Multiverse Theory

Searching for Life in the Multiverse

Article written: 18 Jan , 2010
Updated: 24 Dec , 2015

Other intelligent and technologically capable alien civilizations may exist in our Universe, but the problems with finding and communicating with them is that they are simply too far away for any meaningful two-way conversations. But what about the prospect of finding if life exists in other universes outside of our own?

Theoretical physics has brought us the notion that our single universe is not necessarily all there is. The “multiverse” idea is a hypothetical mega-universe full of numerous smaller universes, including our own.

In this month’s Scientific American, Alejandro Jenkins from Florida State University and Gilad Perez, a theorist at the Weizmann Institute of Science in Israel, discuss how multiple other universes—each with its own laws of physics—may have emerged from the same primordial vacuum that gave rise to ours. Assuming they exist, many of those universes may contain intricate structures and perhaps even some forms of life. But the latest theoretical research suggests that our own universe may not be as “finely tuned” for the emergence of life as previously thought.

Jenkns and Perez write about a provocative hypothesis known as the anthropic principle, which states that the existence of intelligent life (capable of studying physical processes) imposes constraints on the possible form of the laws of physics.

Alejandro Jenkins. Credit: Florida State University

“Our lives here on Earth — in fact, everything we see and know about the universe around us — depend on a precise set of conditions that makes us possible,” Jenkins said. “For example, if the fundamental forces that shape matter in our universe were altered even slightly, it’s conceivable that atoms never would have formed, or that the element carbon, which is considered a basic building block of life as we know it, wouldn’t exist. So how is it that such a perfect balance exists? Some would attribute it to God, but of course, that is outside the realm of physics.”

The theory of “cosmic inflation,” which was developed in the 1980s in order to solve certain puzzles about the structure of our universe, predicts that ours is just one of countless universes to emerge from the same primordial vacuum. We have no way of seeing those other universes, although many of the other predictions of cosmic inflation have recently been corroborated by astrophysical measurements.

Given some of science’s current ideas about high-energy physics, it is plausible that those other universes might each have different physical interactions. So perhaps it’s no mystery that we would happen to occupy the rare universe in which conditions are just right to make life possible. This is analogous to how, out of the many planets in our universe, we occupy the rare one where conditions are right for organic evolution.

“What theorists like Dr. Perez and I do is tweak the calculations of the fundamental forces in order to predict the resulting effects on possible, alternative universes,” Jenkins said. “Some of these results are easy to predict; for example, if there was no electromagnetic force, there would be no atoms and no chemical bonds. And without gravity, matter wouldn’t coalesce into planets, stars and galaxies.

“What is surprising about our results is that we found conditions that, while very different from those of our own universe, nevertheless might allow — again, at least hypothetically — for the existence of life. (What that life would look like is another story entirely.) This actually brings into question the usefulness of the anthropic principle when applied to particle physics, and might force us to think more carefully about what the multiverse would actually contain.”

A brief overview of the article is available for free on Scientific American’s website.

Source: Florida State University


28 Responses

  1. Jon Hanford says

    “What theorists like Dr. Perez and I do is tweak the calculations of the fundamental forces in order to predict the resulting effects on possible, alternative universes”.

    How would you like to have that for a job description? 🙂

    Seriously, the authors lay out their case in a non-technical, accessible manner. They also touched on a number of cosmological questions familiar to regular readers here at UT. It’s worth tracking down the full article at a library or school (or borrow a friends copy).

  2. OJB42 says

    Very interesting. The apparent fine tuning of the universe has been something I’ve found very puzzling and have recently blogged about. I find the idea that our universe may not be as finely tuned as we thought intriguing. This finding seems to have philosophical and theological as well as cosmological significance!

  3. Torbjorn Larsson OM says

    Well, I’m glad that this type of work explodes the myth of fine-tuning. The adherents never show any numbers behind their claims, it seems to be a folk myth.

    While those who look into it (Vic Stenger comes to mind) does so. The smoking gun was that paper a few years back there they turned the weak force off all together (IIRC) and still got mundane galaxies.

