I understand that topic of essay competition is 'assumptions in physics' rather than any particular physical phenomenon.
Thanks for compliments.
All concepts have to be based on certain definite preconceived ideas, which we call assumptions. These may be results of our past experience or axioms which are widely believed to be true. In physics, an assumption is a statement that is accepted as truth without logical reasoning. It will not attract questions about rational behind it. However, all further reasoning should be based on it.
If we analyze contemporary physical theories, we shall notice that presence of physical bodies is common and necessary for all physical phenomena and related theories. Presence of physical bodies is the reason for all other physical phenomena and without physical bodies, nothing would exist. Absence of physical bodies would ensure absence of all physical phenomena (including our existence) and consequently, there will not be any need for physical theories.
Once, we accept presence of physical bodies, next step would be to answer basic questions like; what? where? when? how? etc. about physical bodies. A physical body, to be real, has to have objective reality in space. Space is an imaginary region, presupposed by rational beings, whenever they envisage real entities. Substance (stuff) gives a physical body, its objective reality in space. By definition, matter provides a body with its objective reality in space. Therefore, matter is the substance that makes physical bodies with objective reality. Thus, presence (or existence) of matter is a basic truth or concept in physics.
In my view, going beyond this concept is meaningless. Because, by definition, matter is the stuff that makes all physical objects. There is no other entity that can provide substance to a physical body. Matter, being real and ultimate substance, cannot be made out of something else. Hence, existence of matter (in universe) is the ultimate truth. This fact should be accepted as the fundamental assumption. Once it is accepted as such, no other questions about existence of matter will arise. No explanation will be required about its cause, creation or origin. Diverse physical bodies in nature would be structured in logical steps from matter alone. There will not be any prior steps to create matter. Hence, existence of matter is the solitary phenomenon without prior cause. All other phenomena are results of existence of matter.
Implication of your query arises from widely accepted belief that matter (or mass) is converted from energy. Energy is defined as 'ability to do work'. Ability is a qualification of some real entity (in this case, ability of a matter body to do work). A qualification is a functional entity without objective reality. It is not a physical entity. A non-physical entity cannot be converted to physical entity. Hence, it is illogical to believe that energy can be converted into matter or vice versa.
Once we accept existence of matter as the basic assumption, explanation on every physical phenomenon in nature should be logical extension of this assumption. Reasoning used for any physical theory should start from this basic assumption. All other secondary assumptions (if any) and explanations will be derived from this single basic assumption. Adding illogical assumptions (whenever certain phenomenon cannot be explained on the basis of basic assumption) to suit observation is not a correct practice.
No, Sir. I would emphasize the point that 'everything real is made of matter and nothing else'. Electrons and protons are superior physical bodies (fundamental particles) made of matter.
Thanks for your interest,