Wikipedia:Reference desk/Archives/Science/2007 January 24

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[edit] January 24

[edit] non-venomous snakes

Which snakes are non-venomous, like Garter Snake for example? I doing a video about girls dancing in naked with non-venomous snakes. I did read the article about the non-venomous snakes but, it said some snakes like Boomslang are venomous. Can someone tell me which snakes are non-venomous?

See Snake and Venomous snakes, and check library books to be sure. Some can be easily confused with others; the first Ball python I saw looked like this one [1] and reminded me of an American copperhead. Any snake can deliver a painful bite. Edison 00:14, 24 January 2007 (UTC)

Thank you for your help.

The easiest way to do it is usually to locate which snakes are venomous and work backwards from there. Even easier if you are talking about a specific region — it is pretty easy to tell which snakes in North America are poisonous, for example (vipers and the coral snake, and that's about it). --24.147.86.187 02:14, 24 January 2007 (UTC)

Videos of girls dancing naked with snakes? Tell me when you're done taping, I want to buy one! None of my snakes could dance. X [Mac Davis] (How's my driving?) 03:54, 24 January 2007 (UTC)

Buy a video, a girl, or a snake?Edison 05:03, 24 January 2007 (UTC)

Snakes on a dame! --Zeizmic 12:58, 24 January 2007 (UTC)

[edit] Zinc and HCl reaction with copper catalyst

Can anyone tell me what the effect of a catalyst, preferably copper, would have on the reaction of HCl and Zn? Further I would like to know how I could prove this in an experiment?

Thank you so much —The preceding unsigned comment was added by 198.54.202.250 (talk)

By definition, adding a catalyst to a reaction will accelerate it. What effect some specific material would have (does it catalyze a certain reaction, and by how much) is the question. To "prove this in an experiment", well that just mean you try it and see what happens (Zn+HCl, with and without a certain catalyst added). I have no idea how copper would affect this particular reaction. DMacks 01:45, 24 January 2007 (UTC)

Catalysts lower the activation energy of a reaction, making this barrier easier to overcome. Notice that copper (Cu) is not in the equation. That is because it is not consumed by the reaction. Basically, it goes in one end as copper, and comes out the other as copper! The chemical equation to this reaction is as follows:

Zn _(s) + 2HCl _(aq) → ZnCl₂ _(aq) + H₂ _(gas)

− Twas Now ( talk • contribs • e-mail ) 04:23, 24 January 2007 (UTC)

[edit] Electricution by speakers

My amp outputs 100W for each speaker. from reading the article on speakers, i understand that its simply an electrical signal. why is it if i grab the 2 wires to each speaker with my fingers i dont get electricuted? 100w should be more than enough to give me a jolt, no?

The voltage is probably less then 50 v pk. not enough to cause any appreciable current unless you stuck the wires thro your skin and into the blood stream (dont!)--Light current 03:22, 24 January 2007 (UTC)

Most speakers are 8 ohms. Simply speaking, 100 watts into 8 ohms gives 28 volts. Although if it's a stereo amp, that's probably 50 watts/channel, for only 14 volts. Definitely not enough to shock you, although if you got your fingers wet and cranked some punchy music up real loud, you might be able to feel a little tingle.

If it were possible to shock yourself with ordinary audio amplifiers and speakers, they would require much more substantial wiring, with protective insulation at the connections. The fact that no such special wiring is required is one clue that the voltages involved are generally regarded as safe.

—Steve Summit (talk) 03:36, 24 January 2007 (UTC)

You would be much more likely to burn yourself, like me. X [Mac Davis] (How's my driving?) 03:50, 24 January 2007 (UTC)

This is not a subject I am highly knowledgeable about, but I think it is the voltage which determines whether or not you get shocked, not wattage. − Twas Now ( talk • contribs • e-mail ) 04:27, 24 January 2007 (UTC)

Of course with a ~~tstepup~~ stepup transformer it would be quite possible to electrocute someone with the output of a stereo amplifier. There was a case where someone did just that. (And we all know AC is more deadly than DC.) Edison 05:05, 24 January 2007 (UTC)

It's a combination or amps and volts that's dangerous. The electric shock article has descriptions of the dangers. 05:15, 24 January 2007 (UTC)

True, although it's really milliamps and volts. (In particular, a 15 amp, 120 volt circuit is no more or less dangerous in terms of electrocution hazard than 20 amps, or 1 amp, or 100 amps.) —Steve Summit (talk) 13:49, 24 January 2007 (UTC)

Though it may be pedantic to say so, it's really the current that can kill you, not the voltage. A few milliamperes through your heart is often sufficient to stop it, but you can withstand a low-current electrical discharge of several thousand volts with just some discomfort. Remember when you shuffled around on the carpet and shocked someone? The electrical potential required to do that can easily be in the range of 10 kV (don't be misled, though, breakdown happens at a critical electric field, not a voltage), but the amount of excess charge you have built up in your body isn't sufficient to sustain a large current. The result is that you feel an uncomfortable shock, but nothing nearly life-threatening. This is different from, say, a 5 kV three-phase residential mains, which are connected to a power grid designed to deliver a lot of current if need be.

