Philip Goff has an article in Scientific American, looking at one popular rational for the multiverse, the anthropic principle, or argument from fine tuning:
We exist, and we are living creatures. It follows that the universe we live in must be compatible with the existence of life. However, as scientists have studied the fundamental principles that govern our universe, they have discovered that the odds of a universe like ours being compatible with life are astronomically low. We can model what the universe would have looked like if its constants—the strength of gravity, the mass of an electron, the cosmological constant—had been slightly different. What has become clear is that, across a huge range of these constants, they had to have pretty much exactly the values they had in order for life to be possible. The physicist Lee Smolin has calculated that the odds of life-compatible numbers coming up by chance is 1 in 10229.
Physicists refer to this discovery as the “fine-tuning” of physics for life.
Goff goes on to discuss the idea that if we live in a multiverse, where the laws of physics vary between universes, then our improbable luck in having things just right for life doesn’t seem so improbable anymore, but the result of selection. We have to be in one of the few universes right for life, because if we weren’t, we wouldn’t be here to observe that we are.
But Goff, citing arguments from probability mathematicians, argues that this is a case of the inverse gambler’s fallacy, the idea that since something improbable just occurred, it must be just one of numerous outcomes. It’s the opposite of the regular gambler’s fallacy, that since your luck as been bad all night, you’re due for a lucky break. But for any particular instance of a bet, the probability of the outcomes remain the same.
Steven Novella replies that Goff and the mathematicians are engaging in the lottery fallacy. If you bought a lottery ticket last night, and wake up this morning to discover you’ve won, does that require any special explanation? No. Somebody was going to win, and it turned out to be you, as unbelievable as it might feel.
Novella concludes that either there is some deeper reason why the laws of physics are what they are, or we live in a multiverse and have just won the lottery. (Novella also addresses the issue about whether God or some other intelligence amounts to that deeper reason, but points out the problems with that solution.)
Personally, fine tuning arguments have never been that interesting to me. Certainly the universe appears to be fine tuned for life and us, at least from a certain perspective, but that has always struck me as looking at it backwards. I think the actual reality is that we, and all of life, are fine tuned for the universe. Which makes sense, since we evolved in it. If we had evolved in a different universe, we would be very different.
But, the argument goes, without the fine tuning, nothing like the self replicating patterns we call life could have evolved. My issue with this goes back to the quoted paragraph above, and the idea that physicists can meaningfully talk about what the universe would be like under different laws. Sean Carroll made the point a while back that physicists can’t derive the periodic table of elements from the Standard Model.
Any calculations about what the universe might be like under different laws or constants are going to involve a lot of simplifying assumptions. Every assumption is an opportunity to be wrong. Which means my trust in these types of analyses is pretty low. All I think we can really take from them is that the universe would be radically different with different laws. We should be leery of confident conclusions that complex patterns wouldn’t emerge from any of those alternatives.
Life in another universe would be unimaginably strange, but the idea that it could only exist if that universe were like our own strikes me as pretty anthropocentric, which seems strangely appropriate when we’re talking about something involving the anthropic principle.
So, while I think there are scientific reasons to find certain types of multiverses plausible, I’ve never found this particular line of reasoning compelling. But maybe I’m missing something?
SelfAwarePatterns 
“If we had evolved in a different universe, we would be very different”.
But the point of the fine tuning proponents is that in almost all universes we wouldn’t be here in any form. Life wouldn’t exist. Minds wouldn’t exist.
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Right. But I tried to convey reasons in the post why I’m not onboard with that point.
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Not terribly persuaded by your reasons.
Ultimately I think this boils down to a lack of fundamental understanding of causality. In other words, what is the cause of the constants being what they are? Even if the constants could be different and still result in life and minds, we are still left with the unanswered question of why they are what are in our universe. If there is no cause, they are random and the paradox exists.
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I definitely think the fact that we don’t understand why the laws are what they are needs to be kept in mind. We don’t know that they were random. But I doubt that even if they were random, life isn’t the profoundly improbable thing Smolin and others claims. I remember reading from Victor Stenger that he did his own calculations, probably with different but still plausible assumptions, and concluded that complex structures were a lot more likely than many claim.
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Any reference for Victor Stenger. I would be interested in seeing rationale because it makes intuitive sense to me but as we know so-called “intuition” is usually as often wrong as right.
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I can’t find where I originally read it. It was probably on his old blog on Huffpost, which I’m not sure exists anymore.
But a Google search turns up this paper: https://arxiv.org/abs/1202.4359
Apparently he wrote a whole book on it: https://www.amazon.com/Fallacy-Fine-Tuning-Why-Universe-Designed/dp/1616144432
Warning: Stenger was a strident atheist, in a manner that might turn off many people. A lot of his engagement on this question was within that context.
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I basically agree, Mike, and want to add one more reason. Suppose we know of no reason why the cosmological constant, fine structure constant, etc. had to be what they are in our universe. OK, that shows that there’s a small epistemic probability that the constants would have these values in a given universe. But it doesn’t show a small objective probability somehow built-in to the process that led to our universe or our Hubble-volume. And I think you need the latter, objective probability, to declare a fine tuning “problem”.
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I agree, there may be necessities in the processes that led to the existing laws and constants. Until we understand those processes better, declaring their results improbable seems hasty. In that sense, invoking the multiverse for this specific issue can be seen as prematurely terminating our line of inquiry. I’m a lot more sympathetic to multiverses when they’re a prediction of successful scientific theories. When they’re specifically invoked as a postulate, I’m much more skeptical.
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Re “Certainly the universe appears to be fine tuned for life and us, at least from a certain perspective, but that has always struck me as looking at it backwards.”
