Wikipedia:Reference desk/Archives/Science/2008 November 1

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November 1[edit]

Do chimpanzees and apes have menstrual periods?[edit]

I'm wondering if chimpanzees and apes/gorillas have menstrual periods like humans, or if they have an egg already ready and waiting, and if that is the case, do the females go into "heat" like cats and dogs?Cindycat (talk) 00:47, 1 November 2008 (UTC)

Its a good question. We have three articles on Chimps: Chimpanzee, which covers the genus Pan in general, and the two species of chimpanzee: the Common Chimpanzee and the Bonobo or pygmy chimpanzee. Chimpanzee females of both species exhibit what is called "genital swelling", an engorgement of the vulva, which is an indication of being ready to mate. Common Chimpanzees only exhibit this during fertile periods, while the Bonobo female is pretty much in a state of constant sexual readiness, regardless of fertility. However, our articles coverage on Chimpanzee sexual physiology is lacking, and I am not much of a zoologist, so I will have to defer to a more expert person beyond that. As far as Great Apes beyond the Chimps, well, 3 genus (Chimp, Gorilla, and Orangutan), 6 species, and about a dozen or so subspecies of Great Ape, and our articles there don't expand much on this either. 02:30, 1 November 2008 (UTC)
This seems to be the best answer that the internet has to offer. Accordingly, only great apes would appear to have true menstrual flows, though many mammals have cycles where the uterine wall becomes receptive to implantation. In non-apes, that tissue is usually reabsorbed if no pregnancy occurs, with little or no overt blood loss. In a few species, blood loss is observed during ovulation (as distinct from menstruation). Dragons flight (talk) 05:27, 3 November 2008 (UTC)

When was the speed of sound broken (by man made object)[edit]

When was the speed of sound first broken by a man made object. No please do not give me the Chuck Yeager crap. (talk) 02:13, 1 November 2008 (UTC)

See whip. Dragons flight (talk) 02:19, 1 November 2008 (UTC)
When a bubble collapses - it moves at the speed of sound. Babies have blown saliva bubbles since the dawn of time. SteveBaker (talk) 03:15, 1 November 2008 (UTC)
Huh? Cite, please. Bubbles breaking don't make a sonic boom. Whips do. --Anonymous, 04:16 UTC, November 1, 2008.
Perhaps you haven't listened close enough. Ever wondered what makes a bubble 'pop'? Richard Avery (talk) 08:26, 1 November 2008 (UTC)
The escape of the slightly pressurized air inside? --Anon, 02:45 UTC, Nov. 2, 2008.
A bursting balloon can create a sonic boom according to this New Scientist article and this page. Gandalf61 (talk) 15:28, 1 November 2008 (UTC)
If the new scientist say's so then it must be true! (talk) 15:34, 1 November 2008 (UTC)
Cracking finger joints?--GreenSpigot (talk) 00:17, 2 November 2008 (UTC)
I suppose technically a finger joint is "a man made object" - but it's a bit of a stretch. SteveBaker (talk) 16:55, 2 November 2008 (UTC)
Why is Chuck Yeager crap? --Masamage 16:57, 2 November 2008 (UTC)
What did you learn when you read the sound barrier article, which even has a "History" section? I assume there's at least some non-crap in there for you. DMacks (talk) 18:40, 2 November 2008 (UTC)
I think our OP merely means that while Yeager is widely credited to be the first person to break the sound barrier - his plane was not the first man-made object to go supersonic. SteveBaker (talk) 13:22, 4 November 2008 (UTC)
And if you study the history of his flight, you'll find that the Bell X-1 was patterned after the .50BMG machine-gun bullet -- an object that was well-known to go faster than sound. --Carnildo (talk) 00:45, 5 November 2008 (UTC)


who is the most published living paleobotanist today? —Preceding unsigned comment added by (talk) 03:12, 1 November 2008 (UTC)

See Category:Paleobotanists. This list is probably far from complete, but its a start. 03:45, 1 November 2008 (UTC)
How do you measure "published"? Most pages in print? Most titles? Most copies printed? (talk) 01:33, 7 November 2008 (UTC)

PVC pipe ROV[edit]

Can anyone give me suggestions or give me tips and things to look out for? I am building a ROV with a constraint of using these materials provided to me:

  • 2 24" PVC pipes
  • 10 L-joints
  • 10 T-joints
  • 3 motor mounts

The tethered ROV will be dropped and launched in a 50x25m pool. The ROV will pick up a metallic object using an electromagnet and will drop it on a target elsewhere in the pool. --hello, i'm a member | talk to me! 04:15, 1 November 2008 (UTC)

