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October 4[edit]

October 6[edit]

October 8[edit]

chem[edit]

how do you find the number of protons neutrons and electrons, in a negative oxygen with atomic mass 16 and atomic number 18? --Thegooduser Life Begins With a Smile :) ๐Ÿ 02:09, 8 October 2019 (UTC)

What is a negative oxygen? โ†Baseball Bugs What's up, Doc? carrotsโ†’ 03:18, 8 October 2019 (UTC)
I am guessing they mean a negatively charged ion, which would mean more electrons than protons. But we need to know exactly how much negative charge to determine how many extra electrons it has. Oxygen has an atomic number 8, not 18, so maybe he refers to an ionized molecule ? Hydrogen peroxide (H2O2) has a total of 18 protons (in other words, the total of the atomic numbers is 18). But the atomic weight of 16 makes no sense, as the atomic weight should be equal or more than the atomic number. For hydrogen peroxide the total atomic weight is about 34, since that's the total of the protons and neutrons (and a tiny bit for electrons). So, I can't make any sense of those figures.
For a single atom with an atomic number of 18, that would be argon, but it has an atomic mass of 36-42, depending on isotope. SinisterLefty (talk) 03:30, 8 October 2019 (UTC)
All isotopes of oxygen always have 8 protons, regardless of their atomic mass number. oxygen-18 has 18 mass, including those 8 protons, the number of neutrons is 18-8=10. The number of electron will the same as the number of protons, plus any negative charge; for instance, 9 for for O- Gem fr (talk) 08:56, 9 October 2019 (UTC)

Lights on the ocean at night[edit]

What are these lights?

When flying in Southeast Asia recently, I saw what looked like lights on the surface of the ocean at night, and I can't figure out what they could be. I saw them over the Java Sea (coordinates about -5, 110) and over the South China Sea (about 20, 114). Are they ships? But if so, why are they so uniform? They're all the same color, the same brightness, and spread fairly uniformly over a certain area, not clustered. In the picture you can see a few, but over the Java Sea I saw what looked like hundreds. โ€”Granger (talk ยท contribs) 11:28, 8 October 2019 (UTC)

They are probably fishing boats with lights used to "attract squid and other sea life", as in this image from NASA. Mikenorton (talk) 11:53, 8 October 2019 (UTC)

2019 Nobel Prize in Physics[edit]

I just read in the Wall Street Journal that the Prize had been awarded to 3 scientists. The article is very vague but it seems that the first one, James Peebles from Princeton, is a theoretician. What is his contribution? Thanks, - AboutFace 22 (talk) 15:07, 8 October 2019 (UTC)

This BBC story goes into more detail. Mikenorton (talk) 15:21, 8 October 2019 (UTC)
(ec) Our Jim Peebles article says he made "major theoretical contributions to primordial nucleosynthesis, dark matter, the cosmic microwave background, and structure formation". However, I'm not sure which of those the prize was for. SinisterLefty (talk) 15:23, 8 October 2019 (UTC)

The Wikipedia's article about him, quoted above, says: "he expressed a preferred reference frame for velocity anywhere in the universe based on Isotropic Cosmic Background Radiation, a departure from previous models." What does it mean? I think the CMB is anisotropic. AboutFace 22 (talk) 17:46, 8 October 2019 (UTC)

See Cosmic_microwave_background#Data_reduction_and_analysis. On the one hand, Lorentz symmetry implies the laws of physics are unaffected by an observer's motion; on the other hand the CMB data implies a rest frame through which the earth moves at 368 ยฑ2 km/s causing the CMB to appear slightly red-shifted in the direction of movement. DroneB (talk) 15:26, 9 October 2019 (UTC)
It's a preferred reference frame in the same way that the walls of the room that you're in present a preferred reference frame (the one where these walls are at rest). It's just convenient for describing the actual Universe that we live in. It does not break and has nothing to do with Lorentz symmetry. --Wrongfilter (talk) 07:27, 10 October 2019 (UTC)

October 9[edit]

Black hole center[edit]

People assume density at black hole center is infinite, Infinity does not exist, so where does the stuff go?--213.205.192.210 (talk) 01:22, 9 October 2019 (UTC)

Who says that infinity doesn't exist ? It certainly exists in a mathematical sense, and may well in a physical sense, too. See singularity. There is a theory that mass can come back out of a white hole, but most are skeptical that they exist in reality. SinisterLefty (talk) 01:44, 9 October 2019 (UTC)
About infinity, it depends on what you mean by "exist". It exists as a concept of boundlessness. But it is not a number. โ†Baseball Bugs What's up, Doc? carrotsโ†’ 03:11, 9 October 2019 (UTC)
mathematics of intervals are such that there is no difference between (โˆ’โˆž,โ€‰+โˆž) interval and (0,1). That is, the former is just as infinite as the latter, you can switch between with a simple variable change; for instance, u=log(t), where t is time starting at big bang, will throw big bang back to infinite as measured in u units of log-time. Not saying this is relevant, just meant to illustrate that if you think there exist some beginning you cannot actually reach, you just imagined infinity actually exist in another set of unit. Gem fr (talk) 10:17, 9 October 2019 (UTC)
No. The former set is clopen, the latter is not, and the image under the logarithm of (0, 1) is (-โˆž, 0), not the whole real line. And this is a bad analogy too because we don't live in "log time". "Infinite" densities can be well-modeled using a Dirac delta function, but we cannot say how physical that really is. The OP is correct to surmise something fishy, but "infinity" is not as unimaginable as they might think.--Jasper Deng (talk) 10:28, 9 October 2019 (UTC)
Both (0, 1) and (-โˆž, -โˆž) ARE open. I did not meant to imply that logarithm was the relevant function to map the former into the latter, just that it could be done (log(x)-log(1-x) would do). Nor that we live in log-time (although if we were, I am not sure we could find out). It is easier to imagine time going on forever, or space never ending, than to imagine some sort of bottomless gravitational pit; I think this is because infinite calls "boundless" to mind, it is harder to imagine some sort of horizon around a well we can easily make a turn around. Gem fr (talk) 12:41, 9 October 2019 (UTC)


