The events of 9/11 were huge. The body of evidence that the administration, or other agencies within the US government, were involved is also huge. The problem with summarizing the information is that the scale of the operation and its cover-up are so vast. Finding smoking guns is like picking up litter on a field. It's hard to move in a straight line. That makes it hard to create a simple narrative. My personal questioning of the events of 9/11 began a few years later, when my sister went to a 9/11 conference and brought back books, DVDs, and enthusiasm. I watched the DVDs and became especially fascinated with one clip where the North Tower appeared to be literally erupting as it fell. One streamer caught my eye because I was able to follow its trajectory. I did some simple measurements right on the TV screen and estimated that the horizontal ejection velocity of that stream of debris was around 60 mi/hr. These ejections of material were from high in the building. How could heavy steel members be thrown sideways so fast when even the downward collapse had not picked up very much speed? This did not seem to me to be consistent with a purely gravitational collapse. I was hooked. I started using some video analysis tools I use in my teaching to analyze the motions of various ejecta and the buildings themselves. Several videos of the collapse of both towers show waves of horizontal mass ejections that race down the faces of the buildings, nearly keeping pace with material falling outside the building, well below the zone of destruction itself. (YouTube: South Tower Coming Down and Race with Gravity.) The ejections appear to come from many floors at the same time, which is inconsistent with the idea that the ejections consisted of debris blown out floor-by-floor as the floors pancaked together. In addition to the massive waves of ejections there are many photographs and videos showing individual, focused, high-speed ejections of material many floors below the point of collapse. These are easily explained as explosive ejections. They are not convincingly explained as escaping jets of compressed air. The lack of sufficient cause for the collapse has been thoroughly documented, disputed, rationalized, and obfuscated. The jet fuel would have burned off within the first ten minutes. Most of the fuel burned up in a fireball outside the building, especially in the case of the South Tower where the plane mostly missed the core columns. The fires in the buildings, beyond the first few minutes, were essentially office fires, and not very large ones at that, ignited by the jet fuel, like lighter fluid on charcoal. Jet fuel is kerosene. Temperatures from either kerosene or office fires are insufficient to melt, or even catastrophically weaken, the massive steel columns running up the core of the building. Even if the flames and air temperature were maximally hot, the large mass of steel would wick away the heat and not raise the steel temperature sufficiently. For the steel temperature to come close to the air temperature the fires would have to be of long duration, but these fires were very brief, on the order of an hour. There are photographs and video footage of a woman leaning on a girder and waving in the hole where one of the airplanes crashed waiting to be rescued. This would seem to be direct testimony that the fires on the floors where the impact and the jet fuel had their greatest effect, had subsided, and the air and steel temperatures were moderate enough for people to walk around and touch the steel: nowhere near hot enough to cause failure of the structural steel columns. The fact that the fires were emitting black smoke is a sign that they were not burning at high efficiency, so high estimates for fire temperatures are unwarranted. Furthermore, no steel beams recovered by NIST during its investigation showed temperatures over a few hundred degrees"far below the temperatures needed to weaken steel. (The small sample of steel studied after the event is a problem in establishing steel temperatures conclusively, but by the same token, it speaks to the rapid and near-total destruction of the crime scene. Destruction of any crime scene is itself a crime. In this case it is part of an ongoing criminal cover-up of mass murder.) On the other extreme of temperatures, the research of Steven Jones, Kevin Ryan, and others have established that there were very high temperatures present in the building, not just enough to weaken steel, but to melt it. They found evidence for thermite in the rubble pile. There were pools of molten steel under the rubble piles of Buildings 1 and 2 (the North and South Towers) and Building 7 that remained molten for weeks after the building collapses, indicating a continuing energy source. NASA thermal images show evidence of high temperatures on the surface of the rubble pile for literally months, indicating even higher temperatures below. Furthermore, several research groups found tiny iron spheres in the dust scattered all over Manhattan. These are from tiny droplets of molten iron that solidified before hitting the ground. For there to be tiny spheres of iron in the dust, there had to be temperatures above the melting point of iron, and a blast event to atomize the molten iron into droplets during the collapse of the building, for it to be distributed with the dust. These are droplets of iron, not steel. They did not come from the structural steel of the towers. Iron spheres are an expected byproduct of the thermite reaction. Along with the iron spheres, Steven Jones also discovered red and gray layered chips in the dust samples, which turned out to have the signature of thermite. In April 2009 an international team of scientists published a seminal paper identifying the red and gray chips found in the dust as high-tech nano-thermite, also known as super-thermite. Unlike ordinary thermite or thermate, which could be considered high-temperature incendiaries, nanothermite releases its energy at a much higher rate because of the high surface-to-volume ratio of the particles. When combined with suitable volatile materials, nano-thermite can be formulated as an explosive. The ignition temperature is also much lower than ordinary thermite. Ironically, although Building 7 was ignored after it collapsed, there is ample evidence of foreknowledge. BBC and CNN both reported its collapse, complete with an explanation for why it happened, but they got their script wrong and did the report while the building was still standing. In both cases, the intact building is clearly visible behind the reporter announcing the collapse. There are also numerous video and narrative accounts of policemen and firemen clearing people away, saying the building was going to come down. Larry Silverstein himself, the owner of the building, at one point states that he and an unnamed fire department commander made the decision to "pull it." He later tried to re-interpret his comments, but from the context of the original statement he was clearly indicating they decided to demolish the building. The problem with this statement, of course, is that the building could not have been set up for demolition by the fire department in a matter of hours. Demolitions require weeks of preparation. If the demolition was planned, then the incidents of 9/11 had to have been known, and planned, in advance. I presented a talk on the physics of 9/11 at a physics teachers' conference at Occidental College in early 2008. The physics teachers in the audience certainly represent a sample of the population with above average intelligence and intellectual curiosity. Yet approximately one-third of the audience had never heard of the collapse of Building 7. Anyone who is "into" 9/11 has seen endless discussion of Building 7, but for those who depend on the mainstream media for their information, it never happened. Given that this was one of the most anomalous events of 9/11, there seems to be a clear conspiracy of silence in the media. Video footage was broadcast on the day of 9/11 itself, but whereas videos of the falling towers persisted on TV for weeks, Building 7 immediately disappeared from the scene. This shows that 9/11 was surely an inside job.