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January 31

Which theory explains Earth rotation?

If Einstein's General relativity explains Earth revolution, then which theory explains Earth rotation? Rizosome (talk) 06:34, 31 January 2021 (UTC)[reply]

Are you asking why the earth spins? ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:03, 31 January 2021 (UTC)[reply]

Courtesy link: Earth's rotation, specifically Earth's rotation#Origin.

Please clarify the premise of your question. Are you highlighting some aspect of the Earth's revolution which is inadequately described by Newtonian physics?

Note: It is best to use internal wikilinks (double square brackets) when linking Wikipedia articles. If you wish text other than the article name to appear in a link, then use piped links (see WP:PIPE), such as "[[Earth's orbit|Earth revolution]]" which yields Earth revolution.

-- ToE 14:02, 31 January 2021 (UTC)[reply]

What makes Earth spin? Rizosome (talk) 14:14, 31 January 2021 (UTC)[reply]

Love Makes the World Go 'Round —2603:6081:1C00:1187:3439:5742:B1FB:BCCC (talk)~ — Preceding undated comment added 16:03, 31 January 2021 (UTC)[reply]

Spin is ubiquitous in the cosmos. Planets rotate, as do stars and galaxies. This comes about simply from conservation of angular momentum. When two ice skaters (or celestial bodies) approach each other and link arms (or are attracted due to gravity), they will start rotating.--Shantavira|^{feed me} 16:24, 31 January 2021 (UTC)[reply]

Unfortunately, the angular momentum Wikipedia article is rather technically dense, and by the second paragraph is already introducing terminology likely to confuse the average layperson. This video from the YouTube channel "Science Asylum" does a pretty good job explaining the role of angular momentum in the formation of the solar system. This video from Universe Today deals with the same issue as well. --Jayron 32 14:50, 1 February 2021 (UTC)[reply]

Into what does the human body convert acetic acid?

The human body normally converts ethanol to acetaldehyde which is more poisonous. Then acetaldehyde to acetic acid (vinegar) which is less poisonous than ethanol. But what does it convert the acetic acid into? JRSpriggs (talk) 22:20, 31 January 2021 (UTC)[reply]

WHAAOE. It's metabolised to acetyl-CoA: see Ethanol metabolism#Acetic acid to acetyl-CoA, which also explains what happens next. {The poster formerly known as 87.81.230.195} 90.200.40.9 (talk) 02:48, 1 February 2021 (UTC)[reply]

Yep, this is how it can be "burned" for energy as a macronutrient. Acetyl-CoA is the "entry point" into the citric acid cycle for nutrients. The all-ethanol diet is not recommended, however. --47.152.93.24 (talk) 17:31, 1 February 2021 (UTC)[reply]

February 1

Stabbing someone in the midst of a heart attack

Hello, Wikipedians I`m just posting this question because I`m curious what would happen if you stabbed someone in the heart while they were in the midst of a heart attack? Thank You — Preceding unsigned comment added by 98.113.197.52 (talk) 00:51, 1 February 2021 (UTC)[reply]

They would probably die. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:16, 1 February 2021 (UTC)[reply]

If you have reason to think they are a vampire, the recommendation is to use a wooden stake for best results. --Lambiam 11:48, 1 February 2021 (UTC)[reply]

There is a famous scene showing an emergency intracardiac injection of epinepherine in the movie Pulp Fiction to keep the person's heart beating, but it was after the person had overdosed on heroin, not during a heart attack. Also, the heart injection was fictional: those injections are usually given in a leg muscle. See epipen. I wonder if you may have been remembering that scene. 2602:24A:DE47:BB20:50DE:F402:42A6:A17D (talk) 08:32, 1 February 2021 (UTC)[reply]

Are you thinking of pericardial tamponade? It can cause cardiac arrest, which is technically not a Heart attack (disambiguation) but is often colloquially called one. Pericardiocentesis, a treatment for pericardial tamponade, could be rather inadequately described as stabbing someone near the heart. Pericardiocentesis can be lifesaving, but it is ideally administered before the patient goes into cardiac arrest. If you want medical advice, take an advanced first aid course that includes first aid for firearm wounds (being shot in the heart is a common cause of pericardial tamponade). HLHJ (talk) 03:54, 2 February 2021 (UTC)[reply]

