You think there's a multiverse? Get real

[marcus]

To be clear, I wouldn't say these people are arguing AGAINST the multiverse idea. If you like the idea you can believe in it, if you want. It is just not a scientific idea.
They are explaining why there is no compelling scientific case for it. And there are alternatives which appear compatible with observation and which may not be so "flexible". :)

 

[MattRob]

So the test is: that if the universe dissolves in a sea of fire then "there are fundamental scalars in the universe that have metastable ground states" and therefore the multiverse exists.

As this process of transitioning to a lower energy state, this “vacuum decay,” would create a bubble of a new vacuum state that would expand outward at the speed of light then we wouldn’t have any warning until we were obliterated.

The hypothesis "the multiverse exists" would have been proven true but only by the destruction of the whole universe and when there was no-one left to appreciate the fact.

Some test!

Actually gargantuan energy levels are probably necessary for this transition to occur and we are (probably?!?) safe yet.

But it illustrates the problem of testability. We are building theories about energy levels far beyond testable limits (particle colliders bigger than the whole Earth etc.) and the fact that we can construct a theory that is mathematically consistent is no guarantee that that is or was the way the universe actually works/ed.

Garth

If I recall correctly, the amount of energy required for this to occur exceeds the amount of energy density that would form an event horizon in our cosmos' current state, so perhaps we're permanently safe from this because even if it did happen as a statistical fluke of QM's randomness, then it'd contain itself in a (at least microscopic) black hole which would quickly evaporate away? Heh, that's an almost Hitchhiker's Guide kinda idea. Universe-destroying phenomenon occur in intergalactic space on a regular basis. Fortunately, they're quickly contained in black holes every time and quickly vanish by Hawking radiation without a trace.

Anyway to recap what I pointed to in posts #41, 42, 43 and elsewhere, what we are seeing is some world-class experts in cosmology (George Ellis, Joe Silk, Slava Mukhanov, Paul Steinhardt, Robert Brandenberger,...) explain why there is no compelling scientific case for "multiverse".
1. "multiverse" thinking rests mainly on the mistaken idea that INFLATION necessarily must run hog-wild and generate a huge mulitiplicity of separate expanding regions.
But Mukhanov says no: you can have inflation without "selfreproduction" (post #41)
2. Furthermore the inflationary paradigm may itself be too FLEXIBLE to be properly tested, says Steinhardt. It seems able to adapt to any set of observations that comes up, suggesting that its status as science is shaky and it may be time to develop and study alternatives that achieve the same good results. (Steinhardt's Nature article "Big Bang Blunder Bursts Multiverse Bubble", post #42)
3. Finally, Robert Brandenberger and others including a close collaborator Yi-Fu Cai, have been developing bounce cosmologies which do not need inflation in order to achieve the desired results of near flatness, sameness in all directions, and evenness of fluctuation spectrum. There is much recent work along these lines so I will simply take as an example a paper by Cai&Wilson-Ewing which was titled "LambdaCDM Bounce". Essentially it takes standard cosmic model, puts it through collapse, rebound, expansion, and checks that the results are compatible with current observations. (post #43).

Once again, I don't see why "do not need" should be a strong argument for something. It seems somewhat arbitrary to add a constraint that universes cannot reproduce. Also, once again, yes, anything that can happen will happen an infinite number of times, but that's also technically true in an infinite spatial expanse within our universe; yet that does little to muddle physics. Also, given the sheer size of the visible universe as contrasted to fundamental particles, extremely unlikely things can happen with QM quite easily; but once again this is non-issue because we still respect events' respective likelyhoods, rather than their possibility.

[...]
Equally the reason the Multiverse argument is wrong is because in Inflation we have a theory in which, amongst the infinite number of patches/universes, in the words of Alan Guth, "anything that can happen will happen—and it will happen infinitely many times". So no only is there no predictive power but also, satisfied that we have explained 'everything' by the multiverse, we have no motivation to find the real reasons for the natural phenomena that lay within fundamental physics and the origin of this universe.. [...]

