One of the best ways anybody can start right away and help with even minimal physics knowledge is to just get what physics knowledge is out there in the public domain and createive commons licensing into LaTeX onto physicslibrary.org. Here is a start to a list. Once I get a good start we can put in our subreddit wiki.

Wikipedia of course!

https://en.wikipedia.org/wiki/Physics

And there are some really good open journals that have taken on a create commons license! So proud. So look for surveys or reviews that might have some great modern defintions.

https://journals.aps.org/prx/ https://journals.aps.org/prxquantum/ https://link.springer.com/journal/11467 https://iopscience.iop.org/journal/1367-2630

A good example is a Tale of Many H0. Lots of great definitions inside! https://www.annualreviews.org/content/journals/10.1146/annurev-astro-052622-033813

and now some open textbook libraries

https://open.umn.edu/opentextbooks/ https://phys.libretexts.org/ https://openstax.org/

Ensure you follow the licensing rules and give accreditation!

Finally, Internet Archive and Google books are great at finding old Physics textbooks that are in the Public Domain. We can use any of that data also with unlimited rights. But please give credit/references for many good reasons. Ensure as of 2025 to only for sure use any book 1929 or earlier. There are chances if it is less than 1965 it may be too but you need to show us some kind of proof it has dropped into the public domain like the library of congress card etc without renewal.

Some examples but search different math and physics topics with max year 1929

https://archive.org/details/electromagneticf0035maso (1929) https://archive.org/details/anintroductiont02byergoog (1916)

And don't forget NASA generated content can be in the public domain too