Assuming the blade doesn't directly enter the heart - which would cause instant death - the two would compound each other. A heart attack causes decreased heart oxygenation, while stabbing causes blood loss. Less blood means even less oxygen going to the unharmed parts of the heart. So the answer is, very likely, the person would die. Red Panda 25 21:12, 3 February 2021 (UTC)[reply]

The OP specifically said stabbed "in the heart". ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:29, 3 February 2021 (UTC)[reply]

Did you intend to find an answer from a legal perspective? Like what happens if you kill someone, who was dying within seconds? — Preceding unsigned comment added by Bumptump (talk • contribs) 21:46, 3 February 2021 (UTC)[reply]

Since the OP has only made the one edit, we may never know. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:30, 3 February 2021 (UTC)[reply]

Unlimited bandwith for over-the-air broadcasting

If everyone in my city had a radio they tuned to the same station at once, or a broadcast TV tuned to the same channel, we could all watch/listen simultaneously with no bandwidth or capacity issues (ignoring weather, antenna location, distance from the source, etc.) But if we all tried to make a mobile phone call or use the internet at once, we would have capacity issues. My guess is because of the two-way nature of phones and the internet, and also physical constraints such as the towers and the fiber and cable wiring. But is there a better explanation for this and would it also apply to satellite TV/radio?174.16.121.131 (talk) 00:59, 1 February 2021 (UTC)[reply]

I do not think that this is correct. In electronics, if you add more resisters in parallel, eventually the total resistance would be reduced to the point that the voltage would not be measurable. In other words, each receiver adds to the load on the transmitter until the transmitter is no longer able to drive the signal through the noise.

Another way to look at it is that each receiver also is a transmitter which transmits a signal roughly opposite (but smaller in magnitude) to the primary transmitter and partially cancelling it out. JRSpriggs (talk) 01:48, 1 February 2021 (UTC)[reply]

Basically as the signal to noise ratio decreases, the ability to extract information from the stuff coming into the receiver also decreases. If there are 1000 transmitters on a frequency and you're trying to listen to just one of them, the other 999 are "noise". The theoretical limits are established in Shannon's noisy channel coding theorem and modern spread-spectrum modulation schemes (like in current mobile phone systems) are really very good. By comparison, old-school broadcast radio is terrible. 2602:24A:DE47:BB20:50DE:F402:42A6:A17D (talk) 07:48, 1 February 2021 (UTC)[reply]

In a radio broadcast, there's a single transmitter sending the same signal to everybody at the same time. When using modile phones, the transmitters have to send a different signal to each separate user, so the total amount of signal is much higher. PiusImpavidus (talk) 08:45, 1 February 2021 (UTC)[reply]

The term "bandwidth" has two different meanings. In signal processing, "bandwidth" refers to the size of the portion in the frequency spectrum taken up by the signal. It can be related to the maximum rate of information transfer, but is a property of the signal, not coupled to a notion of channel. In networking, "bandwidth" is a property of a channel, directly specified as the maximum rate of information transfer. So the best explanation, I think, is that the set-up conflates these two notions. --Lambiam 11:41, 1 February 2021 (UTC)[reply]

Yes, modern satellite TV and satellite radio is duplex just like cellular service or the Internet; satellite receivers and the transmitters on the satellite communicate back-and-forth. One reason for this is to encrypt the signals, so free riders can't pick up the broadcasted content. --47.152.93.24 (talk) 18:51, 4 February 2021 (UTC)[reply]

