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The science behind the meteor-caused sonic boom heard over Utah

A screenshot from a doorbell camera captures a meteor streaking across the sky minutes before a boom Saturday morning.

A screenshot from a doorbell camera captures a meteor streaking across the sky minutes before a boom Saturday morning. (Ruby Anaya)



Estimated read time: 3-4 minutes

SALT LAKE CITY — Utah Gov. Spencer Cox was one of many who heard the boom Saturday morning.

The governor reported he was out for a run in Salt Lake City when the loud crash rattled the Wasatch Front, northern Utah and even parts of southern Idaho shortly after 8:30 a.m. He wasn't alone, as evidenced by all the social media posts and the sudden spike in Utahns searching terms like "earthquake," "explosion" and "boom" within the first 30 minutes, according to Google Trends.

The meteor theory emerged soon after an earthquake or military exercises were debunked. Scientists agree now that a meteor is all but surely the cause of the boom because the evidence, including Snowbasin Resort's web camera showing a meteor streaking over the mountaintops about the same time of the boom, points toward it.

Ben Bromley, a theoretical astrophysicist at the University of Utah, explains that it's not common for a meteor to create a boom like many Utahns heard on Saturday morning, but it's also not that rare either. This relative rarity is why he was like many going through the list of possibilities before thinking of meteors.

The event happened just after the Perseid Meteor Showers peaked this year, though experts say it is probably unrelated.

"This is really an exciting deal," he said Monday on KSL NewsRadio's "Dave and Dujanovic." "The videos beautifully confirm that a meteor is a real possibility and that's really exciting to me."

So why did this meteor possibly cause the sound everyone heard when so many others cruise over Utah silently? The California Institute of Technology points out that large meteors can cause a sonic boom which is often heard "before they are slowed to below the speed of sound by Earth's atmosphere."

The meteor that passed through Saturday morning was likely about 3 feet in diameter when it entered Earth's atmosphere to make a sound as loud as it did and as far as it was heard, Bromley explained.

"If it was super small, it would have just burned up in the outer atmosphere of the Earth, but this thing had to survive the heat of traveling through the Earth's atmosphere at a speed of tens of thousands per hour," he said. "These things are cruising really fast. ... It's got to be substantial in order to survive into the lower atmosphere of the Earth."

Had the meteor been 10 or 20 yards, or 30 to 60 feet in diameter, the sonic boom likely would have been severe enough to break windows and cause damage, he added.

As for the meteor itself, Patrick Wiggins, a NASA ambassador to Utah, told KSL-TV on Saturday it's likely that the meteor exploded as it passed through. He believes there are fragments of the meteor — some of which can be quite valuable — somewhere in Utah or east of it.

If you go out searching for it, good luck. Bromley said are "tens of thousands" of tons of micrometeorites all over the world from similar meteor events that are often difficult to find only because they don't really stand out among other rocks.

"The best way to find out if you have a meteorite is to find a rock sitting in a place where you don't expect rocks," he said.

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Carter Williams is an award-winning reporter who covers general news, outdoors, history and sports for KSL.com. He previously worked for the Deseret News. He is a Utah transplant by the way of Rochester, New York.

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