"Directed Energy Weapons" refer to any number of types of unconventional and exotic weaponry.
The full range of these weapons is classified information, so no attempts will be made to distinguish between categories within the realm of energy weapons, as doing so would imply specific knowledge of all that are available.
In addition, no claim is be made about whether the directed energy weapon operates from a space-, air-, or ground-based platform, nor are any claims made about whether or not it involves sound waves, antimatter weapons, scalar weapons, a facility like HAARP, etc.
However, the evidence appears consistent with the use of energy weapons that go well beyond the capabilities of conventional explosives.
Wikipedia article on Directed-Energy Weapons
Although speculation about DEWs on 9/11 began shortly after the event, one of the first scientists with relevant credentials to publicly propose the DEW hypothesis was Dr. Judy Wood, a former professor of mechanical engineering.
The following material is largely from her book Where Did the Towers Go?, as well as from her old and new websites.
Where Did the Towers Go?
I. 9/11 Enigmas
II. New Nomenclature
Free-fall time of a billiard ball dropped from the roof of WTC1, in a vacuum
Let's consider the minimum time it would take the blue billiard ball to hit the pavement, more than 1/4 mile below. Start the timer when the ball is dropped from the roof of WTC1, assuming this is in a vacuum, with no air resistance (note, large chunks of the building will have a very low surface area-to-mass ratio, so air resistance can be neglected).
From the rooftop of WTC1, drop one (dark-blue) billiard ball over the edge. As it falls, it accelerates. If it were in a vacuum, it would hit the pavement, 1368 feet below, in 9.22 seconds, shown by the blue curve in the figure, below.
It will take longer if air resistance is considered, but for simplicity, we'll neglect air resistance. This means that the calculated collapse times are more generous to the official story than they need to be.
The "Pancake Theory"
According to the pancake theory, one floor fails and falls onto the floor below, causing it to fail and fall on the floor below that one, and so forth. The "pancake theory" implies that this continues all the way to the ground floor.
In the case of both WTC towers, we didn't see the floors piled up when the event was all over, but rather a pulverization of the floors throughout the event.
So, clearly we cannot assume that the floors stacked up like pancakes. Looking at the data, we take the conservative approach that a falling floor initiates the fall of the one below, while itself becoming pulverized.
In other words, when one floor impacts another, the small amount of kinetic energy from the falling floor is consumed (a) by pulverizing the floor and (b) by breaking free the next floor. In reality, there isn't enough kinetic energy to do either.
But, for the sake of evaluating the "collapse" time, we'll assume there was. After all, millions of people believe they saw the buildings "collapse."
Note that the top "block" begins to disintegrate before the damaged zone starts to move downward
WTC2, demonstrating there is little to no free-fall debris ahead of the "collapse wave."
If there was enough kinetic energy for pulverization, there will be pancaking or pulverization, but not both. That energy can only be spent once.
If the potential energy is used to pulverize a floor upward and outward, it can't also be used to accelerate the building downward. In order to have pancaking, a force is required to trigger the failure of the next floor.
If the building above that floor has been pulverized, there can be no force pushing down. As observed in these pictures, much of the material has been ejected upward and outward.
Any pulverized material remaining over the footprint of the building will be suspended in the air and can't contribute to a downward force slamming onto the next floor.
With pulverization, the small particles have a much larger surface-area-to-mass ratio and air resistance becomes significant. As we can recall, the dust took many days to settle out of the air, not hours or minutes.
So, even though the mechanism to trigger the "pancaking" of each floor seems to elude us, let's consider the time we would expect for such a collapse.
To illustrate the timing for this domino effect, we will use a sequence of falling billiard balls, where each billiard ball triggers the release of the next billiard ball in the sequence by simply passing it in space.
This is analogous to assuming pulverization is instantaneous and does not slow down the process. In reality, this pulverization would slow down the "pancake" progression, so longer times would be expected.
Thus, if anything, this means the calculated collapse times are more generous to the official story than they need to be. Billiard balls are used as timing devices because they are identical (same size, mass, surface, aerodynamic properties).
‘Progressive Collapse’ in ten-floor intervals
To account for the damaged zone, let’s simulate the floor beams collapsing every 10th floor, as if something has destroyed 9 out of every 10 floors for the entire height of the building.
