Wikipedia:Reference desk/Archives/Science/2012 July 25

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July 25

Angle of Vega in Summer Triangle over time.

I don't have any facility at all with the sources needed to answer the following, so I cannot really begin. The question I have is (for somebody who might have such facility) whether there is a date specific (nearest ours) when the angle of the star Vega was or will be (very nearly approximately) right from the vantage point of the Solar System (say, specifically, from the Sun, if it is possible to be at all that precise based upon available data). Thanks if anybody has this in a source or from easy work from own knowledge.173.15.152.77 (talk) 02:41, 25 July 2012 (UTC)

By "right", you mean a right triangle (one with a 90 degree angle) ? StuRat (talk) 03:25, 25 July 2012 (UTC)

The necessary information is in our articles on Vega, Deneb, and Altair -- their coordinates and proper motions -- but it's more work than I'm willing to do right now. Based on a quick glance, though, it looks to me like it would have been in the past, and probably a few hundred thousand years ago. Looie496 (talk) 03:37, 25 July 2012 (UTC)

Yes, StuRat, I meant for the adjective 'right' to modify the distantly separated noun 'angle' in the sentence. That is a common way to describe Vega's position in the Summer Triangle, as at nearly a right angle to the two others. Thanks for that guesstimate, Looie496.

Does anybody know if those relative motions would be sufficiently close to constant for that information not to require adjustment on that timescale, assuming he is correct? Is there any chance this questionn has been asked and answered in the literature? It comes off as a recreational problem more than anything else, but stranger things have been done with academicians' time in journal articles (I recall that somebody wrote a chemistry article purporting to compute that the Heaven described in the Bible would be hotter than the Hell, for example).173.15.152.77 (talk) 23:38, 25 July 2012 (UTC)

Unless any of those stars is in a binary or multiple star system, then, yes, their proper motions should be constant enough for this calculation. StuRat (talk) 02:54, 28 July 2012 (UTC)

Transition hydrides

Hypothetically, what would be the transition hydride sequence/habit?

The main group, alkaline, alkaline earth, noble groups have the structure: 1, 2, 3, 4, 3, 2, 1, 0

What about the structure for the fourth period: 1, 2, 3, 4, 5, 6, 5, 4, 3, 2, 1, 2, 3, 4, 3, 2, 1, 0?

Or, perhaps: 1, 2, 3, 4, 5, 6, 7, 6, 5, 4, 3, 2, 3, 4, 3, 2, 1, 0?

What would be the most reasonable, hypothetical choice? Plasmic Physics (talk) 04:27, 25 July 2012 (UTC)

Neither. Transition metals don't fit into such a simple model. For the first, transition metals don't exhibit singular oxidation states per element. Nearly all of the transition metals have multiple oxidation states, and multiple hydrides, they form. Iron hydride for example has many different varieties. --Jayron32 04:49, 25 July 2012 (UTC)

Most elements exhibit multiple oxidation states per element. Oxygen can form two hydrides in which the oxidation state is not mixed or fractional: either oxidane or oxidanyl. I should mention that I'm talking about molecular hydrides, not ionic or interstitial hydrides. Plasmic Physics (talk) 05:05, 25 July 2012 (UTC)

Wow. Did you just use the word "oxidane" for "water?" I've never met a person who didn't use that word ironically. --Jayron32 05:16, 25 July 2012 (UTC)

For me it depends on the context, when I discuss molecular theory, I prefer "oxidane" when I talk about applied chemistry, I use "water". Plasmic Physics (talk) 05:26, 25 July 2012 (UTC)

In the FeH article, it is stated that there are three known FeH_x molecules. To follow the pattern of no unpaired electrons, it would be fair to say that the smallest value for iron would be 4, ferrane. Meaning that, FeH would be ferranylidyne. Plasmic Physics (talk) 05:21, 25 July 2012 (UTC)

Lets take into account the case of pumbane vs plumbanylidene. Even, though the latter is more stable at STP, the former is still the main hydride. Plasmic Physics (talk) 05:29, 25 July 2012 (UTC)

The best analogues to understand those differences in lead-hydrogen compounds would be to look to the difference in stability between methane and carbene. The article Carbene analog discusses lead analogues of carbene. --Jayron32 05:51, 25 July 2012 (UTC)

For the iron hydride FeH₂ and FeH₃ are only known at cryogenic temperatures in a noble gas matrix, so I am not sure you can call this a habit. FeH molecules are only around if the temperature is high enough and density low enough not to form liquid or solid iron, so although it occurs in nature it is not exactly a habit. By the way I am planning User:Graeme Bartlett/Chromium hydride to make Chromium hydride but it is in substub status at the moment. This is also CrH in stars. For molecules with Me a metal atom, MeH is likely to be stable as a molecule by itself. However in higher density MeH+MeH may form H₂ and Me. MeH₂ may decompose to Me and H₂ if there is enough energy to move or break the bonds. And MeH_x will have even more ways to break up. For high values of x, eg ReH₉ there needs to be enough space around the central atom to accommodate the H atoms, and then this may be unstable unless there is some extra charge involved, or the temperature is extremely low. Graeme Bartlett (talk) 10:17, 25 July 2012 (UTC)

Creating that article is going to be difficult, considering I can only find its CAS number and a particular spectroscopy study on google.

Maybe, I should rephrase: I'm looking for a pattern, the maximum non-eximer hydride, containing only two centre, two electron bonds, for each elemental group. Plasmic Physics (talk) 11:31, 25 July 2012 (UTC)

Group 3 has a minimum limit of 3 proved by scandium trihydride.

Group 4 has a min. lim. of 4 proved by titanium tetrahydride.

Group 5 has a min. lim. of 2 proved by vanadium dihydride.

Group 6 has a min. lim. of 6 proved by tungsten hexahydride.

Group 7 has a min. lim. of 4 proved by rhenium tetrahydride.

Group 8 has a min. lim. of 3 proved by iron trihydride.

Group 9 has a min. lim. of 2 proved by cobalt dihydride.

Group 10 has a min. lim. of 3 proved by platinum trihydride.

Group 11 has a min. lim. of 2 proved by copper dihydride.

