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?"