@TanMath : Phys.SE only allows a limited number of res. recom. qs for various reasons, cf. several meta posts, e.g. they have no unique answers, they are primarily opinion-based, and they tend to be list of links. Res. recom. qs are easy to pose and easy to answer. For this reason it seems fair to make them CWs. It is much better (and more interesting for the reader to read) if you ask an actual physics question.
See also: Why are "shopping list" questions bad?, http://blog.stackoverflow.com/2011/08/the-future-of-community-wiki/
TL;DR
I do feel that our book/list policy can be revised. Not removed, but loosened up considerably. For book questions, this can be done by making sure that answers include...
@vzn I have synesthesia, and my favourite colour is blue. The letters that appear blue to me are o, r, b, e. I only chose 3 of those letters because the number 3 also appears blue to me. weird.
@obe I can sort of imagine associating colors to objects inside my head, but I cannot imagine to automatically see that color when encountering the object/thought. You don't actively create the color, it's just there, right?
they should try to do brain imaging on "synasthesiasts". it seems it would turn up something quantifiable. a great neurobiological study. also, the list of famous ppl with synasthesia would be quite interesting.
@ACuriousMind Ideas and abstract objects also have colours, therefore words can be of some colour, though the idea or object that they represent can be a different colour.
@FenderLesPaul those who have or studiy it do not necessarily see it as "needing treatment". its thought to be mostly benign. maybe it can be explained in some strange evolutionary terms. like a neurological appendix so to speak? dont know. science barely recognized it until "recently" (last few decades) and (afaik) it was scientifically rejected for awhile. shows hows how science evolves. a paradigm shift within our generation.
@FenderLesPaul be careful how you interpret that. some weird noises or other sensations "bother" me or others too. but so what? its part of being human eh? synesthesiasts just seem to have different sensations. but maybe (conceivably) they are helpful or maybe even "adaptive" in some way.
@ACuriousMind Your name has 3 words in it, you're not a single colour. Though your existence, separate from your name has a single colour. Which one do you want to hear?
That is because A, C, M are those colours, not in order, though barely red.
The skull.
I'm trying to figure that out, I've had a lot of coincidences before, though I can't tell if the first impression has an effect on the objects colour/aura.
Though those letters are still of that colour, regardless of the image.
If you look at the night sky, sometimes you can see stars in your peripheral vision, though when you turn to look at them, they dissapear because your central vision is insensitive to their light.
@0celo7 I always amazes me how people can get hung up on such things...unless you're in the non-commuting case Qmechanic alludes to, who the hell cares where the damn $\mathrm{d}x$ stands?
@obe I do. I saw the '85 return of Halley's comet on a clear and very dark night, but even so saw it mostly with my peripheral vision. It was widely considered a disappointment.
There are a lot of questions that have totally incorrect premises, ask for "a formula" for something where no such formula exists (e.g. "given the gravitational acceleration, what is the formula for position?"), or don't even make syntactic sense.
Several times, I've responded to these questions...
I posted an answer to Why is any number divided by 0 is infinite?; it was rather too short, I confess [but correct], & this might prompted someone to downvote me; my rep got decreased by 2. Then I thought, why to waste my rep?? I deleted my answer.
Then I saw, it was migrated to MSE. I thought ...
@0celo7 If you think someone is encouraging posts that have been ruled off-topic by the community (i.e. not a personal opinion) by answering them, the correct way to go is to flag them for moderator intervention. It's okay if you tell me about it too, but it's not like it's my place to "handle" this somehow (or decide to refrain from doing so)
Personally, I think his answer is well within bounds---he's not solving the problem for the guy, but trying to help him out nonetheless. I know that this is a delicate issue, though, so I won't argue too much with you if you disagree.
