Marie scrunched up one eye, equally confused. “What are you talking about? Of course that was the plan. I knew the headband would show me things I couldn’t see from the outside.”
Daniel held a finger in the air like an exclamation point. “Then you didn’t take it off. It must have fallen when you leaped.”
“Yeah, it did. All three of us jumped to a balcony inside the smokestack. The headband probably fell to the bottom when I hit. Of course, it’s gone now, blasted somewhere up there.”
“No, no, no,” Daniel said. “I wasn’t talking about jumping into the smokestack. I mean the first time you leaped, back at Fermilab. It must have fallen off there.”
“Okay, Daniel, now you’re not making any sense,” Nala said. “Marie had the headband inside the 4-D bubble. That’s how we got out.”
Daniel gave a quizzical look to both of them, still clearly confused. “Hang on, let’s reset. I talked to Jan just a few minutes ago. He said he has the headband in his office. He was holding it while we talked. He wants to know what he should do with it.”
Marie leaned forward, “Jan has the headband? How is that possible? We were standing at the top of the smokestack right here in Austin, a thousand miles from Fermilab. It was on my head when I jumped. The headband fell into the smokestack; it couldn’t be anywhere else.”
“She did,” Nala confirmed. “I saw her. How could Jan have it now?”
Daniel looked at Nala and then Marie, holding one hand to his mouth and tapping a finger on his lip. “Jan said that security picked the headband up off the floor at Fermilab. The security guy said he saw you set it on the floor just before you leaped, as if at the last minute you decided you didn’t want it.”
“Well, that’s ridiculous,” Marie said, waving it off with a flip of her hand. “I had the headband on when I landed—” Marie covered her mouth. “Oh shit.”
Nala sat bolt upright in her chair. “Double shit. You didn’t have it when you landed, did you? When we hooked up, you told me you thought you’d lost the headband but decided that was part of the hallucination.”
Marie ran through her memories of that first leap into the singularity. The sound of steps behind her. The guard calling out. Her determination to jump, backing up and then leaping into the pit. But there was something else. A hesitation, a last-minute thought. Could she really have set the headband down?
Impossible. She had worn it inside the 4-D space. She’d visualized inside. The headband had guided them to the smokestacks.
“No. Of course I had the headband,” she said, staring off into the distance. “At first, yes, I did lose it… that’s when Thomas was dead. But then, there was a flash from the light. I blacked out, and when I woke up, the band was on my head.”
Nala shook her head continuously, a strange look falling across her face. “Superposition. Multiple eigenstates, each existing only as a probability.” She looked at Marie. “You had the headband and you didn’t. It was inside the bubble and it wasn’t.”
Marie tried to absorb what Nala was telling her. Superposition was being blamed for Thomas being dead and then alive, but this seemed like an even greater paradox. “If I didn’t have it, how did we get to the smokestacks?”
“Don’t expect sensible cause and effect,” Nala said. “This is quantum physics. If you try to match it to our day-to-day world, you’ll only get more confused. Yes, you had the headband, and no, you didn’t. All at the same time. But as soon as we jumped into the smokestack, we left the quantum effect, an external observer came into the picture and the dice stopped rolling.”
Marie’s heart quickened. She worried about what this detour into the bizarre meant to her state of mental health if Nala was right.
The words were senseless, but Nala spoke with the seriousness of a scientist. “The external observation ended the superposition. The random probabilities settled on a single result, and as it turned out, you didn’t have the headband after all. From an external perspective, you never did. You set it on the floor. Security picked it up and gave it to Jan.”
“But our memories.” Marie flinched at the confusion of thoughts. If she wandered far enough down this mental trap, the hallucinations would no doubt return. “You have the memories, too.”
“I do,” Nala said. “And those memories are accurate, but that doesn’t make them real. I know it sounds strange, but I think Jan has confirmed the final state. You left the headband outside.”
“So how do you account for the memories?” Daniel asked. “It sounds like you both remember the same thing.”
Nala thought for a minute and laughed. “It’s definitely confusing. If an electron could think, this is probably how it would feel too. Marie and I have been in quantum superposition, but now we’ve settled back into reality. What’s left in our heads is… well, a phantom memory, a leftover, an unused probability from the multiverse.”
“You think we really live in a multiverse?” Daniel asked. “Every outcome exists?”
Nala shrugged. “Marie visualized it. A hundred different versions of each of us. Not an infinite number of probabilities, maybe not even every probability, but a big number.”
Her statement hit home. Marie gazed off into nothing. The events of the past several weeks now made complete sense. “I was a probability,” Marie said slowly. “Zin said so. Core said so.”
Daniel echoed the statement Core had made during their visit. “Nothing is certain. Outcomes follow probabilities.”
An intensity flooded Marie’s thoughts, and she turned to Daniel. “Did Core know? Is that why Zin chose me? Was this whole thing a manipulation from the start?”
Daniel shook his head. “Unknown, but highly doubtful. It’s hard to imagine a mechanism for peering into the future, even if you are a quantum computer.”
