Prior to the 20^th century, scientist believed that light was a wave phenomenon. In 1905, Albert Einstein suggested that light was not a wave, which went against everything that the classical electromagnetic theory stood for. In his eyes, light was a particle or “photon”. He proved this by using “The Photoelectric Effect” which acquired him a Nobel Prize. This discovery paved the way to other findings such as Bohr’s Model and the Emission Spectra or Atomic Spectroscopy. These findings apply to every element, including fictional elements that are found in Sci-Fi movies or comics, such as Tony Stark’s Arc Reactor that is composed of a fictional element known was “Vibranium”

No one knows exactly how the reactor works or how it is able to produce energy and be self-sustaining, but the reasons why the core gives out its light blue color are well known to us.

The photoelectric effect tells us the following: Light travels in packets of photons which contain a specific amount of energy, and that photons experience a “threshold frequency”, which below, no electrons can be emitted from a metal no matter how bright or how long the light was shone on that metal. Basically, Einstein proved that this phenomenon is quantized meaning no electrons can be emitted unless the light which is shone on the metal has a specific minimum energy or frequency. The amount of energy that a photon of light has can be expressed with the following equation: E = hν.

As for the Bohr’s Model, this discovery explained the emission spectrum observed with atomic spectroscopy. An atom can absorb various forms of energy such as heat, light, or electricity and when it does, the atom can sometimes remitted that energy as light. We observe this phenomenon every day and the most common example used is neon lights which are composed of neon atoms in the gaseous form that absorb electrical energy and remitted it as red light. However, scientists found that the light emitted from an element can be separated into multiple wavelengths by using a prism and a spectroscope to analyze the findings. The results were: a bunch of lines called the “emission spectrum” of that given element. Each element has a unique emission spectrum which can be used to identify it. This particularity can be explained with Neils Bohr’s Model which states that electrons travel around the nucleus of the atom in circular quantum orbits, meaning that those orbits are fixed in space and have fixed levels of energy (the energy of each orbit are unique to each element). Bohr explained that an atom can emit or absorb radiation only when an electron made a transition of orbits.

Now by putting all of the above information together, explaining the blue radiation from Tony Stark’s arc reactor is quite easy: the core absorbs energy from an unknown source and the Vibranium atoms inside are excited and jump to a higher energy orbit which in return jump back down to a lower energy level releasing radiation. This radiation can be composed of multiple wavelengths in the visible spectrum and also UV, X-Ray and Gamma rays, who knows (although X-Ray and Gamma radiation is unlikely because it would result in the death of Tony Stark in the long run). The fact that it is blue is because either it is the only radiation within the visible spectrum or it is the most abundant of them all, which causes that none of the other colors of light can be observed.