Group 12 has a min. lim. of 2 proved by zinc dihydride.

That's according to WebBook. I proppose a new sequence: 1, 2, 3, 4, 5, 6, 7, 6, 5, 4, 3, 2, 3, 4, 3, 2, 1, 0. Plasmic Physics (talk) 12:05, 25 July 2012 (UTC)

On what basis? Because it matches your sense of aesthetics for the nice pattern? Those numbers don't actually, you know, match the data you just gave, AND there's no evidence that the numbers you just gave are representative. There may not be any pattern at all, it seems quite like you're grasping at straws here: trying to force there to be a pattern where none exists. As a scientist, it is very important that you be wary of the very common error of apophenia: finding patterns where there are none. --Jayron32 22:29, 25 July 2012 (UTC)

If there is a pattern in block A, then there is no reason to assume that there is not a pattern in block B. If that is true then the minimum limit sequence has to be: 1, 2, 3, 4, 3, 6, 5, 4, 3, 4, 3, 2, 3, 4, 3, 2, 1, 0. I just smoothed out the apparent trend, using the fact that main hydrides of block A, don't have odd numbered valence electrons. Plasmic Physics (talk) 01:28, 26 July 2012 (UTC)

I should say that a large part of them are representative, I chose one elemental hydride for each group, but it recurs down the groups for a part of them. Plasmic Physics (talk) 01:46, 26 July 2012 (UTC)

You forgot the 9 for Rhenium - see Potassium nonahydridorhenate. My point above was that if the atom is bigger it can fit more hydrogens. Graeme Bartlett (talk) 11:07, 26 July 2012 (UTC)

Nonahydridorhenate is an anion, I am talking about neutral molecules. Yes, a bigger molecule can fit more hydrogens, I am aware of that. Plasmic Physics (talk) 11:45, 26 July 2012 (UTC)

Iridium(IX) hydride, IrH₉, is theoretically possible. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 17:13, 28 July 2012 (UTC)

Synthesizing HeO using alpha decay

Let's say we have (currently unknown) some ²²⁶RaO or ²²⁶RaO₂(should be easy to prepare).

Now, I wonder if the alpha particles emitted by the process ²²⁶Ra→²²²Rn+⁴He can oxidize the oxygen atoms to form HeO molecules.--Jasper Deng (talk) 05:34, 25 July 2012 (UTC)

Not in any meaningful way, and likely not at all. Alpha particles are very hot, moving at extremely high speeds, much too fast to interact with oxygen or even free oxide. Even if you could slow it dowm, its electron affinity is likely too high to form any meaningful molecules or ionic compounds, even fleetingly, before it simply stripped some electrons off of a nearby atom to make itself neutral helium. There are metastable helium compounds known as excimers, but these aren't formed as you describe, rather they form in conventional helium plasmas. --Jayron32 05:42, 25 July 2012 (UTC)

(edit conflict)Firstly, radium does not exhibit the fourth oxidation state, or are you refering to the peroxide?

Secondly, He²⁺ + O^2- --> He + O^2•.

Plasmic Physics (talk) 05:44, 25 July 2012 (UTC)

I'm referring to the peroxide in the latter; I based this musing off the noble gas compound article where it says there's evidence for an He-O bond.--Jasper Deng (talk) 05:50, 25 July 2012 (UTC)

Yeah, but you simply aren't going to get one off of an alpha particle. The wikipedia article Alpha particle states that recently decayed alpha particles move at 5% of the speed of light; in technical terms this is known as "hauling ass". It isn't going to hang around to pick up any hitchhikers. Even if an He-O bond is feasible, you aren't going to get an He-ANYTHING bond out of alpha decay. They do slow down via collisions with anything, including molecules of air, but those same collisions allow them to easily strip electrons off of what they collide with, giving you again inert neutral helium. --Jayron32 05:54, 25 July 2012 (UTC)

Well if you fire alpha particles into thin gaseous oxygen or solid oxygen or oxygen embedded in solid helium you may get He+ ion which could form a HeO+ molecule. However this is going to be quite unstable as mentioned above, scraping electrons off other things to make He and atomic Oxygen as a more stable alternative. One thing that may work something like this is tritium hydride decaying to Helium hydride ion. In this case most of the energy is put out in the electron and neutrino, with not much imparted to the tralphium. So the molecular bond remains. Graeme Bartlett (talk) 09:24, 25 July 2012 (UTC)

Cryonics and its Viability

Are there any prominent scientific articles discussing the odds of cryonics' success in the future? Futurist110 (talk) 08:08, 25 July 2012 (UTC)

Are you asking about resuscitation of cryonicly preserved humans? As cryonics can be counted as successful now. Graeme Bartlett (talk) 09:26, 25 July 2012 (UTC)

To clarify, single cells (like sperm and embryos) can be frozen, thawed, and reused now. But we can't yet freeze, thaw, and revive a full-sized human. StuRat (talk) 10:33, 25 July 2012 (UTC)

Well, we can achieve two out of three of those goals... that's not bad. Tom Haythornthwaite 07:59, 27 July 2012 (UTC) — Preceding unsigned comment added by Hayttom (talk • contribs)

Our Cryonics article lists 104 references (admittedly not all scientific articles), the second of which has an abstract that includes:

We consider the limits of what medical technology should eventually be able to achieve (based on currently understood chemistry and physics) and whether the repair of frozen tissue is within those limits.

