The massive 8.2-magnitude earthquake that rocked Mexico earlier this week was enough of a phenomenon on its own, but the quake also had something of a fascinating side effect: mysterious lights in the sky.
Numerous videos have been cropping up on social media showing the flashes brighten the night sky above Mexico City, but the flashes aren’t lightning coming from the clouds above, or even lights from planes.
Nobody is entirely clear why the bright lights actually happen, though they have been reported for years. Some argue that they are connected to the energy being released from the ground, while others say they are the result of secondary effects like explosions from power stations or electricity cables.
The mystery of the flashes has even led people to think of them as supernatural. “In the past, people often interpreted [earthquake lights] in religious terms, and in modern times they thought of UFOs, although there is a completely rational physical explanation that we are working on,” Friedemann Freud, who co-authored a study about the lights, told National Geographic.
Professor Freud’s study claimed that the lights came about because the electrical properties of rocks on the ground. The energy from the tremors release electrical charges from the rocks, which can then show bright blue and green lights across the sky in the wake of a tremor.
But other geological experts say that the lights aren’t actually anything to do with the ground at all. Instead, the flashes are small explosions coming from generators and other power systems that then can be seen across the night sky, they claim.