The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos

by Brian Greene

Sometimes it refers only to those parts of everything that someone such as you or I could, in principle, have access to.

Interesting. Universe defined as what a human observer directly beholds. This would allow for that reflexive-expansive definition, where there can never be a "super" natural, because the moment we observe it we claim superiority over it, making it "natural." It's the "stacked deck" defense of naturalism.

We can predict the odds of attaining one outcome, we can predict the odds of another, but we generally can’t predict which will actually happen.

This is a form of faith-based science. On the one hand, it is giving over to the fact that hard core objective empiricism is untenable for a human finite mind. On the other, it makes the human observer the final arbiter of reality and allows for even the most ridiculous theories to be entertained on the grounds that literally anything is possible.

The mathematics underlying quantum mechanics—or at least, one perspective on the math—suggests that all possible outcomes happen, each inhabiting its own separate universe. If a quantum calculation predicts that a particle might be here, or it might be there, then in one universe it is here, and in another it is there.

But why is this the mathematically necessary answer? It seems to be rather a philosophical adaption that results in a preferred conclusion. Just because the math showed all things are possible, why does it follow that all things must be actual?

We’ll see that if space extends infinitely far—a proposition that is consistent with all observations and that is part of the cosmological model favored by many physicists and astronomers—then there must be realms out there (likely way out there) where copies of you and me and everything else are enjoying alternate versions of the reality we experience here.

So if there is enough space and I look far enough I'll find myself? How is that not pure assertion via imagination?

No experiment or observation has established that any version of the idea is realized in nature.

That said, I find it both curious and compelling that numerous developments in physics, if followed sufficiently far, bump into some variation on the parallel-universe theme.

Is this because that is where the evidence leads our because a common philosophical starting point predestines the result?

Rather, all of the parallel-universe proposals that we will take seriously emerge unbidden from the mathematics of theories developed to explain conventional data and observations.

Unbidden? Perhaps. But how much of this is a lack of philosophical self examination? If the underlying, unadmitted anti theistic premise were to be intentionally examined, then perhaps the point of view would change.

universes. I want you to get a sense of how modern scientific investigations—not untethered fantasies like the catoptric musings of my boyhood—naturally suggest this astounding possibility.

But if we're only to accept hard evidence and there is none, how is this not also "untethered"?

These copies would inhabit realms so distant that light traveling since the big bang wouldn’t have had time to cross the spatial expanse that separates us.

But if light from the Big Bang hasn't reached there yet, how is any of this possible? How do their crops grow? Are we talking multiple bangs? So far this sounds like one bang, one universe.

The world’s most famous physicist had been persuaded to change his mind about one of the world’s most challenging mysteries. While still largely unknown to the general public, Lemaître would come to be known among scientists as the father of the big bang.

The Big Bang was pioneered by a Christian thinker.

Such uniformity proves crucial to using the equations of general relativity to study the entire universe. To see why, think of a beautiful, uniform, smooth beach and imagine that I’ve asked you to describe its small-scale properties—the properties, that is, of each and every grain of sand. You’re stymied—the task is just too big. But if I ask you to describe only the overall features of the beach (such as the average weight of sand per cubic meter, the average reflectivity of the beach’s surface per square meter, and so on), the task becomes eminently doable. And what makes it doable is the beach’s uniformity. Measure the average sand weight, temperature, and reflectivity over here and you’re done. Doing the same measurements over there will give essentially identical answers. Likewise with a uniform universe. It would be a hopeless task to describe every planet, star, and galaxy. But describing the average properties of a uniform cosmos is monumentally easier—and, with the advent of general relativity, achievable.

So it's necessary because it's easy?

when it comes to space itself, there isn’t an outside environment to contain it);

Doesn't multiversal space, if it exists, prove this wrong? Even in our attempts to conceptually go outside ourselves we still are bound by our finitude. We cannot conceive of one space that isn't contained and bounded by another.

