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The following is a bit of a detour, but I better cover it (now) while the possibility of it arising in your brain is dealt with, immediately ... It is not necessary to theorize the anomalous existence of photons to account for the traversal of energy across empty space when space is perfectly capable of acting as a dielectric medium supporting the existence of longitudinal shockwaves. Electromagnetic transverse ripple waves are a short-range ramification of longitudinal shockwaves converting into transverse ripple waves whenever the longitudinal shockwaves meet up with matter at the other end of an empty void of space. Oliver Heaviside effectively acknowledged this, over a century ago, when he devised his Telegrapher Equations to solve the riddle of, "Why was the magnetic field of electricity dying out so rapidly (along the length of the trans-Atlantic telegraph cable) while the electric field did not?" It was because the electric field does not travel since it is the consequence of a dielectric material responding to the imposition of a potential storage of voltage. This dielectric material was the boundary condition initiated by the surface of the copper cable separating the cable from its surrounding space of Atlantic ocean. The insulation of this cable helped facilitate this boundary condition insuring that no current would leak out into the ocean. But the dielectric condition of a transmission cable is at right angles to its transmission while its transmission is parallel to the cable's length. So, ...
The transmission of dielectric charge of potential (voltage) does not have to travel, unlike the magnetization of current which does. Thus, voltage potential does not have to die out while magnetic current must die out along the entire length of a copper cable. Hence, a permalloy ferromagnetic tape had to be wrapped around the bare copper cable before applying a very thick layer of insulation to retain the magnetic field (generated by the application of a difference in voltage potentials upon the terminals at either end of this copper cable) to prevent the loss of the magnetic field surrounding this cable. This prevention of the loss of magnetism is known as: magnetic remanence, or simply: remanence. It was used as a form of computer memory between the years of 1955 and 1975 by creating tiny ferrite rings through which was threaded a pair of criss-crossing copper wires creating a tapestry of horizontally and vertically aligned fine copper wires each of whose intersections was surrounded by a single, magnetizable, ferrite ring which could remember the polarity of its magnetization long after the application of voltage was shut off in the wires which passed through each ring. This polarity of remembrance was interpreted as either a binary "one" or a "zero". And this memory of ferromagnetic material is perpetual. It never dies out unless acted upon by a new force of electricity. This is in keeping with Sir Isaac Newton's dictum, that: "Energy tends to remain in a particular vector of motion unless acted upon by another force." You see, ...
Magnetic energy is a preexisting condition within a ferrite ring. All we do is make use of it by organizing its random polarizations into a collective alignment which we can recognize as possessing a north and a south pole held to be en masse across the entire chunk of this ferromagnetic material. So, the perpetuosity of magnetism is already within the ferrite ring. But it's a chaotic mess until we impart order to it and, thus, put it to work for our benefit. It is this perpetuosity of ferromagnetism within a lengthy strand of permalloy (or similar) tape which made the transmission of current possible across the trans-Atlantic telegraph cable – without which, there would have been no Morse coded message received. It is only short lengths of copper wire which can carry a magnetic charge. Long lengths don't succeed unless ferromagnetic material is located nearby, or else this lengthy copper wire is coiled so that the leakage of one turn of wire leaks out into the next! So, ...
What is the boundary condition of space which makes the longitudinal transmission of dielectricity instantaneously possible? The answer is, ...
The existence of matter at either end of a longitudinal transmission is what makes this transmission possible across empty space. This space acts similar to the behavior of a dielectric material sandwiched between two conductive plates within a capacitor. And the boundary condition of two conductive plates (on either side of a capacitor's dielectric middle layer) respond to the longitudinal transmission across the dielectric material by creating transverse ripples of current. But these ripples of current are short-range dying out very quickly due to the resistance of the conductive material in which they arise unless this material incorporates the use of iron, or a coiled geometry, to help "remember" the magnetic ripple.