From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: To: 9fans@cse.psu.edu Subject: Re: [9fans] Plan 9 from Bell Labs - Frequently Asked Questions [FAQ] From: "Russ Cox" In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Date: Wed, 9 Apr 2003 12:36:09 -0400 Topicbox-Message-UUID: 8dad25d0-eacb-11e9-9e20-41e7f4b1d025 > Subject: Is the cross product of two vectors a vector? > > No, it is not, and the fact that people treat it as one is the problem. The > *geometric object* that is the closest thing to the c.p. is a skew tensor > (practically the same as wedge product), which (only) in 3D has Cartesian > components that resemble those of a vector, *except* that this pseudo-vector > *flips* under reflection (unlike a genuine vector). Unfortunately, > physicists have been trained to express Maxwell's laws as a relationship > between a genuine vector (field) and a c.p., which means that that > expression of those laws *changes* under reflection, something that > physicists are *not* taught and which appears to have been overlooked in the > analysis of the (nonconservation of) parity experiment. > I had to quote Douglas Gwyn verbatim on this, because I have no *ucking clue > what he's talking about -- Steve ☺