Wikipedia:Reference desk/Archives/Science/2015 June 21

= June 21 =

Cases of natural adrenaline halting anaphylaxis
Are there any cases in medical literature where severe anaphylaxis was stopped without medical intervention by the persons body naturally releasing enough adrenaline into their blood stream? Maybe as a result of heightened anxiety or stress from the reaction? 2001:268:D005:E529:B926:913F:AB27:B1C (talk) 05:40, 21 June 2015 (UTC)
 * According to Epinephrine, normal range (adrenaline blood concentration) is 10 ng/L, ten times that during exercise and fifty times during stress, so around the normal maximum is around the 500 ng/l mark. A medical dose produces 10,000 to 100,000 ng/L, off by a factor of 20. So it seems unlikely to me that a severe anaphylaxis episode could be stopped by a "natural" release of adrenaline. Vespine (talk) 23:02, 21 June 2015 (UTC)

Is putting sperm directly into a man's bloodstream a guaranteed way to permanently sterilize him?
This question is purely theoretical for the time being; however, I am genuinely extremely curious about this: Is putting sperm directly into a man's bloodstream a guaranteed way to permanently sterilize him? As in, is this type of male sterilization incapable of ever failing for any male?

Any thoughts on this?

Also, Yes, this is certainly a completely serious question. Futurist110 (talk) 07:28, 21 June 2015 (UTC)


 * Why would anyone think that is a method of sterilization?--Shantavira|feed me 07:55, 21 June 2015 (UTC)


 * Because vasectomies can and sometimes do fail? Futurist110 (talk) 08:01, 21 June 2015 (UTC)
 * Yes, vasectomies fail in a very small percentage of cases but are highly effective otherwise. But the alternate method you suggest has absolutely no evidence in its favor, and is nothing more than a bizarre delusion. Cullen328  Let's discuss it  08:05, 21 June 2015 (UTC)


 * I've got a question, though--please pardon any extreme ignorance which I might have in regards to this, but isn't putting a man's sperm into his bloodstream going to cause this man's immune system to reject his sperm? After all, isn't that why some vasectomies are not reversible? Futurist110 (talk) 08:07, 21 June 2015 (UTC)


 * Also, for what it's worth, I previously saw a similar question here: https://answers.yahoo.com/question/index?qid=20081218192630AA95oVu Futurist110 (talk) 08:09, 21 June 2015 (UTC)


 * In addition, this Wikipedia article appears to be of value in regards to this: Blood–testis barrier. Futurist110 (talk) 08:28, 21 June 2015 (UTC)


 * Who was it, some months ago, that asked about injecting an embryo into the bloodstream? ←Baseball Bugs What's up, Doc? carrots→ 13:17, 21 June 2015 (UTC)
 * This one: Reference desk/Archives/Science/2015 April 1 ←Baseball Bugs What's up, Doc? carrots→ 13:31, 21 June 2015 (UTC)


 * Both cases, injecting sperm or an embryo into the bloodstream, seem bloodcurdling, literally, even when experimenting with animals. Everybody knows that what you need is a virgin's blood transfusion. However, the big corporations don't want we to know that it can cure anything.--YX-1000A (talk) 18:06, 21 June 2015 (UTC)


 * There is an article, kind of short however, about this - hematospermia.--YX-1000A (talk) 13:26, 21 June 2015 (UTC)


 * We're not supposed to give medical advice, which answering this question would amount to. So, maybe. InedibleHulk (talk) 20:31, 21 June 2015 (UTC)
 * Discussion about appropriateness of question at WT:RD. -- ToE 00:10, 22 June 2015 (UTC)