^{[citation needed]} on the claim satellite TV or radio is duplex. I'm sure they exist, but I've never heard of them, nor any part of the world where they are common. Unencrypted satellite TV is generally just some variety of DVB-S. Encrypted satellite TV is generally just some variety of DVB-S with some form of encryption in the mix. While it is theoretically possible someone would require two-way communication for that, nearly all do not, even the infamous NDS VideoGuard. The smart card does require regular updates, but it doesn't need outward communication for those. (If you take out the smart card for a very long time, it's possible it won't work, in that case some outward communication maybe required either by the STB or end user.) For stuff like Pay-per-view, two way communication can be required but even then only in a limited way. In particular, for PPV purchased from the set top box or similar, there is some need for the box to communicate the purchase decision, but this was traditionally via modem and nowadays often via wired ethernet or Wi-Fi. For PPV purchased over the internet or phone, there's generally no need for the STB to communicate outwards as the provider simply signals the STB ~~a few times~~ and assumes it's received. Nil Einne (talk) 11:45, 5 February 2021 (UTC)[reply]

I'm no expert, but I do have DirecTV service, and the receiver definitely talks to the satellite. You can access information about receivers through their website/app, regardless of whether the receiver has an Internet connection. Similarly, you can access PPV content, etc. through a receiver with no Internet connection. --47.152.93.24 (talk) 02:42, 6 February 2021 (UTC)[reply]

I see zero indication from either our article or a general search that DirectTV STBs are able to communicate via satellite. What do you mean by "you can access information"? Of course you can see what PPV content is available on the STB. There's zero need for the STB to communicate outwards for that as I already explained. The provider is simply sending that information all the time. Likewise, the provider knows about your STB, which channels you are subscribed to etc, that's how it works. So you can see that information on the internet.

Can you actually purchase PPV content from the STB with no internet or phone line connected? (DirectTV themselves don't think so [1].) And I don't mean "try to", I mean actually purchase. Plenty of STBs have terrible UIs so it's very probable it would appear you can purchase PPV content until you actually try the final step of purchasing when it may then tell you you need an internet connection. (But don't blame me if it does work and you have to pay.) Note as I already explained, purchasing PPV content via the internet or phone or SMS or whatever is expected. There's zero reason the STB needs to communicate outwards for this. The provider simply signals the STB to provide access (via the satellite).

Can you see information that is exclusive to the STB? For example, if you have a PVR type STB, can you actually see what you recorded even though you set up the recordings through the STB with no internet or phone line connected? (Setting up recordings over the internet, again the provider may keep track of such recordings and can communicate with the STB via satellite to let it know what you want to record without needing an outgoing connection from the STB.)

If you can do either of these or something else where outwards communication is required, how sure are you that the STB really has no access outwards communication via other means? Have you checked the back of the STB to make sure they didn't connect an ethernet line or phone line when setting it up? Note that if you have Wi-Fi internet in the home provided by AT&T and didn't bother to change the default password, there's a reasonable chance AT&T just set up the STB to access this Wi-Fi. Even if you did change the Wi-Fi password, if you're using their router there's a good chance they have remote access for management so perhaps they take your Wi-Fi password and provide it to the STB.

Of course it's possible there's no need for any of this since the STBs come with built in mobile network support in some form, for something so simple even 2G would be enough (some old smart meters use 2G for example, it's one reason 2G is being kept in a number of places) although considering this is AT&T, newer STBs would probably just have 4G if they wanted to do that.

Nil Einne (talk) 05:13, 6 February 2021 (UTC)[reply]

P.S. See e.g. [2]. Why would DirecTV only come after people for possible misuse if the STB has a phone or internet connection ,if the STB could report this via satellite?

BTW, it's theoretically possible that AT&T would allow the STB to automatically connect to a neighbour's password protected Wi-Fi that they know about although I find this very unlikely. However more likely it may connect to a non password protected Wi-Fi, perhaps without even asking you. From what I can tell e.g. [3], it should be clear somewhere on the STB if you are connected to Wi-Fi and you can disable it but as always unless you actually did that you shouldn't assume it's the case. (It is theoretically possible that the connected thing could be misleading if it does know WiFi details of some AP it can see somehow, but I find this very unlikely.)

I didn't find any indication that DirectTV STBs generally have any sort of mobile network connection.

I did find [4] [5] [6] which suggests that DirectTV was and probably still is using co-ax for ethernet via DECA splitters. So actually rather than just checking the STB for any connection, although I still suspect the UI should be clear about any internet connection but maybe not a phone line one, you probably need to check your router as well and ensure all ethernet cables are something you know about. If your internet comes from AT&T, you might also want to check that your "modem" or whatever if it's different from your router in case it has more than one output.

