Wikipedia:Reference desk/Archives/Science/2020 June 26

= June 26 =

Saturn V
Hello I'm working on Saturn V and I found that it is a unsourced paradise. Could you find some sources in general as there is not one place that does not have sources. Thanks, Signed, The4lines &#124;&#124;&#124;&#124; (You Asked?) (What I have Done.) 03:42, 26 June 2020 (UTC)


 * There are nearly 100 references, and some of them are used more than once. Bubba73 You talkin' to me? 05:42, 26 June 2020 (UTC)

Ethics or lack thereof. Transmission by microbes?
Could morals, or even mores(such as respectability seeking, “healthymindedness”, crudity, monogamy, etc), or their opposites, be transmitted by microbes? What about kindness and cruelty?Rich (talk) 04:00, 26 June 2020 (UTC)


 * Almost certainly no. microbes simply don't contain enough information, and most of the information they do contain is instructions for making more microbes. Also there is no known mechanism that would have the effect you describe. Also, in general most microbes cannot cross the blood brain barrier.


 * That being said, if you are willing to take a small step upwards in complexity, Toxoplasma gondii has an effect on humans similar to what you are talking about. --Guy Macon (talk) 04:32, 26 June 2020 (UTC)


 * Fun facts from Toxoplasma gondii: Toxoplasma infection was 2.4 fold more common in people who had a history of manic and depression symptoms, and students who tested positive for T. gondii exposure were 1.4 times more likely to major in business, 1.7 times more likely to have an emphasis in "management and entrepreneurship", and 1.8 times more likely to have started their own business. --Guy Macon (talk) 04:38, 26 June 2020 (UTC)


 * It's well known that traumatic brain injuries can make people become violent. Thus we see things like millionaire professional football players going off on idiotic crime sprees.  It's not too big a stretch to imagine some infections having the same result.  And as Guy Macon says, Toxoplasma has a longstanding suspicious relationship with schizophrenia and other mental illnesses.  As for positive changes, I haven't heard of any bacterial or viral agents causing that, but there's ongoing research as to whether plant extracts like psilocybin mushrooms (or other chemicals like MDMA) can do that: see MAPS for some info. 2602:24A:DE47:BB20:50DE:F402:42A6:A17D (talk) 06:22, 26 June 2020 (UTC)


 * Looking at this the other way, it's feasible that certain human behaviours and moral codes have evolved over time as a response to the prevalence of infectious microbes i.e. humans change their behaviour in order to minimise transmission, and over time these behaviours become codified into societal morals. Witness the massive change in human societies caused by the current pandemic - it isn't difficult to imagine that where such pressure exists over a prolonged period, human behaviour becomes permanently altered (sexual morals might be an example). PaleCloudedWhite (talk) 06:24, 26 June 2020 (UTC)


 * Not the transmission of morals but viruses can influence human behavior. I am familiar with this case. An individual had an episode of severe abdominal flu during an epidemic. Upon recovery it was found that he had autoimmune hemolytic anemia and a genetic test showed that 9% of his DNA was epigeneric material. No visible influence on his behavior but potentially... AboutFace 22 (talk) 17:24, 26 June 2020 (UTC)
 * Thanks to all for valuable information and comments...Even if microbes can’t cross the blood brain barrier, they could still manipulate hormones, couldn’t they? Couldn’t they infect the peripheral nervous system also? I’ve heard viruses like herpes do something akin to that. With some time of illness and/or changed hormones, could the blood brain barrier be breached? Also, isn’t the blood brain barrier less effective for young children?Rich (talk) 19:09, 27 June 2020 (UTC)
 * Please see Table 1 on page 192 here. As most social behavior is learned nurture instead of ancestry nature, this article may be also of interest. 98.33.89.17 (talk) 22:53, 27 June 2020 (UTC)

Starlink Sun shield
How effective is the sun shield used on recent Starlink satellites? (how many magnitudes of brightness reduction?) Bubba73 You talkin' to me? 05:41, 26 June 2020 (UTC)


 * Current Starlink satellites have an average apparent magnitude of 5.5 when on-station and brighter during orbit raise. We don't have firm numbers for the new design because they need to experiment with different attitudes, especially during boost, and it wouldn't be unusual for the shade design to go through several iterations, each more effective than the last. Right now it looks like they will be able to hit magnitude 7 or better with the current design. That should make them invisible to the naked eye. SpaceX is also working on better CCDs for large telescopes that aren't as effected by satellites -- any satellite, not just starlink. In theory, they could remove power to individual pixel sensors at the moment that you know that they will be looking at a satellite. At the very least they could fix the problem with current sensors where a single saturated pixel screws up an entire row or column of pixels.


