Into the Unknown, page 7
I also believe that not engaging in the “something-from-nothing” issue is a bit of a cop-out—science itself has led us to the precipice of perhaps the greatest existential mystery that has impelled human thought and belief for uncounted generations. To be sure, there is currently a handover that must happen between science, philosophy, and theology somewhere around 10−43 seconds, but I don’t think scientists are totally off the hook, because there may well be another turtle that is accessible to empirical inquiry of the future.
Before we can get into if or how one might generate “something” from “nothing,” we need to take a step back and talk about “nothing” with more precision. When I teach a course on this, we spend an entire class period talking about “nothing,” for which I am sure there are cynics out there questioning the use of tuition dollars. However, the thing is, there are different types of “nothing.” In fact, many types of nothing have been expounded on in academic discussions, but I will limit us to three main types here:
The most trivial type of nothing in this scheme is Type 1, which is what I suspect many people first think of when they think of the concept of “nothing.” In this case, we have a turnkey universe, there just isn’t anything in it—no matter, no energy, no force fields. To be clear, we can’t even achieve this type of nothing in a lab—even in the most extreme ultravacuum chambers, there are still fields that permeate space that we can’t avoid (at least not yet), such as the Higgs field, which is responsible for giving mass to things.
Type of
nothing
Matter/Energy
exists
Space-time
exists
Laws of physics
exist
1
∅
2
∅
∅
3
∅
∅
∅
Type 2 nothing turns nothingness up a notch—in this case we no longer have the very fabric of space-time. In a real estate analogy, it would be like having a permit to build a house, but not yet even having the land to build it on. There are, however, a whole mess of zoning regulations that determine what can and cannot be done. This type of nothing no longer has “things” in it or an arena in which there even could be things, but underlying laws “exist” that inform what is possible. This type of nothing overtly raises the question of where these laws reside if they don’t have a universe to reside in, but this issue extends beyond this type of nothing (and which we will come back to in the chapter on the laws of the universe).
One can imagine a higher power in the context of Type 2 nothing, and they might determine what is and is not possible—in other words the laws that govern the universe reside with them. This is indeed the perspective of many theologies and may well be correct for all I know. But we have only managed to nudge the philosophical can down the road—even a higher power is “something,” so we still have something instead of nothing.
The most extreme type of nothing is Type 3. No things, no fields, no arena, and no underlying framework or set of laws. Truly a complete and utter void that defies language—even calling it a “void” might suggest that there is something that is empty. This type of nothing is the most challenging to reconcile with there now (demonstrably) being something for us to make for dinner. In this type of nothing, it is not clear there is even room for a higher power—because that would not be nothing.
If you are expecting me to resolve this philosophical quandary, I’m afraid your faith is sorely misplaced. I’m just as confused as anyone. I have (mostly) come to terms with only being able to go one more turtle down at a time, and then hold on to some hope that perhaps when we have understood that next turtle things will be more clear.
Before we go on to speculate about what might be one turtle down, I want to pause and bring up a curious feature of the observable universe. Let’s imagine for a moment that you want to buy a car, but you have no money. A very kind and generous friend loans you the money with no interest, and you buy the car. Now you have the car, but you owe your friend exactly the amount of money the car is worth. So, in some very real sense your net worth is zero. It turns out the universe is in a similar situation, only the loan was a lot more extreme.
The “net worth” of the observable universe appears to be effectively zero (or as close to zero as we can determine). We can estimate the entire mass/energy of the observable universe (which is positive), and we can estimate the entire gravitational potential energy of the universe (which is negative), and these two seem to cancel each other out. If the universe has a net worth of nothing, then instead of asking, “Why do we have something instead of nothing?,” the question becomes “What was the mechanism for the loan?”
We are clearly on the borderlands of science here, but that hasn’t kept humans from thinking about what might have preceded17 the universe as we know it, even if these conjectures are (currently) outside the realm of empirical inquiry. The general tactic is to consider the physics of the universe as we understand it and try to extrapolate possibilities.
One concept with a long history is that the universe is created and destroyed in a cycle. The idea of a cyclic universe has been present in various cultures and mythologies throughout history. For example, in Hindu and Buddhist cosmogonies, there are the concepts of kalpa and saṃsāra, which refer to cycles of creation, destruction, and rebirth of the universe.18 Ancient Greek cosmogonies are rife with notions of cycles; Empedocles (fifth century BC) developed a cyclic cosmogony that even included the concepts of love and strife.19
A cyclic universe understandably has broad appeal—it nicely skirts the issue of having a “beginning,” and there is an important psychological element to believing there will be another cycle that will start anew, no matter how bad things might seem now. The general modern idea of a cyclic universe proposes that the universe undergoes an infinite series of cycles, with each cycle beginning with a “big bang” and ending with a “big crunch.” According to this hypothesis, the universe expands and cools down after the big bang, eventually slowing down and collapsing in on itself due to gravity, only to rebound and expand again.