It’s also putting us back in the center of the universe. Could we not also say that the universe seems fine-tuned to create black holes? There are more of them and they weigh more than all of us. Or that the universe is fine tuned to create empty space. As the galaxies get farther and farther apart, there is more and more empty space! It is almost as if the universe was created to do just that!
Before I come close to accepting the fine-tuning argument, someone will have to show me that those constants can be different. And, that those constants do not interact to make themselves what they are. Basically, show me that other combinations of the fundamental constants can be made. Otherwise we are comparing the one we got with hypothetical “others” that do not exist.
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Good point. We could also say the universe is fine tuned to produce entropy, which of course, black holes have more of than anything else. In that sense, life seems to be resisting that overall fine tuning. Although before it’s over, life could conceivably end up being the maximum entropy producer if anything like Type III civilizations ever happen.
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[erm, … life has already generated more entropy than if it hadn’t existed].
Actually, that’s a good question. Would entropy necessarily increase in universes with different constants?
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True, life has generated more entropy than if it hadn’t existed. But couldn’t we say that about anything?
It might depend on how we define entropy. Some universes would just quickly collapse back on themselves, but it still seems like at least some entropy would have been generated in the process.
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You said “ We could also say the universe is fine tuned to produce entropy … [L]ife seems to be resisting that overall fine tuning.” I meant to say: on the contrary, life is not resisting that fine tuning to produce entropy. Instead, life is the result of that fine tuning, because life enhances/accelerates the production of entropy.
I don’t have the math skills to address entropy in alternate-constants universes.
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I guess I could have been more clear. I meant that an individual organism, in its homeostatic operations, does resist entropy inside itself. But in the process, it ends up generating entropy. Although, as things stand today, life is far from a major player in entropy generation. Stars leave it in the dust. And black holes are in a class by themselves.
Can’t say I have the math either.
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“And, that those constants do not interact to make themselves what they are”.
That would be a sort of fine-tuning too, wouldn’t it?
I think years ago I saw a Scientific American article (which I can’t find anywhere) that showed there could be other constants which might be able to produce some sort of cosmically stable universe that might produce life. However, there are also a lot of combinations which would be failures – no stars, no planets, or rapid contractions.
There is also still outstanding a question raised by Paul Dirac that the constants might not be constant. The consensus today is they are constant but still periodically somebody suggests the constants could be gradually changing. Certainly when we get to hundreds of billions of years of age (assuming we don’t rip apart or something before then) it might be the constants will be different.
At any rate, the multiverse is about as unprovable as God so I don’t see that solving anything.
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I agree. You are right.
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So Lee Smolin has calculated that the odds of life-compatible numbers coming up by chance is 1 in 10^229? I’ve heard about him from time to time but hadn’t quite decided what I think of him. To me this estimate does not speak well of him. It reminds me of numbers that creationists come up with about how unlikely it would be for life to evolve. In either case I wonder what makes people think they can credibly quantify matters of such complexity? Is my presumption correct that Lee Smolin then uses his estimate to help validate some of his other ideas?
It seems to be as you’ve said Mike, that life found a way given existing physical constants, and specifically given that they’re what’s on the table. Other parameters may or may not suffice, though that’s beside the point. It’s like how we presume there to be other examples of life given the number of planets out there. And they’d have evolved to their own circumstances just as some variety of “life” might be realized under other physical constants. How could we know otherwise? (Given that we evolved for the parameters of Earth however, I consider this to be our only sustainable “space ship”.)
Multiverse speculation already seems relatively supernatural to me, though Goff has now added to my perception by presuming that under this scenario there must be universe versions with different electron masses and whatnot. Naturalism mandates that our constants exist by means of causality however, so even given a multiverse there wouldn’t be branches with different constants. Under naturalism constants shall exist specifically as they’re caused to and not otherwise. For Goff the idea of a multiverse seems quite like a junk box, where everything imaginable will exist somewhere. (So here I seem to concur with Steve Ruis.)
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Actually Smolin’s argument is for a sort of natural selection among universes so it is naturalistic explanation. Black holes create new universes with properties from progenitor universes but also mutations. Eventually stable universes survive.
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Thanks James. So instead of the Everetian multiverse, Smolin is talking about matter being compressed by black holes, and that this effectively feeds new universes which may have different properties, and some of them will fail given those properties while others will be more like ours and so be sustainable enough to create black holes and thus other universes? So then I presume that our universe would be one of countless created by the black holes of other universes, and this also just happens to be one of the amazingly improbable ones which support life.
Regardless you seem to have answered one of my questions, or does he use his estimation that there’s a 1 out of 10^229 chanced that a universe could create life, for the purpose of helping to support some of this other ideas? Yep.
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You’ve got the gist of the theory as far as I understand it. I don’t know how it relates to his calculation but presumably most universes simply collapse or turn out to be completely uninteresting but occasionally some develop stars, planets, and eventually life and those would be progenitors of galaxies of lots of universes with similar constants. Where all the matter/energy comes from to build all of these universes is something I don’t know but it might be addressed in his book.
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I’m with you on not being sure what to make of Smolin. You and James discuss his views on how other universes might be created, but in the little bit I’ve read from him, he was pretty anti-multiverse. He actually came across pretty dogmatic about it. But that little bit was a collaboration, so it’s possible it wasn’t his words specifically.
I agree that currently, Earth is our only ship. If we want to colonize other planets, or space in general, we’ll most likely have to modify ourselves. It won’t be like the historical colorizations we’re familiar with, but more like life migrating to land.