As regards audio amplifier power ratings, that is just the maximum rated power output for the speaker drive. Nothing requires that a speaker be dissipating that much power at all times (in fact, it usually is not). Also, if you're wondering about the seeming discrepancy in Light current's voltage estimation and Steve Summit's, realize that power rating is calculated using RMS values, so both estimations are about right (read AC power). Incidentally, if you turn up the volume on your amplifier while holding the speaker leads you probably will feel a jolt. 50 V p-p should be able to induce enough current for you to feel. Even at lower voltages you ARE actually being "shocked", but the electrical current is too small for your nervous system to detect. -- mattb @ 2007-01-24T15:47Z

While it's strictly correct to say that "it's not the voltage that kills you, it's the current", this ends up not being a terribly useful statement in practical terms. The current it takes to kill you, at the heart muscle itself, is on the order of milliamps, but except during open-heart surgery, there's no way to apply current (or voltage) directly to the heart muscle. The interesting question, then, is what kind of electricity does it take applied to your skin to induce a fatal current density deep within your chest cavity. For that question, under everyday circumstances, the more interesting variable really is voltage, not current.

For example, although a car battery is capable of supplying many hundreds of amps, if I put my left hand on the negative terminal and my right hand on the positive, I will not even feel anything, let alone be fatally electrocuted, because the 12 volt potential of that battery is not sufficient to induce any significant current across the many kilohms of resistance of my body (much of which, it must be said, is the resistance of my relative dry skin). If, on the other hand, I hold a piece of metal in my left hand and stick it in the hot side of an electric outlet, and put my right hand in a bathtub full of water, the situation (and the possible outcomes as regards my health and longevity) are very, very different. The difference is the voltage: the 120 volts (in the U.S) or 240 volts (many other places) of potential behind that electric outlet are enough to overcome my skin resistance and induce significant currents across and within my chest cavity, with potentially heartstopping effects. It makes no difference whether the current supplied by the outlet is (capable of being) 10 amps or 20 amps or 100 amps or even just 1 amp, it will shock and potentially electrocute me all the same. The only situation in which the current matters for a high-voltage shock is if the current is somehow limited to less than the few milliamps it might take to kill me. But electrical sources which can deliver high voltages but with currents limited to a few milliamps are comparatively rare. (But not unheard of. One example, as already mentioned, is everyday household static electricity such as you might get by shuffling your shoes on carpet, or combing your hair, or petting your cat, or rubbing a balloon on your coat. Another example is a neon sign transformer, which develops 12 to 15 thousand volts, but with current limited to I think 12 milliamps.) —Steve Summit (talk) 05:39, 25 January 2007 (UTC)

Of course, I never intended to imply otherwise, only to point out that it really is the current induced by a high voltage that can be fatal, not the mere existance of a potential difference. -- mattb @ 2007-01-25T14:38Z

[edit] Sound energy

is the total sound energy calculated as Amplitude X Frequency? is sound energy the same as "volume"? is there a relationship (equation) between amplitude, frequency, and volume.. kind of like the way voltage, current, and power are related? —Preceding unsigned comment added by 209.53.181.151 (talk • contribs)

From sound energy density:

$E = \xi^2 \cdot \omega^2 \cdot \rho = v^2 \cdot \rho = \frac{a^2 \cdot \rho}{\omega^2} = \frac{p^2}{Z \cdot c} = \frac{I}{c} = \frac{P_{ac}}{c \cdot A}$

You might also be looking for sound intensity. X [Mac Davis] (How's my driving?) 03:57, 24 January 2007 (UTC)

[edit] Buying Copper?

Where can I purchase blocks of high purity metals, such as copper?

Ebay is the best place to look first! :) X [Mac Davis] (How's my driving?) 04:22, 24 January 2007 (UTC)

There are companies such as Alfa Aesar that sell very pure chemicals for scientific use. Alfa Aesar will sell you pure copper in many different forms. —Bkell (talk) 06:17, 24 January 2007 (UTC)

[edit] Homosexual transexual

There are humans who are transexual. There are humans who are homosexual. But are there any homosexual transexuals? - posted unsigned.

Yes - I can remember a lesbian transexual interviewed on talk radio a number of years ago, and happen to know another myself. --Neo 09:38, 24 January 2007 (UTC)

Of course. Between FTMs and MTFs you can find all sorts of attractions. I haven't seen any FTMs interested in men though. Night Gyr (talk/Oy) 11:14, 24 January 2007 (UTC)

Trannie bisexuals probably. But why would someone get a sexchange if they like the opposite sex? -- 我♥中國 17:40, 24 January 2007 (UTC)

Sex reassignment surgery is all about making one look like what they feel, regardless of their sexual orientation in the first place. So a hetero male who feels like he is a woman trapped in a man's body could get SRS and then still have a relationship with a woman afterwards. howcheng {chat} 18:46, 24 January 2007 (UTC)

I have also (anecdotally) heard of MTF transsexuals whose "object of desire" switches as they get hormone therapy, so that they change from a straight man to a straight woman, or from a gay man to a lesbian. —An gr 09:49, 25 January 2007 (UTC)

[edit] rf load

moving under RF LOAD. PLease do not post Qs more than once!--Light current 17:13, 24 January 2007 (UTC)

[edit] How to find technical bibliography of biology professor

I have searched the internet for the technical bibliography of Professor Steven Rose a neurobiologist. I found a page that included a listing of his papers from 2000-2006 but I need his earlier papers. Any suggestions of how I could find this. I thought of posting on the talk page of the Steven Rose article but its empty so I doubt anyone is watching it. -- GrahameKing 08:13, 24 January 2007 (UTC)

Go into a public research library (such as the ones at a good university) and ask at their reference desk. They will have access to databases like Web of Science. That may not get you everything, but it should get you most of the publications in major journals.

