“The anthropic principle – the idea that our universe has the properties it does because we are here to say so and that if it were any different, we wouldn’t be around commenting on it – infuriates many physicists, including [Marc Davis from UC Berkeley]. It smacks of defeatism, as if we were acknowledging that we could not explain the universe from first principles. It also appears unscientific. For how do you verify the multiverse? Moreover, the anthropic principle is a tautology. “I think this explanation is ridiculous. Anthropic principle… bah,” said Davis. “I’m hoping they are wrong [about the multiverse] and that there is a better explanation.”” -Anil Ananthaswamy, in The Edge of Physics
It is pretty obvious that, since we already are here in this Universe, it had to have physical laws, particles and interactions that at least admit for the possibility that something like us could have formed.
Image credit: ESA / NASA / Hubble Space Telescope, of Messier 100.
But is that a tautology? Or can we learn something important about our Universe simply from that statement -- and the reasoning that flows from it -- alone?
Bubble Universe: According to the multiverse theory, our universe is only one among a large (or infinite) number of universes, each with a different combination of parameters. Most of them are not hospitable for life.
Sabine Hossenfelder takes us on a fascinating journey through the good uses (and some abuses) of the anthropic principle!
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I think the biggest issue with all this is the idea of fine-tuned constants. People say the speed of light is constant, but that's the locally-measured speed of light. It's constant only because of a tautology wherein we define our second and our metre using the motion of light. See http://arxiv.org/abs/0705.4507 and note that the "coordinate" speed of light isn't constant. Some people say Planck's constant isn't constant, see physcisworld. The fine structure constant α=e²/4πε0ħc is a "running constant", see NIST. It isn't constant, and conservation of charge suggests that it isn't e that varies. See http://arxiv.org/abs/1008.3907. IMHO all this stuff leaves the anthropic principle looking like pseudoscience. I don't know why anybody gives it the time of day myself.
Isn't it just a case of working backwards: we know something about the properties of out particular universe, and we can work backwards from those observed properties to constrain certain things about the universe. For an example in the case of Hoyle's deduction,(I don't know what is rationale was, but this one makes sense), our universe contains carbon at some rough level of abundance, therefore nuclear properties was obey certain constraints. Thats not too different from ordinary science where we do experiments to determine the values of things
in order to constrain our theories, the only difference is that the experimentalist usually has an idea of the theory beforehand, whereas the universe and the things we observe in it are a bit more ad-hoc.
I love the Anthropic Principle discussions!
That gets us down into the weeds of what we mean by whether something exists or not. President Clinton nailed it when he commented: "That all depends on what your definition of "is," is. Does something exist if we can define it and imagine its properties? or do we have to be able to hit it with a hammer? So, we are talking about a physical, three dimensional-plus-time, rock containing expanse of space: our physical universe. Then, we get into the Philosopher's sock consideration: If we have a sock and it gets a hole in it, and we repair the hole, is it the same sock? If it happens again and again, when does it become a different sock? When do admit that the universe might have become a different universe? Our physical universe is constantly changing, entropy is seeing to that. So our definition of what our universe IS, already encompasses some change. What the multiverse theory describes, however, is some sort of distinct splitting off of another separate three-diminsional-plus-time physical universe with the same physical constants, but very slightly different conditions, moment-by-moment, occupying the very same three dimensions-plus-time as we do. I am going to postulate an exclusion principle, much like the Pauli Exclusion Principle, that two co-terminous physical universes with the same, (or even nearly the same) physical constants can NOT occupy the same three-dimensional-with-time space in the same physical space at the same time. I'm going to name my postulated principle: The Harmony Exclusion Principle. Just because I like the name. While there may be an infinite number of other universes with other physical constants, no other three-dimensional-plus-time universe with nearly identical physical constants can occupy the space we are in, or get started in the space we are in, because we already occupy it.
Then, let's consider other universes with wildly varying physical constants, and we get into thinking about longevity. We are aware that myriad particle-antiparticle pairs of things are brought into being instantaneously all around us, and as quickly anihilate themselves and dissolve back into nothingness. We don't see these, because they occur too quickly and disappear. Our physical universe continues to exist because the physical constants have adjusted to the point where they maintain a continuity of self-supported existence. I suspect that universes with wildly different physical constants interact and anihilate themselves as quickly as a particle and anti-particle pair, and we don't see them because they happen too quickly.
I read last week where astronomers were using a massive galaxy billions of light years away as a lens to focus on a galaxy even farther away. That only works if the physical constants of our universe are stable over tens of billions of light years. And we are only LOOKING for objects (ok, there's that emphasis on Physical Objects again), and physical phenomena which our instruments can measure. If there were a separate universe with wildly varying constants between us and that distant galaxy, we wouldn't "see" it. Oh, wait. There's dark energy and dark matter. Maybe there's some"thing" to that.
But there must be some quality of dark energy and dark matter than maintains their continuity in three dimensional space. Hmmm? What is conserved?
