Wikipedia:Reference desk/Archives/Science/2006 June 4

Humanities Science Mathematics Computing/IT Language Miscellaneous Archives

The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions at one of the pages linked to above.

< June 3 Science desk archive June 5 >

Mother seagull refusing to feed her baby

What's the deal here? Her baby left the nest a couple of weeks ago and now the mother gull won't feed him. He comes up to her cheeping for food and she just ignores him and turns her back on him. He tries to peck at her beak and she snaps at him. I'm worried about the little guy now.

Hello Mr. Seagull person. This is normal behaviour. All birds leave the nest and then are fed by the parents for a few weeks. At some point the parents go on to the second brood, and the baby birds don't like it. Some harsh actions are taken. At our cottage, we have baby ravens who are leaving the nest, and they are soooo loud, the whole lake can hear them. --Zeizmic 02:39, 4 June 2006 (UTC)

And "kids" in their twenties who try to move back home frequently find that Mom and Dad have changed the locks, LOL. StuRat 02:27, 5 June 2006 (UTC)

Kinetic Energy Problem

Question: One car has twice the mass of a second car, but only half as much KE. When both cars increase their speed by 6.m/s, they have the same KE. What were the original speeds of the two cars? [Answers are 4.2m/s; and 8.5m/s]

I've tried a few different things but it hasn't given me any results. I know that if double the mass, I double the KE, and if the speed is doubled, then KE becomes four times as much. I'm guessing that if the mass is doubled, and the KE is half, that the speed must be 1/4th. I've tried this with algebra but again it hasn't given me anything useful. I've been unsure of what to do with the 6.0m/s. If anyone could help me out, I'd appreciate it. Thanks C-c-c-c 00:53, 4 June 2006 (UTC)

Let M be the mass of one of the cars, and V1 and V2 their initial velocities. I think you know enough to write down two equations involving these three variables (one for the situation at their initial velocities, the other for the situation at the increased velocities), which seems like one too few. However, if you write these down and think a bit, I suspect you'll figure out how to proceed. -- Rick Block (talk) 02:05, 4 June 2006 (UTC)

Hmmm...maybe it's been too long since I did problems like these, but I don't think the answer provided is correct. I may be embarrassing myself at this point though :)--Robert Merkel 02:28, 4 June 2006 (UTC)

Kinetic energy might help refresh your memory. -- Rick Block (talk) 02:35, 4 June 2006 (UTC)

M1 = 2 * M2
K1 = 1/2 * K2

K1 = 1/2 * M1 * V1^2
K2 = 1/2 * M2 * V2^2

J1 = 1/2 * M1 * (V1 + 6)^2
J2 = 1/2 * M2 * (V2 + 6)^2

J1 = J2

Find V1 and V2

===============================
Solution:

         M1*((V1 + 6)^2)
    J1 = ---------------
                2

Solve for M1

             2*J1
    M1 = ------------
         ((V1 + 6)^2)

    eliminate J1 


             2*J2
    M1 = ------------
         ((V1 + 6)^2)

    eliminate J2 

         M2*((V2 + 6)^2)
    M1 = ---------------
          ((V1 + 6)^2)


    eliminate M1 


         M2*((V2 + 6)^2)
2 * M2 = ----------------
           ((V1 + 6)^2)


So we have

       (V2 + 6)^2
   2 = ----------
       (V1 + 6)^2


Solution

   V2 = +1 * sqrt(2) * (V1 + 6)  - 6
or
   V2 = -1 * sqrt(2) * (V1 + 6)  - 6

Ohanian 03:29, 4 June 2006 (UTC)

Hey Ohanians, thanks so much, but I have one question. How do I solve for v2 in the last equation if I don't have v1, or am I ignoring some other aspect? Thanks! C-c-c-c 03:38, 4 June 2006 (UTC)

Sounds to me like you need to brush up your algebra. You cannot solve for V2 because V1 is NOT BINDED to any numerical value. Your question only gave numerical value of 6 for the increase in velocity. No other variables in your question is BINDED to any numerical value. Is this a homework problem? Ohanian 04:16, 4 June 2006 (UTC)

No, it's a question out my physics textbook and I'm doing some studying for my exam. Okay, but if I can't solve for V2, then why does my textbook give me numerical answers? C-c-c-c 04:22, 4 June 2006 (UTC)

         K2
#2: K1 = --
         2

2-> eliminate K2 using 4
Solving equation #4 for (K2)...

         M2*(V2^2)
#2: K1 = ---------
             4


2-> eliminate K1 using 3
Solving equation #3 for (K1)...

    M1*(V1^2)   M2*(V2^2)
#2: --------- = ---------
        2           4

2-> eliminate M1 using 1
Solving equation #1 for (M1)...

                M2*(V2^2)
#2: M2*(V1^2) = ---------
                    4

2-> replace M2 with 1

           (V2^2)
#2: V1^2 = ------
             4

2-> V2

                     1
#2: V2 = ((4*(V1^2))^-)*sign1
                     2

============================

V2 = +1 * sqrt(  4 * V1^2  )
or
V2 = -1 * sqrt(  4 * V1^2  )

Ohanian 04:25, 4 June 2006 (UTC)

Now put those two possible solution sets into the same graph. Solution set A and solution set B

Solution set A

   V2 = +1 * sqrt(2) * (V1 + 6)  - 6
or
   V2 = -1 * sqrt(2) * (V1 + 6)  - 6

==========================================
Solution set B

V2 = +1 * sqrt(  4 * V1^2  )
or
V2 = -1 * sqrt(  4 * V1^2  )

Ohanian 04:27, 4 June 2006 (UTC)

Thanks Ohanian, now I see what you mean. That's a complicated method, one I would never think of. Considering my level (grade 11 AP) there would probably be a simpler method (at least I hope). Otherwise, I'll definitely fail lol. Thanks again for devoting your time!!! Very much appreciated!!! C-c-c-c 04:45, 4 June 2006 (UTC)

Don't feel too bad that you are unable to solve this problem on your first few atttempts. When I was at your age, I was even dumber than you are right now. What I have nowadays is the benefit of hard earned experiences, so I had several tricks whic I could try to solve the problem. Ohanian 07:45, 4 June 2006 (UTC)

Here's a simpler approach. Suppose the cars initially have velocities V1 and V2, where V1 is the velocity of the heavier car. KE is proportional to MV^2. We know Car 1 is twice the mass of Car 2, so to make its KE half that of Car 2, we must have

$V2=2V1.$

Now they both speed up by 6 m/s and have equal KEs. So

$V2+6={\sqrt {2}}(V1+6).$

Substitute for V2 and solve for V1 ...

