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Searching for Life in the Multiverse

Artist concept of the multiverse. Credit: Florida State University

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


Nancy Atkinson is currently Universe Today's Contributing Editor. Previously she served as UT's Senior Editor and lead writer, and has worked with Astronomy Cast and 365 Days of Astronomy. Nancy is also a NASA/JPL Solar System Ambassador.

Comments on this entry are closed.

  • Lawrence B. Crowell January 19, 2010, 8:13 PM

    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.


  • Aodhhan January 20, 2010, 4:16 AM

    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.

  • Lawrence B. Crowell January 20, 2010, 4:52 AM

    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,


  • Olaf January 20, 2010, 10:45 AM

    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.

  • Lawrence B. Crowell January 20, 2010, 4:46 PM

    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.


  • Torbjorn Larsson OM January 22, 2010, 3:58 PM

    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.

  • Torbjorn Larsson OM January 22, 2010, 4:20 PM

    @ 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!

  • Lawrence B. Crowell January 23, 2010, 5:28 AM

    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.