Watch cases come in lots of different materials including steel, titanium, carbon fibre, plastic and platinum. But the most common choice for classic dress watches has to be gold: red gold, pink gold or white gold. But have you ever wondered where that gold originally came from? And by “originally” I’m not referring to a gold mine on earth but the original source of the gold even before it arrived on our planet.
Can you guess how this extra-terrestrial gold was made? I doubt it, but spoiler alert: it involves an explosion, a very big explosion!
Shock and Awe
The incredible shock waves generated by supernova were once thought to fuse lighter elements (up to iron) into heavier elements, e.g. gold. But the sums didn’t quite add up, i.e. the biggest explosions the the universe just didn’t seem big enough, or numerous enough, to explain the quantity of gold (and other heavy elements) in the universe.
So until recently, we weren’t really sure where gold came from.
A long, long time ago
Around 3.9 billon years ago, just as the very first micro-biotic life appeared on earth, two neutron stars collided. They were not very big, just tens of kilometers/miles across, but each had around 1.5 times the mass of our sun.
That collision caused a humongous explosion and light and energy radiated out in all directions.
Some of that light headed towards earth.
Last year, on the 3rd of June 2013, the flash of gamma rays from the collision of those two neutron stars 3.9 billon years ago reached earth because they were 3.9 billon light-years away from us at the time of the explosion.
Gold fever
The flash lasted 0.2 seconds, just half the blink of an eye. But that was long enough for NASA’s Swift satellite to pick it up and relay the news to earth. Over the next few days, telescopes on earth and in space (Hubble) searched the region where the flash came from.
After analyzing the data they came to the conclusion that neutron star collisions are responsible for creating virtually all of the heavy elements in the universe, e.g. gold, mercury, lead and platinum.
Images snapped by the Hubble Space Telescope nine days after that first 0.2 second flash provided evidence of a lot of heavy elements, including several moon masses of gold. “Given the amount of gold in that one collision, and the fact that these collisions are thought to occur once every 10,000 or 100,000 years in any given galaxy, the crashes could account for all of the gold in the universe,” reported reported Edo Berger of the Harvard-Smithsonian Center for Astrophysics.
The neuron stars that collide like this aren’t just flying around and unluckily hit one of their own kind. They are the result of a binary solar system with two giant stars that both explode as supernovas and collapse into neutron stars. Their gravitational force gradually pulls them together like magnets until they collide.
The resulting collision concentrates so much mass in one place that it collapses on itself, often triggering the formation of a black hole. However, a small amount of matter gets ejected and is eventually incorporated into the next generation of stars and planets in the surrounding galaxy. And some of the debris is flung even further afield.
Gold (and other heavy elements) is rare on earth because it is so rare in the universe. It’s estimated that all of the gold ever mined on earth would fit into a cube just 25 meters (82 feet) on each side and would fit in two Olympic-size swimming pools.
And if you are wondering why platinum is so expensive, it’s estimated that all of that noble metal ever mined would fit into a cube with 6.3-meter (20 feet) sides.
So how did the gold get to earth?
If gold was formed by colliding neutron stars in far distant galaxies, how did it get to earth you may well ask. The answer is meteorites.
And not just any meteorites. Most of the gold we are interested in, i.e. that we can hope to dig up, arrived by in a massive shower of meteorites that hit the earth 3.8 to 4 billon years ago. Before that the earth was still so molten that any heavy elements would have been pulled into the planet’s iron core.
So the next time you wonder if that watch with a gold (or platinum case) is really worth the money, just consider that it was formed during the collisions of neutron stars, ejected as the stars were collapsing into a black hole, and arrived on earth around 4 billon years ago by hitching a ride on a meteorite.
And that’s all before it was found, mined, refined, sculpted and fitted with a watch movement.
So making gold isn’t that difficult, simply crash two neutron stars into each other at very high speed, step back (a long way back) and then sift through the pieces while being careful to avoid possible black holes. But as the title warns, don’t try this at home!
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