$2V1+6={\sqrt {2}}(V1+6)$

$\Rightarrow (2-{\sqrt {2}})V1=6({\sqrt {2}}-1)$

$\Rightarrow V1={\frac {6({\sqrt {2}}-1)}{2-{\sqrt {2}}}}=4.243{\mbox{ to 3 d.p.}}$Gandalf61 11:37, 4 June 2006 (UTC)

Windows

Is there an alternative, operating system, than windows, that will run excisting programs. Ernie Hatt

See Operating_system#Today — The Mac Davis] ⌇☢ ญƛ. 02:04, 4 June 2006 (UTC)

Many versions of Unix will run existing Windows programs more or less successfully using a compatibility layer called WINE.-gadfium 04:01, 4 June 2006 (UTC)

Does this mean, If I load linux operating system, I will be able run my Photoshop CS2 and like programs.-User talk:erniehatt

I'm certainly not going to give you any guarantees, but I understand from WineTools that Photoshop 7 will run under WINE. That doesn't mean that Photoshop CS2 will, or that every feature of Photoshop 7 will work as expected. You should install a 32-bit version of Linux for maximum compatibility. You should try using a search engine for your application and WINE, such as this, which indicates that CS2 isn't supported yet. You should also be aware that there are commercial for-cost variants of WINE that support additional programs, such as Crossover Office. It may be that the core WINE distribution has caught up to Crossover, since they both claim to support Photoshop 7.-gadfium 09:00, 4 June 2006 (UTC)

Don't think just about tools like WINE. Anything that supports virtualization, like VMware or Virtual PC can be used to run Windows potentially within a non-Windows operating system. Dysprosia 09:54, 4 June 2006 (UTC)

Not to mention, if you don't need every single unique feature of a program, that there may well be an open source alternative able to run natively in Linux - eg. instead of Microsoft Office, consider OpenOffice. Instead of trying to run Photoshop, see if Gimp has the functionality you need. Confusing Manifestation 10:49, 4 June 2006 (UTC)

Thanks to all for the enlightment. I have been looking around some of the site mentioned, and have found that CS2 has been installed and working. My problem now is, where can I get hold of a suitable linux operating system, I am a biginner at this, and have become quite lost at some of jargon and different versions around. Will linux work with sata type drives.-User talk:erniehatt 01:44 5 June 2006

Probably the safest version of Linux to run is the same one that someone else has already confirms works well with Photoshop CS2. However, probably any recent version will run Windows programs equally well. I personally use Kubuntu and it and its counterpart Ubuntu have just had a new release which are getting good reviews. The difference between the two is the look-and-feel of the windowing system, which may not concern you. Just make sure you get the x86 version, not the amd64 version, as the x86 version will be more compatible with a broad range of software than the slightly faster amd64 version. You also can't go too far wrong with Fedora Core or Suse.

And yes, Linux works fine with sata drives.

I suggest you ask questions on a Linux specific forum where people are already knowledgable about running Photoshop under Linux.

On a different note, someone above suggested you look at the GIMP as an alternative to Photoshop. You should specifically consider GIMPshop, which is a version of the GIMP which replicates Photoshop's menu structures. It runs on Windows, Mac and Linux, so you can try it out before you move to Linux. If GIMPshop does what you want it to do, then you are almost certain to be able to do what you want on Linux as GIMP is a standard part of almost all Linux distributions.-gadfium 06:43, 5 June 2006 (UTC)

Thanks gadfium for the help, I have taken your advice and ordered Kubuntu.-[[User talk:erniehatt' Ernie.

Further my question on Sata Drives, windows will not accept them as a boot drive, if I wanted to have duel boot, would Linux be able to use them.-[[User talk:erniehatt' Ernie

I'm going to move this question down to the bottom of the page, because many people won't notice it in a question that's already been answered. Look for it at #Linux and SATA drives.-gadfium 01:23, 8 June 2006 (UTC)

Diamond

I know how it crystallizes but how does that relate to valence bonding of it? (no it's not homework)Any help would be appreciated. And remember, as this question may seem ridiculously simple, as I just read above: don't bite the newbies

In diamond, carbon is in the sp3-hybridised state, see orbital hybridisation for a nice image. Each nucleus sits in the middle of a tetrahedron. Thus, it is tetravalent here as elsewhere, and each carbon atom "shares an electron" with each of its four neighbours. --vibo56 09:50, 4 June 2006 (UTC)

This brings another question - a cube is related to an octahedron in Plato's system, how can a self-dual tetraedron build cubic centered crystals ? I'd appreciate any hint. --DLL 20:18, 4 June 2006 (UTC)

I'm not sure if this answers your question, DLL, but there's a picture of the 3D structure of diamond in the carbon page. --vibo56 21:53, 4 June 2006 (UTC)

OK, the distance between the center of the tetrahedron and its summits must differ from the distance between summits linked by Valence. --DLL 22:13, 5 June 2006 (UTC)

Black holes

i've been given an physics assignemnt do do a power point presentattion on black holes. now i know it says do your homework, but im wondering what are the main things i should include, as i am a bit overwhelmed by the information im finding. thanks in advance

The prime thing to remember is that a black hole is a star that is so massive, the force of its own gravity pulling it inward is greater than the forces propping it up outward (there are two kinds, called eletron degenerency pressure and neutral degenerency pressure. These are the outward push created by sqeezing electrons and neutrons close together). Because hte force pulling it inward is greater, the star collapses into an infinitly small point.

