Wikipedia:Reference desk/Archives/Miscellaneous/2009 February 7

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February 7

Plane passing through diagonal

Can you explain what this means and give an answer if possible: A cube is cut in half along a plane that passes through the diagonal of one of its faces. What is the shape of each half of the cube? Thanks for any help!! —Preceding unsigned comment added by 124.184.97.118 (talk) 00:37, 7 February 2009 (UTC)

This sounds like a homework question -- it certainly isn't a question you came up with on your own, since you ask what it means. We're not going to do it for you, but this really isn't a very hard one! You know what kind of a shape a cube is. You read our article on "diagonal" to find out what it means, and from that point on, you should be able to figure out the rest. -- Captain Disdain (talk) 00:53, 7 February 2009 (UTC)

Well it's rather the wording that has me slightly confused. My friend and I aren't sure whether or not the answer is triangular prism —Preceding unsigned comment added by 124.184.97.118 (talk) 01:00, 7 February 2009 (UTC)

This sounds like a homework question, but it also sounds like you are having trouble understanding the question. Instead of giving you a simple answer I will try to help with your understanding of the question: A cube has six square faces. I suggest you take a look at the diagonal article to decide what "the diagonal of one of its faces" means. Now imagine placing a knife on the diagonal and cutting the cube in half. The cut will be in the "plane that passes through the diagonal". You will end up with two identical parts which have a shape that your teacher should have mentioned in class. Astronaut (talk) 01:09, 7 February 2009 (UTC)

I was able to find the name of the thing and a picture of it by starting at the article "Solid geometry", but it wasn't easy. --Milkbreath (talk) 01:23, 7 February 2009 (UTC)

Or, make a Play-Doh cube and cut in half as described. hydnjo talk 01:28, 7 February 2009 (UTC)

The question is a bit trickier than it first appears. The phrase "cut in half" in normal english usage does not mean "divided into identical parts." Instead, it often means "cut into two parts." But this meaning results in ambiguity. It might be fun to find the weakest definition of "cut in half" that results in an unambiguous answer. -Arch dude (talk) 02:34, 7 February 2009 (UTC)

Without giving anything away: in this case, the cut would result in 2 objects identical in every respect, so your point is of not much relevance to this question. The question implicitly assumes the 2 parts are identical, in any event, because it asks for "the shape of each half", not "the shapes of the two parts". -- JackofOz (talk) 05:59, 7 February 2009 (UTC)

The diagonal of a face is just a line, there are infinitely many planes passing through any given line, each will give different shapes when cut along. I think the question means a plane passing through the diagonals of two opposite faces. --Tango (talk) 15:27, 7 February 2009 (UTC)

That is exactly what "cut in half" means. hydnjo talk 15:36, 7 February 2009 (UTC)

I know all that. I was trying to guide the OP to creating the following problem for himself and then solving it:

• A cube is divided into two parts of equal volume by a plane that includes the diagonal of one face. Prove that the two parts are isomorphic.
• Bonus problem 1: Prove or disprove: for any division of a cube into two equal-volume parts by a plane, the plane includes the center point of the cube.
• Bonus problem 2: Prove or disprove: for any division of a cuge into two equal-volume parts by a plane, the two parts are isomorphic. -Arch dude (talk) 15:59, 7 February 2009 (UTC)

But the OP is already confused trying to understand the original problem. Why add a layer of complexity and start using the phrase 'cut in half' in a way that, apparently, is common in your vernacular, but is not how the OP will be expected to use it in school or mathematical contexts? And may not be a use of the phrase in their vernacular at all? 79.66.57.25 (talk) 14:59, 8 February 2009 (UTC)

Plane steering

The question above (about moving aircraft on the ground) got me thinking. How do pilots steer large commercial aircraft when on the ground? And are the wheels driven/powered in some way? Astronaut (talk) 01:22, 7 February 2009 (UTC)

See "Taxiing". The wheels aren't powered. They steer with the nose gear and the rudder, and some planes apparently have separate brakes for the two sets of wheels under the wings, allowing steering by differential braking, like a tank. --Milkbreath (talk) 01:29, 7 February 2009 (UTC)

