The Collapse of the Wave Function: What Makes Something “Real” in Quantum Physics?

Cristiano França Ferreira
Aug 23
3 min read

The Collapse of the Wave Function: What Makes Something “Real” in Quantum Physics?

In classical mechanics, objects have well-defined properties: a ball has a position, velocity, and color. But in the quantum world, a particle doesn't have a fixed reality until it's observed . It exists as a superposition of possibilities—and only at the moment of measurement does one of those possibilities become real .

This phenomenon, known as wave function collapse , is one of the greatest mysteries in physics. It raises a fundamental question: what causes one of several possibilities to manifest?

The Wave Function: A World of Probabilities

In quantum mechanics, the state of a particle is described by a wave function , usually represented by the Greek letter Ψ (psi). This function is not a physical thing , but a mathematical description of the probabilities of where the particle might be and what values its properties (such as momentum, spin, and energy) might assume.

Until a measurement is made, this function evolves continuously and predictably, following Schrödinger's equation . But the instant we make a measurement, the wave function "collapses"—that is, all possibilities disappear, leaving only a single observed outcome.

Before measurement: the particle is in all possible states. After measurement: it is in only one.

The Measurement Problem

This “jump” between the probabilistic world and observed reality is known as the quantum measurement problem .

The central questions are:

What defines the moment of collapse?
Does the observer's consciousness play a role in this?
Is there an objective reality before measurement?

These questions have no consensual answer - and therefore have given rise to different interpretations of quantum mechanics .

Main Interpretations

1. Copenhagen Interpretation (Bohr and Heisenberg)

Collapse occurs at the time of measurement .
The system has no real properties prior to observation.
Reality is probabilistic and contextual .

2. The Many Worlds Interpretation (Everett, 1957)

There is no collapse: all possibilities are realized , but in different parallel universes .
The observer splits into multiple versions, each experiencing one of the possible outcomes.

3. Objective Collapse (GRW, Penrose)

Collapse is a real, spontaneous physical process , independent of measurement or consciousness.
There is a limit where superposition ceases to exist, for reasons not yet fully understood.

4. Theories of Consciousness (Von Neumann, Wigner)

The observer's consciousness would play an active role in the collapse, making one of many possible states real.
Although controversial, this idea has influenced both science and philosophy of mind.

A Curiosity: The Collapse of the Wave Function in Everyday Life?

Although the collapse is a microscopic phenomenon, we constantly experience symbolic reflections of it .

Example: Imagine you submit your resume for a job opening. Until you receive a response, all possibilities exist : approval, rejection, or rejection. Reality only becomes clear at the moment of "assessment"—when the email arrives.

Of course, this isn't quantum collapse, but the narrative structure from uncertainty to revelation is very similar. And perhaps that's why this concept has such appeal outside of physics.

Philosophical Implications

The collapse of the wave function breaks with the idea of an absolute reality, independent of observation . It forces us to admit that the interaction between subject and object is an essential part of the quantum universe .

As Werner Heisenberg wrote:

"What we observe is not nature itself, but nature exposed to our way of questioning."

Modern physics, in this sense, does not simply describe “what is,” but what can be—and what reveals itself when we interact.

Technological Applications

Understanding the collapse is critical to:

Quantum computing , which relies on quantum coherence and careful manipulation of states before collapse,
Ultra-high-precision sensors that take advantage of the behavior of particles in superposition,
Cryptographic systems , which are based on the destruction of information when trying to measure it.

Final Reflection: Are We Part of the Equation?

The collapse of the wave function challenges a long-held idea in science: that we are neutral observers of the world . Quantum physics suggests that reality is not "out there," ready-made and independent, but entangled with the way we look at it .