Last updated by DK, 2018.
Original by Philip Gibbs, 1996.

Useful Physics Resources on the Web

The world wide web is a rich source of information about physics. The Physics FAQ is not the place to put together a complete list of them, so I will concentrate on databases that are packed with useful content such as physics news. (Editor's note: many of the original links that this page referred to no longer exist, but I have updated the ones that are there.)

American Institute of Physics: The AIP publishes and archives a number of informative newsletters. This is a good place to look for brief reports on recent discoveries.
High-Energy Physics Literature Database: This is a good site to search for the latest in literature on high-energy physics, as well as more general physics.
The American Physical Society: They publish some of the most important Physics Journals such as Physical Review. On-line access to those is restricted, but the News Room is a useful resource.
The Institute of Physics: Another journal publisher with a News section.
Los Alamos E-print Archive: These archives are a standard means of communicating new papers in physics disciplines. Unfortunately, the lack of real competition for archives in this e-print area is perhaps what has given the archive's maintainers a very exclusive attitude that probably prevents much good research from being published at arxiv. Even career physicists can find it hard getting their papers onto this archive, but that doesn't imply that what is there is always good physics.
Particle Data Group: This is where you will find the Review of Particle Physics containing values for all manner of physical constants. They have also put together an educational feature called The Particle Adventure.
John Baez's Papers: Useful information on developments in physics including the archive of This Week's Finds in Mathematical Physics. John has also put together a tutorial on General Relativity.
National Institute of Standards and Technology: Another site with convenient tables of physical constants.
The Laws List: An alphabetically ordered list of laws and principles of physics by Erik Max Francis.
Eric Weisstein's World of Physics: Another alphabetical list of physics definitions and equations by Eric Weisstein.
MacTutor History of Mathematics Archive: This is an extensive archive of historical information which has good coverage of physicists and astronomers as well as mathematicians. Go straight to the search page and enter the name of your favourite physicist or topic.

If you still have not found what you are looking for, try the usual search engines such as Duck Duck Go, Start Page, Qwant, or, if you don't care about privacy, Google. It is also a good idea to search old usenet posts using Google Groups.

Note by Editor DK, 2018: don't take too seriously the top-voted entries on physics-discussion sites such as "Physics Stack Exchange", or the conversations on "Physics Forums". The answers given on these sites are often supplied by members who are driven only by a desire to raise their "site star" rating, and such answers can tend to be what is naively believable rather than what is correct but possibly sophisticated and difficult. Also, a form of voting on such sites gives rise to an abuse of power, such that long-time members can vote down good answers, while new members, who might have vastly more knowledge, are not able to vote those good answers back up again. The moderators of these sites have the power to close down entire conversations if those conversations start to conflict with what those moderators believe to be true; then, if someone tries to restart the conversation under a new entry, the same moderators will close down the new conversation with the words "This question has already been answered". I think these moderators place an extreme censorship on the web today when it comes to interested people wanting to discuss physics.

Another site not to take seriously is Wikipedia. Wikipedia is probably fine if you want to know the population of Bolivia, but you should take it with a heavy dose of salt if you're looking to learn physics. The reasons are several:

Wikipedia's entries are generally a reflection only of widespread opinion, rather than knowledge. (That's also true of "Physics Stack Exchange" and "Physics Forums".) The entries also tend to reflect the opinion of the last man standing, after all the rest have given up the battle to supply corrections that keep getting overturned by louder voices.
Because a typical entry tends to have several authors, there is generally no oversight into whether the notation used is self consistent throughout the entire entry. Each contributor will swear by his own contribution's notation because he saw it in a book, without necessarily realising that different books have different notations and conventions that conflict when thrown together onto one page.
Wikipedia entries need have no hard-won scholarship behind them. They are reviewed by Wikipedia contributors, who are probably more likely to be "wannabe" experts rather than real experts. Real experts are probably seldom bothered to waste their time competing with non-experts over who can last the longest in a Wikipedia battle.
Wikipedia has done a good job in redefining knowledge to be what is most commonly believed by the loudest voices rather than what is agreed upon by specialists or what is correct.
Wikipedia contributors seem often have an obsession with listing or labelling irrelevant and spurious concepts and jargon, that serves only to obfuscate what should be a simple subject.
Wikipedia redefines fads as canon. A good example is its favouring of abstruse and pretentious mathematics in pages on physics where that maths is simply not relevant or not necessarily correct. Mathematical obscurity is a modern fad, and the more abstruse you can make a Wikipedia page on physics, the more likely it will be left alone by other contributors, who simply get cowed into accepting the new contribution. A non-physics example of this is the oft-found replacement of the date appellation "BC/AD" with "BCE/CE". Another non-physics example is re-spellings of place names according to what is currently popular. Another example of such faddism is an obsessive use of macrons that no one actually uses, such as in writing the modern Maori language.
Wikipedia belies the idea that knowledge should be above politics; for example, its extreme political correctness and marked left-wing philosophy can only get in the way of presenting facts. That tends not to affect its pages on physics, but the problem is always potentially present as a way of rewriting history, be it physics or otherwise.