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Howdy, thanks for this opportunity to ask such questions. If an entity, such as a photon, has no "mass" : How can it "be" ? In what domain do we say that it "exist's" ?

Here is a long answer to a short question.

I think that the definition of "EXISTance" has changed with time. Thousands of years ago, only what was in one's vicinity and sensed by the five crude human senses "existed". As casual observations and later careful examinations made an increasing number of natural phenomenon apparent, visible, or comprehensible, concepts began to develop. This made the phenomena familiar, if not totally nested in the realm of existence. Some have eventually been found to "exist", some not, and some not yet.

As humans developed their skills and tools, they discovered the "EXISTence" of entities that were beyond their reach. A telescope made fainter objects in the sky visible, thus adding to the list of things that "existed". Microscopes made the physical existence of smaller beings known; they now existed "for us". But in fact they existed long before we discovered them.

Increasing sophistication and scientific tools have made some of the contrived concepts "real"; some of the intangible, tangible; some of the invisibles, visible. For example, pain is no longer a mental construct of an agonized soul, but a manifestation of the intensity of certain electrochemical messages in the body. Thus, pain gains a "real" existence in some sense.

So, for me, existence is synonymous with what we, as humans, can sense, observe, or construct. It is an ultimate bottleneck, for we cannot or do not know what we do not know. Do things we do not know about exist? If we do not sense an entity or its manifestations, it does not exist "for us" and we would not know it.

Back to your question: In what domain do we say a "photon" exits? It exists because of its manifestation, it's direct and indirect sensing, be it by human eyes or sophisticated scientific instruments. Having no mass is no barrier to something's existence. For now, some think that any being has either a mass or some equivalent energy; mass or energy being interchangeable. A photon, of course, has a definite quantifiable energy. What stronger evidence for existence that this do we need? Unless one defines existence to mean only what has a mass.

Who knows... maybe there are entities that have no mass, no energy, and yet exist. But this is something for cosmologists, philosophers, and theologians to contemplate... and I am none of the above.

Good luck.

Dr. Ali Khounsary

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