Wikipedia:Reference desk/Archives/Science/2007 May 14

From Wikipedia, the free encyclopedia

Science desk
< May 13 << Apr | May | Jun >> May 15 >
Welcome to the Wikipedia Science Reference Desk 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 on one of the current reference desk pages.


Contents


[edit] May 14

[edit] When is it first clear that a child is left or right-handed?

I was wondering when it was first obvious that a child is left or righthanded. The article on right-handed has nothing on it. Capitalistroadster 02:46, 14 May 2007 (UTC)

I don't know, but the results of this google search might be helpful: first age handedness children. Anchoress 02:50, 14 May 2007 (UTC)
When they've been writing or painting for a few months it's obvious. Before that - it's really hard to tell. SteveBaker 03:46, 14 May 2007 (UTC)
My son could throw a ball at approx 10 months old. Surely you can tell then? Sandman30s 09:49, 14 May 2007 (UTC)
My son was using both hands equally for almost all activities - until he started drawing and painting - for which he used only his right hand. If you put a crayon into his left hand, he'd pass it over to his right and then starts doodling. I don't think a ball toss is sufficiently strongly associated with laterality to show a preference at early age. But hey - we're all individuals and handedness isn't a 'pure' left/right thing. There are degrees of the strength of preference - so it's possible you could tell earlier. SteveBaker 11:32, 14 May 2007 (UTC)
Even at that age I am fairly sure he used to pass the ball over to his right hand if it was in his left. Certainly, at age 12 months he was running, picking the ball up with eaither hand, and throwing with his right. Also kicking with his right foot. Being right-handed myself, I find it very unnatural to attempt a throw with my left. I think he would have found the same even at that age. Also early activities such as building blocks or opening a container etc. - way before drawing or painting. Sandman30s 12:19, 14 May 2007 (UTC)
The child would probably experience the preference well before the parents were aware of it. The question is when is it first clear, presumably meaning "clear to the parents". One of my sons is left-handed. We first noticed it when he was around 12-15 months. My mother was quite worried that he was not quite normal, as he was the first person from either side of the family in at least 2 generations who showed a preference for the left. I had to reassure her that it's quite ok to be left-handed, and had to resist her attempts to make my wife and me make him use his right hand over his left. JackofOz 12:43, 14 May 2007 (UTC)

[edit] insect identification

I found these guys on my windowsill today: [1] [2] [3] [4]. Does anyone know what they are? Jay Gatsby(talk) 02:47, 14 May 2007 (UTC)

Unfortunately, all 4 pics appear to be out of focus. StuRat 02:58, 14 May 2007 (UTC)
It's the best I could do with my camera right now (the insects are really small). Care to take any guesses? Jay Gatsby(talk) 03:01, 14 May 2007 (UTC)
I think they may be termites. What do you guys think? Jay Gatsby(talk) 03:08, 14 May 2007 (UTC)
That's what they look like. Assuming I wasn't wearing my glasses at the time that is. If they are on your sill, you should call an extermination expert forthwith. --BenBurch 03:11, 14 May 2007 (UTC)
Thanks for your opinion. I think I can get better pictures tomorrow afternoon when there is more sun. To be continued! Jay Gatsby(talk) 03:21, 14 May 2007 (UTC)
I don't think you need more Sun, I'd guess you need to hold the camera farther away or adjust it for a closer focus. StuRat 04:24, 14 May 2007 (UTC)
If you look at this image, there's really not much room for doubt (your guys look like the workers, not the toothy soldiers). I'd call a bug man. --TotoBaggins 03:51, 14 May 2007 (UTC)
You need to see if your camera has a 'Macro' setting - that's what's needed to take photos with the lens closer than maybe a foot or so to the subject. Most halfway decent camera have a macro option. SteveBaker 11:34, 14 May 2007 (UTC)



[edit] Sigma Replication

What is Sigma Replication? —The preceding unsigned comment was added by 59.93.16.61 (talk) 04:51, 14 May 2007 (UTC).

