Wikipedia:Reference desk/Archives/Science/2017 February 19

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.

February 19

I'd like to have my car tires vulcanized .......... by Buster Keaton's mechanic

• youtu. be/UWEjxkkB8Xs?t=2m31s

In an unnamed Buster Keaton movie, bad guys are after him and he tries to hitch a ride by sitting on a car's rear spare tire. The car drives away and Keaton finds himself remain in the same place. The spare tire is actually used as a roadside sign placed behind the car with a cardboard saying "Vulcanizing" and an arrow pointing to the shop.

Did people of the 1920s really have to have their car tires vulcanized by someone? -- Toytoy (talk) 01:55, 19 February 2017 (UTC)

Our article on Vulcanization describes it as "a chemical process for converting natural rubber or related polymers into more durable materials by the addition of sulfur[1] or other equivalent curatives or accelerators".

Clearly, that was already done to the rubber in tires before it was used to make them. However, the term "vulcanization" was also widely used to refer to the process of patching inner tubes of tires with thin pieces of vulcanized rubber, which I've done myself. You clean the spot around the hole of the tire, apply a solvent to the tire and the patch, then apply the patch to the now sticky rubber inner tube. Since almost all cars of the 1920s had tires with inner tubes, yes, they did from time to time require vulcanization in the sense of "repairing the inner tube of a tire with a patch of vulcanized rubber". loupgarous (talk) 02:19, 19 February 2017 (UTC)

Vulcanisation was the older process of repairing a puncture with a patch of unvulcanised rubber, then vulcanising it in-situ with heat and pressure. It's no longer performed, as later tyres gained greater quantities of filler materials and became less like pure rubber. Andy Dingley (talk) 02:56, 19 February 2017 (UTC)

Wups. You're right. We called it "vulcanization" when I was a kid, but in the 1960s you had to really hunt to find someone who did "hot vulcanization". But your answer is correct in the OP's context. loupgarous (talk) 03:22, 19 February 2017 (UTC)

Menstruation

Can high levels of stress or anxiety stop, delay, or otherwise affect menstruation? Benjamin (talk) 01:57, 19 February 2017 (UTC)

According to our article on Amenorrhoea, specifically the section Secondary Amenorrhoea, yes. Quoting:

"Secondary amenorrhea is also caused by stress, extreme weight loss, and excessive exercise. Young athletes are particularly vulnerable, although normal menses usually return with healthy body weight. Causes of secondary amenorrhea can also result in primary amenorrhea, especially if present before onset of menarche." loupgarous (talk) 02:39, 19 February 2017 (UTC)

Can it be caused by stress alone, and if so, how much? Benjamin (talk) 03:09, 19 February 2017 (UTC)

In standard units, that would be 3.27 mother-in-law days. :-) StuRat (talk) 03:27, 19 February 2017 (UTC)

Yes. The brain actually controls the cascade of events which lead to menstrual flow through the Hypothalamic–pituitary–gonadal axis, part of the neuroendocrine system.. As to "how much stress", that really depends on the individual woman. Each of us have unique bodies, and there's no single amount of stress sufficient to cause any physiological response across the human race - it varies from person to person.

And Stu, I've found mother-in-law mediated stress to be independent of the neuroendocrine system, and in some cases to be pathognomonic of Vistaril deficiency on the part of the mother-in-law. loupgarous (talk) 03:39, 19 February 2017 (UTC)

In answer to "how much," stress does not have a quantitative measure. In practice, small amounts of what others would consider trivial stress tend to cause far more harm than extreme levels of stress. If you are interested in this area, look into PTSD research. I don't want to make specific statements about veterans in our clinic, but it fits. Those who suffered very little stress have higher rates and worse forms of PTSD compared to those who suffered extreme stress. 209.149.113.5 (talk) 13:27, 21 February 2017 (UTC)

If the Solar System were brought to rest relative to the Galaxy then allowed to follow real physics what would the new orbit be?

