In the June 30th issue of New Scientist Paul Davies discussed the anthropic principle [The flexi-laws of physics]. He says,If the universe came with any old rag-bag of laws, life would almost certainly be ruled out. Indeed, changing the existing laws by even a scintilla could have lethal consequences. For example, if protons were 0.1 per cent heavier than neutrons, rather than the other way about, all the protons coughed out of the big bang would soon have decayed into neutrons. Without protons and their crucial electric charge, atoms could not exist and chemistry would be impossible.As far as we know, life exists on one small planet orbiting an insignificant star in an unremarkable galaxy off in one small corner of the known universe. This reminds me of a famous Mark Twain quotation [Mark Twain and the Eiffel Tower].
Physicists and cosmologists know many such examples of uncanny bio-friendly "coincidences" and fortuitous fine-tuned properties in the laws of physics. Like Baby Bear's porridge in the story of Goldilocks, our universe seems "just right" for life. It looks, to use astronomer Fred Hoyle's dramatic description, as if "a super-intellect has been monkeying with physics". So what is going on?
I really like the letter from Nathaniel Hellerstein that appeared in the July 21st issue of New Scientist.
If Paul Davies says that the universe is bio-friendly, then I say he hasn't taken a good look at it (30 June, p 30). The universe is bio-tolerant, maybe, or better yet bio-indifferent. Looking at the night sky, I do not see a cosmos optimised for producing life. It appears to be optimised for producing vacuum.
Even if the universe somehow "needs" life, it evidently doesn't need very much of it. Perhaps, from the cosmic point of view, life is a necessary evil, to be tolerated and limited.
I call this the misanthropic principle - it certainly fits the facts better than the anthropic principle does.
As far as we know, life exists on one small planet orbiting an insignificant star in an unremarkable galaxy off in one small corner of the known universe.
ReplyDeleteThat's not saying much, since we don't know much. AFAIK we haven't even ruled out life on mars or europa yet. And even if other life (including intelligent life) were found, I'm not sure it would weaken the anthropic principle, any more that it's weakened by the presence of other life all around us (as individuals) on this planet.
The anthropic principle however, does not explain why, out of presumably multiple universes able to harbor life, that we are in this particular one - which is analogous to the question of why we are the individual we are, and not another. These are some of the most profound questions that can be asked. Except of course, if you're a solipsist. Then both questions and the fine-tuning of universe make perfect sense.
I’m not sure whether this gut reaction to a visual inspection of the cosmos counts for much. A million coin tosses might seem a lot but if we found a run of 30 heads we might begin to suspect loading. Likewise, the visible cosmos seems big but given that living organisms are taken from a space of possibilities whose logarithmic size runs into millions upon millions of digits, the visible cosmos (whose logarithmic size in space and time extends at most to a mere three or four digits) simply does not provide enough space and time if the chances are evenly spread over the space of possibilities. So the big question is: what is loading the probabilities allowing the computations of natural selection to work? It may be that the universe is far, far bigger than we can ever hope to see or detect (multiverses and all that), thus allowing an unloaded probability regime to eventually produce life. But failing that it looks as though something is loading the probabilities in favour of natural selection: Either our given regime of physical laws, or something we have yet to understand about complexity, or maybe both. I think you will find that this is the sort of thing Paul Davies is getting at.
ReplyDeleteI really like the letter from Nathaniel Hellerstein that appeared in the July 21st issue of New Scientist.
ReplyDeleteThen you really like being just as utterly clueless about how the goldilocks enigma works.
I do not see a cosmos optimised for producing life
That's NOT what the anthropic physics predicts, but we're all glad that you feel like you are free to express your uneducated opinion.
Get a clue
The interest in anthropic principles investigates what earlier for different reasons seemed like a suspect albeit natural solution for physical models. It has some "interesting" connections to evolutionary theory, which no doubt would explain similar sentiments.
ReplyDeleteIt appears to be optimised for producing vacuum.
I think Hellerstein makes a mistake - universes with radically different cosmological constant would have radically different lifetimes and other properties. I doubt that we can expect much more mass:
The largest problem when discussing this is that people tend to discuss different anthropic principles out of the set of possibilities. (Tautological AP, weak AP, environmental (EP), strong AP, forced AP, final AP, "completely ridiculous AP (CRAP)", ...)
Another problem is when various finetunings are unnecessarily tied to probability of life. Davies seems to do this. But often the bounds are more relaxed than some analysis says.
This is one connection to evolution by way of TE and ID cosmological teleology. Creationists of different kinds likes to twist these numbers because they erroneously thinks finetunings are unnatural when a simple analysis shows the reverse is true. Finetunings seems loosely to be as consequential as interlocking complexity is in evolution, which is an interesting parallel to creationists twisting the later into "IC".
