What Is Nothing?

Close your eyes and try to imagine nothing.

Too late. Odds are, you’ve already thought of something: maybe the color black, or the word “nothing,” neither of which are nothing.

Pondering nothing could be considered, at best, a form of meditation, and, at worst, a total waste of time. Or, it would be, were it not for the simple fact that there is an unresolved question at the heart of physics that requires at least some consideration of this matter, or lack thereof: why is there something (our universe) instead of nothing?

Nothing is a concept so deceptively simple that it inhabits the strange intersection of science, philosophy, and language itself. Like a child asking “Why?” to the point of absurdity, trying to get to the bottom of this problem can be pretty frustrating, so I enlisted the help of a physicist and a philosopher to get an idea of what—if anything—”nothing” means. Apparently, this is also a frustrating question for experts.

What is nothing, according to physics?

Sean Carroll is a theoretical physicist and cosmologist at California Institute of Technology. Nothing has been a recent concern of his, insofar as it relates to something.

In a recent blog post, podcast episode, and chapter in the Routledge Companion to the Philosophy of Physics, all entitled “Why Is There Something, Rather Than Nothing?” Carroll attempted to answer this question in the simplest possible terms.

“Science and philosophy are concerned with asking how things are, and why they are the way they are. It therefore seems natural to take the next step and ask why things are at all,” he wrote in the chapter. “Our experience of the world, which is confined to an extraordinarily tiny fraction of reality, doesn’t leave us well-equipped to think in appropriate ways about the question of its existence.”

True nothingness is very different from simply “empty space,” even though that might be a serviceable, everyday definition, Carroll told me on a recent Skype call.

“In quantum field theory, which we think is our best way of describing the universe that we have right now, empty space is kind of interesting,” he explained. “Even if it’s as empty as it can be, there are still quantum mechanical [properties]—they’re just in a zero-energy state not doing anything. But you could probe the vacuum, as particle physics does, and discover its properties.

“Empty space is a very interesting place in modern physics; there’s a lot going on, whereas, if it were nothing, there would be nothing going on,” he said.

Quantum states are wave functions that measure the unpredictable energy levels of atoms and particles to a high degree of precision. A quantum mechanical system in its lowest energy state might look a lot like nothing, even from a mathematical perspective, but there would still be minute particles and energy bouncing around in there.

Whether it’s a hole in the ground or the vast swathes of space between celestial bodies, these “empty” spaces are filled with something that has physical properties. That vacuum is not nothing, at least as far as Carroll and his contemporaries are concerned.

But that’s only one way of understanding this problem. The other is even more mind-bending: the absence of space-time altogether, “empty” or otherwise.

“Just truly nothingness—not a quantum theory vacuum—just the absence of anything,” Carroll said. “Given that we’re in a post-general relativity world, we know that space and time are not fixed and absolute; they are dynamical. Einstein said that space and time are warped by energy, so it’s probably better to think of nothing as the absence of even space and time, rather than space and time without anything in them. There’s a big difference between empty space and nothing.”

While it’s important to keep this definition of nothing in mind, Carroll added, it’s not really of any service to the field of physics. “‘Something’ is interesting; nothingness is interesting only insofar as it's the absence of something,” he said.

Ultimately, Carroll said, he’s not losing sleep over the question of “What is nothing?” even if it’s a fascinating thing to think about.

“I think the question of ‘Why is there something rather than nothing?’ is interesting, but the answer probably is, ‘That’s just the way it is,’” he concluded. “There’s probably not anything deeper than that. It’s not like nothing is some mysterious unknown; it’s just the absence of anything. That’s all there is to say about it. There’s nothing more to learn about nothing. All there is to learn is about something.”

What is nothing, according to philosophy?

Science doesn’t have a monopoly on nothing. Jim Holt is a philosopher who has written about a wide array of scientific topics, from the origins of the universe to a philosophical history of jokes. He has also addressed quantum mechanics and nothingness in a TED Talk entitled “Why does the universe exist?”

For Holt, pure nothing is not only intelligible for the human mind, but describable using philosophical reasoning, which is another great starting point for someone who is mulling this question. He argues that “nothing”—not empty space filled with invisible things, as put forth by quantum physics, but literally nothing—can be easily described using only formal logic.

“You can coherently describe a state of nothingness; it’s easy to do,” Holt told me over the phone. “It’s a state in which everything is not self-identical. If for all x, x is unequal to x; that sentence in logic describes a state of nothingness. It doesn’t help the imagination, but it doesn’t give rise to any contradictions. It can only be true if nothing exists, because if anything exists, it equals itself. ”

Using scientific reasoning to understand how something emerged from nothing, Holt contends, is a physicist’s attempt to answer a metaphysical question. Specifically, he takes issue with quantum field theory, which posits that the universe may have exploded out of a quantum vacuum thanks to inflation.

Inflation theory was initially proposed as a kind of addendum to the Big Bang theory in the 1980s. It contends that cosmic inflation pushed the universe from the quantum scale to the astronomically huge in a very short period of time (between 10-35 seconds and 10-33 seconds after the Big Bang), giving rise to the scale and structure of the universe we now live in.

But if the universe sprang into existence from nothing, in accordance to a set of physical laws, then where did those laws come from? Did they exist before the universe? If so, wouldn’t that mean that the universe did not emerge from nothing? “[According to physicists], the laws of quantum field theory can summon a world into existence out of the abyss, so they’re very mysterious entities. But they are still entities. They are not nothing,” Holt told me.

So, what is nothing then? According to Holt, even if we can’t describe its properties—or even imagine it—it is conceivably the way things could have turned out.

“Nothing is the simplest possible way that reality could turn out; it’s the least arbitrary, because it excludes everything,” Holt said. “Once you take that seriously, you begin to think, ‘That’s how it should have been; why should there be something rather than nothing?’ Not only is there something, but there is a very particular kind of something that we see around us.”

If anything, nothing is an invitation to consider that which does exist—which is something, to be sure. Nothing, for all its nothingness, is one of the meatiest intellectual morsels for us to chew on.

“It’s an interesting mix of philosophy, science, conceptual analysis, and theology, and deciding the limits of language,” Holt said, “For people who are curious about abstract intellectual matters, it’s a feast.”

Nothing really matters

Our brains are wired to understand things as discrete entities, but that doesn’t mean we can’t wrap our minds around the idea of the absence of any properties. In fact, doing so can create a more nuanced appreciation of the universe.

“I do think [nothing is] understandable,” Carroll said. “We don’t think that the universe has an edge in space, but it might have had a beginning—we don’t know that for sure, but it’s certainly plausible. If there’s a [beginning] moment, and after that moment there was something, then there’s nothing on the other side. You’re tempted to say, ‘Before that moment, there was nothing.’ But it’s better to say, ‘There’s no such thing as before that moment.’”

Holt said nothing may be intelligible via logic, but you probably won’t be able to visualize it unless you have a cable sports subscription. “I’ve never been able to understand nothingness completely, but I can get close to it when I watch professional bowling on television,” he joked.

This reference to bowling may not have any scientific or philosophical validity, but it does illustrate the absurdity of trying to understand that which necessarily cannot exist. Still, at the very least, asking a question as absurd as “What is nothing?” reminds us that there will always be ideas at the edge of human understanding, and defiant humans willing to confront that absurdity and dig deeper.

“I’m open to having better answers,” Carroll says. “Satisfaction is something we can hope for, but not demand, when we talk about the universe. It’s up to us as a species to cultivate the intellectual maturity to accept that some questions don’t have the kinds of answers that are designed to make us feel satisfied.”

So, what have we learned here? Hopefully, something.

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