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  • The Anthropic Principle: Reading Only

    • The anthropic principle is a peculiar example of an emergent principle---an example that is when using the general broad definition of emergence yours truly adopts (see above subection Defining Emergence) since yours truly thinks it will exist in any imaginable relatively complex universe.

    We discuss it in here in IAL 0 because it's a bit philosophical and does NOT fit anywhere else in IAL.

    The term anthropic principle was coined in 1973 though the idea of such a thing goes back to 1904 (see Wikipedia: Anthropic principle: Origin) and perhaps earlier in a vague sense.

    The anthropic principle has been controversial: some argue that it is trivial or worthless as a scientific prinicple.

    Part of difficulty in assessing the value of anthropic principle is that there are different versions of it, and so its value is version dependent.

    However, it seems a basic anthropic principle has gained traction and is of some importance in modern astronomy and physics.

    Put as an aphorism, the anthropic principle states:

    See Orson Welles (1915--1985) observing in the figure below (local link / general link: orson_welles_chimes_at_midnight_a.html).

    1. An Explication of the Anthropic Principle:

      An explication anthropic principle that seems generally acceptable is as follows:

      Some conditions of the observable universe have to exist or there would be NO observers to observe them.

      That there are observers is a partial explanation for those conditions.

      The observers can be specified in different ways:

      1. Humans.
      2. Technologically advanced intelligent life as we know it.
      3. Intelligent life as we know it.
      4. Life as we know it.
      5. Anything characteristic of the observable universe.

      However, most people it seems choose life as we know it, and so "biotic priniciple" would be a better name than anthropic principle.

      The reason for choosing life as we know it is that life as we know it seems to be ineluctable in the observable universe (unlike humans who are obviously eluctable) and specifying the necessary conditions for life as we know it seems a lot easier than for technologically advanced intelligent life as we know it or intelligent life as we know it. The 5th catetory seems to be broad to be interesting.

      The anthropic principle would obviously be very useful if allowed you to discover something about the observable universe that you did NOT know before---it would then be a DISCOVERY TOOL For example, you had never noticed A, but then you realized there had to be A for life as we know it to exist and then you looked for A and discovered it.

      But that the anthropic principle has ever been a DISCOVERY TOOL in any important way is controvsial.

      section UNDER RECONSTRUCTION BELOW

    2. The Anthropic Principle and the Multiverse:

      For yours truly and many others, the most important anthropic principle possible discovery is of multiverse.

      The theory of the multiverse itself branches into quasi-infinite varations, but one version in short it is the idea that there are other realms of existence where the laws of physics differ from those of the observable universe. These other realms may be just far away in space outside of the observable universe or maybe far away in time or both or just detached from observable universe An possible argument from the anthropic principle for the multiverse goes as follows:

      1. Say hypothetically the laws of physics as relationships are determined by ineluctable logic. This may NOT be true, although it is arguable true for the 2nd law of thermodynamics.
      2. But the fundamental physical constants (e.g., vacuum light speed c = 2.99792458*10**8 m/s = 2.99792458*10**5 km/s (exact) ≅ 3*10**5 km/s, gravitational constant G = 6.67430(15)*10**(-11) (MKS units), Planck's constant h = 6.62607015*10**(-34) J·s = 4.135667696 ... *10**(-15) eV-s (exact)) in whatever units you write them in seem to have NO their values have obvious relationships to each other. EXCEPT their values allow life as we know it in the observable universe and other values differ to some degree or another do NOT But how much they have to differ is itself a fraught discussion among the great brains.
      3. So the values of the fundamental physical constants are what they are in a partial explanation because life as we know it exists.
      4. So the argument goes, there must be multiverse where the fundamental physical constants are chosen from some probability distribution. Most other realms of existence are probably lifeless.
      5. Like many others, yours truly finds this anthropic principle argument and variations on it plausible, but that is all.
      6. But even conceding the argument and variations on it are plausible, all you get from the anthropic principle is a very limited multiverse. theory. There is NO guidance for further development of the theory.
      7. Some people think the multiverse theory is NOT worth talking about any further from anthropic principle reasoning. The anthropic principle has given us little and will give us nothing more.
      8. Can the multiverse theory be further developed without the anthropic principle? Yes. If a wonderful fundamental physical theory was developed that explained everything we observe (i.e., a theory of everything (TOE)) and it implied multiverse, then would a very plausible reason for believing in it and maybe allowing further development. But this wonderful fundamental physical theory would owe little or nothing to the anthropic principle.
      The above argument is just an example of the kind of arguments from and over the anthropic principle.
    3. The Conditional Probability Proof of Existence:

      Say you have events A and B and

            P(B|A) = probability of B given A = 1    ,

      then B must exist if A exists.

