Wikipedia:Reference desk archive/Science/2006 June 11

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[edit] Spam

This may be going out on a limb, but I have a gmail account I am trying to fill. I get around 500emails a day atm and I want to increase this, any ideas?

Cheers.Raven.x16 02:38, 11 June 2006 (UTC)

Post your address all over the place and sign your address up to a bunch of those free i-pod websites. Something such as [1] should work quite nicely. A Clown in the Dark 03:11, 11 June 2006 (UTC)

  • I'm curious as to why you want to do this. You wouldn't even have time to read all those emails. - Mgm|(talk) 08:45, 11 June 2006 (UTC)

Are you trying to see if you really have those 2.whatevef gigabytes of storage space or just trying to get viruses on a friends computer?

Lol - i figured someone would aks this...I have no way to proove it but im just trying to see how many i can fit in, and if i can outdo the gmail "always increasing" rate. Raven.x16 09:28, 11 June 2006 (UTC)

Neopets (8years ago now) meant my first email address got/gets ~50+ spams a day.

My Neopets-linked account doesn't get much spam, but that might be because I was careful not to sign up for third-party sponsors during registration. Worth a try, though. I think you'd have more luck signing up for porn sites (if it's legal for you, of course). --AySz88\^-^ 16:22, 11 June 2006 (UTC)
What do you mean, "signing up"? Have you no faith in the egomaniacal greed of porn sites? Just wander through them for awhile, they'll find a way to find you. Black Carrot 16:49, 11 June 2006 (UTC)
How? --Bowlhover 02:10, 12 June 2006 (UTC)
One sure way is to get the shortest, most predictable email address available. firstname_lastname@gmail.com style accounts are probably the worst for spam.  freshofftheufoΓΛĿЌ  02:44, 12 June 2006 (UTC)
This is a cool experiment. I would like to know how it turns out. I recently read an article where a guy tried to delibarately expose a computer to as much malware as possible. ike9898 16:56, 12 June 2006 (UTC)
You're thinking of this article over at Wired mag. Hilarious. Tyrhinis 15:29, 18 June 2006 (UTC)

[edit] Specific weight of Helium under pressure and different temperature.

At what presure is the specific weight of Helium equal to air, Temperature 20C, 0C, -50C and 100C. Thank you. Mike Engel.

This isn't a complete answer, but it may help.
At 20C, Air is 8.273 (lb/ft^3)*10^-2
At 0C, Air is 8.633 (lb/ft^3)*10^-2
Source: http://www.engineeringtoolbox.com/air-desity-specific-weight-d_600.html
- I know it's not much, but it may help get you started, and the site may help you further.Raven.x16 03:14, 11 June 2006 (UTC)

From REFPROP, NIST standard reference database 23, version 7.1 (beta) (Sorry about the formatting).
Air
T P Density
(°C) (atm) (kg/m³)
-50.000 1.0000 1.5840
0.00000 1.0000 1.2927
20.000 1.0000 1.2043
100.00 1.0000 0.94563

Helium
T P Density
(°C) (atm) (kg/m³)
-50.000 7.2804 1.5840
0.00000 7.2659 1.2927
20.000 7.2625 1.2043
100.00 7.2528 0.94563

[edit] Why isn't water flammable?

Water is made out of hyrdrogen and oxygen which are both very flammable, so why doesn't water burst into flames? A Clown in the Dark 03:08, 11 June 2006 (UTC)

The valance shells of the three atoms are altered, and it produces a different chemical. Kind of like how when Na and Cl come together... Na explodes on contact with water, and Cl is a poison gas. See this link for a great answer [2] from the US DOE.— The Mac Davis] ⌇☢ ญƛ. 03:21, 11 June 2006 (UTC)


