The Light Comes onto Earth in Very Interesting Ways

We are bounded in a nutshell of Infinite Space: Reading #3: The Light Comes onto Earth in Very Interesting Ways

In the reading from “Astrophysics in a Nutshell” of Chapters 2.2.1-2.2.3 & 2.3, there is a quick mention of how light coming from the center of a star diffracts several times within the layers of a star before it is released into the Universe. Diffraction, in general, refers to how light changes its angle of travel once it changes medium. This happens often when you observe a fish inside a body of water, we think it’s on one place, but actually the photon bouncing off it come out at an angle which makes us think they are somewhere else. Diffraction, combined with some other characteristics of the Earth’s magnetic field and atmosphere composition, yield some of the most amazing physical phenomena humanity has encountered on Earth.

These are the Northern Lights, the Aurora Borealis (also known as the Aurora Australis in the case of the southern hemisphere), the most brilliant light show available on Earth. An Aurora is produced when the light entering the highly magnetized poles of the Earth, and thus become energized. This highly energized light then interacts with the many layers of Earth atmosphere, energizing the atoms in the gas as the light passes and changes direction repeatedly. As gases move and light diffracts, the spectacular formations of the auroras swirl and take shape. The colors of the Aurora themselves are determined by the gases present in the atmosphere as the light passes, like Neon for red and orange

Krypton for green and gray,

and Oxygen in rare cases for a majestic Red Aurora:

The difference in color stems from how these atoms interact with the light, mainly because of how atoms receive the light from the photons, and their electrons go up an energy level. Now energized, these atoms want to go back down to their ground state, which means releasing the accumulated energy, but this time with the color analogous to the energy received described by Plank’s equation: \[ E = h\nu = h \frac{c}{\lambda}\]

These lights, revered, feared, and gazed at for eons, are prime examples of how light interacts with matter, on a scale more relatable than the color of a planet several hundred or thousand light years away. 

References:

http://www.spaceweather.com/aurora/images2011/24oct11c/Dan-Salmons1.jpg

http://openwalls.com/image/19527/aurora_borealis_4_3234x2304.jpg

http://www.smh.com.au/content/dam/images/g/h/w/3/w/1/image.related.articleLeadwide.620x349.ghwn79.png/1435129354424.jpg

http://www.athropolis.com/arctic-facts/fact-nlights-color.htm

https://i.ytimg.com/vi/KAIyVZoXv9M/maxresdefault.jpg