Wikipedia:Reference desk/Archives/Science/2012 November 10

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.

November 10

where do new layers of earth come from

hello, one sometimes reads that paleontologists found some fossils so and so many meters deep, or archaeologists excavated some city or something, I wonder where has the earth that buried historical artifacts underneath it, come from? Do the upper strata just get reshuffled so that that which was down goes up and vice versa (we have been naught... lol), or are these cosmic matter (in which case that would mean that the earth becomes bigger, wouldn't it?) Thanks in advance Asmrulz (talk) 13:10, 10 November 2012 (UTC)

A number of factors contribute. The action of plants and animals builds up a layer of soil. In many cases rain and wind driven erosion moves sand from one place to another. Over time, in the absence of geologic activity, mountains tend to get lower in height and low level areas tend to get higher. A recent article in Scientific American magazine decribed how wind lifts sand off the Sahara into the upper atmosphere and transports it to overseas countries. Where the sand is dropped, which is an extremely slow process, plants and animals convert it into nutrient laden soil. In some areas, particularly coastal and island, bird droppings has added hundreds of metres. Wickwack 124.178.149.139 (talk) 13:18, 10 November 2012 (UTC)

(ec)The atmosphere is fixated by abiotic sedimentation and biological fixation. Bodies with no atmosphere (like the Moon) don't fix new regolith. This process, and the loss of atmosphere to space, would leave the Earth without an atmosphere, and so this process would stop here too - but Earth is tectonically active, which means volcanoes are spewing forth new atmosphere, keeping the process going. Magma is produced from very deep material, so it doesn't disturb the geological layers except right where the volcano erupts. For human settlements (where the timeframe is just a few thousand or tens of thousands of years) many are quite literally buried with trash. And when archaeologists are looking at say a Roman villa, they're mostly looking at the foundations and a few layers of stones, and all the junk that got dropped down the cloaca or buried in the garden - the whole of centuries of life compressed down to a few inches. -- Finlay McWalterჷTalk 13:23, 10 November 2012 (UTC)

See also Erosion and Deposition (geology). Ghmyrtle (talk) 13:24, 10 November 2012 (UTC)

Indeed. There is also an large element of survivor bias here - most buildings (especially wooden ones) leave no trace behind, and most animals are not fossilised, so we only ever find the exceptional cases. Gandalf61 (talk) 13:33, 10 November 2012 (UTC)

Didn't Charles Darwin write up an estimate of the rate at which earthworms churn the soil? —Tamfang (talk) 16:14, 10 November 2012 (UTC)

Yes he did. His final book, reprinted many times as was much of his output, was "The formation of Vegetable Mould through the Actions of Worms." In it he described how earthworms effectively raise the level of the soil by a quarter of an inch per year. This obviously buries things after a while. HiLo48 (talk) 04:02, 11 November 2012 (UTC)

Exposed face of a peak in the French Alps

"Reshuffling", though oversimplistic, is basically correct. If you're asking about the "short term" origin of new rock layers, then the answer is as above. Fossils and artifacts are found in only one type of rock - sedimentary rocks. And it is subject to a somewhat semi-cyclical process of weathering, erosion, deposition, and lithification. In most cases, the sediments that constitute a certain stratum come from rocks exposed during that time period. The sources are often rocks set higher or at more exposed places that are then eroded into lower places (e.g. sediment from mountains eroding into lakes or basins which results in characteristic lentification). See also Stratigraphy, Stratum, and Stratigraphy (archaeology).

