Mystery boom
© The Scottish Sun
A boom heard and felt over three counties last Sunday may have no conclusive explanation.

There are many theories as to what the boom was - cryoseism, earthquake or sonic boom. But none have been definitely proven.

Cryoseism seemed to be the first theory most concluded on social media.

According to Frost Quake's website, a cryoseism is defined as "'a natural phenomenon that occurs when extremely cold temperatures lead to sudden deep freezing of the ground, after it has been saturated with water."

Earth science professor at Tennessee Tech Larry Knox said a cryoseism just wasn't likely.

"As I understand them, cryoseisms occur where the ground is saturated with ground water and temperatures drop suddenly to, or below, zero degrees Fahrenheit. There was a temperature drop on Sunday, but not of that magnitude," Knox said via email. "Also, cryoseisms are generally accompanied by earthquake-like vibrations that are strong enough for people to feel them - no earthquakes were reported as far as I know."

Geophysicist Paul Caruso of the United States Geological Survey (USGS) confirmed no earthquakes or abnormal ground movements occurred last Sunday between 2 to 4 p.m. in the Upper Cumberland region.

For the sonic boom theory, whether it be from a meteor or aircraft, it doesn't seem likely either because barometer readings would have recorded a sudden pressure change, Knox said.

According to Time and Date's website, the barometer readings in Cookeville for the hours between 2- 4 p.m. maintained 30 inches of mercury and there appeared to be no significant spikes or drops.

All and all, many theories surround the boom event from Dec. 10, but none have been proven. Like Knox stated, an explanation may simply be impossible to determine.