So the answer to the question is probably "yes". Mitch Ames (talk) 10:56, 25 July 2012 (UTC)

Melted cheese

It seems to taste different, and IMHO better, after it's melted, even after it re-solidifies, and hard cheeses are then softer. What changes ? Does anybody sell pre-melted (and re-solidified) cheese ? StuRat (talk) 10:38, 25 July 2012 (UTC)

Denatured proteins? Plasmic Physics (talk) 11:03, 25 July 2012 (UTC)

You wouldn't even need full denaturation, even partial unfolding would be enough to expose buried disulfides, and thus induce cysteine mediated cross-linking between proteins. Would certainly be enough to change the physical properties of the cheese. (+)H₃N-Protein\Chemist-CO₂(-) 13:56, 25 July 2012 (UTC)

Didn't Isaac Asimov write something on why is melted cheese so tasty? --TammyMoet (talk) 18:52, 25 July 2012 (UTC)

Cool, do you have a link ? StuRat (talk) 19:16, 25 July 2012 (UTC)

I've been trying to find it, racking my brains and I'm not even sure it's Asimov and not Feynman or Sagan... pretty sure I'm not hallucinating it though! --TammyMoet (talk) 19:25, 25 July 2012 (UTC)

Thanks for trying. StuRat (talk) 19:32, 29 July 2012 (UTC)

Melting cheese brings the fat (the sixth taste) to the surface making it richer and also potentiating the other fat soluble tastes. μηδείς (talk) 22:06, 25 July 2012 (UTC)

There's some scientific talk here and some vendors here. Zoonoses (talk) 02:55, 27 July 2012 (UTC)

OK, thanks everyone, I will mark this resolved. StuRat (talk) 19:28, 29 July 2012 (UTC)

Resolved

H1 antagonist and sleepiness

Why do H1 antagonist medications provoke sleepiness? OsmanRF34 (talk) 12:55, 25 July 2012 (UTC)

Because they cross the blood/brain barrier and trip the cholinergic receptors of brain cells as well as the H1's of any cell. Wickwack120.145.129.240 (talk) 14:53, 25 July 2012 (UTC)

So, does less histamine get detected? But, why wouldn't our body just release more histamine when it notices that it has less (or it's detecting less). OsmanRF34 (talk) 16:00, 25 July 2012 (UTC)

If I remember my neurobiology and endocrinology correctly, histamine levels are very much a local phenomenon; there isn't much of a globally regulated level like insulin. In fact a global rise in histamine can cause anaphylactic shock.The level of histamine in the nose or under a spot on the skin will rise in proportion to local irritation and its detection by nearby cells will provoke an immune and inflamatory response. Local histamine signalling in the stomach lining does something to regulate mucous levels. And in one tiny part of the brain (some nucleus whatsitsname) responsible for keeping you awake, some cells use histamine as a neurotransmitter to certain specific other neurons that the brain should wake up. The low local histamine detection just makes the downstream cells think that it is time to go to sleep. Staticd (talk) 05:26, 26 July 2012 (UTC)

Generally speaking, increased histamine neurotransmission in the brain will promote EEG arousal via multiple mechanisms (directly depolarising cortical & thalamocortical glutamatergic neurons, depolarising basal forebrain cholinergic neurons, amongst others). Most of this is H1 receptor-dependent, therefore antagonism of H1 receptors will block this activity. See PMID 2565152. Here's a thorough review: PMID 20851648 (open access). --Markr4 (talk) 12:55, 26 July 2012 (UTC)

Hell's Kitchen taste taste

I watch Hell's Kitchen on Hulu so I'm behind a week or so, but in the taste test between Brian and Christina, it seemed unfair that Gordon Ramsey gave them shallots and they both got it wrong for guessing 'onion'. I've never had shallots before but when I see them at ShopRite, they certainly look like small onions and even our shallot article seems to say they're basically a variety of onion. I'm assuming that Ramsey himself would be able to spot the difference -- but how is that is they're basically a variety of onion? DRosenbach ^{(Talk | Contribs)} 15:07, 25 July 2012 (UTC)

There are different kinds of onion. Not quite sure what your question is, but to my mind shallots taste much better than regular onions. Suggest you try some.--Shantavira|^{feed me} 15:28, 25 July 2012 (UTC)

I'm asking: If shallots are just a type of onion, why is it wrong for them to have guessed 'onion'. I understand that something like sweet potato is different than a white potato, but just because shallots have a different name doesn't mean they are different. Whiskey made outside of Kentucky mustn't be called bourbon, but it can taste exactly the same as something made across the state border. DRosenbach ^{(Talk | Contribs)} 16:34, 25 July 2012 (UTC)

Yes, but if he gave them sweet potatoes and they answered "potatoes," they would also have been wrong. A sweet potato may be a type of potato, but a chef ought to know the difference by taste, and most chefs would say "sweet potato" when you asked them what the ingredient was. Likewise, a shallot — which is not even an onion, if you had read the article, it's simply another species in the genus Allium — is different from an onion and a chef ought to be able to taste the difference. — Sam 63.138.152.202 (talk) 18:00, 25 July 2012 (UTC)

Actually our article says it's now classified as the same species, simply a different variety. These sort of taxonomic definitions are somewhat arbitary particularly when it comes to cultiviated species. Nil Einne (talk) 13:35, 27 July 2012 (UTC)

You'd have to ask the show's producers to get a final answer—though their reaction would probably be, "It's a reality TV show; don't sweat it." As 63.138 notes above, it's essentially a functional distinction. If you visit the grocery store or a kitchen, or if you read a menu or a cookbook, the subset of onions identified as shallots will never be described as onions or even small, mild onions. They will be called shallots. In the kitchen, they're recognized as a distinct ingredient, and named accordingly. Regardless of what might be 'correct' for a biologist or taxonomist, calling a shallot an onion is 'wrong' in the domain of the professional chef. TenOfAllTrades(talk) 18:15, 25 July 2012 (UTC)

I don't watch the show, but my understanding is that Ramsay is somewhat of a pedantic jerk, no? Anyway, presumably Ramsay expects wannabe chefs to be able to distinguish between the tastes of major onion and onion-like varieties. Shallots, yellow onions, sweet onions, and red onions all taste quite different and are generally speaking not interchangeable in recipes. Anyway, I would file this under "things not worth spending much time worrying about," personally. Out of all the unfairness in the world, this ranks quite low — it's arguably not unfair at all. --Mr.98 (talk) 18:06, 25 July 2012 (UTC)

And, if they both were judged by the same standard, it doesn't give either an unfair advantage. Heck, he could even have required them to say "it's a shallot harvested on May 23rd, 2012 at 3:28:58 PM, at Tomlington Farms, at the following GPS coords...". StuRat (talk) 19:13, 25 July 2012 (UTC)

