Barns Are Painted Red Because of the Physics of Dying Stars | Hacker News Reader

Barns Are Painted Red Because of the Physics of Dying Stars

smithsonianmag.com

15 pointsshovel8 comments

Actually, the reason iron is so cheap is because life chemistry and tectonic-hydrothermal processes have concentrated it. The bulk of the reserves date back from the Great Oxygenation event from 2-1 bn years ago when the first photosynthetic life oxidized the iron dissolved in the ocean and precipitated it at the bottom of the then-ocean. This didn't happen to aluminium, which is more abundant than iron, to the same extent. Aluminium was only discovered in the 19th century and only produced economically as a purified metal in the latter part of that century. Iron itself took some technology to become cheap and abundant and before the 12th century BC was regarded as a precious metal (see: https://en.wikipedia.org/wiki/Meteoric_iron ).

The price of metals does not match their abundance in the Earth's crust and least of which the Earth as a planet.

Aluminum's also bound much more strongly to its oxides. Generally you need electrical currents to smelt aluminum, which wasn't possible until the 19th century (with one possible exception, below).

Iron, on the other hand, can be heat smelted, using charcoal or coal. Iron smelting drove the use of coal as it was consuming so much by way of forests earlier. Generally, fuelwood (locally available) is more convenient than coal, only available from specific areas and mines, and which requires transport over large distances.

Overland transport prior to the 19th century was something avoided if at all possible, so coaling routes generally involved ships and oceans or rivers.

There's some evidence that a goldsmith in Rome may have found a process for smelting aluminum:

"One day a goldsmith in Rome was allowed to show the Emperor Tiberius a dinner plate of a new metal. The plate was very light, and almost as bright as silver. The goldsmith told the Emperor that he had made the metal from plain clay." From: http://www.world-aluminium.org/history/antiquity.html

Most versions have him being executed by the emperor to prevent the devaluation of copper and gold.

That's a rather tenuous connection. Nearly everything on Earth is due to the physics of dying stars. Once could also ask why so many houses in Greece are white and blue, and the answer would also be "because of the physics of dying stars."

This article focused on iron. The Earth's crust has more oxygen by mass than iron, but that point was left out.

It mentions that the Red Ochre dye has 3 oxygen atoms for every 2 Iron atoms.

Furthermore, no explanation given for why the described fusion process stops at 53, and why heavier elements are also present on Earth.

Nuclear binding energy: http://en.wikipedia.org/wiki/Nuclear_binding_energy

Iron is at the top of the binding energy curve, and hence the bottom of the potential curve. Effectively, it's at the bottom of a hill with hydrogen on one (very) high side, and uranium and the trans-uranium elements on the other (less) high side.

Yeah, it's not actually the physics of dying stars, but the physics of the nucleus and the fact that iron is at the binding energy maximum [1].

[1] https://en.wikipedia.org/wiki/Nuclear_binding_energy#Nuclear...

Other than very small traces of helium, all elements other than hydrogen are formed in stars. Mostly supernovae.

So if you want to know what stardust looks like, look around you.

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