If you're asking about the "long term" origin of new rock layers, then the answer lies in the rock cycle. Remember that we are basically living on very thin floating islands of solid rock on top of a very deep "ocean" of "boiling" magma. All rocks on the crust (aside from those originating from celestial objects like remnants of comet impacts), ultimately derive from magma. But again, by long term, I mean very long term. Large parts of the crust haven't been to the mantle for a very long time, and are basically just being "recycled" as you implied earlier. Though conversely, some parts of the crust have long since disappeared forever back into the mantle, like the Farallon Plate which slid under the west side of the North American plate, leaving only bits and pieces and the Rocky Mountains as a testament to its demise. Plate tectonics itself play a part by deforming the rock layers (orogeny) as the plates move around. The movement of the crust can thrust layers of rocks up, down, or fold them around like taffy, exposing old layers to erosion and burying others. -- OBSIDIAN†SOUL 16:31, 10 November 2012 (UTC)

When it comes to archeology I think much of the layers are human made derbies and maybe soil from decomposing plants.Gr8xoz (talk) 20:35, 10 November 2012 (UTC)

Twin follicles in horses

From my understanding twin follicles are follicles produced at the same time and of roughly the same size and that they will produce twins. But I'm not sure why this produces twins and why it's a sign of pregnancy in the first place. Thanks. 138.253.210.27 (talk) 17:25, 10 November 2012 (UTC)

It basically has to do with the production of eggs (ova) in the estrous cycle. Aside from differences in timing and the way the uterine lining is disposed of if fertilization is unsuccessful, it is largely similar to human menstrual cycles.

Like humans, horses have ovaries which contain primordial follicles. In regular intervals coinciding with each estrous cycle (after puberty, of course), a number of these primordial follicles start to develop in a process called folliculogenesis. Note that more than one primordial follicle is being grown per cycle. They are essentially being grown in batches.

Once they reach a certain stage of growth where they are known as antral follicles, they enter the next stage known as the follicular phase. In this phase, the different follicles start to compete with each other until only one dominant follicle is selected. It is this swollen ovulatory follicle (around 35-50 mm in diameter) that is detected in the mare during estrus. This is not a sign of pregnancy. The presence of ovulatory follicles of the proper size only means the mare is ready for mating. That dominant follicle that emerges from the follicular phase will then proceed to ovulation, releasing a single egg into the uterus in the final phases of the estrus. If the horse has mated, then the egg will have a chance of being fertilized.

But in rare cases, two follicles will emerge as dominant after the follicular phase (in very very rare cases, more than two). This means two eggs will be released during ovulation (double ovulation, one per ovulatory follicle). This does not necessarily mean that the mare will bear twins though. Indeed multiple follicles have the advantage of increasing the chances of successful fertilization. But yeah, since there are more than one egg now in the equation, this introduces the possibility of both eggs being fertilized. If this happens, then yeah, you'll get twins (although note that these are fraternal twins, not identical, since they developed from different eggs).-- OBSIDIAN†SOUL 18:47, 10 November 2012 (UTC)

Cycling drugs

Users of recreational drugs normally 'cycle' them to be sensitive to them again, but users of legal psychoactive drugs seem to take them regularly during the whole treatment or even for an indefinite time. Do the potheads know stuff that the doctors do not? Are the potheads wrong? Or are both groups doing what works better for each one? Comploose (talk) 17:52, 10 November 2012 (UTC)

I question the second part. I think doctors often do cycle through various meds for their long-term patients. However, this isn't just to prevent loss of effectiveness of one med. Some other reasons:

A) A new med comes out and they want to try it, to see if it will be more effective or have fewer side effects.

B) Some meds require the patient to periodically take a break.

C) Rather than proactively, doctors will change meds after the fact, if they cease to become effective.

D) Switching doctors often means switching meds, too.

E) Some meds are already a mix of meds, like the AIDS cocktail.