I don't suppose you've considered just emailing Professor Rose and asking him?--Robert Merkel 11:23, 24 January 2007 (UTC)

Send me your e-mail address (go to my user page; then e-mail this user); I'll send you back a ref list for S. Rose. ike9898 14:04, 24 January 2007 (UTC)

I have posted a lengthy list of Steven P.R. Rose publications on User:GrahameKing's talk page. − Twas Now ( talk • contribs • e-mail ) 08:49, 25 January 2007 (UTC)

Note that Pubmed is a free to all, web accessable version of Medline which searches for journal publications in the medical/biological/biochemical fields. -- 17:52, 25 January 2007 (UTC)

[edit] Cooking with gas.

Is there any difference from the cook's point of view when you cook with town gas, natural gas or LPG? thanks 203.109.174.164 10:57, 24 January 2007 (UTC)

Essentially no. Town gas is usually natural gas, though is sometimes doped with LP if the natural gas feed is temporarily inadequate to satisfy the demand (on a minute-by-minute basis). Thus a substitution often happens without the notice of cooks or other gas users. However, when LP gas is used, it must be mixed with air to have the same heating properties as natural gas. LPG alone has more energy per unit volume than natural gas. ^tucker/_rekcut 11:54, 24 January 2007 (UTC)

I'm sure what tuckerekcut meant to say is that "In order to burn correctly, LP gas must be mixed with a different amount of air than natural gas". Obviously, both fuel gases must be mixed with air to burn. Some stoves/cookers can accomodate this by changing the "air shutters", others are pretty-permanently adjusted to one type of fuel or the other and won't tolerate a fuel that deviates too far from their intended fuel.

Atlant 17:04, 24 January 2007 (UTC)

I'm confused; unlike internal combustion engines which supply a specific quantity of air to the combustion chamber, I thought open flame stoves just reacted with the ambient air. Are you saying they mix air with the gas supplied, prior to combustion ? StuRat 19:26, 24 January 2007 (UTC)

Yes, definitely. The fuel gas is fed out of a calibrated orifice which meters out a maximum amount of gas and also creates a jet through a venturi. The back of the venturi is open to the ambient air and an appropriate, proportional amount of ambient air is dragged in by the flowing fuel gas. The fuel gas/air mixture is then routed to the burners. Because it's a proper stochiometric mix, it burns with a nice blue flame from bottom to top of the flame, without soot being deposited on your pots and pans. When you change fuel gases, you often have to change orifices and adjust the "air shutters" that admit air into the venturis. Here's a picture.

Atlant 02:27, 25 January 2007 (UTC)

I notice I only get the nice blue flame on low settings. On higher settings I get flecks of yellow. StuRat 10:31, 25 January 2007 (UTC)

Time to adjust your air shutters? But mark the initial positions in case things go from slightly bad to worse.

Atlant 12:41, 25 January 2007 (UTC)

Above, Tucker said "Town gas is usually natural gas", but the town gas article disagrees, and also says it doesn't have a specific composition. I remember hearing a relative say "When they converted to natural gas in our area, we had to adjust our cooking because the flame was hotter." Maybe the answer to the original poster's question depends on what sort of town gas is meant. --Anonymous, January 25, 17:49 (UTC).

Well, any cookware worth its salt distributes the heat from the flame pretty evenly, so the peak temperature of the flame probably isn't the issue. But what you have correctly identified as an issue is the maximum amount of heat that a given fuel gas will produce given a certain orifice in the burner arrangement. Generally, if you change fuel gases, the orifice is changed to provide roughly the same heating value with the new gas as you had with the old gas. If you just adjust the air shutters, you're almost certainly changing the total amount of heat that the burner can produce as the heat value of the various fuel gases varies quite a bit.

BTW, my parents went through the same experience as your relatives when the gas company switched from manufactured gas to natural gas.

Atlant 18:25, 26 January 2007 (UTC)

[edit] national geographic

in the 1999 issue of nation geographic on biodiversity there is a diagram representing the species of organisms and their numbers and proportions , the problem is that i no longer have that issue with , i was wondering if any one could suggest any way to get this diagram or would anyone be kind enough to scan that image for me .

regardsMi2n15 12:02, 24 January 2007 (UTC)

Have you tried your local library? Or, try a friend. There's always someone who saves all their national geographics. I don't think scanning a diagram would fly with wikipedia's copyright policy. Night Gyr (talk/Oy) 12:05, 24 January 2007 (UTC)

My mom threw all mine away :( X [Mac Davis] (How's my driving?) 20:08, 24 January 2007 (UTC)

From The National Geographic Society Website [[2]]:

How can I order back issues?
You may order back issues from the National Geographic Society by contacting us:

National Geographic Society
Single Copy Department
Telephone: 800 777 2800 (U.S. and Canada only)
or +1 813 979 6845
E-mail: ngs.single@customersvc.com

NATIONAL GEOGRAPHIC Back Issue Rates, in U.S. Dollars
Cover date : Price per issue
...
1986-present : $6

NOTE: Outside the U.S., please add U.S. $1.50 per copy.

