4 ms·
I'm always perplexed when just a raw wikipedia article is posted here with no context or commentary about it.
by rtkwe 8y ago
I'm always perplexed when just a raw wikipedia article is posted here with no context or commentary about it.
- Scene_Cast2 8y agoWell, if people upvote it... I guess it's more like "hey look, this article is really cool", without a direct application to most people's daily work.
- jetrink 8y agoAgreed, sometimes it's obvious why a particular article caught the poster's attention, but for this one, it would be nice if they gave some context. How did they hear about it? Is there an interesting fact hidden in the article that would not jump out to the uninitiated?
- teucris 8y agoNo idea why OP found it interesting, but this really caught my eye: “Given the properties of bilinearity, orthogonality and magnitude, a nonzero cross product exists only in three and seven dimensions.”
- isoprophlex 8y agoexactly this! these marvellous rarities are what makes mathematics so divinely interesting. why only 3 and 7? what's the relationship with quaternions and octonions? in a similar vein, https://en.m.wikipedia.org/wiki/Exceptional_object https://en.m.wikipedia.org/wiki/Exceptional_object
- deehouie 8y agoMy experience with HN is, there are some very thoughtful mathematicians engaging in deep research around here. Some of the posts here may make no sense to 99% of the readers ("why on earth should I care about 7-dim stuff, I just don't give a damn"), but it may just be the lightning strike needed for someone to make important breakthrough in certain area of mathematics.
- arbitrage 8y agoThis property of 3/7 dimensional cross product is not terribly insightful. It's taught to undergrads. It's not really a hallmark of advanced mathematical research.
- nilkn 8y agoThis is definitely a bit niche, but at first blush it's highly bizarre that you can get a natural cross product operation in three dimensions... and not again until seven. And then never again after that. It's a peculiar and interesting (if not very useful) fact that is probably within reach of a sizable chunk of the audience here.
- oarabbus_ 8y agoSee, now that you've said it, it really is quite interesting. But would that insight be plainly obvious to most? I highly doubt it. I have an MS in an engineering discipline, and this was not obvious to me until you said it. Maybe I'm just dumb (I kid - I would have picked up on this while in undergraduate or grad school, when I could really throw my weight around in mathematics, but like anything else, linear algebra is a muscle that wastes if you don't flex it) but really there should be some commentary associated rather than a raw article - the parent comment is totally right. I could link HN to pentation or the Ackermann function; they're interesting, but useless without context.
- newen 8y agoCross products are taught in high school. And I'm sure by college, a good amount of people are aware that four dimensional cross products are not possible. And like me, most of them probably thought four and higher dimensional cross products don't exist. So when I saw 7-dimensional cross product, I got pretty interested.
- oarabbus_ 8y agoConvex optimization is also taught in high school. Organic chemistry, biochemistry, discrete math, probability, and statistics too. I fail to see your point.
- newen 8y agoMy point is that cross products are really really really simple and for some reason you have this notion that cross products are something complicated.