Granted absolutely that slightly different constants would produce radically different universes. Often ones in which nothing, not even matter or energy as we recognize the ideas, could exist.
Where the Strong and Ridiculous anthropic principles go increasingly off the rails IMO is where they posit the necessity that some even higher level meta-force is causing universes to be created that *necessarily *have matter-compatible or life-compatible parameters. That’s simply Man as God’s Chosen Center of the Universe thinking updated to 20th century terminology. IOW, bunk.
The key recognition is one of Bayesian probabilities. It doesn’t matter how incredibly unlikely it is overall that *some *particular universe has *our *particular parameters. The probability that a universe containing us has compatible parameters *for us *is 1.0. What you can observe depends critically on where you stand. And we only stand in this one particular universe.
That disconnect between our universe being incredibly insanely unlikely and at the same time being absolutely certain trips up a lot of thinkers not used to applying Bayesian logic to problems.
They tend to assume instead that there must be some trans-cosmic thumb on the scale to make our universe not only much more likely, but in some arguments, inevitable. Again IMO bunk.
So what you’re saying is that no matter how unlikely our universe is, given enough universes the odds of at least one universe like ours is highly probable? Is there an experiment we can conduct to test this idea?
Our universe is utterly insanely zillions of zeros behind the decimal point unlikely. Period.
But given that we exist now, we will see what we do see: a universe with these particular parameters and us swimming around in it taking notes.
Said another way:
Q: How likely is it to flip 10 heads in a row with a fair coin?
A: About 1 in 1000.
Q: How likely is it to flip 10 heads in a row with a fair coin given that you’ve already flipped 9 heads in a row?
A: About 1 in 2.
How can the exact same coin flip, the 10th one, have odds of both 1 in 1000 and 1 in 2?
When you can comfortably explain that to yourself, you’ll understand what I’m saying about universes.
I thought the universe was ultimately completely inexplicable anyway. We try to chase down the nothing that existed before, and it involves our own incomprehensibles.
First of all, the so-called “Goldilocks principle” (I have not seen it described as a hypothesis, nor does it really fit that description) is an essential observation about the statistical distribution of a parameter, to wit, that for any measure that is randomly distributed there will be a large population around some arbitrary moment of the mean value, with the extremes at higher variance always being considered outliers. (Students of statistics will recognize this as just being a generalization of the central limit theorem.) For the observer the native state is that they are in a “just so” condition, e.g. measurements in degrees Fahrenheit seem ‘natural’ if you’ve grown up in the United States, even though they are no more ‘natural’ (and actually less sensible) than temperature measured on the Celsius scale. These observations say more about the observer than the probability of that condition.
What is being stated in this thread is akin to the strong anthropic principle: that the fundamental parameters of the universe are so fine-tuned to our chemistry and biology that there must be some special significance behind it, i.e. the universe was made to provide for us. This makes sense only if you assume that humanity is some special and unique product, and that the Earth was specially made to offer the ideal conditions for us to live upon. In fact, outside of the mythology of various religions, there is no evidence of this whatsoever; we’ve spent the last four centuries discovering that not only is the Earth or Sun are not the center of the universe, they aren’t even very unique. Nor can we restrict our definition of life to just being specifically like us; although our carbonaceous-nitrogenous structures defined by deoxyribonucleic acids are the only form life we know, that just indicates the depth of our knowledge; like a tourist who goes on vacation to New York but only orders room service to eat, we can’t state any degree of knowledge of the potential of life any more than our tourist can talk informedly about the cuisine of Manhattan in even a cursory fashion.
All we can infer about the possibilities of other universes is that we are well-fit to this one and would almost certainly not be able to survive in another with different chemistry and basic physical laws. We can make the argument that a universe with physical parameters that does not permit any analogue to chemistry is unlikely to give rise to the complex, self-reproducing patterns that we could ever consider alive, but as far as we know, uncountable numbers of randomly rolled up universes pop into existence every picoseconds; those with no chemistry analogue are spaces of unmetered chaos or absolute uniformity. If even a tiny fraction have the correct parameters to allow complexity to emerge, some kind of self-organizing, self-reproducing systems are probably inevitable, and some fraction of those might be something we recognize as life. Our universe could be that tiny fraction of a fraction of potential universes–not a “Goldilocks” but an extreme–and we would never be aware that we’re just the random flipping of a coin that happened to come up heads ten thousand times in a row. To assume that the universe is specially made because it supports us is like the young child who thinks his house and yard and food his parents serve him are all the best and everything else is “weird”. We don’t even know enough about the tiny local pocket of our universe, much less the potential for other universes, to have an informed opinion.
As for water, as Shagnasty stated and cited, there are a large number of properties that make it an almost ideal solvent and medium for our form of life. Given that we live on a planet that is largely covered in this substance, it doesn’t seem at all unusual that complex systems would evolve to use its special properties, and it is reasonable to look for evidence of water elsewhere as being a useful precursor to life. But we should not limit ourselves to the assumption that any other form of extraterrestrial life will be dependent upon liquid water.