Nil Einne (talk) 06:00, 6 February 2021 (UTC)[reply]

Who predicted an Analemma (position of the sun in the sky) before it got photograph in 1990s?

Wiki page of Analemma didn't mention history of Analemma clearly well. If Albert Einstein predicted Gravitational waves then who predicted Analemma? Rizosome (talk) 06:21, 1 February 2021 (UTC)[reply]

This article (which is given as a reference in Analemma, so anybody could have found it) mentions Jean Paul Grandjean de Fouchy as the "inventor" of this particular type of representation in 1740. It is based on the concepts of equation of time and mean solar time. --Wrongfilter (talk) 07:31, 1 February 2021 (UTC)[reply]

Although in principle it could be predicted by someone who knew enough about the Earth's motion around the Sun and orientation in space, it can in fact be observed very simply (by plotting the position of, for example, the shadow of a fixed object on a fixed surface every few days over the course of a year), so it was known about long before before such knowledge was developed. Sundials, an ancient technology, generally take it into account. According to this, the 1st-century BCE Roman architect Vitruvius utilised the concept in his work (in order to know where shadows of buildings would or would not fall) and described its calculation and use in Book 9, Chapter 7 of his work De Architectura Libri Decem, though he didn't claim to have discovered it, and it was likely known to scholars at least several centuries earlier. {The poster formerly known as 87.81.230.195} 90.200.40.9 (talk) 10:07, 1 February 2021 (UTC)[reply]

As I understand it, Vitruvius' analemma was not identical to the figure that Rizosome asked about. For that figure to become apparent one needs a certain way of reckoning time (at what time of day do you have to take the indivdual exposures that go into the photograph?) – that's why I mentioned mean solar time, which is a concept that Vitruvius did not know about. Nevertheless there is obviously a relation between what Vitruvius did and what de Fauchy did. --Wrongfilter (talk) 10:45, 1 February 2021 (UTC)[reply]

In any case, the annual north–south swinging of the solar position has been observed and known since antiquity. To observe the much smaller east–west deviations requires sufficiently accurate timekeeping devices, such as the pendulum clock, invented in 1656. By the time of Fouchy (who deserves an article), the biannual east–west movement must also have been detected. No one (as far as we know) can be said to have "predicted" it; the observation preceded the explanation. Fouchy's role is that of an inventor: he invented a graphical method to relate the position of the Sun in the sky (giving the apparent solar time) to the mean solar time. --Lambiam 11:20, 1 February 2021 (UTC)[reply]

Lambiam From here, Analemma is developed by the French astronomer Grandjean de Fouchy. But in Analemma his name is missing. Is 1730 in science vandalism? Rizosome (talk) 15:45, 1 February 2021 (UTC)[reply]

Sources disagree about the year. Here we read "since 1730", but here we see "1740". Without extensive investigation, it is hard to tell which is wrong. --Lambiam 16:06, 1 February 2021 (UTC)[reply]

In his 1797 treatise De la mesure du temps par les horloges, scientist and watchmaker Ferdinand Berthoud writes that he knew of three analemmata having been drawn, the first being by Grandjean de Fouchy at the Count of Clermont, and two more he drew himself in 1737.^[7] This makes the date 1740 too late. It may be impossible to assign a precise date, because it seems that Fouchy has not published his invention but merely told others, such as Berthoud. Several French sources give an imprecise date, writing "vers 1730" ("around 1730" or "circa 1730"). --Lambiam 11:03, 2 February 2021 (UTC)[reply]

Lien de courtoisie: fr:Jean-Paul Grandjean de Fouchy. -- ToE 19:36, 1 February 2021 (UTC)[reply]

A number of churches in Italy have an analemma inlaid in the floor, and a pinhole in the south wall so that an image of the sun at noon falls thereon. One day in 200x, the sun was partially eclipsed for Italy at noon, and someone put out a call for photographs of the image of the crescent sun on such churches' analemmata. I supposed when I saw this gallery that the analemmata were made in the Renaissance, but perhaps not? —Tamfang (talk) 02:29, 3 February 2021 (UTC)[reply]