 * This question is presumable premised on information such as that expressed in Vasectomy_reversal:
 * 2. Approximately 50%-80% of men who have had vasectomies develop a reaction against their own sperm (i.e., antisperm antibodies). High levels of these proteins directed against sperm may impair fertility, either by making it hard for sperm to swim to the egg or by interrupting the way the sperm must interact with the egg.
 * The question is then whether a male contraceptive could be developed in which the subject is vaccinated in order to encourage the development of these anti-bodies. The most recent review article on the subject that I've located is from the July 2011 American Journal of Reproductive Immunology, Antisperm contraceptive vaccines: where we are and where we are going?  Our article on the subject is Immunocontraception.  Such methods utilize sperm-specific antigens, not whole sperm, following the common practice of vaccinations. -- ToE 01:42, 22 June 2015 (UTC)
 * I'm wondering why a man who has had a vasectomy would be worried about impaired fertility. Isn't that the purpose of having a vasectomy? Liz  Read! Talk! 20:41, 22 June 2015 (UTC)
 * Well yes, but sometimes people want to have vasectomies reversed. The idea that some vasectomies cannot be effectively reversed due the formation of an immune response to one's own sperm is what makes the OP's question not nearly as strange as it might have seemed at first. Unfortunately, a lot of responders like to jump to conclusions that OPs are seeking advice or trolling, merely because they themselves don't understand the context. That confused the issue here, but at least some of us might have learned something in the process. SemanticMantis (talk) 20:59, 22 June 2015 (UTC)
 * I think there's a wider issue being missed here. The OP appears to be looking for a method more effective thea a vasectomy. In fact technically they said they were looking for "permanent sterilisation". This method may very well work and be fairly effective, but there's still no reason to think it will be more effective than a vasectomy let alone achieve permanent sterilisation (whatever the OP means by that). The related research highlighted above doesn't suggest such a goal, instead the primary goal seems to be an effective but simple and non surgical method of contraception for men and possibly women, that may be reversible. (Notably if the OP means non reversable, for the reasons highlighted above and particularly below, I don't think irreversible is generally a common goal of much contraception research. Instead high effectiveness, low price, low side effects, low difficulty of the method and similar factors are targetted while intentional reversibility is actually desired.) Vasectomies may fail, but the failure rate is low, perhaps around 1% or so within 5 years which is fairly good in contraceptive terms. I think this is with "perfect use", but I believe perfect use of a vasectomy mostly requires abstinence or alternative contraception for the first 3 months or until sperm count drops to zero, whichever is later. (Which seems to be what the source says too.) For someone as worried as the OP, would hope they could follow this requirement. Note also that this failure rate probably includes surgical error, if you're really that worried it may make sense to choose a surgeon who with more experience even if they may cost more for a hopefully lower failure rate. Note that the statement "vasectomies cannot be effectively reversed due the formation of an immune response to one's own sperm" should be treated with care less the OP is mislead. Quite a high percentage of vasectomy reversals may be fairly ineffective or can be classified as failures partly for this reason. But it may often be a combination of factors (particularly age possibly of both partners) that's the reason for the failure i.e. causes no pregnancy. In particular, when we're talking about very low failure percentages already for a vasectomy of 1%, it would be foolish to assume the problem this causes for reversals tells us it's likely to be more effective than a vasectomy. Notably we don't know why the reversals which do succeed aren't sufficiently affected. Is it because of no immune response or because the immune response isn't really that effective? A significant point is that the absence of any of the antigens in the blood stream may mean there are few antibodies. (As with all vaccinations, the body may be "primed" to respond, but it still needs something to respond to.) Complete speculation here but in the case of a vasectomy, it could be the testes blood barrier often isn't completely re-established and that causes. In the absence of that, such as when there was no vasectomy, the effect of the injection may not last long. I wouldn't be surprised if this is why the method mentioned in the research above requires monthly injections. If true, this does give more hope for regular injections, but still doesn't suggest it's necessarily going to have a lower failure rate than 1%. (And as others have mentioned, regular injections of sperm is likely to have significant ethical barriers hence why the research focuses on isolation specific antigens.) Of course it could be that once the body is "primed" whatever cross there is between the blood testes barrier is enough to induce an immune response, however this calls in to question the reversable claim for the related research. (It could be that the leakage isn't sufficient to result an immune response that was initially induced by the antigen vaccine, but I'm not sure how likely this is.) Now it's possible that this method combined with a vasectomy may have a reduced combined failure rate, but until it's actually developed that's difficult to say. Also even under best case scenario, considering the likely time required for development and to demonstrate such a combined effectiveness it may be 15 years or more before we really know that. Nil Einne (talk) 02:01, 23 June 2015 (UTC)


