The anthropic principle is an observation, not an explanation. To believe otherwise is to believe that our emergence at a late date in the universe is what forced the constants to be set as they are at the beginning. If you believe that, you are a creationist.As with many experimentalists, this Nobel Laureate deserves a lot of respect for his knowledge of both experiment and theory, so I need to walk on egg-shells, but his statement above is wrong, as are most of the rest of the statements that he makes about the anthropic principle, and it is for the same reason that I commonly run into, which is this:
Scientists don't seriously believe that any form of real anthropic preference is even possible, so they simply don't bother to learn enough about it to think about it in that context. For this reason they apparently don't understand that statements that ignore any part of the following are not going to be anywhere near accurate:
If you bear in mind all of the relevant information of the above statement, then it becomes very obvious what assertions like the following neglect to consider:
The cosmological anthropic principle says that since we exist, the universe must have evolved in a way that allows us to exist.
It is true, for example, that the fine structure constant α has to be close to 1/137 for carbon atoms to exist, and carbon atoms are required for us to be here writing about cosmology. However, these arguments have nothing to do with explaining what physical laws led to this particular value of α. An interesting relevant recent paper by Roni Harnik, Graham Kribs, and Gilad Perez demonstrates a universe with our values of the electromagnetic and strong coupling constants, but with a zero weak coupling constant. Their alternative universe has Big-Bang nucleosynthesis, carbon chemistry, stars that shine for billions of years, and the potential for sentient observers that ours has. Our universe is not the only one that can support life, and some constants are not anthropically essential.
We talk about the Big Bang, string theory, the number of dimensions of spacetime, dark energy, and more. All the anthropic principle says about those ideas is that as you make your theories you had better make sure that α can come out to be 1/137; that constraint has to be obeyed to allow theory to agree with experiment. I have a very hard time accepting the fact that some of our distinguished theorists do not understand the difference between observation and explanation, but it seems to be so.
Richter then referenced this paper to support his statements:
A Universe Without Weak Interactions
http://arxiv.org/abs/hep-ph/0604027
With full benefit of the doubt in place, I can only conclude that Burton Richter doesn't know how important it is to refrain from dissecting the complete statement:
Problems in a weakless universe
http://arxiv.org/abs/hep-ph/0609050
The fact that life has evolved in our universe constrains the laws of physics. The anthropic principle proposes that these constraints are sometimes very tight and can be used to explain in a sense the corresponding laws. Recently a "disproof" of the anthropic principle has been proposed in the form of a universe without weak interactions, but with other parameters suitably tuned to nevertheless allow life to develop. If a universe with such different physics from ours can generate life, the anthropic principle is undermined. We point out, however, that on closer examination the proposed "weakless" universe strongly inhibits the development of life in several different ways. One of the most critical barriers is that a weakless universe is unlikely to produce enough oxygen to support life. Since oxygen is an essential element in both water, the universal solvent needed for life, and in each of the four bases forming the DNA code for known living beings, we strongly question the hypothesis that a universe without weak interactions could generate life.
I honestly don't want to be too hard on Burton Richter, but this problem is too common among scientists who sorely misrepresent the relevant physics simply because they have dismissed the possibility for any real anthropic preference out of hand, without any real consideration for possibilites. All the imagination in the world for any other possibility, but a complete lack thereof when it comes to this.
How can you possibly expect to ever explain what physical laws led to this particular value of α... if you're not willing to recognize that ALL of the anthropic coincidences point commonly or "coincidentally" toward carbon-based life, all the way down to the local ecobalance that enables our existence, so there is a clear indication that there is some good physical reason for it that is somehow "specially" related to the existence of carbon-based life?
The anthropic principle is an observation, not an explanation. To believe otherwise is to believe that our emergence at a late date in the universe is what forced the constants to be set as they are at the beginning. If you believe that, you are a creationist.
No, I'm sorry, that's false, and your non-scientific "belief" will necessarily obscure your view of reality, so it's pretty much guaranteed that you will never find the answer that you seek as long as you are unwilling to entertain the implication for true anthropic preference.
It's a number provided to us by nature... and a physicist believes that a theory will someday provide a reason for it...