@DanielSank Well, nobody says you should write all forms with $\mathrm{d} $'s, or even could :P
Rep Cap Take one throw-away answer to a pop-sci level question, stir in a dose of ``Hot questions sidebar (tm)'', and allow to rise on a warm counter under a damp tea towel. Bake overnight. Makes one serving.
sometimes I felt like I need to do something else to fix my bad question problems
this is because I have at least 3 questions (2 deleted by community) that are based on a very wrong premise and thus cannot be fixed by improving the question (since any improvement will necessary mean completely changing the question)
I am also doing some reading on the physics stack exchange question FAQ since I am so late at discovering that the multiverse is considered speculative thus off topic (which is how I cost myself one step closer to the question block 3 weeks ago in a deleted question by community)
@Qmechanic That would be bad since there are some answers that rely, for example, on Feynman diagrams, for which there is no way to include them into the post in another way
@Qmechanic yeah, I was just going to point to that as an example of why text should by typed, not included as images. (Though one can always use SE imgur upload, which fixes that issue, technically)
@Qmechanic that's regular imgur AFAIK. SE imgur images are retained at least as long as the corresponding SE site exists. (I think.)
Yeah, they're different: SE imgur upload uses the i.se.imgur.com domain, whereas the regular one is just i.imgur.com. They are controlled by the same company, same web service, etc., but SE definitely has a special arrangement of some kind for archiving of images on the se.imgur.com domain.
I have unilaterally closed and deleted the "link rot" question. It certainly predates our current homework policy, but in the rotted condition it was doing no one any good.
@Secret Stack Exchange can host it's ow image at this point (a feature more than a year old now, I think) and the insert image tool copies them there. So that problem should be limited to only quite old questions.
If a person falls into a certain sized black hole they accelerate very fast, which increases the g forces on them.
These g forces flatten the person out into a pancake.
As the person falls further into the BH the acceleration is less even and they turn into spaghetti.
Is there a puff pastry poin...
@Danu At the time I was learning proper calculus and I stopped writing the $d$ because I realized it didn't mean anything. Then later when I learned about forms I started putting it in again because it did mean something.
Is the proof "straightforward" as in "All isometry algebras must be subalgebras of this one, and it doesn't have 8 or 9 dimensional subalgebras", or is it more convoluted?
"Theorem 11.2 : The only Einstein spaces ($R_{ab} = \Lambda g_{ab}$) with a group of motions G_r, $r\geq 7$, are the spaces of constant curvature which admit a $G_10$"
"Further we can see that there are no spacetimes with a $G_r (r \geq 7)$ containing an electromagnetic field with $C=0$"
"The only possible metrics with exactly a $G_7$ are a perfect fluid solution with an $I_3$ of spatial rotations at each points, and a pure radiative solution with an $I_3$ generated by null rotations"
Now I am not exactly sure if that's true
Seems like it is, but it is not said in so many words
Hm, the most powerful general result I can find is that the identity component of the isometry group of a Lorentzian manifold is the product of an Abelian, a compact, and a oscillator, Heisenberg or SL(2,R) group.
Alas, that doesn't say anything about the dimension
What is the highest number of symmetries (Killing vectors) that a spacetime can have without being maximally symmetric? From what I can see, it seems to be 7 (which includes the Einstein universe and some pp-wave spacetimes), but the theorems used (in chapter 11 and 12 of Stephani's "Exact Soluti...
@Slereah Why didn't you formulate it as an actual question, i.e. "What is the spacetime with the highest number of symmetries that is not maximally symmetric?"
See also: Why are "shopping list" questions bad?, http://blog.stackoverflow.com/2011/08/the-future-of-community-wiki/
TL;DR
I do feel that our book/list policy can be revised. Not removed, but loosened up considerably. For book questions, this can be done by making sure that answers include...
I posted an answer to Why is any number divided by 0 is infinite?; it was rather too short, I confess [but correct], & this might prompted someone to downvote me; my rep got decreased by 2. Then I thought, why to waste my rep?? I deleted my answer.
Then I saw, it was migrated to MSE. I thought ...