Would the sum pulls of dark matter and gas, dust, and star clouds etc. cause an orbit that's not "drop to the center like a stone?" Sagittarian Milky Way (talk) 02:43, 19 February 2017 (UTC)

No offense, but "new orbit around what?" If all the masses in the Solar System lost their proper motion with respect to the rest of the Milky Way (the motion causing their galaxy rotation curve, specifically), strictly speaking the Solar System as a whole wouldn't have an orbit around the center of the galaxy. You'll have to define your question better, and while you're doing so, supply a mechanism by which this might be done. You'd have to supply an arresting force to every mass in the Solar System somehow which discriminated between the orbits of the objects in the Solar System around the Sun and those planets with moons or captive asteroids and their proper motion attributable to their galaxy rotation curve in the galaxy. Then you'd have to keep applying it unless you somehow abolish all the other mass in the Milky Way.  :"Dark matter and gas, dust, and star clouds etc." either part of the Milky Way or they're mass in other galaxies. Working out the resultant vector for a Solar System in which we woke up and found the rest of the Milky Way had gone away... we can't do that here in the Reference Desk.

We could, I suppose, estimate extragalactic masses from observation of their motion, but I don't think we'd get meaningful results, since those motions are likely much smaller than the limits of accuracy of how we measure them. And "dark matter" will be even harder to estimate the mass of, for obvious reasons. loupgarous (talk) 02:55, 19 February 2017 (UTC)

Around the center of mass of the Milky Way Galaxy. Why would you have to keep applying the force? Once it's stopped it has lost all it's galactic rotation curve momentum/proper motion and that is when you turn on real physics again and see what happens. It's not a plan, it's a thought experiment like Einstein's riding on a beam of light (even harder than stopping the galactic orbit as your body cannot reach the speed of light). Sagittarian Milky Way (talk) 03:47, 19 February 2017 (UTC)

Oh, I see. For your thought experiment, you postulated being able to switch the gravitational attraction between the galaxy and the solar system off for a while. If you've ever taken a pail with a rope tied to the handle, filled it half-full of water, then swung it over your head, you've got a heavenly body orbiting a massive object, with the rope representing the gravitational attraction between them. Now let go of the rope. See what happens? That's what happens to the solar system once the gravitational attraction between it and the center of the galaxy abruptly goes away - angular momentum sends the solar system away from the galaxy on a line tangential to its orbit around the center of the galaxy. Unless you are cancelling the Solar System's inertia while you're turning the gravitational attraction from the center of the galaxy off, too.

That's actually more plausible. Once you throw the switch back "on", are you restoring the gravitational pull from the galaxy, or not? loupgarous (talk) 04:31, 19 February 2017 (UTC)

You're focusing too much on how to get there from here. A thought experiment doesn't require that, you just jump to the new state. Nobody worries about how Schroedinger got the cat in the box. "Free prussic acid food inside !" StuRat (talk) 04:38, 19 February 2017 (UTC)

There would be some attraction to the matter in the arm, that might restore a portion of the solar system's original galactic rotation, but certainly not all, causing it to fall towards the center. As it did, it would pass other solar systems, potentially causing chaos as multiple solar systems are pulled out of position. What would happen to ours would be difficult to predict. It might even be possible for it to be ejected from the galaxy, at least temporarily. And the planets might get pulled away from the Sun in the process. StuRat (talk) 03:24, 19 February 2017 (UTC)

"Might" is a mighty weak word ;-). When two galaxies collide, actual close encounters of stars are still very very rare. Look up one clear night - how much of the sky is taken up by stars and how much by void? If the solar system magically lost its proper motion, it would - very slowly - start to fall towards the center of the Milky Way. Most likely, it would interact with enough other random stars to not pass exactly through the center, but bypass it at some distance. It would then drift out to about the current distance and there momentarily come to rest, before repeating the process. Unless it gains additional energy by some close three-body encounter, it will not be ejected from the galaxy. And the time scale for one full passage (back and forth) would be on the same order of magnitude as the current galactic orbit - hundreds of millions years. --Stephan Schulz (talk) 07:24, 19 February 2017 (UTC)

While stars are spread far enough apart that they aren't likely to collide, they are close enough so that they have gravitational effects on each other, especially over billions of years. Take a look at this page on galactic collisions, and note the animation of a simulation of such a collision, about 3/4th down, showing stars flying everywhere: [1]. StuRat (talk) 16:15, 19 February 2017 (UTC)

Yes, but that's a billion stars falling through a billion stars (give or take an order of magnitude). The vast majority of stars form the merged galaxy - the ones that are flung out are a small fraction. --Stephan Schulz (talk) 16:30, 19 February 2017 (UTC)

