Fifty years ago today, the United States, the Soviet Union, and the United Kingdom opened a treaty for signature that would become the backbone for international space law. It was a United Nations-approved agreement called the Outer Space Treaty, and 104 nations have become parties to the document since it was signed and enacted in 1967. Since then, the treaty has helped ensure the peaceful exploration of space, as well as provide a lasting framework for how nations are supposed to behave in Earth orbit and beyond.

In reality, the "Outer Space Treaty" is just a nickname. The document's full title is the "Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies." It's a lengthy name, but it sums up the essence of the treaty well: it's a list of principles for what nations can and cannot do in space and on other worlds.