A google search led me to this: http://www.bizarremag.com/ask_bizarre.php?id=365
In summary, the reason hydrogen and oxygen are flammable is because they have a lot of
stored energy - when they combine, they do so exothermically, releasing energy in the
process. - The resulting molecule, good old H2O is low energy - and as such no longer burns.
Hope that helps.Raven.x16 03:21, 11 June 2006 (UTC)
Water is made of hydrogen and oxygen because it is the result of hydrogen burning in an oxygen rich environment. You can think of it like burning wood. The result, along with as well as CO2 and water vapor, is ash, which does not burn. Or think of burning propane: the result is CO2 and water vapor, and often some CO and elemental carbon, all non-flammable. As Raven.x16 pointed out, hydrogen and oxygen have a lot of stored chemical energy, which is released by burning (the heat and light); the product resulting from any combustion has much lower stored chemical energy, so it is not flammable. --Ginkgo100 talk · contribs 03:36, 11 June 2006 (UTC)
Because so are the potentials of interactions. :) Speaking seriously, in a molecule of water atoms are binded together by electromagnetic forces -- and the "bond" is strong enough (by the way, could anyone answer what is the energy of it in say electronvolts? Thank you in advance!). So for atoms of H or O to take part in any reaction, first this "bond" must be destroyed, i.e. you must free the atoms first -- and to do it you need energy. So reactions with water molecule are much harder than with pure O or H atoms (or O2 and H2 molecules). ellol 07:51, 11 June 2006 (UTC)
The standard heat of formation of water from H2 and O2 is 241.8 kJ/mol or 2.50608036 electron volts. I assume you want to completely disassociate all the atoms for the total energy, so add half the heat of formation of O2 from O (half of 247.5 kJ/mol, or 1.28257835 electron volts and that of H2 from H (217.94 kJ/mol or 2.25878889 electron volts) to get a total of 6.0474476 electron volts. :) --AySz88\^-^ 16:10, 11 June 2006 (UTC)
And now that I turn the page, my reference tables actually have an average bond energy table - 463 kJ/mol for an O-H bond, which is 4.80 electron volts per bond (and there are two per H2O), but that number isn't what I got.... >.< - I guess I'd trust those tables more. --AySz88\^-^ 01:49, 12 June 2006 (UTC)
  • Water is made of hydrogen and oxygen atoms. It's hydrogen and oxygen molecules that are flammable, because they consist of two of the same atoms. As soon as they are broken to form a water molecule their properties change. However, there's an explosive so hot that if you set it on top of a huge block of ice, it burns right through and makes the water (ice=water) so hot it turns back into hydrogen and oxygen and explodes (seen it on Brainiac). But you need a temperature of over 1000 degrees centigrade for such an explosion.
Oxygen isn't flammable, as such. Philc TECI 09:21, 11 June 2006 (UTC)
One of my science teacher's favourite tricks was the hydrogen/oxygen explosion. All that remained were a few drops of water. A more elaborate device, such as [this, separates the water out first.--Shantavira 10:38, 11 June 2006 (UTC)
Yes, lol, the incredibly elaborate electrodes in water. :-P Philc TECI 15:53, 11 June 2006 (UTC)
Oxygen doesn't burn, it allows combustion to occur as a oxidizing agent. Titoxd(?!?) 01:45, 12 June 2006 (UTC)

[edit] HIV

User:Mac Davis/HIV What is up with this? I surely do not have a 5/10000 chance of getting infected by HIV through penile/vaginal intercourse? — The Mac Davis] ⌇☢ ญƛ. 03:19, 11 June 2006 (UTC)

Check the title of the second column: Estimated infections per 10,000 exposures to an infected source. Each time you have intercourse with an HIV positive individual, those are your odds of becoming infected yourself. TenOfAllTrades(talk) 03:27, 11 June 2006 (UTC)
That value seems too low - I would think far more than 0.05% of those who have intercourse with an HIV-positive person would be infected. --AySz88\^-^ 04:31, 11 June 2006 (UTC)
You could always check the sources. Bear in mind this is per act. You could increase the chances tenfold in the course of a week. --Shantavira 09:51, 11 June 2006 (UTC)
It does seem to counter the common perception of the virus as being deadly on contact. But, in looking at the pubmed source, it seems like a legitimate study. It is worth noting that there are several factors that can increase the odds, including age, advanced state of the disease, etc.
Has anyone seen figures on rates of transmition through cunnilingus? ike9898 16:52, 12 June 2006 (UTC)
That would seem to be missing in the chart, isn't it? I would suspect that it's somewhere on the order of fellatio, but that's mere speculation. Also, it's not quite clear to me which party is the "receptive" party in fellatio, but I guess the "insertive" clears it up. And of course, there's the question of spitting versus swallowing -- I'd expect that to be a significant factor.
There are other complicating factors that influence the likelihood of spreading HIV through sex. For instance, how infectious HIV-positive people are varies between cases and over time. Also, infection with other sexually transmitted diseases increases the risk of transmission. Finally, there are various sexual practices that may increase the risk of transmission, for instance dry sex. See our AIDS article for more information. --Robert Merkel 03:22, 13 June 2006 (UTC)