Nobody knows where the stuff goes, or what happens to it. We call the centre of a black hole a "singularity" (in both the mathematical and gravitational senses) because the mathematics we currently have seem to indicate that it becomes infinitely small and dense, but we don't necessarily think that's literally true, and accept that we don't (yet) have the theory or mathematics to understand what is really going on. The people who eventually figure it out will undoubtably win Nobel and other prizes. {The poster formerly known as 87.81.230.195} 2.121.161.82 (talk) 06:28, 9 October 2019 (UTC)
Specifically, we don't know without an accepted theory of quantum gravity.--Jasper Deng (talk) 06:39, 9 October 2019 (UTC)
or any other theory, for that matter. So we don't know, period. Gem fr (talk) 10:17, 9 October 2019 (UTC)
Stephen Hawking knew a little about it too.--Jasper Deng (talk) 10:29, 9 October 2019 (UTC)
And I will add that stuff falling into a black hole will never be seen to cross the event horizon. It will appear to approach the speed of light and be red shifted to invisibility. If Hawking radiation is real, then the infalling material will never get to the balck hole event horizon before it evaporates. So there is no reason to worry about the interior of a black hole, as there is nothing there yet. Graeme Bartlett (talk) 11:34, 9 October 2019 (UTC)
That's is not the case to an observer the fall seem to take infinite time. From the falling matter perspective, the time is finite. ืื™ืœืŸ ืฉืžืขื•ื ื™ (talk) 19:22, 13 October 2019 (UTC)

Longest time alone in Space.[edit]

Who holds the record for the longest time in space without another human being in the spaceship? Is it one of the Mercury or Early Russian flights, one of the CM Pilots while the LM was down on the moon or someone else. (I was watching the first episode of the original Twilight Zone and I'm not sure in reality we've ever had someone alone for that long in space (in the episode, I think it was several weeks).Naraht (talk) 03:32, 9 October 2019 (UTC)

According to List_of_spaceflight_records#Longest_solo_flight, Valery Bykovsky hold that record at almost five days. WegianWarrior (talk) 04:07, 9 October 2019 (UTC)

Thx.Naraht (talk) 14:10, 9 October 2019 (UTC)

Notably, Steve Fossett conducted a solo balloon flight around the Earth, in the capsule for 13 days - alone in a flight vessel, traveling around the Earth for a longer duration than any astronaut on an orbital mission. Although he didn't reach the fairly-arbitrary altitude that many organizations claim as the "boundary" of outer space, his craft and his missions were historic and record-setting. Nimur (talk) 14:44, 9 October 2019 (UTC)
The figure used as the boundary of outer space may be arbitrary, but any altitude where travel by balloon is possible is clearly not in space. --04:28, 10 October 2019 (UTC) โ€” Preceding unsigned comment added by 76.69.116.4 (talk)
That would depend on how you define space. If it's by an absence of a detectable atmosphere, then I agree. But there could be other measures, like the percentage of UV light that's blocked, where virtually none would be blocked at that height. SinisterLefty (talk) 05:12, 10 October 2019 (UTC)
If you think someone defines space that way, I say "[citation needed]". --76.69.116.4 (talk) 07:15, 10 October 2019 (UTC)
It's where the sky turns black and a jet engine won't work anymore. โ†Baseball Bugs What's up, Doc? carrotsโ†’ 09:36, 10 October 2019 (UTC)
See Kรกrmรกn line for sourced definitions. PrimeHunter (talk) 12:29, 10 October 2019 (UTC)

Global radiation budget - the numbers don't add up?[edit]

I'm referring to a diagram in Outgoing longwave radiation. According to the nice diagram, Earth receives 235 W/m^2 from the sun, and emits back (195+40)=235W/m^2. Thanos would say "Perfectly balanced... as all things should be." Evidently this can not be true since the warming already occurs and is easily measured. What gives? ืื™ืœืŸ ืฉืžืขื•ื ื™ (talk) 06:30, 9 October 2019 (UTC)

The surface of Earth is constantly being warmed by the hot interior. Dbfirs 06:35, 9 October 2019 (UTC)
In that case it should have been warming forever. I mean even if all there was no sun to warm Earth up, it would have been (452-235)W/m^2 balance. That doesn't work either. ืื™ืœืŸ ืฉืžืขื•ื ื™ (talk) 07:53, 9 October 2019 (UTC)
Geothermal heat only accounts for about 0.09 W/m2, according to Earth's internal heat budget. Heating the top 200 meters of the oceans by 0.02 K per year takes about 0.4 W/m2, which is much more than the geothermal heat, but still low enough to disappear in the rounding of that 235 W/m2 ingoing and outgoing radiation. PiusImpavidus (talk) 09:00, 9 October 2019 (UTC)

The warming is on average about 1 Watt per square meter. It's small enough to get lost in rounding errors on a simplified diagram. Someguy1221 (talk) 09:59, 9 October 2019 (UTC)

OK, makes sense. I suggest, though, that because of the importance of the issue, the diagram must present this 1 W/m^2, either substructing from the output or increasing the input. ืื™ืœืŸ ืฉืžืขื•ื ื™ (talk) 11:18, 9 October 2019 (UTC)
I copy this question+answers to Talk:Outgoing_longwave_radiation#Global_radiation_budget_-_the_numbers_don't_add_up?. I suggest we'll discuss modifying the diagram there. I do not know the rules here about transferring discussions so I will not delete it from here. ืื™ืœืŸ ืฉืžืขื•ื ื™ (talk) 11:21, 9 October 2019 (UTC)
The question has been answered. See bullet points #2 and #5 of Wikipedia:Reference_desk/Guidelines#What_the_reference_desk_is_not. TigraanClick here to contact me 11:23, 10 October 2019 (UTC)
1)warming is not easily measured. Humans just started studying the stuff less that half a century ago, argo floats started less than 20 years ago, satellites started not long before, etc. Lots of this stuff is still just estimates, produced by models (that is, NOT data). You'll find in Earth's energy budget another estimates, were the values are actually close to 240 W/mยฒ, and a 0.6 W/mยฒ imbalance. Both lacks accuracy and precision, if these were given, there would be surprises...
2)Actually, there is just no reason why the thing would perfectly balance. Each point of the Earth is always out of balance, gaining energy by day/summer, losing it by night/winter. There are, for sure, some balancing mechanisms, but not some perfect control.
3)even if it were a perfectly balanced energy budget, some "warming" or cooling can be experienced. This just require some energy moving from a reservoir to another with a different Heat capacity. For that matter, and for instance, heat capacity of water (ocean) is 4,184 J/K/kg, while Nitrogen's (atmosphere) is only 736 J/K/kg (that is, air temperature will rise >5x more than ocean temperature will fall, if energy is transferred from the latter to the former; and vice versa). Also, water turning to ice will release heat with no local change of temperature, but the released heat could find its way elsewhere where it will rise temperature.
4)you can have the same budget with very different average temperatures, because radiated power is ~T4. For the same budget, the average temperature will rise if the range of temperatures gets smaller, and lower if the range broaden.
(Bottom line: temperature is an awful metrics of warming, and average temperature an even worse, if possible. This is one of the very first thing you learn in thermodynamics).
5)the balance numbers say absolutely nothing about the temperature. For instance, Venus as so great an albedo that the energy that enter the Venus thermal system is less than 235 W/mยฒ -- and so is the energy getting out -- (not sure of the value, can be calculated from relative solar constant and albedo of Earth and Venus), but it still has far greater surface temperature
all in all, you do need a positive imbalance to increase the energy inside the system, but whether this will result in a temperature rise is quite different. And, symmetrically, you can very well experience temperature rise while energy is balanced. Foehn wind is an interesting example of air actually losing energy, but increasing temperature.
Gem fr (talk) 12:02, 9 October 2019 (UTC)


