Subject: What are the logical, scientific reasons why matter/energy is not eternal?

This question is for Benn Tannenbaum.  If I correctly understood your answer to 
my first question "Is matter eternal?" to mean that matter is not eternal, then 
I have clarified my question above. My definition of eternal is "having always 
existed in some form, with no beginning and no end(not created)".  In the "why" 
of your previous answer to me you state that "we believe the universe was once 
pure energy.....".  I am not looking for a "we believe" answer.  I am looking 
for all of the logical and scientific reasons/explanations why matter/energy is 
not eternal.  For example: if I wanted to try to prove to someone that 
the "theory" of evolution(macro, not micro)is false, one of my main arguments 
would be the "Law" of Biogenesis. 

Re: What are the logical, scientific reasons why matter/energy is not eternal?