Many people, who vaguely remember their school physics classes, would have some trouble differentiating between "mass" and "matter". Modern physics, however, is beginning to show that these two words really refer to two different physical manifestations. All matter that we can perceive on earth, and all the billions of stars and galaxies that we can observe in the sky, altogether make up less than 5% of the contents of the universe. More than 95% consists of what is called "dark matter" and "dark energy", that is to say matter and energy that is invisible.
This dark matter can be detected only by its gravitational pull on visible matter. "Visible" matter includes not only what we see in nature around us, but also the gases that we do not see directly. All this matter is atomic in structure, with almost all its mass in the atomic nucleus, that is in its protons and neutrons. These two particles, plus some short-lived particles, are called baryons as a group. Each of them consists of three quarks.
What the invisible dark matter consists of is unknown. Physicists, however, are reasonably certain that by far the greater proportion of it must consist of non-baryonic particles, that is of matter which does not have an atomic structure. Speculation centers around the concept of a gas of weakly interacting massive particles, or WIMPS. These particles are purely hypothetical at the moment. If they are ever discovered, the presently used Standard Model of particle physics would have to be extended to include them.
So it seems that "dark matter" has mass, because it exerts gravitational pull, but not what we commonly call matter, which has an atomic structure. This atomic matter, which not too long ago was thought to represent the entire structure of the universe, is now found to be a somewhat rare (less than 5% of the total) combination of mass and forces which work together to form an atom, that is the basic building block of all matter. The forces involved here are primarily the strong nuclear force, which holds the quarks together in the protons and neutrons, and also holds the protons and neutrons together in the nucleus of the atom.
The other force involved in this unique combination of mass and force that constitutes the atom is the electromagnetic force, which interacts with electrically charged particles, like the electron and the proton. The electromagnetic attraction between negatively charged electrons and positively charged protons in the nucleus causes the electrons to orbit the nucleus of the atom.
As all solids, liquids and gases of our world are made up of an atomic structure, it might be easier to call all these "matter". Everything below the atomic horizon, particles such as protons, neutrons and quarks, could then be thought of as consisting of "mass" There are also force particles which carry mass, like the W and Z bosons. When it comes to "dark matter", of course, something is involved which is different again. Not only in this dark matter thought to have no atomic structure, but it is also thought to consist largely of WIMPS, that is non-baryonic particles, or particles which do not include the ordinary subatomic protons and neutrons.
It is tempting, however, to use the term "matter" only for atomic matter and the term"mass" for everything else on which gravity exerts an influence. When we know what "dark matter" actually consists of, it might be necessary at some stage to divide the concept of mass yet further.
This conceptual difference between matter and mass is confirmed to some extent by the latest work in quantum mechanics, which otherwise has been rattling our conceptual cages in a most disquieting manner for years. It should be emphasized that quantum theory is unbelievably successful. Every prediction it has ever made has been proved by experiment and observation. Its mathematics has refined and corrected Newtonian laws.
It is the bedrock of modern physics. Yet it also states (and has shown experimentally) that a body can exist simultaneously in two or more places; it also avers that observation not only marks an object but actually brings it into being: before the observation, there was no object. Furthermore, under certain conditions, the result of an action can be transmitted instantaneously to another place, no matter how far away.
These weirdnesses in quantum mechanics will be dealt with separately in another article. They servce as a reminder that matter is much more mysterious than anyone imagined during the era of classical Newtonian physics, when the atom was thought to be the ultimate, indivisible little bit of ordinary matter. What is of interest here is that quantum mechanics realizes that, for all practical purposes, large bodies can be dealt with according to the laws of classical physics.
As these bodies get smaller and smaller, down to molecules and then atoms, the weird effects increase, because such particles can easily be put into a wave form, which is the necessary preliminary to being in a "superposition state", where such a particle can exist in two places at the same time.
Down to and including the atom, however, matter particles are still well defined in space. With a modern scanning tunneling microscope (STM), we can not only see individual atoms, but we can pick them up and move them around. The situation gets much more difficult with subatomic particles, which Heisenberg called "potentialities" or "probabilities", rather than well-defined realities.
At the beginning of the modern age of physics, in the 1920s, when it became obvious that subatomic particles were not simply very small bits of matter, Bertrand Russell grumped in his Outline of Philosophy that, "For ought we know an atom may consist entirely of the radiations that come out of it. It is useless to argue that radiations cannot come out of nothing .... The idea that there is a little hard lump there which is the electron or the proton, is an illegitimate intrusion of commonsense notions derived from touch." It was a hard time for scientific thinkers to make the jump from classical Newtonian physics to the modern age.
Today, the results of quantum experiments leave no doubt that what we call matter exists simultaneously in two states, one in wave form (where it can be in two places at once) and the other in particle form, where it can exist in only one place at a time. It is entirely our decision in which state we want to investigate a body.
What this article suggests is that both mass and force are "dark" or invisible manifestations by themselves. Hence, what we call "dark matter" and "dark energy". The primal energy (to give it a name) which was exploded in the Big Bang and from which the universe originated, is thought by modern physics to have passed through something called the Higgs Field, from which it emerged at different levels of energy.
First to emerge, at very high energy levels, were the force of gravity and the strong nuclear force. Below that came the electromagnetic force and the weak nuclear force and still further down the energy scale came the mass particles. A small portion of these mass and force particles then combined to form the atomic structure of matter, which we can perceive through our senses. Apart from that, only light (as it emerged from the Higgs Field) could have been perceived by our senses, as part of the radio wave spectrum.
Such is the general framework around the origins of mass, matter and force which modern physics is looking at today. How it all fits together, and whether these ideas will stand the test of time, is something only the future can decide.