Because of the probabilistic rather than deterministic nature of QM, the same thing could actually be said of it. Could I quantum tunnel through the floor at any given moment? Technically, yes, but the odds are so slim it's truly non-issue. Likewise, yes, there is a universe where everything just happens by insane chance, but that's really non-issue because it's so unlikely.

Furthermore, if our universe is infinite, then out there there's an infinite number of identical copies of me falling through the floor due to quantum tunneling; but I'm really not bothered because I know there's more(?) who aren't, and by probabilities, I'm really much safer from that threat than, say, poor dietary habits.

All that being said, I do agree on the principle that scientific theories need to be testable to be science, with a cautionary note that sometimes non-testable, or even simply wrong heuristic models may sometimes still be helpful in making other discoveries (such as Galilean approximations, or interpretations of QM). And furthermore, sometimes theoretical advances simply outpace observational capabilities. The schwarzchild solution existed long before we ever had the tools to discover AGN, probe their natures, or discover Sagittarius A. While it's a very rare occurance for theory to outpace observation with success, it is, nonetheless, possible, and perhaps even necessary given the increasing difficulty of yielding experimental results.

On that note,

[...]

But it illustrates the problem of testability. We are building theories about energy levels far beyond testable limits (particle colliders bigger than the whole Earth etc.) and the fact that we can construct a theory that is mathematically consistent is no guarantee that that is or was the way the universe actually works/ed.

Garth

I remain somewhat hopeful that they'll find new and clever ways to experiment, much akin to interferometry making radio studies of the cosmos possible. Simply put, you don't know what you don't know, so hopefully some ingenious solutions will come along to get the effect of colliders bigger than Earth without needing actual colliders that large.

 

[Garth]

I was sort of hoping to emphasize that contrary to your claims that there is predictive power by theories that involve the multiverse as a byproduct. That they frequently do make very specific physical predictions that *are* observable and that already have been observed and that could have been falsified many times in the past.

In the past thirty years or so I have worked through countless versions of Inflation theory, each making different predictions. In the words of Paul Steinhardt

Over the entire multiverse, there are infinitely many distinct patches. Among these patches, in the words of Alan Guth, "anything that can happen will happen—and it will happen infinitely many times". Hence, I refer to this concept as a Theory of Anything......

Inflation, once started, runs eternally and produces a multiverse of pockets whose properties vary over every conceivable possibility—flat and non-flat; smooth and non-smooth; scale-invariant and not scale-invariant; etc. Despite laudable efforts by many theorists to save the theory, there is no solid reason known today why inflation should cause our observable universe to be in a pocket with the smoothness and other very simple properties we observe. A continuum of other conditions is equally possible. In string theory, a similar explosion of possibilities has occurred, driven by attempts to explain the 1998 discovery of the accelerated expansion of the universe. The acceleration is thought to be due to positive vacuum energy, an energy associated with empty space. Instead of predicting a unique possibility for the vacuum state of the universe and particles and fields that inhabit it, our current understanding of string theory is that there is a complex landscape of vacuum states corresponding to exponentially different kinds of particles and different physical laws. The set of vacuum space contains so many possibilities that, surely, it is claimed, one will include the right amount of vacuum energy and the right kinds of particles and fields. Mix the inflation and string theory, and the unpredictability multiplies. Now every combination of macrophysical and microphysical possibilities can occur.

The only prediction that Inflation has made is that the universe should be nearly flat. It seems to be extraordinarily flat, and I expect there is some version of the theory out there that can accommodate this. Other theories also produce a flat universe, so the prediction is not unique to inflation.

As PS said all the other 'predictions' were really cases of model fitting - with a continuum of possible models to fit from.

And now the prediction of a gravitational wave signature in the CMB is in the balance. The prediction was of a B-mode polarisation signal of strength 'X', but ~2'X' was observed. Planck has shown that in that area of sky the B-mode polarisation signal from dust is ~2'X'+/-error bars.

There is still a possibility that a primordial gravitational wave signal might be hidden in the error bars and it is that which is being investigated now; it will take two years to get the experiment together.

