The concept of matter represents the fundamental substance that makes up the physical universe. It is the underlying “stuff” from which all tangible objects, from the smallest atom to the largest galaxy, are constructed. To fully grasp what matter is, it is often helpful to explore the things that are frequently mistaken for it but ultimately fall short of its scientific definition. By examining non-examples, we can clarify the precise boundaries that distinguish physical substance from other phenomena in nature.
The Criteria for Defining Matter
In science, matter is precisely defined by two non-negotiable physical properties: it must possess mass and it must occupy space, a property known as volume. For something to be classified as matter, it must satisfy both of these criteria simultaneously.
Mass is a measure of the amount of substance within an object and, more accurately, its resistance to a change in motion, or inertia. This property is inherent to the object and remains constant regardless of its location. Volume is a measure of the three-dimensional space that an object or substance fills. It is the capacity for an object to occupy a distinct region that excludes other matter.
The requirement of both mass and volume means that matter has a tangible presence that can be both weighed and contained.
Non-Examples Related to Energy and Fields
Many physical phenomena fail the test for matter because they are forms of energy or forces, not substances. Light, for example, is a form of electromagnetic radiation composed of particles called photons. These photons possess momentum and transfer energy, but they fundamentally lack rest mass and they do not occupy a fixed volume. Because light can travel through a vacuum, it does not require a medium of matter for its propagation.
Heat is another non-example, representing the transfer or flow of thermal energy between substances, not a substance itself. This energy is the result of the kinetic energy of the constituent particles of matter, such as atoms and molecules vibrating and moving. While matter is necessary to hold or generate heat, the thermal energy itself has no mass and cannot be contained in a volume.
Sound waves are also not considered matter, as they are mechanical vibrations that propagate through a medium like air or water. Sound is the transfer of kinetic energy caused by the compression and rarefaction of matter particles. While the air molecules transmitting the sound are matter, the wave of energy traveling through them is not.
Electromagnetic fields, such as those responsible for magnetism, are also non-examples of matter. These fields are regions of space where a force is exerted, meaning they represent a form of energy and interaction. A magnetic field can influence matter, but it does not possess mass or occupy space itself.
Non-Examples Related to Abstract Concepts and Information
Entities that are purely conceptual or abstract also cannot be classified as matter because they lack any physical presence. A thought or an emotion, for instance, is a complex electrochemical process occurring within the brain, which is matter. However, the concept of the thought itself—such as the idea of “justice” or the feeling of “joy”—is immaterial. These concepts are mental constructs and descriptions, not physical substances.
Time is another non-example, as it is a dimension used to measure the sequence of events and the duration between them. Time is not a physical substance that can be collected, weighed, or given a volume. It is a measurement tool, not an object.
Information and data, though they must be stored on matter like a hard drive or a piece of paper, are abstract concepts. A digital photograph stored as binary code, for example, represents a pattern of information that is massless and volumeless in its conceptual form. The concept of the number two, or a mathematical equation, also exists outside of the physical world. These are conceptual tools and logical relationships that have no mass or volume.