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Why the upper Earth’s atmosphere is green

If you look closely at the night sky you will see that, at the horizon line, you will see a faint green glow. This is called airglow and happens allover the world. The lower parts of it are green, but in the upper atmosphere the color is actually red.

What causes this airglow?

The excited oxygen atoms do this. During the day the UV rays hits the O2 molecules and, due to the high energies of UV rays, the molecule are split up in oxygen atoms that also engulf some of the UV energy. We call these oxygen atoms that have some extra UV energy in them excited atoms.

After a while the oxygen atoms combine into a molecule back again releasing a faint blue light. If you go between 95 – 100 km int he atmosphere you will encounter lone oxygen atoms that release the energy in the form of visible green light.

If you go above 100 km you will encounter excited oxygen atoms that will release a red light. The atoms become stable again by moving the electrons from higher energy states, where they wound up by eating some of the UV energy, to their stable or ground energy states. By moving the electrons back to the ground states a photon is emitted.

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Aloha: bacteria which feeds on and poops electrons

Isn’t that neat? These bacteria, Shewanella and Geobacter, cut the middle-man, metabolism, and eat up energy directly from the electrons. As you know, metabolism is responsible for transforming food into sugars like glucose which is then used to power up our bodies. Ultimately, our need for energy can be summed up into one single fact: we get the energy from the same electrons these bacteria are feeding off, but we do it using the long way.

Extreme Tech explains how the metabolism works in a few neat sentences:

When it gets right down to it, everything you eat is ultimately converted or digested into single molecules of glucose. Without going into the complexities of respiration and metabolism (ATP!), these sugars have excess electrons — and the oxygen you breathe in really wants those electrons. By ferrying electrons from sugar to oxygen, a flow of electrons — i.e. energy — is created, which is then used to carry out various vital tasks around your body (triggering electrons, beating your heart, etc.)

It seems that life is able to always surprise us. If these bacteria seem so alien int he way they eat and poop electrons, how much stranger could real aliens be? Answer: possible not much more stranger as the laws of physics are the same everywhere. Good bacteria, good 😀

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The double slit experiment which proves that the electrons are particles AND waves

In the video from above Brian Greene explains how the double slit experiment allowed us to see that the electrons are particles and waves in the same time, much like you hear all around that light can be seen as particle and as a wave.

The very act of observing the electron going through the slits determines that electron to behave only as a particle and thus the “shadow” left on the wall will show only two lines. That is happening because when we observer the electrons we interact with them and such we “somehow make them” show only their particle side, and not the wave one. In any case, qwuantum physics is amazing and some things are so hard to understand that you feel that you land in the realm of magic.


Via Jason.