The source for that diagram, which is originally a NASA science summary poster, further cites Earth's Global Energy Budget (2008), which gives detailed analysis and summarizes the NASA CERES project to aggregate source-data from ground- and satellite- measurements.
Readers who are concerned with the data beyond the decimal-places probably need to go a little further than the summary-poster, which is essentially just an informative and educational cartoon for consumption by children. The really authoritative data and analysis of Earth's energy balance will be found published in scientific literature; and while there is room for a little bit of scientific disagreement and/or uncertainty, the numbers in most analyses do actually add up to a net warming effect - otherwise, responsible scientists wouldn't be so confident in their statements that our planet is presently experiencing a warming trend. The exact details are complicated - where the energy comes from and where it goes - but when we reduce it to a single net incident power figure, that value is positive - and while the value superficially appears to be quite small, it is still larger than the uncertainty, and also larger than a negligible quantity - so it is manifesting as as a true effect on our climate.
Nimur (talk) 14:59, 9 October 2019 (UTC)
In science when you have 2 legit measurement of something, say 235 and 240, then the uncertainty cannot be less than their difference, that is, 5, no matter what each source claim. And, uncertainty add up even when you subtract to get a net. That is, the uncertainty on net incident power is no less that 10. Which is far more than the claimed 0.6 (meaning, this could actually be anywhere between -9.4 and +10.6. Since it is highly implausible that the real value is so far off 0, it just mean we don't know, and just should tell that). Now if the 235 figure is NOT legit anymore, which could very well be, it should just be erased from wikipedia. I would also be very concerned if the claimed uncertainty for the 235 figure was lower than 5: unless some drastic improvement in uncertainty estimates is documented, there is no reason why the new figure is as accurate as it claims to be. Gem fr (talk) 15:30, 9 October 2019 (UTC)
I'm not really here to quibble over which digit is correct.
My point is pretty simple: interested readers who care about scientific accuracy should be consulting the published literature. Wikipedia, as an encyclopedia, is not a good place for this level of detail - especially not when it comes to very precise and accurate quantitative factual data. What we can and should be doing here is to point our readers to good resources - references - like the specific scientific source for the diagram at issue in our OP's question, or to recent publications Bulletin of the American Meteorological Society or Geophysical Research Letters. Those sources are updated frequently - e.g., if you care about the most accurate numbers known to the scientific community and vetted by the peer-reviewed professional staff, as of this week, then pop over to one of those publications. They literally have the latest energy-budget numbers, and they cover the academic debate over the details - as of this week.
There are just too many complicated details for the volunteer editors of our articles to curate, nor even to perfectly remove all the stale or outright-wrong data. We do our best, but this kind of work is a full-time endeavor, and that's why professional publications exist. Our volunteers can't reasonably sift through volumes of detailed data or cull the stale data from millions of articles or fact-check a million changes a day. We are volunteers. We keep the egregious errors out, and we try to make sure the information is accessible to a wide audience. What we have is a bunch of mostly-good articles that provide broad-brush-strokes summary information. If you're the kind of person who needs to know numbers, this encyclopedia isn't the right format.
Those who cannot be bothered to expend the effort (or cost) to find and use the professional publications are just going to have to settle for "free"-quality facts. Categorically, that is going to mean less clarity, less quality, and less timeliness in the delivery of the current state of knowledge. As a case in point, the reader who stumbles through our article won't know if the net energy flux is -9.4 watts, +10.6 watts, or negative a-thousand wibbly-watts because it has been recently-vandalized. There isn't a full-time professional editorial staff to provide peer review here. That's just how it is.
So use your brain, be paranoid about the sources of your information, and be prepared to justify any data that you present. Take my advice on this point: it's waaaaaaay not useful to quote ten significant digits when we talk about climate. It is useful to quote a methodology and a reliable source.
Observe: "NASA scientists accurately computed the global energy budget by analyzing satellite data, and here is some of their work: the CERES instrument on the Terra satellite mission. These scientists have rigorously studied the data in detail, and they concluded - along with most other scientists - that Earth is warming and humans are causing this climate change, and we need to get our pollution under control." The decimal digits don't really even matter.
Nimur (talk) 15:48, 9 October 2019 (UTC)
Actually, there is noting to curate about this series of article, just like pretty much all politically touchy stuff, it is completely overrun by activists claiming to be scientists holding the truth: "we need to get our pollution under control", while pretty obvious, is just NOT science (see, I am paranoid enough ;-) ). Now, here is not the place to make or complain about science, we take things as they are, no matter how full of crap, so Wikipedia will be fine in, like, 3 decades, when some science will actually have been done (it just began). Gem fr (talk) 17:28, 9 October 2019 (UTC)
I'll just pop in here to note that you make a flawed assumption to begin with - that the uncertainty in the difference between two values even has to bear a relation to the uncertainty in the values themselves. You ignore the possibility that there is an entirely separate method of measuring the difference itself.[1] Someguy1221 (talk) 19:05, 9 October 2019 (UTC)
Ye, this is the kind of stuff that is highly damaging to climate science. Earth albedo is about 0.30; 1 is worth ~340 W/mยฒ, so 0.001 albedo 0.34 W/mยฒ. If albedo were just the only thing with uncertainty (and is it not, among the hundreds of parameters of Hansen's model), you would need to know it precisely at ~0.0004 precision to get to the claimed O.15 W/mยฒ. Just check yourself NASA data (as good as possible, but still not without uncertainty data): [2] ... And that, even with disregarding the fact that climate is chaotic, that is, uncertainty exponentially increases with iterations (that is, a 0.001 W/mยฒ uncertainty grows not to 0.002 then 0.003, but to 0.01 then 0.1 W/mยฒ, and keep growing until it all turn to nonsense. aka butterfly effect). You have to have good pal reviewer to get away with this, and he does. And of course, you did not even noticed the prediction of the paper failed, despite being quite weak. And somehow the line of reasoning "A=>B, B, so A" doesn't seem strange to you. You probably forgot Feynman's warning "Science is the belief in the ignorance of experts". Gem fr (talk) 21:35, 9 October 2019 (UTC)
Are the world's glaciers melting? โ†Baseball Bugs What's up, Doc? carrotsโ†’ 21:47, 9 October 2019 (UTC)
Has the climate experienced flat zero natural change in half a century for the first time in history? Have a bunch of geniuses discovered a magic statistical bullet to assess this and to predict the future of a chaotic system, shitting on Edward Lorenz legacy and pretending he did not warned them, with no one applying in all other trades this sure recipe for so fabulous wealth it would make Larry Ellison's ridiculous, without getting three Nobel prize (chemistry, physics, Medicine) and a Fields medal in the process?Gem fr (talk) 09:42, 10 October 2019 (UTC)
I don't see anything in the Ed Norton article about glaciers. โ†Baseball Bugs What's up, Doc? carrotsโ†’ 10:20, 10 October 2019 (UTC)