Well - clearly you can take 4 L-joints and 4 straight bits and make a rectangle. Do that twice and you have two rectangles. You can cut each of the straight bits in two and insert the 'top bar' of a T into the middle of each side of each rectangle. Now, use four more straight bits to connect together the verticals of the T's to make a cube. Fix on your motor mounts (I have no idea how - without a picture, it's hard to know - but you have two more T's and two more L's to make more structure if you need to make that mounting go more smoothely. I presume you have a way to control the speeds of the motors - and if you only have 3 motor mounts - then you probably only have 3 motors. I would put two on two sides of the ROV - pointing backwards - and one on the bottom - pointing downwards. By driving the bottom motor forwards or backwards - you can make the ROV rise or sink - by using the other two motors together - you can go forwards or backwards - and by driving one forwards and the other backwards, you'll be able to spin on the spot. The most important thing (IMHO) is to weigh your motors, batteries, electronics and other on-board stuff to figure out how much pipe you need to make the thing only JUST float. You can measure the outside diameter of the pipe and figure out how much water it displaces and make sure that your total displacement is slightly more than the weight of the machine itself. You don't want it to float too well because if you do, the "up/down" motor won't be powerful enough to make it sink. If you don't make it float well enough - then if something fails (and it will), it won't just naturally float to the surface. You're unlikely to get this exactly right the first time - so aim to make it float a bit more strongly at first - and you can always shorten the tubes to shave off a bit of bouyancy before you finally glue the whole thing together. SteveBaker (talk) 17:19, 1 November 2008 (UTC)
Thanks. How and where should I place my electromagnet? --hello, i'm a member | talk to me! 18:35, 1 November 2008 (UTC)
Without knowing what kind of attachment point you have - or the size of the thing you're trying to pick up - it's hard to know - but you need to be sure that the object doesn't unbalance the ROV when you pick it up because you don't have enough motors in the design to correct things if it ends up being (say) pointed downwards at 45 degrees. Your bouyancy calculations have to be a compromise between being neutrally bouyant WITH the object attached and WITHOUT the object being attached. If the object is very small/light then that may not matter at all - but if it's big and heavy compared to the ROV then it'll matter a lot. Ideally - you'd like the electromagnet to be at the bottom - in the center of the craft so it won't get unbalanced - but sadly, that's also where you'd like the vertical thruster to be - and they can't both be there! Can you let the electromagnet dangle on a wire a foot or so below the craft? That would be the simplest thing - and the end of the wire could then be pretty central to the ROV without disturbing the thrust from the vertical motor. There must be other parts allowed in the design - because your list doesn't include the motors or the propellors or the means to control them - you must be allowed things like cable-ties or electrical tape - and I'm sure you can use those to hold the electromagnet - or it's wires - to the structure. The critical thing that I'm trying to impart here is the vital necessity of the thing being slightly (but only slightly) positively bouyant - and being balanced, both when stationary and when thrusting and both with and without the load it has to carry. A little positive bouyancy is good because you'll be able to easily retrieve it when (not if!) it fails during testing - yet too much positive bouyancy will prevent the thing from being able to dive when the downward-pointing thruster is activated. Since your only source of bouyancy is the tubular structure of the ROV itself, you need to calculate that stuff up-front (don't guess!) and be prepared to tweak the lengths of the tubes until it floats absolutely how you want it to. Since you have limited amounts of tube - you need to start with them being a little longer than your calculations suggest so that you can cut them down as needed (you can shorten a tube - but you can't lengthen it again!)...make small adjustments until you home in on the perfect bouyancy. Similarly, the craft will be more stable if the weight is below the center-line (ie the center of gravity is below the center of bouyancy). In order to turn, you want the two thrust motors to be as far apart as you can make them horizontally - but as close to the center of bouyancy as possible so it'll drive smoothly forwards and backwards without pitching up or down. SteveBaker (talk) 15:44, 2 November 2008 (UTC)

Mechanical Puzzle[edit]

This has been bugging me. Say we have two identical cylinders A and B, with their axes parallel and set up to spin freely. Then gear them together so that B always spins through three times the angle A does. Procure a long strip of stretchy material (rubber band or something) and attach one end to A. Wrap it around A repeatedly, keeping a bit of tension so it doesn't slip off, and when you get to the end stretch it out and attached the loose end to B. Now, spin B to wind the rubber band off of A. Once it's wrapped around B, it will be three times as stretched out as it was when it was wrapped around A. So, if you let go, will it unwind? If so, with how much force? Black Carrot (talk) 07:39, 1 November 2008 (UTC)

Yes, it'll unwind with the same force as it was wound up. Just put on wheels, a seat steering and brake and you've got yourself a green vehicle for when fuel prices go up again :) Dmcq (talk) 10:23, 1 November 2008 (UTC)
OK - I agree - it'll unwind with approximately the force you used to wind it up - minus the losses due to overcoming friction. We can't calculate the force because you didn't tell us the properties of the rubber or the frictional forces involved. But before we all get too excited, think about this: It would work better (as an energy storage device) if B span 10 times as fast as A...100 times as fast...INFINITELY FASTER. So A stays exactly still and B rotates freely. The 'A' end of the rubber is simply fixed in space and winds around B as required. Well, that's exactly what a clockwork motor does. To do get the best out of real rubber, you need to understand that the force required to stetch is gets drastically more as the rubber gets close to its breaking point. So as your device gives up its energy, it produces most of it all in a rush at the start - then kinda fizzles out. The fix for that is to make the cylinders taper so that they wind around the biggest diameter at the start - and then to progressively narrower parts of the cylinder. This makes it easier to wind the thing and to provide a nice even power output for a given input. SteveBaker (talk) 16:49, 1 November 2008 (UTC)