NOTE: Payment is required before a back issue can be mailed. Discounts are offered for educational institutions and on bulk orders of 100 copies or more. Please contact our Single Issue Department (see above) for these special prices.

-- 17:49, 25 January 2007 (UTC)

[edit] Dead body reflexes

I'm looking for the word that refers to a reflex action that comes from a dead body. Hope someone has the answer. thanks for your help. marie Martin

cadaveric spasm - Johntex\^talk 16:32, 24 January 2007 (UTC)
- In the tears after Galvani and Volta's discoveries, doctors did gruesome experiments with recently dead animals, including humans, and found that the corpse would change its facial expression, including moving the eyes and mouth or sticking out the tongue, when stimulated with electricity. This may have inspired Mary Shelly in some of the details of her novel about Frankenstein. This may also be a factor in observers thinking a person executed in an Electric chair is still alive and struggling against the restraints, each time the current is reapplied, when it it is really electricity stimulating muscle contractions. Edison 18:44, 25 January 2007 (UTC)

[edit] Liquids that are safe to drink?

The article on water intoxication says that even plain old water is toxic if ingested in large enough amounts. Are there any liquids that are safe to drink, meaning that they don't induce chemical intoxication regardless of the amount ingested? JIP | Talk 14:44, 24 January 2007 (UTC)

Aside from chemical toxicity, a major concern is the osmolality of the solution. For that reason, a 0.9% NaCl solution would be just fine. Can't think of any other examples offhand. --David Iberri (talk) 14:54, 24 January 2007 (UTC)

Although even that is going to cause you trouble eventually. Even though the osmolality of normal saline is good, you'll lose other ions in your urine, and build up sodium in your body. TenOfAllTrades(talk) 16:08, 24 January 2007 (UTC)

A liquid would likely be safe to drink in copious amounts if it satisfies three requirements: one is osmolarity, the solution should have an osmolarity of approximately 300mOsM, the same as the intracellular compartment. Two is diffusibility, the dissolved solids must not be able to diffuse directly through the plasma membrane (unless the same chemical has an osmolarity of 300mOsM inside the cell too). Three is nontoxicity, the solute must not interfere with biological processes. Normal saline and ringer's acetate fit this description, and ringer's lactate comes relatively close. ^tucker/_rekcut 17:03, 24 January 2007 (UTC)

Does blood fit all these requirements:]Hidden secret 7 18:31, 24 January 2007 (UTC)

Its okay, provided you have the enemy's skull to pour it in first. -- DLL ^{.. T} 20:01, 24 January 2007 (UTC)

Blood would cause iron toxicity if consumed to excess. TenOfAllTrades(talk) 20:13, 24 January 2007 (UTC)

Although not a liquid, vitamin C is basically impossible to overdose on. X [Mac Davis] (How's my driving?) 20:19, 24 January 2007 (UTC)

What if they had anaemia:@Hidden secret 7 20:31, 24 January 2007 (UTC)

It doesn't take a lot of blood to make you sick actually. Vespine 22:05, 24 January 2007 (UTC)

Really? I have a lot of blood... | AndonicO ^{Talk · Sign Here} 13:41, 25 January 2007 (UTC)

I don't think the original poster needs to be concerned with the possibility of water intoxication (assuming that's even why they posted the original post). I believe they'd feel too full to want to continue drinking water and the frequent trips to the toilet would be become sufficiently annoying to deter any would-be accidental water overdoser. In summary: water is safe to drink! More than safe, even - healthy! --Seans Potato Business 18:29, 25 January 2007 (UTC)

The post was probably in response to this [3]. Chickenflicker---♣ 03:09, 26 January 2007 (UTC)

[edit] choir boys

Do choir boys' voices break later than normal boys'?

The articles Puberty#Voice_change and Human_voice are relevant, but I can't find much on this issue in either one. I've not heard that regular singing changes when a boy's voice would change, but I really don't know. One factor that might make it seem like they change later- boys whose voices have not yet changed may be selected for singing because of this. In other words, if the boy's choir seems high-voiced, maybe it's because the boys whose voices have already changed aren't in the boy's choir anymore. Friday (talk) 15:24, 24 January 2007 (UTC)

And, of course, see castrato for a method once used by the church to enhance their choirs at some minor expense to the singers.

Atlant 17:07, 24 January 2007 (UTC)

[edit] Safety Critical Decision Making

Wiks have the potential to provide a "big brain" perspective on any topic.

How does one use a Wiki to enhance safety critical decision making when numerous single accountable individuals make up the formal decision hierarchy?

The dilema is how does one maintain accountability while leveraging the big brain?

SpaceSafetyGuy 15:29, 24 January 2007 (UTC)

Wow. Was that english? You can create your wiki, semi-protect it, and disable account creation, so that only people whose accounts you have created for them can edit. In this way, you'll know who said what (history). yandman 15:41, 24 January 2007 (UTC)

You could also enforce signatures, so that users do not have the option to leave their post unsigned. Page protection is another way. You could set it up so that there are some pages anyone can edit, other pages that can only be editted by "team leaders", other pages that can only be editted by a designated "safety summarizer", other pages (containing goals and the like) that can only be editted by top managemement, etc. Johntex\^talk 16:25, 24 January 2007 (UTC)

Michael Griffin - is that you? bmk

A launch decision requires the assessment and resolution of numerous "niche science issues" (e.g., Space Shuttle example / foam loss, foam transport, impact and damage assessment or in the case of Challenger - the phenomena of soot on secondary O-rings (blow-by). As yandman notes a wiki could be bounded if the desired decision space requires detailed knowledge, data and expertise. I am intigured though by the possibility of setting up a bounded/controlled wiki for subject matter experts with a paralell "public" wiki where folks could weigh in with out-of-the-box creative perspectives on addressing complex risk issues. Further discussion welcome.

