Classical mechanics couldn’t explain how an electron could orbit an atom without crashing into the nucleus, due to electromagnetic radiation predicted by Maxwell’s classical equations. Niels Bohr addressed this by theorizing that electrons exist in quantized orbits, not radiating energy.

Louis de Broglie showed that if quantized orbits exist, electrons must be waves. Experiments confirmed that not only electrons but all quantum particles, like photons and atoms, exhibit wave-like interference, implying they are waves too.

Erwin Schrödinger developed an equation explaining this wave behavior. His equation describes how a wave evolves over time. But when detecting quantum objects, they appear as particles, not waves. This confusion is evident in experiments like the double-slit experiment.

Max Born proposed interpreting the Schrödinger wave as a probability wave. This allows quantum objects to be described as waves, with a probability of being located at any point, determined only upon measurement.

Here’s what makes quantum mechanics fascinating: unlike classical mechanics, quantum objects like electrons, photons, and atoms don’t behave like tiny basketballs. Instead, their wave-like behavior forms interference patterns, as seen in experiments.

Even though we have a mathematical model in Schrödinger’s equation, detecting these objects always shows particle-like behavior. To reconcile this, the concept of measurement was introduced. When a measurement is made, the wave collapses, localizing into what we interpret as a particle. This wave collapse through measurement, known as the measurement problem, lacks a clear explanation.

Despite this, not solving the measurement problem hasn’t hindered the predictive power of quantum mechanics. A philosophy called “shut up and calculate” suggests that the accuracy of equations is what matters most, not understanding the underlying mechanisms too deeply. However, many scientists believe that explaining the universe’s inner workings is essential.

In quantum mechanics, objects behave as waves. Their wave functions aren’t localized but spread across all space, forming probability waves. The Uncertainty Principle emphasizes that we can’t simultaneously know both a particle’s position and momentum.

For example, a perfect sine wave for an electron implies an undefined position, but defined momentum. To know the electron’s position precisely, we need waves of different wavelengths, creating uncertainty in momentum.

This isn’t a limitation of our measuring tools; it’s intrinsic to the universe. Even larger objects like tennis balls propagate as waves, but their wavelengths are minuscule, making their quantum properties undetectable.

Wave-like behavior also leads to phenomena like non-locality and entanglement, where particles exhibit correlations without real-time communication, a concept Einstein found puzzling.

Quantum mechanics also redefines atomic structure. Instead of electrons in circular orbits, envision a probability cloud around the nucleus. The universe is quantized, meaning energy, momentum, charge, mass, and even time and space occur in discrete units. An electron moving between energy states doesn’t pass through intermediate states but jumps directly. This quantization isn’t directly observable because the intervals are too small.

Ultimately, quantum mechanics is fundamental. Classical mechanics works at macro scales but is an approximation of the deeper quantum reality. Understanding this offers a glimpse into the core of our universe’s behavior.