observe today. Hence, we, and any observers in the Universe who have evolved on terrestrial planets, should not be surprised to find [tex]\Omega_m \sim \Omega_{\Lambda}[/tex]. This result is relatively robust if the time it takes an observer to evolve on a terrestrial planet is less than [tex]\sim 10[/tex] Gyr."


    This is an example of what I would call a good SCIENTIFIC use of the term selection effect. Someone might come and say "ISNT IT SURPRISING that we live right when matter is 27 percent and dark energy is 73 percent, so they are roughly same order of magnitude? What an amazing coincidence!"
    Lineweaver says it is not at all surprising, on the contrary, it is VERY LIKELY, based the simple dynamical principles of physics.
    Stars take a while to coalesce, planets take time to form, life takes time to evolve, and then stars and planets die.
    There are apt to be MORE observer-planets now than there will be much later and that there were much earlier.
    They find 68 percent probability that if an observer wakes up somewhere in the universe he will be in a timeframe that puts matter and dark energy at least as close as they are now

    So we are finding that such and such that we THOUGHT was an unlikely coincidence is not, after all, uncommon. Thinking it was unusual was a mistake caused by a selection bias, or selection effect.

    Notice that the selection effect does not GOVERN physics. The illusion or fallacy of thinking there was an odd circumstance was a selection effect. the physics of stars and biological evolution set us up to have this selection effect delusion. Which Lineweaver and Egan now have dispelled.

    =======================

    Larry Krauss has a neat paper about how this is a good time to be alive and to be studying the universe.
    Because of how dismal the (LambdaCDM) universe will get later on, and how hard to study as a cosmologist. In the future the clues like redshifted galaxies and the CMB will fade out of sight. With all the light around it's not surprising to have eyes.
    With all the good energy food around it's not surprising that we are hungry active animals. With all the good information about the universe around it's not surprising we are curious and ask questions.

    http://arxiv.org/abs/0704.0221
    The Return of a Static Universe and the End of Cosmology
    Authors: Lawrence M. Krauss (1,2), Robert J. Scherrer (2) ((1) Case Western Reserve University, (2) Vanderbilt University)
    to appear, GRG October 2007;
    (Submitted on 2 Apr 2007)

    "We demonstrate that as we extrapolate the current LambdaCDM universe forward in time, all evidence of the Hubble expansion will disappear, so that observers in our "island universe" will be fundamentally incapable of determining the true nature of the universe, including the existence of the highly dominant vacuum energy, the existence of the CMB, and the primordial origin of light elements. With these pillars of the modern Big Bang gone, this epoch will mark the end of cosmology and the return of a static universe. In this sense, the coordinate system appropriate for future observers will perhaps fittingly resemble the static coordinate system in which the de Sitter universe was first presented."
     
    Last edited: Aug 10, 2007
  5. Aug 10, 2007 #4
    Marcus,
    I think, you are a little bit too strict with Sean here.
    Describing the selection effect as an actor for me is like saying, a chess program doing this or that move is following this or that plan. We know, that in reality it is only a computer program executing a certain algorithm, but it is a convenient standpoint. But wait, ins't software just an illusion, and ultimately it is the CPU following the rules of electromagnetism and quantum mechanics?
    I think in the end looking at different levels of description only God knows, which perspective is ultimatively the right one, if any. Meanwhile, at a certain time we choose the most convenient one.

    I also think, Sean would even agree, that what you describe here, are promising applications of the anthropic principle.
     
    Last edited: Aug 10, 2007
  6. Aug 10, 2007 #5

    marcus

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    Thanks for comment, Micha. Perhaps I am.

    But I would not agree that the Lineweaver and Egan paper are any sort of application of the anthropic principle at all (promising or not promising :smile:)

    Or Larry Krauss paper either---he is just predicting what the old dark universe will be like for cosmologists (dismal, dull, difficult to read)
    We are living in a very rich information environoment with the cosmic microwave background and huge numbers of redshifted galaxies. By Krauss paper we should break out the champagne and celebrate. It won't always be this good!

    But I do not see that either paper applies any kind of anthropic principle.
    they just take careful account of the one sole reality we have.
    And they provide no excuse for giving up trying to explain anything that needs explaining!

    It sounds as if you liked the two papers that I mentioned. I'm glad. I do too :cool:
     
  7. Aug 11, 2007 #6

    Chronos

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    Sean is a jokester at heart. I think he was poking fun at the dragon.
     