Just to be clear, Goff in his article comes down against fine tuning being an argument for the multiverse. So this is a case where he agrees with us. It’s Novella who argues that fine tuning remains a good line of argument. But like me, Goff doesn’t rule out various types of multiverse.
As I noted to someone else, I’m a lot more sympathetic to a multiverse when it’s a prediction of a scientific theory than when it’s a postulate. In the former, we have to add assumptions to get rid of the other universes. In the latter, we’re just assuming them.
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Okay Mike, I’ve now read Goff’s article. Yes that seems pretty solid reasoning from which to doubt fine tuning. It makes sense to me that he’d be able to present quality arguments from time to time given that he’s a successful panpsychist. How else might someone succeed in academia with such a precarious position in tow?
I suppose you’ve noticed that Sabine did her own version of this post after you did yours. I doubt that this is a full coincidence, but rather that each of you get ideas from similar places. As you know I sympathize with her anti multiverse rhetoric. http://backreaction.blogspot.com/2021/01/was-universe-made-for-us.html?utm_source=feedburner&utm_medium=email&utm_campaign=Feed:+blogspot/ermku+(Backreaction)&m=1
To me the graduation of liquid based life to air based life was utterly destined here given evolution and how well situated our planet happens to be for life in general. Surely you agree. But teleologically rebuilding ourselves (robot equipped of course) for independent space survival? I understand why people would want that to be the case, though the actual logistics of such a proposition utterly eludes me. Yes we can shoot disposable stuff to various places, but sending the infrastructure to build new machines out there given the distances and other parameters, sounds more “fi” than “sci” to me.
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Funny. I had just noticed Hossenfelder’s post and shared it at the bottom of this thread. Yeah, she’s probably watching many of the same sources I am. She makes some good points. I do disagree with her that all multiverse concepts are non-scientific. Some definitely are, but the idea that all of them are, just because it’s the multiverse, strikes me as dogmatic.
It’s easy to see things that already happened as destined, and what we can’t do yet as sci-fi. I’d just note that nothing in evolution is “utterly predestined” (other than in the possible sense of a deterministic universe). That’s not how it works. If we do successfully expand into space, an Eric a million years from now might be talking about how “utterly predestined” that was, and poo pooing the idea of reaching other galaxies.
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Oh come on Mike, an Eric situated in another galaxy in a million years would be utterly amazed that the idiot human could practically get that far rather than sinfully kill itself off in war or pleasure tanks or whatever. The logistics of non terrestrial survival is simply ridiculous, not to mention that if advanced enough we might blissfully vegetate rather than concern ourselves about going anywhere at all.
Regarding Dr Hossenfelder, fortunately I can count on her to not drink the Kool-Aid. If one can explain something that isn’t understood by means of another universe that we can’t otherwise detect, it seems to me that this proposition should effectively be the same to us as magic itself. Though possibly true, to me this seems both unfalsifiable and beyond the realm of worldly causal dynamics.
Hossenfelder’s previous post concerned consciousness, and she was having none of the popular nonsense which irritates me. One person however asked her about her thoughts on McFadden’s theory. This was a med student who read his 2020 paper (and unfortunately misrepresented it a bit by using the “quantum” term). Of course this proposal sounded like standard crap to her. No sign that he’s taken the bait, but I did try to lure him over to our neighborhood. I not only wanted to support his intuitions here, but hint to Sabine that McFadden’s ideas aren’t the standard bullshit that she’s come to expect in the field. http://backreaction.blogspot.com/2021/01/the-mathematics-of-consciousness.html?showComment=1610231966153&m=1#c7386694145013707879
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Eric, your first paragraph is just an assertion of your own views and vehement rejection of anyone else’s. It doesn’t leave any real room for productive discussion.
On this tendency I’m seeing to emphasize Hossenfelder’s PhD status, I would point out that Dr. Carroll, Dr. Tegmark, Dr. Tyson, Dr. Greene, Dr. Vaidman, Dr. Wallace, Dr. Coleman, Dr. Hawking, Dr. Deutsch, Dr. Preskill, and many other doctors disagree with her. I’d also point out that Dr. Hossenfelder is pretty selective in her skepticism, seeing no issue with talking about things like FTL when it’s a notion she favors.
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Her comment is somewhat ridiculous because neither the commenter or anyone else is arguing the brain is exclusively electromagnetic fields. There are probably good reasons to doubt the cemi idea but that isn’t one.
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Right James, except that Sabine answers an insane amount of comments each day, and seems to do so virtually as fast as she reads them. She even picked on this guy for misspelling “substrate”. So it goes…
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Oddly she comments in her reply “Electromagnetic fields transmit the most important interactions in the human brain. They are arguably important..”
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I did go ahead and buy Smolin’s book. BTW, the possibility our universe is a black hole shouldn’t be dismissed out of hand. There are a number of odd coincidences about our universe and black holes.
View at Medium.com
Among other things it provides an alternative to Guth inflation theory that has never made much sense to me.
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I don’t dismiss the possibility out of hand. But the usual versions I read about, involving the holographic principle, seem to need a number of postulates, which seems to make it a less likely proposition than the ones that just fall out of otherwise reliable theories.
Andersen’s version is a bit different. I’ve seen other physicists mention the space time inversion before, but not to say it results in another universe. He presents it as almost inevitable, but I haven’t seen this from other physicists, including some are who quite friendly toward multiverse theories, so not sure what to make of it. Is this Smolin’s version?
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I’ll have to read Smolin’s book to know. Maybe I’ll post something on it.