There are two recent physical motivations for AP; the recognition that stateful theories admits various vacuum solutions while lacking cosmological selection principles, and multiverse cosmology which does the same. Earlier it was hoped that more complete theories would force one unique solution. [Possibly a mistake akin to picking a forced AP ("the universe must create life").]
The problem with AP on the cosmological scale is that the APs that naturally picks solutions, the weak APs, must resolve a probability. Some have noted that "cosmological evolution" would do this elegantly, since selection principles work locally. (Lee Smolin has proposed such a cosmology, btw.) It is IMO interesting that what comes about naturally in biology would be a grand thing in physics as well.
So what do we do if we mistrust anthropological principles, for example because one single model which gives a cosmological constant isn't testable - we live in the universe we have?
One solution is to look for environmental principles, not dependent on live observers but classical observers of any kind. This removes ambiguities how to define "life". Another is to hope that the same principle picks several parameters, which would constitute a testable prediction.
Boussou et al has proposed one EP based on maximizing entropy. Since dust is what does this best, we should find universes with lots of suns producing it. And planets and life - as Sagan noted, we are star dust ("star stuff"). Boussou has a paper that may answer Hellerstein, with explicit models - we seems to live in a universe that has produced as much dust as is possible.
Isn't the anthropic principle similar to panglossian adaptationism? Everything is described as being "just right", precisely again, to invoke some intelligence.
ReplyDeleteI think the anthropic principle is along a teleological line of thinking of inverted causality. Life was made possible thanks to certain conditions; the conditions did not come together to make life possible.
Objections:
ReplyDelete(a) We don't know that life could not exist under other laws of physics. If, for example, protons were heavier than neutrons it would change the universe so radically that we really have no idea of what would and would not happen. It is possible that there would still be life, just not our kind of life.
(b) If you apply the same sort of logic to anything other than the laws of physics, where humanity's pro-religious prejudices make us more likely to accept the ideas, then you instantly see how stupid this is: "all of economics and finance exist only to make sure that the exchange rate between the dollar and the yen is 118.385 yen per dollar" "computers only exist so that there would be something to put under 005 in the Dewey Decimal system" "the sky changes colors at sunset to help artists use all the colors in their palettes"
(c) Why stop with intelligent life? Maybe the laws of physics are predisposed to beings that have a sense of smell, too. There is roughly as much conclusive direct evidence of this as of the anthropic principal as it is generally stated. Show me some intelligent life without an olfactory sense, and I'll recant.
not dependent on live observers but classical observers of any kind.
ReplyDeleteA mistake. I meant not explicitly dependent - we must still have an implicit connection to us.
This comment has been removed by the author.
ReplyDeleteSanders:
ReplyDeletepanglossian adaptionism ... inverted causality
Not necessarily. If you do the analysis I mentioned (Sober, Jeffery & Ikeda) dependent probabilities follows from causality. The other way is the creationist mistake btw. You will also see finetunings as a natural result.
anonymous:
It is possible that there would still be life, just not our kind of life. ... Why stop with intelligent life?
The principle you choose should explain what we see in a weak AP scenario, which is the most realistic IMO. The later is the type of concern what environmental principles address - the probability for observant life is a bit ambiguous as you note.
If you apply the same sort of logic to anything other than the laws of physics,
We are not assured that we can do this. For example if this is contingent on the possibility for life (or maximum entropy or whatever related measure you chose), not the characteristics for it, as for the weak AP. Which btw I think was your points (a) and (c).
As I noted in an earlier comment, much of this comes down to which logic (AP) you choose to use.
Dawkins at Douglas Adam's Funeral:
ReplyDeleteThis is rather as if you imagine a puddle waking up one morning and thinking, 'This is an interesting world I find myself in - an interesting hole I find myself in - fits me rather neatly, doesn't it? In fact it fits me staggeringly well, must have been made to have me in it!'
The largest problem when discussing this is that people tend to discuss different anthropic principles out of the set of possibilities.
ReplyDeleteBut none of them supecede the apparent strong implications of the observed universe.
To listen to Susskind or Weinberg, the most apparent explanation without a multiverse is a designer.
What they're really saying is that the universe "appears" to be strongly anthropically constrained, and without a multiverse, it is.
Funny how nobody recognizes this, innit?
Dawkins at Douglas Adam's Funeral
ReplyDeleteAnother invalid misrepresentation of the physics that neodarwinain antifanatics typically tend to fall in love with because it sounds cool when they all grunt together.
