JANESVILLE - What caused the window-rattling rumble that shook parts of southern Wisconsin on Sunday evening and lit up social media sites with speculation?
Everyone wanted to know the source of the sound they heard at about 8:15 p.m.
People reported hearing a roaring sound that lasted between one and three minutes.
It was heard in Janesville, Beloit, Milton, Evansville, Albany, Monticello, Monroe, Elkhorn and Delavan, among other communities, according to Facebook comments. The sound seemed louder and longer than an aircraft or thunder, according to the comments.
Commenters on The Monroe Times' Facebook page also reported hearing the strange sound in Darlington, Wiota, Blanchardville, Argyle and north of New Glarus.
It was raining but not windy in Janesville at the time.
The Rock County Sheriff's Office and Rock County 911 center told The Gazette it had received no calls about the phenomenon or any damage.
Here's a look at theories offered as explanations:
Was it a low flying plane?
K.C., who choose not to disclose his last name, said he was staffing the tower at the Southern Wisconsin Regional Airport on Sunday night. No planes were flying through his airspace during the time the noise was heard, he said.
Also, it was heard in several counties simultaneously.
"I heard the sound, too, and there wasn't any jets flying through or anything like that," he said. "If they would have came through our airspace, I would have seen it."
Was it thunder?
Officials at the National Weather Service in Sullivan had no radar contacts or weather events that might explain the noise.
Was it a meteorite?
Allard Beutel, acting director for news and multimedia at NASA's office of communications, told The Gazette that he checked with NASA's meteor tracking office and that there were no reports of a meteor Sunday night in southern Wisconsin.
"The short answer is the sound likely was not caused by a meteor or fireball," Beutel said. "Any noises produced by a meteor would sound like a sonic boom and last, at most, a few seconds."
Mike Hankey, operations manager for the American Meteor Society, said that even a large meteor creates a sound that only lasts a few seconds.
Was it a small earthquake?
According to the U.S. Geological Survey, there were no reports of any ground movement in the area at the time the sound was heard.
What else could it be then?
One theory is a transformer explosion in Beloit, but that wouldn't explain the sound being heard in several counties.
Milton resident Ryan Skinner, who has written multiple books on UFOs, said he isn't sure what the sound was, but he finds it interesting.
"I'm just curious of what it is," Skinner said. "This is great, I love it. What is it? If it ends up being a conventional explanation, I'm all for it."
Skinner, who has a private pilot license, said it could have been secret military exercises or a spy plane flying under radar detection.
Skinner admitted those theories could be wrong, but said he's sure it wasn't a conventional aircraft because the sound last longer than an aircraft quickly flying overhead.
The 115th Fighter Wing returned to its home base in Madison on Sunday but did so during the day. A ceremony was held for the airmen upon their return after spending the past three months at Kadena Air Base in Okinawa, Japan.
"This was constant tone of over two minutes with nothing lit up in the skies," Skinner said. "What I'm curious of is if this was some sort of airplane flying low with its lights off, you'd think someone would be aware of it. The only thing known to be overhead at that time was 747 going to Orlando at 12,000 feet. It was way too high for that noise."
"To be conspiratorial, this could have come from the upper atmosphere," he said.
Everyone wanted to know the source of the sound they heard at about 8:15 p.m.
People reported hearing a roaring sound that lasted between one and three minutes.
It was heard in Janesville, Beloit, Milton, Evansville, Albany, Monticello, Monroe, Elkhorn and Delavan, among other communities, according to Facebook comments. The sound seemed louder and longer than an aircraft or thunder, according to the comments.
Commenters on The Monroe Times' Facebook page also reported hearing the strange sound in Darlington, Wiota, Blanchardville, Argyle and north of New Glarus.
It was raining but not windy in Janesville at the time.
The Rock County Sheriff's Office and Rock County 911 center told The Gazette it had received no calls about the phenomenon or any damage.
Here's a look at theories offered as explanations:
Was it a low flying plane?
K.C., who choose not to disclose his last name, said he was staffing the tower at the Southern Wisconsin Regional Airport on Sunday night. No planes were flying through his airspace during the time the noise was heard, he said.
Also, it was heard in several counties simultaneously.
"I heard the sound, too, and there wasn't any jets flying through or anything like that," he said. "If they would have came through our airspace, I would have seen it."
Was it thunder?
Officials at the National Weather Service in Sullivan had no radar contacts or weather events that might explain the noise.
Was it a meteorite?
Allard Beutel, acting director for news and multimedia at NASA's office of communications, told The Gazette that he checked with NASA's meteor tracking office and that there were no reports of a meteor Sunday night in southern Wisconsin.
"The short answer is the sound likely was not caused by a meteor or fireball," Beutel said. "Any noises produced by a meteor would sound like a sonic boom and last, at most, a few seconds."
Mike Hankey, operations manager for the American Meteor Society, said that even a large meteor creates a sound that only lasts a few seconds.
Was it a small earthquake?
According to the U.S. Geological Survey, there were no reports of any ground movement in the area at the time the sound was heard.
What else could it be then?
One theory is a transformer explosion in Beloit, but that wouldn't explain the sound being heard in several counties.
Milton resident Ryan Skinner, who has written multiple books on UFOs, said he isn't sure what the sound was, but he finds it interesting.
"I'm just curious of what it is," Skinner said. "This is great, I love it. What is it? If it ends up being a conventional explanation, I'm all for it."
Skinner, who has a private pilot license, said it could have been secret military exercises or a spy plane flying under radar detection.
Skinner admitted those theories could be wrong, but said he's sure it wasn't a conventional aircraft because the sound last longer than an aircraft quickly flying overhead.
The 115th Fighter Wing returned to its home base in Madison on Sunday but did so during the day. A ceremony was held for the airmen upon their return after spending the past three months at Kadena Air Base in Okinawa, Japan.
"This was constant tone of over two minutes with nothing lit up in the skies," Skinner said. "What I'm curious of is if this was some sort of airplane flying low with its lights off, you'd think someone would be aware of it. The only thing known to be overhead at that time was 747 going to Orlando at 12,000 feet. It was way too high for that noise."
"To be conspiratorial, this could have come from the upper atmosphere," he said.