Quantum mechanics describes nature with extraordinary accuracy, yet its behavior remains difficult to reconcile with everyday experience. Physicist Richard Feynman famously argued that nobody really understands quantum mechanics. The problem is not that physicists cannot predict quantum behavior. Rather, human intuition, developed through interactions with large objects, struggles to picture what happens at atomic and subatomic scales, tells Wired.com (full article available to subscribers).
The double-slit experiment illustrates this problem. When ordinary objects such as tennis balls pass through two openings, they produce two groups behind the slits. Electrons behave differently. Although they are particles with mass, electrons passing through two tiny slits create an interference pattern resembling waves.
The result becomes stranger when electrons are fired individually. Over time, they still produce the interference pattern, suggesting that each electron effectively interferes with itself. Quantum mechanics describes the electron as existing in a superposition of possible states rather than simply traveling through one slit or the other.
Measurement changes the situation. When scientists use a detector to determine which slit an electron passes through, the interference pattern disappears. The electron behaves like a particle following a definite path. This process is commonly described as the collapse of the wave function.
Schrödinger’s famous cat thought experiment attempted to expose the apparent absurdity of applying superposition to everyday objects. Yet subsequent experiments have established superposition as a genuine feature of quantum systems. It is also fundamental to the potential parallel-processing capabilities of quantum computers.
Other quantum phenomena, including entanglement, further challenge familiar ideas about physical reality. Measuring one entangled particle is correlated with the state of another even when they are widely separated.
The deeper lesson is that common sense may simply be unsuitable for describing nature at its most fundamental level. Quantum mechanics therefore demands not an intuitive picture of reality, but acceptance that experimentally verified physical behavior can extend beyond everyday human experience.