[edit] Suffocating sensation when tired

After a long and tiring bicycle ride, I often get a sensation similar to smelling cigarette smoke from 6 m away. What is this smell? I don't think it's a hallucination, since it disappears if I breathe through my mouth.

I know that most of you think I'm a troll, because of the question I asked about suicide (and also because of several other reasons). I assure you that it was not a hoax, but please forget about the incident anyways. Now that you know so much about me, I often feel embarassed when making edits, and therefore do not make edits if I feel they'll embarass me. --Bowlhover 03:59, 11 June 2006 (UTC)

It actually hadn't crossed my mind that you might be a troll. So, is this sensation one of "suffocating", or is it an odor "similar to smelling cigarette smoke"? And don't be too sure about the hallucination part. Not to say you're crazy or anything, but it's remarkably easy to fool your nose into smelling things. Many's the time during the summer months I've relaxed to the entirely nonexistent smell of eggnog. If it's a smell, have you considered it might be sweat? Black Carrot 16:46, 11 June 2006 (UTC)
I'm very sensitive to cigarette smoke, so the smell of the smoke is suffocating. I haven't considered the possibility that the smell (if it exists) might be sweat, but no other sweating person smells like smoke. --Bowlhover 01:06, 12 June 2006 (UTC)
Well, continuing with the detective work, I move to the next item in your description: the bike itself. Have you tried putting your face near the tires and seeing if the smell gets worse, or maybe the chain? If you carry a water bottle, could you trace it to that? And, of course, it's possible someone happens to smoke a lot, or burn wood/leaf/trash piles (if you live in that kind of area) around the time you go for rides. BTW, by "6 m", do you mean miles or meters? Black Carrot 03:47, 12 June 2006 (UTC)
Are you asthmatic? Is it possible that you're short of breath after either a hard bicycle ride or cigarette smoke? Maybe that's why you smell the same? – b_jonas 10:11, 12 June 2006 (UTC)

[edit] Psychology Experiment

What is the name of the psychology experiment that showed children a video of someone beating up an inflatable clown and then allowing them to do the same? 69.40.252.95 05:18, 11 June 2006 (UTC)


Bobo doll experiment. --vibo56 talk 19:17, 11 June 2006 (UTC)

[edit] SquirrelMail

I just found out about SquirrelMail. I looked at the screenshots and the interface looks beautifully simple, and I want to try this out. But there is no signup page on the site, and I can't find one. Are there any free webmail sites out there that use squirrelmail? --pile0nadestalk | contribs 05:21, 11 June 2006 (UTC)

It looks to me as though you should just go to their homepage and click on Download. Did you try that? --Shantavira 10:52, 11 June 2006 (UTC)
Except that it's a webmail interface, not a standalone POP client. —Bkell (talk) 20:07, 11 June 2006 (UTC)
It appears the questioner doesn't fully understand what SquirrelMail is. It is a set of webpages that you put on your server so you can check the email on your server. That means that you must have a webserver and email server to put SquirrelMail on. It is not a free webmail service like Hotmail, YahooMail, or GoogleMail. --Kainaw (talk) 19:45, 11 June 2006 (UTC)
Right, but there might be some webmail service out there that uses SquirrelMail as its interface. —Bkell (talk) 20:09, 11 June 2006 (UTC)
No big email providers, no. -- Миборовский 04:06, 12 June 2006 (UTC)
I'm sure there are plenty of smaller webmail companies that use SquirrelMail. Some friends of mine run a site called Slashmail that uses it. (I won't post a link, since I'm not sure that it would not be considered blatant advertising.)
GNU-Darwin offer SquirrelMail accounts to people who donate to the project [3]. Ojw 15:22, 18 June 2006 (UTC)

