We all know that barns are usually red. But why? Well, the answer is a little more complicated than you might think, but basically it's because of nuclear fusion.


Googler Yonatan Zunger took the time to explain the whole thing in great detail on Google+, and the train of thought goes a little something like this:

Barns are red because red paint is cheap.

Red paint is cheap make because the ground is loaded with an iron-oxide compound called red ochre that makes a good pigment. (or basically, rust)

The ground is loaded with red ochre because when stars die, physics dictates they generate a bunch of iron and explode.


It's that step where things get a little more complicated. Zunger explains it this way:

[When a star dies, it] starts to shrink. And as it shrinks, the pressure goes up, and 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 start to form heavier elements still, and so the cycle gradually repeats, with the star reacting further and further up the periodic table, producing 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. This collapse raises the pressure even more, and sets off various nuclear reactions which will produce even heavier elements, but they don’t produce any energy: just stuff.

This stuff-generation just continues for a while, churning out material with an atomic mass of around 56 (iron) until eventually, it meets its final demise and explodes (sometimes), seeding that material through out the cosmos.

It's that rusty startdust that litters the ground of this planet we live on and makes it cheap and easy to get a whole bunch of red paint for our barns. Crazy, right? You can dig waaaaaay deeper into the nitty gritty details by reading Zunger's wildly in-depth post. [Yonatan Zunger via Smithsonian Blog]


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