Whatever that balloon experiment finds it will mean that if there is a primordial gravitational wave signal hidden in there it will be far smaller than the one predicted, but hey! we can find another version of inflation that will 'predict' that.

As for the second paragraph. Sorry, I don't follow the argument or the claim. Are you really saying that you don't approve of spontaneous symmetry breaking as a physical process, and instead need to look for explicit symmetry breaking?

I was saying three things:

1. The presumption that the process was 'spontaneous', that it was a stochastic process, implies a large/infinite ensemble of possible universes - the multiverse, which has been fed into the theory as an a priori assumption.
2. We don't know if the symmetry breaking was spontaneous - there might be other physical factors in some yet to be found TOE that make the process one of Explicit symmetry breaking.
3. We will never find that TOE if we have satisfied ourselves that we have already found the answer in an untestable and infinite possibility multiverse 'theory of anything'.

So yes, in this cosmological case I don't approve of spontaneous symmetry breaking as a physical process because it is unscientific and it short circuits further scientific investigation. Again as Paul Steinhardt said, "Because an unfalsifiable Theory of Anything creates unfair competition for real scientific theories".

Thank you Marcus for the link to PS's Nature article, which also emphasises what I say about the BICEP2 results.

I repeat Marcus' quote from PS with just one line: The answer given by proponents is alarming: the inflationary paradigm is so flexible that it is immune to experimental and observational tests.

Garth

 

[mitchell porter]

My 2 cents:

We should distinguish between:

a theory which makes plenty of testable predictions, and also has the untestable implication that there is a multiverse

a theory which posits a multiverse and obtains a testable implication from thisA theory in the first category might be... standard model plus chaotic inflation. The evidence for chaotic inflation would come from standard cosmological observations, but along with implications for CMB etc, the theory would imply the existence of other inflating regions that are eternally out of reach to us. (That is the weakest sort of "multiverse" because they are in our space-time, but inaccessible.)

A theory in the second category might be... some "theory" (guesswork) about the string-theory landscape, plus eternal inflation. In the previous example, the physics in every inflationary region is standard model, standard model, standard model. In this case, there is a guess that e.g. the extra dimensions curl up differently in different inflationary regions, so there will be a different effective physics; and then one would contrive to predict things about beyond-standard-model physics (and retrodict things about standard-model physics) on the basis of e.g. reasoning about what kind of effective physics is most common in the landscape.

 

[Haelfix]

A few comments about the word games being played here, and Steinhart's 'argument'.

It is important here to distinguish between an idea and a model (I choose to not use the word 'theory' here, as it is being overloaded). The inflationary paradigm is an idea, a specific instantiation of that idea is a model, like say m^2 phi^2. Models are relatively easy to falsify as they always make very specific predictions, ideas on the other hand, are very difficult to kill off and sometimes impossible.

Another example of this is the idea that there exists particles beyond those catalogued in the standard model of particle physics. A specific instantiation of that idea, is say a new Dirac Fermion with a certain mass and set of couplings.

Before we go claiming that we should only deal in 'scientific' ideas, consider that the latter example is completely unfalsifiable, even in principle, yet it is the very thing that every working physicist spends most of their life contemplating.

So... One of the many problems with Steinhart's arguments, is that he claims that the inflationary paradigm is unfalsifiable, and then gives as an alternative, a specific model. You see, it's completely disengenous, b/c he knows perfectly well that his more general idea, the 'ekyprotic universe' is very much as hard to falsify as inflation is. This holds for all of the alternative ideas, like the bounce paradigm, and so forth. Further all of these 'alternative ideas' have only made retrodictions, inflation was the first to actually make a nontrivial prediction that stood the test of experiment.

Now, the notion that inflation predicts anything you want with a multiverse is just not correct. Here's what Steinhart is talking about. It turns out that a very specific set of inflationary models that happen to inflate eternally, will, if you tweak things in a very specific way (eg by making a manifestly *wrong* choice of measure amongst other things) will break many of the assumptions that keep the mathematics under control (slow roll,a proper phase of reheating, etc). This then leads to regions of space that have bizarre physics with high probability.

