Already on edge days after two bombings in New York and New Jersey, residents were startled on Wednesday afternoon by an earthshaking boom that thundered across several neighborhoods in Queens and on Long Island.

Many jumped on Twitter to unleash a stream of panicked, anxious questions: Did you hear that? What happened? Had terrorists struck again?

Well, New York, there is good news and bad news. The noise that shook buildings and rattled nerves does not appear to have been caused by terrorism. But no one seems to know what, exactly, was the cause.

Calls flooded into the New York Police Department and the Fire Department, which sent units to investigate the reports in "a ton" of locations, according to a spokesman. Shortly after the first reports, the police tweeted that the noise had been caused by two F-22 military aircraft flying over Queens.


There was one problem with that explanation. The North American Aerospace Defense Command in Colorado Springs, which coordinates the country's air defense, said that explanation was not only inaccurate, but also not possible.

"I can tell you, we checked in with the folks in our command center and first of all we don't have F-22s who are flying for the enforcement of the F.A.A. temporary flight restriction that exists over New York and part of New Jersey right now for the U.N.G.A.," said Michael Kucharek, a Norad spokesman, referring to this week's meeting of the United Nations General Assembly.

"We do have, I can tell you, a couple of airborne fighters, but they are flying at such an altitude and such an airspeed that it would not have caused this," Mr. Kucharek continued. "So at this time there is no indication that it was a Norad asset that caused this noise or sonic boom, as people are calling it."

So what does he think caused the loud bang? "I wouldn't even want to speculate," he said.

One early theory, floated on Twitter by the Fire Department in Oceanside, N.Y., was that the noise was caused by fighter jets escorting Air Force One to Kennedy International Airport. But the president was in Manhattan at the time. The Fire Department later deleted its tweet.

The Air Force's Air Combat Command offered another possibility later on Wednesday afternoon. It tweeted that the Police Department's report of F-22 activity over the city was incorrect. It said the jets patrolling the sky were F-15s but did not say they were responsible for the loud noise.


Let's jump to some quick science. What is a sonic boom? According to the National Aeronautics and Space Administration, a sonic boom is a deafening noise that people on the ground hear when a nearby aircraft flies faster than the speed of sound, which is roughly 760 miles per hour.

"Air reacts like a fluid to supersonic objects," NASA said. "As objects travel through the air, the air molecules are pushed aside with great force and this forms a shock wave much like a boat creates a bow wave. The bigger and heavier the aircraft, the more air it displaces."

New Yorkers have been celebrated this week for keeping their cool in the wake of the bombing that injured 31 people in Chelsea, but an unexpected explosion-like sound will rattle anybody. Many in Queens and neighboring Nassau County, on Long Island, wrote on Twitter that the noise shook their houses, set off car alarms and frayed their nerves.