Subject: How do I post a follow up question to a recently answered question?

I was reading an answer posted by Mr. Donald E Duggan (ID: 988153260.Ch ). I was 
confused with regard to a small aspect of his answer. "The only one of 
these things which is truly massless is heat, Light has a very small amount of 
mass according to the theory of relativity, albeit immeasureable, it is still 
implied." Is not light and heat (infered radiation) just different frequencies 
of the same kind of energy (EM vibrations)? How can heat be massless and light 
have mass? Additionally how can light (with some mass) travel at light speed? I 
have read numerous references that cite the massless nature of photons is what 
allows and even necessitates that light travel at light speed? Perhaps the Mr. 
Duggan is referring to the mass of photons via acceleration? Perhaps he ment 
heat as the molecular motion of a system? If so then what is the difference 
between the definitions  of heat (infered radiation) and the other (molecular 
motion of a system? Which concept is more valid? I'm very confused. Help.

Re: How do I post a follow up question to a recently answered question?