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October 4

October 6

October 11

October 12

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)[reply]

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:

Practical Considerations for the Care of Female Astronauts on the International Space Station (2015)

.... which was a conference presentation by several aerospace medical doctors, including astronaut/flight-surgeon Serena Auñón-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)[reply]

Thank you so much Nimur! This is exactly what I was looking for. Clovermoss (talk) 22:36, 11 October 2019 (UTC)[reply]

Static vs. kinetic friction

In this problem [1], the truck would experience μk if its wheels are jammed and the truck slides down the slope. But how would it experience μs, 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)[reply]

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)[reply]

The problem assumes the driver applies the brakes very skilfully and the wheels do not skid. The μ_k value is not used. DroneB (talk) 12:35, 12 October 2019 (UTC)[reply]

D'oh! Thank you. 104.162.197.70 (talk) 18:21, 12 October 2019 (UTC)[reply]

October 13

CO2 and drowsiness

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

I wasn't suggesting that it was caused by CO2, just pointing out that people are apparently not "a bit stupider nowadays". Alansplodge (talk) 18:04, 17 October 2019 (UTC)[reply]

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)[reply]

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. אילן שמעוני (talk) 17:53, 13 October 2019 (UTC)[reply]

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)[reply]

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

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)[reply]

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.[2] ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:53, 13 October 2019 (UTC)[reply]

On the other hand, here's a story about a guy who allegedly hit a softball 576 feet,[3] although it looks like he's using a metal bat. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:03, 13 October 2019 (UTC)[reply]

BTW, the record for a hit baseball is 634 feet (193 m). [4] Alansplodge (talk) 22:09, 13 October 2019 (UTC)[reply]

I would be skeptical of that claim. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:07, 14 October 2019 (UTC)[reply]

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)[reply]

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. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:07, 13 October 2019 (UTC)[reply]

Relevant links are Golf_ball#Aerodynamics and drag crisis (though the latter article is not in a really good shape). Tigraan^{Click here to contact me} 10:47, 14 October 2019 (UTC)[reply]

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)[reply]

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. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:42, 14 October 2019 (UTC)[reply]

October 14

pH - actually math question.

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).[reply]

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)[reply]

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).[reply]

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).[reply]

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)[reply]

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.[5] 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)[reply]

"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)[reply]

I find your language confusing. I am used to strong/weak acid referring to the ease for the acid to release H+, that is, the pKa, not the pH. Gem fr (talk) 11:34, 15 October 2019 (UTC)[reply]

I was careful to include the word/concept of "solution"...the strength of a solution is obviously related to its concentration. You are right about the other idea obviously as well...the intrinsic acidity of the solute that makes the solution acidic (that's why I specified HCl, and specifically chose a strong acid). DMacks (talk) 12:04, 15 October 2019 (UTC)[reply]

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).[reply]

Yes, diluting change the pH (because it reduce the concentration, obviously). The pH will get closer to 7. Gem fr (talk) 11:27, 15 October 2019 (UTC)[reply]

Yup, pH is exactly related to concentration, not the numerical amount. Someguy1221 already said that in the very first reply to the original question. DMacks (talk) 12:04, 15 October 2019 (UTC)[reply]

Drug testing.

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. — Preceding unsigned comment added by 67.175.224.138 (talk) 00:58, 14 October 2019 (UTC)[reply]

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)[reply]

Not all metabolites and not all metabolic pathways are created equally. Testing for alcohol consumption in urine might only give a positive result for the first few hours after consumption, while testing for marijuana might yield a positive result days, or even weeks after use. What's the metabolic half-life of these compounds? What's the limit of detection for the measurement technique (which also won't be the same for all compounds), and how does it compare with the actual expected concentrations in urine? It's not impossible to imagine some things might not be detectable easily at all. Certainly, even in the field of drug testing, there's a bit of a cat and mouse game (especially regarding performance enhancing drugs) between testers and drug designers. Meats certainly have some chemical differences between them, but are largely made of protein, and so their breakdown products may end up being too similar to discern either from each other, or from our own protein breakdown products. --OuroborosCobra (talk) 23:28, 15 October 2019 (UTC)[reply]

What is the method used for determining the metabolites in drug testing? Spectroscopy? 67.175.224.138 (talk) 00:31, 16 October 2019 (UTC).[reply]

It depends. Methods differ depending on the metabolite and what method has the best limits of detection and (if necessary) limits of quantitation. Note that for some drugs, positive/negative presence is all that is needed, as they are illegal substances and having them in your system at all is proof of crime. When it comes to other substances, like alcohol, you need a quantitative test that demonstrates whether one is currently intoxicated or not. One challenge right now for marijuana (at least as far as I am aware) is that we don't have a good test for current intoxication, since until recently, the legal status was fairly universally "any amount is illegal," and there was no need for a test for intoxication. Immunoassays are a common method, though possibly not the best for a quantitative result. Chromatography, sometimes combined with mass spectrometry, is another method. This article describes more on current urine testing techniques. --OuroborosCobra (talk) 01:09, 16 October 2019 (UTC)[reply]

Well, my specific question would be the urine testing that takes a few seconds. After giving the nurse my cup of urine, she dips some item in it that has like 8 tubes or so (for each test) and within seconds she records a positive or negative for all of them. Perhaps the positive/negative is a color change? 67.175.224.138 (talk) 01:20, 16 October 2019 (UTC).[reply]