      On the other hand, you know nothing about B if A does NOT exist. It could exist or NOT.

      And P(A|B) (i.e., probability of A given B) is also unknown.

      The equation P(B|A) = 1 is the general essence of the anthropic principle.

      It applies to anything. A does NOT have to be humans or living beings at all.

    4. The Basic Idea of the Anthropic Principle:

      The essence of the anthropic principle is "we" (and "we" in general is anything existing) is A and if P(B|A) = 1, then B must exist.

      In other words, A exists implies B exists.

      What's B? Any of a vast number of things that are necessary for A to exist. We give one famous example of B below in subsection Anthropic Principle Example: The Triple-Alpha Process.

      What's A? There are many possibilities. Possible A values relevant to human (which are the ones usually considered when discussing the anthropic principle) roughly in order of increasing generality are:

      1. Technologically advanced intelligent extraterrestrial life / Technologically advanced human society as we know it or in any possible formulation.
      2. intelligent extraterrestrial life / human life.
      3. life as we know it.
      4. life.
      5. liquid water.
      6. water.
      7. carbon.
      8. hydrogen.

      Interestingly, there is historically a forerunner of the anthropic principle in Aristotelianism. To explicate, Aristotelianism considers A to be a final cause of B since B exists, among other things, to make A possible.

      This Aristotelian teleological point of view is useful in some contexts (e.g., things designed by intelligence or evolution), but probably NOT many others.

      An example from evolution is that animal flight (i.e., A) is the final cause of wings (i.e., B). But, of course, wings can and do exist without animal flight. However, wings used in or once used in animal flight did evolve the way they did for animal flight.

    5. The Anthropic Principle Redux:

      In the subsection below, we give a famous example of the application of the anthropic principle used as a discovery tool.

      There were more examples once, but enough is enough.

    6. Anthropic Principle Example: The Triple-Alpha Process:

      Probably the most famous example of the use of anthropic principle was in the discovery of the triple-alpha process in 1952.

      Recall, the term anthropic principle was coined in 1973. So only retrospectively has the term been applied to this discovery.

      The story in point form:

      1. Life as we know it requires carbon.

      2. Carbon is the only atom out of the whole periodic table (see figure below: local link / general link: periodic_table.html that permits complex molecules (i.e., organic molecules) needed for that complex structure life as we know it.

      3. Since carbon exists in the observable universe, there must be some way to make it in observable universe Big Bang---which did NOT make any carbon---or in the steady state universe (viable 1948--c.1961) which posited only a steady creation of hydrogen.

        In 1953, the Big Bang theory (then very rudimentary compared to today) and the steady state universe were considered the most---maybe the only---viable cosmological models.

      4. But nuclear physics in 1953, knew of NO process to make abundant carbon in stars where most elements were thought to be synthesized.

      5. Fred Hoyle (1915--2001) in 1953 hypothesized that a process with special properties, now called the triple-alpha process (see figure below: local link / general link: triple_alpha_process.html), had to exist since abundant carbon exists and we need that to exist (see Wikipedia: Triple-alpha process: Discovery).

        In other words, an anthropic principle argument argued for the triple-alpha process---and, as aforesaid, this was before the expression anthropic principle was coined in 1973 (see Wikipedia: Anthropic principle: Origin).

      6. The triple-alpha process was soon discovered soon thereafter experimentally.

      7. So the anthropic principle allowed us to discover something we didn't know existed before---the triple-alpha process.

      8. Note that we imply the existence of carbon, but carbon doesn't imply the existence of us.

      9. All kinds of life could exist in a universe with carbon.

      10. Many of our peculiarities are the result of random events particularly in the evolution of life on Earth.

        The properties of the winners of a lottery are quasi-unique due to random peculiarities, but there are always winners of a lottery.

      11. The anthropic principle can used to infer the causes or the probable causes of properties of us that are NOT just due to random chance.

    7. Extending the Anthropic Principle

      What if A exists, but P(B|A)∈(0,1).

      Now you only know that B could exist. You could still search for B if P(B|A) is estimated to be large enough for the search to be worthwhile.

      The formula P(B|A)∈(0,1) can be called the extended (general) anthropic principle.

      Searches for B given P(B|A) siginificant probably go on all the time without bother to use the name anthropic principle.

    8. The Anthropic Principle: Is it a Useful Scientific Principle?

      The subsections above show that yours truly's opinion that the anthropic principle is a useful scientific prinicple in both explaining in a sense why things are as they are and sometimes as a discovery tool.

      There are criticisms of the anthropic principle (Wikipedia: Anthropic principle: Reception and controversies), but yours truly thinks those are mostly directed toward more extravagant claims for it than those discussed here.

      In IAL, we occasionally refer to the anthropic principle.