No, but American conspiracy-theorist physics is worse.
The homepage link on the keeling site said:
It didn't take long to find the fail in this model (source code is at the wtc.nlogo link near the top of the linked page).
Here's the setup to fail (color added for easier reading):
The paramenter floor-rupturing-momentum is being set to a "number of floors" (representing a mass value, as in number of floors worth of mass), times sqrt(2gh), a velocity value representing the freefall velocity after falling one floor height from a stationary start. So, the parameter represents the momentum that the mass of n floors (where n is set by floors-needed-to-break-floor) falling one floor.
It is then modified by a supplemental-floor-weakening parameter, which is set to zero by default.
The default values on the sliders gives floor-rupturing-momentum a value of 5 * sqrt (2gh), or the momentum of 5 floors having falling 1 floor's height from a standing start.
This is apparently based on NIST's estimate of the maximum dynamic load that a wtc floor could support. (Overlooking that it doesn't take the velocity gained from several meters of free fall to make a load dynamic.)
Now, here's the fail itself:
Some context is needed here. These computations are inside the loop that calculates the total collapse time by counting up the fall time of the upper mass for each collision with another floor. For each floor, the upper mass is assumed to accelerate at g for a distance floor-height; it is then slowed down (while its mass is increased) by the collision of each floor.
mfall is the falling mass just before each collision
vfall is the velocity of the falling mass just before each collision
mcoll is the falling mass after the collision
vcoll is the velocity after the collision
So, mfall * vfall is the momentum before the collision.
The value of vfall is negative (representing a downward fall) so the momentum value mfall*vfall is also negative.
Momentum is conserved in any collision, and the momentum of the newly added mass is zero before the collision. So, mcoll*vcoll = mfall*vfall.
That is, vcoll = ((mfall * vfall) / mcoll)
But the model says: set vcoll ((floor-rupturing-momentum + (mfall * vfall)) / mcoll)
Remember, vfall and vcoll are negative values, so adding the positive value floor-rupturing-momenum represents a decrease in momentum.
Keeling is subtracting an arbitrary amount of momentum, in a model of a collision for which the laws of physics say momentum must be conserved.
It would be reasonable to adjust the momentum based on some of the falling mass being shed in the collision (in which case the momentum would still exist, but not longer be contributing to the momentum of the falling mass), but Keeling isn't doing that.
What he's doing is subtracting an arbitrary amount of momentum, in a model of a collision for which the laws of physics say momentum must be conserved.
But, you might be thinking, some momentum has to be lost, to do the work that breaks the floors. But that's not the case. What's lost to do the work that breaks the floors is kinetic energy. When we apply
vcoll = ((mfall * vfall) / mcoll)
based on conservation of momentum, kinetic energy is lost. That's what does the work to break the floors.
If he wanted to, Keeling could also include a parameter representing some additional loss of kinetic energy (which would reduce the velocity) before or after each collision, to represent additional energy required to break structural elements.
But he isn't doing that. He's OMGWTF subtracting an arbitrary amount of momentum, in a model of a collision for which the laws of physics say momentum must be conserved.
Fail.
And, guess what? His parametric graph of his own model shows that the larger he sets the value of floor-rupturing-momenum, this physically impossible momentum loss parameter, the less his model behaves like the real towers did in the real world! Should this surprise anyone?
Respectfully,
Myriad
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