I don't know, but a google search with "sigma replication" has a few likely looking sites. The first hit's abstract ([5]) suggests it is a "mode of bacteriophage lambda DNA replication during its lytic development in Escherichia coli cells". The introduction of that paper would be likely to have a more precise description. Aaadddaaammm 08:09, 14 May 2007 (UTC)
Were you unable to access the article? Quoting from the article:
"rolling-circle (σ) replication occurs late after infection to produce long concatemers that serve as substrates for packaging of λ DNA into phage proheads. The mechanism regulating the switch from θ to σ replication remains unknown."
Someguy1221 09:15, 14 May 2007 (UTC)

[edit] Speeding up the aging process in paper

Does anyone know how aged parchment and paper can be reproduced chemically. I make reproduction lithographs as a hobby and would love to be able to print them on subtly toned paper. I know all the coffee and tea techniques but unsurprisingly they all stink of um, coffee and tea! I thought that I heard of a technique using alum that changes the cellulose in some way? Any information would be greatly appreciated even if it is completely unverified.

Thanks - Kirk UK —The preceding unsigned comment was added by 82.153.110.133 (talk) 07:19, 14 May 2007 (UTC).

High doses of UV light and acidic humid environment? --antilivedT | C | G 07:42, 14 May 2007 (UTC)
It depends on whether you want to replicate the phenomenon or the appearance. You can buy "old-style" paper or parchment at an art-supply store. Nimur 13:32, 14 May 2007 (UTC)
I would think they would normally just use yellow dye, since most people want it to look old, but don't actually want it to be as fragile as such an old document would really be. StuRat 14:33, 14 May 2007 (UTC)
Since this is a hobby anyway, you might as well go all out and make your own paper. You can control the size of the fibers, the thickness and density (though you might find an upper limit to you ability to press the pulp using just hand clamps and weights lying around the house; the handmade paper I have seen tends to be closer to wedding stationary than onionleaf), and even the composition (bamboo and cotton are both readily shredded for pulp). Papermaking is a good place to start. Failing that, might storing the paper you have in a warm, dry, well-ventilated area for a week or two get rid of the smell? Eldereft 03:21, 15 May 2007 (UTC)

It's traditional to rub damp tea leaves on paper to make it look old.

"Wedding stationary" may explain why a lot of marriages end in divorce. If only they'd used stationery instead.  :) JackofOz 02:40, 17 May 2007 (UTC)

Agreed, who would want a stationary wedding ? Don't most people (well, most women, anyway) prefer a moving ceremony ? StuRat 05:27, 18 May 2007 (UTC)
heh, oops. Shows what I get for relying on Firefox's inline spellchecker instead of actually reading. :) Eldereft 03:36, 17 May 2007 (UTC)

[edit] Atlantis

What is your opinion on the existence of Atlantis? Do you think a super continent existed in which Atlantis resided? Do you think that the Altantians had a hand in the Eqyptian Dynasty? --Juliet 13:53, 14 May 2007 (UTC)

Since this question calls for opinion, I've answered here: [6]. StuRat 14:27, 14 May 2007 (UTC)
No, Atlantis could not have had it's own continent or supercontinent. If it existed around the time that is normally said it had existed. That's not an opinion. [Mac Δαvιs] ❖ 19:05, 14 May 2007 (UTC)
As far as I know, Atlantis does exist, and resides in North America except when it's in orbit. Nimur 01:45, 15 May 2007 (UTC)

which egyptian dynasty? They've had at least 30.

you don't wan't to go to atlantis, they're all just pompous, *****ing, self obsessed ***s :] HS7 16:28, 16 May 2007 (UTC)

And no it doesn't exist, they would have found it overwize :( HS7 16:34, 16 May 2007 (UTC)

I've heard of being "too smart for your own good", but can one be over wize ? StuRat 23:39, 16 May 2007 (UTC)
HS7, are you a reincarnation of Charles H. Duell? JackofOz 02:38, 17 May 2007 (UTC)

[edit] Glass

Hi my chemistry teacher has given me this question "Why is glass described as a supercooled giant covalent liquid?" and I can not find any explanations or information on Google, can anyone help me out?

