NIST, the National Institute for Standards and Technology (a U.S. government agency) was authorized by Congress to determine “why and how WTC 7 collapsed.” NIST produced a preliminary draft of their final report in August, 2008 omitting the fact that Building 7 fell at free fall acceleration for part of its descent. After a physicist challenged NIST on this point the final report, in November 2008 admitted free fall acceleration for 105′ or 2.5 seconds.