At 5:30 pm today, there was a boom heard in my neighbourhood and surrounding neighbourhoods, and nobody knows what it was. It wasn’t an explosion, it wasn’t thunder, it (probably) wasn’t a sonic boom (or someone would have known there was a jet overhead at that time), no companies have come forward and said that they were doing something at that time that caused a loud boom. Apparently there was also a loud boom in a town two hours away at the same time.
What do you suppose could have caused these mystery booms?