I'm going out on a limb here, but I'm pretty sure that doesn't make any sense. The point of this setup is that only a small section of the rubber band is being adjusted at any time, and the rest is sitting still. The friction of the band against itself and the band against the cylinders requires that. The part that is being adjusted is only stretched out a small amount, well within the tolerance of this material. It's very different from holding one of the cylinders fixed and removing the gears, and there should be no loss of speed near the end. Black Carrot (talk) 19:11, 1 November 2008 (UTC)

In my read of this, the band will just unwind itself. It appears that the band is wrapped around A just enough to hold it there. Then, it is wound around B until it is "off of A". So, it is no longer attached to A. It is just wound around B. You end up with one end touching B and most of the band wound tightly around B. There is a free end now dangling. Before you even let go of the contraption, the band should quickly unwind itself off B. -- kainaw 02:51, 2 November 2008 (UTC)

Schwarzschild Radius[edit]

How do you even get the Schwarzschild Radius from General Relativity? —Preceding unsigned comment added by Superwj5 (talkcontribs) 11:20, 1 November 2008 (UTC)

Our article on Schwarzschild radius does not seem to show this derivation directly, but there are a list of references at the bottom of that article. These may lead you to some more detailed information. Also, we have articles on Gravitational singularity, Black hole, Event horizon, and on General relativity, all of which may have bits and pieces of the answer you are looking for. 15:54, 1 November 2008 (UTC)

Well, you don't really need relativity to do that - good old Newton does just fine. The radius depends on the mass of the black hole - and a rough way to calculate it is the mass of the black hole divided by the mass of our sun multiplied by 3 (in kilometers). You can calculate it exactly: Use the mass to calculate escape velocity as a function of distance: v2=G.M/r and note that at the Schwarzschild radius, the escape velocity is the speed of light. So the radius is G.M/c2 (G is the universal gravitational constant). SteveBaker (talk) 16:27, 1 November 2008 (UTC)
You've missed out a 2. Newton's laws work even better if you get them right! ;) It's v2=2G.M/r and the Schwarzschild radius is 2GM/c2. --Tango (talk) 17:09, 1 November 2008 (UTC)
Ooops! My bad! Perhaps this explains why I haven't heard back from my superluminal probe out at GRO-J1655-40. ;-) SteveBaker (talk) 17:56, 1 November 2008 (UTC)

I believe in the articles it states that the derivation by Newton's math is technically incorrect for some reason. Mac Davis (talk) 00:25, 2 November 2008 (UTC)

Update: Ah, here's what it says: Note that although the result is correct, general relativity must be used to properly derive the Schwarzschild radius. It is only a coincidence that Newtonian physics produces the same result. Mac Davis (talk) 00:44, 2 November 2008 (UTC)
And that statement is unreferenced. Seriously, why are Newtonian physics inadequate, if they produce the same result? What kind of bullshit is that? 01:09, 2 November 2008 (UTC)
Newtonian physics is an approximation that only holds under certain circumstances. Near a black hole isn't one of those circumstances, it just happens that the correction term is zero in this case by coincidence. An example of a very similar calculation where the coincidence doesn't work is when you look at orbits around a black hole. Using the same approach we could determine that the closest you can have a stable orbit around a black hole would be where the orbital velocity is the speed of light. Orbital velocity (for an object of negligible mass in a circular orbit) is , that would give a radius of , half the Schwarzschild radius (so you could have a stable orbit within the event horizon, but couldn't escape). General relativity, however, gives a last stable orbit a 1.5 times the Schwarzschild radius (I won't do the derivation here, mainly because it would take me too long to remember it), a completely different answer. So Newtonian physics gives the right answer to one question and the wrong answer to another very similar question - that's a pretty good reason to call the correct answer a coincidence. --Tango (talk) 01:43, 2 November 2008 (UTC)

I know that the Schwarzschild radius can be derived from Newton's laws and how, but my question is how in General Relativity!!!------The Successor of Physics 14:40, 3 November 2008 (UTC)

UK digital tv switchover[edit]

I have a friend who is keen to keep her old black-and-white television through the digital switchover as the licence is so much cheaper. Of course this tv doesn't have a scart socket, but apparently all she needs is a (Freeview) set-top box with an RF output rather than (or as well as) the usual scart. The official site lists several models of box that have this, but a couple of hours of searching brings up few on-line suppliers that have any of them in their catalogue, and none of those actually have any of those models in stock. Does anyone know for sure that these boxes are actually available? Or does anyone know of a gizmo that can convert the scart signal to RF for the aerial socket on the back of the television?--Shantavira|feed me 14:05, 1 November 2008 (UTC)