[edit] Question about plecostomus (a type of fish)

I posted a question on Talk:Plecostomus about two plecos I have — asking whether people think they're the same species or not. I've got several photos of both fish posted over there. Rather than repost everything over here, perhaps some fish experts could go have a look over on Talk:Plecostomus and let me know what you think? Richwales 05:59, 11 June 2006 (UTC)

Sorry, I don't think there are any fish taxonomists currently reading the reference desk. Good luck finding out though! --Ginkgo100 talk · contribs 18:54, 12 June 2006 (UTC)

[edit] Embedd flash into powerpoint.

Does anyone know the name or websites offering softwares which can embedd flash files into powerpoint (ppt) files? Thank You.

I'd suggest the Microsoft Knowledgebase.--Anchoress 09:14, 11 June 2006 (UTC)
You don't need any special software - see this tutorial (it works for all kinds of flash files). I think it probably works best if you save the flash to your disk first, though I've been able to get it to use a URL too. --AySz88\^-^ 16:16, 11 June 2006 (UTC)

[edit] Maximum Heart Rate and Aerobic Threshold

I'm not asking this question because of my own fitness routine, so no need to tell me to ask my doctor. ;-) What I'm wondering is if there's normally a correlation between MHR and AT? I know most exercise advice puts the top percentage of MHR for aerobic exercise at 85%. I read on the triathalon page that athletes working at 92% MHR were working anaerobically; I had thought you had to be closer to 100% before hitting anerobic, but is there a predictable threshold? I don't mean it would be exactly the same for every person, but is there a ballpark?--Anchoress 08:43, 11 June 2006 (UTC)

[edit] Salvia divinorum

What negative, if any, effects have been shown in the use of Salvia divinorum? In regards to health, both physically and mentally.

A significant amount of information relating to salvia can be found at http://www.erowid.org/plants/salvia/salvia.shtml (especially http://www.erowid.org/plants/salvia/salvia_faq.shtml#health). Though I cannot provide a full answer, I can suggest that it is likely not terribly good for your lungs when smoked as it is a bit slow to absorb so you really have to hold it in for a long time and it must be burned at a high temperature for the salvinorin to be released, which can probably cause burns if it isn't smoked through a water pipe. 128.197.81.181 16:09, 11 June 2006 (UTC)

[edit] Baby seagulls have just hatched - what's the best food to give to the mother/father gull?

The herring gull nest on my roof now contains two tiny, fluffy little chicks. I've been feeding bread and kitchen scraps to the parent birds ever since they decided to nest here, but now the babies have hatched, I want to make sure that they get the best diet to ensure that both of them survivie and grow to be strong, healthy birds. What is the best food to give to the mother and father gull, so that they can regurgitate it for the chicks?

I'm pretty sure that bread will do. But remember that "caffeine, alcohol, chocolate, avocados, rhubarb, sprouted limas, fava beans and navy beans" are unsafe for most birds. They would probably appreciate fish if you can get some. But you also must remember that the gulls are most likely self-sufficient and will scour for their own food to feed their babies. You probably don't even have to worry about them, unless the parents are incapable of finding their own food or are hurt, etc. Just enjoy watching them in their nests. ;) --Proficient 14:45, 11 June 2006 (UTC)
Chicks need a high protein diet, so bread is really not that good. Their natural diet is, of course, fish, so they will appreciate any scraps from the local fishmonger.--Shantavira 15:48, 11 June 2006 (UTC)
Bread is not that good for gulls. It fills them up without providing much in the way of nutrition. Whilst it doesn't really harm them as such, there are better things you can be feeding them (e.g. meat or fish). Personally, my gulls always get cooked beef or pork. Just don't go mad with it - like I did... ;) --Kurt Shaped Box 19:40, 11 June 2006 (UTC)
Agreed. Actually, I would've thought the common name of the species would be a pretty good hint. —Ilmari Karonen (talk) 17:10, 12 June 2006 (UTC)
In that case, I can't resist asking what you would feed a Dolphin Gull? --Shantavira 17:31, 14 June 2006 (UTC)
Well, according to the article their diet includes carrion, so presumably they would eat dolphin if they found a dead one somewhere...
In fact, gulls are actually known to attack live whales — though not dolphins as far as I know: see f.ex. [4]. —Ilmari Karonen (talk) 18:06, 14 June 2006 (UTC)