Correct, but that doesn't mean the stars that remain in the galaxy weren't affected by each other's gravity. Indeed, that's critical to changing the orbit of each into the new orbit in the resultant galaxy. If they didn't affect each other, the two galaxies would just pass through each other and continue on their way. StuRat (talk) 16:33, 19 February 2017 (UTC)

The gravitational pull would reduce as the planet approached the galactic center, so I think the orbit would take somewhat longer. Stars passing by at a distance (so as not to appreciably accelerate the Sun to puppy-dog along behind) would be expected to push and pull by roughly equal amounts. But there is substantial frame dragging from the galactic rotation that would pull on the Earth. Its magnitude is described in this interesting paper which has been published in Europhysics Letters. However, I don't know how to get from that to an orbital deflection. I would suppose the chance of collision should be much higher due to the greater relative velocity between the infalling star and the "usual flow of traffic". Wnt (talk) 13:01, 19 February 2017 (UTC)

Actual star/star collision chances would still be low, but the chances of passing close enough for a significant gravitational deflection of one or both stars (depending on relative masses) would be much higher. StuRat (talk) 16:48, 19 February 2017 (UTC)

Infections

Why don't all localised infections become systemic infections? Surely, if bacteria or other infection causing organism has entered the body, it will eventually spread? 2A02:C7D:B921:AD00:F95A:A035:E07C:21D6 (talk) 09:33, 19 February 2017 (UTC)

Any pathological organism entering the body will trigger a response from the immune system. Most minor infections will be suppressed but a few may become systemic. The result will vary according to such factors as the age and health of the individual, the type of infecting organism, for example. Try this site or Immune system for starters. Richard Avery (talk) 09:41, 19 February 2017 (UTC)

Then the next logical Q is how infections can overcome the immune system. Some methods are to attack the immune system itself, like AIDS does, or to just overwhelm the immune system when you are exposed to a large dose of bacteria or other microbes. StuRat (talk) 16:30, 19 February 2017 (UTC)

Search for Alien life

Have been looking for some information about the search for alien life; Yes i am aware of the usual Carbon based biological search but was looking for some good articles of people thinking out side of the norm and some fresh ideas of what could be a starting point. So the question i guess would be - What is the current thinking with regard to the search for alien life outside of the normal parameters? Also what if any ideas have people come up with to detect alien life forms that do not match the criteria layed down for life as we know it? Thanks for your help and/or thinking Adrian — Preceding unsigned comment added by 5.175.64.53 (talk) 11:27, 19 February 2017 (UTC)

Keep in mind that we are way far beyond searching for any particular type of life form. Other star systems are simply too far away to directly tell if they contain life, carbon or otherwise. Rather, searches for alien life have focused on looking for radio signals that cannot be generated naturally (thus far, no unambiguously artificial radio signals have been detected that were not created by humans, obviously). This type of search doesn't matter on the nature of the alien life. Searchers also have an eye for visual signatures of megastructures around stars, which again, doesn't matter on the nature of the alien life. See Search for extraterrestrial intelligence for more information, for starters. Someguy1221 (talk) 11:50, 19 February 2017 (UTC)

The question asker may be thinking about the chemical tests being performed by Mars Curiosity and not SETI. It's true that the search for Life on Mars has mostly been to look for organic compounds, or evidence of metabolisms like those seen on Earth life. The Life on Mars article is still worth a read. ApLundell (talk) 15:26, 20 February 2017 (UTC)

See Hypothetical types of biochemistry. --IEditEncyclopedia (talk) 12:00, 19 February 2017 (UTC)

Even biochemistry may be too limiting. Suppose, for example, that the complex magnetic patterns we see in the Sun are actually the result of some type of magnetic plasma life forms. StuRat (talk) 16:25, 19 February 2017 (UTC)

The article Search for extraterrestrial intelligence has extensive references and further reading. Blooteuth (talk) 18:55, 19 February 2017 (UTC)

Thank you Hypothetical types of biochemistry was a good article Adrian (from the article i am thinking best way to narrow down silicon based life would be to look at sulphuric acid rich environments ( just need a lot of equipment now )then look for structures) ment added by 5.175.64.53 (talk) 05:54, 20 February 2017 (UTC)