One possibility is to find a VCR with a scart socket for input and an aerial socket for output.
It seems like all you need is a simple format adaptor for the jacks, these sort of gizmos are widely availible in the U.S. at Radio Shack stores, which are somewhat ubiquitous (its hard to find a strip mall built in the last 30 years withOUT a Radio Shack). Whatever the UK equivalent electronics store is will likely have sales people who may be able to match you up with the right equipment. It is likely a $5.00 adaptor will make it so that ANY digital converter box will make her TV work just fine... 15:50, 1 November 2008 (UTC)
I'm guessing you don't know what a 'SCART' socket is! (This particular HORRIBLE standard is unknown in the US - which is "A Good Thing") SteveBaker (talk) 16:29, 1 November 2008 (UTC)
Holy crap that is an awful piece of junk.
this was designed by the French
. No wonder the French designed it. How did this become industry standard? In the U.S., we have relatively simple-to-work-with AV connectors, including RCA connectors and Coaxial cable and the like. The different sorts of connectors generally interconvert with a simple adaptor. No wonder this is a problem in the U.K. Ugh... 16:55, 1 November 2008 (UTC)
Thanks, and yes, scart plugs are dreadful things. They have to be wiggled vigorously in and wiggled vigorously out. Anyway, I think the UK equivalent to Radio Shack is Maplin Electronics. I get lots of stuff there but I haven't been able to find a scart-RF converter there so I assumed they weren't possible. If anyone can show me a product code for such a thing I'd be grateful.--Shantavira|feed me 18:05, 1 November 2008 (UTC)
What's truly impressive about the gargantuan SCART plug is that they are an absolute bitch to plug in - really tough to pull out - yet somehow they manage to spontaneously fall out without any provocation whatever. SteveBaker (talk) 18:15, 1 November 2008 (UTC)
Anyone who hates SCART will read this and think "Crickey! That's just the part of the iceberg above the water". They are truly a disgusting invention, I wish we could switch over to something else. —Cyclonenim (talk · contribs · email) 18:54, 1 November 2008 (UTC)
Just a guess, but it wouldn't surprise me if you could find such units at Tesco or Asda. Also try which I found on kelkoo using "freeview rf output" and manually filtering out the expensive ones or ones with no rf output. (Oh yes - check it really is rf output and not just rf loopthru) -- SGBailey (talk) 22:47, 1 November 2008 (UTC)
Also try -- SGBailey (talk) 23:01, 1 November 2008 (UTC)
Scart isn't that bad really IMO, I find they rarely come out accidently and aren't that hard to connect and disconnect (certianly less hassle than the FIVE phono plugs two of which are often the same color that are needed for component video and audio). And it's simple for the user, one standard cable between thier TV and the peice of AV equipment and job done.
And yes you CAN get scart to RF converters (e.g. ) but they aren't cheap (partly because just like a composite to RF adaptor for the US they need active electronics. partly because they are an item that few people need since AV equipment kept the RF outputs for many years after new TVs got scart inputs) it will almost certainly be cheaper and easier to get a freeview box with RF output built in (such as one of those linked on that page the guy above mentioned).
From my U.S. perspective, the problem with SCART seems to be that its using a sledgehammer to do a Ball-peen hammer job. I mean, what is the need for a 21-pin connector for AV equipment. In the U.S., surround-sound, High def home theaters are run using 5 cables: 1 video and 4 audio channels, and RCA or RF cables work fine for these applications. Even more modern standards, like S-video use at most 9 pins for 2-way video communication. Seriously, whoever decided that was a good idea needs to be given a good stern talking to... 00:52, 2 November 2008 (UTC)
S-video isn't that great is it? It's only Y/C. SCART supports RGB while admitedly YPbPr is now becoming more popular, I presume it seemed a fine idea at the time. And none of those provide data signalling. Personally I've never used SCART other then with adapters (I've had devices with SCART output but no SCART TVs) but it seems fine to me, provided all devices have them. Definitely simpler then 3 cables for video which is needed for component/RGB in most other cases + at least 1 audio for mono direction (x2 if you want bi directional=8 cables). Incidentally my experience with adapters is similar to anon. They aren't that hard to plug in. They aren't that secure either mind you but then again, nor is svideo and at least the pins are a lot more difficult to damage (unlike svideo) Nil Einne (talk) 07:59, 2 November 2008 (UTC)
But that's half the problem - SOME SCART devices support RGB - some support component - but some don't - and a few support both standards on the same connections with switches or menu options to configure them - so when you connect two gizmo's together, you have no clue whether it'll work - and no clue what form of video they'll be exchanging if they DO work. The cables themselves often leave out conductors in an effort to make them more flexible - resulting in cables that don't work when you connect them between devices that (against all odds) would have worked had all of the necessary wires been there. Separate cables at least let you SEE what's connected to what. A 21 wire connection might just about be bearable ordinarily - but because these are analog video signals, they have to be coaxially shielded - resulting in either monsterously thick cables - or cables that invite noisy connections - or cables with missing conductors. But my main complaint is the sheer mechanical ineptitude of the design and the overall chunkiness of the thing. Try fitting a SCART plug onto the side of a sexxy slimline laptop! When I lived in the UK, I used to need to push my TV up against the wall to save space - but the scart plug itself is over an inch deep - it has a stiff strain relief behind that - which adds another inch - and the cable itself needs about a 3" arc to bend through 90 degrees - so my TV has to be SIX INCHES from the wall! Compare to my US TV which has a recessed panel with the connections on it and the thin cables and short connectors are such that the TV can go right back against the wall with no gap at all. I dare not think of the ugliness of a flat panel TV with SCART connections! SteveBaker (talk) 15:26, 2 November 2008 (UTC)
According to the SCART article, the vast majority of modern devices do support RGB. Some also support component (but since it was a later addition it's not required nor should be expected). I don't know whether talking about laptops or flat panel TVs is fair, after all, these things were invented in the 1977 (and was the first standard evidentally). It's not as if 25 pin serial or parallel connectors are fun and they are new (I think) then SCART. If you want to argue that SCART is outdated and should die, I would agree, but then I don't find that S-video + audio or three component + 2 audio x 2 (okay that isn't quite fair since RGB isn't bidirectional) for is great either. Ultimately everything is moving to digital, or should provided the studios don't go too nuts about copy protection so all of these nasty cables will die but I personally having used them all to some extent don't find either of them that great, they each have their advantages and disadvantages. I think a lot of people do find SCART a lot easier then the large multitude of cables you otherwise need despite the other issues that can arise. Perhaps alternatives would have been better but I suspect until recently definitely, the advantages were probably minimal to not make it worth such a confusing switch. Even now, it seems most don't consider it worth it [1] Nil Einne (talk) 14:38, 3 November 2008 (UTC) Nil Einne (talk) 14:19, 3 November 2008 (UTC)
Frankly, at this point, 10GHz Ethernet would be a great fact, I'd like everything to support that - my toaster, my MP3 player, my doorbell - and TV, radio, etc...everything. SteveBaker (talk) 19:19, 3 November 2008 (UTC)