This assumes there is no resistance within each 10-floor interval, i.e. we use the conservative approach that there is no resistance between floor impacts. In reality there is, which would slow the collapse time further.
Also, there was only damage in one 10-floor interval, not the entire height of the building. Thus, if anything, this means the calculated collapse times are more generous to the official story than they need to be.
The clock starts when the blue ball is dropped from the roof (110th floor). Just as the blue ball passes the 100th floor, the red ball drops from the 100th floor. When the red ball passes the 90th floor, the orange ball drops from the 90th floor, ... etc.
Notice that the red ball (at floor 100) cannot begin moving until the blue ball reaches that level, which is 2.8 seconds after the blue ball begins to drop.
This approximates the "pancaking" theory, assuming that each floor within the "pancaking" (collapsing) interval provides no resistance at all.
With this theory, no floor below the "pancake" can begin to move until the progressive collapse has reached that level. For example, there is no reason for the 20th floor to suddenly collapse before it is damaged.
With this model, a minimum of 30.6 seconds is required for the roof to hit the ground. It would take longer if accounting for air resistance.
It would take even longer if accounting for the structure's resistance that allows pulverization. The columns at each level would be expected to absorb a great deal of the energy of the falling floors. Thus, if anything, this means the calculated collapse times are more generous to the official story than they need to be.
‘Progressive Collapse’ in one-floor intervals
Similar to the previous case, let's consider a floor-by-floor progressive collapse.
The minimum time for the collapse, if every floor collapsed like dominoes, is 87-97 seconds.
‘Progressive Collapse’ at near free-fall speed
Now, consider this chart.
Let's say that we want to bring down the entire building in the time it takes for free-fall of the top floor of WTC1. So, If the entire building is to be on the ground in 9.22 seconds, the floors below the "pancaking" must start moving before the "pancaking" ("progressive collapse”) reaches that floor, below.
To illustrate this, use the concept of the billiard balls. If the red ball (dropped from the 100th floor) is to reach the ground at the same time as the blue ball (dropped from the 110th floor), the red ball must be dropped 0.429 seconds after the blue ball is dropped. But, the blue ball will take 2.8 seconds after it is dropped, just to reach the 100th floor in free fall.
So, the red ball needs to begin moving 2.4 seconds before the blue ball arrives to "trigger" the red ball's motion. That is, each of these floors will need a 2.4 second head start for falling -- before the "free falling" floor is triggered to drop.
But this also creates yet another problem: "the resistance paradox." How can the upper floor be destroyed by slamming into a lower floor if the lower floor has already moved out of the way?
So, for the building to be collapsed in about 10 seconds, the lower floors would have to start moving before the upper floors could reach them by gravity alone.
Did we see this? It seems pretty clear in some of the videos. The "wave" of collapse, progressing down the building, is moving faster than free-fall speed. This would require something like a detonation or destruction sequence.
Realizing that, for example, the 40th floor needs to start moving before any of the upper floors have "free-fallen" to that point, why would it start moving? There was no fire there. And, if anything, there is less load on that floor as the upper floors turn to dust.
In this picture, notice that WTC2 is less than half of its original height, yet has no debris that has fallen ahead of the demolition wave.
How could the ground rumble for only 8 seconds while WTC1 "disappeared?"
This part of the building surely took a lot longer to hit the ground as dust than it would have if it came down as larger pieces of material. Much of this paper is covered with dust, indicating that this dust reached the ground after the paper did.
There are a few tire tracks through this dust, but not many, so this picture was probably taken shortly after one (or both) of the towers were down.
If there had been a strong wind blowing the dust around, it would blow the paper away before it would have blown the dust onto the paper. So, the fact that much of the randomly-oriented paper is covered with dust indicates the relative aerodynamic properties of this dust.
In a conventional controlled-demolition, a building's supports are knocked out and the building is broken up as it slams to the ground; gravity is used to break up the building.
Here, it seems that the only use of gravity was to get the dust out of the air.
In conclusion, the explanations of the collapse that have been given by the 9/11 Commission Report and NIST are not physically possible.
A new investigation is needed to determine the true cause of what happened to these buildings on September 11, 2001.
The destruction of all seven WTC buildings and especially WTC1 and WTC2 may be considered the greatest engineering disaster in the history of the world and deserves a thorough investigation.