Quantum Uncertainty Explained

Demystifying the science of quantum physics

TL;DR

In quantum physics, certain pairs of properties cannot be precisely known at the same time.

In classical physics, everything is deterministic, and measurement limits are primarily technological. In quantum mechanics, however, there’s a fundamental limit — knowing one property more precisely makes another property less certain. This principle reflects the intrinsic randomness at the heart of quantum theory rather than just a gap in our measurement tools.

How did this all come about?

Let’s first recall the historical development and the core ideas behind quantum uncertainty.

1. Old Quantum Theory (Early 1900s)

Classically, if the positions and momenta of all particles are known, one can predict future states indefinitely Such “one” — dubbed Laplace’s demon — is guaranteed this through Newton’s laws that stood for centuries.

But, by the early 20th century, scientists like Max Planck, Albert Einstein, and Niels Bohr had already shown that energy and light come in discrete chunks — a significant departure from classical theory. The theory revolved around a new constant of Nature, ℏ, now called Planck’s constant.

The notion that particles themselves might not have definite classical properties (like position or momentum) at all times was suggested bu Lious de Broglie when he introduced that all things — light and particles — possess wave properties.

All the facts until 1925 comprised “old quantum theory” — a hodgepodge of classical ideas applied to quantum corrections derived from guesswork.

2. Heisenberg’s Matrix Mechanics (1925)

In an attempt to provide some underlying principles to quantum theory, Werner Heisenberg introduced a formulation of quantum theory using non-commuting quantities to represent physical observables. This was a radical shift from classical concepts, emphasizing discrete mathematics and new rules for calculation.