-Paul Dirac
15 comments:
We make statements like that because of the fact that the CMB shows the basic hallmarks of inflation.
The universe is just along the borderline between being open and closed, so we either have a type I universe, in which all initial volumes are realised, or a type two one, which creates different universes with different fundamental constants, as predicted by chaotic inflation.
Thus, the problem of 'fine tuning' is addressed by modern inflationary theories.
Thank you very much for the reply, "anonymous", but doesn't that require that we adopt an ad-hoc assumption about the initial entropy state in order to account for the time asymmetry?... which typically involves the use of the weak anthropic principle, so this still does not discount the implication that we are somehow specially relevant and necessary to the physical process.
Regardless of that, nothing is definitively settled yet, so you can't simply discount this implication until it is, and my point was that doing so without said justification is wrong and isn't scientifically honest.
I personally would argue that inflationary theory is an un-necesary band-aid to big bang theory that only came about because we were already dead-set on the projected idea that the universe began from an ultra-low-entropy cosmic singularity, which doesn't explain why the entropy of the early universe was so small if high-entropy states are more "natural".
Projecting backwards in time to the point where inflationary theory became necessary to explain the flatness and horizon problems isn't the most natural explanation, since the most obvious indication is a universe with certain volume had a big bang right there and then.
Of course, I would also claim that I can define a viable mechanism for this, so I would claim that inflationary theory isn't necessary for more good reasons than science is ready to go back and recognize.
Thanks again for your considered reply.
I wouldn't dismiss the anthropic principle out of hand, I'm just skeptical of the fact that I haven't seen any firm data from anthropic-related physics such as the string landscape theory.
Inflationary theory shows excellent agreement with WMAP data, but I would reserve judgment on anything more speculative such as the anthropic princple until data from Planck in a few years time when we'll be able to see data that would falsify cosmological consequences of 'anthropic' physics such as the landscape.
I wouldn't dismiss the anthropic principle out of hand, I'm just skeptical of the fact that I haven't seen any firm data from anthropic-related physics such as the string landscape theory.
Inflationary theory shows excellent agreement with WMAP data, but I would reserve judgment on anything more speculative such as the anthropic princple until data from Planck in a few years time when we'll be able to see data that would falsify cosmological consequences of 'anthropic' physics such as the landscape.
Maybe I misunderstood you. Please explain to me how any of this supports to the kind of special anthropic connection that Burton Richter was talking about, that you originally commented on.
Please show me how I'm not justified to say that you don't know what you're talking about?
I was merely stating that I'm skeptical of the principle until definitively proven by any cosmological data. I don't exactly appreciate being attacked for merely stating that I would wait to see what the data shows before coming to any firm conclusions.
If Planck or CMBR data suggested that theories that invoke the anthropic principle were correct, I would have no choice but to believe them.
I don't really believe in my friend's practice of attacking people with beliefs he doesn't believe in, either.
Personally, I'm intrerested in the type II multiverse characteristic of chaotic inflation, producing bubbles of stable spacetime with varying constants, and in some of those the constants have taken on values to allow sentient life to arise.
Ours could be one of the few where this could actually happen. The landscape's type IV universe goes even further, suggesting universes with wildly different physical laws. The paper that you mentioned mentions one without a weak interaction, but yet it still allows life to arise. It has been criticised as not allowing not enough oxygen to be formed through stellar nucleosynthesis, but yet from several generations of stars oxygen would still be formed.
These models, where universes that support life can arise because of the variety of different possible values of physical constants, or possibly laws, address the problems of fine tuning. We've merely come to exist in a time where the universe supports life, possibly due to the type II multiverse, or in a rather more far-fetched scenario, the type IV.
I have no problem that some form of life must come to arise in this universe, but the fact that ours is specifically favoured because we as a species have caused the fundamental constants to be set seems a little far-fetched.
That said, I wouldn't dismiss Weinberg's observation about the cosmological constant either, which set out an idea similar to the one I mentioned above.
Ultimately I just believe in what the data from experiments tell me, so I try and reserve judgment about theories until I can see data to support or dismiss them. I may have ideas I personally favour, but I think it's unscientific just to dismiss any idea until I see it proven.