That would be an immunoassay test, most likely. Sometimes that result is determined through a color change, but there are otherways (change in fluorescence, for example). --OuroborosCobra (talk) 18:56, 16 October 2019 (UTC)[reply]

Wow, I've never had seen/used/learned of immunisays and ELISA in any chemistry class, for analytics (did IR, NMR, GC, HPLC, etc.). What class in the biology department deals with immunoassays and ELISAs? Is it a different technique? I mean what would be the closest. 67.175.224.138 (talk) 20:55, 16 October 2019 (UTC).[reply]

We have a urine drug test article-section. DMacks (talk) 03:02, 17 October 2019 (UTC)[reply]

Bah, that doesn't answer my question either, as it mostly lists a list of metabolites that they are able to detect, but not say how. I see the article Urine_test_strip but doesn't seem to cover drugs? 67.175.224.138 (talk) 06:47, 17 October 2019 (UTC).[reply]

Yikes, that's a silly redirect. Why doesn't it point to the same place as urine drug screen, which is more on-target for you? DMacks (talk) 08:52, 17 October 2019 (UTC)[reply]

Here's a ref summarizing (among other things) what can cause incorrect results. I spot-checked the refs for the individual drugs and they often have quite specific technical detail about the individual test (because they are studying the scope and limitations of the test itself). DMacks (talk) 08:59, 17 October 2019 (UTC)[reply]

Color theory.

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).[reply]

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)[reply]

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).[reply]

There are single pink lights, like this one: [6]. 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)[reply]

There actually are tunable lasers. DMacks (talk) 06:07, 14 October 2019 (UTC)[reply]

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)[reply]

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)[reply]

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 380 nm (deep violet) to 740 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.

The example of pink

Pink is very desaturated red. If we were mixing oil colors, stirring a couple of drops of red pigment into a can of white paint would provide pink. However in RGB coding we are adding lights not pigments and the code for pink could be arrived at as follows. Start from a 75% bright grey/white RGB(192,192,192) which allows a 25% headroom for adding color. A fair pink results from filling the headroom with red primary i.e. RGB(255,192,192). Visualize this as drawing a line on the RGB color space triangle from the D65 white point to the red primary corner, and picking the point on the line 25% length from white. The red primary is not far from (but definitely not exactly at) the spectral wavelength ~610 nm so we may think of that as the unreachable end target wavelength of further desaturation. However there is subjective acceptance of a range of pinks and the OP cites from the Wikipedia article RGB(255,192,203). That point is reached similarly except that instead of desaturating by adding only 25% red, the added light is 85.1% red and 14.9% blue. Our vector direction leaving the D65 white point is rotated clockwise slightly and we may imagine it pointing to a deeper, possibly infra- red wavelength 650 nm or more, which is even further beyond the gamut. DroneB (talk) 20:39, 15 October 2019 (UTC)[reply]

What type of owl is this?

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

Is it not a Great horned owl? ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:47, 14 October 2019 (UTC)[reply]

Yes, it must be. Thanks.Bubba73 ^{You talkin' to me?} 05:49, 14 October 2019 (UTC)[reply]

Sharp drop of agricultural carbon dioxide emissions since 2012/13

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)[reply]

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 CO₂ 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)[reply]

@Femkemilene: Thank you very, very much – 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)[reply]

I'll keep you posted if I hear anything back from the publisher. Femke Nijsse (talk) 20:38, 14 October 2019 (UTC)[reply]

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)[reply]

@TracyMcClark: Sorry, but I'm only a layman. What exactly are you referring to?--Hildeoc (talk) 12:42, 15 October 2019 (UTC)[reply]

is escape velocity real?

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? —usernamekiran(talk) 12:09, 14 October 2019 (UTC) [reply]

off-topic, unproductive discussion. Everybody involved got to present their opinions. —usernamekiran(talk) 05:54, 15 October 2019 (UTC)[reply]

The following discussion has been closed. Please do not modify it.

Have you read Escape velocity? ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:32, 14 October 2019 (UTC)[reply]

@Baseball Bugs: hi. Even though not at all helpful, your attempts to help others are 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. —usernamekiran(talk) 16:42, 14 October 2019 (UTC)[reply]

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)[reply]

@Jmchutchinson: Hi. I was not being combative. But honestly speaking I was trying to be uncompromisingly forthright while trying to remain polite. I apologise for not being able to put the original question correctly in words. —usernamekiran(talk) 05:54, 15 October 2019 (UTC)[reply]

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. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:23, 14 October 2019 (UTC)[reply]

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)[reply]

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. Tigraan^{Click here to contact me} 12:38, 14 October 2019 (UTC)[reply]

@Tigraan: thanks a lot. My doubt is totally cleared now. See you around

—usernamekiran(talk) 16:42, 14 October 2019 (UTC)[reply]

You may be interested in reading our gravity loss article. -- ToE 17:08, 14 October 2019 (UTC)[reply]

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)[reply]

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)[reply]

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]

v_{e}={\sqrt {\frac {2GM}{r}}},

where G is the universal gravitational constant (G ≈ 6.67×10⁻¹¹ m³·kg⁻¹·s⁻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

v_{e}

= 80 km/h and M = mass of Earth gives r = 1.61×10⁹ 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)[reply]

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)[reply]

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)[reply]

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)[reply]