    OTOH the weak anthropic principle is really robust and predictive, at least in it’s more general environmental form. (Say, as maximizing dust production, and so planets of any kind. Which sounds what these author’s may have been looking at.) I thank Nancy for the article and Jon for the encouragement to find it worthwhile hunting the work down!

  4. Paul Eaton-Jones says

    I feel that any version of the Anthropic Principle smacks of some underlying religious element. The initial conditions [electric charge ratios, mass ratios etc. etc] didn’t happen as they did in order to eventually produce life. That hints at a grand design. In some universe the ratios were different and life either didn’t arise or is totally differently.
    It always gets turned around so that the fine tuning ‘was done’ in order that the universe would end up with us/intelligent life to observe and measure it. Why can’t people accept that we’re here and the universe is here? The universe existed before us/life and will be here long after life has had its day in the light. Anything else is mere hubris.

  5. Lawrence B. Crowell says

    The other problem is the anthropic principle (AP). There are forms of this, in particular the strong and weak forms. The weak form is a sounding board of sorts. The 19th century hypothesis that the sun produced energy by gravitational collapsing failed a weak AP argument, for this could only work a few 100 thousand years and evolution indicated at the time a greater than 100 million year time line. So this was effectively an AP argument that physics had to be of a different form in order for life and configurations on Earth to exist. So the weak AP says, “Nature must be of a certain form in order for life to exist as well as other particular configurations of things we observe. The AP in this form does not explain much, but it is something which acts as a sanity test. There is the strong AP as well, which says that the universe which exists is that which brings about intelligent life. In this form the AP acts as the “explanens” for the structure of reality. In effect this is a tautology of sorts, which can’t really serve as a foundational theory. The authors are advancing ideas of life in other cosmologies based on a version of the strong AP.

    The big issue is the cosmological constant, which is a Ricci curvature terms associated with quantum vacuum energy. Quantum physics predicts a very large value, while observations indicate a very small value, and which compose what is called dark energy. Now we might address this issue by considering our cosmology (universe) as a four dimensional spacetime embedded in a 26 dimensional bosonic spacetime or equivalently a 10 dimensional super-spacetime. There is a relationship between them which is subtle. There then exist on a scale larger than the string length regions of D-brane compactification which define 4 dimensional spacetimes. These are different universes. Now the fields so configured emerge from quantum fluctuations with a mass-energy density L_p^{-4} ~ 10^{122} Gev^4. This is huge. However, the process involves something called holography, which in a quantum perspective is a quantum fluctuation which changes the phase of the system. The Euclideanized time, t, of the fluctuation is equivalent to an effective temperature T = hbar/kt (hbar = Planck quantum unit of action, k = Boltzmann constant) which can adjust the thermodynamic phase of the system. The phase here is between a heavy fermion and light fermions in an anti-ferromagnetic state. This renormalizes the cosmological constant to a much smaller value. So as I work through the AdS correspondence with Dirac operators etc, I think the problem can be addressed without appeal to a strong AP.

    We can’t probe these other universes because even though there is a quantum tunneling process with holography mapping dual forms of fields, if we could probe these other cosmologies it would violate the “no cloning” theorem of quantum mechanics. In other words we would be able to duplicate quantum fields by carrying them across certain horizons in ways which also violate some causality principles.


  6. Lawrence B. Crowell says

    I copid this in from MS Word and did not capture the first paragraph!


    I read their article and found myself asking an important question, “Is this science?” There are two main problems with this. The first is we are not likely to ever test the hypothesis there exists life on other universes in the multiverse. BTW, I really dislike the term multiverse, for I prefer to think of there being a universe with multiple spacetime cosmologies. Yet I will never change that term — as much as I dislike it. In fact the big trick is to detect the existence of other cosmologies. This might be possible if we can detect quantum fluctuations of spacetime which have certain characteristics. This would support the idea of the multiverse, though I doubt we can directly probe other cosmologies. In other words I doubt we can send probes into them and get pictures of other cosmic galaxies or whatever exists there. There are certain issues which I think preclude this, which I allude to below.

  7. neoguru says

    Is it me or is this Santa Claus science? I mean the Easter Bunny and Tooth Fairy are fun also, but their existence is asking a bit much. Alternate universes? Isn’t this simply investigating a fantasy where there’s no evidence of such a thing? Worse, by its very nature, no evidence for its existence can EVER be found. It seems downright silly to me. I’m at least glad that others share my opinion.

