Barns are painted red because of the physics of dying stars
There is a reason why almost every barn you have ever seen is red. It has to do with the chemistry of dying stars. Seriously.
Yonatan Zunger is a Google employee. Zunger explained this fact on Google+. The simple answer to why barns are painted red is because red paint is cheap. The cheapest paint there is, in fact. But the reason it is so cheap? Well, that is the interesting part.
Red ochre is also known as Fe2O3. It is a simple compound of iron and oxygen. It absorbs yellow, green and blue light. It appears red. It is what makes red paint red. It is really cheap. That is because it is really plentiful. And it is really plentiful because of nuclear fusion in dying stars.
The only thing holding the star up was the energy of the fusion reactions. So as power levels go down, the star starts to shrink. And as it shrinks, the pressure goes up.
The temperature goes up until suddenly it hits a temperature where a new reaction can get started. These new reactions give it a big burst of energy. But it starts to form heavier elements. And so the cycle gradually repeats. The star reacts further and further up the periodic table. It produces more and more heavy elements as it goes. Until it hits 56. At that point, the reactions simply stop producing energy at all. The star shuts down and collapses without stopping.
As soon as the star hits the 56 nucleon (total number of protons and neutrons in the nucleus) cutoff, it falls apart. It does not make anything heavier than 56.
What does this have to do with red paint? Because the star stops at 56, it winds up making a ton of things with 56 nucleons. It makes more 56 nucleons containing things than anything else. That is aside from the super light stuff in the star that is too light to fuse.
What element has 56 protons and neutrons in its nucleus in its stable state? Iron. The stuff that makes red paint.
And that, Zunger explains, is how the death of a star determines what color barns are painted.
CRITICAL THINKING QUESTION
Why would farmers choose the least expensive paint for their barns?
Write your answers in the comments section below