Definition of Matter

by Ron Kurtus (revised 24 March 2016)

Matter is defined as anything that takes up space and has mass. Everything around you is made up of matter. Matter is a generic term for the "stuff" around you.

Taking up space means that an object has a measurable size or volume. Mass is a property of matter that is a measure of its resistance to acceleration. Another property of matter is that has a gravitational force, such that objects attract each other with a weak force.

There are also variations of matter, such as antimatter and dark matter.

Questions you may have include:

• How does matter take up space?
• What is mass?
• What are the variations of matter?

Matter takes up space

Particles of matter have size and take up space. At the very least, all matter has three dimensions: length, width and height. This is somewhat obvious when you look at various objects around you. They all take up space.

Note: There are theories that matter may consist of many more than three dimensions. Since we consist of matter, and we are also 3-dimensional objects, we cannot experience or measure other dimensions except through mathematical theories.

Measurements have been made of the diameter of various atoms and the space they take up. It is assumed that the various subatomic particles also have a physical size and take up space.

Matter has mass

When an object is accelerated, its inertia resists that acceleration according to the mass of the object. Thus, mass is a property of matter that indicates its resistance to acceleration.

Objects or quantities of matter will attract each other through a gravitation force related to the amount of mass in the objects.

Density

The amount of mass per unit volume of an object or material is called its density. That is how much mass is stuffed into a given volume.

Variations of matter

There are types of matter different than the ordinary forms.

Antimatter

Antimatter particles have the same mass as their corresponding subatomic particles, except that they have the opposite electrical charge and sometimes opposite spin.

Common antimatter particles are the positron, anti-proton, and anti-neutron.

The positron has the same mass as an electron, but it has a positive (+) electrical charge instead of a negative (−) charge.

An anti-proton is the same as a proton, except that it has a negative (−) electrical charge instead of a positive (+) charge.

An anti-neutron has a spin component in the opposite direction of a neutron. These particles are still matter.

Dark matter

Another variation of matter, called dark matter, is still a theory. Astronomical measurements indicate that some galaxies have more mass than is observed. The theory is that there exists some sort of "dark matter" that cannot be seen but that has an influence on the gravity of those galaxies.

Summary

Matter is anything that takes up space and has mass. Taking up space means that an object has a measurable volume. Mass indicates how much force is required to move the object. Variations of matter include antimatter and dark matter.