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spratleyj
2008-Oct-09, 01:13 AM
From what I've read about it the Anthropic Principle seems to something that a "religious" scientist might use to explain phenomena, however what I'm baffled at is why physicists like Susskind seem to embrace it - so any clarifying as to what the Anthropic Principle acutually is or about why so many scientist seem to embrace it...

BigDon
2008-Oct-09, 01:17 AM
Oh Spratley! There was a big thread on this. I think started by Raven's Cry.

AGN Fuel
2008-Oct-09, 01:55 AM
I have a great deal of sympathy for the (weak) Anthropic Principle and there is not a religious bone in my body!

Ken G
2008-Oct-09, 03:14 AM
From what I've read about it the Anthropic Principle seems to something that a "religious" scientist might use to explain phenomena, however what I'm baffled at is why physicists like Susskind seem to embrace it - so any clarifying as to what the Anthropic Principle acutually is or about why so many scientist seem to embrace it...
Do you mean the strong anthropic principle? The weak one is pretty inescapable and has little explanatory power. It just says that if intelligent life appears anywhere, that's where the question "how likely is intelligent life, given its requirements" will be asked. It's a bit like only interviewing lottery winners when examining the chances of winning the lottery. The strong principle says that life has to appear, so the basic parameters of the universe as a whole have to be set up so as to make life possible, and that explains why they have the values they do. So the weak principle addresses where and when life appeared in our universe, given its parameters, and the strong principle addresses why it appeared, i.e., why those are the parameters of our universe.

Neither requires any religion, they are expressly a way to discuss the existence of life without referencing any kind of deity or plan-- it is a way to get life to appear spontaneously where and how it does, because it has to to be consistent with what we already know is true-- we are here.

To me, the question to ask is "but is this explanatory of anything, i.e., what are the requirements of an explanation", with special stress on the issue of whether one can use what is given to be true as part of the explanation for why it's true.

agingjb
2008-Oct-09, 07:21 AM
I wouldn't underrate the Weak Anthropic Principle. If nothing else it does emphasize that we could just be lucky to be here, as against Gaia hypotheses which suggest that our environment is self-correcting.

AGN Fuel
2008-Oct-09, 10:01 AM
I agree, aginjb. I think the Weak Anthropic Principle is all too often dismissed glibly and taken for granted, but it is subtly powerful. I particularly find it useful in arguments with ID'ers on occasions!

island
2008-Oct-09, 03:02 PM
I agree, aginjb. I think the Weak Anthropic Principle is all too often dismissed glibly and taken for granted, but it is subtly powerful. I particularly find it useful in arguments with ID'ers on occasions!

The WAP is only valid if you assume that there is a multiverse and if I were an IDer, I'd laugh directly in your face for thinking that an unprovable multiverse is more plausible than exactly what it looks like.

Leonard Susskind very clearly expressed rationale for this in his interview with New Scientist concerning his recent book, The Cosmic Landscape: String theory and the illusion of intelligent design.

Amanda Gefter:
If we do not accept the landscape idea are we stuck with intelligent design?

Leonard Susskind:
I doubt that physicists will see it that way. If, for some unforeseen reason, the landscape turns out to be inconsistent - maybe for mathematical reasons, or because it disagrees with observation - I am pretty sure that physicists will go on searching for natural explanations of the world. But I have to say that if that happens, as things stand now we will be in a very awkward position. Without any explanation of nature's fine-tunings we will be hard pressed to answer the ID critics.

http://dorigo.wordpress.com/2008/06/23/guest-post-rick-ryals-the-anthropic-principle/
The Anthropic Principle was originally formalized by Carter as an ideological statement against the dogmatic non-scientific prejudices that scientists commonly harbor, that cause them to consciously deny anthropic relevance in the physics, so they instead tend to be willfully ignorant of just enough pertinent facts to maintain an irrational cosmological bias that leads to absurd, “Copernican-like” projections of mediocrity that contradict what is actually observed.

Carter was talking about an equally extreme form of counter-reaction-ism to old historical beliefs about geocentricism that cause scientists to automatically dismiss evidence for anthropic “privilege” right out of the realm of the observed reality. I intend to put very heavy emphasis on this point, because people go to unbelievable lengths to distort what Carter said on that fateful day in Poland, in order to willfully ignore this point as it applies to modern physics speculations and variant interpretations, which are neither, proven, nor definitively justified, theoretically.

