In the year 1770, the explorer Samuel Hearne was tramping through the snow and bitter cold near Great Slave Lake, in what would become the North West Territory, Canada. He looked up in the sky to see a shimmering and dancing curtain of green and yellow, high in the black sky. Today this spectacle is known as the Northern Lights.
A rustling and cracking noise like the flapping of a large flag in a gale.Samuel Hearne
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The Northern Lights
In the year 1770, the explorer Samuel Hearne was tramping through the snow and bitter cold near Great Slave Lake, in what would become the North West Territory, Canada.
He looked up in the sky to see a shimmering and dancing curtain of green and yellow, high in the black sky.
He also heard sounds that he described as “ a rustling and cracking noise like the flapping of a large flag in a gale”.
The Aurora Borealis
Hearne was an early chronicler of the phenomena of the Aurora Borealis, or the Northern Lights, but many others have observed this curious display of nature.
They have been described as rippling curtains, streamers, arcs, shooting rays, or even patchy cloud-like objects.
They often appear pale green or yellowish in color, although many different hues have been observed including red, yellow, blue, and violet.
An Audible Spectacle
There have been many reports from responsible observers of sound emitted from the display, similar to Hearne’s description. But this varies from person to person and has never been scientifically documented.
The aurora borealis generates an electrical field, and there is some speculation that the sensation of sound may come directly from the influence of these fields on the auditory nerves in some individuals.
What Are the Northern Lights?
The extremely high temperatures in the sun are enough to cause violent collisions between gas particles, so fierce that atoms are separated into protons and electrons in the corona above the sun’s surface.
This plasma, as it is known, can then be thrown off into space by the force of the sun’s rotation, and after a few days makes its way to the vicinity of earth.
There they collide with molecules high in the earth’s atmosphere, from about 50 miles (80 km) to 400 miles (640 km) in altitude, and these high-energy clashes emit energy in the form of light.
The characteristic greenish-yellow color is produced by collisions with oxygen molecules.
Common Gases Found in the Northern Lights
Nitrogen, the other most common gas in this interaction casts off a blue to purplish-red hue when stimulated.
During prominent displays, high-altitude oxygen can also emit a bright red color, creating a dramatic effect in the Polar Regions.
Solar emissions ebb and flow in a roughly eleven-year cycle, and at high points of the cycle the northern lights are more active.
The earth is in effect a giant magnet, with magnetic lines of force around the planet that are similar to those of a small, magnetized iron bar.
The charged particles in the solar wind tend to be attracted to the Polar Regions, but deflected from the equatorial areas.
This usually relegates the light shows to the Arctic and Antarctic Regions, but occasionally they are seen quite far to the south.
The southern lights or aurora australis occur simultaneously with the northern lights, and they tend to manifest as mirror images of each other.
Future Research Into the Northern Lights
Research into the northern lights phenomena is ongoing. The electrical fields produced can be very disruptive to power supply systems, and this is one incentive to find out more about this interesting aspect of nature.
If you find yourself in the northern, or extreme southern latitudes, look up and enjoy the show!