First up we have to remember that Mr Ramsay does most of his stuff on TV for dramatic effect. This often involves humiliating people by pointing out their shortcomings in a variety of ways. Considering there are several types of shallots it is asking almost the impossible to expect a regular Joe to be able to tell the difference between them and onions - especially if they are not familiar with them. Most people would be unable to tell the difference in a sudden blind tasting because shallots grown under different conditions and onions grown under different conditions are going to have a lot of flavour overlap. It is not a sin to be unable to tell the difference between shallots and onions in spite of what the odious Gordon might say. When he knows his onions then he's got room to pull up other people - don't hold your breath! Richard Avery (talk) 19:58, 25 July 2012 (UTC)

I distinctly remember a cook on Australia's MasterChef a few years ago got caught out by that too. I agree a chef should be able to tell the difference. I'm not even a chef but I use shallots in Beef bourguignon, If they were diced and cooked in the food i'm not sure I'd be able to tell the difference, but whole or halved they are easy to pick. . Vespine (talk) 22:29, 25 July 2012 (UTC)

I don't know about the MasterChef case but from what I read, the Hell's Kitchen case was a blind test so solely based on taste and perhaps mouth feel (although probably not cooked). However from what I read, at least one person did correctly identify the shallots. It may have just been blind luck, or perhaps it is usually possible to identify shallots in a blind test if you're good enough. (Whether Gordon Ramsay actually could I don't know.) Without commenting on whether it's generally possible to tell the difference between shallots and varities of onions in a blind test or whether someone expecting to be head chef in a top class restaurant should, I'd note that when it comes to cultivated species, going by species is often misleading. I think most of use would agree any chef who can't tell the difference between broccoli and cauliflower or kai lan and cabbage or many other combinations of Brassica oleracea even in a blind test deserves be criticised. (Having said that, I don't think the sweet potatoes example above is a great example. Sweet potatoes are quite distant from potatoes, the fact they're called potatoes is more of an accident of history then anything else, I'm not sure if they're even the most closely related to potatoes of tuberous crops, and potatoes are stem tubers whereas sweet potatoes are root tubers. In other words, calling them a type of potato is IMO a little flawed. Calling a shallot a type of onion less so, in fact it does happen in some languages.) Nil Einne (talk) 08:42, 27 July 2012 (UTC)

I would be quite impressed if somebody could identify a shallot, strictly by taste. StuRat (talk) 19:26, 29 July 2012 (UTC)

hunter education program

according to wikipedia 49 of 50 states have a mandatory hunter education program. what state dosent?--Wrk678 (talk) 17:05, 25 July 2012 (UTC)

I believe that Arizona is the only state that still does not require taking classes to obtain a hunting license.Tombo7791 (talk) 17:55, 25 July 2012 (UTC)

How does curvature correlate to velocity in a random walk (Brownian motion) ?

see duplicate post at math desk
The following discussion has been closed. Please do not modify it.
While investigating fly path curvature in a 2D arena as a statistical parameter, I have found that the curvature-speed relationship follows a power law where curvature in (1/mm) is predicted by the relation C = 10^a * x^b, where a is ~0.8 and b is ~ -1.6, and x is speed in mm/s. Firstly, if behavior is random, doesn't the physical equation for curvature already "totally account" for velocity, i.e. curvature should be statistically independent of velocity in a random walk of stochastic speeds, such as Brownian motion? Curvature is |y"x' - x"y'| / speed^3, but both the numerator and denominator are dependent on velocity and should cancel each other out, right? Thus any correlation between curvature and velocity should be due to non-random behavior-- is this correct? 137.54.30.45 (talk) 17:25, 25 July 2012 (UTC) You have already asked this question on the Math desk. Please don't ask a question in more than one place. Looie496 (talk) 18:12, 25 July 2012 (UTC) I don't recall cross-posting being prohibited-- people suggest that all the time. 137.54.30.45 (talk) 18:37, 25 July 2012 (UTC) People frequently suggest moving a question to a different reference desk, or repeating a question on an article's talk page, but people who contribute here regularly never suggest asking a question on multiple ref desks at the same time. Looie496 (talk) 19:20, 25 July 2012 (UTC)

Converting a density into Daltons/A^2

Hi all, I have a density that's listed as 200 Kg/(mol * Ų). How would I convert this to Daltons/Ų? I'm a little confused, because 1 Kg is 6.02e+26 Daltons, but what's 1 Kg/mol? In Molar mass it says a Dalton is 1 g/mol, so is 1 Kg/mol just 1000 Daltons? So is the above 200,000 Daltons/Ų? Thanks! — Sam 63.138.152.202 (talk) 17:53, 25 July 2012 (UTC)

Yes. A Dalton is just the name given to the otherwise nameless unit that measures the atomic mass. Most basic chemistry books will use g/mol instead of daltons in order to make it easier to convert to grams. Therefore 200 Kg/mol * 1000 grams/1 Kg will give you 200,000 grams/mol or 200,000 daltons. Tombo7791 (talk) 19:14, 25 July 2012 (UTC)

Thank you. I've got it now, working backwards from the mass of a mole of Carbon atoms. — Sam 63.138.152.202 (talk) 19:20, 25 July 2012 (UTC)

On Superman breaking and entering

Let's say Superman pulls on the handle of a locked, standard-commercial-grade steel door. Since we're talking about Superman, he keeps pulling with sufficient force until it breaks open. My question is - which part of the door breaks first? Is it the lock? The hinges? The door frame? The door itself?

For the sake of context, let's say that the door is set in a wall made out of reinforced concrete, at least a foot thick. The frame of the door is probably metal, same as the door itself.

