Humming from the Sky
Some people have tried to say that airplanes are the cause of humming. That theory has not been proven. Others think that it's something extraterrestrial or secret government training. The government has not commented on what the sound was.
2011 Joplin Tornado
On May 22, 2011, Joplin, Missouri, was hit by a horrible tornado that killed 161 people and completely leveled the town. The tornado reached speeds upwards of 200 mph. Conspiracy theorists think that the crazy strength of the tornado was not a natural disaster.