~~This would have been the solar eclipse of October 3, 2005.~~ It is possible that the traced figure and its significance was discovered independently several times, and it is not strictly impossible that some of these inlaid analemmata stem from the Renaissance. Some clock towers had striking clocks that were accurate enough already then; they would have struck the sexts every day at the same mean solar time. It would be interesting to historians of timekeeping to know the earliest construction dates. --Lambiam 09:32, 3 February 2021 (UTC)[reply]

Perhaps the solar eclipse of August 11, 1999, which passed as a partial eclipse over Italy around 10:45 UTC = 11:45 CET. (I had the privilege of watching its glorious totality that day from Amasya.) --Lambiam 17:08, 4 February 2021 (UTC)[reply]

February 3

Single use plastic

I've recently bought a disposable water filter for a jug and the package says "Reduce single use plastic". Since the filter itself is plastic and assuming it's the manufacturer's responsibility to produce non-plastic filters, I consider "reduce single use plastic" directed towards consumers a bit taunting and mocking. And per Brita (company), the manufacturer in question, "the filters can be recycled", which also makes that reduce plastic warning redundant. So does it make sense? 212.180.235.46 (talk) 12:28, 3 February 2021 (UTC)[reply]

I believe the message is about plastic water-bottles. Between the lines they're stating that decanting from a Brita into a re-usable bottle is a good thing, and well done you, rather than buying those one-use plastic water bottles. I agree it's a poorly directed message and reads like an accusation. Zindor (talk) 12:53, 3 February 2021 (UTC)[reply]

Context Is for Kings. The context here is a product that you use for filtering tap water. Britas aren't meant to be used to filter bottled water. So, by using a Brita instead of bottled water, you are reducing the amount of single use plastics since you aren't using single use plastic water bottles. Even the Brita filter itself isn't really a single use product; you use it to filter water again and again for months. The amount of water going through it is far greater than the amount of water that would be contained in single use plastic water bottles with an equivalent amount of plastic. --OuroborosCobra (talk) 18:24, 3 February 2021 (UTC)[reply]

Just in case there's any doubt, their website makes it clear that they're talking about the waste generated by bottled water.

“Single-use plastic bottles are destroying our planet. With Brita, you can enjoy great-tasting water without the waste.[8]”

ApLundell (talk) 23:43, 3 February 2021 (UTC)[reply]

Are you sure this was the literal text? If so, it is a bit crummy; it should be "single-use plastic waste" – what is being reduced is not the plastic (the incredible shrinking bottle) but the plastic waste. If this was not the literal text, perhaps it said, "reduces single-use plastic waste". --Lambiam 10:18, 4 February 2021 (UTC)[reply]

One important thing to note about bottled water. Unless you live in an area without access to safe drinking water (and there are a LOT of people in that situation, so don't get me wrong), bottled water is basically pointless. If you live in a major western city with a municipal water supply, the water in your bottled water is just drawn from the same water supply as your kitchen tap gives you. It's going to be produced in a local bottling plant, which may (but often does not) do some rudimentary filtering such as would be done by a Brita-type filter (but on a larger scale). When you buy bottled water, you're basically paying for just the bottle, and if you have containers in your house that can hold water, and a kitchen tap that delivers water from your local municipal water source, there's no conceivable advantage to drink bottled water. --Jayron 32 14:08, 4 February 2021 (UTC)[reply]

This may be true in the USA, but isn't true elsewhere. Our (UK) tap water has detectable chlorine in it. The bottled water we can buy comes from many different places and contains differing levels of minerals, so will taste different. The one I usually buy is from Evian in France.--Phil Holmes (talk) 08:16, 5 February 2021 (UTC)[reply]

Note that here "detectable" means: detectable by the unaided human sense of smell. --Lambiam 10:21, 5 February 2021 (UTC)[reply]

