Public Health 302

The basis for our current copyright laws in the United States came about under the Copyright Law of 1976, and has been amended several times--including as recently as June 2016. 

Copyright law protects origial published works--including articles, artwork, songs, films, books, musical scores, and more--from being reproduced, performed, displayed, and/or distributed without permission and prohibits the creation of derivative works (such as the usage of an original fictitious character by an unauthorized author or artist) for a variable amount of time. The length of copyright depends on when the work originated, but for most works by an individual, it is 70 years after the death of the creator, and for corporate entities 95 years from creation or 120 years from publication--whichever comes first. For more specifics on copyright duration, please consult this chart.

Public Domain are works that are legally defaulted to no longer being under copyright law.

This means that works in the public domain may be freely reproduced, performed, displayed, distributed, and remixed to form new derivative works without special permission.

Many online archives, historical collections, and more contain public domain works because of the historical nature 

Other works are intentionally placed in public domain, such as those created or published under Creative Commons licenses 

Other works may enter Public Domain because they have ben orphaned or the copyright owner failed to renew copyright.

There are also certain types of things--such as ideas, titles, common sayings, etc--that are not covered by copyright and cannot be enforced and are therefore part of the Public domain.

Public Domain works still need to be cited when used in research papers and projects though. The work of the original creators deserves credit where credit is due because the ideas matter.