 * For more info, see and . --Guy Macon (talk) 07:23, 26 June 2020 (UTC)


 * Thanks. I can't see magnitude 5.5 anyway, but I could see them when they were between 3 and 4.  Bubba73 You talkin' to me? 21:50, 26 June 2020 (UTC)


 * It's a fascinating engineering problem. To avoid overheating, a satellite should be white or shiny. To avoid being seen it should be flat black. Except you don't get to choose the color of the solar cells. The shades can be flat black because we can easily make them so they don't get damaged if they get hot. We should also try to make the shates thermal insulators so that the back side isn't a glowing light source in the infrared illuminating the satellite. That makes the front side even hotter, though, changing the color temperature and intensity of the IR coming from the front of the shade. But if the front side points way from the earth, who cares? Except that there are telescopes in orbit. Now to add another complication: it isn't just the sun that shines light on a satellite to be reflected. It also experiences moonlight (varies with the phase and position of the moon) and earthlight (varies with amount of cloud cover and time of day). So many variables to juggle! --Guy Macon (talk) 13:14, 27 June 2020 (UTC)

Economists on Health Care
This one has me perplexed. The National Bureau of Economic Research published a paper regarding the spread of covid-19 among BLM protesters. The paper has received coverage from the mainstream press. As best as I can tell, the National Bureau of Economic Research is a respected, peer-reviewed journal. However, their field of expertise appears to be economics, not health care. I would think such an article would be reviewed and published by a medical journal, not by an economics journal. Am I correct in thinking that they published an article outside their field of expertise? Is so, is this frowned upon within the scientific community? A Quest For Knowledge (talk) 07:12, 26 June 2020 (UTC)


 * I don't think it matters. "NBER working papers are circulated for discussion and comment purposes. They have not been peer-reviewed or been subject to the review by the NBER Board of Directors that accompanies official NBER publications."


 * It looks like the Center for Health Economics & Policy Studies at San Diego State University got a grant from the Charles Koch Foundation and the Troesh Family Foundation to do this study, and CHEPS chose NBER as a venue to put it out without peer review. One would hope that they have plans to submit it to a peer-reviewed journal in the future. Until they do it fails WP:MEDRS. --Guy Macon (talk) 07:32, 26 June 2020 (UTC)


 * Thank you for the informative answer. I wasn't planning on using it in an article.  I just found it curious that economists are publishing articles about medical issues.  A Quest For Knowledge (talk) 18:02, 26 June 2020 (UTC)
 * do you know about The Equality Trust? Epidemiologists on economics. 2601:647:5E00:C5A0:D4D0:DEF7:89B4:1B85 (talk) 07:45, 1 July 2020 (UTC)

What was the Sun's global magnetic polarity (N or S) at the end of Solar cycle 24?
I'm having trouble finding this fairly simple info (in Wikipedia or elsewhere). For the just-recently concluded Solar cycle 24 and during the associated solar minimum, which direction is/was the Sun's overall dipolar magnetic field pointing in relation to the Sun's rotation axis? (For comparison, the Earth's magnetic field is currently pointing (mostly) in the opposite direction of the Earth's positive rotation vector, since the magnetic pole in the Arctic is actually a "south-seeking" pole.) Also, is it safe to say that the conclusion of every previous even-numbered cycle (22,20,18,16,...) had this same polarity? DWIII (talk) 07:49, 26 June 2020 (UTC)


 * The Sun's polar field reversals are out of phase with our way of segmenting sunspot activity in cycles: these reversals occur during the cycle maximum, halfway each cycle. (You could say instead that our way of segmenting is out of phase with the Sun.) As far as we know and understand these solar cycles, they are driven by the polar field and its reversals, so it is a safe bet that as long as the Sun does not do something unexpected like a double somersault, the polarity change during a cycle goes the same way for cycles whose numbers have the same parity (and the opposite way for the others). There appears some uncertainty, though, whether 1784–1799 was one unusually long cycle, or two unusually short cycles, so going back all the way to the 18th century the bets are off. Figure 22 in the paper "The solar cycle" shows that the field flipped from positive polarity north pole to negative polarity north pole during the maximum of cycle 23. So it should have flipped the other way during the maximum of 24, meaning that right now the Sun has positive north pole polarity. The paper linked to is an overview of about all that is known about the solar cycle. --Lambiam 07:17, 27 June 2020 (UTC)