Glaciation during an ice age - source of the ice?[edit]

Hi. I'm wondering, during a glacial period, where does the ice actually come from? This seems like an obvious question, but right now I have two opposing ideas, and I could not find information on Wikipedia or the Internet. When an ice age begins, is the expansion of the glaciers caused by extra snow piling over time after being evaporated from the ocean? Or, could some of the ice be frozen from the surface of the ocean, increasing ice mass near the shore and reducing sea level? Or, is it a combination of both? It seems that nowadays, glaciers retreat because of warmth and sublimation, and they grow because of extra snow deposited on it. However, for the glaciers to grow quickly, the snow would need very high evaporation rates from the ocean, but isn't that supposed to happen during warm periods, not cold ones? I know Snowball Earth was supposed to have been started when extra rain washing the carbon dioxide out of the atmosphere (could that happen in a globally-warmed world?), but Pleistocene ice ages are supposed to be started by cold weather from Milakovich cycles, not rain washing the CO2 away? If the freezing of the ocean adding to the ice pack as a negative feedback occured, does that mean the ice pack could have left some brackish water behind while it melted, buried in the deepest regions of the Great Lakes? What is the current scientific view on where the ice came from? Thanks. ~AH1(TCU) 17:05, 1 November 2008 (UTC)

Take a look at the glacier article. Definitely formed from snow under high pressure. Sea-ice is different, it is much thinner than glaciers and is saline, unlike glacial ice which produces fresh water. SpinningSpark 18:30, 1 November 2008 (UTC)
Actually, sea ice is mostly fresh too. When water freezes, the ice crystals don't have space for salt molecules, so the salt stays behind in the increasingly salty liquid phase. If freezing is fast it is possible for the salt to be trapped in the frozen ice, as pockets of brine surrounded by freshwater ice. Over time, though, if subjected to thermal cycling or pressure (say from a thick layer of ice) the brine pockets merge and eventually are expelled from the ice. The increase in salinity due to brine rejection from freezing ice is one of the driving forces behind the thermohaline circulation (see also polar ice packs for more info). -- (talk) 19:43, 1 November 2008 (UTC)

Type of ammunition ?[edit]

I found an old rifle shell (the bullet had been fired). The bottom is stamped "1907" and it appears generally identical to an 8 mm Mauser shell except for one unusual feature. Unlike an ordinary rifle shell that necks down once (where the bullet is joined to the shell), this shell necks down twice and appears to be made to be joined to a bullet 4 mm in diameter. The shell was found in an area where the French and German armies squared off during World War II, and a couple of 1930-s era 8 mm Mauser shells were nearby. Anybody know what kind of ammunition this might be ? -- (talk) 18:40, 1 November 2008 (UTC)

Is relevant. The bullet on the right appears to have 2 necks and is a "8mm mauser (7.92 x 57 mm)" -- SGBailey (talk) 22:37, 1 November 2008 (UTC)
A bit similar, but the second "neck" on the shell I have is 15 mm long. I wondered if it is some kind of a blank round but from what I can find the Germans were using crimped blank rounds, at least in World War II. —Preceding unsigned comment added by (talk) 11:02, 2 November 2008 (UTC)
This is hardly a science question - you'd do better to ask it on the Miscellaneous desk. SteveBaker (talk) 15:10, 2 November 2008 (UTC)