Theobromine toxicity

from the articles on theobromine and theobromine poisoning, it is clear to me that rats and humans can tolerate higher amounts of it because they have a much easier time metabolizing it than other animals, eg cats/dogs. My question is-- why? What digestive/metabolic adaptations do rats and humans have that allow them that much higher tolerance? is it a specific enzyme or something that other animals lack? i didnt see it mentioned in the articles if it was there, so apologies if this is redundant 206.47.249.251 (talk) 13:10, 19 February 2017 (UTC)

Seems like there's multiple pathways with multiple enzymes potentially involved in metabolising theobromine. Our article does mention metabolism in the liver by CYP1A2 and CYP2E1. This study shows a different metabolite pattern in different species, suggesting involvement of different enzymes. Fgf10 (talk) 15:13, 19 February 2017 (UTC)

[2] mentions several different pathways of metabolism and different profiles of products but also mentions the key difference seems to be in rates. BTW to clarify your later point, as I understand the source (sort of mentioned at the end of the abstract, but clearer if you check the full article), the same metabolites were mostly observed in all tested species. The qualitative pattern did differ, in other words the amount of each one. While it's possible different enzymes were involved in different species, this suggest to me more likely is the similar enzymes were involved in all species but different enzymes are more significant in each species. Nil Einne (talk) 15:31, 19 February 2017 (UTC)

Correct, my phrasing was inaccurate. Fgf10 (talk) 16:54, 19 February 2017 (UTC)

LDL and HDL are different from cholesterol?

I have been taught that cholesterol is divided into two: LDL and HDL so when I'm saying cholesterol it includes the two. But now I saw a short lecture made by university of Reading in the UK that states: "So how does HDL work? Well, we're not quite sure, but we think that it may work in the reverse way to LDL. LDL takes cholesterol from the blood into the arterial wall. HDL may take it the other way, from the arterial wall from atherosclerotic lesions back into the blood." it says that LDL takes cholesterol and that means that cholesterol is different from LDL. what is that? I'm a little bit confused. 93.126.88.30 (talk) 16:17, 19 February 2017 (UTC)

Let's start with your first sentence: "I have been taught that cholesterol is divided into two: LDL and HDL". You were taught wrong. Cholesterol is a

Lipid. HDL and LDL are Lipoproteins.

Cholesterol molecule

Lipoprotein structure (chylomicron)
ApoA, ApoB, ApoC, ApoE (apolipoproteins); T (triacylglycerol); C (cholesterol); green (phospholipids)

Simplified flowchart showing the essentials of lipoprotein metabolism.

Lipoproteins (LDL and HDL) transport lipids (fat) in your blood. Cholesterol is one of the lipids they transport. --Guy Macon (talk) 17:35, 19 February 2017 (UTC)

Thank you! I hope that I didn't understand my teacher properly rather than it's his mistake, because he is a scientist. Now I understand that LDL is like insulin which takes the glucose inside to the cell, but LDL takes cholesterol to the cells, and HDL take them out from there. Isn't it? 93.126.88.30 (talk) 20:18, 19 February 2017 (UTC)

That was a good try, but ... no, insulin is something else. It is a separate signal that goes to the cells and bangs on the door and says, "really, let this glucose in". The glucose just sits out in the bloodstream as a solution and is potentially available to the cells at any time. But a type I diabetic can essentially starve to death for lack of glucose even while his bloodstream contains five times more of the stuff than a normal person's. Wnt (talk) 21:42, 19 February 2017 (UTC)

Sorry, regarding to the first question now I'm reading on an article of the Open university in the UK the following things (which are similar to what my teacher said): "One of the risk factors for coronary heart diseases (CHD) is an inappropriate ratio of different types of fats in the blood, including the two sorts of cholesterol (known as HDL and LDL)." How can you explain these things, are they also incorrect or maybe I don't understand them well? 93.126.88.30 (talk) 00:15, 20 February 2017 (UTC)

This is an issue where context is important. A "serum cholesterol" lab does not pick out little bits of cholesterol in the blood and count them. It is not a count of the total cholesterol in the body. There is a hell of a lot more cholesterol in the body. The serum cholesterol lab estimates the amount of cholesterol in serum and separates it into the type of lipoproteins used: HDL, LDL, and VLDL. If you want an overly specific name, you can say "total cholesterol being transported inside a lipoprotein in the blood stream." We just say "total cholesterol." 209.149.113.5 (talk) 14:34, 20 February 2017 (UTC)

Sort of like saying "a four lane freeway can typically handle 100,000 drivers and passengers per day" when you really mean "a four lane freeway can typically handle 70,000 vehicles per day, all of which contain drivers and some of which contain passengers." --Guy Macon (talk) 10:04, 21 February 2017 (UTC)

Are there any microorganisms that wouldn't taste bad if you drank or chewed many grams of them?