Thank you very much folks. Your comments have been very much intriguing, and helpful. It is appreciated a lot —usernamekiran(talk) 05:54, 15 October 2019 (UTC)[reply]

References

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

Slightly salted peanuts for the squirrels

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)[reply]

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. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:22, 14 October 2019 (UTC)[reply]

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)[reply]

Thank you, Sinister. This is a delicate question for me. Obsessed with helping the nature to survive, don't want to do any harm. Of course birds and mammals are different phyla, squirrels are more likely as us and perhaps they can tolerate some sodium chloride. AboutFace 22 (talk) 14:23, 15 October 2019 (UTC)[reply]

Hi AboutFace 22. According to sources, there are three problems with feeding peanuts to squirrels. Peanuts in general harm squirrels by filling them with a less nutritious food than their regular diet, leaving them less room for the food they really need. In addition, both salted peanuts and raw peanuts actively harm squirrel health.

1. Pest control company squirrelcontrol.ca says: "The two main issues with feeding squirrels are filling them up on foods that have little or no nutritional value or foods that are outright dangerous. Peanuts have little nutritional value for squirrels and salt is very bad for squirrels."

2. Pet food store nwseed.com says: "Salted nuts of any kind should never be fed to wild creatures." and "Feeding raw peanuts to squirrels and other animals can have serious consequences. The results can even be fatal. Peanuts when raw contain a trypsin inhibitor, a substance that inhibits or prevents the pancreas from producing trypsin which is an enzyme essential for the absorption of protein by the intestine. The detrimental effects on rodents have been documented since 1917. Thus squirrels fed a steady diet of raw peanuts could easily develop severe malnutrition."

3. Online magazine sciencing.com says: "You should feed a wild squirrel food that aligns with their natural wild squirrel diet [link provided] to avoid making them sick and/or overweight. Too many peanuts along with expired nuts can be dangerous for squirrels to eat. Peanuts for squirrels seems like a no-brainer, but they're actually not super nutritious." 70.67.193.176 (talk) 16:10, 17 October 2019 (UTC)[reply]

October 15

Approximately how old is this tree?

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)[reply]

Starke, A. H. (1933). Sidney Lanier: A biographical and critical study. has an earlier photo if that helps, worldcat lists an ebook version [7].—eric 04:26, 15 October 2019 (UTC)[reply]

Thanks, it is hard to tell. Here is the 133 photo and this is a recent one. Both seem to have three trunks, but (1) the 1933 pne appears taller, compared to the concrete marker. (2) the concrete marker is farther away and pointing the other direction - the plaque on the marker now faces the tree. Of course, the marker could have been moved. I need to take the 1933 photo to the tree and examine the big branches. Bubba73 ^{You talkin' to me?} 05:39, 15 October 2019 (UTC)[reply]

Scratch #1 - a rough measurement of the 1933 photo puts it about 6x the height of the marker; the recent one about 7x. Bubba73 ^{You talkin' to me?} 05:45, 15 October 2019 (UTC)[reply]

However, the marker looks like a different one. The plaque on the current marker is old, but the concrete might not be. Bubba73 ^{You talkin' to me?} 05:48, 15 October 2019 (UTC)[reply]

I don't think there's any way to get a very accurate answer without obtaining a core sample (or a much older photo). According to our article oaks are very long lived (see also Bowthorpe Oak). But size isn't going to be a very good indicator of age because it's going to be complicated by any number of other factors, such as nutrients, exposure to elements, pests, and so on. Matt Deres (talk) 20:18, 16 October 2019 (UTC)[reply]

How to Age a Live Oak Tree (by measuring the circumference).

How to measure a live oak’s girth: "Dr. Stephens estimated that an oak with a girth of 17 feet or more (the Live Oak Society today says 16 ft.) should be at least 100 years of age. But he noted also that many live oaks of much smaller girth can be more than 100 years old as well. The girth can vary significantly depending on whether the tree grows out in the open, far from other trees competing for light and water, or in a natural forest setting where it is more crowded (close-grown). Also, the growth rate and overall health of an oak can vary depending on the quality of the soil in which it grows and its access to a regular water source".

Famous Trees (1938) Charles Edgar Randall, p. 48 has another photograph. Alansplodge (talk) 18:27, 17 October 2019 (UTC)[reply]

Oak trees can be very long lived. The Bowthorpe Oak is thought to be over 1,000 years old. Richerman (talk) 20:29, 17 October 2019 (UTC)[reply]

Blood backflow in IV

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 extending to the infusion-bag) might have on a patient, with due references to medical literature. ∯WBG^{style="color:#00F">converse} 04:40, 15 October 2019 (UTC)[reply]

So to prevent backflow into the iv line? I guess the first question is why would this need to be prevented? It is not really a big deal... Doc James (talk · contribs · email) 09:25, 15 October 2019 (UTC)[reply]

If you put the search term "backflow" into pubmed you get a number of articles that might help. This one caught my eye: Avoiding iatrogenic thrombo-embolism: the "KAPLIT" technique. It says "Also backflow of blood into the IV tubing ... predisposes to clotting of blood in the IV tubing/catheter. Overenthusiastic efforts to push IV fluids without disconnection and flushing of IV line may pose a possible risk of embolizing the clotted blood thrombus into circulation." 70.67.193.176 (talk) 21:02, 17 October 2019 (UTC)[reply]

XY chromosome disorders.

