It is relatively common to understand what mass is not. It is not a size that can be measured, poured into a container or weighed. It seems that it can be measured only in relative terms, the relationship of the effect of the impact of one atom on another. We have identified the number of protons and neutrons in specific atoms and that number determines its relative mass in relation to other atoms.
That measure of mass which is the relationship of the impact of one atom on another is the same as the measure of inertia. Is mass a reality or is inertia the entire reality?. It is always dangerous to impute more to a definition than may be justified.
We see the relative inertia in the splat of an automobile into a concrete barrier or the fuel consumption in going from 0 to 60 miles an hour in a heavy automobile. We have used lead projectiles for centuries for greater inertial stability and currently use even heavier (greater mass) depleted uranium for more effective penetration of armament.
Is that all there is to inertia? Fortunately there are many more subtle effects. The many more subtle effects of inertia rely not on the cost of acceleration or the effect of deceleration but on the stability of motion imparted by inertia . The orbits of the planets are not determined by gravity alone but by the interaction of inertia and gravity. The skipping of a flat stone on a pond is caused by the relationship of the effect of gravity on the stone and the inertia of the water molecules it contacts as it zips along. The first contact will create a slight depression and the stone will be propelled into the air as it climbs over the perimeter ridge. When second year university students still believe heavier than air flight is possible from the lift created above the wing by its curvature it is time to examine the situation. Someone long ago got scientific recognition for proclaiming that when a gas passes around an obstacle a lower pressure is created on the surface of the trailing edge. Is that because the gas in going around the obstacle has further to travel. Absolute nonsense!! Inertia tells us that an object will deflect a moving molecule. We are also aware that a gas (air) is very elastic. Air is deflected both up and down by the leading edge of the wing at an energy cost from the thrust of the engines. The design of the leading edge of the wing deflects the air more violently upward. The combined effects of inertia and the elasticity of a gas result in the air reversing direction relatively slowly and resulting in a lowered pressure on the trailing upper portion of the wing. Nevertheless the greater lift is provided by the inertia of the many air molecules contacted by the under surface of the wing. That is why aircraft must move FAST. Aircraft can fly upside down as long as they move. Inertia and speed are the key. An equivalent mass of air molecules are accelerated downward while the aircraft is supported or lifted.
The relative inertia of a mass (our earth) provide the stability and consistency of orbit and plane of rotation that permit us to forecast the night and the day and the seasons. There are external forces that affect that cycle but they are generally proportionally small.
The period of rotation and orbit, in addition to providing our measure of time for the day, the seasons and the year, on the much smaller scale of the orbiting electron is used to measure the most minute period.
Equally important to the period of orbit is the stability of plane of orbit. Just as the period of orbit can be anticipated the plane of orbit will be consistent unless affected by an external force. By being aware of the extent of external forces we can anticipate quite accurately where a celestial body will pass.
The effects of the stability of the plane of orbit are not limited to the huge masses of the planets but are equally important in the minute world of the electron. As previously indicated, in our world the electron orbits the nucleus of the atom. The law of inertia applies in the same way. The plane and period of orbit will be constant unless affected by external forces. The number of external forces are as numerous as the electrons of the universe. Fortunately to a great extent their effect is synchronized and also dissipated with distance and we can control and anticipate results by application of various external forces. That is what electricity is all about. We can accomplish many tasks with the movement of electrons if we acknowledge the effect of inertia on the flow of electrons and understand the potential for control inherent in inertia to determine the movement of electrons. Conductivity, resistance, semi-conductivity are all dependent on inertia and the consistency of orbit of electrons.
Where the planes of orbit of electrons of adjacent atoms are not aligned a great deal of push is required to cause them to move. The amount of push required and heat (distortion of electron orbit) will be proportional to the misalignment of the planes of orbit.