[edit] Assistance needed on Dolorimetry

I have run across the article dolorimeter, about devices for measuring pain. Does anyone want to help? It is in sort of sad shape. And I need good reference materials/reviews to work from.--Filll 16:30, 24 January 2007 (UTC)

[edit] Balloon Question

When you let go of an inflated balloon, it zooms off randomly. My question is, could it ever be possible, (though obviously improbable) that the balloon release all its air and propel itself in a perfectly straight line?

Or, does the balloon release naturally require this sort of "whiplash" effect...? Thanks, ChowderInopa 20:19, 24 January 2007 (UTC)

Well, if you look at the article on turbulence and chaos maybe that would help. I don't think there is anything technically stopping a balloon going in a straight line, if you taped a straw into the nozzle to stop it flapping around, and glued some wings to the sides and attached a piece of ribbon to the straw to give a bit of drag at the back end, you could probably make a balloon that went straight, now none of those things fundamentally alter what the balloon is doing, they just constrain the parameters of what it does. I have not had my morning coffee, does that make any sense? Vespine 21:59, 24 January 2007 (UTC)

That does make sense. My argument for a lone balloon, however, is the following: The nozzle pushes air, and thereby pushes itself (this same nozzle side of the balloon) into the remainder of the balloon. Assuming the balloon is not able to maintain its 'shape' against this high pressured force, the back end of the balloon somehow wraps around the nozzle, and is now 'trailing' the nozzle, biasing the whole contraption to one side, and thereby causing it to skew in a certain direction. I just cannot see how the balloon can ever NOT exhibit this, and thereby fly straight. Even if chance allowed it, and the back of the balloon somehow perfectly wrapped around the rest of the nozzle, kind of "inside-outing" the balloon, the excess air would have to be forced out in a certain direction, whichever is the weakest/most forgiving...ChowderInopa 22:36, 24 January 2007 (UTC)

It's not the mouth of the balloon that pushes the balloon forward. The entire balloon acts to expel air from the mouth. So the mouth of the balloon will not "push into" the rest of the balloon. —Bkell (talk) 04:22, 25 January 2007 (UTC)

Touche'ChowderInopa 05:30, 25 January 2007 (UTC)

A balloon will spin and change direction if the thrust is not in line with its center of mass. Edison 18:49, 25 January 2007 (UTC)

[edit] linkage analysis and association analysis

In the area of genetic epidemiology, what is the defanition of the terms linkage analysis and association analysis? what are the objectives of linkage analysis and association analysis? please mention the differences between parametric and non parametric linkage analysis? 20:53, 24 January 2007 (UTC)feld

I'm going to be blunt here: Sorry, but you should do your own homework. if you need help with a specific part or concept, feel free to ask, but please do not post entire questions and expect us to give you the answers. Letting someone else do your work means you learn nothing in the process, nor does it allow us Wikipedians to fulfill our mission of ensuring that every person on Earth, including you, has access to the total sum of human knowledge. Have a look at the articles on Genetics, Genetic_linkage, and Population_genetics. If there is nothing helpful there you might even have to do a Google search[4]--inks ^T 21:20, 24 January 2007 (UTC)

[edit] Black hole

Ok, so i was just listening to the Fightstar song - Grand Unification Part 2 and there is a speaking bit at the end where the person is talking about people learning about black holes and the last line says 'well, gosh, what happens if i drop a black hole on a black hole'

My question is exactly that.. theoritically what would happen if you dropped a black on a black hole? (assuming of course you could accomplish this) Would the size of a black hole make any difference at all?

Fairly simple answers would be appreciated, i'm no physicist, so probably wouldnt understand anything majorly complex. Rickystrapp 20:59, 24 January 2007 (UTC)

I'm pretty sure you just get a bigger black hole. Vranak

I remember reading a hypothetical, ignoring the effect of empty space and all that, the gravity gradient is so steep as you approach the black hole that you would basically get torn apart into just about individual particles. On a very basic level say you were falling in feet first, as you approached the black hole, your feet would experience a much higher gravity then your head. Vespine 21:35, 24 January 2007 (UTC)

Indeed - and we even have an article on this phenomenon, which has the wonderful name of spaghettification. But to answer the original question, I believe Vranak is right, although I couldn't find a reference - if two black holes collide, you just get a bigger (i.e. more massive) black hole. Gandalf61 22:02, 24 January 2007 (UTC)

Yeah - I mean despite their unusual properties, black holes are still made of the same matter as everything else. Add two masses together, and you get a bigger mass. Vranak

I expect that the phone book (MTW) mentions this. --Philosophus ^T 01:00, 25 January 2007 (UTC)

Cheers for that people, maybe not the cool answer i was hoping for but interesting none the less. Rickystrapp 22:18, 24 January 2007 (UTC)

I do imagine that in the process of colliding though you could get some outrageously large tugging forces on account of these two objects with massive gravity being in close proximity. I wouldn't be too surprised, though I am no physicist, if this sort of thing would not send out large amounts of crazy-accelerated matter if there was any lying around nearby. --24.147.86.187