What do you think? Any guesses? --Brasswatchman (talk) 18:03, 25 July 2012 (UTC)

Very likely the handle breaks. There's no need to frame this question in terms of fantasy -- you're really just asking what is the weakest point on a steel door. The answer of course will depend on the specific type of door, but my guess is that for most types the handle will come off before anything else breaks. Looie496 (talk) 18:11, 25 July 2012 (UTC)

I just figured the thought experiment aspect might help the literalists out there. Okay, the handle being weakest makes sense. Switching things around, then - let's say he pushes against the door. What would you guess is the next weakest part? --Brasswatchman (talk) 18:22, 25 July 2012 (UTC)

Mythbusters did a test of trying to bash in a locked door to see what would happen. I don't remember the specifics of how the door was built, by the locks broke before the door or its frame, with the exception of one hotel privacy lock that they installed with stronger-than-standard screws. Someguy1221 (talk) 18:36, 25 July 2012 (UTC)

In crime-prone areas the door may open out, in which case you pry it open rather than kicking it in or pulling on a flimsy handle. In either case, if the latch-plate at the jamb does not fail first, the door itself will fail at the deadbolt, allowing the bolt to swing in or out of the bolt-hole. Picture. μηδείς (talk) 21:54, 25 July 2012 (UTC)

The front doors of homes in crime-prone areas also get knocked down by battering rams more often when the police make a visit. Obviously, they can only bust them inwards. 203.27.72.5 (talk) 01:50, 26 July 2012 (UTC)

Your point--for which you risked carpal-tunnel syndrome, premature keyboard death, and chapped fingertips--is that the police more often use battering rams to knock doors in than to pry them open? Or did I misunderstand you? μηδείς (talk) 02:10, 26 July 2012 (UTC)

My point is that the cops don't take your advice and pry it open even when the door opens outward, they just up the ante a bit. 203.27.72.5 (talk) 04:26, 26 July 2012 (UTC)

Assuming an outward-opening steel door in a steel frame, pushing on the center of the door, the most likely failure mode is tearing failure of the door itself, resulting in Superman pushing his hands through the door (most steel doors are hollow, or are sheet steel wrapped around a wooden core). If he uses some method to distribute the force (say, by pushing against a manhole cover placed against the door), the most likely failure mode will be sheer, compression, and tearing failure of the frame around the latch. He can selectively break around the latch or around the hinges by pushing near one side of the door or the other. If he pulls, the handle's going to break or come off. --Carnildo (talk) 02:48, 26 July 2012 (UTC)

Assuming a uniform door, it will be weakest at the hole cut into it to accommodate the deadbolt. I've seen several such doors fail there. I would love to see a picture of a steel door with a hole punched through the middle by some blunt subsonic object. I have seen wooden doors with central portions kicked in, including my own interior door in a duplex--but that's a different matter, and their locks were metal, not wooden. μηδείς (talk) 03:11, 26 July 2012 (UTC)

When my mother set her house on fire, the fire department attempted breaking in through our steel front door, which was itself in a steel frame. To be fair, they were using axes, but all they succeeded in doing was putting holes through the door and punching one of the locks out. The door stayed right where it was and the door frame was completely undamaged. The door I referenced above was far weaker. Someguy1221 (talk) 03:03, 26 July 2012 (UTC)

Location of Big Bang

If "we" know the trajectories of all the matter then do "we" also know where the center point location of the big bang is today? — Preceding unsigned comment added by 165.212.189.187 (talk) 18:33, 25 July 2012 (UTC)

Although this depends on the shape of the universe, it is entirely consistent with modern cosmology that there wasn't a location of the big bang. Although the big bang is often represented as an explosion into empty space, this is utterly inaccurate. At the moment of the big bang, there was no empty space to explode into. The big bang was everywhere, and things have been getting apart ever since. There is no center of the universe from which we are still hurtling away. Someguy1221 (talk) 18:38, 25 July 2012 (UTC)

In other words, the Big Bang was not the expansion of matter into space, it was the expansion of space itself. Therefore EVERY point in space is the location of the Big Bang. hajatvrc @ 18:44, 25 July 2012 (UTC)

But we are hurtling away from somewhere and to somewhere else, right? we haven't been hurtling away from somewhere forever...165.212.189.187 (talk) 18:47, 25 July 2012 (UTC)

From our vantage point, everything is hurtling away from us. From our vantage point, if you look at the trajectories of every other object in the universe, they're all moving exactly as you would expect if we had been the center of an explosion. Yet it looks that way from every other vantage point as well. — Sam 63.138.152.202 (talk) 18:50, 25 July 2012 (UTC)

The are those trajectories considered an illusion, since we know that can't be?165.212.189.187 (talk) 18:53, 25 July 2012 (UTC)

No if you were on the surface of a balloon, everything would be moving away from you, from every point....the universe is a 3-d version of that.--Gilderien Chat|List of good deeds 18:56, 25 July 2012 (UTC)

Of an expanding balloon, that is. — Sam 63.138.152.202 (talk) 19:19, 25 July 2012 (UTC)

The Big Bang is cannot be looked at as having a location because before the Big Bang there was no such thing as location. Location, or coordinates, is a method of defining something in terms of everything around it. We can describe the location of Earth because we can say Earth is so far away from this point or that point. No method that we have discovered can describe a location for the big bang, and there probably is no method. hajatvrc @ 18:57, 25 July 2012 (UTC)

No, no more than it is an "illusion" that the sun gets farther away from us when we are moving towards the furthest point in our orbit. You can measure the trajectory of the sun with regards to us, and that trajectory is perfectly valid from our frame of reference. When we move towards the apex of our orbit, who is moving, us or the sun? Who is to say? There's no "fixed point" in Space where you can measure everything from. This is a big part of Einstein's Theory of Relativity. — Sam 63.138.152.202 (talk) 19:19, 25 July 2012 (UTC)

Regarding the balloon analogy, however, isn't it more like we are the surface of the balloon? Beings and planets and galaxies surely don't exist outside the fabric of space, and as far as we can tell, (correct me if I'm wrong) space expands at the same rate everywhere. The only reason the relative distance between two given objects (e.g., the sun and the earth) remains constant is that gravity is holding them together against the force of the expansion. This is less relevant on an intergalactic scale, so explains the seemingly ubiquitous red shift we see when looking outside the Milky Way. Evanh2008 ^{(talk|contribs)} 19:22, 25 July 2012 (UTC)

But the balloon was initially not filled with air located at some central location that can be extrapolated to have been "inside" the inflated balloon. How can this phenomenon be related to the big bang?165.212.189.187 (talk) 19:33, 25 July 2012 (UTC)