As Einstein explained, gravity doesn't attract things, but really bends space. (Think of a star or planet in space as being roughly like a bowling ball in the center of a fluffy matress, and a photon of light as a marble rolling nearby. The bowling ball depresses the mattress in such a way as to bend the "straight" path of the marble.) A black hole bends space so much that light which passes close enough will fall straight in. Raul654 06:11, 4 June 2006 (UTC)

Where are you getting this stuff, Raul? Why do you think light will fall straight in? Surely that will violate conservation of angular momentum (unless of course the light is aimed straight in at the singularity). -lethe ^{talk +} 07:04, 4 June 2006 (UTC)

Oops. "Fall straight in" is definitely incorrect (I meant it as a figure of speech)- it would be more of an inwards spiral. Raul654 07:15, 4 June 2006 (UTC)

I see thanks for your help- any other contributions are greatly appreciated.

Mention that inside the event horizon, the radial coordinate becomes timelike, which means that your descent to the center is as inexorable as the flow of time. Mention that the tidal forces at the event horizon which elongate you radially and compress you tangentially decrease with large mass (I think it goes M^–4). Thus you can cross the event horizon without even feeling it if it's a big black hole. Mention that probably every galaxy has a supermassive black hole at its center. Mention that some people think there may be microscopic black holes, though we can't be sure what happens to them without quantum gravity. Mention that the only measurable information in a classical black hole is its mass, its charge, and its angular momentum. Mention that quantum considerations due to Hawking tell you that a black hole's entropy is proportional to its surface area (at the event horizon), and that it has a temperature as well. Mention that spinning black holes can have singularities that are rings instead of points. Mention that a black hole might connect to another spacetime via an Einstein-Rosen bridge. Mention the Chandrasekar limit which tells you how massive a star has to be in order to collapse to a black hole on its death.

Regarding Raul's comments. It's not really accurate that there are two kinds of degeneracy pressure. There's only one, and all fermions exhibit it, electrons, neutrons, and quarks. A living star is also supported by radiation pressure. I would also advise you to be careful with Raul's bowling ball analogy. -lethe ^{talk +} 06:34, 4 June 2006 (UTC)

It is probably obvious, but you did look at our article on black holes for ideas, right? Dragons flight 06:53, 4 June 2006 (UTC)

How fast can an Alligator run?

SSIA

A lot faster than you. This is an encyclopedia. See alligator for the answer. --Shantavira 07:18, 4 June 2006 (UTC)

They are capable of short bursts of speed that can exceed 30 miles per hour. If you want to outrun one, climb a tree. — The Mac Davis] ⌇☢ ญƛ. 10:35, 4 June 2006 (UTC)

Dunno if its true or not, but i recall one of the keepers at a crocodile farm in Southern Africa telling me that while they are remarkably fast runners, crocs cannot change direction well while moving. Therefore running in zig-zags is the best way to outrun a croc if you cant get up a tree. Sounds logical if you consider its body shape, so it might be the same for aligators. Rockpocket 17:58, 4 June 2006 (UTC)

There is that old story about Peter or a lousy angel giving skills to animals. Then comes man and the skill box is empty.

This is false. Man is one of the longest runner on earth. Very few quick animals run more than a few minutes. Everything in man, from neck to heel, seems to be designed for running. This is what Marathon town was devised for, and why we invented cars. --DLL 20:06, 4 June 2006 (UTC)

Whilst I am not a biologist, DLL, where did you come up with this? Just off the top of my head I can come up with several animals that are significantly better runners than homo sapiens, both in terms of speed and endurance - the horse, for one. Humans are relatively slow sprinters and have good long-distance endurance, but are not exceptional in either category when compared to other land animals... — QuantumEleven 22:48, 5 June 2006 (UTC)

Couple of black hole questions

Sorry if this is a dumb question but could someone explain to me (in layman's terms) what the inside of a black hole (beyond the event horizon) would look like to a human in a space suit?

Perhaps this is an even dumber question. Would you die when you hit the singularity in the centre? What exactly would happen to the human body upon contact?

I've read the various black hole articles on Wikipedia but I found them a bit technical and they didn't really answer my questions. Thanks. --84.71.158.231 08:20, 4 June 2006 (UTC)

In the singularity you are squeezed to zero volume. (out of existance.)User: VictorP

1. Space looks the same inside the event horizon as it does outside the event horizon. You can pass it without even noticing. 2. After you're crushed by tidal forces and completely ionized, every particle in your body approaches the singularity. What happens when the particles come to within a couple of Planck lengths of the singularity is not so clear. -lethe ^{talk +} 08:26, 4 June 2006 (UTC)

Thanks a lot. I'm guessing that being 'crushed by tidal forces and completely ionized' isn't a particularly pleasant way to die. Probably quicker than cancer though. :) --84.68.137.18 08:56, 4 June 2006 (UTC)

Well, it completely depends on the size of the black hole. For a small black hole not much bigger than our sun, it would happen very fast, so that you would die nearly instantaneously. Actually you'd probably die before you even passed the event horizon. On the other hand, falling in to a supermassive black hole, the kind where you didn't even notice the event horizon, it could take a long time, it could be very gradual. I don't know enough about physiology to tell you what exactly would happen to your body, or how long you could last with constant pressure, so I'm not sure how unpleasant it would be. If I had to take a wild guess, I would say that the first thing to go would be your breathing apparatus, so that you'd probably suffocate before you were crushed. -lethe ^{talk +} 09:10, 4 June 2006 (UTC)

1, a black hole has to be 3 times the size of the sun. 2, you are squeezed to zero volume not riped apart by tidal forces, but yes much quicker than cancer:-)user: VictorP

Tell you what though - there'd be no shortage of people willing to fly into a black hole, despite the knowledge of an almost certain death, if there was even the smallest chance that something 'interesting' might be found inside, be it the gateway to another universe, God, the meaning of life, aliens, the secret to immortality, or whatever else we humans like to dream about. Probably get some people with nothing to lose doing it simply 'because it's there and I can' too. --Kurt Shaped Box 10:14, 4 June 2006 (UTC)

Interesting! In a rotating black hole you would go to another time or universe.User: VictorP

You would die from the [lack of] elements in space—if you didn't have a suit and stuff, but even then the suit would probably be damaged enough before you could die by black hole. — The Mac Davis] ⌇☢ ญƛ. 09:26, 4 June 2006 (UTC)

If you don't have a life support system, then you certainly don't need a black hole to kill you. -lethe ^{talk +} 09:39, 4 June 2006 (UTC)

You'd be dead before getting a chance to cross the event horizon. The tidal forces would tear you to pieces, regardless of how much stuff you surround yourself with. — BRIAN0918 • 2006-06-04 19:21

Nope. See my already posted replies to know why this is not correct. -lethe ^{talk +} 20:04, 4 June 2006 (UTC)

Curing Snoring and Apnea

About 35 years ago I devised a method to cure myself of loud nightly snoring and moderate apnea-type breathing. The cure took less than a week, and I have not reverted since. Only one other person has - to my knowledge - tried the system and found that it worked. At its simplest, the method requires no equipment, only the willingness of another person to monitor the first hour or so of the miscreant's sleep.