“Don’t expect the quantum world to make sense,” Nala repeated. “An artificial intelligence based on quantum computing may be wholly different from anything we can imagine. Who knows what Core can do?”
Nala had an impish smile on her face. “But I do know one thing.”
“What’s that?” Daniel and Marie asked together.
Nala reached for Daniel’s hand and interlaced her fingers with his. Her brown fingers complemented his pink. She reached out with her other hand and took Marie’s.
“Outcomes really do follow probabilities.” She turned to Daniel. “What happens tomorrow between you and me? Will we be together or not?”
Without waiting for an answer from Daniel, she turned to Marie. “What will you do next at NASA? Will you wear the headband again now that you know it hasn’t been destroyed? Will you visit Haiti after our chat? None of these outcomes, the important stuff and the trivial, has been determined. But there are plenty of probabilities, and some outcomes are more likely than others.”
Nala gripped their hands tightly. “If you ask me, that’s the multiverse in a nutshell. We live it every day. Today is the result of yesterday’s probabilities, and tomorrow will materialize from today’s.”
“Sounds more like philosophy than science,” Daniel said.
Nala smiled. “Yeah, it does, doesn’t it? And here I thought I was strictly a scientist.” She lifted Daniel’s hand and kissed it and then did the same to Marie’s. “The quantum world will do that to you.”
Afterword
I hope you enjoyed the story. I had a lot of fun writing it. Like most people I relish a good adventure, but I could spend days contemplating the unanswered questions of our fascinating world. If this story spurred deep thoughts about the structure of the universe or why it works the way it does, then I’ve been successful.
I also had fun writing this story because I’ve developed an affection for the three scientists that held hands in the final chapter. I would love to join them in their conversation out on the hotel patio in Austin. It makes me think of Stranger than Fiction, the movie with Will Ferrell and Emma Thompson in which an author meets her character. That would be fun.
Just as
I did after the first book (Quantum Space) I thought I’d write one more chapter. I’ll step out of the story and talk about the science and the science fiction by diving into three scientific topics: critical density, nothingness and quantum superposition. Don’t roll your eyes; I’ll be nice.
Critical Density
While drifting effortlessly in her float pod, Nala contemplates the density of space in Chapter 6, Bosons. Later, in Chapter 38 and 40, she explains that the universe is flat because its density exactly matches critical density, measured to be 9.47 × 10–27 kg/m3.
First, let me say that every bit of this is real science, as accurately as I could write it. Second, it absolutely blows my mind that our universe is flat, and it doubly blows my mind that so few people realize how mind-blowing this bizarre coincidence is!
Allow me to expound. In 1915, Albert Einstein published his Theory of General Relativity, which is all about gravity and the shape of space. Space, Einstein said, is curved wherever there is mass. The curvature is what we experience as gravity. But curved into what? Einstein’s explanation required extra dimensions of space that we cannot see.
Fast-forward a hundred years and dozens of confirmations of Einstein’s theory. As it turns out, space really is curved into an extra dimension and remarkably this curvature is measurable with highly accurate lasers. How?
Space can have positive or negative curvature, or it can have no curvature at all (flat). Like this:
You probably learned in high school geometry that the sum of the angles inside any triangle always equals 180 degrees. Right? But when space is positively curved (the top image), the sum of those angles is slightly more than 180. And when space is curved negatively, the sum is slightly less than 180. Only when space is flat do the angles inside a triangle sum to 180.
For our routine life on Earth, the curvature of space is negligible, and sure enough, any triangle you measure will sum to 180 degrees. But shine three lasers between Earth, Venus and Mars to precisely measure the triangle formed by the planets. You won’t get exactly 180 degrees; the sum of the angles will be a little larger as a result of the positive curvature of space around the sun. (Full disclosure: No one has ever performed this specific experiment, but NASA’s Gravity Probe B in 2004 and the LAGEOS satellite in 1976 both did something similar to measure the warping of space around the Earth. Answer: space is indeed curved.)
What if you wanted to measure the curvature of the whole universe? Is the universe itself curved? If so, does it curve like a sphere or a Pringles potato chip?
Astronomers have been eager to find out ever since Einstein explained how space curved. They got their chance in 2001 when NASA launched the Wilkinson Microwave Anisotropy Probe (WMAP). The probe took pictures in every direction, measuring the 2.7 Kelvin cosmic microwave background (CMB) radiation, the residual radiation left over from the Big Bang. The results looked like this (which Nala explains in Chapter 40, Density):
With WMAP’s sensitive instruments and some clever thinking, mission scientists measured overall curvature. What did they find? The universe is flat. Not everywhere—there are local positive curvatures and local negative curvatures—but as a whole it all balances out to perfectly flat. An enormous triangle spread across the whole universe would have angles that add to exactly 180 degrees. That’s important. But before I cover why, let’s talk about density.
Measuring triangles with lasers or estimating curvature from the CMB radiation map is what scientists call the geometric approach but there’s another way to measure the shape of the universe, called the accounting approach.
In Chapter 40, Nala takes a stab at explaining it:
“The universe is expanding, right?” she says. “And gravity tries to halt that expansion by pulling things together. More mass, more gravity. Critical density is a number with deep meaning. It tells you the precise amount of mass that is needed to exactly cancel expansion.”