F) Some meds have their content changed on a regular basis, like flu vaccines. StuRat (talk) 18:01, 10 November 2012 (UTC)

Drug tolerance is common in both recreational and normal use of drugs (corticosteroids for example need a rest phase). Since people who are hooked on a substance will use it frequently, it might be pretty common among this group of people to build tolerance. On the other hand, people who are just treating an illness will just stop using the substance once the treatment is successful. In some cases, it's the bacteria that are getting resistant to the drug, and not the patient, but in this case too, it's wise not to abuse antibiotics. 19:05, 10 November 2012 (UTC) — Preceding unsigned comment added by OsmanRF34 (talk • contribs)

Recreational antibiotics? Alternated with what? Ground glass capsules? Please do . μηδείς (talk) 23:08, 10 November 2012 (UTC)

Your vision must be better than mine; somehow you can see the phrase "recreational antibiotics" where none exists. Antibiotic abuse occurs when antibiotics are given when they're not required, as for a viral infection. You can read more about that here. My parents, for two, were terrible for that: bugging the hell out of our GP for antibiotics every time my sister and I got colds. Matt Deres (talk) 23:19, 10 November 2012 (UTC)

Thanks Matt, you got the point. Medeis is out of tone again. OsmanRF34 (talk) 00:02, 11 November 2012 (UTC)

Google at it again. It pointed me to this section when I was looking for this. Epic Google fail. - ¡Ouch! (^{hurt me} / _{more pain}) 08:51, 12 November 2012 (UTC)

How would {100} monocrystalline semiconductor grade silicon be made using common materials and no specialized machinery?

This video starts by casually saying they have such material. It seems safe to suspect that this is a person without access to million-dollar (or even multi-thousand-dollar) machines from Intel or any research lab. Yet they don't explain where they got or how they made the {100} semiconductor grade monocrystalline silicon. How could one individual make this then? Peter Michner (talk) 19:17, 10 November 2012 (UTC)

I do not see any statement that it is homemade, I would assume the boring answer is that they bought it some where.Gr8xoz (talk) 20:30, 10 November 2012 (UTC)

Third section down, second to last in section: Cz (made with Czochralski process ) <100> (orientation) 25.4mm diameter Undoped 1.5" thick 45 grams $360.00. With prices like that, it's probably not something easily makeable in the kitchen or the garage. 67.163.109.173 (talk) 23:17, 10 November 2012 (UTC)

Radiation from wifi

Does the radiation emitted from a laptop's wifi depend on what is being done (upload/download/idle)? Also, does it depend on the direction? (I'd be mostly interested in potential health issues, so perhaps in the radiated power!?) bamse (talk) 21:49, 10 November 2012 (UTC)

The radiation from Wifi is not functionally different than the radiation from other radio sources such as cordless phones, walkie-talkies, CB radios, etc. It is at the high-energy end of the Radio spectrum, but that doesn't necessarily mean much: visible light is higher energy radiation than WiFi and you're happily bathed in it every day with no ill effects. --Jayron32 22:07, 10 November 2012 (UTC)

Reading Wireless electronic devices and health or Electromagnetic radiation and health or Mobile phone radiation and health it is not as clear as you want to make it. I am not claiming there is an effect on health, but my question is: If there was an effect on health, would it depend on whether one is uploading/downloading or just having an idle wifi link? bamse (talk) 23:52, 10 November 2012 (UTC)

Yes, more energy is being radiated if the link is in use than if it is idle. Uploading will radiate more energy than downloading (reception of information isn't significant, but a downloading laptop is still continuously replying "yeah, I got that piece"). Downloading will radiate more energy than sitting idle ("yeah, I got that piece" in addition to the always-happening occasional "here I am" in all modes). Given that battery tests generally show a significant difference in lifetime-with-wifi and lifetime-without-wifi, I also suspect that wifi energy is a significant fraction of the overall radiated energy of the laptop. — Lomn 23:57, 10 November 2012 (UTC)

Thank you. bamse (talk) 16:18, 11 November 2012 (UTC)

(Not directly related to the topic, but...)