October 10[edit]

When is the very last molecule of coffee cleared from the body?[edit]

Popular sources on sleep say that caffeine has a half-life of 6 hours. So my cousin read this and cheekily pointed out that this would imply traces of caffeine will still be in our bodies millions of years from now. I have tried to find some serious answer to this, but most people just talk about when the effect of coffee wears off. So, according to this paper, "caffeine's elimination half-life may range between 1.5 and 9.5 hours, while the total plasma clearance rate for caffeine is estimated to be 0.078 L/h/kg". Based on this, if I drink one cup of coffee now, when would the very last molecule of caffeine be cleared from my body? Vesal (talk) 11:58, 10 October 2019 (UTC)

Apparently you're talking specifically about Caffeine rather than coffee, which has a significant amount of water in it. What's unclear to me is whether a caffeine molecule remains intact or whether it is broken down by digestion. I don't see that in the article. โ†Baseball Bugs What's up, Doc? carrotsโ†’ 12:30, 10 October 2019 (UTC)
Almost 100% of the caffeine makes it into your circulation in tact. This is seen in the bioavailability listed in our article. Someguy1221 (talk) 12:39, 10 October 2019 (UTC)
Yes, but a small portion of the caffeine doesn't make it inside tactfully, but rather rudely, in the form of a coffee enema. SinisterLefty (talk) 02:03, 12 October 2019 (UTC)
(edit conflict) If we make the probably naive assumption that caffeine's elimination follows a simple exponential decay, and assume that our subject has consumed a single cup of coffee containing 95mg of the good stuff, then from the molar mass of the molecule and avogadro's number, we can conclude that after 68 half lives, there is only a single molecule expected to remain. Again, assuming simple exponential decay, this one molecule has a 50% chance of still being around after one half life, ad infinitum, but once it's gone it's gone. Someguy1221 (talk) 12:33, 10 October 2019 (UTC)
Wow. 68 half lives of c.6 hours is a seriously long time. So why is it that caffeine addicts feel the need for more in massively less than one half life? --Dweller (talk) Become old fashioned! 12:49, 10 October 2019 (UTC)
Typically one cup of coffee gives you a plasma concentration of caffeine of about 4uM. From rodent studies, by 1uM you're already down to undetectable effects on brain activity. It also matters which type of brain activity you're focused on. Caffeine has a half life of typically four hours in a rat, but some effects of caffeine are already gone in less than two after a dose of caffeine. See [3] for example. Someguy1221 (talk) 13:23, 10 October 2019 (UTC)
{{ec}} Is there some threshhold of effect? (ec: I see Someguy1221 addresses this). If one thrives on having the effect of the caffeine-level gotten after a single cup, after ca. 6 hours, you're already down by half and need a booster shot. And even after 1 hour, you're already down from where you started. I'm not sure which of our steady state articles is relevant to pharmacology and drug-dosing. And this is all assuming there is no lag after ingestion. If the caffeine level were to gradually rise or have a delayed effect, the 10 minutes after the first cup "I don't feel more awake, better drink another". Which reminds me, it's been 10 minutes since my last cuppa... DMacks (talk) 13:25, 10 October 2019 (UTC)
I'm assuming in addition to the matter of threshold, there is likely also a degree of short term desensitization. Someguy1221 (talk) 13:36, 10 October 2019 (UTC)
Caffeine#Dependence and withdrawal mentions tolerance and the subarticle caffeine dependence discusses the physiological basis of it in more detail. DMacks (talk) 13:46, 10 October 2019 (UTC)
Atoms and molecules are incredibly tiny. For a fun illustration, to a zeroth-order approximation a human head contains 456000000000000000000000000 atoms (4.56ร—1026). 100 mg of caffeine, very roughly an average dose, consists of around 310120000000000000000 molecules (3.1012ร—1020). Way before you get down to a few molecules of caffeine, you're going to lose any effect. The molecules might not even be in your brain, which they need to be to have any psychoactive effect. Your body contains random amounts of lots of things, but mostly in too low an amount to have any real effect. --47.146.63.87 (talk) 23:07, 10 October 2019 (UTC)
This thread is why I still read Reference Desk. It quantifies the unquantifiable and unscrews the inscrutable.Edison (talk) 23:52, 11 October 2019 (UTC)
Also, it's about coffee! --Stephan Schulz (talk) 00:09, 12 October 2019 (UTC)

October 11[edit]

October 12[edit]