  8. Lawrence B. Crowell says

    There are good reasons to think there are other spacetime cosmologies. It comes down to counting degrees of freedom in physics. To make physics work we need to go to these larger dimensions, but this results in many more degrees of freedom than what can exist in our observable universe. Hence these degrees of freedom exist “elsewhere,” or in other universes.

    There are potential tests for this. Other universes (or spacetime cosmologies as I prefer to think of them) are coupled to our observable universe by quantum fluctuations which will have certain signatures. We can detect that — at least in principle. We then could infer the existence of these other universes based on evidence which is correlated with their prediction.

    You might want to check out Max Tegmark. He puts this multiverse idea on steroids, in ways which I think go far beyond any empirical tests we could perform, at least now or the foreseeable future. He proposes that all mathematical structures which can exist, and this is infinite, enter into other universes which may be profoundly different from our observable universe. So their might be universes with spaces that have quartic Plucker coordinates, or universes based on mathematics we don’t even know about.


  9. Aodhhan says

    Science101: Science is doing something, when we don’t know what we are doing. So, yes it is science.

    If we stopped working on things before we ever thought they were possible… there would be many things never invented or researched.

    Yeesh, just read the life of Einstein, and look at at least 3 things many experts believed he was nuts about. Like maybe, gravity affecting light “Insert here”.

    Actually…what a great job. Turning off elementary forces and then attempting to determine what the universe would be like… a helluva challenge actually. Unless you turn off the strong force… then it would be pretty simple. Just a bunch of radiation. However, the weak-force which someone brought up; is full of challenges.

    On dogma: It is strange, how the universe (or nothing for that matter) could somehow create a spontaneous all-knowing, all-powerful diety, yet couldn’t create man after billions of years. I’m still waiting for this answer… if anybody has one, I have continuing questions as well.

    Multi-verses is plausible. Since in the known universe there seems to be more than one of everything.

    It comes down to counting degrees of freedom in physics?? What does this mean? I asked 2 other physicists, and they are as clueless as I am. Although one had a pretty funny thought.

  10. Joseph says

    I think that if the multiverse theory is real, that not only are there different universes other than our own, but an infinite amount and all in other dimensional planes. You can’t rule out that just because these universes would have different laws of physics, that none of them would hold life like ours does. If there’s an infinite amount of universes, there is a possibility that there is another universe out there that is basically exactly replicate to our own, except maybe history is a little different, because you know how they say, kill a bug in the past, drastically alter the future? Well, if you go back in time and something changes and then are brought back to present time, everything is different, well, where the hell did your reality go? You have memories of it, so it must have existed, right? Well what if every millisecond, or even every yoctosecond ( for those of you who don’t know what that is.), our universe gets split up into other universes based on the choices we make everyday.

  11. Member
    Aqua says

    Apparently there are at least as many universes as there are opinions?

  12. Joseph says

    And I won’t post my personal theories if other people don’t.

  13. Paul Eaton-Jones says

    If one subscribes to the ‘Many Worlds Hypothesis’ of quantum theory then a multiverse idea isn’t too far out and is theoretically possible/probably.

  14. Member
    Aqua says

    Are there beings from alternate realities/universes among us? Have you ever had an otherworldly ‘visitation’? or done any time travel?

    I have. Yet I have no scientific proof that would pass even the most casual analysis. There are aspects of reality that are only cognizant to those who attempt them. And there are those amongst us who would vehemently deny even the possibility.

    NO FEAR!

  15. Dark Gnat says

    In these multiverses, maybe Santa, the Easter Bunny, and Frodo truely exist.

    Honestly, unless something could be detected or tested, then this is all science fiction, or a fun mind excercise.

  16. Lawrence B. Crowell says

    Depending upon who you talk to there are differences between the many worlds interpretation (MWI) of quantum mechanics and the multiverse. The MWI is an interpretation of quantum measurement or the apparent nonunitary process of quantum state reduction. The multiverse is a system of spacetime cosmologies connected in a grand superspace. Now these have subtle quantum entanglements with each other, which means this system is related MWI. However, there are holographic considerations at work, which means each of these cosmologies exists “on its own,” so to speak.