I need to write a post for all those who want to talk about stringy and mulitiuniversal interpretations of the AP, and post it on somebody elses blog where everyone will be on topic... ;)
I have no problem with these interpretations if they bear-out, but the point of this article was to gently illustrate that Burton Richter's statements were not honest.
I have no problem that some form of life must come to arise in this universe, but the fact that ours is specifically favoured because we as a species have caused the fundamental constants to be set seems a little far-fetched.
"Seems"... is relative to what you know about it, which is directly related to how much credence you give the evidence... ergo my statement:
Scientists don't seriously believe that any form of real anthropic preference is even possible, so they simply don't bother to learn enough about it to think about it in that context. For this reason they apparently don't understand that statements that ignore any part of the following are not going to be anywhere near accurate:
-The observed structure of the universe occurs in dramatic contrast to the modeled expectation... so many fixed balance points that are commonly or "coincidentally" pointing directly toward carbon-based life indicate that there is some good physical reason for it that is somehow "specially" related to the existence of carbon-based life.
"Seems" also has a lot to do with which cosmological model is actually in effect. If tension between the vacuum and ordinary matter grows as the vacuum expands then any little simulation of the Big Bang might result in a needle/balloon effect. In which case we would single handedly have cause the universe to leap.
Like I said... all the imagination in the world for any other idea, but a complete lack thereof where this is concerned.
whoops, double post:
FYI, I've edited down the tone of my last article, but the new blog format doesn't seem to allow for deletion, so I'm stuck with that.
I'm sorry about the above post... I think he's just enjoying himself doing his usual routine of baiting people he finds to be amusing. He does it to everyone.
I wouldn't mind discussing the consequences of stringy/anthropic landscape theories sometime.
Island, I recently re-read the first 7 chapters of Nick Bostron's book on Anthropic Bias.
A point I think I have come to understand, is something you seem to mention here. It's the phrase
"In dramatic contrast to modeled expectation".
The issue is really one of what should we find surprising, and what should that surprise tell us ? Clearly one thing it tells us is suspect our presmuptions - and maybe entertain the previously unthinkable ... with you there.
What I still can't grasp is the "unthinkable implication" of a true understanding of AP ... the teleology our original discussion started with ?
Regards
Ian
Hi ian,
The issue is really one of what should we find surprising, and what should that surprise tell us ? Clearly one thing it tells us is suspect our presmuptions - and maybe entertain the previously unthinkable ... with you there.
Well, the "normal" expectation follows the least action principle, but every model for turbulance driven structuring has failed miserably to reflect the configuration that we ended up with, (although there may be a very important development going on there, as we speak!).
I'm sure that the configuration does indeed follow the least action principle, but what is "unthinkable" to most is how the expectation can be constrained by us.
What I still can't grasp is the "unthinkable implication" of a true understanding of AP ... the teleology our original discussion started with?
Nobody likes the idea that we're not here by accident due to the implication that there is no free-will if this is true, and I would highly reccommend reading this blogger's relevant article:
http://judahmacabee.blogspot.com/2006/05/choices-do-we-have-bechira-in-latest.html>choices-do-we-have-bechira
Unthinkable implications:
Einstein was right, and "god" does not throw dice, so human evolution and every action that we take and every thought that we think is a guided process.
But the greater issue, I think, are commonly misunderstood assumptions that also make it pseudo-"unthinkable", like:
Geocentric arrogance:
People think that an admission implies that there is a hubristic implication that the universe is made just for us, so they fear that this will be used as evidence for a higher intelligence that's doing the guiding.
Wrong, without direct proof, the only implication can be that there is some method to nature's apparent randomness that makes us a necessary part of the physical process. i.e., you have to differentiate intelligent intent from any other form of natural bias or there is no reason to conclude intelligent origins over any other form of natural inclination.
They got it backwards because we are enabled, alright, but more like a specialized tool, where necessity is the mother of "invention", and we aren't the only tool in the chest, either, so we're only "priveleged to some extent"... like Brandon Carter said.
Hope that helps, and please let me know if I missed the point, but remember that Bostrom erroneously extends the mediocrity principle where it does not apply.
I guess that I blew that link, so here it is again:
choices, do we have bechira?
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