From Taxiing: "The aileron and elevator controls are used to prevent wind from lifting the tail or a wing." I wouldn't think this is a problem with large aircraft, but knowing the wind direction while taxiing is a concern with smaller aircraft. Taggart.BBS (talk) 10:37, 7 February 2009 (UTC)

Generally, the rudder control pedals are also connected to the nose-wheel steering mechanism. There are typically short pedal extensions on the tips of the rudder pedals that control the brakes in the main wheels. So depending on your speed there are FOUR ways to steer: The rudder works at high speeds, the engine thrust can be adjusted separately for each engine, the nose wheel can be steered and the main wheels have separate brakes. All of this makes a big airliner surprisingly manouverable on the ground. Smaller aircraft probably have nose-wheel or tail-wheel steering connected to the rudder controls - but they may not have differential braking. SteveBaker (talk) 04:32, 10 February 2009 (UTC)

"We're through the looking glass people"

What is the origin of the phrase "We're through the looking glass, people"? Is it the Simpsons or is that referencing something else?

When The Simpsons used it, it was an allusion to a line in the movie JFK (1991): http://www.youtube.com/watch?v=FhBm4kprCkk#t=113

And what does it really mean, anyway? Because the Alice in wonderland stuff doesn't really fit in the context of "we've uncovered a conspiracy", surely?

--213.107.112.194 (talk) 11:07, 7 February 2009 (UTC)

As you guessed, it is a reference to Alice in Wonderland, specifically the second book Through the Looking-Glass. It means just "everything is different", and if you uncover a big enough conspiracy, that's the way it feels. --Anonymous, 11:20 UTC, Fnorduary 7, 2009 (copyedited later).

Excellent, thanks. But do you know if the phrase was used in this way before the Simpsons? Is it commonly used in America? Would it always be used sarcastically, to mock conspiracy theorists etc, or would people say it seriously? --213.107.112.194 (talk) 14:52, 7 February 2009 (UTC)

Being an American, I think I can say that the phrase "through the looking-glass" is a commonplace part of an American's cultural landscape, much more than "at the back of the wardrobe", for example, which would be inscrutable on at least two levels to many, and would be recognized as a Britishism by the rest. We love Alice as much as y'all do. We'd tend to leave out the hyphen by mistake as our friend here did, because the word is "mirror" over here, and there is no such thing as a looking-glass. In fact, when I read it as a child, I assumed the word was another of Carroll's fancies. That said, I think more Americans would turn to Dorothy than to Alice, and say "We're not in Kansas anymore" (another misquotation) to convey a sense of unexpected otherworldliness. The writers of the Simpsons are shockingly intelligent, and they aren't afraid to knock bodies down with it, so look out. --Milkbreath (talk) 15:22, 7 February 2009 (UTC)

The version I prefer is "Somehow, I don't think we're in Kansas anymore, Toto". Another way of saying the same thing is referring to a weird and different place (either literally or figuratively), as Oz. StuRat (talk) 16:47, 7 February 2009 (UTC)

That's entered the lexicon as "the Oz factor" [1]. And yes, I am the ruler of that land, so watch your step when you come visiting.  :) -- JackofOz (talk) 02:48, 8 February 2009 (UTC)

Does that mean you're a little guy hiding behind the facade of a powerful man ? StuRat (talk) 21:31, 8 February 2009 (UTC)

Have that man killed, Rodney! -- JackofOz (talk) 02:07, 9 February 2009 (UTC)

Have we moved on from the Wizard of Oz to the Wizard of Id, as in "The peasants are revolting !"..."I'll say they are !" ? StuRat (talk) 21:01, 9 February 2009 (UTC)

Actually, that Simpsons episode (Grampa vs. Sexual Inadequacy) was referencing JFK, when Jim Garrison says it in a similar scene. Adam Bishop (talk) 15:52, 7 February 2009 (UTC)

Even when I was a child in England (nearly 50 years ago) 'looking-glass' was a very old-fashioned word. --ColinFine (talk) 23:36, 8 February 2009 (UTC)

VHS recordings made in the UK

Is there a "machine" that can play recordings from UK TV on Canadian TV ?? —Preceding unsigned comment added by Wishtoknow (talk • contribs) 16:48, 7 February 2009 (UTC)

I think they are called multisystem VHS players. Your UK tv recordings are in PAL, and the Canadian TV are running NTSC. A quick google will locate sites that sell the required converters or all-in-one machines. --Mdwyer (talk) 19:55, 7 February 2009 (UTC)

On the other hand depending on how many you have you might be better off getting them converted. VHS to VHS seems to be about $10 and VHS to DVD about $15, both for 3 hours. As converters run around $100 that might be a better option if you have only a few tapes. CambridgeBayWeather Have a gorilla 23:33, 7 February 2009 (UTC)

Getting a mortgage -- extend line of credit?

