econ41 wrote:"They are all attempts at explaining something where my personal competence at both understanding and explaining is on par with or better than theirs.", I expect this should pose little difficulty."
Miragememories wrote:"Do you really know what it means to drop?
If we drop a ball for instance, it clearly means that at the very instant that we remove its last thread of vertical restraint, it will descend at free fall, only impeded by air resistance."
econ41 wrote:"Given that drop = "Fall, or allowing an object to fall" does not implicitly mean free fall I will recognise your wish to limit "drop" to free fall."
Actually, I made it perfectly clear that my interpretation of
drop explicitly meant
descend at free fall, only impeded by air resistance.
In the context of the upper section of WTC 1
dropping onto the intact lower section, I can see no other interpretation of the word. You could have used
sink,
gradually fail,
gradually buckle, etc., but you chose a term that clearly implies
suddenness or
instantaneous in nature,
D R O P.
Because the reader is so familiar with the meaning, it is
critically important that it be used properly before continuing on with a narrative that will otherwise contradict itself.
econ41 wrote:"My meaning however should be clear in context. So substitute "started to move downwards" or, if you wish, suggest some other phrase.
<cut for brevity>
So moving on and addressing more of your terminology:"
Miragememories wrote:"Using WTC 1 (the North Tower) as an example, you are proposing that at collapse initiation, its upper section [econ41 edit] dropped"started to move downwards" as a single unit or block."
econ41 wrote:[/i]"(terminology changed)...yes it came down as a recognisable entity. But don't read "rigid" or "solid" into either "single unit" or "block". I made that aspect explicit in my post:"[/i]
Well this is rather important do you not think?
A
rigid or
solid body impacting a structure is going to have a totally different effect than a
not rigid or
not-solid body.
Take a bag of sand for example. It has a fixed mass and while tightly contained, represents a solid and rigid body. Drop it, or if you prefer, make it move downward, when it impacts an object below, it will have a certain amount of concentrated momentum.
Now take the same bag and make it not rigid, or not solid, by breaking its containment structure (the burlap bag encasement) and drop, or if you prefer, pour its contents downward, when it impacts an object below, it will have a vastly different amount of concentrated momentum.
econ41 with added emphasis wrote:"We are at the stage where the lower portions of the falling top block is interacting with the upper portions of the lower tower. Neither is a rigid solid rather a framework of separate members each with its own flexibilities plus the flexibilities of the various combinations."
Well we have a more fragile upper block suffering pre-existing physical damage from the aircraft impact, on several of its floors, combined with whatever damage has resulted from 102 minutes of unfought fire, making contact with the undamaged, intact structure below it.
The intact structure below is rigidly interconnected by a perimeter of structural steel columns linked by concrete covered steel trusses joined to heavy structural steel core columns.
Miragememories wrote:"But getting back to WTC 1. Ignoring for the moment, the issue of the upper block's much smaller mass, what allowed that upper block to drop?"
econ41 wrote:"You are addressing the causes of the initial collapse. My post was referring to those moments in time following the start of the initial collapse where the various claims for "missing jolts" fit in the collapse sequence. I was not discussing the mechanisms which led to the initial collapse."
Are you suggesting that an error in understanding what caused the initial collapse is irrelevant to what followed?
econ41 wrote:"The rest of your post moves over three stages of collapse. I will identify but not address the issues which were in the pre-initial collapse stage or in the later global collapse stage. We can discuss them at a later stage:"
I think the basic premise on which you draw your forward conclusions must be proven to be reasonable before you can proceed with any analysis.
You are in effect asking that the reader accept your assumptions so that you can present conclusions which are wholly dependent on the legitimacy of your unsubstantiated assumptions.
The rest of your response just continues in the same vein.
The reason I make such a big issue about this, is that I believe for both of the Towers, the upper sections did
D R O P.
What I do not believe is that they
dropped as a consequence of fire-induced thermal expansion.
MM
by 
