Reports of light in the middle of the night called airglow or nocturnal sun— by which one could read— date back to the time of the Romans and have mystified scientists for centuries. Now Canadian scientists1 think they have the answer.
The oxygen we breathe is a molecule of two oxygen atoms. Beyond 60 miles from earth’s surface, ultraviolet light from the sun separates the atoms during the day. Then at night when the sun is gone, the atoms reunite and in the process release energy in the form of light. I find this counterintuitive, but it’s standard chemistry. Normally, while the energy is visible as light only to scientific instruments, sometimes humans can see it, but why?
Think of air currents as waves in the ocean. In fact they are called zonal waves and are influenced by Earth’s rotation and severe weather on Earth’s surface. Usually waves peak in different places, but occasionally there’s a pileup of waves in the same spot. This pileup is believed to account for increased intensity of the light to the point that it beautifully lights the sky. Despite growing up on a farm with minimal light pollution, I’ve never seen it. It happens about once a year and is more common at middle latitudes.
It must be exciting to be a scientist who unlocks the mysteries of our universe.
- Gordon Shepherd and Young-Min Cho, atmospheric scientists from York University.
Source: NYTimes Article