Michael Faraday's Electromagnetic Force Field, Particle/Field Duality (1832)
This field concept replaced Newton's instant action-at-a-distance between discrete particles. Importantly, the electromagnetic (e-m) field is a vector (directional) quantity that defines force anddirection of acceleration of many charged particles upon one another. It is continuous in the sense that the distance and force between particles can vary by infinitely small amounts.
For example, electrons near one another in Space experience a mutual force of repulsion and this behaviour can be mathematically described using Faraday's e-m field which quantifies this force and describes how it varies with distance and direction. As Albert Einstein explains;
He conceived these fields as states of mechanical stress in an elastically distended body (ether/space). For at that time this was the only way one could conceive of states that were apparently continuously distributed in space. The peculiar type of mechanical interpretation of these fields remained in the background - a sort of placation of the scientific conscience in view of the mechanical (Newtonian) tradition of Faraday's time. (Albert Einstein, 1940)
Once we understand the Spherical Wave Structure of Matter in Space though, then we no longer need these mathematical ideas, instead we realise that Space itself is a continuous wave medium (which necessarily connects all things) and there are no such things as discrete particles.
James Clerk Maxwell's EquationsWhen Maxwell (1876) used this field theory to assume that light was an Electromagnetic Wave, and then correctly deduced the finite velocity of light, it was a powerful logical argument for the existence of the electromagnetic force field, and that light was a wave like change in the field (electromagnetic radiation) that propagated with the velocity of light c through the ether.
The Finite Velocity of Light Waves (1876)
In fact Maxwell was simply confirming that all Wave-Center to Wave-Center (particle) interactions are not instantaneous as Newton assumed, but are limited by the velocity of the In-Waves which is the Velocity of Light c.
So while Maxwell misunderstood the true nature of the waves (which are physical waves in Space rather than mathematical vector e-m waves), he is largely correct. This new knowledge was significant as it established the importance of the finite velocity of light c and further enhanced the field theory, thus rejecting Newton's theory of particles and instant action-at-a-distance.
Only after Hertz (1888) had demonstrated experimentally the existence of Maxwell's electromagnetic waves did resistance to the new theory break down. And what was true for electrical action could not be denied for gravitation. Everywhere Newton's (instant) actions-at-a-distance gave way to fields spreading with finite velocity.
At that thrilling moment he surely never guessed that the riddling nature of light, apparently so completely solved, would continue to baffle succeeding generations. (Albert Einstein, 1954)
Thus when Max Planck (1900) discovered that there are only certain allowed discrete energy states for electrons in molecules and atoms, and that light is only ever emitted and absorbed by electrons in discrete amounts or 'quanta', contrary to Maxwell's formulation that light is a continuous electromagnetic wave, then this caused a fundamental problem for the field theory that was never resolved. It is only now, with knowledge of the true foundations of physics and reality, that we can understand, and thus anticipate and correct, the errors of contemporary modern physics.