Without added microorganism food, waste products, extracellular water etc, just piles of nothing but cells and still alive or at least not rotting yet (some microorganisms produce very polyunsaturated fatty acids that go rancid quicker than plant/animal fats, maybe that'd be tastable). Sagittarian Milky Way (talk) 18:21, 19 February 2017 (UTC)

Well, the food manufacturer that produces Quorn thinks their micro-organisms tastes OK (no comment as to what I think of it). Yet again their is yogurt, blue cheese, lactic acid fermented vegetables, etc., etc.--Aspro (talk) 18:43, 19 February 2017 (UTC)

Many foods contain a small portion of microorganisms, but that doesn't mean those would taste good when isolated. StuRat (talk) 19:55, 19 February 2017 (UTC)

And I'd bet much of the home sapiens population would dislike the taste of blue cheese. Maybe the Quorn species wouldn't be bad for most of humanity. Or the baker's yeast species (I forgot about yeast). If it tastes like the dry yeast packets then I'd say it's not bad. Sagittarian Milky Way (talk) 20:10, 19 February 2017 (UTC)

Bet most home sapiens can't enjoy a late-night supper with some really good Stilton and a wee dram or two of a really good double distilled malt (which imparts a heavenly peaty taste). Until they have tasted ambrosia they are just treading water, on this, their short sojourn through-this-world. Make the most of of a very short life and live a little; and dare to dip into the cornucopia. Enjoy! .--Aspro (talk) 20:46, 19 February 2017 (UTC)

Pro tip: Do not eat too much yeast. If you drink 2 cups of Snapple and swallow a 21 gram packet it'll ferment in your stomach and carbon dioxide will keep burping out. I imagine that 0.2 kilos of yeast and 0.2 kilos of sugar would be inadvisable. Sagittarian Milky Way (talk) 21:22, 19 February 2017 (UTC)

I think you have just invented the next "challenge" for teenagers to torment themselves with ;) Wnt (talk) 21:40, 19 February 2017 (UTC)

This does sound like great fun although the desired (?) result may be difficult to achieve. The stomach is a highly acidic environment and IIRC from my homebrewing days fermentation stops at pH of 4-ish and below. Shock Brigade Harvester Boris (talk) 23:11, 19 February 2017 (UTC)

Well, maybe yeast and its archrival baking soda/powder can collaborate on this one. ;) Wnt (talk) 00:39, 20 February 2017 (UTC)

There once was a lady from Ryde,

Who ate yeast and apples and died,

The apples fermented

Inside the lamented

And made cider inside her insides. MChesterMC (talk) 11:58, 22 February 2017 (UTC)

Nutritional yeast is added in fairly large quantities to many recipes. I think it tastes good. Some people put it on popcorn. See also Spirulina_(dietary_supplement)#Historical_use, a bacteria the Aztecs used to cultivate and eat. SemanticMantis (talk) 23:01, 19 February 2017 (UTC)

• Penicillium camemberti, Penicillium roqueforti, Penicillium glaucum, etc. --Jayron32 01:31, 20 February 2017 (UTC)

Spirulina_(dietary_supplement) can be eaten straight. Tellingly, the article doesn't mention how it tastes. ApLundell (talk) 14:35, 20 February 2017 (UTC)

Need bibliography about how, when and why to apply statistics

Need bibliography about how, when and why to apply statistics: what the median and the mean tells us, correlation not implying causation, problems that are intractable for stats, and so on.--Dikipewia (talk) 19:00, 19 February 2017 (UTC)

See arithmetic mean, median, correlation to start. As for when not to apply stats, one of the biggest problems is too small of a sample size. If you flip a coin and it comes up heads 9 out of 10 times, you can't conclude that it will continue to happen 9/10th of the time. You probably need over 1000 tosses to consider it a reliable sample size. (If it comes up heads or tails 900 of those times, it's probably not a fair coin.) Then there's the problem of introducing statistical bias, especially problematic when dealing with people, such as doing surveys. There's also the issue of cherry-picking. For example, many stocks can be said to have performed well or poorly, depending on how far back you go.

