 Early advocates such as physicist Steven E. Jones, architect Richard Gage, software engineer Jim Hoffman, theologian David Ray Griffin, and Dutch demolitions expert Danny Jowenko, proposed that the aircraft impacts and resulting fires could not have weakened the buildings sufficiently to initiate a catastrophic collapse, and that the buildings would not have collapsed completely, nor at the speeds that they did, without additional energy involved to weaken their structures.The National Institute of Standards and Technology (NIST) and the magazine "Popular Mechanics" examined and rejected these theories.Specialists in structural mechanics and structural engineering accept the model of a fire-induced, gravity-driven collapse of the World Trade Center buildings, an explanation that does not involve the use of explosives.