 * Per Vasectomy: "This situation of repartnering later in life has led to what has been characterised as a boom in vasectomy reversals and regrets in which, although the man was happy with his decision at the time of getting the vasectomy, he subsequently regretted the decision later on in his life. Altered situations including death of a partner, relationship break-down, children starting school or leaving home, death of a child, repartnering and remarriage, increased wealth (which previously factored against having more children), mean that the psychological associations and effects of vasectomy are not only those which immediately follow the vasectomy, but may continue throughout a person's life. It is acknowledged that around 5% of men go on to have a vasectomy reversal, and a much higher portion enquire about or seek a vasectomy reversal but are put off by the high costs of surgery and its interplay with the only moderate to moderately low success rates." -- ToE 22:46, 22 June 2015 (UTC)

windshield sun shade reflection
Some windshield sun shades reflect sunlight in a colourful manner, like the one shown in http://www.amazon.com/Reflective-Vinyl-Shield-Shade-Window/dp/B006U605YE Is this phenomenon due to Structural coloration, Iridescence, Thin-film optics, or other physical property? Thanks! Etan J. Tal(talk) 12:46, 21 June 2015 (UTC)
 * That is iridescence caused by thin film optics. Looie496 (talk) 13:51, 21 June 2015 (UTC)
 * Thank you! Etan J. Tal(talk) 14:57, 21 June 2015 (UTC)

Tubes on a salvage tug
What are they for? How are they used? See a picture here: --YX-1000A (talk) 13:50, 21 June 2015 (UTC)
 * They deflect the prop-wash to blow sediment away from the working area --TrogWoolley (talk) 15:19, 21 June 2015 (UTC)
 * In marine treasure hunting (and possibly in other forms of marine salvage) they are referred to as mailboxes or mailbox blowers. See How Mailbox blowers work? for construction and operation details. -- ToE 16:16, 21 June 2015 (UTC)  Edit: Surprisingly, I've not been able to find them described in any Wikipedia article. -- ToE 16:19, 21 June 2015 (UTC)

Earth compared to the known universe
Suppose the known universe is the size of Earth. How big would our Earth be? The size of a pea? An ink dot? A mite? A speck of stuff on a mite? Anna Frodesiak (talk) 15:13, 21 June 2015 (UTC)
 * Much smaller than any of those! The diameter of the observable universe (OU) is about 8.8 x 1026 metres, and the diameter of the Earth (E) is 12,742 km or 12,742,000 m. If x is "the diameter of the earth relative to an earth-sized universe" then x/E = E/OU, or x = E2/OU, which is about 1.84x10-13 m, or 184 femtometres (fm). For comparison, the Bohr radius - essentially the radius of a Hydrogen atom - is about 52600 fm, or about 285 times as big. Space is big. Really big. AndrewWTaylor (talk) 15:58, 21 June 2015 (UTC)
 * I concur with your calculation and add that 184 fm is about 12 times larger than the 15 fm diameter nucleus of a uranium atom and 120 times larger than the 1.5 fm diameter of a hydrogen nucleus (a single proton). So, smaller than an atom, but larger than an atomic nucleus. -- ToE 16:04, 21 June 2015 (UTC) Edit: Article of interest: Orders of magnitude (length). -- ToE 16:08, 21 June 2015 (UTC)
 * A while back I was thinking about how fast the speed of light is, but then considering how long it takes it to cross the known universe, space is REALLY big. Bubba73 You talkin' to me? 03:21, 22 June 2015 (UTC)


 * In addition,universe is in its initial stage of rapid expansion...[[User:sidsandyy|'' s i  d  s  a  n d y y '']]  — Preceding unsigned comment added by Sidsandyy (talk • contribs) 18:03, 21 June 2015 (UTC)

Holy moly. That is teeny. Sorry to make you do all those calculations. I hope it didn't take long. Space really is big, isn't it. Wow. Thank you, all. Anna Frodesiak (talk) 22:10, 21 June 2015 (UTC)
 * Just a little picky point here. You asked about the "known" universe, but people responded in terms of the observable universe.  I'm not sure that's precisely responsive.  The observable universe is defined in terms of event points that are causally connected with us, which means something about them in principle could be known, but not necessarily that much is known.  --Trovatore (talk) 22:25, 21 June 2015 (UTC)

One more
So, sorry, one more. I just want to explain to some kids how big it all is. The atom thing is tough because they can't understand how small an atom is. If the universe were the sun, would Earth be a speck on a mite then?

You don't have to answer any of this. I just think the kids need some sort of reference they can get their heads around.

Maybe the universe thing is too big. How about our galaxy? If you took a pancake the diameter of Earth, would the sun be a pea? How much space between suns?

