Wikipedia:Reference desk/Archives/Science/2008 December 26

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December 26

Ashes in the garden

What is the PH of ash from burnt wood? And what substance (that is not too toxic to put in a compost pile) has a base that can neutralize the acidity of the ashes?--Apollonius 1236 (talk) 00:54, 26 December 2008 (UTC)

I would (wood?) expect the ashes to be a base, since in frontier America they used water dripped through wood ashes to combine with rendered animal fat to make soap, like lye was later used. The material leached from wood ashes was apparently weaker than lye, since the soap tended to be soft, per The Foxfire Book (1972)edited by Eliot Wigginton [1] , [2] , [3]. Note that any substance strong enough of a base to make soap is hazardous. Here is a Purdue University source on using wood ashes in the garden if the plants need soil with less acidity: http://www.hort.purdue.edu/ext/woodash.html]. In a compost pile the decay of plant material should tend to make the material more acidic. That is one reason why farmers add lime to fields which laid fallow and had organic material decompose for years. A gardening site [4] says sulfur can be used to lower the pH if the soil is too alkaline. Edison (talk) 01:30, 26 December 2008 (UTC)

Any detrimental effect of ashes in your garden depend on the amount of ash and what you grow. Small amounts are quickly diluted by rain and even act as fertilizer (potash). I wouldn't worry too much. If you are on arid land and the salt content of the ground is an issue, that's different. 93.132.154.92 (talk) 11:44, 26 December 2008 (UTC)

As far as I know, an acid and a base form a salt and a water, making cleanup a lot easier. Baking soda is one base of pH 14, and so is kitty litter. ♫Deathgleaner 00:40, 27 December 2008 (UTC)

Source for kitty litter being a very strong alkaline? Seems dubious. Some is just derived from clay. Edison (talk) 05:03, 27 December 2008 (UTC)

Electrical Charges

My question has to do with protons and electrons. I would like to know what classifies a positive charge, as well as a negative charge.I have no idea how electricity can take on two forms. I appologize for such a 'trivial' type of question but I cannot find the answer anywhere I look. Thank you very much for your time and I hope to hear an answer shortly! —Preceding unsigned comment added by 216.54.110.130 (talk) 02:05, 26 December 2008 (UTC)

The same way that numbers can be positive or negative, a charge can take any real value, that is any number that lies on the real axis. Which includes both positive and negative values, just like a bank balance can be positive or negative. Now which is positive and which is negative is just defined by convention, and has no underlying scientific reason. Like charges repel and different one attract. —Preceding unsigned comment added by 92.3.10.246 (talk) 02:22, 26 December 2008 (UTC)

Did you by any chance look up proton or electron yet? When you have come back her if you need further explanation--GreenSpigot (talk) 02:23, 26 December 2008 (UTC)

There is an explanation of why protons are positive and electrons are negative, but this has to do with their constituent quarks, which just leads to questions on why quarks are like that, and so on. Ultimately you hit a point where you just have to accept that things are the way they are, as no further explanation is possible. StuRat (talk) 03:57, 26 December 2008 (UTC)

There is no explanation as to why positive objects are positive and negative objects are negative (not to mention that electrons have no constituent quarks) it is simply convention, and all that is important is that whichever you define as positive is the opposite sign to which ever you define as negative. The charges of quarks were defined by the accepted convention for proton charges (hence the awkward fractional charges) and not the other way round. —Preceding unsigned comment added by 92.1.240.165 (talk) 15:42, 26 December 2008 (UTC)

The order in which they're discovered is irrelevant. A proton can still be said to be positive because it contains two up quarks and one down quark. StuRat (talk) 18:47, 26 December 2008 (UTC)

In principle I agree with your statement but I feel the use of the word 'because' implies that one is defined by the other, which is not the case, all that is important in theory is that any tow statements or predictions which can be deduced from it are consistent. —Preceding unsigned comment added by 92.22.7.10 (talk) 20:18, 26 December 2008 (UTC)

For hundreds of years prior to the 1700's people studied electricity and wondered if there were two kinds of electricity, one kind created by rubbing a glass rod with a silk cloth, and another created by rubbing amber with fur. Two amber rods rubbed with fur repel each other. Two glass rods rubbed with silk repel each other. But the amber rod and the glass rod when charged this way attract each other. Benjamin Franklin in the 1700's established that lightning is also electricity, and that the two kinds of electricity are really more or less of one kind of electricity. He called the charge on amber "negative" meaning less of the one "electric fluid" and the charge on glass "positive" for more of the one substance. He knew nothing of electrons or ions. A century and a half later scientists discovered that the charge carriers are subatomic "electrons" with negative charge which can be stripped away from neutral atoms inn a glass rod to leave the rod positively charged and the silk negatively charged. Edison (talk) 16:11, 26 December 2008 (UTC)