They show that the curvature of space reduces to a single observational quantity: the density of matter (more precisely, the density of matter and energy) in space.

But if there is at least one major type of undetectable energy (dark energy) how can we ever be certain we understand what the actual proportions are?

curve back on itself, yielding the spherical shape.

If space is a sphere, could this be the way to the Big Crunch? Once the matter pushes to the far side of the sphere it begins to collapse down on itself?

Because of its important cosmological consequences, astronomers have been trying for decades to measure the average density of matter in the universe. Their method is straightforward. With powerful telescopes, they carefully observe large volumes of space and add up the masses of the stars they can see as well as the mass of other material whose presence they can infer by studying stellar and galactic motion.

This would presume we know roughly the size of the whole universe and that the observable portions are either the whole or reasonable representatives of it. I'm not convinced we aren't like Columbus estimating the size of Asia relative to the earth. It makes plenty of sense based on the data we have, but fails because of the data we're missing.

astronomers realized that they had been leaving out an essential component of the tally: a diffuse energy that appears to be spread uniformly throughout space.

Bingo. What makes us think dark energy is all these is that is left to find?

For some cosmological questions, such as the age of the universe, the distinction between the two possibilities plays no role.

How so? Can something be spatially infinite and temporally finite? Can we rationally posit a beginning with no end?

And for either a finite or an infinite universe, state-of-the-art analyses now peg that moment at about 13.7 billion years ago.

But doesn't the inflationary universe argue that our rate of expansion has varied widely? Why might it not continue to do so?

If space is truly infinite in size, then it always has been and always will be.

I understand the Big Bang created measurable time and space. If so, then the space referenced here is clearly not the same as the space which the universe occupies because that space has a beginning and is constantly expanding outward. This infinite space, then, must be the space which our space occupies, which he previously said was not necessary or even conceivable. In short, this is the Unspaced Space! The space that is not space! In short: unexamined gobbledygook.

Although observations leave the finite-versus-infinite issue undecided, I’ve found that when pressed, physicists and cosmologists tend to favor the proposition that the universe is infinite. Partly, I think this view is rooted in the historical happenstance that for many decades researchers paid little heed to the finite video-game shape, mostly because it is more mathematically complex to analyze. Perhaps the view also reflects a common misconception that the difference between an infinite and a huge-but-finite universe is a cosmological distinction that’s only of academic interest. After all, if space is so large that you will only ever have access to a small portion of its entirety, should you care whether it extends for a finite or for an infinite distance beyond what you can see?

I wonder if this is the reason or of it is because they are afraid of the larger implications of truly finite space. Specifically, finite space would require a cause and any cause must be sufficient to explain all of the universe (i.e. God). Ironically, this question bears very heavily on the practical moral and spiritual implications of daily life. In that sense, it is far more applicable than to real people than most of what I'm reading here.

You should. The issue of whether space is finite or infinite has a profound impact on the very nature of reality.

Good!

With minimal effort, we’ll find ourselves inhabiting one of an infinite collection of parallel worlds.

Which predisposes us to accept the infinite in advance of the evidence....

In an infinite universe, most regions lie beyond our ability to see, even using the most powerful telescopes possible. Although light travels enormously quickly, if an object is sufficiently distant, then the light it emits—even light that may have been emitted shortly after the big bang—will simply not have had sufficient time to reach us.

How dues this make any sense? If the universe originated in the Big Bang, even if it is thereafter infinite, we occupy the same relative space to the rest of the universe that we would in a finite universe. The infinite aspect really plays no role in that whatsoever. If you're talking about other light from other Bangs, that's a different question, but that isn't here this is presented.

Using the reasoning rehearsed with Imelda and Randy, this means that conditions in the infinity of far-flung patches—in regions of space like the one we inhabit but distributed through a limitless cosmos—necessarily repeat.

This is the old, tired monkey on the typewriter argument. If the chances of any one patch coming into existence are impossible, then infinite time-space simply repeats an infinite impossibility.

