## Matter and Substance

##### Reference: A Logical Approach to Theoretical Physics

There are atomic and non-atomic substances (see Emptiness, Void and Space). Matter is atomic substance. Light is a non-atomic substance.

Matter puts resistance to being pushed. That is how matter is detected. If there is no resistance, we can neither push matter nor detect it. Therefore, matter is defined by its resistance to push. Newton defined this property as innate force of matter, or “inertia”. The property of inertia makes matter substantial. That is why matter is also called “substance”.

We can detect light through our sense of vision. Light, therefore, is substantial because it interacts with our eyes. Its innate force, however, is very small compared to the inertia of matter.

Matter is atomic substance. Light is a non-atomic substance.

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## Mass and Energy

Matter has mass, but light is considered to have no mass. Science looks at light as radiant energy.

Matter has mass because it has an atomic structure with a nucleus. This structure greatly adds to the innate force of matter because of its rigidity. Therefore, mass is associated with matter and its inertia. Light has no mass because it has no rigid structure. It radiates out like a wave with a wavelength. It has kinetic energy.

Newtonian concepts of momentum and energy are defined for matter using mass in the mathematical equations. Momentum refers to the amount of motion there is, such as, in a moving log. Energy is the work done in stopping that moving log. When two billiard balls collide, their motion changes, and work is done in changing that motion. Change in momentum and energy are manifested only when there is force acting through contact.

Momentum and energy exist for light too. Since light has no mass, mathematics assumes some substance (innate force) for light without expressing it. That substance may be estimated for light from Einstein’s equation, E = mc2.

Light is an extremely fast moving, unstructured, wave-like substance.

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## Substance and Density

The density of matter depends on how densely the atoms are packed within a body. But even then, this density is averaged over the atom in which the heavy nucleus exists as a tiny speck.

The highest density of substance exists in the nucleus of an atom. The density decreases sharply farther away from the nucleus in the electronic region. The electron is 1840 times lighter than a neutron, and its volume is much larger. A photon is still much lighter, and greater in volume compared to the electron.

One may say that “pure substance” is becoming “diluted” from neutron/proton to electron to photon, and its density is decreasing. The density of photon may be estimated by its wavelength.

Light as a substance has minimum density.

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## Past Views of Light

In Newton’s time, the recognized substance was matter. He saw light as made up of particles (corpuscular theory) but these particles did not follow the laws of mechanics like matter particles did. Therefore, he did not associate inertia or innate force with them.

Einstein also viewed light to be made up of particles, which he called light quanta. He implied these particles to be packets of energy that had discrete existence in space. These particles carried enough momentum to expel electrons from the surface of certain metals. Still Einstein did not call out light as a substance with density and innate force.

In the past light has not been viewed as a dynamic substance with density and innate force.

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