Biography & contributions
Anders Celsius was a Swedish scientist born on November 27, 1701 – died on April 25, 1744. He was professor of astronomy at Uppsala University from 1730 to 1744, but traveled from 1732 to 1735 visiting notable observatories in Germany, Italy and France. In 1742 He introduced Celsius temperature scale.
Celsius researched on aurora borealis phenomenon and he observed the variations of a compass needle and found that larger deflections correlated with stronger auroral activity. He described that there is dependence between boiling of water and atmospheric pressure.
Celsius defined zero degrees as the temperature at which water freezes, and 100 degrees as the temperature at which water boils. He gave a rule for the determination of the boiling point.
Chemistry of aurora borealis
The aurora borealis also known as the Northern Lights, an Aurora is a beautiful natural phenomenon that often occurs in the polar regions of Earth. It appears as colorful clouds and rays of green and red (and sometimes blue) light that dance across the sky.
The aurora is formed when charged particles (electrons and protons) are guided by the Earth's magnetic field into the atmosphere near the poles. When these particles collide with atoms and molecules of the upper atmosphere, primarily oxygen and nitrogen, some of the energy in these collisions is transformed into the visible light that characterizes the aurora.
The energy source for the aurora is 149 million kilometers (km) (93 million miles) from Earth at the sun. The sun continuously emits charged particles (mostly protons and electrons), which are the byproducts of thermonuclear reactions occurring inside the sun. These charged particles make up the solar wind, which travels away from the sun through space at speeds ranging from 300 to 1,000 km/sec - about a million miles per hour.
The high-energy electrons and protons traveling down Earth's magnetic field lines collide with the atmosphere (i.e., oxygen and nitrogen atoms and molecules). The collisions can excite the atmospheric atom or molecule or they can strip the atmospheric species of its own electron and create an ion. The result is that the atmospheric atoms and molecules are excited to higher energy states. They relinquish this energy in the form of light upon returning to their initial, lower energy state. The particular colors we see in an auroral display depend on the specific atmospheric gas struck by energetic particles, and the energy level to which it is excited. The color of the aurora depends on which atom is struck, and the altitude of the meeting and among them two main atmospheric gases involved in the production of auroral lights are oxygen and nitrogen.
Aurora Colors According to Altitude
Oxygen is responsible for two primary auroral colors: green-yellow wavelength of 557.7 nanometers (nm) is most common, while the deep red 630.0 nm light is seen less frequently.
Nitrogen in an ionized state will produce blue light, while neutral nitrogen molecules create purplish-red auroral colors. For example, nitrogen is often responsible for the purplish-red lower borders and rippled edges of the aurora.
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