Paywalling the laws of the universe
authorea.com
authorea.com
It's ridiculous that copyright lasts so long. At least for nonfiction works, copyright should expire after a relatively short amount of time. There is no benefit to society by looking these great works behind paywalls.
That and much more is also downloadable from the MAA's Euler Archive: http://eulerarchive.maa.org
Note that Euler generally did not write in English. His math was usually published in Latin. If you want to read it in English, you need a translation. Although the underlying work is public domain, the translation may still be under copyright. The particular translation that the site links to was done in 2000, and so is still under copyright.
Nit: I'm not sure if I'd call Black-Scholes a law of the universe
That said, Boltzmann died in 1906, so even under this ridiculous system, it should have expired by now. However that doesn't mean it they can't put it behind a paywall. You can charge money for public domain works.
I think it's like sheet music that is in the public domain, they use the threat of legal action and strictly control access as a means of maintaining some revenues...
I'm not sure twice really counts as "every so often".
The first was part of the Copyright Act of 1976. That extended the term from 28 years with the possibility of one 28 year renewal to life of the author + 50 years, or to a fixed term of 75 years for anonymous works and for works made for hire.
While Disney certainly was in favor of this change, the driving force behind the 1976 Act, and its term extension, was to bring US copyright law into closer agreement with that of most of the rest of the world in anticipation of the US joining the Berne Convention. Berne required a minimum of life of author + 50 years.
Many (most?) other countries don't seem to have the notion of a "work for hire" in the sense that the US does. In the US, when an employee creates a work as part of their job the employer is the author for copyright purposes and is the sole owner of the work. Outside the US, the employee is the owner of the copyright, and all the employer might get is a license to use the work.
Because the author, not the employer, retains copyright, most of the world doesn't need a separate term for corporate works. In the US, where the corporation is the author, life + 50 years could be indefinite since the life of a corporation is indefinite. Hence, the need for a fixed term for corporate works. If you want that to approximate the effective term of corporate works in the rest of the world, 75 years seems reasonable. I would guess that most of the time it works out to shorter than it would be if it were life of the human who actually made the work + 50 years.
The second was the Copyright Term Extension Act of 1998, which changed the term to life + 70 years for non-corporate works, and for corporate works to either 95 years after publication or 120 years after creation (whichever was shorter). Disney pushed for this change, although a big part of what sold it to Congress was again bringing the US into alignment with others, specifically with Europe which had gone from life + 50 to life + 70 with the "Directive harmonising the term of protection of copyright and certain related rights" in 1993.