I would like to donate this method to the public, and wonder if it appropriate for inclusion somewhere in Wikipedia? If not, any suggested methods of spreading the word would be welcome. I am willing to provide an internet address for inquirers to get full details of the method free of cost or obligation.

If only you and one other person has tried it, then it is not a sufficiently well documented method to go on Wikipedia. See our policy at Original research. I suggest you get your own website to put your method up on, and if other people find it useful then maybe people will link to it from lots of websites and you'll get a high Google ranking.-gadfium 09:16, 4 June 2006 (UTC)

That's a good suggestion. Also, check the net for bulletin boards and newsgroups for apnea sufferers, join, and post your cure there.--Anchoress 09:25, 4 June 2006 (UTC)

I actually suffer from rather severe sleep apnea and use a CPAP to breathe properly while sleeping. I'm curious about your "method", but you haven't so much as signed your post, so there's no way contacting you to even inquire about what you're talking about. Post a note on my userpage, hopefully with an email, describing what you're talking about, and if it makes any sense at all, I'll surely get back to you. Loomis51 02:10, 8 June 2006 (UTC)

training a shark to be a vegetarian

If i brought home a baby man-eating shark and trained it to eat only veggies and one day i throw in a piece of meat will it eat the meat or avoid it?

thanks

This has been tried with many carnivorous animals owned by crazy environmentalists that want to save the animal, and is at the same time a vegetarian, and it always fails. These animals simply cannot eat vegetation, because they can't get any nutrients out of it. Lions and tigers for instance, vomit excessively, go blind, its hair will lose color and fall out, then die of starvation if you feed them no meat. — The Mac Davis] ⌇☢ ญƛ. 09:22, 4 June 2006 (UTC)

How would you "train" it to eat vegetables? If it's a "man-eating" shark, then presumably it only eats humans, which would mean that it needs the nutrients in human bodies in order to survive. Most strict carnivores do not consider vegetables to be food, and thus won't eat them no matter how hard you "train" them. Cats, for instance, need a certain amino acid which is mostly found in animal tissues in order to live, so if you want your cat to be vegetarian, you must add this nutrient to its food with an eyedropper from a bottle. The food has to look and smell like meat in order for the cat to eat it in the first place. Likewise, strict herbivores do not like to eat meat, and need the nutrients in plants in order to survive.

In answer to your question, the shark would ravenously devour the meat, and then leap out of the tank to eat you as well.

There is no such thing as a shark which only eats humans. TheMadBaron 11:02, 4 June 2006 (UTC)

Keeping sharks can actually be quite difficult for aquarists. Even training them to eat in captivity at all is sometimes a challenge. I remember one whitetip reef shark that suddently went off her feed, then refused to eat anything except salmon fillets for a whole month. The most notorious "man-eating" shark is the Great white shark, which has only recently been kept successfully in captivity. Sharks are obligate carnivores, and I cannot conceive that you would be able to convince one to eat vegetables (although a high-protein vegetable-based gel diet might be doable for some individuals of some species). If you did feed a shark nothing but vegetables, it would die of malnutrition.

However, if you trained a shark to eat only one kind of seafood, it may or may or may not later be willing to eat other kinds of seafood. It depends largely on the individual; some are pickier than others, and in some the pickiness diminishes with hunger. --Ginkgo100 19:31, 4 June 2006 (UTC)

This reminds me of a post I saw on a bird-keeping forum a couple of years ago - a real 'where do they find these idiots?' moment, it was. The person insisted that as he was a vegan, his pet owl should also be on a strict vegan diet. He posted to the forum, asking why his pet was getting sick and was constantly listless on such a 'healthy' diet! The mind boggles. --Kurt Shaped Box 19:52, 4 June 2006 (UTC)

Simpons' quote: I'm so hungry, I could eat at Arby's! Isopropyl 20:52, 4 June 2006 (UTC)

Considering Half Life 2's headcrabs...

Just sitting around and idly considering the scientific feasibility of these critters. Hypothetically speaking (and setting aside 'it's just a computer game' concerns), wouldn't it be almost infinitely improbable that a species that evolved on another planet to parasitize hosts from its own biosphere (and which presumably is also a very specialized parasite) would also be able to successfully parasitize an alien species (humans) which it had previously had no contact with whatsoever, to the extent that it can even take complete control of the host's nervous system without killing it?

Are there actually any parasitic organisms in reality that are able to 'take control of' a higher vertebrate in this manner, as a matter of interest?