One interesting problem that can't be solved by stats is the likelihood of extraterrestrial life. Since we have only one sample case to work with (Earth), or perhaps a few more if you include our negative results (so far) looking for life elsewhere in the solar system, we really have no idea how common life is in the universe. See Drake equation. StuRat (talk) 19:11, 19 February 2017 (UTC)

That's a great post Stu, thanks! SemanticMantis (talk) 22:52, 19 February 2017 (UTC)

It would be very useful if the OP provided more details of why this bibliography is needed. Statistics is an incredibly complex area, although the OP's question seems to focus on the most basic of statistics. A couple more articles of relevance at this level are Parametric statistics, Nonparametric statistics, Statistical power, and Sample size - the last 2 are especially useful to avoid ethical concerns if the research involves animals . DrChrissy ^(talk) 20:02, 19 February 2017 (UTC)

I already included that last link. StuRat (talk) 20:12, 19 February 2017 (UTC)

I see you did - apologies for the repetition. DrChrissy ^(talk) 20:16, 19 February 2017 (UTC)

Also, Correlation does not imply causation. Loraof (talk) 22:00, 19 February 2017 (UTC)

Some additional reading: Inference, frequentist inference, statistical hypothesis testing, frequentist, bayesian, statistical regression, statistical model. We do have a whole category Category:Statistical_theory that you can browse using the little box at the bottom of an article like statistical theory. And yes, we can probably do better than a shotgun approach if you let us know what area your interest is in, or perhaps why. SemanticMantis (talk) 22:57, 19 February 2017 (UTC)

Huff's How to Lie with Statistics should be required reading for everyone, everywhere. Shock Brigade Harvester Boris (talk) 00:54, 20 February 2017 (UTC)

M. J. Moroney's Facts from Figures is essential reading. DuncanHill (talk) 17:19, 22 February 2017 (UTC)

Apollo 8

Apollo_8#Lunar_orbit "The SPS ignited at 69 hours, 8 minutes, and 16 seconds after launch and burned for 4 minutes and 13 seconds, placing the Apollo 8 spacecraft in orbit around the Moon. The crew described the burn as being the longest four minutes of their lives. If the burn had not lasted exactly the correct amount of time, the spacecraft could have ended up in a highly elliptical lunar orbit or even flung off into space. If it lasted too long they could have struck the Moon."

How did they calculate the exact burning time of 4 minutes and 13 seconds? --IEditEncyclopedia (talk) 19:07, 19 February 2017 (UTC)

Remember following this mission as it was happening. It was calculated on Earth by computer and relayed up to them before disappearing out of contact with Earth. They then had to time the burn on the Swiss made 'mechanical' wristwatches made by Omega -as the US did not have digital wristwatches at that time. planet-omega, space. This was the technique use on all Apollo missions. Newtons laws gave them all the algorithms they needed and Turing's work told them how to build the computer. Plan B was to use some plastic bags to defecate into; in case plan A didn’t work. --Aspro (talk) 19:32, 19 February 2017 (UTC)

They had watches, but the Apollo spacecraft had a digital clock (in the computer). I'm pretty sure that the start time and length of the burn were controlled by the computer. Bubba73 ^{You talkin' to me?} 01:08, 20 February 2017 (UTC)

Also, I don't think that the article is right about it having to be that exact. For one thing, it does NOT say that in the reference. Secondly, if it is off a little one way or the other, it would just go into an orbit of a different size. Bubba73 ^{You talkin' to me?} 01:13, 20 February 2017 (UTC)

On your second point, absolutely correct. They could make as many corrections as they like later on, until the fuel is exhausted, if a particular orbit is required. The reason to get it right the first time is that it is more efficient. On the other hand, mid course may not be (almost certainly is not) the most efficient place to do it either. Greglocock (talk) 07:44, 20 February 2017 (UTC)

In fact they did make a correction to the orbit later. They wanted a circular orbit 60 or 70 miles above the surface. The initial orbit was good at the perilune but 90 or 100 miles too high at the apolune. Another short burn made it more circular. Bubba73 ^{You talkin' to me?} 16:05, 20 February 2017 (UTC)

To Aspro, the Apollo astronauts voided in a specialized item nicknamed a "blue bag", and no improvisation involved. There was an entire, detailed procedure, including things I'll let our readers decide whether to see on this link, or not. NASA may have dropped the ball on the design of the Apollo 13 service module, but they generally knew their shit. loupgarous (talk) 19:43, 22 February 2017 (UTC)

Question about cryogenic preservation and transgender people

Out of curiosity--if a transgender person gets cryogenically preserved after they die (especially if only one's head or brain is cryogenically preserved), would it be possible to use stem cells or whatever to grow a new body for this person which matches his or her gender identity? Or would that create a risk of rejection due to the chromosomes (XY and XX) not matching?