Ethan,
Not to be obsequious, but I agree with everything you have expressed on the matter. This article reminds me of a thought I often consider:
It's that we probably cannot come close to imagining the extent of what there probably is to imagine. And given the vastness of the universe, we likely fail spectacularly to do so, at best.
This universe isn´t very friendly to life, think, how many zillions of galaxies, stars and planets, and life only on this tiny rock middle of nowhere. Probably. "Where are they"
Whoever "designed" this set of natural properties or values, did he really do good job?
Hmmm....seems to me the AP is an example of how human intuition can go wrong when it comes to statistics. We intuit improbability when in fact there is a 100% probability that something that arises within a universe will be consistent with that universe's laws.
whole argument is one
On Sabine Hossenfelder's point 7 "The applications of the anthropic principle in physics have actually nothing to do with life" -- this is of course right because of the "in physics", but OTOH the anthropic principle asymptotically extends to cosmology a form of reasoning that's natural to use in biology. Any living species implies the neighborhood of natural environment in which it can survive. What's called an ecological niche.
John, if the speed of light changes, then a shedload of other things change too, unless many things ALSO change in precise synchronicity.
If you wish to claim they change, then you need to explain what ensures that they were synchronised to parts-in-a-billion-or-better for at least the last 4 billion years, and almost definitely for the past 12 billion.
The arxiv paper does not do this.
I think the use of the term "anthropic principle" is unfortunate. That term makes it seem as though the principle is claiming that human life is in some way special and that the existence of human life has implications for the way we study the universe. Calling it the "porcine principle", the "simian principle" or even the "bacterial principle" would pretty much imply the same actual content without the philosophically loaded implications that seem to come with the "anthropic principle."
At its best, it seems to me that the anthropic principle serves just as a sanity check on our understanding of physics. If we apply our current best knowledge of physics (or any other branch of science) and come to the conclusion that human life cannot exist because of some implication of our theories, then we know that we have to go back to the drawing board and look more closely at our theories. Of course, the anthropic principle is nothing special in that regard; ANY observational data serve the same purpose. Existence of human and other life is just one more observation with which our theories must be consistent.
I think the usually excellent Sabine gets a bit confused at point 8 in her list of 10. She is claiming that the Anthropic Principle is no tautology, and I guess she is strictly correct in that. However, the examples she uses are logically flawed. The Anthrpoic principle claims, simply put: "If life - then - the universe must have parameters that enable life". This is NOT the same as "If the universe has parameters that enable life - then - life". In Sabines two examples of why the Anthropic principle is no tautology she gets these two confused - and they are very different.
It is a basic point of logic that "If A - then -B", is not equivalent to "If B - then A". "If I am a cat then I am a mammal" does not imply "If I am a mammal then I am a cat".
Sean, I'll differ with you about this: I agree that the use of terms such as "anthropic" (and naming theories of ecology after goddesses) creates cultural problems such as polarization of attitudes. However, in the end I would suggest as a principle, that we have to progress culturally to the point where we can handle those things without adverse effects.
It's up to us to ensure that the public's understanding of these ideas is accurate and leads to the right conclusions. We can't look at each day's news of humans engaging in ignorant brutish behavior, and then conclude that the best we can do is a holding action, such as keeping young-Earth creationism out of public schools. Instead we should insist not only on those things, but also boldly forge ahead and seek/demand a net increase in scientific literacy and capacity for observation and reasoning. This is exactly what Ethan has been doing with these columns, and lo & behold, he has a wide range of people reading them, who might otherwise never be exposed to these ideas.
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Waterbergs, I'm also inclined to believe that if a universe has values for parameters that enable life, life will inevitably emerge. Here I'm using the generalization that "in a natural universe, anything that is not forbidden is required, whether in large measure or small."
First question: is that generalization any good, or is it wrong or "not even wrong"?
Second question: Am I making a mistake with the following, and if so, what/where?: The version of the anthropic principle I use is "we are more likely to exist in a universe whose parameters are favorable to our existence, than in a universe whose parameters are unfavorable to our existence." In essence I'm thinking in probabilities, on a spectrum from "universe in which complex life is impossible" to "universe in which complex life is inevitable," and assuming that our universe is closer to the latter than to the former. Is that any good or is it crap?, and if the latter, what type of crap?;-)
Interesting article and discussion. Just to be honest, I am a sometimes nuanced, but indeed an evangelical christian; please remember the "nuanced", I may not be all that you would stereotype me to be.
I believe that the anthropic principle is one piece of evidence in favor of the existence of God.
It is NOT a probability of one, as eric says, I find this argument to be considerably lacking from a probability theory point of view.
And even if there are multiple combinations of constants that work for life, the AP still shows the EXTREME narrowness of conditions for life to exist.
This can be explained as design by an intelligent being, or by an extremely large number of universes with the variables randomized. We must decide which we think is more likely; I obviously believe the former. (Incidentally, a designer can also design multiple universes, or a multi-verse, as well as just one).
Well, since Gods have always been an invention of humanity, to an extent, I agree. Without us, there would be no gods.
That's rather like pointing to the extremely close fit between the water and the convoluted edge of the lake as being SUPREMELY UNLIKELY.