I'm sure that they would have called the "charged particle which flows freely" (electrons) the positive charge, and protons (perhaps renamed "negtrons") would've been said to have a negative charge, if they understood what was happening better. But they didn't, and we ended up with the labels being essentially backwards. StuRat (talk) 21:07, 26 December 2008 (UTC)

The backwardsness causes confusion for beginning students of electricity, but in electrical engineering or physics they go their merry way with "conventional current" from positive to negative. If top and bottom in the Triboelectric series had been chosen oppositely, Franklin might have made a definitional choice which would have made the lives of beginning electricity students easier. See also [5]. Silk is classically associated with glass and fur with rubber, but from the table silk should make glass positive and make rubber negative. It seems very odd that "human skin" is at the top of the chart. Edison (talk) 21:27, 26 December 2008 (UTC)

When Benjamin Franklin decided to describe the "two kinds of electricity" as opposites of each other, he arbitrarily assigned the positive numbers to one kind and the negative numbers to the other. He knew that the assignment was arbitrary and that the math would work for either assignment. We have followed his convention ever since. This is similar to assigning positive longitude as east of Greenwitch, or positive angles as counterclockwise: either way will work, as long as everybody knows the convention. In retrospect, we can now say that Franklin guessed wrong and that the assignment of postiive to the electron would have made life easier. The other quantum attributes (spin, color, etc.) are equally arbitrary. -Arch dude (talk) 03:28, 27 December 2008 (UTC)

Franklin's insight was "One kind of electricity, just more or less of it" rather than "Two kinds of electricity." Edison (talk) 05:02, 27 December 2008 (UTC)

It really doesn't matter - you can either envisage electrons going around the circuit in one direction or 'holes' (places where there is an electron 'missing') travelling in the opposite direction. For static electricity, there is some vast number of protons providing positive charge and some vast and almost identical number of electrons providing negative charge. The net charge is the teeny-tiny difference between those two numbers. You can get an idea of the smallness of that disparity when you consider that Avagado's number (which is roughly the number of protons in a couple of kilograms of 'stuff') is 6x10²³ and the charge on the electron is 10^-19coulombs. So a charge of one coulomb on a largeish object might represent a disparity of only a fraction of a percent of the electrons versus protons. SteveBaker (talk) 16:12, 27 December 2008 (UTC)

'Holes' do not exist in conductors, only semi conductors, in metallic conductors the bonding is not covalent and the electrons naturally exist in an energy band which overlaps with the conduction band, and so the notion of holes where electrons are missing makes no sense. In conductors the electrons are naturally free, as metals can be thought of as positive ions held together by negative electron glue. —Preceding unsigned comment added by 92.22.7.10 (talk) 18:14, 27 December 2008 (UTC)

Fortunately, you can decide whether negative or positive charges make up the current - measure the Hall effect! Icek (talk) 12:24, 1 January 2009 (UTC)

Proactive Competitor

In Fort McMurray, there is advertised a competitor to Proactive in a commercial similar to the proactive commercials. In the commercial, it says it is cheaper than proactive and that it has delayed release benzoperoxide. What is it?96.53.149.117 (talk) 02:53, 26 December 2008 (UTC)

I think you mean benzoyl peroxide. But what is your question exactly ? StuRat (talk) 03:53, 26 December 2008 (UTC)

I think he/she wants to know the brand name of the competitive product advertised in Fort McMurrary as a competitor of Proactive that is cheaper and has delayed release. That isn't really a science question though. While perhaps someone in the RD is familiar with the ad in question, my recommendation would be just to pay more attention next time it comes on. It must mention the brand name sometime, otherwise it's a pretty useless ad Nil Einne (talk) 09:56, 26 December 2008 (UTC)

Hey, it's about chemicals which people have trouble spelling, so it sounds more like a science question than miscellaneous or humanities. A competitor for Proactiv which is advertised on TV is AcneFree, per [6] and [7]. Other competitors are mentioned at [8] Please understand that we cannot give any medical advice, including advice on effectiveness or gentleness of acne remedies, and this information is not an endorsement. You might wish to see a dermatologist. Edison (talk) 16:01, 26 December 2008 (UTC)