You might counter that the inability to distinguish between tiny spatial separations or differences in speed reflects nothing more than a technological limitation. With progress, the precision of equipment always improves, so the number of discernibly distinct positions and speeds available to a well-funded fly will also always increase. Here I must invoke some basic quantum theory. According to quantum mechanics, there’s a precise sense in which there is a fundamental limit on how accurate particular measurements can be, and this limit can’t ever be surpassed, regardless of technological progress—ever. The limit arises from a central feature of quantum mechanics, the uncertainty principle.

Cited here as an article of faith, not empiric science.

In interpreting the implications of this statement, I should declare my bias. I believe that a physical system is completely determined by the arrangement of its particles. Tell me how the particles making up the earth, the sun, the galaxy, and everything else are arranged, and you’ve fully articulated reality. This reductionist view is common among physicists, but there are certainly people who think otherwise. Especially when it comes to life, some believe that an essential nonphysical aspect (spirit, soul, life force, chi, and so on) is required to animate the physical. Although I remain open to this possibility, I’ve never encountered any evidence to support it. The position that makes the most sense to me is that one’s physical and mental characteristics are nothing but a manifestation of how the particles in one’s body are arranged. Specify the particle arrangement and you’ve specified everything.15

A wholly faith-based statement not supported by his actual observations in absence of bias thus far. Thus it becomes the the speculative/imaginary foundation necessary to accept what follows. He has passed the Pale of Possibility.

Over time, the size of the cosmic patches laid out in Figure 2.1b will increase; with more time, light can travel farther and so each of the cosmic horizons will grow larger. Ultimately, the cosmic horizons will overlap. And when they do, the regions can no longer be considered as separate and isolated; the parallel universes will no longer be parallel—they will have merged. Nevertheless, the result we’ve found will continue to hold. Just lay out a new grid of cosmic patches with patch size set by the distance light can have traveled since the big bang through this later moment. The patches will be bigger, so to fill out a pattern like that in Figure 2.1b their centers will need to be farther apart, but with infinite space at our disposal, there’s ample room to accommodate this adjustment.16

This completely contradicts the basic premise of a single Bang producing a coherent universe. It postulates a completely unsupported, infinite multispace that he's confusing with universal space. Further, it never answers the question of why any space exists at all. Infinite space simply make the impossible infinitely impossible.

Might the assumption that the entire cosmos is inhabited by particles be wrong? Perhaps beyond our cosmic horizon is a vast realm containing nothing but empty space. It’s possible, but the theoretical contortions required to accommodate such a picture render it thoroughly unconvincing. The most refined cosmological theories, to be encountered shortly, don’t lead us anywhere near this possibility. Might the very laws of physics change beyond our cosmic horizon, corrupting our ability to perform any reliable theoretical analyses of those distant realms? Again, it’s possible. But as we will see in the next chapter, recent developments yield a compelling argument that although the laws can vary, that variation doesn’t invalidate our conclusions regarding the Quilted Multiverse. Might the universe’s spatial expanse be finite? Sure. Definitely possible. If space were finite yet large enough, there could still be some interesting patches way out there. But a smallish finite universe could easily fail to have adequate space to accommodate substantial numbers of distinct patches, let alone any that are duplicates of our own. A finite universe poses the most convincing way to upend the Quilted Multiverse.

None of these hit on the most fundamental and most seriously flaws assumptions here. These are either smoke or he doesn't know he's even made the deeper assumptions--and therefore doesn't think the can be questioned.

Guth realized that an inflaton field filling space could behave similarly—turning on for a burst and then turning off—which would allow repulsive gravity to operate during only a brief window of time. That’s essential.

Right. But just because fields can vary it doesn't follow they will vary in specific ways, especially when those ways are astronomically unlikely to occur naturally. What causes the field to suddenly vary and then conveniently cease?

Taken together, the two processes yield an ever-expanding block of cosmic cheese riddled with an ever-growing number of holes. In the more standard language of cosmology, each hole is called a bubble universe (or a pocket universe).

