Matter is commonly defined as anything that has mass and occupies space. Everyday objects, from a car to the air we breathe, fit this description, being composed of atoms and subatomic particles. However, the universe contains many phenomena that do not conform to this definition. These non-matter entities play a significant role in how the universe functions.
Energy
Energy represents the capacity to do work, causing a change or exerting a force over a distance. Unlike matter, energy possesses no mass and does not occupy volume. While matter can contain energy, and energy can be converted into matter and vice versa, they are distinct concepts.
Light
Light, a form of electromagnetic radiation, exemplifies energy that is not matter. It consists of photons, which have no rest mass and cannot be brought to a halt. Photons must be massless because anything with mass would require infinite energy to reach the speed of light. Light does not occupy space; multiple light beams can cross through the same point without interfering.
Heat
Heat, or thermal energy, is another form of energy, not matter. It arises from the kinetic energy of particles within a substance, reflecting their random motion. Heat cannot be physically contained or weighed, distinguishing it from matter. While heat can be transferred between objects, it is a manifestation of energy, not a substance with mass or volume.
Sound
Sound is a form of mechanical wave energy, which travels through a medium by vibrating its particles. Sound waves do not possess mass or occupy space; instead, they represent oscillations or pressure variations in matter. For instance, sound travels through air because air molecules vibrate and bounce off each other, transmitting the energy, but the sound itself is not the air molecules. Sound requires a medium to propagate and cannot travel through a vacuum.
Forces and Fields
Forces are interactions that can cause changes in the motion or shape of an object. They are not physical objects with mass or volume, but rather pushes or pulls that affect matter. For example, gravity pulls objects with mass towards each other, but gravity itself is not a physical substance.
Electromagnetism, the strong nuclear force, and the weak nuclear force are other fundamental forces. These forces mediate interactions between particles, influencing their behavior without being composed of matter themselves. A force always has both magnitude and direction, making it a vector quantity, which describes its effect rather than its physical composition.
Fields
Fields are regions where a force can exert its influence. A field assigns a physical quantity, such as a number or a vector, to every point in space and time. Gravitational fields, for example, are regions around objects with mass where other masses experience a gravitational force. Similarly, electric and magnetic fields surround charged particles or magnets, influencing other charges or magnetic materials.
Fields are not made of particles with mass, and they do not possess weight. Fields are conceptual frameworks used to describe how forces are transmitted and interact across space, often visualized as extending throughout a large region and affecting everything within their vicinity.
Abstract Concepts and Information
Beyond physical phenomena like energy and forces, abstract concepts exist that are not matter. These include thoughts, ideas, emotions, numbers, and mathematical principles. Such concepts are products of consciousness or constructs of the mind; they do not possess mass or occupy physical space. For instance, the idea of ‘justice’ or the number ‘five’ are real in their conceptual meaning but are not tangible objects.
Information itself also falls into this category of non-matter. While information can be stored or encoded within matter, such as data on a computer hard drive or thoughts represented by neural activity, the information content itself is not material. The physical medium has mass and occupies space, but the patterns, data, or concepts they represent do not.
Information is often considered a fundamental aspect of the universe. While some theories propose it as a basic element alongside matter and energy, it is typically understood as an organizational property or a pattern, rather than a substance with physical mass or volume. The abstract nature of information means it can be communicated, processed, and even lost, but it does not have the tangible properties of matter.