Why do none of the popular definitions of the anthropic principle include what Carter actually said?
…a reaction against conscious and subconscious - anticentrist dogma.

This a the real problem for science.

island
2008-Oct-09, 03:06 PM
I wouldn't underrate the Weak Anthropic Principle. If nothing else it does emphasize that we could just be lucky to be here, as against Gaia hypotheses which suggest that our environment is self-correcting.

I guess that you've never heard of the Goldilocks Enigma.

Ken G
2008-Oct-09, 03:12 PM
I wouldn't underrate the Weak Anthropic Principle. If nothing else it does emphasize that we could just be lucky to be here, as against Gaia hypotheses which suggest that our environment is self-correcting.But here's the kind of problem it engenders as an actual explanatory agent. Can you really argue that the weak anthropic principle is at odds with the Gaia hypothesis? I believe I could easily argue it supports that hypothesis, on the simple grounds that intelligence is more likely to appear in an environment that is capable of self-correcting, as opposed to one that is not. So if you have a million planets with some form of life starting to develop, only the few that build self-correcting versions of that life will ever sustain life long enough to produce intelligence. See? It provides a potential explanation for almost anything, because it has no actual meat.

Warren Platts
2008-Oct-09, 04:00 PM
To me, the question to ask is "but is this explanatory of anything, i.e., what are the requirements of an explanation", with special stress on the issue of whether one can use what is given to be true as part of the explanation for why it's true.In biology, teleological explanations are a commonplace. In the physical sciences, however, they are decidedly heterodox, to put it mildly.

Cougar
2008-Oct-09, 04:08 PM
I'm baffled at is why physicists like Susskind seem to embrace it - so any clarifying as to what the Anthropic Principle acutually is or about why so many scientist seem to embrace it...

Susskind (http://en.wikipedia.org/wiki/Leonard_Susskind) is "widely regarded as one of the fathers of string theory for his early contributions to the String Theory model of particle physics." As you may or may not know, string theory has had a real roller coaster ride through the field of theoretical physics. In his recent book, The Cosmic Landscape, String theory and the illusion of intelligent design [2006], Susskind gives a detailed answer to your question, and that answer is, basically, "String Theory forced me into it." Originally, string theorists thought the theory would lead them to a single, unique solution that would then explain why things are the way they are -- why the vacuum energy is so close to zero (but non-zero), why the electrical charge is what it is, etc., etc. But as the theory continued to be developed, estimates started coming out that there appeared to be something like 10150 solutions, which meant that there were an embarrassing large number of possible different kinds of universes that were just as likely as ours. Well, in a sense that does offer some explanation about why our universe seems to be so well suited for life: If there are 10150 different 'universes,' odds are good that a few will have the characteristics that ours has. (Come to think of it, I'm not sure how this Landscape idea is particularly 'anthropic'....)

On the other hand, Steinhardt and Turok came out with a spirited opposition to anthropic reasoning with their 2007 book, Endless Universe, Beyond the Big Bang.

Warren Platts
2008-Oct-09, 04:30 PM
There are probably 10150 ways to arrange the atoms and molecules that make up a human body. So it's not surprising that at least 6 billion of such arrangements work more or less satisfactorily. Yet no one supposes that all 10150 arrangements have been tried out. Instead we invoke Darwinian processes to winnow the list of possibilities.

But when it comes to universes, we uncritically suppose that nature has tried out 10150 possibilities, and so we argue we shouldn't be surprised at how special our universe seems to be. But why should we expect that nature would actually try out all 10150 possibilities? Why would she want to. What kind of mechanism would that entail that would allow nature to flip through the entire rolodex of possible kinds of universes?

agingjb
2008-Oct-09, 04:48 PM
Hmm. No, the Weak Anthropic Principle isn't necessarily explanatory. What I said was: "we could be lucky". So what I tried and failed to say was that although, obviously the world in which I live is such that my existence is possible, that fact does not immediately guarantee the continuation of that state.

Actually it seems that the various Anthropic Principles imply sharper things about the physics of the universe than specifically about our planet.

My favourite Principle is:

The Recursive Anthropic Principle, which states that universe is such that the Recursive Anthropic Principle can be formulated.

I think it is true.

island
2008-Oct-09, 04:50 PM
There are probably 10150 ways to arrange the atoms and molecules that make up a human body. So it's not surprising that at least 6 billion of such arrangements work more or less satisfactorily. Yet no one supposes that all 10150 arrangements have been tried out. Instead we invoke Darwinian processes to winnow the list of possibilities.

