Subatomic Particle - Particles

Particles

In particle physics, the conceptual idea of a particle is one of several concepts inherited from classical physics. This describes the world we experience, used (for example) to describe how matter and energy behave at the molecular scales of quantum mechanics. For physicists, the word "particle" means something rather different from the common sense of the term, reflecting the modern understanding of how particles behave at the quantum scale in ways that differ radically from what everyday experience would lead us to expect.

The idea of a particle underwent serious rethinking in light of experiments that showed that light could behave like a stream of particles (called photons) as well as exhibit wave-like properties. These results necessitated the new concept of wave-particle duality to reflect that quantum-scale "particles" are understood to behave in a way resembling both particles and waves. Another new concept, the uncertainty principle, concluded that analyzing particles at these scales would require a statistical approach. In more recent times, wave-particle duality has been shown to apply not only to photons but to increasingly massive particles.

All of these factors ultimately combined to replace the notion of discrete "particles" with the concept of "wave-packets" of uncertain boundaries, whose properties are known only as probabilities, and whose interactions with other "particles" remain largely a mystery, even 80 years after the establishment of quantum mechanics.