Atheists Era said:
What is matter? What is eternal?
I have not found a quantitative definition of matter anywhere. Neither is there a quantitative definition of eternal.
You appear to be asking about the limits of a conservation law. There is conservation of energy, conservation of momentum, conservation of electric charge, and other conservation laws. Some scientists have been analyzing the general validity of some conservation laws.
The phrase "conservation of matter" used to apply to a law now called "conservation of mass." However, mass is now known to be equivalent to energy. Therefore, matter can no longer be equated with mass.
There is currently no unambiguous definition of matter. If there is an unambiguous definition of matter, then the definition would be of scientific interest in itself. Similarly, it would be interesting if there was a quantitative definition of eternal. Without knowing what these things are, one can not answer your question.
There is no definitive definition of matter. Therefore, it is meaningless to ask whether matter is eternal.
The word eternal is sometimes associated with the mathematical concept of infinity. Eternal is sometimes defined as infinite time. However, infinite quantities by definition can't be measured.
Infinity refers to asymptotic limits. Infinity is sometimes a useful concept when estimating the accuracy of certain physical expressions. However, there is no way to measure an infinite quantity even in principle. Therefore, the question of what is infinite and what is eternal has no physical meaning.
Your question is purely philosophical rather than scientific. There is no measurement that can answer your question, even in principle. If one can't measure something even in principle, then one can't discuss it scientifically.
The policy of this forum excludes purely philosophical questions. Therefore, the moderator may soon block the thread. However, before the moderator does that I suggest that you rephrase the question.
One can scientifically ask about the accuracy and reliability of a conservation law. If you rephrase your question with regards to a conservation law, then the discussion could continue. For example, you may start a thread asking about the limits of validity of the conservation of energy. I don't think the moderator could object to that.
Also, present some of your own work. For instance, how would you set up an experiment to determine if anything is eternal?