Two black holes merging

NASA has some very good pictures of what should happen when two black holes meet; they just merge to form a supermassive black hole, but I'd imagine that there would be some very intense X-ray emission during the merger. Laïka 08:02, 25 January 2007 (UTC)

Note that the combined black hole has a larger event horizon, but the singularity, as always, has no volume, but only occupies a single point in space. StuRat 09:48, 25 January 2007 (UTC)

Cool picture. Ok so that picture shows when two black hole merge after their paths cross (in a linear sense, for want of a better phrase). Now my understanding of black holes is that they are funnels so to speak, with an opening like a disc. If you dropped one black hole directly into a larger black hole (ie. a small funnel into a slightly larger funnel), is the result still the same? surely the larger black hole would have an effect on the smaller black hole. To my small mind there should be at least some distortion going on, unless i am not fully understanding black holes (the article is quite complex, there don't fancy trying to read it all!)Rickystrapp 11:40, 25 January 2007 (UTC)

No, they aren't funnels. They are super-dense objects that suck up everything due to one of Einsteins theories (can't remember which). The Andromeda Galaxy might be crashing into us in a couple billion years; the supermassive blackhole at the center of our galaxy, and the one in Andromeda, would start swinging around each other until they are unified, forming a new, bigger galaxy, and starting off the (now bigger) black hole. (bad news for us :) | AndonicO ^{Talk · Sign Here} 13:51, 25 January 2007 (UTC)

One question on that pic, it seems like quite a coincidence that the two accretion disks are roughly coplanar, to me. Is there any reason to expect this ? StuRat 10:06, 26 January 2007 (UTC)

[edit] Towing and 4WD

Hello, I have a question about safely towing a 12 foot U-Haul trailer behind a Ford F-150 Four wheel drive pick-up truck. (I checked all the articles just listed but to avail.) The trip will be all-highway coast-to-coast on Interstate 10 in the United States. Rain and possibly some snow are expected. My understanding is that 4WD would not be used in this case. Instead, the transmission should generally be in the drive (overdrive) position. It should be shifted into lower gear on downhill sections as needed to avoid riding the breaks. Does anyone disaagree? Thanks for your pointers. Johntex\^talk 21:16, 24 January 2007 (UTC)

Is it a braked or unbraked trailer? Feel free to put it in 4WD when you're driving on snow.--inks ^T 21:24, 24 January 2007 (UTC)

The trailer is like this one. It says it has "surge brakes". I'm not sure exactly what that means. Is there a maximum speed for driving in 4WD or does it work in all gears? The weather forecast at this moment is not predicting snow, so although I mention snow I consider it a remote possibility - you just never know at this time of year. Johntex\^talk 21:38, 24 January 2007 (UTC)

It is a braked trailer, where the brakes on it are operated by the pressure exerted by the towbar on the trailer when the vehicle is braking. Thus be very careful when braking at speed in snow or slick conditions. I am not familiar with the 4WD setup on an F150 and there is probably significant variation between models and options. The owners manual for that truck should have the answers.--inks ^T 22:28, 24 January 2007 (UTC)

Thanks very much. The owner's manual has been misplaced but your replies have still been helpful. For one thing, I've learned about the brakes. I'll create the appropriate article at surge brakes. If anyone else has more ideas about my towing question, please chime in. Johntex\^talk 23:50, 24 January 2007 (UTC)

I think you're on the right track. You don't want 4WD for highway driving. I agree with you on the transmission too- leave it alone unless you need to downshift to avoid riding the brakes. Be sure to allow extra distance, etc, since you'll be moving a metric crap-ton of weight around and all your maneuvers will be slower than normal. Friday (talk) 23:59, 24 January 2007 (UTC)

No towing experience myself, but my parents have been RVing across the country for five years now, and I've picked up a few things:

Watch your weight. I don't know which F-150 you've got, but with a U-Haul trailer, it's very easy to pack it to the point that you're overweight.
Maintain front-to-back balance. Once you've packed, go to someplace with truck scales and check to make sure that 1) you aren't over your truck's GCWR, and 2) you don't have too much weight on the rear axles. If you have trouble steering while driving to the scales, you've got too much weight on the rear axles.
Use a frame-mounted trailer hitch. A bumper-mounted hitch will rip out about halfway up the third hill you go up.
When going uphill, don't worry about maintaining your speed. Pull over to the right lane and make sure you aren't over-revving or overheating the engine. Downshift when you need to: don't try climbing hills in top gear.
Plot your route in advance, trying to avoid long downhill stretches. Downshift well in advance: you should probably start downshifting at the top of the hill. Feel free to downshift clear to first gear if you need it.
Since you're towing a trailer, follow the posted speed limits for trucks, not the posted speed limits for cars.
If you feel you need AWD for traction, get off the road. Conditions are too dangerous for you to be driving.

