A mysterious "boom" rattled ears and registered on scientific equipment in parts of Alabama on Tuesday, and officials with NASA and other government agencies still have no idea what caused it, the Birmingham News is reporting.
On Tuesday, at about 1:39 p.m. local time, residents in the towns of Arab, Anniston, Hayden, Kimberly, Center Point, Jasper, and Gardendale reported hearing the boom and reported it to law enforcement. It was also picked up by scientific instruments.
- At the U.S. Geological Survey's Lakeview Retreat near Centreville, a seismograph picked up the sound, which researchers described as a "fairly loud boom."
- The Elginfield Infrasound Array, in Canada (600 miles away from the source of the sound), also picked up the sound beginning at around 2:02 p.m. local time in southern Ontario. The sound, and sonic remnants occurring after the initial boom, continued for about 10 minutes. The fact that the Canadian equipment didn't pick up the sound until half an hour later can be explained by the fact that sound travels at about 767 miles per hour.
- Eyewitnesses on the ground say they noticed a vapor trail.
Officially, supersonic aircraft are not supposed to fly over populated areas, according to Parade. However, it's not outside the realm of possibility that a military craft might have broken the rule. Similarly, NASA concedes that the explosion could have been caused by something on the ground, although the vapor trail seems to rule that out.
The other possibility is what scientists call a "bolide," which is a meteor that explodes in the atmosphere. Though rare over populated areas, bolides have been known to occur, sometimes to devastating effect. For example, in 2013 a bolide exploded over Chelyabinsk, Russia, and the resulting shockwave damaged buildings across the region.
By the way, the meteor in question was almost certainly not one of the Leonid meteors. The annual Leonid Meteor Shower occurs every year when the Earth passes through the tail of the comet Tempel-Tuttle and is expected to peak this weekend. However, the meteors that light up the sky during the Leonids (and other meteor showers) are generally small -- about half the diameter of a penny; that is, too small to make a noise when they explode.
NASA hopes to study the data this week and reach an official conclusion as to what caused the sound.
[Featured Image by Kues/Shutterstock]