    The entanglements these other cosmologies have with our observable universe involves the quantum wave mechanics of the superspace, which is an E8 system. This wave mechanics is a type of soliton associated with the anti-de Sitter configuration of each cosmology, which is dependent on the value of the cosmological constant or “Lambda.” So in detecting these fluctuations some estimate is possible, if we become very good at such measurements, of the internal configurations of different cosmologies. There are 453,060 irreducible representations of E8, which corresponds roughly to the low energy make up of fields in these universes. There is then a range of gauge hierarchies with each of these, leading to 10^{500} possible cosmology types. So at best we might just get some hints at a small sampling over these.

    In spite of the apparent abstractions and remoteness of this, it should be realized that just 100 years ago it would have seemed impossible that people would be concerned over the operations of robots and spacecraft around and on the surface of Mars, or orbiting Saturn.


  17. Aodhhan says

    You must have your own nonphysics dictionary, perhaps just another point where you use the words but lose the cephalic energy to allow the brain to perfuse, or just a twat?

    Quantum Entaglement does not simply mean systems are related. By no means would there be any “Subtle” relationship within the definition. It is definitely an all-or-nothing relationship.
    Holographic Considerations typically relates to information for creating a whole (system for instance) is stored in each of its parts.
    …which it doesn’t in this case.
    Or in Physics, it refers to the holographic principle. Which you definitely can’t fit here the way you use it; although it could fit in with the structure of the topic. However, I’ll let you look it up.

    …and I’m the one who knows nothing? LOL

  18. Lawrence B. Crowell says

    An pure state composed of an entangled system with two parts has the entropy

    S = S(A) + S(B) – S(A|B).

    It can shown that since the eigenvalues of the two subsystems are equal that S(A) = S(B) and that S = 0. So the entropy, as given by the von Neumann form is S = 0. So the joint entropy cancels out the S(A) + S(B). This can be extended to many components of an entangled system. This is the case with multiverse physics. The entire multiverse is likely a pure state in the “superspace,” and so the local entropies we observe, say as with the S(A) above, is due to the fact the other entropies of other cosmologies and their joint entropies are not available. The occurrence of event horizons prevents such EPR experiments. So while the information in our universe is through boundaries, eg AdS boundaries and CFT, holographic “copies” of all information, we lack the “key” required to reconstruct this.

    Quantum fluctuations in our spacetime metric will permit some small measure of this joint entropy. So in principle the physical predictions of a multiverse could be detected to give weight to the hypothesis there exist these “other universes.”


  19. Joseph says

    Would I be considered ignorant to hypothesize that maybe black holes could be connected to other universes? Just another theory to add to what might be on the other side of a black hole, if anything at all.

  20. Dave Finton says

    @Joseph: It is myunderstanding that black holes exist in an infinitely deep gravity well in space time, so there effectively is no other end to connect to another Universe. It’s akin to trying to drive an infinite amount of distance in your car. No matter how far you go, there’s infinitely more distance to cover.

  21. Lawrence B. Crowell says

    Black holes have quite a bit to do with this. Various cosmologies are connected to each other through polarized vacuum structure where huge Weyl curvatures exist — such as near the singularity of a black hole. A quantum fluctuation in the metric can pinch off a portion of vacuum energy which then quantum tunnels as an instanton through a potential field in superspace and into a nascent cosmology.

    The interior of a black hole is a trapped region where geodesic are confined to reach the singularity. The curvature does become enormous, but cuts off at around 1/L_p^2 = c^3/(G-hbar) ~ 10^{67}cm^{-2}, This is also the magnitude of the Weyl curvature, that responsive for tidal forces, which squeezes the vacuum.


  22. Aodhhan says

    I don’t think you’re ever ignorant to hypothesize anything as long as you give it honest thought and investigate. Researching and proving a hypothesis is science!

    Nobody knows what happens to matter once it goes beyond the event horizon. Even mathematics could break down. Which in science breeds many theories. The one who is correct, becomes immortilized. Which unfortunately breeds other things 😉

    One thing is for sure… black holes toss out a lot of x-rays, and can be very violent. So something crazy is going on. Perhaps a gateway for gravity to find its way through the many theorized dimensions of space? Your guess is as good as mine.