  8. Aug 12, 2007 #7
  9. Aug 12, 2007 #8

    marcus

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    thing is, Sean is a charmer and I think maybe he defines science cool for a significant flock of admirers.
    people act as if one flash of the boyish smile and they're inclined to forgive him pretty much anything

    but lately he seems to have taken over the role of apologist for string and I don't think he really KNOWS the string situation well enough to be good at that, plus my impression is his recent research quality is not as good as it used to be----fewer citable papers.

    his current direction worries me. I wish he would stay off the Anthropic Principle----even flirting with this innocent seeming kindergarten version which is just a renaming of some regular physics, but which still is worrisome.
    there is enough semantic grease in how he introduces it to make me think it's the "nose of the camel" that one should not let in under the tent.

    I wish Sean would forget string/philosophy and concentrate on doing cosmology.

    For example, right now I think the leading non-string and non-loop cosmologist is Reuter and there is a big question of where Reuter's universe comes from. The big bang of Reuter's universe is very interesting. Sean could, for instance, take a look at it.
    Reuter's preprint of 3 June cited Sean, which he didn't have to---just took the paper as an e.g. Maybe that's an invitation.
     
    Last edited: Aug 12, 2007
  10. Aug 13, 2007 #9

    marcus

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    Here's a nice article by George Ellis

    http://arxiv.org/abs/gr-qc/0102017
    Cosmology and Local Physics
    George F R Ellis
    20 pages, Int.J.Mod.Phys. A17 (2002) 2667-2672
    (Submitted on 5 Feb 2001)

    "This article is dedicated to the memory of Dennis Sciama. It revisits a series of issues to which he devoted much time and effort, regarding the relationship between local physics and the large scale structure of the universe - in particular, Olber's paradox, Mach's principle, and the various arrows of time. Thus the focus is various ways in which local physics is influenced by the universe itself."

    It has a nice bit about the various versions of A. P. (including the C. R. type)

    I like George Ellis. He co-authored the classic Hawking and Ellis book
    and Elsevier asked him to do the Cosmology article for their philosophy of physics Handbook
    he's deeper than a lot. thinks very clearly and carefully. really like him.
    have to go, back later

    ============================
    REPLY TO TURBO'S NEXT POST---post #10

    Turbo, thanks so much for taking Sean's list of "Anthropics" seriously enough to think them over! We owe that to him. I just glanced briefly but it seemed to me that it is just as you say---the first 8 are straightforward. One can derive them from simple dynamical principles WHICH IS WHAT SEAN IMPLIED ONE COULD NOT.
    More exactly one can find good physical reasons why one is more LIKELY to find life (however reasonably defined) in those places.

    So Sean's post is really dumb and perhaps, as Chronos suggested, it is just a really dumb JOKE. Charming as always, he has now made a big fuss about perverted sexual fetishes, masturbation, scrambled eggs and Entropy---so everything is back into safe territory and it would be uncool to take anything seriously right now.

    But even if the floor is covered with bananapeels we should take this stuff seriously once in a while and you did!

    BTW you say z = 6.5 and I (courtesy NW Cosmocalculator) translate that to 860 million years after bang----almost a billion years. That agrees with what you say "a few hundred million". You ask about metals that quick. I picture big stars hustling to rustle up the metals. Somebody has to get up early in the morning to light the fire and get the bacon cooking and the coffee boiling. :smile: I feel I just don't know enough about early structure and starformation to discuss with you. I can only just sort of register what you say.
    ======================

    OFF-TOPIC COMMENT EDIT:
    http://www.sciam.com/article.cfm?chanId=sa003&articleId=4C44B8D3-E7F2-99DF-3D03439C08E85464
    SOME GOOD NEWS ABOUT FERRETS
    north american blackfooted ferret had a close call but is coming back (PF news clipping)
     
    Last edited: Aug 14, 2007
  11. Aug 13, 2007 #10

    turbo

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    Marcus, I've been mulling this over and it seems that all but the last example in Sean's list can be explained by our nature. We are complex carbon-based life forms that arose from precursors that seemed to require the existence (at least part of the time) of water in its liquid phase. Our existence relies on the availability of a metal-enriched environment, so a galactic crucible is required and the necessity for liquid water implies that we must live on a rocky planet with a protective atmosphere. As for complex life being formed from theoretical entities like DM and DE, those are not viable arguments for any form of anthropic principle. Same with the example of why we are not made of photons or hydrogen and helium. Photons are a great way to transfer energy, but it is difficult to envision them forming a coherent structure naturally, much less coalescing into something that even resembles life.