Any thoughts on this? Futurist110 (talk) 19:11, 19 February 2017 (UTC)

So you would replace an X with a Y, or vice versa, right ? In the case of a male-to-female change, you could double up the X in their XY combo to create an XX, but you would run the risk of making X-linked recessive inheritance problems worse. An alternative would be a donor X or Y chromosome, as needed. See Chimera_(genetics)#Humans for evidence that a person can survive with two or more sets of genes (of course, this doesn't mean that all combos are viable). The bigger problem would be how to get the frozen brain into the new body, including the moral dilemma of what to do with the new brain that developed with the new body. Presumably the brain's development could be halted early on, but that would still be an ethical problem for many. StuRat (talk) 19:32, 19 February 2017 (UTC)

This is very speculative; I would be highly surprised if transplant rejection exists in a world where adult cloned bodies can be grown or tissue printer manufactured from scratch - but I cannot exclude it categorically. Technically little of the Y chromosome is actually needed for apparent maleness; the SRY gene handles most of the obvious morphological details. Functional testes would need other important genes. To make a female, the SRY could be inactivated with similarly little effort. Repairing and reviving the frozen brain is almost surely going to be the tough part. So far it looks like most tissues can be put through a tissue printing process at the cell level of resolution and the cells can figure out where they were supposed to be. But if you do that with a brain you have a blank slate, because the connections are synapses, i.e. subcellular, and long term potentiation similarly is not going to be represented with a newly printed cell. Some will say that any substitution of tissue at all makes it a "different person". (Others like me will say it's all atman so the cryonics is only potentially useful as a means of memory storage) But if you want to go through cell by cell and fix whatever freezing does to them, that could be a very finicky process... Wnt (talk) 21:36, 19 February 2017 (UTC)

Thanks for all of this information, you guys! Futurist110 (talk) 22:42, 21 February 2017 (UTC)

According to our article Histocompatibility, rejection of transplanted tissue is mediated by Human leucocyte antigens, the genes for which are found on chromosome 6p21, so that changes to the 23rd, sex-determination chromosome pair aren't likely to cause tissue rejection issues. A body and brain in which only chromosome pair 23 is different and the remaining genes are identical would have histocompatible cells and tissues, because their HLA would be identical. No rejection response is likely to occur in your hypothetical recombinantly-gendered brain transplant patient. loupgarous (talk) 20:37, 22 February 2017 (UTC)

American '80s car

What car is this on the right? https://scontent-lht6-1.xx.fbcdn.net/v/t31.0-8/16715950_10212273380500364_6250702806737612264_o.jpg?oh=fd4898f3e20308f8e608768000f67040&oe=592C9E04 212.30.205.63 (talk) 19:27, 19 February 2017 (UTC)

Looks like a Mercury Grand Marquis, to me. Compare: [3]. StuRat (talk) 19:36, 19 February 2017 (UTC)

Yes! you found it, thank you so much!! 212.30.205.63 (talk) 20:08, 19 February 2017 (UTC)

You're quite welcome. StuRat (talk) 20:10, 19 February 2017 (UTC)

Resolved

What is the reason that it's more healthy to eat unsaturated fats than saturated fats?