The glass (window glass) is a silicate of potassium and sodium. If it cools down and finds its way to the termodynamical best point it would form crystals. But molten and cooled to room temperature (supercooled) the crystalization is not possible any more. Liquid is false, because the viscosity of glass is really high, even in centuries the glass windows do not get thicker at the bottom (even if many people tell this story). So its more a supercooled amorphous solid.--Stone 14:12, 14 May 2007 (UTC)
Read the Pitch drop experiment for insight to a similar material! Nimur 15:07, 14 May 2007 (UTC)
To augment Stone's answer, you may be interested in reading our article on glass as a liquid. — Lomn 18:12, 14 May 2007 (UTC)

[edit] Apparent Mass vs. Invariant Mass

I have been reading several Wikipedia pages involving the effects of relativity. Now, I have read that as your velocity increases, your mass increases. After some more reading, I found that this was misleading; the object's mass stays the same from it's viewpoint, but it's mass as viewed by other observers (called relativistic mass) increases. But, we know for a fact that the number of atoms inside that speeding object has not increased.

My question: how do both reference frames (the speeding object and the observer at rest viewing that object) observe/interpret this increase in apparent mass? And what are the consequences for this increase in apparent mass?

Thanks in advance. =) —The preceding unsigned comment was added by 129.115.251.49 (talk) 16:57, 14 May 2007 (UTC).

A primary consequence of the relativistic mass is the change in inertia, apparent to outside reference frames. As you know from Newtonian mechanics, F=dp/dt, that is, the force applied to an object is proportional to the time derivative of momentum, However, here momentum is not merely mass times velocity, but is magnified by gamma (1/(1+(v/c)^2)^.5) (I need to figure out the math functions on here). And so a very strong force applied to an object that is passing you at relativistic speeds will appear to deflect its trajectory much less than you would expect using Newtonian mechanics. The observer on the fast moving object sees its trajectory altered by the normal classical calculations, but his reference frame is experiencing time at a much slower rate. For this reason, the observations don't conflict, you see the trajectory altered very slightly, and he sees the same alteration at such an accelerated rate that it appears normal (classical). I hope that made sense. Someguy1221 17:40, 14 May 2007 (UTC)
If I'm reading this right, I think you're confusion comes from assuming something along the lines of mass just meaning how many atoms are inside something. Sorry if I'm reading this wrong. Atoms have mass, and different atoms have different masses. The masses that we use for atoms, in everyday physics and chemistry, are their masses when they are stationary relative to us. When an object's velocity increases relative to us, its mass also increases relative to us. This means the atoms gain mass, not that there are extra atoms. Skittle 18:03, 14 May 2007 (UTC)


Yes, I was aware that the number of atoms remains the same but the mass per atom increases; I guess what I'm asking is that, if the observer views that the moving object has gained mass, wouldn't the observer also see that that object now exerts more gravity on the matter around it? But, on the other hand, from the point of view of the moving object, how would you explain the increased in gravitational effects you experience as your velocity increases, despite the fact that your mass has not increased from your point of view?

Sorry if I'm bad at phrasing questions...but I appreciate the responses so far! =) N3rday 18:37, 14 May 2007 (UTC)

Consider testing the gravity of a moving point particle by placing a (vanishingly small) test mass adjacent to its line of travel, so close that the gravitational force is non-negligible only for the moment of closest approach. We can then, accounting for how slowly the attracting mass was moving (thus how long the "moment" was), derive its inertia by noting the velocity of the test mass after the encounter. The same attractor at different speeds will give different resulting velocities, but an observer on the attractor will claim that the velocities are all the same and we are merely measuring them with varyingly slow clocks! Dealing with kinematics in special relativity is always difficult because the very definitions of such basic quantities as velocity contain variables (that is, time and length) that depend on who measures them. I believe this improves somewhat on Someguy1221's discussion of the non-gravitational case: it's not that anyone's observations of some objective reality are accelerated but rather that there is no objective reality and anyone's observations can be explained by someone else as resulting from "measurement errors".
Also, note that, say, a magically-powerful rocket has less inertia at 0.9c than it did at rest, because it has left so much fuel behind. So to really see this effect you'd have to constantly supply new mass to the rocket, at which point it's not so mysterious that the resulting mass-energy (in either form) has more inertia. Does that help? --Tardis 20:30, 14 May 2007 (UTC)