Someone once told me the universe is like a basketball court filled to your knees with ordinary sand. Each grain is a galaxy. Each galaxy is like a basketball court filled to your knees with sand. But, the space between the grains of sand is really huge. Does that sound at all right? Anna Frodesiak (talk) 22:19, 21 June 2015 (UTC)
 * The distance to the planets is difficult to describe on any small scale. I only really got a good appreciation of the scale of the solar system when I visited a scale Solar System model in the town where I live. There are several sites which attempt to demonstrate the scale, such as this and this]. Vespine (talk) 00:04, 22 June 2015 (UTC)


 * If the earth were a drop of rainwater, the water molecules would be about the size of basketballs. That's a good visualization. μηδείς (talk) 00:18, 22 June 2015 (UTC)
 * Trying to parse this. In other words, if a drop of rainwater were as big as Earth, water molecules would be about the size of basketballs?  I.e. "if you counted the molecules in a raindrop, and then got that many basketballs, they'd be as big as the world"?  Nyttend (talk) 03:07, 22 June 2015 (UTC)
 * Yes, you are interpreting me correctly. I forget where I read that and it wasn't on line, it was probably in the 1990's. μηδείς (talk) 03:36, 22 June 2015 (UTC)


 * Let's figure it out. Drop (liquid) says that raindrops "typically range from 0.5mm to 4mm, with size distributions quickly decreasing past diameters larger than 2-2.5mm".  So I guess we go with 1mm as a rough estimate.  According to Basketball_(ball), a regulation NBA ball is 25cm in diameter.  According to Earth, the mean radius is 6371 km.  So the diameter of the earth is 12742000m, which makes it around 50,000,000 times bigger than a basketball,  so according to this factoid, an atom ought to be 50,000,000 times smaller than a raindrop, which means about 1/50th of a nanometer...20 picometers (pm)...and referring to one of my favorite Wikipedia pages: Orders_of_magnitude_(length), we find that a hydrogen atom has a RADIUS of 25pm...and therefore a diameter of 50pm.  But that's using 1mm for the size of the raindrop.  If we go with 2.5mm - then it works out exactly right.


 * So, the smallest atoms of all (hydrogen) are roughly the size of a basketball on this scale (assuming the raindrop is a 2.5mm droplet).


 * Water molecules are H2O and the Oxygen atoms are 60pm in radius - or 60cm in diameter in our scale...so a water molecule would be two basketballs somewhat embedded into a ball so big that you could only just barely reach around to pick it up...so, the comparison is quite a bit off unless you're prepared to push the size of a raindrop up to the absolute largest.


 * Handily, this water-droplet-earth comparison turns a radius of 25pm (hydrogen atom) into diameter of 25cm (baseball) - so we can look at tiny objects measured in picometers and get a good feel for their sizes immediately by just swapping pm for cm...nm for 10m, um for 10km.


 * Atomic radii of the elements (data page) shows the "empirical" radius of various atoms in picometers - and we find that an iron atom would be 1.4 meters across...chest-high to most humans in water-droplet-world. The biggest atom that we have data for is Caesium, at 260pm - ten times bigger than hydrogen and about the size of a small car or a large sofa in water-droplet-world units.


 * Now we can have fun...the smallest transistors on a computer chip are around a nanometer - which means that you could probably just about fit one in your garage in water-droplet-world. A typical virus is 20 to 300nanometers - which means it could be anywhere from an office building to a small village! Most plant and animal cells are between 1 and 100 micrometers, which is 10km to 1000km - bigger than Mount Everest...up to about the size of a small country!  And of course, on the same scale, a raindrop is (by definition) the size of the Earth.


 * (As an aside, it's quite amazing to imagine a transistor that is the size of a large garage, made by loosely attaching balls ranging in size from basketball to human-sized.)


 * SteveBaker (talk) 04:18, 22 June 2015 (UTC)


 * The Powers of Ten video nicely illustrates some of this: it gradually zooms out from the human scale to the observable universe, then back in again and down to the subatomic level. AndrewWTaylor (talk) 08:02, 22 June 2015 (UTC)

I'm taking notes here. This is all great stuff!!!! Keep going if you have more. Anna Frodesiak (talk) 08:21, 22 June 2015 (UTC)
 * On the question of the size of the earth relative to the Milky Way, which is 180,000 light-years across at its widest (1.7x1021m): if the Milky Way was earth-sized, the earth would be about 95 nanometres across, which is like a smallish virus (viruses are typically 20-300 nm). AndrewWTaylor (talk) 11:23, 22 June 2015 (UTC)

Okay, I've gone through the whole thing and picked lots to dazzle the kids with. Many thanks to all. Again, great stuff!!!! Anna Frodesiak (talk) 17:34, 23 June 2015 (UTC)