So instead of simply throwing those solutions out, he chooses to keep them and then use them as a representative of the whole idea.

An analogy is worth pointing out. It would be as if someone told you that the idea of General Relativity is not scientific, b/c a certain solution (say the Godel Universe) violates cause and effect, and can give you anything you want. Therefore GR can't make predictions! It's just not a reasonable claim.

Anyway, the right way to proceed is to keep working on all of these ideas, gathering data, and then seeing which models survive. It is perfectly plausible that a model like m^2 phi^2 turns out to be the only one left standing at some point in the future (with more refinement of the r-ns plane), at which point people should be prepared to accept that there will be more 'believers' in notions like the multiverse and that this is, as it should be. People will have simply updated their Bayesian priors, exactly as science is always done.

 

[Garth]

It is perfectly plausible that a model like m^2 phi^2 turns out to be the only one left standing at some point in the future (with more refinement of the r-ns plane), at which point people should be prepared to accept that there will be more 'believers' in notions like the multiverse and that this is, as it should be.

Now I wonder why you say that? It sounds like you are already a 'believer' in the inflation paradigm. But science isn't about believing, it's about observing, testing and verifying.

Garth

 

[nikkkom]

This is not quite true, as I shall explain. Once you accept the type I multiverse (in Tegmarks classification) through a certain chain of reasoning, the jump to the type II multiverse requires just one additional assumption: Namely that there are fundamental scalars in the universe that have metastable ground states. Well, we now know of at least one candidate that qualifies (the Higgs particle)

I wouldn't call this model "Multiverse", as even the decay to stable vacuum and a giant fireball are occurring in the same space-time. What is "multiversy" about that?

I think that we should decide whether theories are testable or not individually, on a per-theory basis. Not just slap "all Multiverse theories are non-testable" sticker over all of them. Even some theories with multiple disjoint space-times predict "leakage" between them.

 

[Garth]

I think that we should decide whether theories are testable or not individually, on a per-theory basis. Not just slap "all Multiverse theories are non-testable" sticker over all of them. Even some theories with multiple disjoint space-times predict "leakage" between them.

If this "leakage" can be and is detected, or if we find a way of 'seeing' through the 'singularity' at the heart of a black hole or through the 'singularity' at the heart of the Big Bang and see another universe beyond then the situation changes completely. The multiverse becomes part of observed science.

Until then we cannot count as prediction a result which is one such amongst many thrown up by a spectrum of alternative models. A detection of such a result is simply a matter of model selection.

If we have a huge number of models to select from then the detection of one particular value, predicted by one particular model, may be almost inevitable, ("the inflationary paradigm is so flexible that it is immune to experimental and observational tests" )(my #53); it says nothing about the verisimilitude of the cognitive framework that produced those models.

Garth

 

[Dotini]

I stumbled across a paper that might be relevant to your discussion. Hard for me to say if its any good or not.
http://arxiv.org/abs/1501.01919
https://medium.com/the-physics-arxi...n-to-tear-modern-cosmology-apart-d334a7fcfdb6

 

[Haelfix]

Now I wonder why you say that? It sounds like you are already a 'believer' in the inflation paradigm. But science isn't about believing, it's about observing, testing and verifying.

I completely agree. For instance, if you had asked me this question 6 months ago, I would have said that based on the polarization data based on BICEP, that a model like m^2 phi ^2 was looking pretty good, amongst all the competitors (for both theoretical and experimental reasons) and that the multiverse hypothesis was looking perfectly plausible. Based on the data that was received a week ago from the Planck teams, the data has changed and hence my bayesian prior has updated as well. m^2 phi ^2 is now slightly disfavored and I've updated my belief back to small field 'quantum gravity' models that produce inflatons with much smaller values of r. Some of these have multiverses, and some of them its unclear. Consequently my 'belief' in the multiverse hypothesis is a little lower.

