Quantum mechanics works brilliantly at predicting how tiny particles behave. But it also suggests that reality itself might be far stranger than we ever imagined—with particles existing in multiple possible states at once until measurement seems to force what’s known as quantum wave function collapse.
According to What Is Real? by Adam Becker, this puzzle has led physicists to develop wildly different explanations for what’s really going on. Each interpretation sounds bizarre in its own way, yet one of them might describe the true nature of our universe. Continue reading to learn about these approaches to solving the mystery.
Table of Contents
What Causes Quantum Wave Function Collapse?
Becker explains that Bell’s theorem forced physicists to face a choice: Abandon the principle of locality (and accept the idea of instant connections across space), abandon realism (and accept that properties don’t exist before measurement), or abandon the idea that quantum mechanics is complete.
Three alternative interpretations represent different responses to this choice. They all revolve around the question of what causes quantum wave function collapse—the moment when the “probability wave” of a quantum particle’s potential location and momentum “collapses” into the specific characteristics it takes on when it’s observed and measured.
#1: Many-Worlds—Preserve Everything by Multiplying Universes
The many-worlds interpretation offers one escape route: Physicists could preserve both locality and realism by abandoning the assumption that only one outcome occurs. Becker explains that, in this view, wave functions never collapse. Instead, all possible measurement outcomes happen in parallel branches of reality. This dissolves Bell’s dilemma by denying there’s a single definite result to correlate across space. When you measure an entangled particle, you don’t get just one outcome; instead, you experience all possible outcomes. The apparent nonlocality results from observers’ limited perspective: We only see one branch of reality while remaining unaware of countless others.
Becker points out that, under this interpretation, Schrödinger’s cat is both alive and dead, but in separate branches of reality. The measurement problem vanishes because measurements don’t force choices—they simply reveal which branch of the universal wave function we happen to be experiencing.
| Many-Worlds Goes Hollywood The film Everything Everywhere All at Once dramatizes the idea of the multiplying universe—and imagines how becoming aware of these multiple worlds could feel liberating or devastating. In the film, laundromat owner Evelyn discovers she can access memories and skills from alternate versions of herself across the multiverse—versions where she became a movie star, a chef, or even a being with hot dog fingers. Her daughter Joy, pushed too far into multiverse consciousness, experiences all possible versions of herself simultaneously. This overwhelming perspective leads Joy to conclude that nothing matters since every possible outcome occurs somewhere, which drives her toward nihilistic self-destruction. This portrayal of Joy parallels the real-life trajectory of many-worlds physicist Hugh Everett III. After developing his interpretation of quantum mechanics, Everett abandoned academic science, became an alcoholic defense contractor working on nuclear war scenarios, and died at 51, leaving instructions for his ashes to be thrown into the garbage. Like Joy, Everett seemed crushed by the implications of his discovery. The film gives Evelyn a different way forward, when she learns to come to terms with the multiplicity of her existence through compassion, which some critics see as a nod to Buddhist philosophy. In fact, Buddhism aligns with what some physicists think the many-worlds interpretation really means: They argue the multiverse doesn’t continually split into new universes. Instead, all possible universes already exist in a “universal wave function.” Rather than creating infinite new realities with each move we make, we’ve always been part of this infinite reality. This mirrors Buddhists’ idea that our sense of being separate individuals is an illusion, and we’re really part of a vast, interconnected whole. The film suggests recognizing this vastness need not lead to nihilism, but can inspire us to engage fully with whatever branch of existence we happen to inhabit. |
#2: Pilot-Wave Theory—Accept Nonlocality, Restore Objective Reality
The pilot-wave interpretation takes a different approach: Accept Bell’s proof of nonlocality while restoring the objective reality Einstein sought. Becker notes that, according to this view, particles always have definite positions and properties, and they’re guided by “pilot waves” that can influence distant particles instantly. This eliminates the measurement problem by removing the need for wave function collapse. Particles follow definite trajectories determined by waves, and measurements reveal where particles are. There’s no mystery about obtaining definite results: The particles detected in any experiment existed in definite states all along; we just didn’t know which ones until we measured them.
