Before traipsing off onto supposedly solid ground, and thereby sussing the matter of matter, let’s note the nature of energy – for energy forms the threads from which are woven the fabric of existence.
Energy is an abstract concept introduced by physicists in order to better understand how Nature operates. Since it is an abstract idea, we cannot form a concrete picture of it in our minds, and we find it very difficult to define it in simple terms. ~ American physicist Carlos Calle
Energy is traditionally defined as the relative ability to put matter to work. As matter is transposable energy, that definition is a tautology.
More formally, in physics, energy is a conserved extensive property of a physical system. Parsing that definition for content leaves an irreducible void.
A physical system is a mathematical construct which states that a specified universe has been chosen for analysis. In other words, a physical system is an abstracted arbitrary region, with any external environment, or its influences, ignored.
In examining existence, physicists exclusively focus on the observable 4 dimensions (4D) and studiously ignore extra dimensions (ED), which evidence insists exists. They do so because ED can only be inferred, as its characteristics are beyond empirical analysis (i.e., the scientific method). There is irony in this, in that energy can only be inferred by its effect on matter. In other words, while energy manifests, it does not inherently exist.
In physics, a property is a quantifiable characteristic. It may be intensive or extensive.
Whereas an intensive property does not depend upon system size or content for its value, the size of the system matters for an extensive property. The value of this additive property depends upon the size of the system under description. An example illustrates.
The mass and volume of a body are extensive properties, as they are the measure of proportion within a system. But hardness is intensive, as it is scale-invariant, in being the ratio of mass / volume.
In that energy is an extensive property, the scope of selected system is crucial to the characterization of energy. Wrongly scope the system considered Nature, as physics does, and you get an inaccurate representation.
Conserved means preserved: in this instance, self-contained. The quantity of energy is taken for granted as never changing within the defined system, which is presumed to be isolated (no possible leakage). Virtual particles and other ED weirdness demonstrate that this critical, axiomatic assumption of 4D containment is false for the observable universe.
From its definition, energy is a vacuity, comprising nothing more than a conceptual construct which physics has ill-defined.
Energy cannot be observed directly. It is only a comparative as measured by its effect on matter. In of itself, energy has no presence. Energy is instead only a relative mathematical reference.
What is energy? An abstraction that appears phenomenal through its productions affecting matter.
Energy is more a ‘scientific’ idea than substance. ~ English chemist and molecular biologist Graham Cairns-Smith
In assuming that the cosmos is a 4D closed system, the classic laws of thermodynamics state that energy may neither be created or destroyed. But the universe is not just 4-dimensional, and there is no empirical way of examining the HD universe in its totality. Hence, there is no way to know whether the cosmos is closed. Further, and most saliently, as energy is nothing, the conception of its conservation is absurd.
For all its spot-on predictions of the furniture in the world, physics is theoretically bereft when it comes to the essence of Nature. The history of physics shows that the science is a fiddling of equations until numbers eek out which match observations. Then physicists rashly assume that their models tell all.
It is wrong to think that the task of physics is to find out how Nature is. Physics concerns what we can say about Nature. ~ Danish physicist Niels Bohr