@spendulus, would you be so kind to provide your "math and physics" explanation for wtc building 7?
This is an interesting question. First, here is a summary - Wikipedia on building 7.
https://en.wikipedia.org/wiki/7_World_Trade_CenterThe building was situated above a Consolidated Edison power substation, which imposed unique structural design constraints. When the building opened in 1987, Silverstein had difficulties attracting tenants. In 1988, Salomon Brothers signed a long-term lease, and became the main tenants of the building. On September 11, 2001, 7 WTC was damaged by debris when the nearby North Tower of the World Trade Center collapsed. The debris also ignited fires, which continued to burn throughout the afternoon on lower floors of the building. The building's internal fire suppression system lacked water pressure to fight the fires, and the building collapsed completely at 5:21:10 pm, according to FEMA,[6] while the 2008 NIST study placed the final collapse time at 5:20:52 pm.[7] The collapse began when a critical internal column buckled and triggered structural failure throughout, which was first visible from the exterior with the crumbling of a rooftop penthouse structure at 5:20:33 pm. The collapse made the old 7 World Trade Center the first tall building known to have collapsed primarily due to uncontrolled fires,[8] and the only steel skyscraper in the world to have collapsed due to fire.[9]
I think we could all agree about the "uncontrolled fires." This leaves one with the simple question as to whether it is feasible or not that such fires could bring the building down. That can be examined by looking at the cross section of the steel at the ground level, and some estimates of the joules of energy softening that steel during the fire. Only the ground floor or basement needs to be considered for this.
It is interesting because what happened, happened on the inside, so there is no visual evidence. Remember in the prior post I mentioned the brilliant white of thermite, so bright you can't hardly look at it? That is one reason why thermite in additional to airliner bombs makes no sense for the twin towers - there was no brilliant white seen anywhere, let alone at the floors where the airliners hit.
To understand this, watch this video. It is a short example of thermite welding on railroad tracks.
https://www.youtube.com/watch?v=5uxsFglz2igIf you can get past the old style voice track, this is a good technical explanation.
https://www.youtube.com/watch?v=TstoubOQImQTherefore, one must use deduction to answer the question about bldg 7.