Was it a secret military exercise, the beginning of the Mayan prophesy or an alien invasion?

A loud boom, heard by Pocono residents and others throughout northeastern Pennsylvania the night of March 30, remains a mystery.

The boom, heard at about 10:10 p.m., shook cars and houses from Long Pond to Bushkill.

Pocono Record readers at the time speculated it was a tanker wreck on Interstates 80 or 380, a bunch of semi-trucks rolling down a quiet street or an exploding meth lab.

Some residents reported a bright flash in the sky that didn't appear to be lightning just before the blast.

But most readers agreed the sound was no routine thunder.

What it wasn't

One thing it probably wasn't was an earthquake.

The U.S. Geological Survey noted five reportable earthquakes worldwide between 10:02 and 10:22 p.m. The closest to the Poconos was a 1.6 magnitude quake in Seeley, Calif., more than 2,800 miles from northeastern Pennsylvania.

Ohio meteorologist and Pocono weather expert Ben Gelber said the sonic boom was probably due to thunderstorms.

"A similar boom was heard in Honesdale, which rules out a local explosion of some kind," he said. "Acoustic 'shock waves' triggered by a lightning flash trapped in a cold surface can be uncommonly and frighteningly loud."

Temperature readings that night were in the low 40s.

Thunder has been known to crack wood and shatter windows in extreme circumstances, according to Gelber. The sound waves are refracted or trapped in the lowest layers of the atmosphere just above us.

"The timing with storms present, a preceding flash and sonic boom reports separated by 45 miles fit with scattered thunderstorms along a warm front overrunning cold air near the ground," he said.

Unlikely explanation

An astronomer Gelber consulted said there was a remote chance that a fragmenting meteoroid could have been responsible for a sonic boom as it passed through a thicker atmosphere closer to the surface.

"This would be a rare situation, and almost certainly would have left some magnetized fragments locally for such a large explosion to occur, and simultaneously during a thunderstorm. However, this would likely not account for the sonic boom around Honesdale," Gelber said.

The Poconos are not alone in unexplained noises.

A small New England community has been beleaguered by mysterious blasts for more than 300 years, baffling scientists and residents, according to published accounts.

The town, Moodus, Conn., is about 30 miles outside of Hartford with a 2010 population of 1,413.

The Wangunk Indian tribe lived in the area during the middle and later parts of the second millennium. The town's name was derived from the Indian word meaning "place of noises."

For hundreds of years, residents spoke of unexplained underground thumps and thunders. They are reported to occur in a particular place about a mile deep and a few hundred yards wide.

The Wangunk tribe believed the booms were made by a spirit angered by the European colonists settling in the area. The settlers blamed the noises on the battle sounds of good and evil witches fighting for their puritanical souls.

Investigators have been unable to explain the noises, which could disappear for a decade at a time.

Geophysicists blamed "microquakes," which occur periodically, but that didn't really explain why they would make noises that sound like distant thunder or cannon fire.