--Carnildo 01:38, 25 January 2007 (UTC)

Thanks everyone for the advice! Johntex\^talk 02:59, 25 January 2007 (UTC)

If you have time prior to your trip, have your transmission serviced. Have the fluid flushed, the filter cleaned (or replaced), and new fluid installed. Carry a spare couple pints of the proper transmission fluid with you. Towing a heavy trailer really increases the load on the transmission. Do you know if your truck has the towing package? Does that include a larger-than-stock transmission cooler? If not, consider adding one, especially if your truck is older or has high mileage. It will not be very expensive, and may save you a lot of grief on your trip. 71.112.10.12 13:25, 25 January 2007 (UTC)

More good tips, thank you! Yes, the truck does have the towing package. I think that does include a bigger transmission cooler but I'm not sure. It is a new pretty new truck (2005). I will add the transmission fluid to the list of things to bring along. Best, Johntex\^talk 17:24, 25 January 2007 (UTC)

A friend bought a speedboat and a station wagon to pull it. The boat trailer had surge brakes. He hit the station wagon's brakes at a stop sign, and the brakes on the trailer locked and screeched. He thought there was a truck behind him about to skid into him, so he hit the gas and sped throught the intersection. Moral of the story: get accustomed to the dynamics of the complete towing vehicle and trailer system. Also read up on how to back a trailer, or get someone to show you. and practice in an empty parking lot or some such. You have to cut the wheels to set the angle, then make a correction and straighten the wheels somewhat to back gracefully in a curve. If you try to back without practice, the system will jacknife. I have heard of people having a transmission oil cooler added to a vehicle which will be towing; check your manual or mechanic about that. Edison 04:58, 26 January 2007 (UTC)

Update - made it 500 miles today. No major problems but did have a blow-out on the U-Haul rental trailer. Had to wait over an hour for them to send someone with a spare. My advice to anyone renting a trailer is to inspect your tires as carefully as you can. Have not hit any hills yet, just some rain. Johntex\^talk 05:09, 26 January 2007 (UTC)

[edit] albino mammals

I received photos of two albino moose, via email. How can I discern if the photos are doctored or if in fact it is possible to see two "white moose" (Alberta, Canada) grazing by the side of the road? I looked at the statistics for albino mammals and it's not that common. I would think that in such a large mammal, unprotected in nature that it would not survive well (as the articles on albino animals concur. karin50Karin50 21:42, 24 January 2007 (UTC)

They would be in a nature park, or something similar. Though, I don't know what would predate them, so survival as albinos moose could be possible. Also, it is a genetic disorder, so if it is going to happen, it is possible (1 in 4) that the same parents will have more than one. --liquidGhoul 22:41, 24 January 2007 (UTC)

I believe I have seen the same image as you refer to. I don't know if they are real or not, but there are a few things to consider. Firstly, that (as liquidGhoul states) if a breeding pair have one albino offspring, there is a 1/4 chance that any subsequent offspring will be albino. Secondly, if that breeding pair have other offspring that are not albino, there will be a 2/3 chance each animal is a carrier of an albino allele of tyrosinase. Consider if this single breeding pair was to found a localised population of moose. Then albino alleles will by highly enriched in that local population and occasional interbreeding, even a few generations down the line, would result in albino animals at a much higher frequency than in a large population. Therefore the chances of seeing two albino moose in close proximity is probably much higher than seeing two albino moose independently. The situation I describe happened with squirrels in Kenton, Tennessee, where there is a large population of (so called) albino squirrels. As it happens these may not true albinos, but the principle remains the same. (see Albino Squirrel Preservation Society for more details.)

As an aside, a colleague of mine happens to be considered a world expert on pigmentation. He tells a story of how he was called by a popular morning television show in the UK to comment on a story of a "one in a billion" occurance of a woman who had three albino children. He told them this is actually not very unlikely at all if they all have the same father (which they did). They thanked him and ran the story anyway using the "one in a billion" angle! Rockpocket 23:48, 24 January 2007 (UTC)

Perhaps the one in a billion event would be finding a reporter who isn't willing to sensationalize a story at the cost of the truth. StuRat 09:33, 25 January 2007 (UTC)

As for how to tell if the pic was doctored, trying zooming in so you can see individual hairs (assuming the resolution of the pic is sufficient). It would be quite difficult to change the color of every hair at the edge, so you would likely find dark hairs or missing hairs against the background. This would give it away as a fake. If it's too low res to see individual hairs, then I might be suspicious as to why they can't provide any better pics. StuRat 09:33, 25 January 2007 (UTC)

Shouldn't it be two white mese:?Hidden secret 7 18:25, 25 January 2007 (UTC)

[edit] CO2 emissions in production of concrete

Hi there,

Is it possible to estimate the amount of CO2 emitted in the production of 1 cubic metre of concrete. I have seen reference to between 1.0 and 1.25 tons of CO2 per ton of cement, but of course cement is only a partial constituent of concrete, and how many tons of cement are there in a cubic metre of concrete?

Thanks in advance to anyone who can get their head round this. Fra6jou5 22:00, 24 January 2007 (UTC)

Try the bottom of Portland_cement#Environmental_effects, which gives the amount of CO2 for each kilogram of cement (0.80 kg CO2 per kg finished cement). This site then gives 1506 kg/m^3 for density of cement, and 2371 kg/m^3 for concrete. Google search shows that cement makes up about 10%-15% of the mass of concrete[5]. Using these figures, 15% of the mass of concrete is cement, so 355.65 kg. That gives 0.80 * 355.65 = 284.52 kg of CO2 per cubic meter of concrete due to the cement. Someone check my math. --Wirbelwindヴィルヴェルヴィント (talk) 23:56, 24 January 2007 (UTC)

There are potentially two different questions here.