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 other 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).[reply]

The size of the Y chromosome actually has nothing to do with colorblindness. The reason that red-green colorblindness is more common in men (note, it is not exclusive to men, just very rare in women), is entirely due to the fact that only the X chromosome carries the genes for the red and green color receptors. The 8% rate (which is not for men in general, but for men of northern European descent) is a consequence of the mutations that cause it being found on about 8% of X chromosomes in that group. See X-linked recessive inheritance for more examples of diseases that are inherited in this fashion. And yes, a woman can be a carrier of red-green colorblindness, and pass it onto her sons. Someguy1221 (talk) 08:39, 15 October 2019 (UTC)[reply]

Indeed, in very rare cases, women can be red-green colorblind as well, if they received the recessive gene from both parents. A facile calculation of 0.08*0.08 = 0.0064, or about 6 out of every thousand women should be red-green colorblind. The actual quoted statistic in the Wikipedia article Color blindness is 0.5% (5 out of 1000), which is within rounding errors for these calculations. --Jayron 32 11:44, 15 October 2019 (UTC)[reply]

Correction, those figures are for people of Northern European descent rather than for the world population at large. --Jayron 32 12:03, 15 October 2019 (UTC)[reply]

Because of X-inactivation, it seems possible for a woman to be colorblind in only one eye. —Tamfang (talk) 19:44, 17 October 2019 (UTC)[reply]

Men too can have differing color vision in their eyes. While I am not color-blind, I do have differences in color perception between each of my eyes. Relatively speaking, one of my eyes sees things slightly redder and the other slightly bluer than the other. I have no idea which (if either) is "normal", but as I have had this my whole life, it is my "normal". --Jayron 32 16:49, 18 October 2019 (UTC)[reply]

You might consider taking the glasses off. Someguy1221 (talk) 17:38, 18 October 2019 (UTC)[reply]

Escape at less than escape velocity?

Is it possible for an object travelling at less than the escape velocity from the sun to escape the sun's gravity well by slingshot from another mass? This is without any thrust, I know that a slingshot can be used to greatly increase the effect of thrust by applying it near the point closest to the other object. -- ????

Yes. The third stages of the launch vehicles for Pioneer 10, Voyager 1 and Voyager 2 followed similar initial trajectories to their probes, but without thrusters for course correction or boost during gravity assist manoeuvers. All three third stages are now believed to have achieved solar escape velocity after unguided gravity assist fly-bys of Jupiter and Saturn - see List of artificial objects leaving the Solar System. Gandalf61 (talk) 08:26, 15 October 2019 (UTC)[reply]

Thanks, it certainly is possible then! -- Q Chris (talk) 11:23, 15 October 2019 (UTC)[reply]

Applying thrust at closest approach is to exploit the oberth effect, which is a separate concept from gravitational slingshot. They are often employed simultaneously, however. Someguy1221 (talk) 08:31, 15 October 2019 (UTC)[reply]

Interesting, I had not appreciated that they were different effects. -- Q Chris (talk) 11:23, 15 October 2019 (UTC)[reply]

well, these are means to acquire escape velocity, not to bypass the requirement, so the answer should be no (unless some "at the time of launching" is implied in the question) Gem fr (talk) 11:25, 15 October 2019 (UTC)[reply]

Obtaining carbon-oxygen compounds by burning

In the same way you can avoid getting CO by rising the temperature while burning or re-burning the gases, and obtain CO2 instead, could you tweak the burning further to maybe obtain some other carbon-oxygen compound? Would adding a third element change stuff? Can the by-product of burning, say methane or gasoline, but something else? C est moi anton (talk) 22:40, 15 October 2019 (UTC)[reply]

The burning of methane in oxygen results in a very complex equilibrium of mostly methane, oxygen, carbon dioxide, carbon monoxide and water. The precise equilibrium depends on temperature, which is of course highly variable across a typical flame. In principle you can use the data at this source to compute the amount of carbon monoxide vs. carbon dioxide generated under various conditions, but generally, following Le Chatelier's principle, we might predict that injecting extra oxygen into the reaction will reduce the production of carbon monoxide, and favor the production of carbon dioxide. See also Combustion#Incomplete_combustion_of_a_hydrocarbon_in_oxygen. It is possible to convert methane and other hydrocarbons into a variety of different compounds, and you can indeed achieve this by burning in an atmosphere with a reactive molecule other than oxygen, such as a halogen (see Haloalkane). Indeed, just having other compounds or elements present during combustion can result in traces of these alternative products being generated even when oxygen is the primary fuel. For example, setting fire to a complex mixture of compounds, such as compost, will result in a huge menagerie of products being generated. Someguy1221 (talk) 23:43, 15 October 2019 (UTC)[reply]

While there are other oxygen-carbon compounds than CO2 (such as the aforementioned CO and the ones noted below), it is important to note that CO2 is the lowest energy state for a carbon-oxygen compound. That is, all other forms of C-O compounds have more chemical potential energy than does CO2. Since burning is an exothermic process (that is, it turns potential energy into kinetic energy), it tends to stop once the potential energy minimum is reached. More exotic C-O compounds, with more oxygens, require an endothermic process (i.e. it requires us to turn kinetic energy to potential), which would require an entirely different mechanism than burning. --Jayron 32 12:22, 16 October 2019 (UTC)[reply]

You may also be interested in the Oxocarbon page, although most will not be made by burning! I like carbon pentoxide. Graeme Bartlett (talk) 10:58, 16 October 2019 (UTC)[reply]

As explained above, CO2 is the most stable oxygen-carbon compound at room temperature and pressure. In practice CO and CO2 are the only C-O compounds found in significant quantities at the end of combustion processes, and increasing temperature tends to further burn the CO (as long as there is excess oxygen), but it is not true that increasing the reaction temperature will necessarily increase the fraction of the room-temperature-stable compound.

