The green-blue glow that filled the New York City sky on Thursday night—making some wonder if aliens had landed and others fear they were witnessing the end of the world—was generated by burning aluminum, when one small bit of decidedly earthly Queens became momentarily hotter than the sun.
In providing this explanation for the mystery of the light, a spokesman for Consolidated Edison said there had not been a transformer explosion, as had been initially reported. The extraordinary event had in fact been traced to a voltage monitoring gizmo known as a coupling capacitor potential device—or CCPD if you happen to operate a power grid— that failed to function properly at a Queens substation on Thursday night.
That led to an arc flash in which electricity delivered via a 138,000-volt transmission line jumped from one point to another, ionizing the very air through which it leapt. The energy was too great to be constrained to a straight trajectory, and it began to arc with its own power. The arc grew higher and higher, as did the heat it generated.
“Temperatures can reach as high as 35,000 degrees Fahrenheit,” notes a General Electric fact sheet. “This is hotter than the surface of the sun.”
The fact sheet adds, “Arc Flash temperatures can... liquefy or vaporize metal parts in the vicinity.”
Some of the substation equipment is aluminum, which normally casts a silvery white light when it burns. But at extremely high temperatures such as this bit of sun in Queens, the light generated by the vaporized aluminum was the almost-Tiffany blue that New York City residents saw rise into the sky and spread through the low-lying cloud cover.
Here was light generated by energy as intensely elemental at that of the sun and stars, liable to make anyone think extraterrestrially. Here was power that could make you think of the making of the world (or, more likely, its ending since it had already been made).
Then, just as it reached its absolute apogee, just as its light had startled and mesmerized people by the thousand firsthand and by the million more on social media, the arc came to a point where it could no longer sustain itself. It extinguished itself and vanished.
The only injury was to one worker whose eyes had been overly dazzled. No aliens had landed. The world had not ended. Queens went back to being decidedly earthly Queens.
And that mysterious, alarming but entrancing light blue glow proved to be just some burning aluminum.