Dawkins at Douglas Adam's Funeral
ReplyDeleteThat would actually be a good analogy - if puddles were also observers. (and NO, lets not turn this into a QM discussion).
island says,
ReplyDeleteThen you really like being just as utterly clueless about how the goldilocks enigma works.
Hmmm .... touched a nerve, did I.
The rally clueless ones are those who can't appreciate the humor of the misanthropic principle.
Sanders asks,
ReplyDeleteIsn't the anthropic principle similar to panglossian adaptationism? Everything is described as being "just right", precisely again, to invoke some intelligence.
No. There are many variants of the anthropic principles but most of them recognize, quite rightly, that if the laws of physics and chemistry weren't just right then we woulodn't beher to observe them.
In those variants, the concept of the anthropic principle is about as exciting as the lottery winner who thinks his birth date has some special cosmic significance.
People who believe in God, like Michael Denton and Francis Collins twist the concept into the "fine tuning" argument for the existence of God.
To listen to Susskind or Weinberg, the most apparent explanation without a multiverse is a designer.
ReplyDeleteIs anthropic reasoning possible without the concept of a multiverse? And... do we have any evidence at all for a multiverse? If not, then why is the anthropic principle even an argument? If there's no evidence for a multiverse, you'd either have to argue for pure coincidence (immensely improbable), or use anthropic reasoning in reverse, to assert that there must be a multiverse (as yet undetected), since we are here. Both seem highly suspect.
So, as we seek explanatory “theoretical wrappers” to embed biological realities, what options are we left with? Two choices, it seems: Either we have an infinite system with even/unweighted probabilities (the ‘multiverse’) or we opt for a ‘small’ system with biased/weighted probabilities.
ReplyDeleteBut either way we are left with an unsatisfactory hiatus, an irreducible hard core of givens that leaves me, at least, with the feeling “Is that it?” and a realization that human knowledge can never deliver aseity, and is apt to give trivial answers to the meaning of life like Douglas Adam’s ‘42’.
It is surely an irony that of the two general theoretical models the ‘multiverse’ is most akin to deity. In postulating a kind of “super-copernicanism” in order to accord mediocrity to our situation it posits as ‘given’ that most enigmatic of concepts: the infinite random context. Here, the irreducible hard core – if such it can be called – is everything there possible could be! (all but!). In short the multiverse postulates something infinitely complex, omnipresent, inscrutable, baffling, incomprehensible and incompressible, the essence of mystery - the capricious ‘god’ in which we “live and move and have our being”! Occam eat your heart out!
Sorry for the delay.
ReplyDeleteHere is another exposition on the current anthropic work.
By using the same principle and match several parameters "...this result improves our confidence in the entropic principle and the underlying landscape....". for example, the work constrains the cosmic constant within 2 orders of magnitude when anything is a priori possible, a distribution roughly centered on the correct value. (See the figures in the overhead presentation.)
You can't really calculate a likelihood for this, but if 1 is the natural expectation and since negative values are allowed, you get less than 1 % likelihood for random coincidence on this one parameter alone.
island:
But none of them supecede the apparent strong implications of the observed universe.
The tautological AP would give no implications except matching parameters. (Equal likelihood.) This is how Hoyle predicted the carbon-12 resonance in the triple-alpha process.
without a multiverse, it is.
Without a source of environmental variation the weak AP would not work at all, as already noted.
(Btw, the string landscape vacua is another source, different from the multiverse question.)
Anonymous:
That would actually be a good analogy - if puddles were also observers.
The main lesson of the puddle analogy is correcting the a priori probability with the a posteriori likelihood confusion, which Sober et al treats.
Timothy Reeves:
Occam eat your heart out!
But these theories are no less parsimonious than others, probably more so. (No unique constraints.) As I noted earlier, all sorts of physical theories have naturally a spectra of vacua. Parsimony is a character of the models (say, gases contracts to stars), not the observations (many stars).
Btw, I think a biological analogy would be cladistics. Maximum likelihood methods are among those used to establish the tree diagram of phylogeny. There is a unique common descent phenomena that we can access but it still permits test of the method, the evolutionary theory and the specific observed model.
ReplyDeleteHere we have a unique universe that we can access but using the same principle (say, the entropic) throughout it seems it permits test of the method, the inflationary theory and the specific observed model.
The difference would be that some parameters may be decided by unknown constraints. But perhaps the physicists concerned could call this "the current best model" if they wish.
Thanks for the thoughts and links torbjorn. We are obviously benefitting from your Internet unbiquity!
ReplyDeleteI have tertiary syphilis.
ReplyDelete