For instance, in internal combustion engines, increasing the combustion temperature can increase the amount of NOx because at the combustion temperatures such compounds get formed and they do not separate into the (more stable) N2/O2 when brought rapidly to low temperatures. Tigraan^{Click here to contact me} 10:12, 17 October 2019 (UTC)[reply]

That's a great example of the difference between chemical kinetics and chemical thermodynamics. At high temperatures, the NOx compounds are more stable thermodynamically. At low temperatures, the NO2/O2 mixture is more stable. However, there is a large activation energy "hump" to get over to get from NOx to N2 & O2, and at lower temperatures there isn't enough ambient energy to get over that hump. The NOx products are what we call metastable, but they have a stupidly long half-life, long enough that on human timescales we consider it stable (even though it doesn't technically exist at the lowest energy state for the given temperature). Processes that are thermodynamically stable, but kinetically difficult don't happen on time scales necessary for easy human observation. --Jayron 32 11:15, 17 October 2019 (UTC)[reply]

For that idea in a more macroscale context, see Pitch drop experiment. DMacks (talk) 04:12, 18 October 2019 (UTC)[reply]

October 16

Flu Jab

When getting the flu jab, there is a form that needs to be filled out. One of the questions asks, how do you feel at the moment. Hypothetically if one were to fill this in and say you were healthy but actually you already had the flu, what would the outcome be? Would you end up with pneumonia Also, what is the difference between pneumonia and simply having the winter flu? How would one tell the difference between really bad flu and pneumonia? This just a hypothetical, its not a request for medical advice. I am more curious in the science behind it. Thanks Anton 81.131.40.58 (talk) 10:53, 16 October 2019 (UTC)[reply]

See https://immunisationhandbook.health.gov.au/vaccine-preventable-diseases/influenza-flu for some government information. I will leave you to read this and figure out whether immunization is recommended when you are already sick. Graeme Bartlett (talk) 11:06, 16 October 2019 (UTC)[reply]

To the final question, pneumonia, which you linked, is an inflammatory condition of the lungs, which is caused by various infections as well as non-infectious conditions (though infection is vastly more common). Pneumonia is not itself an infection. The flu is generally experienced as an upper respiratory tract infection, well clear of the lungs themselves. Someguy1221 (talk) 11:13, 16 October 2019 (UTC)[reply]

Yes, but the influenza article says that bad cases can lead to pneumonia, so my question is, how would one known when the trasition has happened? Thanks Anton 81.131.40.58 (talk) 11:37, 16 October 2019 (UTC)[reply]

The Wikipedia article titled Pneumonia has an entire section labeled diagnosis, that should tell you how one would know when one has pneumonia. --Jayron 32 12:17, 16 October 2019 (UTC)[reply]

Exactly. But just to emphasize Someguy's point, pneumonia is not what you "catch", it's what you sometimes experience depending on how what you've "caught" has progressed. You could substitute conditions like "persistent cough" or "post nasal drip" - you don't "catch" those; you "caught" the cold or flu or whatever and it has infected you successfully enough to induce those responses. It may seem like a technicality, but it's an extremely important one. Matt Deres (talk) 20:26, 16 October 2019 (UTC)[reply]

Note also per the article, bacteria are more common causative agents than viral ones in most situations, although causative agents cannot always be identified. So if you just know someone has pneumonia it's not generally wise to jump to influenza without further information. Nil Einne (talk) 07:53, 17 October 2019 (UTC)[reply]

Also, also important is the notion of secondary infection, which means that, strictly speaking, the pneumonia may not be caused directly by the influenza virus, however the flu may make one susceptible to other infections, and those OTHER infections may be what causes the pneumonia. --Jayron 32 12:14, 17 October 2019 (UTC)[reply]

@ Someguy - According to the Mayo Clinic the signs and symptoms of flu are:- fever over 100.4 F (38 C), acheing muscles, chills and sweats, headache, dry, persistent cough, fatigue and weakness, nasal congestion and sore throat. That list seems a bit more than an upper respiratory tract infection and that is probably because influenza is a body-wide infection. (Anecdote warning) Having had flu 3 times in my life it is well beyond a URTI in my experience. Richard Avery (talk) 22:28, 17 October 2019 (UTC)[reply]

Hi Richard. That is a very crucial observation, but it might not mean what you think it does. Or "upper respiratory infection" might not mean what you think it does. Or maybe your statement doesn't mean what I think it does. Anyway, the cells that are infected by a virus do not necessarily coincide with the organs that develop symptoms. Because the immune response to an infection includes the release of systemic signalling molecules, the entire body can feel the effects. I'm not sure of a single article that goes over this in good detail, but I'd direct you to cytokine, chemokine, interferon, and the woefully short immune response. Someguy1221 (talk) 08:14, 18 October 2019 (UTC)[reply]