You're thinking in too many dimensions. Imagine a world in which you can only experience two dimensions, but exists on the surface of a balloon. You don't notice that it's a balloon because every particle is stuck firmly to its surface. Light simply curves around the balloon as it moves, giving the illusion that you are on a flat plane. At the "beginning" of this ballooniverse, the balloon was completely deflated, and the entire surface was crunched into a point of infinite density. Then the balloon began inflating in its own big bang. Every point on the surface is moving away from every other point in its 2-dimensional perspective, the big bang effectively occurred "everywhere". You'll also notice that this universe does not have a center, or at least not one that's reachable by anything it contains. Someguy1221 (talk) 19:43, 25 July 2012 (UTC)

It's an analogy. The universe is not a balloon at all. The way things move apart from each other is like the way that dots on the surface of a balloon would move apart if it were being expanded. — Sam 63.138.152.139 (talk) 20:41, 25 July 2012 (UTC)

Actually I think it's okay to say that the big bang is the center of the balloon. We can trace the motion of present-day matter back to a small area in the past—that's where the idea of the big bang came from in the first place. What you can't do is associate that place in the past with a place in the present. This is because of the relative nature of motion (which is an old idea going back to Galileo in the 1600s). It's well captured by the balloon analogy: the center of the balloon isn't associated with any point on the surface. -- BenRG (talk) 22:13, 25 July 2012 (UTC)

You are entirely wrong, BenRG. The balloon imagery is an analogy, and the big bang happens everywhere on its surface (in higher dimensions) as mentioned above. μηδείς (talk) 22:48, 25 July 2012 (UTC)

He's actually completely correct under the interpretation of spacetime he is using. In our 3D observation, there is a definite point where the big bang happened in the balloon - its center. That point is simply not contained in the 2-surface of the contemporary ballooniverse. The surfaces of concentric spheres around this point can be seen as different snapshots of the ballooniverse's worldvolume, which leads naturally to BenRG's declaration that the center of the universe is in the past. Someguy1221 (talk) 22:54, 25 July 2012 (UTC)

Incorrect. The big bang happened everywhere. There is no center of the universe. μηδείς (talk) 23:04, 25 July 2012 (UTC)

The IP was thinking in too many dimensions, but you are thinking in too few!! Someguy1221 (talk) 23:06, 25 July 2012 (UTC)

No I am not, I am solely criticizing RenRG's bad analogy. Nothing in my statement that the big bang happened everywhere is incorrect. The big bang is not identified with only one point in time and the air inside a ballon bears no analogy with past time, nor is there some fifth space-dimensional "air" inside the hypersurface (assuming it is four dimensional) of our finite self-bounded universe. Hajatvrc and IP 63 above have given correct answers and the OP is not served by BenRG's confusion of the matter. μηδείς (talk) 01:15, 26 July 2012 (UTC)

The crap are you talking about? The air inside the balloon can absolutely be associated with time, even though it is not itself time. You have a two-spatial-dimensional universe (the surface of the balloon), with a third dimension of time. So this universe has 3D spacetime, and 3 dimensions are required to describe the actual shape of this universe. So, let's go back again. You have a 2-dimensional universe, a spherical surface. The universe's world volume is the entire balloon, air inside and all. The surface of the balloon is the present on the world volume, whereas the air inside is the past, and the air outside is the future. The center of the balloon is the big bang, an event. The big bang is the center of the world volume, and could be interpreted as the center of the universe. It's not a center you could reach by traveling through space, however, since it's located in the past. And it does not refute the lack of a center of the visible universe since the big bang is equidistant from all spatial positions in any present time. Applying this to our own universe does not require adding a fifth dimension. Assuming the unproven hypothesis that our universe is the 3D surface of 4-sphere, it's perfectly acceptable to hypothesize the existence of the big bang as a single point on our world hypervolume. As in the balloon example, it is a point that is located in our past and not reachable by traveling through space, and it is equidistant from all spatial positions in the present-day universe. You can hypothesize all of this without ever challenging the centerlessness of the spatial universe. You've shown you are very good at regurgitating the popular talking points, but not at actually thinking about these things, so I'm not going to try to correct you any further. Someguy1221 (talk) 02:19, 26 July 2012 (UTC)

Feel free to curse and repeat my own words at me as much as you like so long as it keeps you out of Batman premieres. μηδείς (talk) 03:31, 26 July 2012 (UTC)

Your disagreement with Someguy1221 is due to the lack of information regarding whether space is closed. A closed space spacetime expands from everywhere, but an open space spacetime expands from a particular point in that space. A balloon is a closed two dimensional surface. Alternatively, a rubber disk expanding into a plane represents an open space with a central point. See also great attractor. 207.224.43.139 (talk) 21:03, 28 July 2012 (UTC)

From our own perspective, there is not a place that is central but there is an inertial frame that is closest to being at rest, in a sense. I don't know if it has been determined with any kind of accuracy, but it would be that for which the temperature from the Big Bang (microwave background radiation) is as close as possible to being isotropic (the same in all directions). The answer to the OP's question is definitely that there is no center, and simply understanding the balloon analogy extended to 3 dimensions--as opposed to the 2 on the ordinary balloon's surface--gives an adequate picture of how space and matter over time are to be considered. Everything is moving away from everything else, aside from smaller local questions (the Solar System, Andromeda and the Milky Way colliding, etc.), and at the same rate per distance of separation. Simply backing up the picture to a single point is to take EVERYTHING to that point (where no particular current place has any more or less right to be considered the center than another).173.15.152.77 (talk) 00:01, 26 July 2012 (UTC)

Thanks all. I guess the balloon analogy is more accurate than most thought, afterall Ben .68.83.98.40 (talk) 03:03, 26 July 2012 (UTC)

The only way this makes sense to me is if the space between all particles was increasing at the same rate. The distance between galaxies is always proportional to time....going back in time they must be "closer" than present yet would never actually reach the same point if taken back to T=0.GeeBIGS (talk) 04:12, 26 July 2012 (UTC)

It's not the case for all particles. Electrostatically and gravitationally bound particles are not moving apart with the expansion of the universe.μηδείς (talk) 04:28, 26 July 2012 (UTC)

My understanding of the big rip scenario is that they are moving apart ever so slowly. I'm probably not understanding it correctly though. 203.27.72.5 (talk) 05:08, 26 July 2012 (UTC)