Dirac (again) has had some interesting ideas on fine tuning constants. Most haven’t stood the test of time but it might be interesting if the total mass of the universe might be related to the constants if not in the way Dirac thought.
https://en.wikipedia.org/wiki/Dirac_large_numbers_hypothesis
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If the universe is a black hole and Hawking is right, then at some point, if not now, the universe will begin to evaporate. I suppose there would be a detectable loss of mass? Would that cause inflation to speed up?
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Actually, black holes emit Hawking radiation throughout their life. So they’re always evaporating. Although they currently take in orders of magnitude more from the CMB than they emit. Most black holes grow a lot in their early life, but then settle down to a relatively quiet existence. The question is, with time and space all twisted around, what would that look like from “the inside”? The timeline outside might be largely orthogonal to the timeline inside.
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What could look like expansion to us might appear to be a collapse to singularity and eventually evaporation to an external universe.
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Definitely, when you start looking at time that way, things get very strange. The topology Andersen described seemed a bit different to me, on “the other side” of the singularity, in a universe “perpendicular” to our own. Not sure how that meshes with Hawking radiation and your point here. But this might map well to the holographic versions where the BH universe is on the event horizon. I have to admit I’m hazy on a lot of the details though.
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I agree with your scepticism about fine tuning, but I think there are very clear grounds for thinking the very notion an irrational one.
Statistics: gathering data and formulating simplified representations of what happened.
Probability: using math tools to predict the likelihood of future events … based on statistics … based on data. We have no reason to suppose that a set of mathematically similar things (e.g. sides of a dice) SHOULD have equal probabilities other than based on the data we collected show that they do. We only know that all our uses of maths of probability in the real world works because we have found that it does, not because we have an a priory assurance that it must.
We have zero data on extra-universe stuff – we have some data on the internals of this universe, that’s all. All attempts to speculate about multiverses is … speculation. The explicit ‘if’ or the implied ‘if’ makes that clear.
We know nothing of the ‘super-physics’ that caused our universe to exist with its physics, as a subset, or whether it’s proper subset or not.
Talking about the probability, or likelihood of these speculative attempts to imagine unknowns is a bad use of probability.
Like Dawkins in God delusion, the ‘likelihood’ of there being no god, on 1 – 7 Dawkins puts his atheism at a 6. What does that a mean, other than a measure of confidence in one’s personal opinion, a hunch? It has no numerical meaning at all. It’s certainly not based on statistical data – and to have no data does not make the probability of gods zero. We only act ‘as if’ it’s zero because there’s no apparent effect of any gods that we can tell.
The Drake equation suffers from the same problem. Yes, it’s a nice list of variables. Something to work on. But for some of them the value could be anywhere from 0 to 1, making it impossible to extract any sense from it.
Fine tuning? The real point about fine tuning is that minor variations in any of the constants make our universe inviable. Yes, all other things being equal … but we have no idea that all other things would be equal, or that many other combinations of constants (inc. ones that we know nothing about) could make universes such that “If we had evolved in a different universe, we would be very different”.
Could there be other universes, which differ vastly from ours, yet have some form of ‘intelligence’ such that entities in it are capable of musing on their own state and the state of their universe? That depends on the physics of what makes universes exist, and what physics can govern them.
Intelligence and consciousness are computational processes of systems that can monitor themselves, as far as we can tell. I see no reason why our universe’s biological machines should be unique in that sense. But we have zero data on whether there are such things, or could be in other universes of different kinds.
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P.S. Sometimes it’s OK to build speculative ideas, like the Drake equation, and still say “We have no idea what to plug in.”
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I don’t think multiverse concepts are necessarily super-physics or pure speculation. Some are predictions of established scientific theories. We have to add in additional assumptions to avoid those predictions. For example, if space is flat, which the most accurate measurements currently show it to be, then the simplest model is that it’s infinite; but if it’s infinite, then a finite arrangement of elementary particles (such as our observable universe) will eventually repeat, resulting in other versions of us out there in the distant cosmos. But it is definitely true that we have no direct evidence for other universes, under any model.
There are many different conceptions of God. Using Dawkins’ scale, for some, such as the Old Testament god, I’m with Dawkins. For others, such as a deistic conception, I’d be more of a 5. And if we’re equating God with the laws of physics, it’d be a 1, although with the stipulation that I’m not wild about using the word “God” in that case.
I think the Drake equation was originally just a thought experiment, to discuss possible factors involved in the prevalence of extraterrestrial life or intelligence. Most of the values have always been speculation. Although some of the earlier ones have become a little less speculative over the decades. But it’s possible to get anywhere from 0 to millions of civilizations in the galaxy. I think Fermi’s paradox rules out the upper bound. Myself, I think unicellular life is prevalent, complex life rare, and intelligent life (involving volitional symbolic thought) profoundly rare.
I totally agree about consciousness and intelligence being computational systems.
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We can’t help ourselves. Cosmic navel contemplation is our affliction. Ultimately, the only way to find out the answer to all of these questions is to die. See you on the other side. Or not.
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Can’t say I’m optimistic on that front. I think oblivion awaits. But it’s worth noting that we visit oblivion every night. And at least we won’t be on the other side alone, unhappy that we’re missing out.
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Not a fan of philosophical anthropic arguments, multiverse fantasies, or Philip Goff. 😉
Maybe the universe is fine-tuned; there are some strong arguments that it is. A small change in the weak force, for one example, and stars don’t work (because fusion doesn’t). A small change in various coupling constants and atoms don’t work or particles don’t interact. Not universes where life is unlikely, but universes where nothing is likely. And it does seem as if there are vastly more of those than friendly universes that allow coherent structure.
But maybe that’s just the way it turned out. (And aren’t we glad!) I agree with Ron Murphy’s point above. It’s impossible to discuss the probability of something like fine-tuning or multiverses when there is no empirical probability distribution for those things. You can’t measure something without a measure.