--84.68.137.18 09:13, 4 June 2006 (UTC)

Most of them, tapeworm for instance? Parasites features a small list in which almost all do it that way. — The Mac Davis] ⌇☢ ญƛ. 09:23, 4 June 2006 (UTC)

Oh wait, you mean take full control. The parasite would have to be significantly more intelligent than the host. Not likely with the headcrab, or anytime soon on Earth. — The Mac Davis] ⌇☢ ญƛ. 09:31, 4 June 2006 (UTC)

If such a species did exist on earth, then it's almost a given that humans would mercilessly hunt it down and attempt to eradicate it completely through fear and revulsion with no expense spared. I couldn't imagine many environmentalists complaining, or any 'Save the Headcrab' campaigns popping up on the internet. :)

Well, they do have save-the-sharks, save-the-tigers, save-the-polar bears... — The Mac Davis] ⌇☢ ญƛ. 10:25, 4 June 2006 (UTC)

Still, you don't see many 'Save the Mosquito', save the 'Encephalitis-bearing Tick' or 'Save the Tapeworm' websites do you? Humans, whilst having some degree of respect for their predators, tend to lack sympathy for their own parasites... --Kurt Shaped Box 19:28, 4 June 2006 (UTC)

But there is a campaign to save the human flea IIRC. People have been quite successful in eliminating this parasite, but how can one set up flea circuses without it? The human flea is larger than cat or dog fleas, and so visible when performing. Plus, biodiversity and all that. However, I don't recall them being particularly successful. Skittle 14:42, 5 June 2006 (UTC)

Regarding save the sharks, did you know ten times as many people are killed by falling coconuts. Yet I can't imagine an relative version of jaws for coconuts, or people hunting them down or people avoiding holiday destinations because of coconuts, or people refusing to go onto beachs because of them the way the refuse to scuba dive, or nets being set up to catch them, like shark nets. Just shows how pathetic and terrified the human race is when its power is questioned, even by a single animal, just because it is more adapted and able in the water than we are. Philc _T^E_C^I 21:35, 4 June 2006 (UTC)

In fact, such a creature would probably have been extinct for a couple of centuries now (it'd be consigned to history as soon as human society developed to the point of being realistically able to 'finally do something about those fucking crabs') and museums/trophy rooms the world over would be jam-packed with stuffed specimens. --Kurt Shaped Box 09:57, 4 June 2006 (UTC)

It's not vertebrates, but Emerald cockroach wasp makes for some amazing reading. It's incredibly unlikely, but it's possible that a parasite could give a human a messy lobotomy and then somehow tap into the base reflex motions or something. But an alien species attacking human brains? Really unlikely. I wouldn't put it past the Combine to genetically engineer them though... Sum0 11:05, 4 June 2006 (UTC)

Sure I can think of an example where a higher vertebrate is completely taken control of by another organism: how about domestication of horses by humans? Parasitism is all in how you define it, isn't it? alteripse 14:17, 4 June 2006 (UTC)

The horse still has a choice. It could easily throw off and kill its 'master' at any time it wished - it just chooses not to. A human with an alien crab hard-wired into his brain, or even the poor cockroach mentioned above can do nothing but obey. --Kurt Shaped Box 19:23, 4 June 2006 (UTC)

Parasitism is easy. The "simpler" functionality of the headcrab, jumping onto something and then eating it, is pretty much possible for all kinds of creatures. As for controlling it ... I'm not sure. You're right, there could be some problems there. The alien creatures' "brains" would likely be totally different than anything on Earth. Maybe they've been genetically engineered by the Combine to feast on humans? By the way, you played Episode I yet? You like Alyx's little Zombine joke? --Cyde↔Weys 17:26, 4 June 2006 (UTC)

Thinking about it another way. If the universe is infinite - doesn't that also mean that there are an infinite number of stars, an infinite number of stars with planets orbiting and an infinite number of life-bearing planets 'out there'? Even if only 0.0000001% of planets harbour life, 0.0000001% of infinity is still infinity, right? Given the above, shouldn't it be mathematically certain that somewhere a parasitic creature has evolved independently of humanity, that has never met a human, yet due to a random co-incidence, still posesses the ability to 'synch' with the human nervous system? --Kurt Shaped Box 19:23, 4 June 2006 (UTC)

I didn't know tapes could get worms :). Is it like CDs getting viruses ? --DLL 19:57, 4 June 2006 (UTC)

there is a parasite that takes over its host, I can't remember its name, though, but it doesn't take over humans, I think it's an insect that's being taken over or something... :) -Obli (Talk)^? 21:43, 4 June 2006 (UTC)

Found it! (Google cache since page was down at the moment) -Obli (Talk)^? 22:24, 4 June 2006 (UTC)

See also Emerald cockroach wasp and the bizarre Dicrocoelium dendriticum and Fasciola hepatica. Sum0 22:31, 4 June 2006 (UTC)

It depends what you believe in, but since it's likely that the parasite works using some sort of poison to influence emotional states (for example a parasite that controls it's host by using a poision that affects their ability to resist), I don't see why that poison couldn't have the same effect on other complex species, assuming their anatomy is in some way similar. Then again, most of the squealers and grunts in HL aren't very humanoid at all (I can say so because I've seen their insides splattered against the wall), so I guess there's a good chance that the same poison wouldn't have the same effect on humans.  freshofftheufoΓΛĿЌ  01:11, 5 June 2006 (UTC)

See also toxoplasma gondii and toxoplasmosis for the cat-infecting protozoa which, when inhabiting rats or mice, changes their behaviour to increase the chances of their being caught by cats. It has some subtle effects on people too.-gadfium 01:29, 5 June 2006 (UTC)

About 80% of French have it, because they like their meat kind of raw. Something like 20% in the US, and more than half for the world's population, but less than the French. — The Mac Davis] ⌇☢ ญƛ. 02:32, 5 June 2006 (UTC)

Biology

why is it that unborn babies donot contract HIV/AIDS from infected mothers,safe for delivery period,when their chances of contracting HIV/AIDS is high.

they do why do you think 30% of zimbabwe has HIV

AIDS#Mother_to_Child_Transmission_.28MTCT.29 says that in utero transmission can occur from the last weeks of pregnancy. I would believe that the HIV virus cannot live in the amniotic fluid, and it cannot pass across the placenta (the placenta is a highly effective filter). EdC 13:15, 4 June 2006 (UTC)

Thats clearly wrong, the HIV virus is the most complicated sophisticaqted virus know to man.

...you would know... how? Vitriol 19:23, 4 June 2006 (UTC)

As for the second question, ask to yourself. A virus that propagates mostly via sex : men with multiple partenaries disseminate the virus, it seems that it is a custom widely ... (citation needed) in Africa. A disease that is not much taken into account by public health services : the cure is not cheap, there is a lack of money, lack of acknowledging the fact that there is a disease : plenty of poor countries are in that case. Those are factors that you encounter less in rich countries.