This was all well and good and seemed totally plausible until we went out to empirically test how fast the expansion of the universe was slowing down. This led to the discovery of dark energy (I am confident in your ability to turn pages and go find the chapter on dark energy, so I will blatantly skip over details here). To be certain, there is a lot we do not understand about dark energy, but insofar as we understand anything about it, we know it is getting stronger with time and the expansion of the universe is accelerating. Unless there is some type of phase transition in the cards (which I absolutely do not rule out), we have no cause to think this acceleration will stop. In which case, a cyclic universe is pretty much out of the question, which is kind of a bummer.
Among physicists, the most popular explanation for the origin of the universe may be quantum mechanics. One of the great things about quantum mechanics is that it gives us a lot of loopholes to play with in terms of what is “allowed” to happen, which provides nearly unlimited fodder for pseudoscientific conjectures. Nevertheless, quantum mechanics itself is well-established and empirically verified. One aspect of the quantum world is that concepts like “cause” and “effect” are not even rigidly defined. This decoupling of cause and effect is like a breath of fresh air in a room full of hypotheses about what “caused” the universe to be created (especially if time didn’t exist)—giving us this cool trick to conjecture that perhaps there wasn’t a “cause” at all, because that very word loses its meaning.
Another key feature of quantum mechanics (one that we will encounter in more depth in the chapter on black holes) is that particles can and do pop in and out of existence from “nothing,” which is required by the very nature of the uncertainty principle—in this case, energy and time can’t simultaneously have precise values, and “nothing” has a very precise value of 0. I will grant you that there is a world of difference between a particle popping into existence and an entire universe popping into existence, but the loophole is there. This does bring up another issue, though—for anything to pop into existence from a quantum field, there must be an underlying quantum field to begin with. So, what kind of “nothing” is that?
Of the various possible explanations for the “beginning” of the universe, this next candidate is perhaps the most abstract. The “no-boundary” hypothesis requires fundamentally thinking about time and space in a way that is far removed from your normal daily experience. This hypothesis was originally put forward by Stephen Hawking and James Hartle in the 1980s with an explicit goal of avoiding a “beginning” of time, as a result, in this proposal time has no beginning.20
The concept here is a bit abstract, so let’s turn to another analogy.
If you will, imagine a standard globe of the Earth with all the usual lines of latitude and longitude. Now further imagine you happen to be an intrepid adventurer (or perhaps you actually are and you don’t have to imagine), and you are headed to the South Pole. As you travel south, you are of course aware—as any intrepid adventurer would be—that the lines of latitude and lines of longitude are perpendicular, which is handy if you are trying to discern between the axes of north-south and east-west. Or at least they are perpendicular until you get to the South Pole, at which point something odd happens—every direction you might face is north. Not only is there no “south” anymore, but “east” and “west” have the same problem. Of course, you—standing at the South Pole—don’t perceive anything particularly different about the precise South Pole, as opposed to a few meters in either direction. This collapse of all directions to the “north” is purely a result of the standard coordinate system we have in place to describe locations on Earth.
In a nutshell, this is how the no-boundary universe proposal works: the basic idea is that time and space are orthogonal dimensions in space-time (think of lines of latitude and longitude on the equator), with time dimension effectively oriented along the north-south axis. But the trick of this proposal is that by the time we get to the “South Pole” of the universe (aka the beginning of time), there is no further south to go. If time = 0 is at the South Pole, then there is no such thing as time = −1, and therefore there is no “before” in this coordinate system.
A schematic of the no-boundary universe conceived of by Stephen Hawking and James Hartle. In this geometry, the location where time is 0 is akin to the South Pole of the global coordinate system on Earth; there is nothing farther south than the South Pole. Similarly, in this scheme, there is no time before time = 0.
Another way to think about the nature of time in this scheme is that time becomes “imaginary” or alternately that time becomes more space-like. To envision this, if you thinly sliced up the globe along lines of latitude you would end up with a stack of circles growing and shrinking in size from north to south. These circle slices are slices of space. At the South Pole, not only does the size of this slice of space become vanishingly small, but the dimension of time, which started out as orthogonal to these slices, has curved into the same plane as the dimension of space.
This proposal of a no-boundary universe neatly gets around the standard notion of causality and what came “before” the universe because it avoids the concept of “before” altogether. However, it notably doesn’t explain why we have an arena in which this universe can unfold to begin with.