Hypothetical Noble Gas[edit]

My Chemistry teacher is having my class make potential elements and describe their properties. Most of the properties should be based on the typical behavior in the group we put them in-the group I've chosen is the Noble Gases. My question: how many elements would be in the currently non-existent periods 8 and up? Is it 18 or 32? I'm mainly confused over whether such periods would have a collection similar to the Lanthanides and the Actinides. (talk) 19:58, 1 November 2008 (UTC)

Maybe this extended periodic table will help: [2] --Russoc4 (talk) 20:05, 1 November 2008 (UTC)
Are you sure that table is correct? Can anyone else vouch for it? (talk) 21:44, 1 November 2008 (UTC)

It looks correct to me, see Periodic table (extended).W.i.k.i.p.e.d.i.a - Reference desk guy (talk) 22:02, 1 November 2008 (UTC)

We have an article on the periodic table and noble gases. Just go and take a look and come back with a more specific question if you need to. - Mgm|(talk) 22:22, 1 November 2008 (UTC)
There are some embedded assumptions about the filling order of f and g shells that we really have no way to test. So the placement of superactinides and the like on those extended charts may not really reflect their chemistry. Of course on the other hand, if those atoms can be created at all they are probably are so unstable that they would never have any demonstrable chemistry anyway. Dragons flight (talk) 23:20, 1 November 2008 (UTC)
On the other hand, there are some hypothesis that some huge elements (the atomic number 132 sticks in my head for some reason) may become significantly more stable than their lighter counterparts, having half-lives that may make it possible to do some real chemistry with them. However, for the purpose of this educational activity, being scrupulously correct is probably not all that important. The idea is to gain a fuller understanding for the importance behind the organization of the period table in order to predict "hypothetical" undiscovered elements, much in the way that Mendeleev used his table to predict the properties of the as-yet-undiscovered elements such as Gallium and Germanium. Sometimes, the importance of teaching this lesson requires that we fudge the real facts, especially at the high school level. See Mendeleev's predicted elements for more info on this... 00:44, 2 November 2008 (UTC)
See also, island of stability. --Tango (talk) 02:14, 2 November 2008 (UTC)
THAT'S IT! Thanks for finding that article Tango. I knew I wasn't crazy... 02:37, 2 November 2008 (UTC)
According to this article from Nature, the average velocity of the 1s electron is (Z/137)*c. This to me implies that while it may be possible to create a stable nucleus of high atomic weight, it's not possible to have an actual atom (i.e. populated electron shells) above Z=136. Also, as that point is approached, relativistic contraction of the orbital sizes (and possibly relativistic increase in mass?) would radically alter the chemistry, so assuming that properties will remain similar as you go down the column of the periodic table might not be safe. Franamax (talk) 08:14, 2 November 2008 (UTC)
I haven't read the article, but is that formula actually expected to hold for heavy atoms? Isn't it more likely that a derivation including relativity (which is easier said than done) would just result in a different formula (which reduces to that one in the non-relativistic case)? --Tango (talk) 13:42, 2 November 2008 (UTC)
Of course the formula is not expected to hold. For relativistic speeds, use relativistic physics. Use the Dirac equation instead of the Schrödinger equation and the speeds will be below c for arbitrarily large Z. Icek (talk) 15:14, 2 November 2008 (UTC)
Well gee, the paper is titled Relativistic effects in homogeneous gold catalysis, so you'd think they may have used relativistic physics, wouldn't you? The box where "Relativistic effects" is explained has "In 1928 Dirac developed a new equation..." and goes on to use that equation. The example they use is Hg, where the 1s electron is at 58% of c. I can send a copy of the paper, drop me an email. Franamax (talk) 20:50, 2 November 2008 (UTC)
Sorry - I was wrong, the Dirac equation is actually not sufficient, and one needs quantum electrodynamics in order to compute the ground state for Z > 137 (Z >= 1/α). Btw, the Nature paper is freely available here. Icek (talk) 23:01, 3 November 2008 (UTC)  := Just check the Janet periodic table and yuo'll see that the next two periods each have 50 elements ending in atomic numbers 170 and then 220 (for the nobel gasses). You also might want to check the images in Talk:Nuclear model about how to build a model of them.WFPM (talk) 18:49, 9 November 2008 (UTC)

Alright, thanks. I could also use help with finding a basic chemical property that a noble gas might have, but I know that's pushing the "We don't do your homework" policy. (talk) 18:15, 2 November 2008 (UTC)

Note: I already have one about how noble gases rarely react due to their full outermost electron shells. (talk) 18:26, 2 November 2008 (UTC)  :=Nobel gasses have the common property of having all the periods completely filled within the atomic nucleus. The next element has to be an add on involving the creation of a new period of elements. The next period will be 4 elements longer than the previous second 50 element period, and thus involve 72 additional elements. WFPM (talk) 19:03, 9 November 2008 (UTC)

Why aren't there better batteries for portable devices?[edit]

How far away are we from having really good, long-lasting batteries for our cell phones, iPods, laptops, etc? Batteries that will last through--I don't know--maybe a day, two days or a week of continuous use. Has there been any progress in this area?-- (talk) 21:41, 1 November 2008 (UTC)

I think we are quite along way form that. Recently memory as decreased in size and cost, unfortunately this is not possible for batteries. Batteries use a chemical reaction to work; trying to improve this is extremely hard.