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I can understand not being a Goff fan. For a while, it seemed like every article about consciousness was by Goff trying to make the case for panpsychism. But like Chalmers, I try not to filter him out. He does write about other things, and sometimes it’s interesting stuff.
In this case, one thing I didn’t make clear enough in the post, is that Goff actually does not agree that fine tuning is a good argument for the multiverse. It’s actually Novella, in his response, arguing that it is. So this is a case where Goff agrees with those who don’t buy the fine tuning argument. Although in my case, I come to the conclusion from a different path.
The philosophy of probability is an interesting and complex thing. Both you and Ron seem to be taking a frequentist interpretation. But there are others. https://en.wikipedia.org/wiki/Probability_interpretations#Philosophy
In particular, there’s a view of probabilities as relative to an observer, so the probability of when you will publish your next blog post is different for you than it is for me, because you have information about it I don’t. We can’t perform empirical measurements of what’s going on inside the core of stars, but we can still extrapolate from what we know, and often derive probabilities of something like when Betelgeuse will go supernova.
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I understood Goff’s position, but ‘even blind squirrels…’ 😉
(Full disclosure: Lately I’ve been asking myself how much value modern philosophy has. I have reverence for the ancients who built the building, and I think learning philosophy has value, but I’m not sure practicing it these days does. Even Chalmers, who I rather align with,… I just ain’t interested. I’ll get my science fiction guesswork from actual science fiction authors.)
The thing about stars, as Dr. Hossenfelder points out about pens, is that we have (literally) billions of observations of physical stars and a physical theory that’s been tested and validated in our fission and fusion efforts.
Even so, speaking of Betelgeuse, when recent observations showed a dimming in the star’s output, many expected a coming supernova (which I admit would have been so awesome). Others expected another explanation. Which all says a lot about the importance of an empirical probability distribution. (And reminded me of the “FTL neutrinos” at OPERA.)
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I’ve always said that the problem with philosophy is much of it is garbage. The problem is no one seems able to agree on what is or isn’t garbage. But I still think it at times plays a valuable role in clarifying definitions and coming up with hypotheses and theories. It’s just not useful, usually, for falsifying those hypotheses and theories.
We do have billions of observations of stars, but not one observation of a stellar core. Everything we know about what happens in a core is based on theory. Most of what we know about what happens in and around black holes are theoretical predictions, some of which have only been recently confirmed. And even when we do conduct observation, it’s always through the lens of theory. All observation and measurement is inescapably theory laden.
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For me the value of philosophy lies in the mental discipline and in the history of the philosophical trail blazers (Plato, Kant, etc). I’ve been extremely underwhelmed by modern philosophical work, which mostly seems to be a fine sifting of very well-plowed ground.
“We do have billions of observations of stars, but not one observation of a stellar core.”
But, as I said, “and a physical theory that’s been tested and validated in our fission and fusion efforts.” Our reactors and bombs have given us glimpses into the heart of stars. Our experience with chemistry, especially nuclear chemistry, also has provided experimental data. That’s a vastly different situation than with any multiverse hypothesis.
I do agree black holes involve more unknowns. To the point some still continue to doubt their existence. Certainly they involve conundrums we don’t understand (the singularity, the information paradox, etc). I am not a fan of the various physical analogues that have been cooked up in labs. I just don’t see that water draining down a hole is really anything like a black hole.
“All observation and measurement is inescapably theory laden.”
Of course! The trick is not letting one’s imagination run away.
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Turns out that Sabine Hossenfelder did a video on this topic this morning. She discusses probability too, although acknowledges the frequentist issue, and goes into an alternate Bayesian interpretation.
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I noticed your comment to Eric:
“[Dr. Hossenfelder] makes some good points. I do disagree with her that all multiverse concepts are non-scientific.”
She’s kind of a hard-liner and takes a purest approach, although I do think the point is well-taken. I think it depends on how one defines science. If it’s the observation and analysis of the physical world, then she’s right. If the definition is broadened to include theory-based guessing about things, then not so much. It almost boils down to where one draws the line between doing philosophy and doing science.
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The phrase “theory-based guessing” is a good one. It sounds bit better than the one I’ve been using: “loose speculation.” As I’ve noted before, I don’t think there’s a bright line between science and fantasy, but more of a spectrum.
1. Reliable knowledge
2. Rigorous extrapolation
3. Loose speculation (guessing)
4. Falsified notions (fantasy)
Science needs 2. Arguably even 3 has its place during brainstorming to find 2. “Hardliners” have a tendency to relegate theories they dislike to 4. But most are inconsistent and try to push guessing they favor to 2 (Hossenfelder in particular seems interested in FTL concepts.). Often, it’s just privileging their own theoretical biases.
Anyway, a lot of multiverse theories are in 3, but some are in 2, predictions of scientific theories. We have to add in assumptions to prevent the other universes from falling out. Of course, since we can’t test those predictions, it’s always possible some unknown factors will make them wrong, but historically those unknown factors haven’t tended to make the situation closer to our intuitive view of reality, but to pour gasoline on the strangeness.
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I think you might need a middle category, 2.5 Loose extrapolation because, in my book, no multiverse theory can be said to be “rigorous”. To me rigorous extrapolation would be deducing positrons or neutrinos. Or, for that matter, quanta or quarks. These are all cases where the math and the experimental data demanded an explanation for an obvious “hole” in our understanding.
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Yeah, the four categories I came up with were mostly just to clarify that it wasn’t just a dichotomy between settled science and fantasy. But each of those categories could be subdivided much further. However, “loose”, to me, implies postulates, assumptions, either a lot of them, and/or ones involving major conceptual concessions, which puts something in 3.