How much CO₂ is given off by a cubic meter of concrete as it cures, i.e. after you've added a bunch of water to the dry concrete powder? (Answer: not much, I suspect, although I haven't checked Wirbelwind's facts or arithmetic.)
How much CO₂ was released during the production of that one cubic meter of dry concrete powder? Answer: a lot more; concrete powder is produced by roasting lime and other materials in kilns at high temperatures, and this typically requires burning (AFAIK) lots of fossil fuels.

—Steve Summit (talk) 05:45, 25 January 2007 (UTC)

[edit] Deuterostomes and Protostomes

What is the connection between starfish and humans pertaining to Deuterosomes and Protosomes?

By performing a Google search for "humans" + "deuterostomes", I found this site [6]. Check out the explanation under "Background." Feel free to check out deuterostomes and protostomes as well. Chickenflicker---♣ 00:41, 25 January 2007 (UTC)

This online textbook might be useful to you. --JWSchmidt 04:07, 25 January 2007 (UTC)

[edit] In heat...?

Does the term "in heat" refer to the occurance of an increase in body temperature of canine females at the mid point of Ovulation and if so do human females suffer an identical condition every month and if so for how many days does it last? -- Barringa 23:47, 24 January 2007 (UTC)

From Estrous cycle:

The estrous cycle (also oestrous cycle; originally derived from Latin oestrus) refers to the recurring physiologic changes that are induced by reproductive hormones in most mammalian placental females. Humans and great apes undergo a menstrual cycle instead. So females suffer... dun dun dun... the period. --Wirbelwindヴィルヴェルヴィント (talk) 00:05, 25 January 2007 (UTC)

Note that under the titles Differences from the menstrual cycle and Estrus in the Estrous cycle article, the actual phrase "in heat" is discussed. Chickenflicker---♣ 00:44, 25 January 2007 (UTC)

See [7] for a discussion of the small change of basal body temperature in the human female at the time of ovulation. Women seeking to become pregnant or to avoid becoming pregnant sometimes use this as an indicant of ovulation, but it can be deceptive, since other things can cause the small change. The Online Etymology Dictionary [8] says "heat" meaning "sexual excitement in animals" dates back only to 1768. I doubt that anyone had a basal temperature thermometer to use on animals back then, and the term probably was more of a metaphor. Edison 18:56, 25 January 2007 (UTC)

[edit] Weight of electric aircraft power source...?

Lead acid batteries are too heavy no matter how efficient an electric motor would be as well as metal halide and probably lithium polymer but what about airgel based batteries like the Boostcap from Maxwell Technologies in San Diego. If the price was lower would it not be feasible to build a full scale passenger or cargo carrying electric powered aircraft? -- 71.100.10.48 23:59, 24 January 2007 (UTC)

It is certainly possible to build an aircraft that runs solely on battery power. I once did a design project where we demonstrated that flying overnight on battery power was feasible. Two questions come to mind though: Why would one build an electric-powered plane when gasoline or kerosene-burning aircraft fill those roles so well? Also the expense of FAA-certifying a new airplane with a radically new powerplant would be very high, especially if the advantages over conventional aircraft are small. Of course an electric aircraft would have advantages, particularily that it would be very quiet, hard to detect by infrared, low vibrations, etc. anonymous6494 03:23, 25 January 2007 (UTC)

I'm speculating that the Energy density of an airgel based Supercapacitor (3,000 farads). may be near the Energy density of Gasoline In fact I'll post this as a new question shortly. Not only is the fuel's weight to energy ratio potentially so much greater than Gasoline but the risk of liquid fueled fire is eliminated in the event of a crash, etc. -- 71.100.10.48 07:26, 25 January 2007 (UTC)

There are several conceivable possibilities for using SuperCaps. The usage as energy source for a model airplane is probably rather the exception. On the other hand NuinTEK has really big devices with 60 F which are superior to batteries in energy density by a factor of 5 to 10 according to NuinTEKs technical infos. Using some of these, connected in series and in parallel to get sufficient voltage and capacity, may make it even possible to launch a small radio controlled airplane. -- 71.100.10.48 07:48, 25 January 2007 (UTC)

One advantage of liquid fuel, however, is that the weight of the plane decreases as the fuel is burned. Unless you jettison the batteries as each is drained, you can't duplicate this with electrical power. There may be some advantages to an electrical plane, however, such as the ability to recharge batteries. A lightweight, high altitude, slow moving reconnaissance plane that could gather solar power by day and run on batteries at night is one application. Such a plane might be able to stay in the air indefinitely. Tiny recon planes to be used to fly over a battlefield, or even into a building, might also benefit from electrical power, as it's more efficient on smaller scales than combustion engines. StuRat 09:19, 25 January 2007 (UTC)

Something to keep in mind about these EDLCs is that they generally operate at fairly low voltage because of the extremely thin dielectric. Of course you can string them together in series to provide higher voltage operation, but if you recall your basic lump circuit models, this will also decrease the effective capacitance of the component. For high current loads like motors, I think electrochemical batteries are still going to give the best energy storage to weight ratio (though I don't have any figures off the cuff to verify this). -- mattb @ 2007-01-25T14:30Z

A similar question was recently asked and answered, and my analysis was that the increase in energy stored at the higher voltage rating from a thicker dielectric more than makes up for the decrease in capacitance. Go with higher voltage caps for higher energy density, rather than maximum capacitance at lower voltage. Edison 19:01, 25 January 2007 (UTC)