Version Date: 12 Sep 1998

Usenet Physics FAQ

Sir Isaac Newton magnet particle tracks

This is the web version of the Usenet Physics FAQ (Frequently Asked Questions). Its purpose is to provide good answers to questions which have been discussed often in sci.physics and related usenet newsgroups. The articles in this FAQ are based on those discussions and on information from good reference sources. That does not mean that they are always perfect and complete. If you have corrections, updates or additional points to make please send E-mail to me, the editor, Scott I. Chase at You can also raise the subject in the newsgroups if you really think you have something new to say. If you want to write up an article following a discussion about a subject not yet covered here then feel free to send it to me, but please do not use this address to ask new questions. Ask them in the appropriate newsgroup instead.

If you are new to the Physics newsgroups, welcome!, please read the article: An Introduction to the Physics Newsgroups It will help you find the right newsgroup for your questions and will give you other crucial advice about appropriate netiquette for these groups. Above all you should check carefully to see if your questions are answered in this FAQ before posting.

This FAQ was created by Scott I. Chase in 1992. The web version was created, maintained and enlarged by Michael Weiss and Philip Gibbs. It is now edited again by Scott I. Chase. Others who have written for the FAQ are credited at the top of the items they submitted while many more who have made smaller contributions have been thanked privately. Since 1996 the relativity articles have been separated into a supplementary Relativity FAQ which is edited by Chris Hillman and Nathan Urban.

This FAQ is currently available from these web sites:

Japanese language version:
Thanks go to John Baez, Philip Gibbs, Alan Cairns, Dave Edsall, Chung-rui Kao, Matthew Parry, Jon Butterworth, Harald Falkenberg, Johan Wevers and the various organisations for hosting us! If any other non-commercial sites would like to mirror this FAQ in countries not represented above, please contact

The FAQ is not available in text only form and is no longer posted to the usenet groups. This is because it is too big and some articles use images and equations which cannot be transformed into text. The full Physics FAQ in HTML form (including the Relativity FAQ) can be downloaded as a single large archive file by FTP from You can install it on your local disk and view it from there with a suitable web browser.

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Index of Subjects

Administrivia and Reference

General Physics

Particle and Nuclear Physics

Quantum Physics

Relativity and Cosmology

Relativity and Cosmology questions are answered in the Relativity FAQ

Related FAQs

There are many other places where you may find answers to your question. This is a list of other FAQs and answer archives which are related to physics.