Rich countries give help but they sometimes ask for conditions like, giving information to people to lead them to refrain from sex. Good idea, easy to follow when you have almost nothing excepted sex. --DLL 19:53, 4 June 2006 (UTC)

Help from other countries often takes the form of educational aid, which is the pamphletting that you describe. Some countries prefer to send medical supplies, others preventative measures such as condoms. Yet another approach is the "faith-based" or abstinence program. Isopropyl 21:13, 4 June 2006 (UTC)

This is a simplification: It seems that up to 38 weeks' gestation there is less risk of the HIV getting from the mother's blood to the baby across the filter of the placenta. During labour the baby is exposed to the mother's blood, and thus to the virus. The best is probably treatment of the mother from 28 weeks on, and then there is a choice of doing a caesarian section delivery. Just a single dose of anti-retroviral, plus a caesarian section before 38 weeks can reduce the babies' infection at birth to less than 2 %. Remember the very important factor of breast feeding, which causes a significant increase of infections with HIV - so bottle feeding is best for babies of mothers with HIV infection. The 30% figure in Zimbabwe includes infections after delivery, those before labour are in the order of 10%. --Seejyb 22:19, 4 June 2006 (UTC)

I'd heard the jury wasn't out on breastfeeding? Although it increases exposure to the virus, it also provides immune protection, so in certain circumstances it might still be better to continue breastfeeding. These circumstances would not arise in a developed country. The very worst was mixing breast and bottle, giving a higher risk of infection than either alone. But research may have found new stuff since I did my A-levels. Skittle 09:48, 5 June 2006 (UTC)

what is the RFM of RFM

I WAS WONDERIING WHETHER U CUD TELL US WAT THE RFM OF RFM?

try RFM -Quasipalm 15:05, 4 June 2006 (UTC)

It can also refer to relative formula mass, which wasnt on the article, so I added it now. Philc _T^E_C^I 21:28, 4 June 2006 (UTC)

Typewriter font

What is the font of a typewriter that can be used on a word processing package, preferably on MS Word. Is it available for download? Thanks, Kilo-Lima|^(talk) 16:22, 4 June 2006 (UTC)

Yeh i have made one called TW sans

Hope this has helped

B Gates

Erm. Try Courier, Courier New and Courier PS in MS Word, should come as default on MS Word 03. A quick look through the drop down list would have saved you time. Anand 17:22, 4 June 2006 (UTC)

There's always Category:Monospace typefaces, although it's small. See also Lucida and Bitstream Vera. Melchoir 19:03, 4 June 2006 (UTC)

I have one on my PC called "Secret Service Typewriter": don't know if it comes with Word or whether I picked it up somewhere else. Sum0 22:25, 4 June 2006 (UTC)

Lawnmowers and pollution

How much pollution does a typical lawnmower release compared to a typical automobile per fuel mass? I.e., when a car and a lawnmower both burn one liter of petrol, which releases more pollutants? I'm guessing the lawnmower does because it has a less efficient cleanup system in it (and no catalytic converter even), but I don't know by how much. Thanks. --Cyde↔Weys 17:24, 4 June 2006 (UTC)

Check out Two-stroke cycle#Compared with four-stroke engines. This mentions that they are much smellier and can't meet emissions standards for cars, but it doesn't mention a ratio. I think I've heard numbers around six or so for "how much worse a lawnmower is than a car" but I don't know how accurate that is and I doubt it's per fuel mass. I think the major problem is the burning oil; I imagine it would release much more particulate matter and Nitrogen oxide. I think the two-stroke cycle article could use a pollutants section. moink 21:04, 4 June 2006 (UTC)

This article also seems right on point. moink 21:43, 4 June 2006 (UTC)

But also bear in mind how much less fuel is burned in lawn mowers than cars. This means that cars make far much more pollution total. StuRat 02:17, 5 June 2006 (UTC)

You'd think, but this is not actually true. A lawnmower is so much less efficient that they actually pollute more. From the external link above: "Testing found that operating a typical gasoline mower with a four-cycle engine produced as much PAH as driving a modern car about 150 km or about 95 miles. (Note 1). This means that unless you drive more than 95 mph, your mower actually produces more pollution per hour than your car! Another source claims that operating a gas mower for one hour will produce the same pollution as driving a car 1300 miles. (Note 4) Yet another source claims the figure is about 3400 miles of car travel per hour of mower use. (Note 5)" moink 06:25, 5 June 2006 (UTC)

I don't buy it. First, the fact that the numbers are all over the place, from 95 to 3400 miles, shows that at least some of the data is highly inaccurate. The high figure is also completely absurd, even if all the gasoline poured into the mower was vaporized and released into the air unburned, it still wouldn't be that bad (I notice the link provided in your source for that figure no longer exists, I suspect they pulled the page when it's absurdity was pointed out to them). The low figure sounds reasonable to me. However, people don't operate lawn mowers as often as they drive. If we say a family operates a lawn mower for an hour a week, then they would create more air pollution total by car if they drive more than 95 miles a week, which isn't all that much (14 miles a day). StuRat 22:37, 5 June 2006 (UTC)

I think the moral of the story to take away from this is that lawnmowers are very polluting. One hour of lawnmowing is equivalent to 95 miles in a car? Wow! Just measuring my commute, I drive about 100 miles in a week ... if I were to mow my lawn once a week with a gasoline-powered lawnmower the pollution contributed by my mower would be equivalent to the pollution contributed by my automobile! Luckily, I use an electric lawnmower, and the plant powering the electric grid probably produces less than one one-hundredth of the amount of pollution for an amount of electricity used in one hour of mowing. --Cyde↔Weys 22:53, 5 June 2006 (UTC)

Water distillation methods

Could someone explain the relationships between steam distillation, water distillation, hydrodistillation, subcritical water extraction, and hydrodiffusion? Are some of these subtypes of the others, or are they all different...? As I type this, only steam distillation goes to an article, and I'm only getting fragments on Google. Melchoir 18:47, 4 June 2006 (UTC)

Colloidal Paritcles

Excuse me, I was wondering if anybody could tell me the effects of colloidal particles in the human body? Please?

