It would be nice if you didn't copy and paste answers from anti-Islamic websites, or even visit them – ever. They don't prove anything except for their members/creators possessing an exceptional amount of stupidity and ignorance. I find it amusing that the foolish and ignorant people are so cocksure of their ignorance. :hmm:
If the sky isn't physical, is it something abstract? I'm not an expert on the nature of physics but I can safely say that the sky has a concrete existence because for one: we can see it!
Secondly, whatever the sky is defined to be as, it does not prove or disapprove of what Allah has said about the sky having 'pillars' that uphold it.
The universe not having any foreseeable end has no relevance to the question at all. Unless you mean to say that we can fly through what we know as the sky above our heads, and still not come across anything that is concrete enough for us to 'feel' or 'touch' it, does not yet still in any way negate the verse at all.
We know that radio waves exist because they enable wireless technology to operate, but you can't touch it or see it or even feel it. After hearing this are you going to ask me, "science says x about radio waves in contrary to Islam so please explain"?