Sweat

Ancient Incas believed gold was the sweat of the Sun.

That might have seemed stupid until August 17, 2017, when astronomers detected two neutron stars colliding. Event GW170817 confirmed that most of the gold in the universe is created in kilonovas: when two neutron stars lock into a tight binary orbit and crash into each other.

Neutron stars are the collapsed remnants of supernovas. They are tiny and incredibly dense. A teaspoon of their matter would weigh billions of tons on earth (if you could get it to earth, which you couldn't, because it would desttoy the earth). When neutron stars collide and explode, vast amounts of gold, platinum, and other heavy elements are flung out into space.

These elements form in milliseconds during the blast. Over billions of years, that material cools and condenses into clouds of gas and dust that form stars and planets. A minuscule fraction reached Earth.

Gold is unmistakably heavy in the hand.

That is because it contains a large number of protons (79) and neutrons (118) forced together in its nucleus. This requires extremely rare conditions, like neutron star mergers, which are estimated to occur roughly once every ten thousand years in a galaxy like ours.

Weight matters because physical systems stabilize around mass.

Gold became money because the universe made it impossible to fake.

Image above: Gold Mask, La Tolita culture, Ecuador, c. 500 BC to AD 500. Hammered gold, likely used in elite rituals or burials. Source: Casa de la Cultura, Quito, Ecuador.