  23. Lawrence B. Crowell says

    For a nonrotating black hole the important metric element is 1 – 2GM/rc^2. For the radius large this term is 1 minus some small number. This is for standard gravity fields. Yet for the radial direction approaching the r –> 2GM/c^2 the metric term approaches zero. At r = 2GM/c^2 you are at the event horizon of a black hole. This is a congruence of null geodesics which demark the “point of no return.” Anything in the region r 2GM/c^2. There is no causal connected set from the r < 2GM/c^2 to the outside. So the X-rays and other radiation we observe are due to material effects of hot plasmas in accretion disks in this outer region. The black hole is inferred because of the energetically high level of such radiation, and that the horizon is not a solid surface with a signature of what might be called a “splash.” The surface of a neutron star has the signature of a solid impact surface, but the black hole does not.

    What is in the interior can well enough be computed without any difficulty in general relativity, at least up to the singularity — in the nonrotating BH case is r = 0. To work in matters of how this connects with other universes or cosmologies gets one into the problem of quantum black holes. In particular the singularity at the black hole core, and the quantum fields on the stretched horizon (a holographic aspect of BHs), have a duality to each other. For a tiny quantum black hole there are quantum superpositions between these two representations of holographically equivalent fields. So quantum fluctuations associated with the large Weyl curvature term in a larger superspace theory can entangle the quantum fields of our universe with a nascent cosmology. In effect a bit of vacuum energy in our universe quantum tunnels into another spacetime cosmology,


  24. Olaf says

    Aodhhan Says:
    “Nobody knows what happens to matter once it goes beyond the event horizon. Even mathematics could break down.”

    “One thing is for sure… black holes toss out a lot of x-rays, and can be very violent. So something crazy is going on.”

    Aodhhan, time for you to start reading some astronomy papers, and get your information updated.

    Only at the singularity level there is a big unknown since current mathematics can’t handle it very well. Beyond the event horizon they can calculate pretty precise. Like that you would not even know that you crossed the event horizon assuming you survived spagettification.

    The sources of X-rays from a black hole are pretty good understood. No requirement for some Star Gate portal or godlike mystery. You should learn something about the magnetic dynamics of a black hole. Big part of the mass even never gets into the black hole.

    If there is a multiverse then it is all around us and most probably follow the gravity, any gravity ne black hole required, the gravity of as single atom in effect vacuum is one direction.

    As far as understand the multi-verse correctly, it is not those 10 dimension where 6 curled up because that is still part of the one universe. It is the 11th dimension that indicates the multiverse. Here we are at the branes.

  25. Lawrence B. Crowell says

    There are a range of mathematical structures here with 10 and 11 dimensions. To make things a bit weirder there is also a 26 dimensional Lorentzian space, which corresponds to the 10 dimensional superspace, and the 11 dimensional space corresponds to the 27 dimensional exceptional Jordan space. Upon compactification, or what is sometimes called the infinite momentum frame, one dimension is reduced. This is the domain where D-branes in 11( or equivalently 27) dimensions are wrapped into various configurations. In effect the 10 (or equivalently 26) dimensional Lorentzian spacetime is a “universe,” and the one compactified dimension can be a parameter for the occurrence of different cosmologies.

    All of this sounds very mysterious, but in a funny way D-brane physics is a lot like Gauss’ law and Stokes law in basic electromagnetism — just in more generalized mathematical language.

    The black hole, as Olaf states does not directly produce X-rays, but rather the dynamics of material in its close gravitational grip generate this radiation. Nothing emerges from the event horizon of the black hole. The only exception is Hawking radiation, and for stellar sized black holes this is negligible.


  26. Torbjorn Larsson OM says

    Okay, late coming back, but I had to read the article. And wow, it doesn’t disappoint.

    First, it was Perez (et al) that had worked with non-weak force universes. Maybe I should have recognized the name, but in fact I didn’t. These guys have continued with other interactions à la Stenger, and showed some more possibilities.

