Fireballs
Derbyshire Police have revealed that the loud explosion heard in Derby city and the surrounding countryside area on Thursday morning was a sonic boom caused by a Royal Air Force (RAF) jet.
According to the authorities, the RAF Typhoon jet triggered the "loud bang" while moving at high speed to intercept an Air India flight from Mumbai to Newark after receiving a "security alert."
However, state and federal officials say they don't know why it happened or what it was.
Scott Sharp, a meteorologist with the National Weather Service in Raleigh, said the boom could have been distant thunder coming from storms that moved through Davie, Yadkin, Stokes and Davidson counties at the time.
Dan Blakeman, a geophysicist with the National Earthquake Information Center in Denver, said there were no reports of earthquakes anywhere Monday night in North Carolina.
"I heard the boom - it was quite loud - but I also felt it. I felt my house move," said the real estate agent, who lives in the Crown Point neighbourhood near the escarpment.
Turns out bewildered residents across the city heard the same thing after 2 a.m. On the beach strip. The Mountain. Even Ancaster.
Adlam posted a question about the sound blast on Facebook that quickly spawned 500-plus comments, theories and, obviously, fart jokes.
But so far, the source of the thunderous bang remains a mystery.
Was it a supersonic jet? An industrial accident? A skyquake? Nobody seems to know.
They say they heard or felt a blast, but authorities say they can't determine a cause.
Micki Tapper says she was awake at 7:30 a.m. That's when she heard it.
"There was just a really loud boom. My house shook, my windows shook," Tapper said.
The sound is picked up by her security camera microphone. You can hear a noise, but you can't discern much about it, or how far away it was.
Still, it was alarming. Tapper says she went outside to look around her home because she thought a tree fell on her house.
Meteor expert Peter Brown of the University of Western Ontario says the infrasound signal is consistent with a "small multi-meter sized near-Earth asteroid." According to data compiled by NASA's Center for Near Earth Object Studies, asteroids of this size and energy hit Earth's atmosphere about once a year. That means it's rare-but not exceptionally so.

A sixteenth century illustration showing Montezuma observing a comet. The European Space Agency has a different plan.
Since the first comet mission, all the way back in 1978, numerous space agencies have made more than a dozen comet flybys, including one rendezvous and landing.
But never before has a mission attempted to visit a comet on its first plunge toward the sun, when its never-before-heated surface is almost unchanged from when it formed at the dawn of the solar system, some 4.5 billion years ago.
The recently approved mission, called Comet Interceptor, will also be unique in what it does as it nears its target.
Rather than simply flying by, it will split into four parts, each of which will whizz past the comet on a slightly different trajectory.
Three of these will be tiny instrument packages, which will view the comet from different angles. This will allow scientists back on Earth to create detailed 3D models not only of its surface, but of the gas, dust, and plasma surrounding it.
The fourth will be the mother ship, which will collect data from the smaller probes and relay it back to Earth.
"It's a novel concept," says Fabio Favata, head of the Strategy, Planning, and Coordination Office in ESA's Directorate of Science.
Details of the mission have yet to be determined, but the use of the word "fast" in its description doesn't mean it will be traveling at warp speed.
According to the operator of the cameras, the blast at 10 pm sent shockwaves towards the Brisbane area.
A second camera showed the blast lighting the sky green above homes in the city of Ipswich.
Comment: The BBC posted footage of the 'sonic boom':