Hi. I have a question and have already searched for the answer, so I think this is the place to ask. I was reading Effect of spaceflight on the human body. I find the topic interesting in itself, but I thought something might be missing? I'm not sure where to look or if research on this topic exists, but I was wondering how spaceflight might affect the Menstrual cycle? Clovermoss (talk) 20:01, 11 October 2019 (UTC)

When in doubt, consult DTIC (Defense Technical Information Center) and/or NTRS (NASA Technical Report Server)!
NTRS has over 100 scientific articles and publications on the broad topic of female astronaut health in both normal and abnormal conditions. Here is a recent conference presentation:
.... which was a conference presentation by several aerospace medical doctors, including astronaut/flight-surgeon Serena Auรฑรณn-Chancellor, who flew on ISS during Expedition 56/57. Her work was also recently published in the journal Nature: Limitations in predicting the space radiation health risk for exploration astronauts (2018).
Here is a 2015 news summary from an NPR interview with some of the very same astronaut-scientist-doctors: What Happens When You Get Your Period In Space?
And if you search the NTRS database, you can input specific keywords including "women's health", "reproductive health", "menstruation", or any other keyword.
There is a lot of research on both normal and non-normal medical considerations for female astronauts, including the effects of (and on) their reproductive health.
A great starter-book for readers interested in aerospace health at large is Introduction to Aviation Physiology, which is decidedly gender-neutral in its coverage - but if you're not already aware of the basics, that's a good book to get oriented with the terminology and the concerns, before you dive deep into specialization topics.
Nimur (talk) 21:25, 11 October 2019 (UTC)
Thank you so much Nimur! This is exactly what I was looking for. Clovermoss (talk) 22:36, 11 October 2019 (UTC)

Static vs. kinetic friction[edit]

In this problem [4], the truck would experience ฮผk if its wheels are jammed and the truck slides down the slope. But how would it experience ฮผs, when static friction only acts on a non-moving object or allows wheels to roll without loss of energy? 104.162.197.70 (talk) 03:32, 12 October 2019 (UTC)

I think you misread the problem. The static and dynamic friction values given are between the load and the bed of the truck, not between the wheels and the slope. SinisterLefty (talk) 03:36, 12 October 2019 (UTC)
The problem assumes the driver applies the brakes very skilfully and the wheels do not skid. The ฮผk value is not used. DroneB (talk) 12:35, 12 October 2019 (UTC)
D'oh! Thank you. 104.162.197.70 (talk) 18:21, 12 October 2019 (UTC)

October 13[edit]

CO2 and drowsiness[edit]

I notice in the Carbon dioxide article under toxicity there is a bit about the effect of elevated levels on people. Seemingly doubling the ambient amount can cause drowsiness in offices. But the current levels are more than double those before the industrial revolution, I was wondering if anyone has done a study of what people's performance on mental tests would be like at pre-industrial levels compared to nowadays? I don't suppose the effect would be large but it is worrying if people are just a bit stupider nowadays because of it. Dmcq (talk) 13:03, 13 October 2019 (UTC)

Are you sure carbon dioxide causes drowsiness ? I associate that more with a lack of oxygen. Of course, both occur as a result of animals or people breathing in a confined space, so it's easy to confuse the two. SinisterLefty (talk) 14:09, 13 October 2019 (UTC)
Ventilation is key here. Offices (being inside buildings) do not have the same amount of airflow as the outside. --Khajidha (talk) 15:09, 13 October 2019 (UTC)
The Flynn effect suggests that people are becoming less stupid rather than more, at least over the course of the 20th century. Alansplodge (talk) 22:16, 13 October 2019 (UTC)
Small correction: the current levels (410) are less than double the pre-industrial levels (280*2 = 560). As far as I'm aware, the effects only start happening at quite high CO2 concentration that occur only in unventilated spaces. I assume that globally, ventilation is still improving so if there is a noticeable effect, we might be getting smarter (still). Femke Nijsse (talk) 12:54, 14 October 2019 (UTC)
Yes I looked at a graph and I see it started in the last ice age at 180, and seemingly it can go up to 280 in between ice ages. Thanks for pointing that out. According to the citations in the article the CO2 level in offices is quite typically higher that the 560 you say and levels of 1500 can be reached in meetings so everyone is yawning. It is a bit sad that people question the article, the citations are there. Though I'm happy to be corrected or the article fixed. I hardly think the Flynn effect is caused by increased CO2. Dmcq (talk) 19:43, 14 October 2019 (UTC)

Why does urine drop from the penis after the brain believes it has done urinating?[edit]

Why does urine drop from the penis after the brain believes it has done urinating?

Wikipedia has an article on post-void dribbling, which is one of many types of incontinence.--Shantavira|feed me 17:02, 13 October 2019 (UTC)
With a risk of making fun of myself, I never understood why other men have this problem. A firm squeeze from base to tip deals with this perfectly. Than again, it may have something with personal anatomy. ืื™ืœืŸ ืฉืžืขื•ื ื™ (talk) 17:53, 13 October 2019 (UTC)
But remember: if you shake it twice, you're playing with it. {The poster formerly known as 87.81.230.195} 2.121.161.82 (talk) 17:21, 14 October 2019 (UTC)

Physics Question- Is it harder to hit home runs with a softball or baseball?[edit]

I have heard that it is harder to hit a home run with a softball than a baseball. This is supposedly due to the fact that harder pitches contribute to baseball's exit velocity, whereas a softball's exit velocity is much more dependent on the hitter. Is this true? 2001:5B0:2965:BF58:8087:99F:B81F:27F3 (talk) 17:29, 13 October 2019 (UTC)

