http://impactglassman.blogspot.com/2007/01/hand-waving-physics-of-911.html
I am curious what some of the engineers in here think of the claims being made in this article. I can't imagine this hasn't been discussed on here, but i'll be darned if I can find it in the search engine. So please don't give me too many lashes if it has been and point me to the right thread. Thanks!
A few things strike me as dishonest about this article, after wading through the initial disjointed and irrelevant rants. Firstly, the author's dismissal of Occam's razor is very carefully misleading. Let me explain.
Formulating a scientific theory generally proceeds from a series of observations, through formulation of the simplest hypothesis that can explain the observations, testing of the hypothesis with planned experiments or further observations, then refinement of the hypothesis if necessary to incorporate further observations. When that cycle has been run through enough times that no refinement is necessary, one has a useful theory.
Did you spot where Occam's razor came in there? Look after the first comma. It's not a case of generating lots of different hypotheses, evaluating each one, and choosing the simplest; it's about setting out in the first place to generate the simplest hypothesis, then only to complicate it if necessary to explain observations. So when Griscom gives his 1-0 score against Occam, he is effectively ignoring every time he has used Occam
implicitly rather than
explicitly. I suspect he's probably intelligent enough to realise that. Not a very good reflection on his intellectual honesty.
Comments on Garcia quoting a value to two significant figures are simply poisoning the well. But let's go on and look at Griscom's calculation of the loading for a 1 degree tilt, which he says will only give a 1.3 times excess over the static weight of the falling block. All very well, but what Griscom doesn't point out is that, if the falling block rotates, then the initial impact will be occur not across the whole structure. Instead, it will occur over a very small part of it, which will have far less ability to resist the impact. In fact, an energy calculation (comparing the gravitational potential energy liberated by a fall of one storey with the energy required to fracture the beams in the storey below) will show that these two effects precisely cancel each other. By only looking at one side of the equation, Griscom is deliberately misleading the reader on this point.
The 2000% live loadings comment has already been dealt with; the live loading of the structure is not its total weight, only the removable weight - furnishings, fixtures and occupants - so without an understanding of the ratio between live and dead weight in the structure it's meaningless (something I might forgive a fellow physicist for not knowing, but not for not trying to find out).
Finally, the comment that
"if some steel columns simply refused to bend or break at the same time, the “upper block” would have descended those 3 meters without picking up nearly as much speed"
is simply laughable. How does Griscom propose that this could happen? How could the upper block fall three meters while some of the columns holding it up remain unbent and unbroken? This is a steel framed building, not a mesh of rubber bands. Quite simply, as soon as enough columns have failed that the remainder do not have enough strength to hold up the upper part of the building, the remaining columns must fail almost simultaneously, not by coincidence (as Griscom disingenuously suggests), but simply by geometry.
Overall, nothing to see here; Griscom's arguments are fatally flawed.
Dave
