Particle

Particles can also be used to create scientific models of even larger objects depending on their density, such as humans moving in a crowd or celestial bodies in motion.

The concept of particles is especially useful when modelling nature, as the full treatment of many phenomena can be complex and also involve difficult computation.

Francis Sears and Mark Zemansky, in University Physics, give the example of calculating the landing location and speed of a baseball thrown in the air.

They gradually strip the baseball of most of its properties, by first idealizing it as a rigid smooth sphere, then by neglecting rotation, buoyancy and friction, ultimately reducing the problem to the ballistics of a classical point particle.

Examples of macroscopic particles would include powder, dust, sand, pieces of debris during a car accident, or even objects as big as the stars of a galaxy.

Because of their extremely small size, the study of microscopic and subatomic particles falls in the realm of quantum mechanics.

[17] According to our current understanding of the world, only a very small number of these exist, such as leptons, quarks, and gluons.

The lifetime of stable particles can be either infinite or large enough to hinder attempts to observe such decays.

Particles may also be suspended in the form of atmospheric particulate matter, which may constitute air pollution.

Arc welders need to protect themselves from welding sparks , which are heated metal particles that fly off the welding surface.
Particles are often represented as dots. This figure could represent the movement of atoms in a gas , people in crowds or stars in the night sky .
Galaxies are so large that stars can be considered particles relative to them.
A proton is composed of three quarks and held together with the strong interaction .
Examples of a stable and of an unstable colloidal dispersion.