Only partially. Expansion of the universe affects all things equally in proportion to the distance between them. But it doesn't change the laws of physics. Two hydrogen atoms in a molecule of hydrogen gas do experience a dark pseudoforce pulling them apart, ever so slightly, but they remain bound at a statistically constant distance due to the attraction between them, which strengthens when you attempt to separate them. They may be imperceptibly further apart than they should be, but they aren't moving ever so slightly. Imagine yourself pushing on a brick wall. The force you are applying is real, but the wall doesn't go anywhere. You might have caused it to flex a few nanometers, but it doesn't keep moving since the foundation of the wall pushes back with an equal force eventually. But with enough effort, you (or more likely a bulldozer) can overcome what force the foundation is capable of reacting with without breaking, and push that sucker over. That's your big rip. Someguy1221 (talk) 05:18, 26 July 2012 (UTC)

So all of a sudden a bulldozer comes along and tears apart the universe? Where does this future "explosion" come from?GeeBIGS (talk) 05:39, 26 July 2012 (UTC) Wouldn't the big rip also mean that space is incompressible?GeeBIGS (talk) 05:51, 26 July 2012 (UTC)

It's not all of a sudden. It's a gradual increase in the rate of expansion. When you are pulling apart a sheet of paper, the sheet seems normal at first if a little stress, until you pass a critical level of force, and the whole thing rips apart. It's like that with matter and the big rip. The force is gradually increasing, rather than suddenly. At some point, suddenly, the force of expansion crosses a threshold at which it can tear particular atoms from one another. And I wouldn't really call space "incompressible". It's not clear what, exactly, expansion is caused by. We just know that things are getting further apart. It's possible expansion will reverse and contraction will begin - big crunch. Without understanding the nature of dark energy, the force hypothesized to drive expansion, we can only speculate on what will actually happen. Someguy1221 (talk) 05:57, 26 July 2012 (UTC)

Each atom is getting further apart, but much slower than each galaxy is?GeeBIGS (talk) 06:05, 26 July 2012 (UTC)

Two atoms in a molecule are not getting further apart. They are stuck to each other, just like two halves of a sheet of paper. Unless you supply the necessary force, they are staying stuck to each other. In the case of things that aren't stuck to one another, such as distant galaxies, the rate of expansion is proportional to the distance between them. Someguy1221 (talk) 06:20, 26 July 2012 (UTC)

Yes but I read here before that the distance between electrons and their corresponding nuclei can be infinitely far apart and still be bound.165.212.189.187 (talk) 13:10, 26 July 2012 (UTC)

The distance of a bound electron to its associated nucleus is not a well defined concept. Someguy1221 (talk) 17:19, 26 July 2012 (UTC)

So then it fits into the realm of possibility?165.212.189.187 (talk) 18:20, 26 July 2012 (UTC)

Can "we" detect the "force gradually increasing"?165.212.189.187 (talk) 13:08, 26 July 2012 (UTC)

No. The force is too small to detect on small scales. All "we" can do is look to cosmology and see that it was weaker in the distant past. Someguy1221 (talk) 17:19, 26 July 2012 (UTC)

So you use the "weaker in the past" for the big rip but when it comes to "closer in the past" to say all the galaxies were once in the same spot - that doesn't work? Sounds like the same logic.165.212.189.187 (talk) 18:20, 26 July 2012 (UTC)

I'm not just saying they were closer in the past. Not only were the galaxies closer in the past, they weren't moving as quickly either, per unit of distance from one another. Someguy1221 (talk) 06:12, 27 July 2012 (UTC)

There are two different possibilities. Dark Energy may work like the cosmological constant, i.e. for every volume of space there is a constant amount of energy pushing the universe apart. Since the universe grows, so does the Dark Energy, and things fly apart faster and faster, but only because they already are apart farther and farther. I'm ignoring gravity, which is important, but complicates things. In particular, bound objects of a given size will stay bound "forever". In the Big rip scenario, Dark Energy is not equivalent to the cosmological constant, but its density is increasing over time, effectively increasing the expansion of space even at constant distances. So the size at which objects can stay bound decreases more and more (because the universe is tucking on them harder and harder). Eventually, galaxies, solar systems, planets, people, and even elementary particles will be ripped apart. --Stephan Schulz (talk) 18:56, 27 July 2012 (UTC)

Camel humps and dehydration

I understand that fat in camel humps is metabolized to produce water, saving them from dehydration during dry periods.

1) Do humans produce water from their own fat, too ?

2) If so, why do people who still have fat on them die of dehydration ?

3) Do we metabolize it too slowly and/or need water faster than this mechanism can provide ?

4) Would an obese person be able to avoid dehydration longer than a skinny person (neglecting the tendency of the extra fat to overheat them and make them sweat more) ?

StuRat (talk) 19:44, 25 July 2012 (UTC)

Metabolizing fat uses water, it doesn't produce net water. " This process of fat metabolization generates a net loss of water through respiration for the oxygen required to convert the fat." The fat in the camel humps is used for caloric shortages. μηδείς (talk) 22:43, 25 July 2012 (UTC)

That's my understanding of it too. When you're working out to lose weight, you have to keep up your body well hydrated since otherwise you won't have the water needed metabolise the fat, and your body will just keep consuming carbohydrates and eventually protein (not to mention become severely dehydrated). 203.27.72.5 (talk) 23:01, 25 July 2012 (UTC)

That's sort of an iffy statement. But even on the most liberal interpretation, total metabolism of a pound of fat produces around 4000 Calories -- about two days worth -- and a bit more than a pint of water, the exact value depending on the exact composition of the fat. In other words, not really enough to keep you going. Looie496 (talk) 23:00, 25 July 2012 (UTC)

Medis is right. See Camel#Eco-behavioural_adaptations and Lipolysis. 203.27.72.5 (talk) 23:07, 25 July 2012 (UTC)

Thanks, I had intended to add just that link to the sentence I quoted from it above. μηδείς (talk) 01:04, 26 July 2012 (UTC)

OK, thanks all. Apparently camels store water in their blood streams, not humps. Reading up on it, it seems that while the actual metabolism of fat produces water, the amount of respiration required over that time period allows more water vapor to escape than is produced. However, I'm not clear on whether this is more or less loss of water than would occur over the same time period, without metabolizing fat. Does anyone know the answer for this, for camels and humans ? StuRat (talk) 17:52, 27 July 2012 (UTC)