[edit] Popular Mechanics

I've been going through my back issues of Popular Mechanics (I'm in year 2000 right now), and I find myself distressingly unable to determine whether the articles are astounding and innovative, or total bull. How do I track down sources on a magazine that has never given, and will never give, sources? For instance I have it open right now to an article on the "Lenticular Reentry Vehicle", cover story to the November issue. I've done what I can to track this thing down (which is very little): I've searched Wikipedia, and I've searched Google. I have yet to find a single site discussing it (including Wikipedia) that didn't use the article itself as the one and only source. And another: in October of that year, they have an article describing Ning Li's attempts to use a "Bose-Einstein condensate" to fight gravity. It's been six years since then, so there must be some kind of results from the project, even if they're negative. How do I track them down? Black Carrot 17:35, 11 June 2006 (UTC)

Searching is certainly good, but you should also consider writing to the PM editors and the article author; you might get follow-up information that way. — Lomn Talk 19:11, 11 June 2006 (UTC)
I've also had similar qualms about PS-like magazines. As a popular magazine they are often printing rather big-sounding stories, often hinting at unrealized links to larger scientific questions, which always leave me wanting some kind of follow-up. I guess they just put their duty to entertain readers above educating them, and thus resolve to not print boring negative results whenever possible. After all, it is Popular Science and not Disciplined Science.  freshofftheufoΓΛĿЌ  02:36, 12 June 2006 (UTC)
Yeah. I don't really want to e-mail them specifically, though, since I'm getting the feeling I'll want to check up on at least a dozen articles per issue. I think they'd get tired of it after awhile, if they helped at all. Anything else? Black Carrot 03:32, 12 June 2006 (UTC)
Did the article by any chance mention the name of any of the researchers? Or perhaps the school, institution? It's usually pretty easy to contact researchers at universities through listings on their homepages.  freshofftheufoΓΛĿЌ  05:51, 12 June 2006 (UTC)
That's a good idea. The first person I tried it on seems to have dropped off the map (except some fan sites, for some reason), though. I'll keep trying.
I have to say, I'm a bit disappointed. It seems like the people here would be good at finding stuff out. Doesn't anyone know of reliable science sites I could look some of this stuff up on? Black Carrot 02:16, 13 June 2006 (UTC)
How's this for a basic rule. If the only place it's published is Popular Mechanics, treat it as slightly, but only slightly, more credible than Nexus. Like Popular Science, they have a history of transmogrifying wild speculations into supposedly rock-solid predictions; where do you think all the flying car articles come from?
In this specific case, the source of the article seems to be a combination of a formerly classified document retrieved under FOI, and a healthy dose of speculation based on historical research, much of which could well have been done on Wikipedia. Might I suggest that you write to the magazine and ask for a copy of the document they used, and suggest that in future they might place sources like that on their website? --Robert Merkel 04:11, 13 June 2006 (UTC)

[edit] Different colours of cigarette smoke?

Just spent the afternoon sat on my sofa listening to music, smoking and chilling out whilst watching the clouds of smoke floating around the room in the sunlight. It was then that I noticed something that I'd never noticed before. With the sun behind it, the smoke rising from the tip of the cigarette has a blueish tinge to it, whilst smoke held in the mouth but not inhaled is white - and exhaled smoke is light grey in colour.