Yes, actually, that does help quite a bit. On a similar subject, do you know of any good literature to familiarize myself with relativity? It seems like I should just read up on it and gain knowledge to answer my own questions rather than crowding the Reference section of Wikipedia...thanks for helping a physics newbie understand. N3rday 04:25, 15 May 2007 (UTC)

I read a book The Meaning of Relativity by an "A. Einstein" who seemed to know what he was talking about. It was published by Princeton. There are of course many many other books on the subject; if you like that author, he also wrote Relativity: The Special and General Theory with a more technical bent, which is available at Wikisource. Re: thanks: you're welcome! --Tardis 16:04, 16 May 2007 (UTC)

[edit] Orchids

I bought two orchids two years ago and they had beautiful flowers on them. Eventually the flowers fell off but never came back. The plant is still alive but how do I make them flower again? --Juliet 18:17, 14 May 2007 (UTC)

That seems to be a very common experience with orchids. Unfortunately, there is no real easy answer. There are an incredible variety of orchids, and they each may need different conditions in which to reliably bloom. From my own experience, I recommend these things, which have worked fairly well for me:
-Water consistently, never letting them dry out
-Experiment with different lighting conditions - keep them in one place for a month or two to see if anything happens before trying another spot
-Use fertilizer that is specific for orchids, often called simply "orchid food"
-Transplant to a larger container if the roots seem crowded and/or tangled
Even when you put the orchid in its ideal conditions, it may take months for it to start to bloom. It will slowly grow a new stalk for the flowers. But once it gets blooms, they generally last a long time. With orchids, patience is key. Hope this helps, at least a little. --Ed (Edgar181) 18:48, 14 May 2007 (UTC)
A google search for "making orchids flower" found some causes listed here including: Not enough light, poor soil, not enough temperature fluctuation, poor water. See the referenced site for more details. The one thing not mentioned above is the need for about 7 - 10 degrees F ( 4-6 celsius) change in temperature between night and day.Good Luck! --Czmtzc 18:50, 14 May 2007 (UTC)
Juliet, could you please say what kind of orchid are you asking about? I'm afraid there's too little information in your question as it is. Some orchids need winter rest, some don't. Some orchids need bright light to flower, some don't. Some are more tolerant to "bad" water than the others. Some are more sensitive to air quality (humidity, stove gas, air motion) than others. Each orchid has its preferred temperature range. So, could you please specify what kind of orchid is it? Cheers, Dr_Dima.

Just be patient, flowers don't always bloom every year. Vranak

[edit] The Celestine Prophesy

The Celestine Prophesy

Is the idea of Synchronicity and the Insights described in the novel The Celestine Prophesy can happen or is there just way too much anger, hate, fear in the world for this to happen? --Juliet 19:45, 14 May 2007 (UTC)

The idea of synchronicity is that an apparent "coincidence" has some deeper meaning, and is not just a coincidence. These occurrences would take place regardless of there being anger, hate, and fear. The insights of The Celestine Prophecy, however, will almost certainly never occur, because it is spiritualistic mumbo jumbo. − Twas Now ( talk • contribs • e-mail ) 21:05, 14 May 2007 (UTC)

[edit] Sleeping Face-up

Why do I find it hard to sleep facing up (also known as supine position)?

The only conscious idea I can come up with is that I feel vulnerable.

Maybe fearing someone will hit me in the face, neck, organs/stomach, and genitals?

Is there another, deeper reason why it may be hard for me?

And how common is it that people find it uncomfortable to sleep in the position? PitchBlack 20:28, 14 May 2007 (UTC)

There can be lots of reasons. It could be tied to you being born at a time when parents were recommended to lie their babies on their fronts to sleep, since that was thought to reduce the risk of cot death. Since this was later found to increase the risk, the advice was reversed, however I know many people in that age group who prefer to sleep in a more 'face-down'y kind of way, while people I know who were laid on their backs as babies tend to prefer sleeping in a more 'face-up'y sort of way. But this is OR :-) On top of this, curling up is a protective position, so if it is sleeping straight, compared to sleeping curled up, that you find hard, vulnerability could be a factor. Skittle 21:10, 14 May 2007 (UTC)