The AP merely takes the view that the chances of the figures being what they are observed are 100% SINCE THE HAVE BEEN OBSERVED.
No, it isn't explained by an intelligent being. You have to show that intelligence will allow you to select the physical constants. You have to show that intelligence, therefore, doesn't require an extant universe, and also being doesn't require a universe to be in.
You then have to explain why they did it as opposed to something else.
Then you have to explain why that intelligence has gone to such lengths as to never appear, except in a distant past where we have absolutely no proof other than hearsay and myth.
Then you have to explain which one of the over 6000 known (and how many unknown to us today?) intelligent beings you meant, how you know it's that specific one and not any of the others, whose stories about what they did are all contradictory between each other and, in many cases within itself.
Indeed your explanation leaves you with vastly more intractable problems than you started out with.
Science can do that too, but it doesn't just wave its hands in the air and go "magesterium!" and avoid it entirely. It then uses the new questions to test whether the earlier answers were right, and what new questions may be available.
Andrew:
Okay, I'm curious. If it's not 100%, what do you think the probability is that something arising within a universe will be consistent with it's laws?
If narrowness of conditions for life implies designed for life, then even more narrowness of conditions for human life implies designed for human life. Right. And if we find some species that requires even more narrow conditions than humans do, we can conclude the universe was designed for it instead of us. Right? That would be the consistent application of your logic. Let me know, then I'll give you an example of something that needs even more stringent conditions than we do.
Thank you for engaging me in this conversation.
As to how a lake conicides with it's shoreline or a universe arising consistent with's own laws. Let me give, a hopefully helpful example. Say, we engage in a bet, if 1000 fair dice are rolled and they come up all 6s, you owe me a million dollars, any other combination, and I owe you a million dollars. Now, you and I are observing 1000 dice that I claim to you were just rolled; and look, they are all 6s; you owe me a million dollars. And then in reponse to your incredulity, I simply say that here we are observing it, therefore the probability must be one that this occurred, because, well, there it is.
If I am looking at any occurence that would be HIGHLY unlikely in a completely random setting, then inferring design is not bad logic, it may indeed be the only sound one. Now, in naturalism, randomness is all you have, and I would claim that our universe is incredibly more rare of an occurrence than 1000 6s.
If our universe is the ONLY universe, well, the evidence is strongly in favor of design.
If the explanation is that the only possible outcome is a universe that is consistent with it's own laws, why ask the question. Then I would argue that the hand waving is occuring on your end.
But I think that the only viable explanation to a naturalistic philosophical viewpoint is that since what we observe is a rare event, then there must be a plethora of universes that fail to have life. But now we are making an assertion on what looks like a faith statement based on a naturalistic assumption; rather than a purely scientific approach.
As to examples of something that is more stringent: that seems to fail to understand the argument. if I am trying to explain how something came to be, that is, if it was designed or randomly occurred. Then it doesn't help to say that I can dream up something that would be less likely than this. That dodges the original question of how this seemingly unlikely event occurred at all.
As to waving my hands in magesterium. My claim is that all of those why he/they did this or that questions is patently NOT what needs to be answered. Otherwise, you must explain why life took the way that it did; why evolution chose all of the crazy paths that it did (including converging back on itself). Why are there laws at all? why is the multiverse the way it is?
I maintain that we are both in the same boat on this one. We can both say that there are unknowns that we have yet to discover. And, I would claim that in both camps there are those individuals who approach the why questions in as unbiased and scientific a way as possible, as well as individuals in both camps that do not.
P.S. my mention of evolution above does not imply that I am approaching this as a creation/evolution debate (I am not); or that I do not accept evolution.
Andrew:
First, you are assuming what you are trying to prove. You are assuming that an all-6 roll is analogous to the observed universe, but in fact that is the question that we want to answer. To answer it, we must have evidence or logic- based answers to questions such as 'what is the range of values these constants can have?' And 'is each value in the range equiprobable, or are some more probable than others?' You do not have evidence-based answers to those questions.You have no evidence supporting the notion that this is an all-6 roll.
Here is much better analogy. You've just won the cosmic lottery (congratulations!). But I'm not going to tell you how many tickets you bought or the odds of winning. So now calculate for me your odds of winning the cosmic lottery. You can't; you don't have the data, do you?. You can make some assumptions and calculate what your odds would be if your assumptions are right, but you don't have any real data on which to base the calculation, you just have unevidenced assumptions.
No, you misunderstand. I'm not dreaming up some less likely universe. I'm saying that if you accept that "life improbable, therefore designed for life" is a valid argument for this universe, you must accept as valid other arguments of the type "x improbable, therefore designed for x." Its the same logic. You can't claim the logic is valid when the subject is 'life' and not valid when the subject is something else. The argument you're using is ultimately going to support the universe being designed for the subject which requirest the most stringent set of parameters and historical events. Which is not us.
Cosmic Genetics (Synopsis) by Haddammann .. Instructor Conjunctural Logic of Space.
Sinn-Klyss--Expressão de Uma Mentalidade (blog, portuguese language - Brasil)