Too much colloidal silver can turn the skin grey/blue but apparently doesn't cause any real harm. See [1]... --Kurt Shaped Box 19:59, 4 June 2006 (UTC)

You may be looking for oncotic pressure, also called colloid osmotic pressure. Important determinant of fluid distribution in the body. --Seejyb 22:49, 4 June 2006 (UTC)

What's the effect of liquids in the human body? Same as for colloids - it depends entirely on what liquid or what colloid. Ice cream is a colloidal emulsion, and is pretty harmless. (unless ingested in large quantities over long periods of time) --BluePlatypus 01:20, 5 June 2006 (UTC)

True. Although you can get some nasty infections from contaminated ice cream, including salmonellosis, those are not really the effects of the colloid, but the bacteria in them. – b_jonas 15:53, 6 June 2006 (UTC)

Save the Candiru?

Following on from this topic [2], do you guys reckon than many people would complain if science developed a method of selectively eradicating 'man's most feared parasite' (a genetically engineered virus, for example)? Concerns about releasing a man-made virus into the environment aside, could you seriously envision people taking to the streets with placards, or posting on the internet to protest against the impending extinction of this (not partiularly cuddly or photogenic) urethraphillic menace? --Kurt Shaped Box 19:43, 4 June 2006 (UTC)

The food chain is like an amplifying signal cascade, with changes at the lower levels having larger repercussions elsewhere. What about biological diversity? Just a thought. Isopropyl 20:51, 4 June 2006 (UTC)

Some people complained when we eradicated smallpox, but not enough to stop it from happening. Candiru might be tougher though. Being a complex organism, its necessity to the ecosystem may be hard to gauge. -lethe ^{talk +} 22:45, 4 June 2006 (UTC)

As with other "most feared" things, Durex & Co seem to have the answer. And it's non-toxic, a replaceable resource. But then again, rubber is tough, what would the banks of the tourist resorts look like? --Seejyb 23:35, 4 June 2006 (UTC)

Goddam, that article makes me want to kill every one in existence. To the questioner, don't worry, there is always somebody against something. No matter how stupid they look, there is always somebody that disagrees. I am however surprised that some idiots were against erradication of smallpox. I frequently use that against people that say everything has the right to live and the killing of a chicken is just as bad as a person. — The Mac Davis] ⌇☢ ญƛ. 21:37, 5 June 2006 (UTC)

Any threat to the penis is a threat to be taken very seriously indeed. I know that if I'd lost my dick to one of those things, I'd make it my life's work to hunt down and destroy their entire species... ;) --Kurt Shaped Box 23:49, 5 June 2006 (UTC)

Collective punishment? Surely not. For all you know there could be groups of them working for a better relationship with humans, only costing half a penis, etc. Skittle 17:16, 7 June 2006 (UTC)

So far environmentalists have been "anti" genetic engineering and genetic organisms, and it's unlikely for that to change in the near future. I've never heard of environmentalists lobbying for seed banks to store GMOs, in fact quite the opposite, as seed banks will not accept GMOs even if it were legally permissable. Also few people have moral quams about the loss of virii. A more serious issue that may pop up is the erridication of mosquitoes, which kill millions year, by acting as vectors for malaria. Wiping out a species of mosquito may be possible one day in the future, and if it happened, what would be the effects?—Pengo 06:38, 6 June 2006 (UTC)

cure for cancer

Is there a cure for cancer?

Not generally, no. But see Cancer#Treatment of cancer and Category:Cancer treatments. Melchoir 19:50, 4 June 2006 (UTC)

Don't listen to the bullshit from books or other whackos. If there was a cure for cancer, we WOULD know about it. --mboverload@ 22:55, 4 June 2006 (UTC)

Some cancers can be cured, some cancers cannot be cured. We do know about it! But one treats specific cancers, not the concept of "cancer" in general, so the question is formulated on the basis of an incorrect understanding of the nature of cancer. - Nunh-huh 23:03, 4 June 2006 (UTC)

I think you should avoid using the word "cure". Some cancers can be treated, maybe even essentially cured, but there's risk of recurrence, and not-so-predictable results in individuals.  freshofftheufoΓΛĿЌ  00:52, 5 June 2006 (UTC)

Yes, I'm familiar with that old canard, but the fact is that there are plenty of cancers that can be cured, and have been cured. The word cure is avoided in discussing individual cases because it seems to be a promise, and is therefore like dangling fresh meat in front of a lawyer if something goes wrong. - Nunh-huh 01:20, 5 June 2006 (UTC)

Nope, and there probably won't ever be. Cancer isn't really a disease as much as it is a large set of diseases with a common underlying cause. Different forms of cancer can be vastly different, so it would be pretty unlikely to find a single cure which works equally well and is equally suitable for all kinds of cancer. --BluePlatypus 01:17, 5 June 2006 (UTC)

This is not necessarily true BluePlatupus. It has been discovered some cancers are caused by a virus and this virus can be dealt with. Most of the cancer 'cure' is pretty crude. The doctors load up the body with an exotic poison, not quite enough to kill the patient, but since cancer cells replicate faster than normal ones, they tend to absorb more poison, and die off. At least that is the way the pharmacy manager where I once worked explained it to me.