A better criteria for different levels of 2 might be how much “terrain” exists between where a theory has been tested and what predictions we’re talking about. The farther that distance, the higher the possibility of those other factors cropping up, the unknown unknowns. So if space is flat, then the simplest prediction is that it’s infinite, with all the weirdness that implies, but that’s also a lot of terrain for unknown factors to emerge.
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Yes, quite! The gap between observational data and what the theory says is a very good litmus test. That’s why I’m askance at any multiverse theory — the gap is about as big as can be.
As we’ve discussed before, space can be flat and bounded. Assuming space is infinite requires accepting that anything physical can be infinite — a premise science tends to reject. If one treats “nothing physical is infinite” as axiomatic, the simplest prediction is that it’s bounded (and there are geometries that allow that).
That’s the thing with speculation. It depends on the assumptions that frame it.
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Right, but assuming space is bounded or that nothing is infinite are themselves speculative assumptions. We have to add assumptions to prevent the strange consequences. If we just go with general relativity and flat space, then the quilted multiverse falls out of it.
And of course, adding those assumptions adds new difficult questions: if space is bounded because of a certain shape like a flat torus, then what does that torus exist in, and what is its extent? Is it itself in its own torus in yet some even broader realm?
Reality is inescapably absurd.
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Absolutely! 🙂
The bounding isn’t the assumption; it derives from assuming space can’t be infinite. It’s the axiom “nothing is infinite” that’s the assumption.
The argument is based on current physics. There is no infinite energy or mass or density or temperature. One reason we know GR isn’t a full story is that it predicts infinite curvature at the singularity. (“Singularity” in general is a kind of infinite thing which is why singularities are rejected.)
So there’s a long precedence for the axiom that “nothing is infinite” — it’s well grounded. The assumption “the universe is infinite” is beyond current physics, thus more speculative.
That said, the geometry of bounded space is unknown although mathematics offers some possibilities. You implied one mentioning a flat torus. That requires a higher dimension, and that kinda balances the speculation. The assumption of an infinite 4D spacetime versus the assumption of bounded one embedded in a higher dimension. Pick your poison. 🙂
Question: How does a “quilted multiverse” fall out of GR+flat space?
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The quilted multiverse is Brian Greene’s name for what Tegmark calls the Level 1 multiverse, infinite space. If space is infinite, and the possible patterns of matter in the observable universe finite (very large but finite) then that pattern would eventually repeat itself an unimaginable distance away. It would actually repeat itself an infinite number of times and in every variation. So there’d be an infinite number of us having this conversation.
Of course, if space is bounded, that goes out the window. But then the question becomes, how many shapes like our universe are “out there” in the higher dimensional bulk? If that is infinite, then might our precise shape not eventually repeat itself, putting us right back where we began? And if there’s only one torus or whatever, then that would definitely beg for an explanation.
Unless reality just…ends in some manner, which seems difficult to conceive. Maybe we hit a wall, dig through it, and find out we were in a grain of sand on a beach the entire time. Or on a turtle’s back. 😛
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😀 My question was: “How does a ‘quilted multiverse’ fall out of GR+flat space?”
It’s worth considering what’s involved in the assertion “there’d be an infinite number of us having this conversation.” Or even just two. The numbers involved are staggering.
This is similar to the idea the infinite digits in the decimal expansion of pi contain every possible finite number. And therefore every JPEG, GIF, sound file, text file, etc possible. One can calculate the length of random digits necessary to statistically guarantee finding a number of a given size. IIRC, for 10-million digits, all possible 6-digit sequences existed (several times over) but 7-digit sequences had a low probability.
One can try to imagine the vast number of digits required in guarantee all JPEG-length sequences.
The amount of data contained in a single universe instance in a Level 1 multiverse is a bit more than contained in any JPEG. Special notation is required for numbers that large.
A higher dimension doesn’t have to require multiple embedded spaces (and we shouldn’t pile speculation on speculation). The geometry may simply amount to there being additional degrees of freedom not accessible to us. (Notions along these lines might also “solve” non-locality.) We might think of it as a “meta-mapping” of spatial points — a mapping that transcends our 3D notions of distance.
As you said, ultimately something very very strange is axiomatic. In terms of time and space, where does it begin and where does it end? If in fact it does.
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Hi Mike,
I agree with most of what you’ve suggested here.
One thing you wrote, was that some proponents of the so-called fine-tuning crisis have it backwards. Paraphrasing, it’s not the universe that is fine-tuned for life, but life that has adapted itself to the universe. I tend to think this is one of those cases where both are true, and neither perspective is right on its own, while both have a certain validity.
I found a paper attributed to Stenger on this issue on the web and read it. He didn’t calculate (in this paper) the probability of complex life, but he reduced the number of dials available for tuning the universe to just four–which he explained as reasonable for reasons I didn’t completely follow–and then showed that there was a wide range of settings of these dials that would yield universes with long-lived stars, those being the fundamental prerequisite for the heavier elements associated with life. So he didn’t seem to think a universe fit for life was as starkly improbable.
He made some points that are interesting imponderables on their own, like the carbocentricity of views that life will always be carbon-based like ours. But he is very content to chide people for not being more open-minded, and offers no real substantive commentary on what life is or how other chemical platforms might achieve those criteria. That’s probably why he wrote a book though–this was just a summary level paper. But the question is an interesting one: what are the minimum capabilities a particular chemical platform must possess to serve as the platform for complex life, and can we demonstrate those are all achievable with some other selection from the periodic table than the biochemistry of life with which we are familiar? I have no idea. As a simple example, it seems inert gases probably won’t work because they don’t react with other compounds. I’m just curious I guess if you’ve ever seen a list of the chemical faculties a given group of compounds must possess to exhibit the dynamic stability of living systems?
