As befits our information age, and anything that has to do with Einstein, we are now deluged with a blizzard of detail, commentary, speculation, polemic, and downright silliness surrounding the recent OPERA experiment (the one which claims to find neutrinos arriving, after a trip from Western Switzerland to Central Italy, earlier than expected.) I aim to avoid adding to the confusion, and will only post what I feel is both clear and reliable. Right now I have little new to say that fully satisfies both criteria. However, later in this post you will find a summary of the posts I’ve put up so far, to help you navigate what’s already here.
One goal of this site is to create a space where lay people with a range of backgrounds can ask questions. While I deeply appreciate that many of my physics colleagues are reading my posts and some are commenting on them — along with highly educated non-physicists who’ve been asking very sensible questions and making insightful comments — my one concern right now is that the level of comments is so sophisticated that a person less familiar with the physics will feel intimidated about asking more elementary questions. So I’d like to ask that the comments on this post be limited to those who feel there are some very, very basic points about the OPERA experiment, and the relevant background, that they just can’t follow.
I’m sure I won’t have time to answer all of your questions, at least not right away — and sometimes an answer won’t be possible without an extension of the website. But just knowing what your questions are will help me decide what material to add to this website, to make it more useful for the more general reader. So: Please Ask Away. [Experts: please see additional comment below]
Finally: the summary of the posts so far.
- A step-by-step explanatory sketch of how one obtains a neutrino beam, starting with a proton beam. (9/23/11)
- An explanatory sketch of how one can detect neutrinos — not easy because most neutrinos sail right through matter without doing anything, but not so hard for that rare neutrino that actually does hit something. [Will be updated with figures] (9/26/11)
- A discussion of supernovas and neutrinos, explaining (toward the end) why observations of the nearby supernova in 1987 put a strong limit on the difference between the speed of light and the speed of neutrinos – at least for neutrinos whose energies are 250 to 1000 times lower than those measured at the OPERA experiment. (9/20/11)
- A general commentary on the OPERA experiment and thoughts on how one must approach a potentially revolutionary (but probably wrong) experimental result. (9/22/11)
- A more detailed reaction to the OPERA experiment’s public presentation, including three remarks on the subtleties of the experimental result, and some cautionary remarks on jumping to theoretical conclusions. (9/23/11)
If you find these posts are too advanced for you or leave a burning question unanswered, feel free to ask questions in the comment section below. Again, I can’t promise an answer, but will try to answer as many as possible.
A last comment for experts: if you see a question from a layperson sitting here, and you feel you can answer it, I certainly won’t stop you. But I am afraid I must reserve the right to delete the answer or to edit it if I feel it isn’t both correct and crystal clear, as well as free of jargon to the extent possible. So please, if you give an answer, try to make sure you are very comfortable with its form, that you’ve proofread it very carefully for clarity, style and content, and that if possible you’ve tried it out (now or previously) on a non-expert. Obviously this is a tricky business as one can answer any question at multiple levels; just please make your answer something that a substantial segment of the public could follow. [And if you see what you think is a mistake in one of my answers, please let me know.]