Public domain

The public domain consists of all creative works to which no exclusive intellectual property rights apply. Intellectual property refers to legal rights that allow creators to control how their work is used. In the public domain, these rights may have expired, been forfeited, or been waived. They might also be inapplicable from the start. Because no single person holds exclusive rights, anyone can legally use or reference these works without asking for permission.

Works enter this shared space through several distinct mechanisms. Many works enter because their copyright term has ended. In most nations, copyright protection lasts for 70 years after the death of the last living author. Mexico has a longer term, lasting 100 years after death for those who died since July 1928. In the United States, copyrights for books published between 1923 and 1978 lasted 95 years if properly registered. Some works, like the formulae of Newtonian physics or simple cooking recipes, are excluded from copyright law entirely. Other creators actively dedicate their work to the public through a waiver.

Different types of media have unique rules within the public domain. Books enter the domain when copyrights expire or are never granted. Project Gutenberg and the Internet Archive provide tens of thousands of these books online. Music has a complex history involving notation and recordings. While musical compositions often follow the 95-year rule, sound recordings have different protections. In the US, sound recordings might not be eligible for public domain status until between 2021 and 2067. Films also enter the domain in various ways. For example, the 1968 film Night of the Living Dead became public domain in the US because the distributor failed to include a required copyright notice.

The concept of shared resources has deep historical roots. While the specific term "domain" appeared in the mid-18th century, the idea comes from ancient Roman law. The Romans used several terms to define things that could not be privately owned. They used *res communes* for things everyone could enjoy, like sunlight, air, and the ocean. They used *res publicae* for things shared by all citizens. The modern idea of the public domain grew from these Roman legal concepts. In the 18th century, British and French lawyers used terms like *la propriété publique* to describe works without copyright.

Scholars view the public domain through different lenses. Some define it as a "negative space," meaning it is what remains after private copyrights are removed. This compares public property to private property. Others see it as a conceptual sanctuary. This view suggests the public domain should protect individual expression from being taken over by private interests. It is often described as a foundation for culture. Some use terms like the "intellectual commons" or the "information commons" to describe this shared space of ideas.

The public domain provides immense value to society. It serves as a building block for new knowledge, providing essential data, facts, and theories. It allows people to access cultural heritage, such as ancient Greek texts or Mozart's symphonies. It also promotes education by spreading scientific principles. Furthermore, it enables innovation by providing access to expired patents and technologies. This allows for low-cost access to information without the need to pay royalties. It can even support the democratic process by making news, laws, and judicial opinions available to everyone.

One of the most important uses of the public domain is the creation of derivative works. A derivative work is a new creation based on an existing one, such as a translation, an arrangement, or a film adaptation. While copyrighted works require permission for such changes, public domain works do not. This allows for massive creative expansion. For instance, the plays of William Shakespeare have been used in over 420 feature-length films. Artists also use famous paintings as starting points. Marcel Duchamp created a derivative work by using Leonardo da Vinci's *Mona Lisa*.

Ultimately, the public domain connects the past to the present and the future. It ensures that the materials of our cultural heritage remain free for all to use. This includes thoughts, words, and ideas that are necessary for a living culture. By allowing creators to build upon the work of those who came before, the public domain drives continuous human progress. It remains a vital system that balances private ownership with the collective needs of humanity.