Sexual peak

http://madamenoire.com/181970/turns-out-women-hit-their-sexual-peaks-sooner-than-we-thought/

I'm sure many people would presume that 18-25s are the most sexually active but this recent survey seems to show this to not be true and that both males & females peak much later on in life in terms of sexual activity. Could this be true based on any biological evidence or is it more to do with social and cultural implications? 176.250.228.140 (talk) 22:24, 25 July 2012 (UTC)

OKtrends published an informal study (albeit one with shit-tons of data) on this very topic, and also agreed that at least the female sexual peak comes much later than expected. I suspect this is sort of biological, but influenced by societal factors. Firstly, your biology doesn't "want" you to start cranking out babies the moment you can. Very young mothers have a higher rate of complications, so it makes sense from a biological perspective that sexual peak would occur some time after sexual maturity. As to why it is so long after, I suspect it is caused by stress. In a study I read about in the New York Times, although I can't remember where it was actually done or published, researchers used fMRI to show that the sexual centers of the brain are less activatable when a female subject is under stress. So I would hypothesize that during a person's formative years, when they are dealing with college, finding a career, figuring out who they are, they may be statistically under more stress then they will be in their 30s. And so by the findings, they may also be significantly more interested in sex in their 30s. Now of course your body, your biology, doesn't "know" why you're stressed out. But if you think about the much more extreme types of stress that would have predominated tens of thousands of years ago (starvation and predation), it would make sense your body would "want" you to not be making new people under such conditions. Someguy1221 (talk) 22:37, 25 July 2012 (UTC)

For females, I believe it has long been understood that, their sexual peaks were much later but it is surprising that this is also true of males. I would have thought younger males in college are more open to multiple partners and casual sex but apparently not according to the survey. So how can this be explained for males? — Preceding unsigned comment added by 176.250.228.140 (talk) 22:47, 25 July 2012 (UTC)

I had often assumed that males would be under the opposite pressure from females. A female wants to make it through stressful periods, and doesn't want to be saddled with a pregnancy while doing so. A male, on the other hand, might want to mate just in case he doesn't survive the same periods. However, there is a flaw here in how "sexual peak" is defined. In the article you linked, it was based on when a person had the most sex, rather then on when they wanted the most sex, which is the measure used by OKtrends. I am completely unsurprised that the average 29-yr-old statistically has more sex than younger men, but that says nothing about when their sexual urges peak. Someguy1221 (talk) 22:51, 25 July 2012 (UTC)

Yes. The OP link just goes to show that women decide when men will have their "sexual peak" and they prefer men about 5 years older than themselves. --81.175.236.109 (talk) 12:20, 27 July 2012 (UTC)

I believe last time something similar came up, someone pointed out with IIRC links that despite common myths, married people or those in a commited relationship actually tend to have sex a lot more then those nominally single having casual sex. IMO this isn't really that surprising when you think about it. Sure there are some people like those potrayed in TV etc who have a different partner each night but the majority of people aren't like that. In worldwide terms, I would say it's even less surprising. A number of areas are still fairly conservative, with sex before marriage strongly frowned upon (often particularly for females) and while it happens a lot more then those in power and parents like to believe, opportunity may be limited for access reasons (people living at home or in university dormitorities). And in some cases legal reasons provide something of a disincentive. Of course in such areas marrying before 25 isn't that uncommon although baring a high divorce or death rate, it's not surprising someone past 25 is more likely to be married, let alone in an area with a high age at first marriage. (Note that initially at least, the OP appeared to be referring to a peak in sexual activity rather then urges, as Someguy1221 said, it's not exactly surprising if the peak in sexual activity differs from urges.) Nil Einne (talk) 05:04, 26 July 2012 (UTC)

My own experience has been that people in their mid 30's typically have the greatest sex interest. I can't be the only one to make the observation since that part of life is colloquially known as one's "dirty thirties". This can be confirmed by looking at the accounts on any swinger's/adult dating website. 203.27.72.5 (talk) 22:56, 25 July 2012 (UTC)

This is probably one area where A) Research results are very unreleliable and unstable across societies (and times), and B) A mean value statistic has very limited value anyway. It has a kind of curiosity value, and more complicated questions that would include determination of averages could certainly have applicable value in some sense; but I doubt that at present social scientists or sexologists are going to have very much of value to offer the layperson (no pun intended) on this question in the form asked (for mean values).173.15.152.77 (talk) 12:08, 28 July 2012 (UTC)

Efficiency of Solar Water Heaters

The wikipedia article on Solar water heaters gives information on their efficiency that I can't make any sense of, and the sources cited sound questionable anyway (Petrotyranny, etc.). For example; the flat plate thermosiphon configuation with a 1.98m² absorber surface area generates 3.9kW.h/day of heat if it gets an insolation of 3.2kW.h/m²/day.
$3.2kWh/m^{2}/day\times 1.98m^{2}=6.336kWh/day{\text{ of light energy}}$
${\frac {3.9kWh/day}{6.336kWh/day}}=62\%$
Likewise, it gets 68% efficiency at 6.5kW.h/day insolation. But the article says it has a Maximum efficiency of 74%. It doesn't define that term, so I have no idea what to make of it. Is that the peak efficiency at midday, or the maximum efficiency for a whole day at optimum insolation? So can anyone either clarify the above or point me to a better resource for data on the efficiency of solar water heaters? 203.27.72.5 (talk) 22:43, 25 July 2012 (UTC)

The maximum efficiency is attained only if the solar incidence angle remains direct through the day, i.e., if the collector were on a sun-tracking mount. 207.224.43.139 (talk) 21:15, 28 July 2012 (UTC)

So that implies it's an instantaneous value. Do you have a reference or any other reason to think that? 203.27.72.5 (talk) 01:05, 29 July 2012 (UTC)

Sorry, just reading on solar over the decades, but I'm sure it's instantaneous for water heaters. Ask the manufacturer? 207.224.43.139 (talk) 05:45, 29 July 2012 (UTC)