But when it comes to universes, we uncritically suppose that nature has tried out 10150 possibilities, and so we argue we shouldn't be surprised at how special our universe seems to be. But why should we expect that nature would actually try out all 10150 possibilities? Why would she want to. What kind of mechanism would that entail that would allow nature to flip through the entire rolodex of possible kinds of universes?

A more relevant question might be... 'Why isn't the universe configured as is most naturally expected?'

http://arxiv.org/abs/hep-th/0512148

Did "god" really have a choice?

I doubt it.

The willfully ignored answer is that there is an anthropically oriented cosmological principle at play that cause the universe to take the entirely unexpected form that we observe.

Something... like this:
http://www.lns.cornell.edu/spr/2006-02/msg0073320.html

tdvance
2008-Oct-09, 05:16 PM
There's also a kind of "reverse anthropic principle":

why does the Earth's atmospher have oxygen? If it didn't, we'd not be here, right? Or is it if it had, say, methane, we'd be methane breathers.

It's like the parable of the puddle of water in the road. the water thinks the hollow in the ground is shaped just right for him, when in fact, it is he who is shaped for the hollow in the ground.

Spaceman Spiff
2008-Oct-09, 05:33 PM
There's also a kind of "reverse anthropic principle":

why does the Earth's atmospher have oxygen? If it didn't, we'd not be here, right? Or is it if it had, say, methane, we'd be methane breathers.

It's like the parable of the puddle of water in the road. the water thinks the hollow in the ground is shaped just right for him, when in fact, it is he who is shaped for the hollow in the ground.

Yep. Somebody once suggested that it wasn't that the universe was designed for us, but rather that we are a result of the universe we inhabit.

Neverfly
2008-Oct-09, 05:52 PM
Yep. Somebody once suggested that it wasn't that the universe was designed for us, but rather that we are a result of our universe.

If it WAS designed for us, I'd like to get my hands on that designer!

Spaceman Spiff
2008-Oct-09, 06:25 PM
If it WAS designed for us, I'd like to get my hands on that designer!

:lol::lol::lol::lol:

Ken G
2008-Oct-09, 06:38 PM
The Recursive Anthropic Principle, which states that universe is such that the Recursive Anthropic Principle can be formulated.

I think it is true.I certainly think that's true, it's virtually tautological. That's my problem with it-- it's too true. I think Wittgenstein was making a similar point when he once wondered aloud why people took the fact that the heavens appeared to rotate about the Earth as evidence that it actually did-- he asked, in effect, don't you have to be able to imagine an alternative possibility to a certain observation before you can count that observation as evidence of anything?

Ken G
2008-Oct-09, 06:41 PM
It's like the parable of the puddle of water in the road. the water thinks the hollow in the ground is shaped just right for him, when in fact, it is he who is shaped for the hollow in the ground.
Exactly, although I wouldn't call that the "reverse anthropic principle", which sounds like an other variant on the anthropic principle, but rather the "anti-anthropic principle", which sounds more like anathema to the explanatory power of the first.

spratleyj
2008-Oct-09, 09:30 PM
A few people have said that the weak anthropic principle lacks predictive power - what kind of predictive power does the strong anthropic principle have?

I'm not sure I fully understand the anthropic principle as most of what I know is from what I read in Susskind's book... but I don't see why it is necessary or even that useful...

Ken G
2008-Oct-10, 12:07 AM
A few people have said that the weak anthropic principle lacks predictive power - what kind of predictive power does the strong anthropic principle have?Nothing very convincing, if you ask me. You first have to accept the concept of the "landscape" of multiverses, so that the universe can "try out" all the possibilities (a somewhat dubious assumption as Warren Platts critiqued). Then you have to have some way to understand the distribution over the possibilities, and that is what could be predictive-- if you have some reason to favor some types of multiverses over others that can allow life, you can predict that ours will be more like what you are predicting. But you have the same problem as with the weak principle-- how to claim that a given in the theory is an explanatory agent concerning the theory.


