An extraordinarily loud boom shook parts of South Carolina on Thursday, with witnesses across the state reporting a noise like a deafening thunderclap, or a huge explosion.
But what caused it? While residents and internet sleuths quickly came up with theories, experts just as quickly dismissed them, leaving a mystery that lingered a day later.
About 5:30 p.m. on Thursday, the boom was heard throughout the central part of South Carolina, including the capital city, Columbia, and an area extending at least 40 or 50 miles east. The United States Geologic Survey said it was centered just about three and a half miles northeast of St. Andrews, in the Columbia metro area.
There were no reports of damage or serious injury, but it left the region puzzled. Hundreds of residents described hearing the sudden, jarring noise, and a rumble that felt like an earthquake. Many expressed their alarm on social media: “It felt like a bomb just went off,” one person said, while another wrote, “It shook my room.”
No company or entity immediately claimed responsibility. Many possibilities were ruled out. Some experts wouldn’t commit to one theory yet.
So the question remained: What the heck was that?
Could it have been a terror attack?
The Richland County Sheriff’s Department, which covers Columbia, did not seem to think so: “R.C.S.D. has not been notified of any causes,” it said. “If we receive any information that it was a law enforcement issue, we will provide updates.”
Did a meteor strike?
No, according to NASA: “We have no eyewitness reports of a fireball and no satellite detections of a meteor over the area at the time,” it said in an emailed statement.
So, we can categorically rule out a meteor? Not so fast: “It’s still possible this was caused by a large meteor, and no one saw it,” NASA added.
Seems like an earthquake then.
“This event is not an earthquake,” said the U.S.G.S.
“We can confirm there was no earthquake activity this evening in or around Columbia, S.C.,” the agency said on Thursday. “The last reported tremor in that area was a magnitude 1.9 on May 22. Nothing today.”
The U.S.G.S., however, did offer a theory on what the sound might have been.
Tell me.
“The recorded waves and eyewitness reports are consistent with a sonic boom,” the U.S.G.S. said in a statement.
A sonic boom is created when an object travels faster than the speed of sound, about 767 miles an hour.
The fast-moving object pushes air forward. When it reaches the speed of sound, these waves of air combine into shock waves, triggering a loud boom.
If the loud noise was indeed a sonic boom, that would open another mystery: What was the speedy object?
Not many things go that fast: The field is mostly limited to high-speed planes or spacecraft. And normally, because of the noise, planes are prohibited from hitting the speed of sound over land.
The agencies that operate such speedy vehicles had little to say.
NASA did not respond to a specific question about a possible boom-causing object. The Navy did not respond to a request for comment. The Air Force and Marines said on Friday they were looking into the matter but had no specific information.
As of Friday afternoon, the mystery lingers.
Livia Albeck-Ripka contributed reporting.
Victor Mather, who has been a reporter and editor at The Times for 25 years, covers sports and breaking news.
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