This is always slightly personalized, b/c some people know a little more about one theory than others, and so have different priors, but this is roughly the process every physicist undertakes at some time or another.

My point was that this process is completely insensitive to philosophy. I wasn't going to penalize m^2 phi ^2 bc it had a type i multiverse as a byproduct, regardless about whether it fit into someone's idiosyncratic definition of 'science'.

 

[Haelfix]

I wouldn't call this model "Multiverse", as even the decay to stable vacuum and a giant fireball are occurring in the same space-time. What is "multiversy" about that?

Well the assumption is that if you have a type I multiverse already, then you consequently have a very large region of preexisting spacetime. A lot of space, and a lot of time, and a lot of pocket universes with the same general physical law as the one we see's. Now, In one of those isolated bubble universes, if we in addition assume the existence of one of those metastable scalars, all it takes is for a CdL tunneling transition to occur (remember, lots of time, lots of bubbles) and within the order of a few billion years, you very quickly change the bubble with similar laws of physics, to one that has different ones. There are also models where such events take place during the actual inflationary phase where the activation energies are already large. Anyway, that's the rough heurestic sketch, you can find details in many reviews on the subject.

 

[Garth]

I completely agree. For instance, if you had asked me this question 6 months ago, I would have said that based on the polarization data based on BICEP, that a model like m^2 phi ^2 was looking pretty good, amongst all the competitors (for both theoretical and experimental reasons) and that the multiverse hypothesis was looking perfectly plausible. Based on the data that was received a week ago from the Planck teams, the data has changed and hence my bayesian prior has updated as well. m^2 phi ^2 is now slightly disfavored and I've updated my belief back to small field 'quantum gravity' models that produce inflatons with much smaller values of r. Some of these have multiverses, and some of them its unclear. Consequently my 'belief' in the multiverse hypothesis is a little lower.
.

So that is an example of what I said in #53

There is still a possibility that a primordial gravitational wave signal might be hidden in the error bars and it is that which is being investigated now; it will take two years to get the experiment together.

Whatever that balloon experiment finds it will mean that if there is a primordial gravitational wave signal hidden in there it will be far smaller than the one predicted, but hey! we can find another version of inflation that will 'predict' that.

And I remind you of what I said in #58:

Until then we cannot count as prediction a result which is one such amongst many thrown up by a spectrum of alternative models. A detection of such a result is simply a matter of model selection.

If we have a huge number of models to select from then the detection of one particular value, predicted by one particular model, may be almost inevitable, ("the inflationary paradigm is so flexible that it is immune to experimental and observational tests" )(my #53); it says nothing about the verisimilitude of the cognitive framework that produced those models.

Garth

 

[William Jackson]

I'm not a physicist of any description so my concepts are unavoidably vague. But on this subject, isn't that true for everyone? I see a difference between rejecting a concept because it's untestable, and ignoring it because it's untestable. There's as little evidence (zero) to support the universe concept as for the multiverse concept. The question just doesn't seem to apply to practical physics.
Now here's where my Little Golden Books physics background comes in :-) If fundamental particles exist in all possible states, then how can the universe not exist in all combinations of those states? Doesn't a multiverse require fewer assumptions than a universe?

 

[Garth]

I'm not a physicist of any description so my concepts are unavoidably vague. But on this subject, isn't that true for everyone? I see a difference between rejecting a concept because it's untestable, and ignoring it because it's untestable. There's as little evidence (zero) to support the universe concept as for the multiverse concept. The question just doesn't seem to apply to practical physics.
Now here's where my Little Golden Books physics background comes in :) If fundamental particles exist in all possible states, then how can the universe not exist in all combinations of those states? Doesn't a multiverse require fewer assumptions than a universe?

Hi William,
Thank you for your post and welcome!

Nobody is simply rejecting or ignoring the multiverse as an idea because it is untestable.

I actually do think it is untestable for the reasons I have detailed above, the chief one being that there is a whole spectrum of possible alternative versions of the theory of inflation so that if one version fails a test then the next one is rolled into service until that falls short. There is no way to falsify the theory - basically as you can never 'see' these other universes then you can't prove they don't exist.