Stenger’s use of computers as an example of an alternative, using a silicon-based platform, doesn’t really seem like a great proof of concept. But that may be because it’s hard to see computers as something self-forming in the environment given they are so conceptually tied to human invention. To posit this as a viable alternative to carbon-based life forms, I think you’d have to show a “smallest computer” that could spontaneously form in the environment, with silicon as it’s fundamental chemistry, that had a far from equilibrium (open system, with flow of energy from the environment) disposition and self-replicating potential. I have no idea if that is possible or not!
Michael
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Hi Michael,
I have to admit it’s been several years since I read Stenger’s writing on this topic. And it’s definitely true that he had to make a lot of assumptions in his calculations. Maybe not all of them were valid. However, those claiming the improbability of life are also making a lot of assumptions in their calculations. And since fine tuning advocates are the ones making the claim, I put the burden of proof on them.
What the chemical and physical prerequisites are for life is an interesting question. If you read astrobiology, this is a long running debate. Some insist that any viable life forms will have to be carbon based, which raises the issue of what would have happened if carbon had never been around. Others see possibilities on the periodic chart as alternatives. Silicon is often thrown out as one.
I’m only lightly read in this area, but what I’ve seen hasn’t made me think there’s an obviously right answer. It is plausible that in a universe with carbon, carbon is the most energy efficient way for life to form. It might take far longer for silicon life to form, and require very different conditions, perhaps requiring a universe far older than ours is at this point. But I don’t know.
And it seems like once we start talking about another universe with a different set of laws, all bets are off. The real question then becomes, how many of those universes are able to form complex structures at all? I think it’s fair to say many wouldn’t form anything interesting. But that’s a long way from the figures fine tuning advocates throw out.
So, lots of unknowns. Some of them, like alternate substrates, might become clearer if we ever discover any other biospheres. I suspect when that happens, we’ll discover just how limited our imaginations have been, constrained by the only examples we currently have.
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Just consider where carbon and silicon are in the Periodic table to see why people think silicon might be a basis for a biochemistry. They’re in the 14th group, elements with four valance electrons, which generally means they bond well with other atoms or themselves. Both can form polymers (long chains of atoms), and polymers seem important structural components.
OTOH, it’s a heavier atom, which has some consequences, and some silicon compounds are problematic (they burn when exposed to oxygen or water). But there are carbon compounds that do that, too, and carbon-based life just doesn’t trade in those compounds.
I have a memory of having read an article about silicon life that essentially said it was possible but fairly unlikely, at least in this universe. AIUI, there’s a reason we see all sorts of organic forms of carbon, but most silicon is in silicates (rock, sand, etc).
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The fact that silicon takes more energy makes me wonder if it’s possible that Earth, early in its history, like in the Hadean, might have had a silicon biosphere, which as the Earth cooled, died out, giving way to the carbon one we know today. I don’t know that it would have left any fossils we’d be able to recognize.
Just a bizarre, probably impossible scenario that just occurred to me.
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Now that’s some speculation! 😀
It would certainly be a lot more likely before oxygen was around.
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One strike against silicon in my book–(depending on how we wish to define life)–is that carbon seems to work out pretty well in exchanges between the atmosphere and the sea. Carbon is always “in circulation” because it is released as a gas when metabolism occurs, and then on the other hand may be absorbed. And this occurs in the seas as well. Silicon, being heavier than carbon, forms sand instead of a gas when oxidized, so it just seems tricky to understand how a life form would be constantly producing and excreting sand as a product of its metabolism? I suppose it’s possible. Just… things get weird pretty quick when the respiratory processes of every cell in your body revolves around excreting sand… There’s probably ways to solve that, but it seems clear that life would be EXTREMELY different if it was based on an altogether different chemistry.
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Excellent points!
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quote
So, let’s contrast silicon and carbon. They can both form four bonds. On Earth, silicon is far, far, far more prevalent than carbon. Basically, silicon is found in sand and rock. In the Earth’s crust, silicon makes up 28%. Carbon, in contrast, is about 1,000 times less common. Yet carbon makes up life, while silicon doesn’t. If silicon were a contender, the fact that it is so common would give it a huge advantage.
So why does silicon fall short? Well, to begin with, when carbon makes four atomic bonds with all of its neighbors, the bonds tend to be of the same strength. In silicon, the first bond is much stronger than the others, which means the first bond is far more stable than the others.
It’s because the first bond is formed when the electrons from each atom reach directly to the other atom in a metaphorical handshake. The other bonds are formed from electrons that are further away and they effectively don’t get as good a grip.
Another thing is that when carbon connects with other chemicals common in organic molecules, the bonds are of similar strength. Carbon–carbon, carbon–oxygen, carbon–hydrogen, and carbon–nitrogen are all pretty similar. That means that, from an energy point of view, it is pretty easy to swap out atoms, which is the physicist’s way of saying that chemical reactions occur.
However, the silicon–oxygen bond is much stronger than say silicon–hydrogen, or silicon–carbon, or even silicon–silicon. That means that once silicon interacts with oxygen, it’s very hard to break them apart. This makes the ease and versatility of silicon chemical interactions far lower than the ones involving carbon.
And, about that silicon–oxygen bond compared to the carbon–oxygen one. When you breathe, you take in oxygen and breathe out carbon dioxide, which is given by the chemical formula CO2. The corresponding silicon molecule is SiO2 or silicon dioxide. The more common word for that chemical compound is ‘rock’.