What is the reason that it's more healthy to eat unsaturated fats or trans fats than saturated fats? In the end of the day all of them fats (or lipids). They have the same atoms just with a minor different structure as it's easy to see on wikipedia articles and on google images. In addition I've read that in the room temperature (25C degrees) the saturated fats are solid (because of their straight chains) - such as butter etc. while those which are unsaturated fats are tend to be liquid in room temperature (because of their bent tails) - such as olive oil etc. Then I'm asking another question: Is there relation or correlation between the recommendation to avoid of saturated fats to their character to be solid (and maybe because of that they sink in the blood vessels and make troubles) or no relation between this character to the mentioned recommendation? 93.126.88.30 (talk) 20:34, 19 February 2017 (UTC)

Trans fats are generally considered much worse than saturated fats, not comparatively good like unsaturated fats. But "The exact biochemical methods by which trans fats produce specific health problems are a topic of continuing research" (see Trans fat § Health risks). And there are even several subclasses of unsaturated that have various patterns of effects. For example: "Polyunsaturated fats protect against cardiovascular disease by providing more membrane fluidity than monounsaturated fats, but they are more vulnerable to lipid peroxidation (rancidity). On the other hand, some monounsaturated fatty acids (in the same way as saturated fats) may promote insulin resistance, whereas polyunsaturated fatty acids may be protective against insulin resistance." (see Monounsaturated fat § Relation to health). Some of our articles only go so far as to note correlations with health effects, rather than being able to explain the actual biochemical/biophysical processes. DMacks (talk) 22:33, 19 February 2017 (UTC)

See here, 13 minutes 40 seconds into the video. Count Iblis (talk) 00:16, 20 February 2017 (UTC)

There isn't any reason, because it (unsaturated better than saturated) is almost certainly false. (Basically everyone agrees that trans fats are bad, worse than the other two.) What happened is that a few decades ago a vocal minority of scientists, mainly in the USA, jumped the gun and decided what was right based on equivocal evidence. Their (still) unproven (more like disproved) hypotheses became institutionalized dogma - for instance they came up with dietary recommendations which virtually certainly have done more harm to public health than good - e.g. leading to insouciance about carbohydrate intake for diabetics that would have horrified earlier generations. (They horrify me!) But Slllooowwwwllly minds & institutions & recommendations change - e.g. European countries and recently the USA have stopped giving dietary recommendations on cholesterol & demonizing it. Read e.g. Gary Taubes & many others on the history.

The far more important metaprinciple to absorb is - Science sometimes goes Backwards. The human race, no more than an individual is destined to always Do Things Right. The human race gets something right, a brilliant genius or a school of researchers or many competing thinkers discover something, enlighten everybody & then ...... everybody kinda forgets it, it becomes unfashionable, they stop understanding it (or more accurately, enough realize they never did understand it well enough). It is replaced by something inferior, sometimes grossly inferior & a generation can become attached to the inferior cognition, usually because they never even heard of anything else. But however long it takes, the steps forward tend to exceed the steps backward; while individuals often emotionally cannot, the human race as a whole does admit: "Mistakes were made." But again, denying that many spheres of science sometimes go full speed backwards - in many fields & not just in the Distant Past of Yore, but Right Now - is to not understand history & philosophy & the history & philosophy of science, for there really isn't any other way for things could be.John Z (talk) 05:51, 20 February 2017 (UTC)

But that's not because unsaturated fat isn't so bad, rather it's because unsaturated fat is not as good for us as we used to think, see here: "The Mediterranean Diet is healthy IN SPITE OF olive oil, not because of it." So, the best diet you can eat is a salt, sugar and fat free diet where all your essential Omega-3 and Omega-6 fats come from what is in the vegetables and grains. Count Iblis (talk) 06:43, 20 February 2017 (UTC)

See cherry picking. There's enough individual studies to back up any statement you wish to make. Understanding comes not from individual studies but rather from the preponderance of all studies. --Jayron32 13:52, 20 February 2017 (UTC)

Temperature of boiling liquids

When we boil water in a pot, at what temperature is the surface or middle of the water in the pot when the bottom starts to bubble?

If we heat two mixed liquids (like water and alcohol, which evaporate at 100 and 79 C respectively), will the boiling point of both change? Would the whole alcohol evaporate before water starts evaporating? --Llaanngg (talk) 21:46, 19 February 2017 (UTC)

For your second question, you may want to read our Azeotrope article. CodeTalker (talk) 22:04, 19 February 2017 (UTC)

There's no easy single answer for your first question. Heat transfer mechanics is extremely messy and complex and requires some serious advanced mathematics to model, especially for fluids such as water. Convective heat transfer is where you want to start your studies. Good luck. --Jayron32 01:27, 20 February 2017 (UTC)

Also, for the theory behind boiling points of mixtures, see Eutectic system. This is mostly refered to when melting Alloys but it is the same principle for many other nonmetal elements. --Kharon (talk) 02:29, 20 February 2017 (UTC)