I'm not sure I fully understand the anthropic principle as most of what I know is from what I read in Susskind's book... but I don't see why it is necessary or even that useful...You are not alone. Said broadly, the point of the strong principle is to "explain" why we can live in a universe which seems to have highly unlikely attributes, just as the weak principle "explains" why the Earth can have highly unlikely attributes. But you first have to be bothered by the apparent unlikeliness-- which assumes you feel you have a good handle on what would be more likely. That's quite a reach.

timb
2008-Oct-10, 02:35 AM
There doesn't seem to be agreement on what the Anthropic principle(s) is(are), but people who use it(them) a lot are usually cranks. I have trouble understanding what it is they are saying. One statement of the SAP is the Universe must have those properties which allow life to develop within it at some stage in its history. Well, duh. We know from observation that the universe contains life, so it could not be the case that the properties of the universe preclude life. Similarly we know the universe contains the moon, so the Universe must have those properties which allow the moon to develop. I know that there is a rather smelly green carpet in my garage. From this I can derive the Strong Smelly Green Carpet Principle that the properties of the universe must be such that smelly green carpets can exist in garages. The SAP is a tautology.

The WAP says The observed values of all physical and cosmological quantities are not equally probable but they take on values restricted by the requirement that there exist sites where carbon-based life can evolve and by the requirements that the Universe be old enough for it to have already done so. While the SAP means something trivial, the WAP doesn't seem to mean anything at all. Observed values do not have probabilities. "If I toss a head, what's the probability I have tossed a head?" They are certainties. Obviously our measurements have errors which means we are always uncertain about the true value of any physical quantity, but that doesn't change the measurement. I think what they're trying to say is that possible true values of physical quantities are not all equally likely because they are constrained by the requirement that there exist sites where carbon-based life can evolve etc.

That's another triviality. We know that carbon-based life exists, so we know that, for example, G cannot have a value that would preclude carbon-based life. Similarly c, ℏ etc. Unfortunately we know extremely little about what values of G, c, or ℏ would preclude carbon-based life, and what bounds we could deduce would be many orders of magnitude greater than the standard errors in our experimental measurements of these quantities. So the WAP doesn't tell us anything.

speedfreek
2008-Oct-10, 01:58 PM
In my simplistic view, it all boils down to the following:

We are here. The laws of physics allow the conditions for life to form. Only if the laws of physics allow life to form will the question be asked as to why the laws of physics allow life to form.

If you have to consider it in terms of probability, the question will only be asked in a universe where the probability of life forming was 1:1. Probability is only a useful tool for making predictions before an event happens. After the event, the chances of that event happening were 1:1. What are the chances of throwing a die and coming up with 6? 1 in 6. If you throw a six, and then consider what the chances were that you would throw a six, the answer is 1 in 1.

So what are the chances of our universe being able to support life? It is a certainty, because it happened. But could the universe have turned out in a way where life couldn't form? Perhaps, but it would have required some of the initial conditions to have been different to what they were and if the initial conditions led to a universe where life couldn't form, nobody would be asking the question!

Is this a cop-out? Well yes it is, if you want to know why the conditions in our universe turned out in a way that allows life to form.

Perhaps there are/were a multitude of universes. Perhaps every set of conditions has played out somehow, somewhere. Perhaps when the 'branes of M-Theory bang together, different conditions arise in the universe that is created with each clash. Perhaps the universe rolled a six first time out.

Perhaps the anthropic principle is simply another way of asking for a first cause.

To me, we should simply consider ourselves lucky to exist and get on with it! But then again, by definition there are no life-forms that were unlucky in that they don't exist, so luck doesn't really come into it!

spratleyj
2008-Oct-10, 08:08 PM
In my simplistic view, it all boils down to the following:

SNIP

Is this a cop-out? Well yes it is, if you want to know why the conditions in our universe turned out in a way that allows life to form.


I don't think science ever will or should answer the "why" in that "why are the laws of physics what they are?" - I mean there are so many similar questions that could be asked, yet never scientifically answered - for example why are there scientific laws at all? I think this falls into the philosophical realm and that science shouldn't try to explain the unexplainable...

Ken G
2008-Oct-10, 08:16 PM
I don't think science ever will or should answer the "why" in that "why are the laws of physics what they are?" - I mean there are so many similar questions that could be asked, yet never scientifically answered - for example why are there scientific laws at all? I think this falls into the philosophical realm and that science shouldn't try to explain the unexplainable...That's my problem with anthropic thinking as well-- it doesn't strengthen any scientific cases, it just dilutes them all by confusing science with other forms of inquiry. In so doing, it also opens science up to criticisms generally reserved for those other forms, and I can't see why the cost/benefit on that scale comes out a positive. I think some would argue that anthropic thinking is not meant to be science, it's meant to be pure philosophy dabbled in by scientists, but that's a slippery slope...