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Iron is the sixth most abundant element in the universe. It’s so abundant because it is one of the major elements forged by stars as part of their natural lifespan.

Stars make so much of it because it has the highest β€˜binding energy’ of all the elements. This means that iron’s nucleus lies at the bottom of a ‘valley’. Moving up the slope on the left are elements lighter than iron like hydrogen, carbon, and oxygen. On the right are heavier elements, like uranium.

Moving atoms towards iron generates energy, like rolling a ball down the valley.

The ‘iron valley’

Stars fuse smaller atoms like hydrogen together, pushing them down the valley and towards iron.

Atomic bombs split larger atoms like uranium apart, pushing them down the valley from the other direction and towards iron.

Both methods extract energy from the atoms, but when you reach iron at the bottom you need to spend energy to make any change, like pushing the ball back up the slope.

Once a star starts producing a lot of iron, it’s a sign that it has reached a dead end by using up most of its fuel and is near the end of its life.

A star’s heat and light energy comes from pushing light elements like hydrogen and carbon towards iron

Depending on its mass, it may then erupt as a supernova or a planetary nebulae, in which the chaos of the explosion will fuse a wild assortment of other elements together, creating the heavy elements like lead and uranium.

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The explosion expels iron and other elements into space, where they will form new asteroids and planets. Iron is heavy, so it often sinks into their core, with some deposits left over in their crust.

On Earth, it’s been relatively straightforward for us to extract iron from the ground and melt it into new shapes, which has been hugely important for the development for our species.

Iron may be a dead end for stars, but it was the beginning for our advanced civilisation.

The ‘Iron Age’ defines the era of the ancient city states of Athens, Sparta, Troy, Carthage, and the Persian Empire. In mainland Europe, Celts built hill forts to defend their small agricultral communities. In India, the Vedas were being written. In every one of these cities you could hear the clank of the blacksmith’s anvil.

Iron is more difficult to work with than copper and bronze as it is melts at a higher temperature, so most early civilisations used them first before they developed the technology to use iron.

The earliest known iron goods were beads found in Egypt, made from metorite iron, but the first iron that was extracted from ore was in Mespotamia and Turkey. By modifying their furnaces to burn hotter and by adding charcoal, they sparked a chemical reaction which gave them lumps of iron which they beat into the shape of tools and weapons. Iron’s abundance, as well as the trade and cultural adoption of this technology, began the era known as the ‘Iron Age’.

Although iron is harder than metals like copper or bronze, it’s main disadvantage is that it is more brittle. Over time our use of iron has advanced to solve this problem. We’ve purified it then created mixtures with other things to create substances that are stronger than their constituent parts. Substituting charcoal with coke (as in the fuel that looks like coal) produces steel – one of the hardest substances yet developed.

Iron is heavily used today for everything from the steel supports of skyscrapers to our cultery.

Iron age weapons

It is a fascinating story from the big picture. Iron, as the waste product of stars, has been discovered and reused as the material backbone of an advanced species of ape for their civilisation.

It’s a reminder of the interconnectedness of everything in the cosmos, and how vast cosmic events billions of years in the past still influence our lives today.


Originally posted 2018-06-17 21:01:18. Republished by Blog Post Promoter

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