I got a flu jab a couple days ago and didn't have to fill anything out. They asked if I had any allergies to them and I said no and I had a jab 2 years ago with no noticible side effects. I didn't fill anything out that time either, iirc, and it was at a different facility. 173.228.123.207 (talk) 23:27, 17 October 2019 (UTC)[reply]

I take it "jab" is a Britishism? ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:54, 18 October 2019 (UTC)[reply]

Indeed, equivalent to 'jag', which is a Scottishism. Richard Avery (talk) 07:24, 18 October 2019 (UTC)[reply]

Jab would be an injection and as far as filling out form, I assume that different countries do it differently. Anton 81.131.40.58 (talk) 15:27, 18 October 2019 (UTC)[reply]

Seto Inland Sea land reclamation

Were there any plans in the past to drain part or all of the Seto inland sea, reclaiming the area for farming and housing? Thanks. --2.37.200.57 (talk) 14:33, 16 October 2019 (UTC)[reply]

The notion of draining Setouchi may have arisen but been left to languish like that of Atlantropa because investors in such a project would be deterred by a geologist's risk assessment of the area prone to subducting sea plates, recurring tsunami-producing earthquakes and volcanos on the Pacific Ring of Fire. DroneB (talk) 15:03, 16 October 2019 (UTC)[reply]

Yes, some for industry and rice production, see Figure 35 here [8] (it's unlabeled). Some of the reclamation was under the 1962 plan of the Comprehensive National Land Development Act of 1950.—eric 18:41, 16 October 2019 (UTC)[reply]

October 17

Bacopa Monnieri

I got a bottle of this stuff in mail one day, charge free. Never heard about it. A quick check showed that people claim various cognitive benefits. Is anybody aware of any solid research on this plant? Thanks, - AboutFace 22 (talk) 02:02, 17 October 2019 (UTC)[reply]

Here's what WebMD has to say:[9] I notice several "might" qualifiers in there. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:47, 17 October 2019 (UTC)[reply]

FWI Bacopa monnieri Anton 81.131.40.58 (talk) 08:13, 17 October 2019 (UTC)[reply]

Touch and death

They say that a baby will die if it is provided with food, water, etc but never given human touch. Is this true of other animals? Temerarius (talk) 02:27, 17 October 2019 (UTC)[reply]

Can you supply any documented information about what “they” say in relation to human infants? It sounds like a myth. Dolphin (t) 02:36, 17 October 2019 (UTC)[reply]

There have been experiments with monkeys that show they do need a "mother", but that can just be a warm blanket with a monkey face mask, it doesn't need to be an actual monkey. And, of course, some animals are independent from birth, like sea turtles, so they don't need any such contact. Other animals that do need mothers can attach themselves to other species, in a process called imprinting. SinisterLefty (talk) 05:34, 17 October 2019 (UTC)[reply]

1st, 2nd law of thermodynamics and the rest

Are the first and second laws of thermodynamics somehow more important or for some reason to be singled out from the rest:

In University Physics by Young's index:

Thermodynamics

Only the first two are studied, at least in a separate chapter. Is that normal for a general textbook? C est moi anton (talk) 08:50, 17 October 2019 (UTC)[reply]

The reason why those two are singled out is that they have the greatest implications for most people. The first law is the law of conservation of energy and the second is the law of increasing entropy. The third law, which is merely a definition of zero entropy; is ultimately not that necessary since we can define a "zero" point anywhere and the other laws still work fine, after all we deal with concepts like energy and enthalpy just fine even though we have no meaningful "zero" point for those values, we just deal in "ΔE" and "ΔH", which is all we need to know anyways. The zeroth law of thermodynamics is a rather unsurprising law describing the transitive nature of energy; that is if state A is in equilibrium with state B, and state B is in equilibrium with state C, than A is in equilibrium with C. It's really only necessary to define thermodynamics as transitive for the sort of mathematical formalism necessary to prove certain other mathematical relationships, but it's not really all that broadly necessary for anything else. The first and second, however, have HUGE implications for the behavior of energy in the universe, which is why we focus on them so much. --Jayron 32 11:10, 17 October 2019 (UTC)[reply]

Dating ancient artifacts that do not contain carbon

Would radiocarbon dating be of any indirect use here? That is, if they find a clay table buried with a bone, they can speculate that the former is at least as old as the latter. Are there direct methods for dating, at least for man-made artifacts? The relevant article Dating in archeology only mentions the existence of direct methods, but does ceramic, swords or glass deteriorate in a way that can be measured? C est moi anton (talk) 10:22, 17 October 2019 (UTC)[reply]

I don't think that any of those materials can be dated directly. Dating in archaeology, like geology, mainly relies on relative dating. The stratigraphy of the site is determined and then any dateable materials are analysed (using the methods listed in the article that you linked to) to provide fixed points in the site's chronology. The artefacts are then dated by comparison with these fixed points. Mikenorton (talk) 11:04, 17 October 2019 (UTC)[reply]

Apparently lead can be dated directly in some circumstances - as here. Mikenorton (talk) 11:25, 17 October 2019 (UTC)[reply]

Iron objects contain carbon:) See [10] for an article about dating iron objects. DMacks (talk) 13:37, 17 October 2019 (UTC)[reply]

Wouldn't clay also contain some carbon? C est moi anton (talk) 16:15, 17 October 2019 (UTC)[reply]

Clay tablets were generally dried rather than fired so any carbon in them would not record the date of the tablets themselves. Most clays anyway don't have a significant organic content. Mikenorton (talk) 16:46, 17 October 2019 (UTC)[reply]

Ceramics, including clay if fired, may be datable via Thermoluminescence dating or by Rehydroxylation dating. Some clay tablets were fired not intentionally but when the building storing them was burned down, as mentioned in the article linked by Mikenorton immediately above.