Hi all,

I'm looking to get a mortgage for a home purchase soon, and I have pretty good credit. One thing that I was wondering, though, would be whether I would be more eligible for lower rates if I got my credit line extended for my credit card. Do they look at that? If I were able to get a larger line of credit, would it affect my credit rating?

Thanks, — Sam 146.115.120.108 (talk) 20:30, 7 February 2009 (UTC)

It's very complicated, credit providers don't just look at a single number (your "credit rating") they look at the actual facts of your case. I think it's impossible to say what effect getting your credit card company to increase your credit limit would have, if you want someone to make a guess you need to ask a professional financial advisor who can look at all the facts of your case and will know what banks where you live tend to look for. Increasing your credit limit will decrease your ratio of debt to credit available, which is a good thing (it means you're managing your money well), but it will also increase your total credit available, which is a bad thing (it means you could very easily get into lots of debt). Which of those is more significant? I have no idea. --Tango (talk) 20:35, 7 February 2009 (UTC)

I am actually in the same position as you, Sam, at the moment. I considered the very same question. What I found is that if your credit score is already about 740 or higher, you don't gain much advantage from making it higher still, because the best mortgage rates are typically available to anyone with a score above 720 or 740. So if your credit score is already in the high 700s or higher, you won't gain any advantage by changing your circumstances. If your score is below about 720, you could gain a marginal advantage, but you have to weigh possible negatives, as Tango points out. If your score is below about 720, you might consult widely available publications on credit repair, which can help you to calculate the effect of various actions on your credit. Marco polo (talk) 21:21, 7 February 2009 (UTC)

The only real "credit repair" options are removing incorrect data from your credit report. If you credit report is accurate and you are just a bad credit risk, there's not a lot you can do other than look after your money better and come back in a few years. --Tango (talk) 21:36, 7 February 2009 (UTC)

Finding out credit rating

What is the best way to find out ones credit rating (in the US)? I remember hearing sketchy stuff about freecreditreport.com. Also, I know that there is the website annualcreditreport.com set of by the gov't, but from there I only seem to be able to get reports as to whether there are any red flags in my report, not my actual score.

Is there a safe, free way to get my actual credit score? Or, if not, does anyone recommend a service that is cheap and won't sign me up for years of credit protection or whatever?

Thanks! — Sam 20:36, 7 February 2009 (UTC) —Preceding unsigned comment added by 146.115.120.108 (talk)

The report to help you spot if anything is wrong is the most useful. Credit scores don't mean much, banks don't actually use them, they look at the actual report and do their own calculations. Also, they're probably not going to tell you what the required credit score is, so even if you know what scoring algorithm they use it doesn't help. You may find Credit score useful. --Tango (talk) 20:47, 7 February 2009 (UTC)

If you go through the site annualcreditreport.com, you will be offered the opportunity to purchase a full credit report from one (or more) of the big three credit-reporting agencies for a fee of $5 or $6. I did this recently and found it well worthwhile for the peace of mind. Also, if you are interested in a mortgage, you can approach a mortgage broker or lender and request preapproval. They will usually do this for free, and, in my case, my preapproval letter confirmed my credit score. In my house hunt, I have found that some sellers will not even show a house to buyers who are not pre-approved for a mortgage. So getting preapproval might be a smart step. Marco polo (talk) 21:30, 7 February 2009 (UTC)

Pre-approval is a very smart step since without it you can't be sure how expensive a house you'll be able to get. You need to know your price range before you can go house hunting. --Tango (talk) 21:37, 7 February 2009 (UTC)

Note that annualcreditreport.com grants you a free credit report (per the government's requirement, rather than some "sign up for a free trial" service) from each of the big three annually. You can purchase a more in-depth report as per the above, but can do a quick check at no cost. — Lomn 00:49, 8 February 2009 (UTC)