The relation between physics and biology

… or, The Real Anthropic Principle…

I was musing, as one does, about the relation between physics and biology. Usually we think of biology as some domain that can (or, depending on your personal position, cannot) be reduced to physics. I, on the other hand think of biology, like chemistry, psychology and librarianship, as what physics does in some part of the the universe. This led me to Avoid Work (a technical manoeuvre I often engage in) by doing some simplistic math on the matter.

The Anthropic Principle is basically the claim that the universe is fine tuned to produce life, and intelligent life at that. I wondered how fine tuned. How hospitable is the universe towards life? Basically, what’s the ratio of life-friendliness in the physical world to inhospitability?

We know that the biosphere of earth is roughly a shell of 100km thickness on the earth, from about 20km below sea level to 80km above it. This is, generously, the part of the universe that we know is life-friendly. Taking the volume of the sphere of the earth’s radius plus 80km, and subtracting the volume of the earth’s radius minus 20km, we get 46,412,331,509 km3. Not bad. 46 billion cubic kilometers in which life can exist. What’s the ratio of the observable universe to life-friendly volume?

The observable universe is roughly 8.8 × 1023 km across, so the volume is roughly 3.5 × 1071 km3. The ratio of life to nonlife volume is therefore around 1 in 1.361. It’s pretty much zero. So let’s assume biospheres are common; say, around a billion biospheres per galaxy and a hundred billion galaxies in that space, each around the size of ours. That gives us 4,641,233,150,851,590,000,000,000,000,000 km3. That brings the ratio to 1 in 1.341. Still pretty much zero.

So if biology is what physics does, it’s what physics does in an infinitesimally small part of the universe. On that basis, should we expect biology to have laws like physics? Are there biological universals? Is this the best universe God could have made for life? Does the design argument still make an impact here?

Have fun chewing on that…

16 thoughts on “The relation between physics and biology

  1. watch the sign on your exponents! 1/(1.3 x 10E-61) is actually a pretty BIG number… (and I omit to comment on significant figures.)
    But your point is well taken. As another eminent philosopher has said: “Space is really big.” To a first approximation it’s empty.

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  2. This is all well and good unless you take the Anthriopic Principle to mean that the Universe is fine-tuned so that one planet will produce life in His Image; with all the rest out there to inspire us to be in Awe of His Creative Power.

    Praise FSM.

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  3. The Strong Anthropic Principle takes the “postage stamp at the top of the Eiffel Tower” thinking to even greater extremes of absurdity. If God really was trying to “fine tune” the universe for life, he damn near failed.

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  4. If reality is observed, then of course it is “fine-tuned”, and it is quite probable that it becomes increasingly fine-tuned to favor your existence in your immediate vicinity (in both time and space). And globally, the probability of finding yourself in a universe compatible with your existence is always 1. The real question then, is why everything is being observed from your perspective in the first place, instead of from another location in space and time, or from another universe 😉

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  5. Just a few more things..

    Instead of “if reality is observed”, I should have said “if the universe is observed from within”. An internal observer is subject to the universe’s laws, whereas an external, timeless observer (“God”) is not (although how an external observation could be made without interaction is beyond me). The universe would always appear fine-tuned to an internal observer, even in models where reality is not created or defined by observation.

    On that basis, should we expect biology to have laws like physics?

    I think the only requirement is that biology be consistent with physics, and vice versa. Even from a non layer-cake-reductionist perspective, everything should still be consistent with everything else, observations, models, etc (and don’t ask me to define “consistent”). But to a strict reductionist, all biology (and everything else, for that matter) must be reducible to physics, which would have fundamental laws that are not explainable or reducible any further (not my style anymore). I don’t know, I would think that formulating biological laws that resemble physical laws would be highly problematic from a practical standpoint alone – how would you devise complex experiments that “prove” an evolutionary or biological law over the very long term? The possibilities of biology, like thought itself, are endless.

    Is this the best universe God could have made for life?

    That seems like a highly subjective question. Define “best”.

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  6. …all that empty space just accentuates how important we are, don’t ya know! (And I think y0u know who I mean by “we”!)

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  7. If you look at how things work in the depths of the cell (even prokaryotes), you see the tremendous dependence living systems have on exactly how quantum physics manefests atoms: how electrons in their shells relate to one another. It’s easy to decide that unless all sorts of specific detailed physical laws were exactly the way they are, it wouldn’t be possible for life to work at all. This, I think, is the most important way in which “life reduces to physics”.

    In fact, IMO such a belief is invalid: it may be that out of all the 10^xxx ways quantum physical laws could work, there are 10^(xxx-10) combinations of laws that would support life, in which case 1 out of 10,000,000,000 possible universes would support life. Or possibly 1 out of 10,000.

    Either way, the anthropic principle still applies: our form of life finds the universe friendly because we’re adapted to it, but that would be true of intelligent life in any universe capable of supporting life.

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  8. The Anthropic Principle is basically the claim that the universe is fine tuned to produce life, and intelligent life at that.

    This statement is incomplete because the physics indicates that the universe is fine-tuned to evolve to produce life over a specific region of the observed universe, and at a equally specific time in its history.

    I wondered how fine tuned. How hospitable is the universe towards life?

    The intelligent move here would be to find out, before speculating:

    http://evolutionarydesign.blogspot.com/2007/02/goldilocks-enigma-again.html

    But… you didn’t.

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  9. This is a good one. Intelligent Design advocates would have us believe the universe is fine tuned (yet massively under utilized) on one hand yet argue that ID predicts ‘No Junk DNA’ in the other.

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  10. I vividly recall my sudden impact with the notion that if you picked a random point in the universe and immediately went there you would die.

    Few people understand not only how stupefyingly big this place is but how heartbreakingly big it is. Any location conducive to life is vanishingly small compared to those locations that are not.

    And yet, the events that happen to us everyday, the people we meet and the ideas we exchange, giving us at least some measure of accomplishment, are similarly improbable.

    It might be said that life thrives in the narrow spaces, between the error bars, in the noise.

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  11. At least it seems like planets are a lot more common than previously thought, and some of those are probably something like Earth… But yeah, even if there were 100,000 Earths, it wouldn’t make much of a dent in the universe as a whole.

    This is exactly correct, and is the reason why the bio-orientation of structure defining features of the universe is indicative of a structure principle that includes carbon based life relevantly into the path of least action.

    The link that I previously referred explains exactly how the “Goldilocks Enigma” that you refer to, makes falsifiable predictions about where and why life will and will not be found elsewhere in the observed universe.

    Like, life, (past or present), will not be found on Mars nor Venus, but it will be found in other galaxy systems along the layer of spacetime that makes-up the habitable zone. Venus suffers from the runaway greenhouse effect, whereas Mars represents the cold stagnate proof of what will happen if extremist environmentalists get things all their way too.

    http://www.astronomynotes.com/solarsys/s9.htm

    In the mean time, John should read this:
    http://www.ontheknol.com/frontpage-knol/the-anthropic-principle

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  12. Not that it would fundamentally change the calculations, but there may be other areas of this giant universe that are conducive to life. At least it seems like planets are a lot more common than previously thought, and some of those are probably something like Earth… But yeah, even if there were 100,000 Earths, it wouldn’t make much of a dent in the universe as a whole.

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