Do you have allergies? Sleeping on one's back can be very uncomfortable during allergy season because of post-nasal drip. Sorry to be gross. --Trovatore 21:25, 14 May 2007 (UTC)

Your weight and the way it's distributed in your body, the type of mattress and pillow, and whether you have trouble with your back, neck, stomach, etc., can all influence which sleeping positions are comfortable. Also if the room is not completely dark, you may want to sleep facing away from the light source. It is possible that there are medical or psychological issues, which would be beyond the scope of the reference desk. --Anonymous, May 14, 2007, 21:30 (UTC).
I've never been comfortable sleeping on my back (or front). (Is this OR? :-) ) I always curl up, on one side or the other. This is an area where different people are just different, I think. Unless you don't have any positions that are comfortable, I wouldn't worry about it a bit. —Steve Summit (talk) 23:34, 14 May 2007 (UTC)

Obstructive Sleep apnea can be more of a problem for people susceptible to it when they sleep on their backs. Edison 22:04, 14 May 2007 (UTC)

Another factor affecting direction faced while sleeping (for me at least) is that I find breathing much easier when facing the room and the window than with my mouth facing the nearby walls. I have trouble sleeping straight, since most beds are slightly shorter than I am. But that's enough OR. Algebraist 00:11, 15 May 2007 (UTC)

[edit] Extreme p[H]s

Hi everyone - I was reading the superacid and superbase articles earlier in the week, which got me thinking: what is the highest pH measured thus far (and the lowest)? I appreciate that a lot of superacids may not be able to be accurately measured on the pH scale, so a rough approximation would do :) Thanks, Martinp23 21:38, 14 May 2007 (UTC)

Negative pH exists, see also this faq. this article tells us that magic acid has a pH of –25 (now added to superacid article). DMacks 22:59, 14 May 2007 (UTC)

[edit] Need help with definition: Atherosclerosis or arteriosclerosis?

Arteriosclerosis redirects to Atherosclerosis, but the article says that atherosclerosis is a specialised form of arteriosclerosis.

I'm trying to write a 'for dummies' definition of arteriosclerosis, but the article isn't helping. It keeps jumping back and forth between artho and arterio, and my head's starting to spin. Help please? Is arterio the main disease? Are they really that different? Anchoress 22:45, 14 May 2007 (UTC)

They are generally used essentially as synonyms, though there is a subtle shade of difference. Arteriosclerosis emphasises the hardening and thickening of the arterial walls, with accompanying loss of elasticity; atherosclerosis emphasizes the atheromatous (fatty) deposits that (usually) accompany the disease. - Nunh-huh 23:26, 14 May 2007 (UTC)
The arter form shall tell more to most people who already know about arteries. The ather one, otoh, is slightly more encyclopaedical. What should we have here in WP ? -- DLL .. T 18:55, 15 May 2007 (UTC)
Thanks very much Nunh-huh, for the clarification. Anchoress 18:28, 16 May 2007 (UTC)

[edit] Drugs that affect long-term memories

Hi my name is John and I have a hard time to answer one of the question of my homework.

- A drug can prevent long term storage of memories is ?

First of all I thaught about the kind drug like GHB or Rohypnol but I think that's more like a type of drug. Can somenone could help me out please ??

J.

Surely the textbook for your class contains the answer? --TotoBaggins 23:49, 14 May 2007 (UTC)
Hmmm. I would have thought that there's one extremely well-known drug whose ability to interfere with memory is notorious... --Robert Merkel 23:51, 14 May 2007 (UTC)
Me too, but I can't remember it since I started taking the Ambien. But more seriously, I'm not certain this is the answer, as it's most noted for short-term memory loss. - Nunh-huh 23:59, 14 May 2007 (UTC)
John, it's hard to say without knowing what you have been studying, because there are so many possible answers to the fill-in question. There are many drugs which interfere with memory formation, but it sounds like the question is asking for one which specifically interferes with short-term to long-term memory transfer (the "consolidation" phase of long-term memory formation), rather than by interfering with attention, or short-term memory formation, or memory retrieval. The benzodiazapines are one type of drug which does this, but there are others as well, so it's hard to say (unless you've just finished a chapter on benzodiazapines.....) - Nunh-huh 23:59, 14 May 2007 (UTC)