Maybe the fallacy lays in assuming that every possible Universe has a God(s) in the first place. Does God (or any god) reside within the universe over which he rules? Is the existence of any Universe a prerequisite for its god to exist at all? Maybe even God can’t exist in the vast statistical majority of Universes. Maybe only those rare Universes that the just-perfectly-tuned to begin with can have a God.
Maybe we live in a Theotropic Universe that just happened to have all the right fundamentals for a God(s) to exist, who then took it from there to create all the rest!
I think there are two empirical difficulties with this otherwise fully conventional wisdom:
(1) We have indeed found increasing that the physical characteristics of the Earth and Solar System are far from unique. G stars are common, so are planets, and even within our Solar System there are quite a number of bodies with complex chemical cycles involving lots of interesting energy flows.
However, this means our failure to discover any hint of extraterrestrial life whatsoever makes the problem of where life comes from more peculiar and less obvious. It would be one thing if we found that, say, Mars had primitive microbes (even fossilized from its early history), and Titan some kind of low-level plant-like stuff that ate hydrocarbons – which is what the earliest sober thinking on extraterrestial life assumed – but that Earth was uniquely rich and the only one that sported intelligent life. That wouldn’t be so weird. Some planet has to have the most complex life, why shouldn’t it be this one?
But it is quite strange that by contrast there is no life at all anywhere in the Solar System we look, not even traces, not even plausible precursors or remains, despite the presence of plenty of water, available energy, many different and complex chemical environments with plenty of active cycling of compounds, and so on. This does tend to point towards the very counterintuitive hypothesis that there is indeed something very special about Earth or its history – something well beyond that it has liquid water, large energy flows that can be parasitized, et cetera. In short, the longer we go without seeing anything along the road to life at all, the more likely it becomes that there is indeed something very subtly special about Earth.
(2) The physical properties of water are not special, and if that were what mattered to life, we could readily imagine it based on some other kind of substance. However, life is a chemical process, and water has unique chemical properties. Or rather, not water per se, but the phenomenon of hydrogen bonding. A hydrogen bond is unique in that it is a form of association that at the right temperatures is significantly stronger than available thermal energy – so it provides a fair degree of permanence to structures held together with it – but at the same time is significantly weaker than covalent bonding – so that it can be rearranged and modified by molecular mechanisms at temperatures and energies that do not risk the structural integrity of the mechanisms themselves. It is no accident that the most important interactions in molecular biology are hydrogen-bonding in origin: the forces that hold the halve of the DNA helix together, which cause proteins to fold into useful shapes and keep them there, which cause oligomeric and polymeric cell structures like spindles and fibers to stick together, which cause membranes and cell contents to segregate and form distinct regions, or which drive substrates to associate with enzymes.
It’s hard to imagine life not using H-bonding forces. If it were to operate at very low temperatures, so that its temporary structures and associatinos were held together with van der Walls forces, the thermal energy available would be entirely insufficient to build any molecules – to build any “tools” with which to guide those associations and structures. If it were to operate at high temperatures, so that its temporary structures and associations were held together by covalent bonding forces, the mechanisms that are supposed to guide those associations (the “tools”) would be too short lived themselves to last. H-bonding provides a golden medium. The reason liquid water them becomes relevant is because it is the most common substance in the universe which exhibits strong H-bonding and which is liquid at the temperatures where H-bonding is modifiable by available thermal energy, but only with difficulty, which lends structures built with it the key semipermanence life requires. Which is not to say you couldn’t build life with other H-bonding solvents – ammonia, say. But there’s way less ammonia than there is water in the universe.
So it’s actually hard to imagine life not using liquid water. Not because of the physical properties of water per se, but because it’s the most common substance that exhibits the particular intermediate-scale molecular forces on which life depends for fundamental reasons – forces that allow life to exhibit its characteristic mix of permanence (it sticks around for a while, defying entropy) and dynamicism (it grows, changes, responds, moves).
Carl Pham, thank you for your post on the essential nature of water in biochemisttry. I wanted to make the same point, but lacked your knowledge and eloquence.
Among water’s other important chemical properties: it is very stable, yet also can readily donate (at least in the presence of catalysts) protons and (oxidizing) hydroxyl ions. Both proton donation, and use of OH ions are essential to many biochemical reactions. These reactions only take place in water.
What other common chemicals could be so utilized? Ammonia is much more reactive than water and, anyway, would it be practical to develop a biochemistry where the role of OH is taken by NH[sub]2[/sub][sup]-[/sup] ? And even if some other chemicals might work as the bathing solvent for organic chemical life, there’d be very few possibilities – not the myriad needed to argue against Goldilocks specialness.
That a system based on molecules was the only plausible basis for life was worked out famously by Erwin Schrödinger long before biochemical details were known. Read Life on the Edge, a good layman’s overview to see how chemical details uphold Schrödinger’s predictions.
Stranger, sorry for my thoughtless use of “hypothesis” – I’m not good at words and tend to blurt out wrong ones. Still, I stand by the rest of the post.