Anyone know why this would be? --Kurt Shaped Box 19:36, 11 June 2006 (UTC)

Something to do with moisture? I seem to recall an Isaac Asimov or Philip K Dick story in which the robot's disguise is foiled by the colour of his cigarette smoke. The rational given was the moisture droplets in the smoke. Skittle 21:07, 11 June 2006 (UTC)
Small smoke particles appear bluish-colored, but only if the particles are smaller than wavelengths of visible light, see Rayleigh scattering and Tyndall effect. If smoke particles grew larger, they'd change from bluish-colored to white. I'd bet that the smoke in your mouth is acting as seeds for the growth of water droplets. The soot particles would gather water vapor from the air and start increasing diameter, also turning from bluish to whitish color. --Wjbeaty 08:05, 15 June 2006 (UTC)
I'd cast my vote for an optical illusion. There isn't much in that article about color illusions, but there's some. Smoke held in your mouth is against a background of black or dark red, and is seen as lighter than it is. Smoke in the air is in its normal habitat, and is seen correctly, as light gray. Smoke against sunlight has to deal with 1)being against a strong light source (darker), and 2)being against yellow (bluish). Black Carrot 22:11, 11 June 2006 (UTC)
Caused by the imprint left on your eye by the brighter yellow sunlight, gives everything a blue hint, I should suspect. Philc TECI 22:42, 11 June 2006 (UTC)
That's an interesting observation. --Proficient 00:45, 12 June 2006 (UTC)

[edit] Food coma

The article is only a stub, so I'm wondering if someone here might provide me a bit more information. The article explains that the brain's intake of oxygenated blood is restricted so that the stomach can metabolize large quantities of complex carbohydrates. Is the reason for sleepiness then simply because the brain can't get enough oxygenated blood and simply begins to shut down body systems so as to use less energy? When I eat way too much carbo-laden food (Chinese food, for example), I often drift off to sleep for several hours while still at the table, and I find this topic quite interesting. There's not much info online, though (perhaps there's a technical term for food coma that I don't know.). Thanks in advance, Johnny. 69.212.22.157 19:55, 11 June 2006 (UTC)

There are a number of potential effects of food on arousal levels. There are some specific metabolites (e.g., tryptophan) with "dormitive properties" a la Moliere. Carbohydrates can affect level of autonomic arousal as well. alteripse 02:33, 13 June 2006 (UTC)

[edit] Black holes - yet again... :)

What would happen if two black holes of similar mass were to collide head on? --Kurt Shaped Box 22:47, 11 June 2006 (UTC)

They would merge into one. No fireworks. Titoxd(?!?) 01:47, 12 June 2006 (UTC)
(after edit conflict) I think the collision would be totally uninteresting. The two black holes will spiral into one another and merge into one mass, and that's about it. No EM-emitting accretion disc would be formed because neither black hole can emit/reflect radiation. --Bowlhover 01:55, 12 June 2006 (UTC)
Actually, according to Eric Weisstein's site the two-body problem for black holes hasn't admitted an analytic solution (ie. we don't know exactly what happens), but from a link in the black hole article to something from the Discovery Channel shows that a computer simulation has suggested that the collision would cause "rippling" gravity waves. Confusing Manifestation 01:59, 12 June 2006 (UTC)
What "waves" don't "ripple"? Black Carrot 02:10, 12 June 2006 (UTC)
The ones I do with my hand.  freshofftheufoΓΛĿЌ  02:21, 12 June 2006 (UTC)

As ConMan says, some of the details of what happens when black holes collide are unknown. What happens to the singularities, for example? It's an open question. It's true that there will be large gravitational waves, though. This happens whenever very massive bodies collide. -lethe talk + 05:09, 12 June 2006 (UTC)