    Second, they not only discuss multiverses as they are mundane, but they actually claim outright that they must be studied. “The real challenge, then, may be to explain why we do not live in a weakless universe. Eventually only a deeper knowledge of how
    universes are born can answer such questions. In particular, we may discover physical principles
    of a more fundamental level that imply that nature prefers certain sets of laws over others.

    We may never find any direct evidence of the existence of other universes, and we certainly
    will never get to visit one. But we may need to learn more about them if we want to understand
    what is our true place in the multiverse—or whatever it is that is out there.”

    Third, they discuss the anthropic principle. I don’t agree with them that finding other potentially habitable universes like the weakless is a problem for it. They are still islands in a larger sea, and an environmental form of the principle still applies.

  27. Torbjorn Larsson OM says

    @ Paul:

    I feel that any version of the Anthropic Principle smacks of some underlying religious element. The initial conditions [electric charge ratios, mass ratios etc. etc] didn’t happen as they did in order to eventually produce life.

    This is exactly the kind of idea these hypotheses argues against.

    One must understand that the religious Anthropic Argument (AA) is devised to “explain” the religious idea of confusing a priori hypotheses (teleological ideas) with a posteriori outcomes (causality of processes).

    Folk “fine-tuning” (balanced outcome of parameters) is, as opposed to physics fine-tuning (balanced parameters), an expression of, nay method for, exactly that.

    The Anthropic Principle (AP) on the other hand is simply an expression for some form of non-uniform statistical distribution over parameters, which is based on causality and a posteriori outcomes. All the weak AP claims is that there is such a distribution. And theories like effective field theories seems to agree, at least as regards having distributions as such.

    @ LBC:

    we are not likely to ever test the hypothesis there exists life on other universes in the multiverse. […] The other problem is the anthropic principle (AP).

    The weak AP is testable. The article that the post describes contains a number of such tests. (Those are the “islands” of habitability I described in my previous comment, predicted by the hypotheses of a non-uniform distribution.)

    Weinberg was the first to successfully falsifiably test the AP, see the referenced article. And lo, it passed the test!

  28. Lawrence B. Crowell says

    The weak AP is not exactly testable, but it is a statement which can be used. It amounts to saying, “The universe must be structured to permit life to exist.” It provides no method for finding that structure. This was invoked in a way to search for a long lasting power source for the sun. The strong AP says, “The only type of universe which may exist is one which brings about intelligent life.” This is more tautological.

    I think I encountered a paper back in 2007-8 by Perez on a weakless cosmology. The question was whether life could exist there was raised. A universe without weak decay would have a different “metallicity,” as astrophysicists call it. The decay channels by beta decay would not be available, so the daughter products we observe from weak decay would not be as prevalent. There are also questions about the energy source of the Earth and other planetary centers. The sort of standard theory is this is due to weak decay, though some recent ideas about uranium nuclear reactions have come up.

    The Pati-Salam theory of weak interactions is an SU(2)xSU(2) ~ SO(4) theory. One of the SU(2) breaks by the Higgs mechanism so its Cartan center gives a U(1) group and the mixing of the hypercharge with the weak central charge (weak angle mixing etc) results in the standard electroweak theory. The SO(4) at high energy is similar to the SO(3,1) group for gravity, under a Wick rotation to hyperbolicity. Both of these can embed in a higher SO(8) group, or SO(7,1) group. So with this standard concept of cosmologies, say where the SO(8) embeds in the E_8 or SO(32) of superstring theory, it seems that these degrees of freedom will exist in some form, where in our cosmos we observe them in a low energy limit as weak interactions. The CP violations in weak interactions might be connected with the so called arrow of time in gravity. We might writes as CPT = 1, and since CP is violated in SO(4), this is mirrored in some ways by a T violation in SO(3,1), setting up the arrow of time, so that upon unification, say in SO(8), this violation or symmetry breaking is removed. There are other questions with axions and the strong interactions as well.

    We might become capable of detecting signatures in quantum fluctuations in the metric, and determining if these are subtle quantum overlaps with other cosmologies. We might stretch this further, and this is a big stretch, and figure out how certain signatures correspond to the gauge structure into these other cosmologies. We will be doing damned good if we can end up doing that. As for finding life, we are probably forbidden to access direct information in these other universes, so this will probably remain a bit speculative.


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