A baseball itself is harder than a softball, hence it can fly farther when hit squarely, because more energy transfers to the ball. A well-hit golf ball can fly even farther than a baseball. There are still plenty of home runs in softball, as the fences are generally much closer. If you google "energy transfer to a batted ball", there are plenty of entries.[5] โ†Baseball Bugs What's up, Doc? carrotsโ†’ 18:53, 13 October 2019 (UTC)
On the other hand, here's a story about a guy who allegedly hit a softball 576 feet,[6] although it looks like he's using a metal bat. โ†Baseball Bugs What's up, Doc? carrotsโ†’ 19:03, 13 October 2019 (UTC)
BTW, the record for a hit baseball is 634 feet (193 m). [7] Alansplodge (talk) 22:09, 13 October 2019 (UTC)
I would be skeptical of that claim. โ†Baseball Bugs What's up, Doc? carrotsโ†’ 03:07, 14 October 2019 (UTC)
It's accepted by Guinness World Records, but whether that's a reliable source or not I don't know. They usually make some effort to verify their claims. Alansplodge (talk) 13:08, 14 October 2019 (UTC)
There's an article called Long drive which is about hitting golf balls. It sees even the average amateur can hit a golf ball nearly 700 feet, which is well beyond the longest record baseball or softball distance. The dimples on the golf ball also aid in that kind of effort, reducing wind resistance. โ†Baseball Bugs What's up, Doc? carrotsโ†’ 19:07, 13 October 2019 (UTC)
Relevant links are Golf_ball#Aerodynamics and drag crisis (though the latter article is not in a really good shape). TigraanClick here to contact me 10:47, 14 October 2019 (UTC)
Which is harder Baseball or Softball? suggests that the difficulty lies in the pitcher being a lot closer in a softball game, giving less reaction time and the ball arriving at a different angle. I confess to knowing next to nothing about either sport. Alansplodge (talk) 13:03, 14 October 2019 (UTC)
There's a significant difference between slow pitch and fast pitch. Slow pitch deliveries come in on a fairly high arc and the batter has to supply all the power. Fast pitch is more like baseball, and it does require a quick reaction time because in both versions the pitcher is only 46 feet away. Furthermore, because all softball deliveries are underhand, a fast pitch pitcher can make the ball come up (a "rise") and that can be very difficult to hit solidly. โ†Baseball Bugs What's up, Doc? carrotsโ†’ 16:42, 14 October 2019 (UTC)

October 14[edit]

pH - actually math question.[edit]

So the pH scale is logarithmic, every unit in 1 is a power in 10. So from pH 7 to 6 is 10x more acidic 7 to 8 is 10x less acidic. How do you calculate what would be twice something acidic/basic? So ph 7, what's 2x acidic and basic, and how do you derive that? Thanks. 67.175.224.138 (talk) 00:55, 14 October 2019 (UTC).

pH = -log10[H+] , where [] indicates concentration. pH 7 implies [H+] = 10-7, so you can double that and plug it into the formula. Someguy1221 (talk) 02:01, 14 October 2019 (UTC)
log(10^7) = 7, and 2 log(10^7) = 14, so doubling it didn't help. 67.175.224.138 (talk) 02:33, 14 October 2019 (UTC).
You know what, I think I got it. -log( 2 * 10^-7) = 6.698...
And ............................ -log(.5 * 10^-7) = 7.301... 67.175.224.138 (talk) 02:42, 14 October 2019 (UTC).
Yep, log(2) = 0.301..., and thus the rule of thumb that a 3 dB change represents a doubling or halving. -- ToE 14:51, 14 October 2019 (UTC)
It's worth noting that while a 0.3 change in pH does represent a doubling or halving of concentration, and that matches your definition of being twice as acidic/basic, I don't know if "Solution A is twice as acidic as solution B." is something a chemist would ever say. (Can anyone here comment on that?) A 3 dB change in sound level represents a doubling or halving power, but it takes a 6 dB change for a doubling or halving of the rms sound pressure, and it is commonly held that it takes a 10 dB change for a double or halving of the perceived volume or loudness, a subjective perception.[8] If chemists do speak of one solution as being so many times more or less acidic than the an other, then perhaps they are doing so based on something other than the direct ratio of hydrogen ion activities. -- ToE 17:06, 14 October 2019 (UTC)
"Half as acidic" is either ambiguous or not used that way. If I take a 1 M HCl solution and dilute it 50%, I could say my solution is half as acidic (the solution is less-strong an acid). Dilute 1 M HCl by a factor of ten, and it's a tenth as acidic (raising one pH unit); by a factor of 100 raises it 2 pH units. But I don't think anybody would say that going from pH 6 to pH 8 is becoming "one hundredth as acidic" even though [H+] is reduced by a factor of 100...it's not a "weaker acidic solution", but is basic instead (even though it could act as an acid in the presence of an even stronger base). DMacks (talk) 17:22, 14 October 2019 (UTC)
Well when you add water to acid, that doesn't change the amount of H+ ions already in there, right, so the pH stays the same? Diluting it changes the pH? 67.175.224.138 (talk) 19:15, 14 October 2019 (UTC).

Drug testing.[edit]

Since drug testing for urine, can determine whether someone does weed, cocaine, or various drugs, then can urine testing also determine whether someone ate food like broccoli, spinach, blueberries, or cherries? And don't you have to worry about false positives and false negatives, i.e., blueberries contains anthocyanins, but evidence of anthocyanins in urine doesn't conclude you ate blueberries. Can drug testing also tell what kind of meat you eat, like between beef, pork, and chicken? Thanks. โ€” Preceding unsigned comment added by 67.175.224.138 (talk) 00:58, 14 October 2019 (UTC)

They likely could develop tests for specific foods, based on what metabolites and waste products make it to the urine, but I doubt if anyone has done so, as there isn't much need for it. SinisterLefty (talk) 01:45, 14 October 2019 (UTC)

Color theory.[edit]

Has anyone attempted to combine the RGB theory with wavelength? Like green light for example, is rgb(0, 255, 0) and 555 nanometer in wavelength, but that doesn't necessarily convert? Then, take pink for example. Pink isn't on the electromagnetic spectrum (the Roy G. Biv). So how would 1 convert RGB(255, 192, 203) (pink) and find it on the electromagnetic spectrum? 67.175.224.138 (talk) 03:15, 14 October 2019 (UTC).