My understanding is the question was about the name of the brand of product advertised not the effects of benzoyl peroxide but I could be wrong. Nil Einne (talk) 07:39, 27 December 2008 (UTC)

Racing Pigeons

Racing pigeons can allegedly not see red light, so it is known for racing pigeon breeders to install red lights in the lofts with the intention that it will allow the breeder to move about at night without disturbing the pigeons, i.e. there is enough light for humans to see, but not pigeons. However, my father has installed some red strip lights in his loft and the pigeons seem perfectly capable of flying about the loft by this light. Does this show that the pigeons are sensitive to this light or are there other explanations, such as possibly that they are sensitive to UV leakage from strip lights? Is this belief that they cannot see red light well founded or is it a myth of the sport? thank you. —Preceding unsigned comment added by 92.1.240.165 (talk) 17:28, 26 December 2008 (UTC)

Most prey birds, like pigeons, lack good night vision, whereas humans have pretty good night vision, so making the lights dim should help him see without the birds seeing him. [9] discusses human versus pigeon vision, and says pigeons are diurnal (daytime) birds and have a "rod-poor retina" which would make their night vision poor, compared to owls, which have many rods in the retina and great night vision. . Different red lights can also have different spectra, and some might include shorter wavelengths the birds are more sensitive to. Edison (talk) 19:28, 26 December 2008 (UTC)

Pigeons can see red light, they're just not as sensitive to it. One paper shows the sensitivity at 640 nm is about 20% of that at 584 nm (the peak)[10]. Visible spectrum defines red as 620-750 nm, so they can perceive shorter wavelengths of red light quite well. --Maltelauridsbrigge (talk) 23:21, 26 December 2008 (UTC)

Amateur genetic engineering

Are there laws in the U.S. under consideration to limit genetic engineering experiments to labs and researchers equipped and trained to reduce the chances of something getting out and causing problems? See [http://www.cbsnews.com/stories/2008/12/25/tech/main4686710.shtml?tag=topHome;topStories "Amateurs Give Genetic Engineering A Try Hobbyists Use Homemade Or Use Equipment In Effort To Create New Life Forms]. (a truly odd title). What could possible go wrong if someone does gene splicing in the kitchen? Edison (talk) 21:47, 26 December 2008 (UTC)

Not much, I think. If you are worried about hybridization of a pit bull with a pit viper, that sort of a problem, it is very unlikely to happen even if one tries very, very hard. I know there is no limit to human stupidity; it is an experimental fact. Still, the genomes of different multicellular organisms are usually different enough for the monsters to remain in the fantasy books. If you are worried about simpler stuff, like accidentally putting a gene for a toxin A into a hitherto harmless bacterium B, the chance for a disaster is still very low, for two reasons. The first one is, horizontal gene transfer happens all the time without any help from a gene-splicing amateur. If it could readily happen (as with E. coli and shiga toxin), it would have or will eventually happen, whether you want it or not. The second one is, an amateur, hopefully, does not have access to the kind of genetic material one should really be worried about. In that respect it is the professionals that should make you nervous... All that is, however, purely hypothetical. Really, I don't mind at all seeing GFP being put to good use, as in the artcle you linked to. And if the researcher turns green as well, because "there's no safety process in place", there isn't much harm in that ;). Or let me put this another way. Experimentalists very often do not know what they are really playing with; that is how the science advances. It does not matter whether the research is done at home or in the lab. It is my firm belief that any advance, or any result at all, eventually benefits the humanity rather than harms it. Hope this helps. --Dr Dima (talk) 03:02, 27 December 2008 (UTC)

There are no laws that I know of that require licensing in order to perform genetic engineering. You would need a licensing regime in place before you could start to talk about limiting. By contrast, there are licensing restrictions in place for radioactive materials, certain dangerous chemicals, and for dangerous microbes and viruses. But "genetic engineering" is a pretty big category, and the state of the art is not yet such that the possibility of an at-home setup producing something truly dangerous is feasible. But someday this will no doubt become the case. --98.217.8.46 (talk) 03:30, 27 December 2008 (UTC)

I have no good answer but have a related question... according to Dr Dima you would need dangerous material available and 98.217.8.46 stuff like dangerous microbes are illegal. Is there not some sort of machine that can add genes one at a time? What exactly is genetic engineering in engineering terms? ~ R.T.G 12:11, 28 December 2008 (UTC)