In the double-slit experiment, for example, each electron takes a definite path through one slit or the other, but the pilot waves go through both slits and create the interference patterns that guide where electrons can land on the detection screen. This explains the wave-like results without requiring particles to somehow pass through multiple slits simultaneously. Becker explains that the price is explicit nonlocality: Pilot waves connecting entangled particles provide the “spooky action at a distance” that Bell proved was unavoidable. Many physicists find this disturbing, but the interpretation at least makes the nonlocal connections explicit rather than hiding them within the measurement process itself.
| Invisible Connections Across Vast Distances Pilot-wave theory might sound impossibly strange, but nature already shows us how invisible waves can carry information across vast distances. Humpback whale songs first recorded off eastern Australia later appear among whale populations in French Polynesia, then Ecuador, traversing vast stretches of the Pacific Ocean. The songs travel through ocean “sound channels” created by temperature and pressure gradients that allow sound waves to bounce up and down across thousands of miles without losing energy. Like the “spooky action at a distance” that links entangled particles across space, whale songs carry cultural information between cetaceans who may never meet. If whale songs traveled at the speeds of the proposed “pilot waves” that connect entangled particles, a whale singing in Australia could be heard instantaneously by whales in Ecuador, influencing their behavior just as nonlocal quantum particles instantly affect each other. |
#3: Spontaneous Collapse—Modify the Mathematics
Spontaneous collapse theories take a third approach: They modify quantum mechanics to make wave function collapse a natural physical process rather than something mysterious triggered by measurement. These theories propose that wave functions randomly collapse on their own, with larger objects collapsing much more frequently than individual particles. Becker explains that this preserves both locality and objective reality by making collapse happen randomly rather than through nonlocal measurement interactions. Individual particles might remain in superposition for billions of years, but macroscopic objects that contain countless particles resolve into definite states almost instantly as random events accumulate.
According to Becker, this approach dissolves the measurement problem by eliminating the need for special measurement processes—collapse happens naturally through the theory’s modified dynamics. Schrödinger’s cat wouldn’t remain in a “both dead and alive” state of superposition for more than a split second because random wave function collapse would quickly force a definite outcome.
| Why “Fixing” Quantum Mechanics by Adding Randomness Might Not Work As Becker explains, spontaneous collapse theories make wave function collapse a natural process, but experiments have dealt blows to these theories. The problem is that if spontaneous collapse really occurs, the random collapse process should cause charged particles to constantly jiggle around, emitting detectable X-ray radiation. But ultra-sensitive detectors in underground laboratories designed for neutrino research have found no evidence of this. The irony is that these theories were designed to eliminate quantum mechanics’ weird aspects, but they do so by adding fundamental randomness to the universe’s basic laws, showing that sometimes the “cleanest” theoretical solution creates more problems than it solves. |
Exercise: What’s Real in Quantum Physics?
Becker explains that quantum mechanics works perfectly well at predicting the behavior of microscopic particles, but it seems to describe an impossible reality in which particles exist in multiple states simultaneously. This forces us to choose between fundamentally different views of what exists and how science should understand the world. The main approaches offer radically different pictures of reality:
Many-worlds: Every possible outcome actually happens, just in different parallel universes we can’t see.
Pilot-wave theory: Particles always have definite locations, but invisible “pilot waves” guide them and connect distant particles instantly.
Spontaneous collapse: Wave functions randomly “choose” definite outcomes on their own, with big objects choosing much faster than tiny particles.
- Which approach to quantum reality seems most reasonable to you? What makes it more appealing than the alternatives?
- Your chosen interpretation requires accepting something strange about the world—parallel universes, invisible faster-than-light connections, or fundamental randomness. Which of these seems least troubling to you, and why?
Learn More
To learn more about the broader issues surrounding quantum wave function collapse, read Shortform’s guide to What Is Real? by Adam Becker.