Inductive charging allows for an electronic device to be charging with out an electronic connection - the electronic device just has to sit on the charger. This will probably be integrated into tables so your battery will be charging when you’re using you laptop or other electronic device.

Although I say it is hard to improve batteries, there have been great developments for batteries. We don't notice these improvements because we are taking more and more power from the batteries, for example a laptop 5 years ago might have had a 2 hour battery-life, now a new laptop might also have a 2 hour battery-life but now it has to run many more power-intensive programs, WiFi, bluetooth etc. W.i.k.i.p.e.d.i.a - Reference desk guy (talk) 22:00, 1 November 2008 (UTC)

See also Micropower, which covers other techniques like microturbines powered by liquid fuel to run electronic devices far longer than batteries can. Edison (talk) 00:43, 2 November 2008 (UTC)
We do keep hearing of batteries that can be formed like plastics, so the casing of the unit could also be its power supply. But these keep not appearing in commercial products, so seem to be yet another futurologists' pipedream. —Preceding unsigned comment added by DewiMorgan (talkcontribs) 02:58, 2 November 2008 (UTC)
Do you mean Lithium-ion polymer battery? They can be shaped to fit various weird shapes, although they can't yet replace the casing itself. MaxVT (talk) 17:26, 2 November 2008 (UTC)
Indeed a simple mobile phone has an excellent battery life (particularly standby), and some people prefer them. For those of us who do like (and use) a colour screen, data connection, camera, music etc of course it's not going to last that long. 1 or more days of continous use is a bit unresonable though we're not talking about Moore's law here, I don't think it's likely battery capacity doubles every 18 months Nil Einne (talk) 08:14, 2 November 2008 (UTC)
I remember reading an article within the last year or so about some new form of batter that would last years. Unfortunately, that's all I can remember. (talk) 10:39, 2 November 2008 (UTC)
I don't know about batter, but there are "batteries" lasting for years (pictures). Icek (talk) 14:26, 2 November 2008 (UTC)


Why is it that,when you have a flu, body temperature always go up during the night and you feel worse then during the day? (talk) 21:51, 1 November 2008 (UTC)

I very much doubt that's always the case. I'm not even sure it's often the case - why do you ask? What makes you think that's the case? --Tango (talk) 22:11, 1 November 2008 (UTC)
Body temperature varies during the day, in a regular pattern, both in healthy humans and in humans suffering from a viral infection. Temperature usually goes up in the afternoon, but not at night. Fever article has some information. --Dr Dima (talk) 23:16, 1 November 2008 (UTC)

Well,the reason I asked is that I have a flu and during the day I always have life 37.2 or something on those measures, but at night it usually goes up to 38.5. —Preceding unsigned comment added by (talk) 23:41, 1 November 2008 (UTC)

Are you taking paracetamol or anything similar? If so, that ought to lower your fever, in which case when you take the drugs will affect when your fever is at its worst. If you take the drugs as soon as you get up and then regularly during the day, but don't take any at night, that would probably explain what you're seeing. Of course, if the unexplained changes in body temperature persist, you should seek professional medical advice - it could be indicative of something serious (I don't know of any such things, but I haven't spent 6 years in med school, so I can't say for certain that it isn't something serious). --Tango (talk) 23:45, 1 November 2008 (UTC)

Well, it's simply not true that when you have influenza "body temperature always goes up during the night and you feel worse then during the day": that's the way you're experiencing, but when the diurnal variation of the symptoms of influenza were studied, it was found that 'the average temperature increased during this illness and ... nasal secretion and the temperature increase were greatest in the early morning'. I suppose this might be interpreted as the temperature "going up" during the night. Part of the reason for differences might be that your normal diurnal variation may be different from other peoples. But most people, apparently, have the greatest temperature and worst symptoms in the morning. [3] - Nunh-huh 01:56, 2 November 2008 (UTC)

your nervous syztem winds down the sympathetic system and fires up the parasympathetic system at night, as you go into rest mode and out of active mode. as a result, your attention is shifted to your internal stimuli, rather than external stimuli in the world. sick people tend to feel more miserable at night. Gzuckier (talk) 16:55, 3 November 2008 (UTC)

Using cat litter to defuse potency of medicines/pills[edit]

Recently, going through my now deceased great aunt's things, her daughter had to dispose of the numerous medicines she was on. (She had cancer if this helps.) She bought cat littler, and put the pills in the cat litter to remove their potency.