Thus, a silicon-based creature using oxygen as part of its energy cycle would be breathing out sand. This isn’t a new realization. In 1934, science fiction author Stanley Weinbaum wrote a story in the pulp fiction magazine called Wonder Stories of an expedition to Mars. The astronaut encountered a life form that was gray, with one arm and a mouth that extruded bricks. He realized that the bricks were the product of the creature’s respiration.
So, while a simple understanding of the chemistry of carbon and silicon suggests that silicon-based life is possible, if you dig a bit deeper, it seems that silicon-based life isn’t really all that likely.
https://www.thegreatcoursesdaily.com/misconceptions-of-science-is-silicon-based-life-possible/
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Excellent, thanks! This rings a lot of bells.
(As an aside, carbon is more abundant than silicon IN SPAAAAACE! 😀 )
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In one of Don Lincoln’s books there is a great diagram that shows how silicon couldn’t produce the complex chemistry that carbon does.
At one point, I was planning a post about the odds for various commonalities in life across the universe. Carbon-based was one of the attributes I thought to be highly likely. Primarily using water as solvent was another. That would imply that it would develop most likely in a temperature zone of liquid water, although it can obviously survive outside that range. Cellular organization seemed pretty likely – it would be hard to participate in evolution without discrete units of some sort.
Right now I think DNA/RNA based might even be fairly likely although perhaps less so than the others. I think I saw something recently about a synthesis that could produce DNA without requiring special enzymes.
https://www.sciencedaily.com/releases/2020/12/201228095428.htm
ATP for energy transport was another with further declining odds. It seems pretty ubiquitous across life on earth.
https://biologydictionary.net/atp/
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Speaking of elements IN SPACE, while I tend to get bored with computer games quickly, I got a bit hooked on this simple one (based on the popular 2048 game, which I’m also a bit hooked on): http://dimit.me/Fe26/
Be sure to read the Fusion Guide carefully or you won’t get far!
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I find the idea of a multi verse compelling. although the “evidence” for one seems slim to non-existent, currently.
I am with you however to this extent. We exist because blind evolution cobbled us together with the laws of physics it found here. If they had been different, so would we.
And so as you say, in different universes, radically different life would have evolved. Or not as the case may be.
So “fine tuning” seems to be BS. Each universe will evolve according to its own laws. Whatever those may be. Perhaps some weird form of life is consistent with those laws and does evolve. Perhaps not.
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Hard data is definitely lacking. I don’t think confidence in any multiverse theory is justified. When we talk about them, we’re talking possibilities. Some, I think, are more likely than others. But it’s possible none are reality. Although I don’t think confidence in that answer is justified either.
But I agree we’re on much firmer ground with evolution and natural selection. That selection has, over billions of years, made us fine tuned to our environment.
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“Novella concludes that either there is some deeper reason why the laws of physics are what they are, or we live in a multiverse and have just won the lottery. ”
The odds of being just one number short of the winning lottery ticket are vastly greater, though. And the odds of being two number short of the winning ticket are even greater. So we would expect to end up in a universe that was just short of perfect. In other words, it should be a universe that is just about to collapse in on itself. But it doesn’t appear to be like that so I would take that to mean that there is some ‘deeper’ reason. I don’t think you can just make a case for chance in a multiverse. The laws of probability say that we should not end up in a finely-tuned universe. Mike.
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Dr. Michael,
Not sure if I follow your reasoning here. If there is fine tuning and there is a multiverse of varying laws and constants, then I’m not sure why that couldn’t be how we ended up in a fined tuned universe. It’d be the same as saying that the odds of Earth having the right conditions for us are very improbable, and that we can’t use the fact of innumerable other planets in the universe where the conditions aren’t tuned for us.
I do agree with Novella, that doesn’t mean there is such a multiverse and we can rule out some deeper reason.
But as I noted in the post, I’m not convinced this is a problem that really needs a solution anyway.
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It could be how we ended up but the probability of this being the case is low. The example of the planets is a useful analogy. If we could visit all the planets in the universe (hypothetically) we would expect to see a few that are earth-like but many more that are just slightly less that earth-like (perhaps with less vegetation and lower order animals). And below this there would be many many more that are even less earth-like. And so on down to the inhabitable planets (gas giants and rocky barren planets) which should constitute the vast majority of planets.
If we were to randomly select one planet it would be very unlikely that we select earth or an earth-like planet. We’d probably get an inhabitable planet where the conditions for life are not fine-tuned. (That’s not to say we might select earth or earth-like, but the probability is very low).
Since we are on earth where the conditions for life seem to be fine-tuned, I would suggest that planet formation and life doesn’t follow a normal distribution. I would expect to have been born into a world where life was just about to die out. It seems quite stable though (although humans certainly seem to be trying their best to reverse this!) The probability that we have been born into a pristine, stable earth seems quite low to me.
Which suggest there is likely to be some other explanation for planet formation that we have not yet discovered. It is not just a random assembly of laws and consonants.
The same with our universe. If it is just one from a mutliverse with a random selection of laws and consonants, why is our universe not one of the more degenerate ones – still one with conscious life that can ponder the question we are pondering now, but one which is just about to cease to exist?
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“But Goff, citing arguments from probability mathematicians, argues that this is a case of the inverse gambler’s fallacy, the idea that since something improbable just occurred, it must be just one of numerous outcomes.”
This is a strawman. By definition, something improbable is one of numerous *possible* outcomes, but no one argues that the other ‘verses of the multiverse *must* exist simply because they are possible–rather, the multiverse is offered as an *explanatory theory* for the probabilistic nature of physical law.
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