This weekend is the 140th anniversary of the Great Chicago Fire. Despite the tales of it being caused by Mrs. O'Leary's cow, the investigative board following the fire never identified the cause.
But another factor suggests an intriguing, out of this world possibility. The same day of the Great Chicago Fire, another great fire occurred to the north in Peshtigo, Wisconsin. The Great Peshtigo Fire as it came to be known, consumed 1.2 million acres of forest (or twice the area of Rhode Island) and killed approximately 2,500 people.
And on the same day there were other large fires in the Lake Michigan region -- Holland and Manistee Michigan burned as well as Port Huron.
That such large fires all occurred on the same day tempts one to consider the possibility of a common cause. It turns out that witnesses that day also reported "balls of fire" falling from the sky and events of seeming spontaneous ignition. Well, in 2004, retired engineer, Bob Wood concluded that perhaps the fires were all started by fragments of the periodic comet Biela. See:http://pdf.aiaa.org/preview/CDReadyMPDC04_865/PV2004_1419.pdf
A century and a half later, it is doubtful that we will ever know what happened on that day, but just perhaps the cause come from the sky.