Pink is some color at all visible frequencies (white) plus more color at the red frequency. The RGB color map doesn't always map to one frequency, because many colors are a combo of frequencies, which our brains then "see" as one color. So, only the colors of the rainbow have single frequencies. Now, you could come up with an approximation of each color by using variable amounts of 3 frequencies, for red, green, and blue. In your example, that would be the max amount of red frequency, 192/255 as much green frequency, and 203/255 as much blue frequency. (Our perceptions of light aren't linear, so you might need to adjust the amounts.) But, of course, that's just one pink, and there are many different pinks. It might be better to do the reverse, and define colors by something universal in nature, like the color of sodium in the flame test, using whatever visible frequencies that produces as the definition of that color. SinisterLefty (talk) 03:27, 14 October 2019 (UTC)
Well, the article on Pink doesn't talk about it in the eye-perception level, but the Wikipedia article on purple near the top has something on when it hits rods and cones in our eye, the L-cone and S-cone for red and blue, and how purple light differs from violet. But I figured pink was just a combination mix of red and white light. But the red and white light cannot come from the same source? 67.175.224.138 (talk) 03:47, 14 October 2019 (UTC).
There are single pink lights, like this one: [9]. The colors can also be tweaked by coating the glass with something to block portions of certain colors. Of course, this is less efficient in that those blocked colors are turned into heat and waste electricity. One of the trickiest things to control is the color of lasers, as they only come in a few frequencies, and you can't alter the color by blocking certain portions of the spectrum with a coating, because they only have a single frequency to begin with. They use techniques to double, triple, or quadruple the frequency to increase the number of colors available. SinisterLefty (talk) 03:59, 14 October 2019 (UTC)
There actually are tunable lasers. DMacks (talk) 06:07, 14 October 2019 (UTC)
Interesting, but a lot more complex than just putting a colored coating on a white light bulb. SinisterLefty (talk) 06:14, 14 October 2019 (UTC)
Trying to represent a RGB colour value by a single wavelength is like trying to represent a three-note chord by a single note. Gandalf61 (talk) 08:46, 14 October 2019 (UTC)

Spectral-lines-continuous.svg This is as near an imitation of the visible range of spectral colors as your display device receiving RGB signals can achieve. Reading the articles Color vision, Color theory and the following links will help. We seldom encounter true Spectral colors that comprise a single wavelength within the visible range 740 nm (deep violet) to 380 nm (deep red). The human eye+brain is incapable of measuring wavelength but is evolved to obtain a perception of color when it receives any mixture of light wavelengths that differs from the case of neutral color Grey or White. Cone cells of the eye retina have 3 different spectral sensitivities, thus color perception is 3-dimensional. Two theories describe the perception process: trichromatic theory and the opponent process theory. Both theories are accepted as valid and the trichromatic theory is the basis for the Additive color or RGB color model that is successful in color CRT, LCD and projection displays. For digital representation in computer graphics files and displays and in HTML coding for web pages the achievable colors are expressed as an RGB triplet (r,g,b) that in a byte-oriented system allows 224=16,777,216 colors from (0,0,0)=black to (255,255,255)=white. However it is impossible for an RGB display to give a genuine spectral color because such colors lie beyond the Gamut achievable by practical RGB Primary colors. DroneB (talk) 11:16, 14 October 2019 (UTC)

What type of owl is this?[edit]

What type of owl?

It is probably the most common type around here. Bubba73 You talkin' to me? 05:35, 14 October 2019 (UTC)

Is it not a Great horned owl? โ†Baseball Bugs What's up, Doc? carrotsโ†’ 05:47, 14 October 2019 (UTC)
Yes, it must be. Thanks.Bubba73 You talkin' to me? 05:49, 14 October 2019 (UTC)

Sharp drop of agricultural carbon dioxide emissions since 2012/13[edit]

If this data is correct, can anybody here explain what exactly caused that sharp drop from 150 to 31 Mt in 2012/13?--Hildeoc (talk) 09:06, 14 October 2019 (UTC)

The data is not correct. If you select the option all greenhouse gases instead of only CO2, there is no drop, and methane doesn't show weird behaviour either. As CO
2
and methane are the main greenhouse gases for agriculture, this is internally inconsistent. I've sent the some feedback to the website, so hopefully they will correct it soon. Femke Nijsse (talk) 12:45, 14 October 2019 (UTC)
@Femkemilene: Thank you very, very much โ€“ especially for taking the courage and trouble to notify the publisher. That's great! (Would you mind informing me about the outcome? I'd be very interested in their response.) All the best--Hildeoc (talk) 19:07, 14 October 2019 (UTC)
I'll keep you posted if I hear anything back from the publisher. Femke Nijsse (talk) 20:38, 14 October 2019 (UTC)
For crying out loud, Femkemilene. It's wrong of course but it's just missing co2 data for those years.--TMCk (talk) 22:58, 14 October 2019 (UTC)

is escape velocity real?[edit]

Does escape velocity really exist? What if a rocket maintains speed of 80 km/h till it escapes the gravity well?
I mean, i can understand an object without any mechanism to increase or maintain the speed will require a "escape velocity". But what if the rocket has plenty of fuel, and time? What if the person in charge of rocket says "doesnt matter how much fuel we burn, or time we waste; i will not increase the speed above 80km/h" In that case, would the rocket escape to space? And if no, why not, and what would happen? โ€”usernamekiran(talk) 12:09, 14 October 2019 (UTC)