He needs to stick to a clear definition and use of "universe". Is it a section of contiguous space in the larger Big Bang or is it a separate, unknown multispace in which a series of Bangs have occurred?

Back in the 1980s, when Vilenkin realized the eternal nature of inflationary expansion and the parallel universes to which it would give rise, he excitedly visited Alan Guth at MIT to tell him about it.

Note the subtle change in language: "would" not "could." He's moved from speaking honestly about possibilities to asserting certainties in the absence of hard evidence.

Sentiment today is very different. When Vilenkin was first thinking about the Inflationary Multiverse, the evidence in direct support of the inflationary theory itself was thin. So, to the few who paid any attention at all, ideas about inflationary expansion yielding a vast collection of parallel universes seemed like speculation piled upon speculation. But in the years since, the observational case for inflation has grown much stronger, once again thanks largely to precise measurements of the microwave background radiation.

Inflation simply refers to the relative speed of expansion observed in the Big Bang. I don't follow how we necessarily posit extra bangs with new inflationary characteristics observationally.

Indeed, if the inflationary theory is correct,

Back to "if". Also, he is conflating this version of inflationary theory with all others by presuming it's the only one.

The surprise lies in the details. Most of us wouldn’t expect worlds to repeat; most of us wouldn’t expect, every so often, to encounter versions of ourselves, our friends, our families. But if we could journey sufficiently far, that’s what we would find.

The more basic issue is that we wouldn't expect worlds to occur at all, let alone repeat.

Peter Higgs, who with important contributions from Robert Brout, François Englert, Gerald Guralnik, Carl Hagen, and Tom Kibble

Part of the issue is that "science" presents itself as an abstract body of objective truth rather than a collection of sayings by specific, fallible people. That gives "science" a false sense of transcendent truth to be accepted via blind faith and turns scientists into priests.

We’ve seen that inflationary expansion yields vast regions whose properties on average are homogeneous. Measure the temperature, pressure, and average density of matter in two large but separate regions within a bubble universe, and the results will agree. The results can change over time, but the large-scale uniformity ensures that, on average, the change here is the same as the change there. As an important case in point, the mass density in our bubble universe has steadily decreased over our multibillion-year history, thanks to the relentless expansion of space, but because the change has occurred uniformly, our bubble’s large-scale homogeneity has not been disrupted.

But if time itself is accelerated universe-wide, wouldn't it allow more or less of this change to occur at different paces, skewing the result and making talk of "years" meaningless?

Smaller inflaton values correspond to later moments. Note that the curves could be extended infinitely far, so from an insider’s perspective, space is infinite.

If I'm following, I don't see how an actual infinite results. If the space is based on inflation as perceived by the observer, it may seem to be infinite but in fact when inflation runs down, so does space and so does time.

If there were more to the universe than length, width, and height, surely someone would’ve noticed. Well, not necessarily.

Didn't they? Haven't the theologians of various religions been talking about other worlds and dimensions for millennia? It's seems, though, that these worlds are declared unfit for consideration from the out set because they weren't postulated by "science."

This leads to a grand challenge: using pen, paper, possibly a computer, and one’s best understanding of the laws of physics, calculate the particle properties and find results in agreement with the measured values. If we could meet this challenge, we’d take one of the most profound steps ever toward understanding why the universe is as it is.

This would still only describe how the universe works. It wouldn't touch the question of why.

The theory will remain speculative until a convincing link to experiment or observation is forged.

Will it? That wasn't the case with naturalistic evolution. Though never directly observed through experimentation, it is now an unassailable "fact." Sheer desire often overrides experimentation.

Such approximations illustrate my earlier assertion that the art of physics lies in deciding what to ignore.

Ignoring deity and personality conveniently and greatly simplifies physical observation. That gives physicists a definite motivation to try. Also, note that this is described as the "art" of intentional ignorance, implying there is nothing scientific at all about the culling process.

approach suggests that his chance of winning is about 10 in a billion, .00000001. But, as in the previous example, this approximation fails to account correctly for multiple wins.