"Some cancers are caused by a virus and the virus can be dealt with" - right. And most cancers are not caused by a virus and cannot be dealt with in the same fashion. So obviously that's not a generic "cure for cancer". As for chemotherapy, which is what your latter description is, that's not a general "cure" either, because it by necessity has huge side effects, chemo will never be the best option for say, a benign tumor. --BluePlatypus 16:30, 5 June 2006 (UTC)

Many cancers can be cured by removing all of the cancerous sales. If all of them are removed, then the cancer is cured. The trouble is getting all of them, because if you don't they continue to spreadXM 20:14, 5 June 2006 (UTC)

I believe about 50% of cancers can be cured today with convential treatment, but I can't remember the exact number. Cancer is no longer means you will soon be dead. However there is no silver bullet for cancer. There are many types of cancer in different parts of the body, each with different properties and treatments. Screening may also pick up insignificant and non-malignant cancers which do not need treatment. —Pengo 06:30, 6 June 2006 (UTC)

Microphone

I am having trouble with my microphone. When I talk into it, no sound comes out of the speakers. I have done everything I can think of to try to get it to work, but to no avail. I plugged it in where it's supposed to go. I did a test to see if it was working and it said it was working fine- but still no volume comes out of the speakers even though the computer says it is registering on it. When I was configuring the microphone, I couldn't hear it coming out of the speakers, but the computer played what I said back fine, but when I tried to record something on the computer the whole file was blank, even though the equalizer thing said there was sound on it. I just can't figure out what is wrong, and any help would be greatly appreciated. By the way- if it matters, I'm using a Windows XP--71.98.11.5 19:54, 4 June 2006 (UTC)

Most sound cards have an option to mute the microphone. Try bringing up the volume control slider panel thingy respective to your system and see if there's a setting for microphone. Turn that up, and make sure it's not muted. Isopropyl 20:47, 4 June 2006 (UTC)

You wrote: "...but the computer played what I said back fine, but when I tried to record something on the computer the whole file was blank". This doesn't make sense to me. If the computer was able to play back a recording of your voice at a later time, then it must have been, erm, recorded. If the file was blank, then there is a software problem or a user error (forgot to save the recording?). --vibo56 22:03, 4 June 2006 (UTC)

I think he's implying that he can record his voice fine, but it won't record something off of his computer, e.g. he's holding the mic up to his speaker and trying to pirate his favourite Digitally Imported stream.  freshofftheufoΓΛĿЌ  00:49, 5 June 2006 (UTC)

Er... Assume good faith? Sum0 13:49, 5 June 2006 (UTC)

That was an example, not an assumption. There's actually nothing illegal about recording from streaming radio.  freshofftheufoΓΛĿЌ  06:35, 6 June 2006 (UTC)

In which case, your use of the word "pirate" is inappropriate here. :)

It appears that there's nothing wrong with the microphone: rather the problem lies with the software configuration. To be of further help, it would be useful to know which software is being used. TheMadBaron 03:01, 9 June 2006 (UTC)

Qubits and quantum computing

A qubit is a number that can hold 0, 1, or both 0 and 1. In that case, it can hold one of 3 distinct states (ternary), rather than 1 of 2 distinct states (binary). In that case, when we contrast this system to binary computing, why don't we call it base-3 or ternary computing rather than quantum computing? Why don't we call a qubit a base-3 digit, and why are the values it can hold {0, 1, both 0 and 1} rather than {0, 1, 2}?

Actually, "both 0 and 1" is just a meaningless phrase used by overexcited popular science writers. In reality, a qubit has infinitely many possible states between 0 and 1, although "state" is a somewhat loaded word here. Qubit probably explains it all. Melchoir 20:33, 4 June 2006 (UTC)

Oh, and Bloch sphere has a nice picture. Melchoir 20:34, 4 June 2006 (UTC)

The highly simplified version is that a qubit can effectively hold 0, 1, or any value between 0 and 1. It is theoretically continuous rather than discrete, though the number of states one can actually measure is finite (and often very small). The interactions between these continuous state variables can theoretically allow one to quickly solve problems that are incredibly hard for ordinary binary computation. Dragons flight 20:35, 4 June 2006 (UTC)

one-way capacitance?

Devices like touch-sensitive switches, touch-on-off lamps, and doorknob-touch detectors, all claim they work on the principle of body capacitance. However, how can this be, when a capacitor requires two (2) terminals for charge to flow through, and your finger only touches one (1) piece of metal? I thought for current to flow (i.e. charge the cells of your body), it has to go in a complete circuit. There are capacitive switches that have two exposed conductors side-by-side in a squiggly shape so that when you touch it, your finger makes a capacitance bridge between two (2) conductors. This actually makes sense. It is the lamps and doorknobs that you only have to touch one finger with that don't make sense.

In your second example, it isn't a capacitance switch - it is just a switch. The two squiggly ends are wires and you touch them together to close the circuit. In the touch-sensitive switch, the outside of the lamp (or other device) is repeatedly charged and discharged. The discharge should be approximately the same as the charge put in. In other words, the outside casing is a big capacitor that is charged and discharged - like a cow prod or a register in a computer. Your body is also a capacitor in that the outside of the skin can hold a charge. Ever shock someone just before you touch them? That is the the charge you stored in your body capacitor. Well, when you touch one of those lamps, your body will either absorb part of the charge of the lamp or release more charge into the lamp (depending on which is charged more at the moment). Then, the capacitance of the lamp will be added to the capacitance of your body. The end result, it takes a hell of a lot more power to charge and discharge the lamp's body and your body - so the "intelligent" circuit knows it is being touched and the lamp either turns on or off. --Kainaw ^(talk) 21:10, 4 June 2006 (UTC)

I think they use the conductance of the body, not the capacitance. The other contact is with the ground. I have a touch-controlled lamp switch, and I can turn it on or off by contacting a wire to it and grounding the other end. However, this kind of switch is rare. – b_jonas 15:45, 6 June 2006 (UTC)

The reason I say it is using capacitance, not conductance, is because it isn't conducting electricity through the body to another location. It is putting a charge on the surface of the skin and discharging it over and over very quickly. The circuit inside the lamp runs all the time. As long as the charge/discharge is just the surface of the lamp, it is fine. When you touch it, your skin affects the capacitance, which affects the rate of charge/discharge and the amount of electricity required to charge and then discharge. --Kainaw ^(talk) 16:34, 6 June 2006 (UTC)

Capacitors need not have two terminals. If an object has an excess charge, and it's surrounded with an electric field, then that object has capacitance. See most undergraduate physics books for the capacitance equation for a single metal sphere, where they assume that this sphere is surrounded by a conductive shell an infinite distance away. On the other hand, when your body touches a touch-sensitive lamp case, two capacitor plates exist. The electric field extends between your body and the Earth (or between your body and the grounded metal pipes and conduits in the walls and floor.) --Wjbeaty 05:59, 8 June 2006 (UTC)

Makes sense. Ok. – b_jonas 08:59, 8 June 2006 (UTC)