On the first morning of the new year, Andrew Koch was working at his computer in Pittsburgh when a thunder-like sound rumbled through his home.
He felt it in his chest more than he heard it, Koch said Tuesday. Only after Allegheny County, Pa., tweeted that there was "no explanation" for the loud noise did he check whether his home security cameras had captured the boom.
The footage had in fact caught what astronomers later concluded was a meteor exploding over western Pennsylvania around 11:20 a.m. on Saturday, producing an energy blast equivalent to 30 tons of TNT. The bolide — a meteor brighter than Venus — is believed to have weighed about 1,000 pounds, measured a yard in diameter and shot through the atmosphere at 45,000 mph, NASA said Tuesday.
A meteor of that size plunges into Earth's atmosphere every three or four days. But because most of the planet is water-covered, the majority of those meteors fall where no one sees or hears them, said Bill Cooke, who leads NASA's meteoroid environments office. Were it not for Saturday's cloudiness, Pennsylvania residents might have been treated to quite a show.
"If it had been clear, there would have been something 100 times brighter than the full moon moving from north to south in the Pittsburgh sky," Cooke said. "That would have been pretty cool to see."
Meteors have entertained people in Michigan, Puerto Rico and beyond in recent years. The most recent fireball prompted joking comparisons to the new film "Don't Look Up," which features astronomers trying to warn the world about a comet streaking toward Earth and satirizes indifference to climate change.
"The Netflix marketing budget for Don't Look Up is out of control," one person tweeted in response to the New Year's Day bolide.
Scientists kicked off their investigation into the cause of the boom by eliminating unlikely causes. The sound was audible over a large geographic area, which ruled out local phenomena such as fireworks. The National Weather Service had not recorded any thunder or lightning.
Then someone at the National Oceanic and Atmospheric Administration noticed light recorded by an optical instrument on the GOES-16 satellite, which monitors the eastern part of North America. At the time of the noise, the satellite’s Geostationary Lightning Mapper registered four flashes moving north to south. Lightning moves more randomly than that, Cooke said — but the pattern was consistent with a meteor breaking apart and producing flares.
The scientists then cross-checked the finding with logs from one of many infrasound stations placed around the world to monitor compliance with nuclear test ban treaties. As meteors travel within about 20 miles of Earth, they break apart and produce low-frequency infrasound that is inaudible to humans. The sound travels downward, Cooke said, causing the ground to shake and homes to rattle.
When the scientists saw that an infrasound station had recorded noise around the same time as the Geostationary Lightning Mapper, the mystery appeared to be solved.
"It left no doubt that what was located over western Pennsylvania on New Year's Day was a bolide breaking apart," Cooke said.
While meteor explosions tend to prompt fears of falling, flaming rocks, Cooke said damage caused by the blast's pressure is a much more realistic concern. Movies about meteor explosions, he added, are usually not accurate.
But Cooke said he can't speak to the specific imagery in "Don't Look Up," which is streaming on Netflix. He hasn't seen it.
“Rocks falling out of the sky, that’s work,” Cooke said. “So I wait for it to come on cable.”