And the reason why inflation is important is that many versions of the multiverse are the inevitable consequence of many of the inflation theories. But inflation itself is untested in laboratory science.

The reason we should be careful of the mutliverse conjecture is that is if it is untestable then it is unscientific, despite it being predicted by some theory. And despite what other posts have claimed here, you do need to be able to falsify a test in order for it to actually be a test. In other words it is not the way to progress the scientific endeavour. It is not a good way to do science.

Doesn't a multiverse require fewer assumptions than a universe?

That is certainly one argument for the multiverse, however it does require the assumption of the existence of all those other universes, and I for one would argue that a single observable universe as the subject of scientific enquiry is the simpler assumption.

Yes, in order to explain the anthropic coincidences, in order to apply the Copernican revolution on a cosmic scale, then we can certainly conjecture a multiverse.

However, just think, had this idea surfaced a hundred years ago, might researchers have chalked up various mysteries to how things just happen to be in our corner of the multiverse, and not pressed on to discover all the wondrous science of the last century? Now we are at a very exciting time in physics, astrophysics and cosmology. New precision data on the cosmos is being received and yet there is so much we do not know (96% of the mass content of the universe for a start!) If we say these mysteries such as symmetry breaking, which gives particular versions of certain laws and constants, are the result of chance, so the symmetry breaking is "spontaneous" in the jargon, then we are saying that they are how things just happen to be in our corner of the multiverse and look no further for the real reasons that lie deeper.

I hope this helps,
Garth

 

[William Jackson]

Thank you Garth. Very clear. If I can shift to the anthropic view for a moment, I have a question that I've never seen posed or answered. The anthropic arguments seem to center around the idea that the simplest building blocks of our universe have to exist, in order for life to exist. But "life" is as we define it. It seems to me that evolution will occur in any system that provides a self-replicating structure, something to power it, and lots of time. If our universe had different parameters, would it necessarily be less complex? Instead of the particles and forces that we have, on the scale that we have, might there not be something else? Could whatever it is that makes up mass-energy in our universe have another form if the parameters are different?
If the question is unanswerable, then I don't see why the anthropic observation would be a surprise.
I'm not going back to the multiple universe idea, just asking what I'm missing.

 

[DennisN]

Hi William!
I don't know if you directed your question at Garth, but I felt like commenting briefly here on this:

It seems to me that evolution will occur in any system that provides a self-replicating structure, something to power it, and lots of time.

How can we tell? E.g. we currently have got only one celestial body with life in our sample selection.:L It is very hard to draw any conclusions from one sample...:D

 

[Chronos]

There are 'anthropic' coincidences that would make carbon based life impossible. Some would even make stars unable to form.

 

[William Jackson]

There are 'anthropic' coincidences that would make carbon based life impossible. Some would even make stars unable to form.

I meant to imply that in my question. If the parameters make it impossible for stars to form, or even if they make it impossible for atoms to form, those are just the forms that we know from our own universe. If the universe had different parameters, then would it not take forms that are outside of our experience? And might it not be possible for complexity to evolve?
The fact that we can't imagine or know anything about that, it exactly the point. We are a product of our universe the way it is. The anthropic problem is only a problem if you insist that development must take the forms that we're familiar with. There is no anthropic conundrum, only a tautology.
(Phrased as a statement but meant more as a question.)

 

[Garth]

I meant to imply that in my question. If the parameters make it impossible for stars to form, or even if they make it impossible for atoms to form, those are just the forms that we know from our own universe. If the universe had different parameters, then would it not take forms that are outside of our experience? And might it not be possible for complexity to evolve?
The fact that we can't imagine or know anything about that, it exactly the point. We are a product of our universe the way it is. The anthropic problem is only a problem if you insist that development must take the forms that we're familiar with. There is no anthropic conundrum, only a tautology.
(Phrased as a statement but meant more as a question.)