 * Thanks(!); that source is definitely informative. So, I take it that, by convention, "positive polarity north" is synonymous with "north-seeking magnetic pole aligned with geographical north", meaning that the dipole magnetic fields of the Sun and the Earth are currently (as of 2020) pointing in opposite directions (coincident with the end of cycle 24 and the beginning of 25).  The primary reason I asked is that, while Earth's magnetic field direction is indicated through geologic time in the geomagnetic reversal article, there doesn't seem to be any mention of specific polarities in the main solar cycle article article, or even in any of the individual solar cycle articles.  Yes, there is that blue-yellow graphic which seems to indicate polarity over the last four cycles, but it's not at all clear that "yellow = magnetic north".  DWIII (talk) 16:38, 27 June 2020 (UTC)


 * With the existing confusion (the North Magnetic Pole, often referred to as the "Magnetic North Pole", is a magnetic south pole). I wasn't too sure about the convention in solar science, so I just copied the terminology of the paper without attempting to interpret it. As this book observes, these terms can be very confusing when applied to the Sun. (Unfortunately, the treatment in that book does not do much to quell the confusion.) Customarily, the "positive" pole of a magnet is its north-seeking pole. I assume the paper uses the same convention when using the term "positive polarity". --Lambiam 20:07, 27 June 2020 (UTC)

Iron etc
When one reads about dietary supplements such as Iron, e.g. "...Brussels sprouts are rich in iron..." is this the same substance as Iron such as cast iron bridges are made out of? I have read the article but I am still unclear. Thank you. — Preceding unsigned comment added by 86.162.76.127 (talk) 09:27, 26 June 2020 (UTC)
 * Yes, and no. (Helpful, heh?)
 * If you have a solid grasp of chemistry already, a link to our article Human iron metabolism might be all you need. If you remember the basics, read on. And if you forgot even the high-school classes, I give a quick summary in the box below.

Matter is made of elementary bricks called atoms which are made of a (positively-charged) nucleus and a cloud of (negatively-charged) electrons. Because nuclei are (almost) impossible to break up, they are used to define chemical elements of the periodic table, of which iron is a part (it is the element with 26 protons in its nucleus). It is however much easier to move electrons around.

Chemical elements tend to combine into molecules due to two effects. For (fairly simple) electrostatic reasons, big chunks of matter tend to be electrically neutral, so molecules that are not electrically neutral (called ions) will tend to combine with other ions to make up for their excess or default charge. But for (insanely complicated) atomic orbital reasons, electron clouds with certain number of electrons are more stable than with other numbers. For example, salt is the NaCl molecule, made from sodium (Na) and chlorine (Cl). Sodium has one more proton than neon whose electron cloud is very stable, so it would very much like to be in the form of the Na+ ion (sodium with one positive charge, that is one less electron than protons). On the other hand, chlorine has one less proton than argon whose electron cloud is also very stable, so would like to form Cl- (one excess electron). Hence, having sodium "lend" one electron to chlorine makes a molecule that is both electrically neutral and where every atom has nice electron clouds, resulting in a much more stable structure than the separated atom (sodium is notoriously unstable, sodium in water is a dangerous but fun experiment).

The above only describes ionic compounds; there are other ways of forming molecules, but they do not matter much for basic iron chemistry. Iron has the symbol Fe and usually likes to lend 2 or 3 electrons (i.e. to exist as Fe2+ or Fe3+ ions). Oxygen (symbol O) is fairly common on Earth and in the atmosphere, and likes to borrow two electrons (i.e. to exist as O2-). Hence there are molecules such as Fe2O3 where 2 iron atoms lend 2x3=6 electrons to 3 oxygen atoms that take 2 each.


