The Large Hadron Collider is the most expensive and sophisticated scientific instrument ever built. Its chief purpose is to find the Higgs boson. We don't know very much about the particle, but various people think that it will solve various physics conundrums, and it has to have mass in a certain range and various other properties in order to satify the theorists.
The viXra blog says that the LHC and other experiments are ruling out nearly all the hypothesized possibilities for the Higgs boson. We could get an announcement this week. If so, the LHC will prove a negative, and become the most exponsive failed experiment ever.
Update: Here is an amusing example of a politician claiming it’s impossible to prove a negative:
While Republicans produced no evidence of voter fraud from impersonation, Mecklenborg and other GOP leaders say they believe it is going on unreported. “I believe it happens, but it’s proving a negative,” Mecklenborg told reporters after the vote. “It’s impossible to prove a negative. How do you prove that fraud doesn’t exist there?”