In this story, these two forces are represented as the interaction between quarks and the HP boson. In our real world, quarks are well established as the foundation for matter, and matter is what causes gravity. But in the real-world HP bosons don’t exist. Oh well, the story is science fiction.
If HP bosons are just a figment of my imagination, what really causes the universe to expand? The answer: unknown. Astronomers call it dark energy, but that term is really just a placeholder. Another way of saying, we don’t really know. Seems like we need some aliens to come along and explain it to us.
But even if scientists haven’t discovered the force itself, they can measure how fast the universe is expanding. It’s called the Hubble constant (H) and WMAP provided the most accurate measure anyone has ever had. Along with Newton’s gravitational constant (G), physicists derived this very simple equation for critical density, ρc.
Critical density is the balance between H and G, between the expansive force and the gravitational force (which derives from mass). Critical density is the bullseye on a target, a what-if calculation of the relationship between these two opposing forces.
To find out whether we’ve hit the bulls-eye, we need to know the actual density of the universe. Can we measure it? Get a really big scale and pile every quark, every atom, every star, planet, nebula—every shred of mass in the entire universe—on one side. Place the mysterious expansive force on the other side of the scale.
What happens? Well, your eyes should pop out of your head when you find that the scale exactly balances. Critical density equals actual density. The amount of mass needed to exactly cancel the expansive force is precisely how much mass there is in our universe. The WMAP mission (and the European Space Agency Planck mission in 2013) both performed something like this humongous scale by accurately measuring real-world values for H and G and plugging them into the equation above.
To the accuracy humans can measure, we live in a universe of critical density, otherwise known as a flat universe. What does this mean? It means the entire universe sums to this digit: 0.
The universe is zero, nothing, nada, zilch. Everything we see around us—the stars, galaxies, everything that floats out there in empty space—is simply a local perturbation of energy and mass. The universe can be thought of as a wave where every trough balances every crest. Taken together the sum is nothing. This tells us with some certainty that the universe sprang from nothing. Exactly how this springing-thing happened is not yet clear, but scientists have confirmed just in the past ten years that nothingness was the original state.
The universe is not just a random pile of stuff—the result of a cataclysmic explosion. We shouldn’t think of the Big Bang as just a larger version of a supernova, it was a very different kind of event. The Big Bang was literally something from nothing.
This newfound knowledge should be disturbing or enlightening or emotional in some way to every person on the planet. We know where we came from. We know what existed prior to the Big Bang—nothing.
Nothingness
So, what is nothing? In this book, I called it the void though physicists and cosmologists use other words depending on the topic. For example, in brane theory they call it the bulk. Sometimes you’ll see references to hyperspace. In mathematical descriptions it’s called Hilbert space. In my opinion, none of these terms are as compelling or as conjuring as the void.
The void is not a place. It’s not space of any kind. It has no dimensions, no contents, no volume, nowhere to put anything of substance. It also has no attributes (length, density, position, etc.) except for the sole attribute that it represents the absence of everything.
Light cannot propagate across the void because there is no “across”. Quarks, leptons and bosons cannot exist within the void because there is no “within”. In Chapter 20, Void, Nala pushes a stick beyond the vertical edge of her prison. The stick disappears into nothingness, crackling and sizzling as it goes. (Just a guess on my part. What exactly is the sound of a trillion quarks simultaneously being eliminated from existence?)
The void is u
nquestionably crazy stuff. Instead of describing the void, it’s easier to describe space. The void would then be anything else. But a word of warning—it gets crazy from here. My advice, take two aspirin before you continue reading.
The multiverse. Multiple universes.
If you enjoy science fiction, you’ve probably come across a story or two that incorporated the idea of multiple universes, or parallel universes. This is the notion that the universe we see (about 14 billion light-years of space containing billions of galaxies) is not all there is. In fact, there may be many universes like our own, possibly an infinite number of them.
Complete fantasy, right? Certainly unscientific.
I don’t think so. Not every idea related to multiple universes is scientifically testable, but some are. And even if only one idea is testable, it makes the question of multiple universes a valid scientific endeavor. Others agree because quite a few physicists, astronomers and cosmologists are actively working in this field.
Take Max Tegmark, for example. He’s a professor of physics at the Massachusetts Institute of Technology—not exactly a hotbed of crackpots. Tegmark has examined each of the current multiverse ideas in detail and has identified four levels of multiverses.
In a Level I multiverse, we live in a sea of never-ending infinite space. Within that space, we can see only a “small” sphere with a diameter of 13.8 billion light-years (that’s how long it’s been since the Big Bang, thus we have no ability to see objects that might be farther away). But this visible sphere is merely a pocket universe—a bubble within the never-ending sea. The bubble came into existence from a Big Bang and a period of inflation (the few microseconds after the Big Bang during which space inflated faster than the speed of light). If this model represents the true nature of our universe, there could be many other pocket universes out there, far beyond our limited view, each of them also a result of local inflation within the infinite sea.
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