 * Iron atoms are indistinguishable and thus, at the atom level, iron in a bridge and iron in a vegetable are identical. However, those iron atoms can exist within different molecules.
 * Bridges are usually made of steel or cast iron, that is a crystalline structure of pure iron with some carbon atoms sneaking inside the holes of the structure, forming an interstitial alloy. (Cast iron = high-carbon steel; "crystalline" = periodic ordering of atoms.) In a bridge, we do not want the iron to be oxidized in the Fe2O3 form by oxygen in the air; that phenomenon is called rust and must be avoided (usually by paints that do not let oxygen through).
 * On the other hand, humans do not usually eat chunks of metal. Human_iron_metabolism says that iron crosses cell walls in the Fe2+ form (see this article for details) and that enzymes can reduce the Fe3+ form into Fe2+. I suppose (but could not find a proper source for that) that most if not all of iron in edible food is in ionic compounds such as Fe2O3. Notice also that only a fraction of iron in the food makes it through the digestive tract, and that amount may also depend on cooking procedure.
 * Hence, the molecules and chemistry for both cases are significantly different, even though the atoms are the same.
 * I would also add that the largest part (probably more than 90%) of the "dietary supplement" industry is a giant scam selling health dreams to misinformed consumers. Iron deficiency is real (unlike other deficiencies advertising would have you correct with their products), but do not buy iron supplements on your own (and definitely do not lick metal scrap pieces!). Go see your doctor and buy supplements only if they so prescribe (and then, buy what they prescribe, even if some TV salesman tells you that their supplement has "four times the iron intake of others" or whatever). Most likely, if you are not at immediate risk of anemia or another iron-deficiency-related disease, they will suggest diet changes rather than supplements. Tigraan Click here to contact me 10:44, 26 June 2020 (UTC)
 * Thank you and, WOW! what great answers. It is really appreciated.  Now I know.  BTW, the reason for asking was that an acquaintance suffers from high iron and has to donate blood on a regular basis as a lifelong cure.  Without this he freezes and goes stiff and faints.  Not a medical question, but pure intellectual curiosity. — Preceding unsigned comment added by 86.162.76.127 (talk) 12:14, 26 June 2020 (UTC)


 * It is very common for chemical elements to be listed as the constituents of commercial products when, in fact, the product contains compounds of the elements, not the elements in the pure state. For example, many garden fertilizers come in packaging that specifies it contains nitrogen N which is a gas at room temperature and pressure. The fertilizer contains compounds of nitrogen, not nitrogen gas. Similarly, fertilizers are stated to contain phosphorous P which is a rather hazardous substance in its pure state. What the fertilizer contains is one or more compounds of phosphorous and those compounds are not hazardous. Similarly with potassium K, a dangerously reactive metal in its pure state. So when I see a statement that a food is rich in iron Fe I assume the statement is actually referring to one or more compounds of iron. Dolphin ( t ) 12:52, 26 June 2020 (UTC)
 * In the same vein, see Louisville Waterfront Park, where a sign was posted warning visitors tempted to dip in the fountain that the water "contains high levels of hydrogen". I am both admirative of a great user design idea and sad that it works better than "please do not bathe in the fountain" (or at least was expected to work by someone whose job it is to design such warnings). Tigraan Click here to contact me 15:01, 26 June 2020 (UTC)
 * I bet a chemical analysis would show the presence of dihydrogen monoxide (DHMO) in that fountain. --Lambiam 19:48, 26 June 2020 (UTC)
 * Except maybe in the dry season. ←Baseball Bugs What's up, Doc? carrots→ 20:03, 26 June 2020 (UTC)
 * Re "It is very common for chemical elements to be listed as the constituents of commercial products when, in fact, the product contains compounds of the elements, not the elements in the pure state", whenever I see "low sodium" on a food package, I think "I certainly hope so!"   :)   --Guy Macon (talk) 11:01, 27 June 2020 (UTC)


 * A common grade school science project involves magnetically separating from cereal the powdered iron filings added for fortification. See this short (0:58) BBC Science Focus Magazine video: How to extract iron from cereal[YouTube]. -- ToE 13:04, 27 June 2020 (UTC)
 * Short answer: yep. But why is that? Why do we have all this iron lying around? Turns out iron is one of the most common elements in the universe. And that, in turn, is because iron-56 is one of the most stable nuclides. This happens to be bad news for stars, which "live" on the main sequence by fusing nucleons in their cores to free up energy. High-mass stars wind up accumulating "inert" iron cores as they age. Eventually the star runs out of enough "lighter" elements to fuse, it stops being able to support itself against gravity, it collapses, and kaboom: it explodes in a supernova, which spews a bunch of this iron along with other elements out into the universe. (There's also another type of supernova that occurs when a stable white dwarf gets a bunch of mass added to it. The details differ, but the end result is the same: star fuses a bunch of stuff and goes boom; these also release plenty of iron.) --47.146.63.87 (talk) 09:37, 28 June 2020 (UTC)

Ferrite core frequency response
Is this article correct in saying that ferrite cores are significantly lossy below a certain frequency range, and if so, then what's the explanation for that fact? I (think) I understand why it's true for frequencies above a certain range (due to hysteresis and eddy currents). ZFT (talk) 19:07, 26 June 2020 (UTC)
 * Hysteresis is a more significant loss factor at lower frequencies. See here (page 154 in the chapter; section "Core Losses"): " • At low frequencies, ferrite core loss is almost entirely hysteresis loss." --Lambiam 19:42, 26 June 2020 (UTC)