actually all particles are basically energy in the sense that they were created by adding energy to a quantum field. This applies whether you're creating a photon, an electron, a quark or whatever.
So in creating a photon we added energy to its quantum field.
If energy is not even a photon, so how can we view energy? Is there any physical view to it?
Answer
If energy is not even a photon, so how can we view energy? Is there any physical view to it?
Man is a thinking animal and observes his/her environment, a pattern recognition program is built in our thought structure.
When man started classifying nature, the first observation was that there were two sets:
a) Objects and b) the behavior of those objects classified in attributes: large, heavy, moving fast etc.. in the primitive level.
At present time we have explored the microcosm to the point where the "objects" we measure are fundamental particles as given in the standard model of particle physics. This is a quantum mechanical framework. In this framework "energy" is an attribute that particles carry, together with their mass and their quantum numbers that distinguish them from each other.
Energy is an attribute for elementary particles as an electron, a neutrino , a photon. Elementary means that they cannot be split further so , in contrast to complex particles which may decay to lower mass constituents according to special relativity rules.
Quantum mechanics is a mathematical theory that describes the microcosm of particles with accuracy and has allowed us to build the technological world we live in, including this computer we are communicating with. The mathematics of Quantum Mechanics can be separated into "first quantization", Schroedinger equation etc, and "second quantization", Quantum Field Theories, QFT. The quote from John Rennie's answer comes from the second quantization tool box. Second quantization cannot be understood without going through a course of first quantization.
So in creating a photon we added energy to its quantum field.
The interaction that created a photon gives it its energy; for example bremsstrahlung the radiation of a photon by an electron interacting with an atomic electric field, the photon takes the energy from the electron, which , by conservation of energy has less.
Bremsstrahlung produced by a high-energy electron deflected in the electric field of an atomic nucleus
The energy of the electron is the kinetic energy $1/2mv^2$, and its momentum is $mv,$ making up the four momentum vector of the electron
$$\mathbf p= \begin{bmatrix}E\\ p_xc\\p_yc\\p_zc\end{bmatrix} = \begin{bmatrix}E\\ \mathbf{p} c\end{bmatrix}$$
After the interaction the photon takes away energy and momentum from the electron, described by its own four vector.
[In the second quantization mathematical formalism this interaction is creating a photon with energy $h\nu$ by acting on a photon field at the point of interaction, and this photon propagates with consecutive annihilation and creation operators on the photon field obeying energy and momentum conservation].
If energy is not even a photon, so how can we view energy? Is there any physical view to it?
Energy and momentum are an attribute, describe the behavior and condition , of a particle. By the very definition of energy it cannot be a particle.
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