I'd never heard of this before. My questions: 1. Why does this work? From reading the article about what it does to the feces, I gather there's some sort of chemical reaction, but am not sure what. And, 2. Is this something that can be done with any medicine? Or just the anti-cancer stuff? Would it work on every kind of drug; could the police place illegal drugs in kitty littlr before disposing of it once it's been used as evidence? (now that I think about it, I would guess they do; they have to do something to it.)Somebody or his brother (talk) 22:30, 1 November 2008 (UTC)

Cat litter should have negligible impact on most dry, solid medications. Cat litter is sometimes recommended as a way to process liquid medications though. This has more to do with turning the liquids into an unpalatable solid than with actually breaking down the medication. Dragons flight (talk) 23:10, 1 November 2008 (UTC)
Sounds very questionable to me. Take the pills to your local pharmacy, I'm sure they'll dispose of them for you. --Tango (talk) 23:41, 1 November 2008 (UTC)
Indeed, pharmacies must have procedures on hand to dispose of expired medications; they would probably add your great aunts pills to the next batch that goes out. I would really recommend that you do that. Attempting to dispose of these on your own is dangerous, and homespun methods of "reducing their potency" seem like a bad idea as well... 00:37, 2 November 2008 (UTC)
The US Office of National Drug Control Policy recommends: "Mixing prescription drugs with an undesirable substance, such as used coffee grounds or kitty litter, and putting them in impermeable, non-descript containers, such as empty cans or sealable bags, will further ensure the drugs are not diverted." [4] I think that should be read as "such as used ... kitty litter" - the kitty litter isn't there to do anything to the drugs, it's there to make them unappealing enough to discourage junkies from snagging discarded drugs from the trash and abusing them. Slightly nutty and paranoid, sure, but that's drug control policies these days. -- (talk) 01:11, 2 November 2008 (UTC)
If memory serves, the official advice in the UK is to take all expired or unneeded drugs to a pharmacy to be disposed of. That page seems to suggest that some pharmacies in the US won't take them. The UK system seems better to me - far simpler (a list of drugs that need to be flushed down the toilet is far too confusing for anyone to actually follow it). --Tango (talk) 01:48, 2 November 2008 (UTC)
If you let people flush them down the toilet, some news idiot with a need for a story will get someone to do an analysis of the water. Then, they'll find something like 1 part per trillion of Prozac in the water and the next morning's headline will be "City Water is Full of Prescription Drugs including Prozac!" -- kainaw 02:33, 2 November 2008 (UTC)
Actually drugs flushed down toilets appears to be a genuine concern [5]. Also this version of the guidelines 128 mentioned don't say anything about junkies. They talk about pets and children. This one does however [6]. In any case, I agree with Tango. I don't know why the US doesn't just follow what's done in the UK, NZ, Australia [7] [8], and large parts of Canada [9] and get pharmacies to deal with expired drugs. (IIRC, last time this came up the consensus was few pharmcies in the US would deal with expired medication and from Googling this appears to be the case) Nil Einne (talk) 07:45, 2 November 2008 (UTC)
Just speculating, but it may have something to do with the way the DEA tracks scheduled (controlled) drugs. If they expect a "chain of custody" and a full account of all drugs received or distributed, having "stuff somebody brought in" would create discrepancies in the records. For things that don't have addict issues, it's probably set at a state level by a board of pharmacy how they keep track of things. Some references that might be interesting: [ONDCP's recommendations], [rules for a state (Oregon) board of pharmacy]. Just from the standpoint of process control, bringing the medications back into the pharmacy creates a burden of making sure that they don't get mixed up with prescriptions to be issued. Creating opportunities for medication errors is considered harmful. SDY (talk) 10:02, 2 November 2008 (UTC)
Surely a pharmcy has to keep good track of their medications anyway don't they? It's not as if they have all their medication in one big tin and choose whatever looks good (at least I hope it's not). So it seems to me it doesn't make that much more problem. After all, giving someone warfarin instead of vitamin K tablets is already serious enough. Even if you're talking about the same drugs, I presume pharmcies still often have to keep track of probably more then one quantity of the drug with different expiry dates. In other words, it may add a small risk and yes that risk may be catatrophic, but surely it's only minute unless the pharmcy already has shit systems anyway in which case you have other things to worry about. Drug control wise, sure it does add another element to deal with but are dodgy pharmcies really such a problem in the US. Here the greater concern is with people robbing pharmacies from what I can tell. Nil Einne (talk) 15:01, 3 November 2008 (UTC)
If you believe that junkie won't consume drugs because they have to weed through cat poop and piss to get them, well, you are sorely mistaken. Drug adicts often do far worse to get a "fix" and, for the kind of person who will hunt through the landfill to get drugs, a little shit and piss is not going to stop them... 02:41, 2 November 2008 (UTC)
Think the toilet scene in Trainspotting, but it may make them harder to find at the tip/dump. Next headline: Dumpster baron recycles pharmaceuticals and makes a motza! Julia Rossi (talk) 22:46, 2 November 2008 (UTC)

My local pharmacy has a sign on the wall about this. It says to remove and destroy all labels, mix liquids with kitty litter or kitchen waste, crush pills and open gelatin capsules, and mix everything together into a nasty mess that is unrecognizable. Then put it in the trash, not the toilet. (talk) 01:42, 7 November 2008 (UTC)