More importantly it fails to account for the fact that he faces the same odds each time. So each attempt is the same one in a billion. He would have to pay the lottery ten times with ten tickets on the same day to improve his chances to ten in one billion, as the example suggests.

The Past and Future of Cyclic Universes

All of this requires the assumption that the 3-branes inhabit some sort of space and are trapped in some kind of transcendent timestream. Even if correct, it only backs up the question of what that space is and how it got there. It provides no practical answers to anything.

Part of the appeal of a cyclical cosmology is its apparent ability to avoid the knotty issue of how the universe began. If the universe goes through cycle after cycle, and if the cycles have always happened (and perhaps always will), then the problem of an ultimate beginning is sidestepped.

Only by presuming an infinite regress by faith. Otherwise, all cycles must have a beginning, no matter how long ago it was.

The braneworld Cyclic Multiverse has no need for a beginning to time.

This ignores the facts that the braneworlds themselves require some form of time in which to operate. It doesn't relieve the problem: it obscures it.

This makes clear why a long-standing effort has been to find a relatively common astronomical species whose intrinsic brightness can be reliably determined without the need to stand right next to it. If you could find such so-called standard candles, you’d have a uniform benchmark for judging distances. The degree to which one standard candle appeared dimmer than another would tell you directly how much farther away it is.

But this doesn't take into account the possibility of items in between, filtering or deflecting the light in some way.

We live in a privileged age.

Convenient.

Such cosmic downgrading, from headliner to extra, exemplifies what scientists now call the Copernican principle: in the grand scheme of things, everything we know points toward human beings not occupying a privileged position.

Yes and no. We do not appear to be the geographical center of anything, but when all the scales are weighed, we must occupy a very privileged position in the universe in order to exist at all. The fine tunning that allows life add we know it is far more complex a kind of privilege that simply being "in the middle."

But the earth is not the only planet in the universe, let alone in the solar system. There are many others. And this fact casts such questions in a very different light. To see what I mean, imagine that you mistakenly think a particular shop carries only a single shoe size, and so are gleefully surprised when the salesman brings you a pair that fits perfectly. “Of all possible shoe sizes,” you reflect, “it’s amazing that the single one they carry is mine. Is that just a lucky coincidence? Is there a deeper explanation?” But when you learn that the shop actually carries a wide range of sizes, the questions evaporate. A universe with many planets, situated at a range of distances from their host stars, provides a similar situation. Just as it’s no big surprise that among all the shoes in the shop there’s at least one pair that fits, so it’s no big surprise that among all the planets in all the solar systems in all the galaxies there’s at least one at the right distance from its host star to yield a climate conducive to our form of life. And it’s on one of those planets, of course, that we live. We simply couldn’t evolve or survive on the others.

Wow. The obtusness here is impressive. The fact that the earth is the only place where life of any kind has been observed makes this whole defense moot at this point and completely validates the original question, based on current evidence. (And to base an objection on the possibility of future evidence is an exercise in faith, not reason.)

So there is no fundamental reason why the earth is 93 million miles from the sun. A planet’s orbital distance from its host star is due to the vagaries of historical happenstance, the innumerable detailed features of the swirling gas cloud from which a particular solar system coalesced; it’s a contingent fact that’s unavailable for fundamental explanation. Indeed, these astrophysical processes have produced planets throughout the cosmos, orbiting their respective suns at a vast assortment of distances. We find ourselves on one such planet situated 93 million miles from our sun because that’s a planet on which our form of life could evolve. Failure to take account of this selection bias would lead one to search for a deeper answer. But that’s a fool’s errand.

An impressive exercise in circular reasoning: we can say that there is no fundamental reason for earth's location because we presume in advance that there is no fundamental reason for earth location. It's the standard stacked-deck approach again.