Some carved stone may be datable by Luminescence dating.

A particular artifact, irrespective of its nature, might be datable by various Geochronology techniques if it has been preserved in an applicable context, as implied in the OP and first response. {The poster formerly known as 87.81.230.195} 90.200.41.118 (talk) 17:24, 17 October 2019 (UTC)[reply]

Are one-to-one comparisons between superlative physical traits of small animals versus large animals "fair"?

There's a new animal show on TV (Little Giants) that focuses a great deal on measuring some physical feat of a small animal and then breathlessly exclaiming about how if you scaled the feat up to human sized it would be so astounding. For example, that the giant horned lizard shoots toxic blood out of its eyes and the 3-foot distance it squirts the blood would be like it squirting the blood five football fields at human size (making up the numbers to give you an idea of what I'm talking about; not verbatim from show); or that the mouse lemurs' X-foot jumps between trees is like a human jumping Y feet, and so on (wow!).

I don't have the science background to back up my nagging feeling that the comparisons they're exclaiming over are not really kosher. Is this one-to-one comparison "fair", or is there some factor of "economies of scale" or something like that, that explains why these scaling comparisons are not as incredible as they seem? Does it really work like that? Or would, for example, a human scaled down to a tiny size also be able to throw much farther in comparison to their normal size because of the way the physical world works at the small versus large scale? Lady in polka dot (talk) 23:10, 17 October 2019 (UTC)[reply]

You are right to be skeptical. See square-cube law and, linked from that, allometry. --76.69.116.4 (talk) 23:49, 17 October 2019 (UTC)[reply]

October 18

elements most similar to iron chemically

Would ruthenium or nickel be pretty similar chemically? It says that nickel doesnt rust as easily, so maybe not as far as oxygen is concerned—Actually i’m wondering what atoms could accidentally replace iron in hemoglobin if any, and thereby cause health problems.Rich (talk) 00:06, 18 October 2019 (UTC)[reply]

I could not tell you why neither of those metals are used as oxygen carriers, but the second most common biological oxygen-carrying metal after iron is copper, as in hemocyanin. Someguy1221 (talk) 08:39, 18 October 2019 (UTC)[reply]

In order to functionally take the place of iron in hemoglobin, an element would need to have both a similar atomic radius and a similar coordination number so that it would "fit" into the hole that iron is taking up. In general, the problem is not in iron being replaced in hemoglobin, but rather the oxygen. Carbon monoxide (CO) molecules have similar sizes and shapes, and orbital orientations to dioxygen (O2), and forms stronger bonds to the iron atom than does the O2, so it will tend to block O2 from bonding to the iron; which is how it kills you. --Jayron 32 12:01, 18 October 2019 (UTC)[reply]

Cobalt and nickel are pretty close: they are the other two members of the iron triad. And indeed, there is such a thing as coboglobin. Double sharp (talk) 12:15, 18 October 2019 (UTC)[reply]

doi:10.1021/bk-1986-0321.ch016 is about nickel–hemoglobin. I don't have full access to read it, but it appears to be discussing more physical-chemistry details rather than at the level of possible oxygen-transport ability. DMacks (talk) 18:21, 18 October 2019 (UTC)[reply]

Real-life mist from Stephen King

Inspired by watching The Mist movie and the series of the same name, do you guys think it's possible for the kind of mist seen in Stephen King's novel could happen in real-life in which strolling through the mist is dangerous either because there are monsters in them (as seen in the movie) or the mist itself that would take the life force out of the body (as seen in the series)? Planet Star 08:20, 18 October 2019 (UTC)[reply]

No. Anton 81.131.40.58 (talk) 09:41, 18 October 2019 (UTC)[reply]

I suspect Brexit is more likely to "take the life force out of the body" than mist. Martinevans123 (talk) 10:13, 18 October 2019 (UTC)[reply]

My job takes the life force out of my body. But I have coffee before and beer afterwards; that seems to help. --Jayron 32 11:50, 18 October 2019 (UTC)[reply]

Mmm, sounds great. Martinevans123 (talk) 12:09, 18 October 2019 (UTC) right on, Jayron. It was the great Jimbo Marx, wasn't it, who said, all those years ago, "Wikipedia is the opium of the masses"?[reply]

How can an adult like PlanetStar be so confused about the nature of fiction, and not know that reality does not include monsters or "life forces"? Was his account hijacked by a troll?--Lgriot (talk) 13:47, 18 October 2019 (UTC)[reply]

Not necessarily a troll. I know nothing about PlanetStar but could he/she have kids using the computer? -- Q Chris (talk) 14:01, 18 October 2019 (UTC)[reply]

Probably not a troll or hacking. See the response from this user on their talk page under the title "Reference desk" about a similar nonsense question posted 3 years ago. Richerman (talk) 14:41, 18 October 2019 (UTC)[reply]

Are you the one who keeps asking about SVU episodes? ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:51, 18 October 2019 (UTC)[reply]