'Irresistible force vs. imovable object' comes to mind WRT the singularities, as does the image of a snake trying to eat itself, for some reason. Gah! My head hurts even trying to think about trying to describe the concept of two 'infinite gravitational wells' of 'infinitely small (zero) volume and infinitely large density and temperature' being pulled into one another. :) --Kurt Shaped Box 06:01, 12 June 2006 (UTC)
Yup, it's a thorny issue, and it's perfectly reasonable to imagine that there is no solution. It's been known since the 19th century that the classical theory of charged point particles contains inconsistent solutions. You can find solutions to Maxwell's equations where two point particles chase each other going faster and faster, a consequence of the fact that a point particle is really a singularity in the charge density. It's reasonable to expect that the same thing happens to singularities in the gravitational field. The issue with point charges was resolved with renormalization in the quantum theory, and one might expect that to figure out what happens to gravitational singularities will require a quantum description as well. We don't have one at present. -lethe talk + 06:19, 12 June 2006 (UTC)
Do you reckon that God knows? ;) --Kurt Shaped Box 06:23, 12 June 2006 (UTC)
Well, I think that He doesn't believe in the theory of relativity, and isn't clever enough to understand string theory. I mean, let's work on getting Him to understand the theory of evolution, and then we'll think about introducing Him to black holes. -lethe talk + 06:55, 12 June 2006 (UTC)
Didn't you hear? It was God that initiated the big bang. Unfortunately, He didn't have time to see whether it was good or not, as He was immediately anhiliated by the intense heat and radiation. :) --Kurt Shaped Box 07:34, 12 June 2006 (UTC)
Nah, that's not what I heard. Word on the street where I'm from is that God created the world in 6 days about 5000 years ago, which makes Him about 13 billion years late for the big bang. -lethe talk + 07:52, 12 June 2006 (UTC)
From the POV of an external observer, does it matter whether the singularities merge or not ? Could they even tell ? Sum the masses/charges/angular momenta of the merging black holes and you get the mass/charge/angular momentum of the merged object. According to the no hair theorem, those parameters completely characterise the final black hole. I don't think an external observer can tell anything about the distribution of mass inside the event horizon. Gandalf61 08:45, 12 June 2006 (UTC)
Yeah, it matters. The geometry of spacetime is quite different when there are two black holes. -lethe talk + 10:40, 12 June 2006 (UTC)
But once the event hroizons have merged, how can an external observer tell whether there are one or two singularities ? If they could tell, wouldn't this be an exception to the no hair theorem ? I know the universal validity of the no hair theorem is controversial, but finding a simple exception would still be big news - especially if it did not involve quantum effects. Gandalf61 11:00, 12 June 2006 (UTC)
If you find a way to merge the black holes without using quantum effects, then you've already made headlines, no matter what whether you've managed to conform to no hair or not. -lethe talk + 14:21, 12 June 2006 (UTC)

[edit] Meaning of gull squawks/caws/cackles/etc. and body language?

Gulls seem to have a very complicated 'language', involving both vocalizations and body posture (i.e. the same call can mean different things in different situations depending on the position of the head and wings at the time). Is there an online resource that explains 'gull language' in detail? I'm quite close to some of my local gulls, having developed a rapport with them by feeding them on a daily basis. There is one bird in particular that I raised as a chick which is definitely trying to communicate with me. So far, I've figured out what a few of the calls directed towards me mean (e.g. lowering the head and flicking the beak whilst making a cheeping noise means 'I'm hungry/feed me', standing with an alert pose whilst making an 'ag ag ag' noise is some sort of greeting, and 'MWAAAK!' with wings slightly spread whilst hanging around outside means something like "Hey! We're here waiting for you!" etc.), but the majority of gull-to-gull communication eludes me (aside from the obvious alarm calls, 'let's gang up on that hawk' and 'back off'-type stuff). Sometimes the gulls will sit gesturing and gabbling at each other for minutes at a time...

Someone *must* have studied this at some point. Any help would be appreciated. --Kurt Shaped Box 23:20, 11 June 2006 (UTC)

Indeed. Some enthusiast would have probably studied this before. Maybe the language can be unique to gulls in certain areas and differ elsewhere. --Proficient 00:48, 12 June 2006 (UTC)
I did once read somewhere that gulls from different parts of the world do not seem to regognize, or react to each others' calls. With regards to the gull I raised, I get the feeling (without trying to overly anthropomophize things) that she's trying to 'make me understand' something - she makes a series of soft clucking noises towards me that I've never heard from another gull before and gestures with her head constantly. She'll also peck at my shoes and legs when she's hungry. I had a very close bond with this bird ever since she was a couple of days old and I'm certain that she remembers and recognises me as an individual. Sometimes I wish I could think like a gull... --Kurt Shaped Box 06:15, 12 June 2006 (UTC)
I take it you've read Jonathan Livingston Seagull. --Shantavira 07:31, 12 June 2006 (UTC)
Actually, no. It's one of those books that I've been meaning to read for ages... :) --Kurt Shaped Box 07:37, 12 June 2006 (UTC)