Shouldn't the articles Wireless electronic devices and health , Electromagnetic radiation and health , Mobile phone radiation and health be named Health effects of ... or Effects of ... on the human body? I can remember, though very vaguely, that article names like "ABC and XYZ" are to be avoided, is that a policy? - ¡Ouch! (^{hurt me} / _{more pain}) 08:50, 12 November 2012 (UTC)

Abiogenesis

Have humans ever successfully synthesized the most simple form of cell which is "Prokaryote" from inorganic matter? If we didn't then what are some recent attempts of doing it? 174.20.101.190 (talk) 22:27, 10 November 2012 (UTC)

Craig Venter claims that he has already synthesize bacteria. OsmanRF34 (talk) 22:37, 10 November 2012 (UTC)

It would help if you'd give a link to that, Osman. I find the claim dubious in the extreme. μηδείς (talk) 23:05, 10 November 2012 (UTC)

Well I have read the Craig Venter article and Synthetic biology article. In the Synthetic biology article, Craig Venter clearly said "we do not consider this to be creating life from scratch but rather we are creating new life out of already existing life using synthetic DNA." And according to the processes in which he used to create the cell are not entirely from inorganic matters. So that's not what I'm looking for.174.20.101.190 (talk) 23:12, 10 November 2012 (UTC)

Craig Venter's work is the closest thing so far. It's only a matter of time, though. Looie496 (talk) 00:15, 11 November 2012 (UTC)

Well I think we are capable of doing it right NOW but unfortunately there is no motivation to do so. In other word, no one is willing to put a big amount of money to do it. Pure interest is not a strong reason for any private funding or the government funding to jump in the case. Compare to the feat of getting to the moon, this is "a piece of cake". Let just look at Venter's work, it costs him 40 millions and he already got very close to a complete synthesized cell. Got man to the Moon cost billions of dollars back in 1960's and by today standard it must have cost a lot more. But the thing is the only reason that we, humans, got to the Moon is thanks to the "space race" between the US and Soviet Union. It wasn't done just for the sake of science to explore the universe. It is funny how everything has a good side. I think we just have to wait for a great cause as a catalyst for ultimate goal of completely synthesized cell. That is a very significant step forward something big! We used to think God is the only one who can create life out of scratch, it turned out not so much... Humans are not too bad compare to God!174.20.101.190 (talk) 07:10, 11 November 2012 (UTC)

To Osman: the popular press sold to their audience that Venter had created life. I do not know if Venter is happy with the way they depicted his development. Comploose (talk) 01:38, 11 November 2012 (UTC)

Genetics question

How accurate are the following statements? "The basic form of life is female. The first male specimens were evolved from females." A8875 (talk) 23:30, 10 November 2012 (UTC)

If one defines female as "An individual that physically produces an offspring" it is self-evidently true. Life cannot propagate if offspring are not produced. Males don't gestate or grow or give physical shape to offspring directly, excepting for a tiny few atoms that contain their genetic code. Functionally close to 100% of an offspring is created by the female body. Males contribute only information to creating offspring. It's a bit flawed to assign sex or gender to species that undergo asexual reproduction, but I see where that statement is going. It would be better to say that before sexual reproduction, there were no sexes at all, and that sexual reproduction created two genders: the Female that produces the egg and the Male that produces the sperm. Of course, many forms of female life don't actually give much more physical material to the offspring than males do. So it's not a great statement, but it's not completely wrong either. Just trite. --Jayron32 23:39, 10 November 2012 (UTC)

• It might be useful to look at our article on isogamy, which was probably the first type of sexual reproduction. In isogamy, individuals cannot be classified as either male or female. Looie496 (talk) 00:07, 11 November 2012 (UTC)

Right. Then the "first male specimens" question can be interpreted as a question on the evolution of anisogamy. SemanticMantis (talk) 05:19, 11 November 2012 (UTC)

Not quite what you're after probably, but it's worth noting that in mammals (at least in rodents and humans, don't quote me on the rest) the developing embryo is female as default, unless it's turned male by amongst other things the expression of anti-Müllerian hormone Fgf10 (talk) 08:04, 12 November 2012 (UTC)