Coming out of the gate, this next scenario might sound like pure science fiction, but it is tethered to real physics that is being actively pursued (and on which legitimate peer-reviewed papers are penned).21 This scenario is an alternative to inflation, but I include it here because it also speaks to the “What happened before the Big Bang?” question.
The gist of this scenario is that our universe could be a multidimensional “brane” (short for “membrane,” which is traditionally only two dimensional) that lives in a volume of yet one extra dimension (and because we are so good at naming things, we call this the “bulk”). By analogy, I like to think of big flat pieces of sea kelp floating in the ocean—where our universe is the kelp and the bulk is akin to the water—which is a peaceful counterpoint to what is happening here. The key is that our brane is not the only one, in fact there may be an infinite number for all we know (which is very little). If two of these universe-branes collide, a whole ridiculous amount of energy is injected into those brane-universes. One of the features of this scenario is that it doesn’t have a time = 0, thus there is no “beginning” of time, rather there is a possibly infinite time in this metaverse in which branes collide and move apart.
I warned you that it sounded like science fiction. The thing is, though, that there is real physics that provides just enough circumstantial evidence for us to not abandon this theory. The whole crazy idea of colliding branes is fundamentally grounded in another possibly-crazy-but-beautiful idea called “string theory,” which we will talk more about in the chapter on other dimensions. Isn’t it annoying how the topics of these chapters get intertwined? Believe me, I hear you. Imagine trying to figure out in what order to present things in this book to begin with. But the universe is complicated and entangled that way, and perhaps we shouldn’t be surprised that many of the unsolved mysteries are connected.
The good news is that this so-called “ekpyrotic” scenario makes some empirically testable predictions that differ from the standard inflationary paradigm, including predictions for the spectrum of primordial gravitational waves that have not yet been detected. My read of the current research status is that the results, so far, lean toward inflation, but I am not quite ready to close the book on this crazy ekpyrotic scenario. Heck, even if colliding branes were not responsible for the Big Bang, not-colliding branes could still be a valid formulation of reality.
But where did the branes come from to begin with?
The Big Bang and black holes are the two astrophysical environments in which we encounter annoying singularities and the laws of physics as we understand them get into hot water. This shared property brings us to the next possible origin for the universe.
You may also note with intense curiosity that these two environments kinda sorta seem like opposites—for example, space itself flows into black holes, but out of the Big Bang. In fact, doesn’t the Big Bang itself seem exactly what one might expect from the opposite of a black hole—a white hole? Yep. In fact, this has an actual name—black hole cosmology, and there are once again legitimate peer-reviewed papers written about it.
There is another nifty fact to add relating to dark energy. In our current (admittedly limited) understanding of dark energy, it acts like there is a negative pressure on the fabric of space, and in Einstein’s field equations, negative pressure acts like a repulsive gravity. It just so happens that one way to get negative pressure is by stretching the fabric of space—and hey, guess what happens inside black holes? It is entirely within the realm of possibility (and is likely to remain so for a good while since we are a long way from knowing what happens inside black holes) that deep inside the black hole space itself is stretched to such an extreme that dark energy takes over—inflating space like a balloon. Sound familiar?
As far as we can tell, our observations are consistent with us living in a universe created inside of a supermassive black hole formed in a parent universe. That is the good news. The bad news is that we don’t currently have a way to empirically test this and discriminate between living in a black hole and living in a conventional (and also not currently well understood) inflationary universe.
This hypothesis is tantalizing to think about, though, and if I got to pick which one of the solutions I want to explain the Big Bang, this would be it (sadly, reality doesn’t really care what I want, or what you want for that matter). One of the side effects of black-hole-baby-universe conjecture is that our own universe could have untold offspring. Moreover, it might be possible for parent universes to pass along a form of genetics through the precise values of physical constants that get passed down,22 which could come from an aspect of string theory (in which precise properties of the universe are determined from the shape of compactified extra dimensions). If genetics are passed down, this in turn could lead to cosmological natural selection, as proposed by physicist Lee Smolin: the more well-tuned the properties in a universe are for making black holes, the more baby universes it will have.23
Need I point out that we still have to contend with where the first parent universe came from? That is at least another turtle down.
We can’t talk about the origin of the universe and not bring up the possibility of a higher being, if for no other reason than a huge fraction of the global population believes this to be true. Just as we can’t prove there is a god, we also can’t prove there isn’t, so I find that I have limited patience with explicit hard-core atheists (by which I mean people who reject the idea of a higher power as impossible, not people who simply lack a belief in the concept and lean more toward agnosticism). Given that we know there is so much we don’t know about the cosmos (let alone the things we don’t even know we don’t know), and the reality that our senses and human intellect have serious limitations, I think it is an ultimate show of human hubris to outright reject the possibility of things we don’t understand.
