here's a very short (12 sec) scene i cut from the Nova production "Why The Towers Fell":-
BEHIND THE SHADOW?
this plainly shows the core momentarily standing during the collapse of WTC2. i suggest this may be what (obviously from a different distance/camera/angle) is seen as the "clouded shadow" in christopheras pic which he seems fixated upon insisting as evidence/proof that the core was made of concrete.
during the scene, a graphic of the structure in question is superimposed by Nova over the core to illustrate the WTC design architects point. sadly it's not that plain to see in my compressed cut/edit. i recommend christophera to watch the original film and try to find convincing evidence (besides several grainy inconclusive jpgs and a doctored diagram) to refute all the acknowledged expert professional opinions the movie shows.
Perhaps then he might be able to come to a more convincing conclusion as to how the WTC towers were constructed and therefore also more plausible mechanics of their eventual destruction.
the whole film is replete with illustrations, explanations and expert testament of/to the construction of the WTC. in fact the film particularly emphasises the true core fabrication.
LOOK and Learn...........
BV