Have you read Escape velocity? โ†Baseball Bugs What's up, Doc? carrotsโ†’ 12:32, 14 October 2019 (UTC)
@Baseball Bugs: hi. Even though not at all helpful, your attempts to help others is commendable. Yes, I had skimmed the article before posting the question here. The second paragraph states:
Escape velocity is only required to send a ballistic object on a trajectory that will allow the object to escape the gravity well of the mass M. A rocket moving out of a gravity well does not actually need to attain escape velocity to escape, but could achieve the same result (escape) at any speed with a suitable mode of propulsion and sufficient propellant to provide the accelerating force on the object to escape.
Which was not much helpful to my query. But on the better side, you didn't call me a troll/vandal this time. Just on side note, one shouldn't be condescending/derogatory on Q/A forums while answering. โ€”usernamekiran(talk) 16:42, 14 October 2019 (UTC)
Usernamekiran, this kind of rudeness to Baseball-Bugs is not appropriate or attractive. The quotation from the article appears to me to answer your query precisely, so it was a reasonable reply to ask whether you had looked at the article. I am not sure why you did not understand it thus, but that is something that we could have explored if you had had a less combatative approach. Jmchutchinson (talk) 18:39, 14 October 2019 (UTC)
Actually I think the passage is a bit problematic. It says the rocket "does not actually need to attain escape velocity to escape", but it does need to, of course. Otherwise it doesn't "escape" (to "escape" is to become gravitationally unbound to the mass in question).
It's just that the escape velocity keeps dropping, till eventually it is lower than the hypothesized constant speed.
To be fair, the author was probably thinking of the escape velocity as calculated at the point the rocket lifts off, and it's true that the rocket does not need to attain that speed. --Trovatore (talk) 02:26, 15 October 2019 (UTC)
There was no indication that the OP had read the article. I just wondered if the OP had in fact read it, and if so, had found it as confusing as I did. โ†Baseball Bugs What's up, Doc? carrotsโ†’ 21:23, 14 October 2019 (UTC)
By definition of the velocity, if you manage to maintain any positive speed (in an ITRF), you will eventually escape the gravity well. But doing so would consume much more fuel that giving a big boost at the start. In practice that would be impossible because the amount of fuel required is exponential, not linear, in the amount of energy you want to give to the payload. TigraanClick here to contact me 12:38, 14 October 2019 (UTC)
@Tigraan: thanks a lot. My doubt is totally cleared now. See you around Face-smile.svg โ€”usernamekiran(talk) 16:42, 14 October 2019 (UTC)
You may be interested in reading our gravity loss article. -- ToE 17:08, 14 October 2019 (UTC)
You might be interested in our space elevator article. This would allow slow ascent, which would be more efficient because the low speeds wouldn't incur the huge aerodynamic drag of rockets. Then there's a balloon assisted rocket launch, which has a slow ascent phase followed by a rapid one. Or simply launching a rocket from atop a high mountain also has a bit of a benefit in saved fuel. SinisterLefty (talk) 17:17, 14 October 2019 (UTC)
A space elevator is even more efficient because the payload "steals" the planet/moon/etc.'s angular momentum as it ascends, thanks to the Coriolis force. This means the only energy required is that to lift the payload up the elevator. A rocket needs to both lift the payload and accelerate it "sideways" to orbital velocity. --47.146.63.87 (talk) 23:56, 14 October 2019 (UTC)
Escape velocity says:
For a spherically symmetric, massive body such as a star, or planet, the escape velocity for that body, at a given distance, is calculated by the formula[1]
where G is the universal gravitational constant (G โ‰ˆ 6.67ร—10โˆ’11 m3ยทkgโˆ’1ยทsโˆ’2), M the mass of the body to be escaped from, and r the distance from the center of mass of the body to the object.
Solving for r with = 80 km/h and M = mass of Earth gives r = 1.61ร—109 km. After cruising around 2300 years at 80 km/h you can turn off your rocket a little beyond Saturn and escape, if other masses are ignored. PrimeHunter (talk) 21:55, 14 October 2019 (UTC)
Yes. The escape velocity decreases the farther you are from the center of the massive velocity. Anytime your velocity exceeds the escape velocity for that distance, you escape. Bubba73 You talkin' to me? 02:27, 15 October 2019 (UTC)

You may also be interested in reading about the Oberth effect, which goes into detail about why it is more efficient for a chemical rocket to burn at the bottom of a gravity well. This is in the context of a flyby of a celestial object, but the same principles apply. Of course assuming you are literally taking off from the surface of the earth, there is atmosphere to deal with, but you know, in the context of spherical cow rockets... Someguy1221 (talk) 01:42, 15 October 2019 (UTC)

I like to observe this bit of rocket science formed a plot point in the 1963 comedy movie The Mouse on the Moon. In the movie, Prof. Kokintz points out (quite correctly) that because the Americans and Soviets are trying to reach the Moon with conventional rockets, they have to get there in a few days, whereas his own ship, with a more powerful supply of energy, can take its time for the journey. --76.69.116.4 (talk) 03:53, 15 October 2019 (UTC)

References

  1. ^ Khatri, Poudel, Gautam, M.K., P.R., A.K. (2010). Principles of Physics. Kathmandu: Ayam Publication. pp. 170, 171. ISBN 9789937903844.CS1 maint: multiple names: authors list (link)

Slightly salted peanuts for the squirrels[edit]

I throw some bird feed to the birds and also various nuts like filberts to the squirrels. It is all thrown out on a deck of our house. You should have seen the speed the squirrels do away with 2-3 pounds of nuts. I simply could never catch them in the act. I heard long time ago that birds should not be given anything salty and here I am compliant. I do have some supply of peanuts. I tasted them and found them slightly salty. Shall I give the nuts to the squirrels? Thanks AboutFace 22 (talk) 19:56, 14 October 2019 (UTC)

If you consider squirrels to be pests ("rats with bushy tails", as some have said), then you might think it's good enough for them. โ†Baseball Bugs What's up, Doc? carrotsโ†’ 21:22, 14 October 2019 (UTC)
Hard to be sure. Sodium is an essential nutrient, so they do need some. If they aren't getting enough sodium in their diet, a few salted peanuts may actually be helpful. But, if they are already getting too much sodium, from discarded french fries, etc., then the salted peanuts could be harmful. Also, it's possible the squirrels may remove excess salt from the outside of the peanuts, either intentionally or as a result of burying them and digging them back up later. SinisterLefty (talk) 02:52, 15 October 2019 (UTC)

October 15[edit]

Approximately how old is this tree?[edit]

The poem The Marshes of Glynn was written under the tree in the second photo in the article - 141 years ago. It is a live oak, which grows slowly. But could this tree have been a significant tree 140+ years ago?

(When I was young, I was told that the original tree died, and that this was a different one. But I don't have any source for that.) Bubba73 You talkin' to me? 00:31, 15 October 2019 (UTC)

Starke, A. H. (1933). Sidney Lanier: A biographical and critical study. has an earlier photo if that helps, worldcat lists an ebook version [10].—eric 04:26, 15 October 2019 (UTC)

Blood backflow in IV bag[edit]

I came upon a IEEE conference-presentation that sought to design an electronic system to prevent blood backflow in intravenous infusions. I am curious to know of the potentially harmful effects, such a back-flow (restricted to the drip-line or may-be, even to the infusion-bag) might have on a patient, with due references to medical literature. WBGconverse 04:40, 15 October 2019 (UTC)

XY chromosome disorders.[edit]

So, red-green colorblindness affects only males, 8% of males. That is because the gene for colorblindness sits on the X chromosome, and women are XX. Since men are XY, and Y is a lot shorter than X in humans, allows men to be born colorblind. Is the 8% due to the Y chromosome being about 8% as long as the X? And what are some order examples of disorders besides red-green colorblind? My book only lists 1 other and that is hemophilia. It mentions women can be carriers of hemophilia to pass it down to sons, does that mean women can pass down red-green colorblindness to sons too? Thanks. 67.175.224.138 (talk) 04:51, 15 October 2019 (UTC).