Ask the Physicist!

Do you have a question related to physics? Since 1999 I have answered more than 7000 questions on line and many more by brief email. Please read the groundrules for the site. You can browse older questions through the categories link above or use the site-wide search to explore the full archive. If my answer is to your liking, please consider making a donation to help support this service.

Over the years I’ve answered thousands of physics questions, and many of those answers are organized into topic categories such as mechanics, relativity, electricity and magnetism, optics, and quantum physics. The categories link at the top of every page leads to this organized archive, making it easy to browse older questions by subject or explore areas of particular interest.

For many years I taught physics at the university level and have continued that work here by answering thousands of questions from readers around the world. My background includes advanced degrees in physics and decades of experience in teaching, research, and public outreach. You can read more about my training and career on the The Physicist page.

Policies:

Questions which

violate groundrules,
I consider to be "off the wall",
are not likely to be of general interest to the many people I know read the answers, or
do not include a valid email address,

will be discarded.

If your question is clearly astronomy or astrophysics, particularly detailed questions about black holes, stellar evolution, dark matter or dark energy, the big bang, etc., areas in which I am not expert, I may not answer. If you google ask astronomer or ask astrophysicist you will get lots of possibilities. I recommend NASA's Ask an Astrophysicist. Another good place is Curious about Astronomy?
Finally, I am not a psychic! Look them up, psychic and physicist.