Nothing which Stephen King describes is possible. That's his style: everything in there – even if not obvious from the beginning – is based on something utterly outside human knowledge and experience. The Shining could be a story of psychological disintegration, but King bases it on something supernatural. The Stand could be a post-apocalyptic tale of bioweapons, but it turns into Milton. Misery is perhaps his only novel that has nothing weirder in it than humanity itself. But this means that King's scenarios can't be analysed. You can't look for the cryptozoology of Stephen King when it's impossible by design. Andy Dingley (talk) 16:01, 18 October 2019 (UTC)[reply]

Ah yes the great Milton. He could knock out a damn good supernatural horror sofa-gripper. Martinevans123 (talk) 21:23, 18 October 2019 (UTC)[reply]

I agree with Richerman that I wasn't trolling or being hacked. I'm being cool. I get inspired to ask even an outlandish question and have discussion about it. I'm well aware that such a possibility of that happening is extremely slim, if not zero. If it doesn't happen on Earth, it could happen on another world that have advanced civilization. In the movie The Mist, the military operation went wrong that they opened the interdimensional portal to let monsters along the mist into the main realm. Physicists suspect there are other dimensions, and some believe that another dimension can be accessed through portals (see interdimensional being). There are all sorts of secret military operations going on around the world. Many operations could come with just as many kinds of accident as a result, some could be the kind that could right now be only generally be talked about it in fiction. One example is cloning, which if they did something wrong could result in a monster that could attack or kill people. Planet Star 02:12, 19 October 2019 (UTC)[reply]

Yes indeed. In her short seven years, I believe that Dolly exercised a brutal "reign of terror" across the uplands of Midlothian. Martinevans123 (talk) 09:11, 19 October 2019 (UTC)[reply]

Strolling through poison gas will take the life force from your body. Monsters aren't likely to survive in it very well either, unless you are willing to accept microbial extremophiles as your monsters.-gadfium 05:16, 19 October 2019 (UTC)[reply]

Washing machines

Do washing machines typically revolve clockwise or anti-clockwise? Or does this depend on whether you're in the Southern or Northern hemisphere? 86.187.233.217 (talk) 21:45, 18 October 2019 (UTC)[reply]

Typically, neither. To prevent the laundry from tangling spirally on itself, the rotation direction alternates every few rounds. I once had a drier that was engineered by some half-wits that didn't used this tried-and-true method. It tangled bedsheets to the point I had to throw them away. אילן שמעוני (talk) 22:22, 18 October 2019 (UTC)[reply]

I think it's safe to say that in this big world different designs of washing machine are likely to be common in different parts. In particular some places have strong preference for the more efficient front-loading design (which may have glass in the door so you can see how it rotates) but in North America the simpler top-loading design is also common (and I've never seen one with glass in the lid, but if you open it during the spin cycle, you can see which way it's turning). Likewise, in some places the same machine is commonly both a washer and a dryer. I can say that (unlike the preference of אילן שמעוני) I've never owned a tumble dryer, or seen one in a laundromat, that did not turn in a single direction. My current dryer, and my current top-loading washing machine, both turn clockwise as seen by a person using the machine. --76.69.116.4 (talk) 05:17, 19 October 2019 (UTC)[reply]

Intriguing. Now the only culprit I could think of is refuted. אילן שמעוני (talk) 07:33, 19 October 2019 (UTC)[reply]

Civil engineering accidents

Worldwide, is it common for individual civil engineers to be sentenced to prison when people die or bare injured as a result of engineering related accidents? 90.194.57.188 (talk) 21:46, 18 October 2019 (UTC)[reply]

Were you including blocks of flats with flammable exterior cladding? In such cases it seems to be more likely that the "Tenant Management Organisation" might be held to be criminally responsible, i.e. not even the local Authority, let alone the civil engineers who built the property. Sorry to focus on such a specific example. I guess many bridges fall down. Many buildings collapse. Martinevans123 (talk) 21:57, 18 October 2019 (UTC)[reply]

In Israel there were three such cases that reached headlines. A bridge under construction that collapsed on the motorway killing 3. A pedestrian bridge that crumbled under the feet of athletes, killing 4, and the collapse of a dance floor that killed 23. In all cases the engineers that ratified the work plans were sentenced to several years in prison, as well as compensating the families. אילן שמעוני (talk) 22:28, 18 October 2019 (UTC)[reply]

There is a very old legal concept known as gross negligence (see also negligent homicide), which is related to the concept duty of care. Basically, if you know that what you are doing could kill someone if you screw it up, and you fail to take reasonable measures to prevent that, you could be in a whole heap of trouble. Even Hammurabi's code contained laws regarding the liability of a builder to the victims of a collapsed building. In modern jurisprudence, though it of course varies by location, the negligence is really key. The fact that someone died or was injured is a component of the crime, but guilt hinges on how reckless the responsible person was. Someguy1221 (talk) 01:03, 19 October 2019 (UTC)[reply]

Wouldn’t it be the case that in many situations, it would have been a system failure or pressure from the company management though? Clover345 (talk) 09:41, 19 October 2019 (UTC)[reply]

October 19

New railway construction

When building new railway lines on flat land in areas with no civil engineering structures required, is the excavation and basic pavement laid down by the civils contractor or by the track contractor? Clover345 (talk) 08:54, 19 October 2019 (UTC)[reply]

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

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