By the way.Implosion is where base and centre are blown, which then PULLS the outside of the building towards the centre as it falls. This type of demolition happens from the bottom up i.e. the top of the building is the last part to lose it's visual form. WTC7 was done so.The towers, however were subjected to EXPLOSIVE demolition i.e. the material was explosively ejected outwards, away from the centre of the building, and it was done from the top down.