Hi William,

The anthropic coincidences are not just those that allow life on Earth to exist but any forms of exotic exobiological replicating species anywhere in this universe.

The one thing such a species would require is complexity, equal to the complexity of the simplest life forms on Earth. It needs complex molecular structure and the complex ordering of such molecular structure.

That requires a complex chemistry and a favourable ordering of the physical environment: a stable narrow temperature range, lack of severe ionising radiation, and a long, long time for any form of evolution to take place. Many possible universes would lack these things, for example if G were too large then those universes might collapse after only a few years or even after only a few seconds. As Chronos has said above one factor would be the existence of carbon as that alone in this universe is capable of sustaining a biochemistry; silicon is suggested as a possible alternative but it comes nowhere near in terms of complex silicon based chemistry comparable with carbon based organic chemistry.

These requirements for hyper-complexity place a severe constraint on the necessary conditions for life to exist anywhere in an otherwise habitable universe.

Now we can conjecture a different set of physical attributes in some other universe that could also produce a completely different complex life-form somewhere within it; but that life would also have to be hyper-complex and as equally unlikely as life on Earth. Like ours such a universe would be lost amongst the many many universes that would be completely hostile to 'life'.

Even if the conditions are suitable even then, if life formed by chance, it would be incredibly unlikely. Fred Hoyle estimated the spontaneous (stochastic - remember?) appearance of life from an ‘organic soup’ to the likelihood of a whirlwind going through a scrap yard and producing a Jumbo Jet in full working order. He estimated the odds to be somewhere between 10 to the power 140 (10¹⁴⁰) and up to 10^10,000 to one. He then proposed that if the universe were infinite in size and infinitely old (his Continuous Creation model) then no matter how small the odds were it would have happened somewhere i.e. here on Earth or in nearby space (our neighbourhood of the galaxy).

To show how small these odds are take the smaller value, 10¹⁴⁰.

Take the rate of simple biochemical reactions as 10⁵ per sec.
Now there are ~3 x 10⁷ seconds in a year and ~1.4 x 10¹⁰ years in the age of the universe, so each atom could have had ~10²³, (order of magnitude) reactions since the beginning of time!
Now there are about 10⁸⁰ atomic particles in the entire observable universe. Let each one be an atom undergoing random chemical/biological reactions.
There would have been a maximum of 10²³ x 10⁸⁰ =10¹⁰³ reactions since the universe began, a short fall of a factor of 10³⁷ before one "first self-replicating organism" arrived. And this is very much a lower bound, the real short fall is much larger.

Therefore on those odds we would have to wait 10³⁷ or 10,000,000,000,000,000,000,000,000,000,000,000,000 times the present age of the universe until just one such organism arrived anywhere!

Now, there might be 10³⁷ other universes or 'patches' of this universe 'beyond our ken' in which the unlikely chemical reaction took place.

So one way to explain this is to say 'The multiverse did it'; no matter how improbable life may be it must happen somewhere in one of those universes/patches, and we are in this universe because we can be in no other.

But on the other hand, perhaps there are other ways rather than by pure chance of understanding how the first self-replicating organism appeared. For example, biologists are looking into there being a first self-replicating molecule, an evolving chemistry, which could develop by natural processes into a first replicating organism, such as a bacteria, in a relatively short period of time.

After all on Earth it seemed to have happened rather quickly, within a few hundred million years of the Earth becoming 'habitable'.

Now my point is this:

If we simply say 'the multiverse did it' then we would short-circuit that scientific investigation into the origin of life and hence get nowhere.

I use this as one example why I think the multiverse is not a good way to do science.

Garth

 

[PeterDonis]

It is very hard to draw any conclusions from one sample...:D

Everyone generalizes from one example. At least, I do... :w

 

[William Jackson]

I use this as one example why I think the multiverse is not a good way to do science.

Garth

Agreed! I like to point out to people that science has made more progress in the last 500 years than philosophy has.
Thank you for taking the time to offer such a thorough reply. You've answered my questions and expanded my thinking a bit.

 

[PeterDonis]

This thread has run its course, so it is now closed.