    The last example is based on the assumption that the BB theory is viable, but as we push back to higher and higher redshifts, observations are providing severe constraints on that theory. Here is is a presentation given by Michael Strauss (science spokesperson for the SDSS team) at the Space Telescope Science Institute. If the Universe is only 13.8 billion years old, there are some SDSS obvservations that need to be explained.

    1) Quasars at z~6.5 exhibit Solar or super-Solar metallicities. How did these metals form and accrete only a few hundred million years after the BB?

    2) Quasars at high redshift show no evolution in relative or absolute metallicity with redshift. They also show no evolution in any other quality that the SDSS team could measure. This was not expected, as the BB theory requires an early era in which metallicities are low and evolve over time. Strauss points out that since metals are expected to be generated from different time-related processes, some evolution in relative metallicity should be evident at this epoch.

    3) Since luminosity falls off as a function of the square of the distance to the emitter, if quasars are accreting BHs, they (the z~6.5 quasars) most be comprised of BHs of up to ten billion Solar masses consuming host galaxies of up to several trillion Solar masses. If structure in our universe forms through gravitational accretion, where are the hyper-massive galaxies and hyper-massive BHs at lower redshifts? Did they simply evaporate or disintegrate? It may be time to reconsider the idea that Gamow was wrong and that the universe may be spacially and temporally infinite.

    Click the link and scroll down to Nov 2.
    http://www.stsci.edu/institute/itsd/information/streaming/archive/STScIScienceColloquiaFall2005/

    This presentation should be required viewing for every cosmological theorist.

    Edited link, corrected a misspelled word, and added a parenthetical clarification regarding the hypermassive quasar puzzle in Strass' presentation.
     
    Last edited: Aug 14, 2007
  12. Aug 14, 2007 #11
    Hi turbo-1,

    Excellent points. I would not like to comment on that post by Sean Carroll so I'm glad that you did it here. I can only say that, at least *my* approach is -- the so many open questions in cosmology, as hard as they may seem, are to be addressed by PHYSICS. I see no compelling reason to give up on good old science and appeal for anthropic arguments in order to reason about those problems.

    BTW the link you mention does not find Michael Strauss' presentation...

    Best,
    Christine
     
  13. Aug 14, 2007 #12

    turbo

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    Thank you, Christine. I have fixed the link. STSI apparently restructured their archives, so my old bookmark was out of date. I have watched Strauss' presentation at least a dozen times - it's a great talk.

    Like you, I have a hard time understanding how people can appeal to the anthropic principle and hope to gain any insight into the fundamental questions facing us. Let us imagine that today is your birthday and you were born 30 years ago, and as you prepare to board a bus to work, you notice that the license plate on the bus reads "081477". If that happened to me, I would probably just smile and say "what a neat coincidence" - I certainly would not attribute enough significance to the event to bother trying to calculating the odds against that coincidence. Anthropic arguments regarding the "coincidence" of our existence seem equally empty to me.
     
    Last edited: Aug 14, 2007
  14. Aug 14, 2007 #13

    turbo

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    I almost missed your comment in that time-warp edit. :smile: Whether or not Sean was serious when he posted that list of "coincidences", other prominent theorists have dabbled with the AP, too, so I at least try to give their arguments some consideration. So far, I haven't been swayed by any version of the AP.

    As noted above, I fixed the link to Michael Strauss' presentation at the STSI, and if you've got the bandwidth to stream video, it is a must-see. His description of SDSS's quasar-search methodology is very straightforward and interesting, but the real treats are in the questions that the SDSS observations raise. He explains why the observations are difficult to explain in the framework of BB cosmology, and he does so in terminology that is easy to grasp.
     
  15. Aug 14, 2007 #14
    Hi Turbo-1!

    Thanks for fixing the link, I'll take a look opportunely.

    Concerning your view on the anthropic principle, I agree with you 100%.

    Ha ha...:biggrin: You see: for a coincidence (inside a coincidence), in your random example you missed the right date for just two wrong digits. The day is correct, the month is 5 integers ahead and the year is wrong by one digit. I'd almost look for an anthropic argument for this... :biggrin:

    In fact my birthdate is the same as Einstein's (14 March). Surely there must be an anthropic explanation for this as well...:tongue2:
     
  16. Aug 14, 2007 #15

    turbo

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    Oh, no! Einstein died on my 3rd birthday! (no kidding) See how the universe has conspired to tease us. I don't recall being particularly concerned at the time, though. :rofl:
     
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