Not sure that I've ever tasted chlorine (like from a swimming pool) in British tap water, but the taste is certainly variable by location. Here (to the north of London) the taste is more neutral than most bottled water in my opinion. Where my Mum lives 60 miles away in Colchester, most people use a filter because of the slightly unpleasant taint, which I assume is due to the local geology. What the carbon footprint of carrying water all the way from France is, I can only imagine, especially as we have so much drinkable water of our own. Alansplodge (talk) 12:46, 6 February 2021 (UTC)[reply]

It is also true in many parts of the U.S.; you can get any number of different kinds of bottled water for your own purposes. If it is important enough for you to increase plastic waste and excessive shipping pollution to have French water, good for you! You should be proud. The shareholders and marketing executives of that corporation thank you heartily for doing your part to increase their wealth at the expense of the environment. --Jayron 32 14:46, 5 February 2021 (UTC)[reply]

February 4

drawing planets orbits around earth

I wish to produce the like of this image. I want it to make it myself so I can release it as creative commons. Preferably, I would like to include the orbits of Venus and Mercury as well. Is there a tool for this job? אילן שמעוני (talk) 01:11, 4 February 2021 (UTC)[reply]

The tool XEphem is capable of calculating and charting ephemerides, but I don't know if it will directly display this kind of chart. The calculation part has been isolated and made available in the form of the Python library pyephem. I have not examined its precise functionality, but our article Ecliptic coordinate system gives formulas for converting between equatorial and ecliptic coordinates, if necessary. List of information graphics software lists many apps that can convert a data set to a chart. --Lambiam 10:06, 4 February 2021 (UTC)[reply]

Vertical bar in chemical formula

The chemical formula given for lazurite is (Na,Ca)₈[(S,Cl,SO₄,OH)₂|(Al₆Si₆O₂₄)]. What does the vertical bar represent? –LaundryPizza03 (d c̄) 14:22, 4 February 2021 (UTC)[reply]

This discussion forum has some ideas. --Jayron 32 15:33, 4 February 2021 (UTC)[reply]

Almost every source presents a different formula. I saw this specific version in the 1992 book A Guide in Color to Precious & Semiprecious Stones.^[9] A 2000 research article in American Mineralogist has (Na,Ca)₈[Al₆Si₆O₂₄](SO₄,S)₂.^[10] --Lambiam 16:51, 4 February 2021 (UTC)[reply]

Cloning using CRISPR/gene editing question

Do you believe that it would ever become possible for us to edit the genes from any cell from our bodies (for instance, a skin cell)--saying, using CRISPR or whatever--and transform this cell into a zygote/embryo? Not into a sperm or egg, but rather into a zygote/embryo. Futurist110 (talk) 22:05, 4 February 2021 (UTC)[reply]

Yes. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:13, 4 February 2021 (UTC)[reply]

Would that also apply in regards to successfully transforming non-human bodily cells (for instance, a cat's or dog's skin cells) into human zygotes/embryos using gene editing? Futurist110 (talk) 01:38, 5 February 2021 (UTC)[reply]

Maybe. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:57, 5 February 2021 (UTC)[reply]

If I peel and mush some bananas, hollow out an orange and stuff it with the banana mush, have I successfully transformed the orange into a banana? --Lambiam 10:15, 5 February 2021 (UTC)[reply]

No, but it's a poor analogy, because the banana mush doesn't actively manufacture more banana structure and banana metabolism proteins, whereas human genes inserted into a non-human cell do generate human-cell proteins and might indeed, if done right, cause the cell to transform into a human zygote.

That said, while I concur with Bugs' "maybe", Futurist110's proposal of using non-human cells apparently adds pointless difficulty to the exercise: why, in the real (future) world would one use non-human cells when human cells would surely be available? Well, Futurist110 is (I understand) kicking around ideas for a science fiction novel, so there might be plot or background details that necessitate it, such as the exploitation of a loophole in laws forbidding human zygote gene editing. {The poster formerly known as 87.81.230.195} 90.200.40.9 (talk) 23:19, 5 February 2021 (UTC)[reply]

Calculating the distance range of commercial over-the-air FM radio stations

Now, I know the internet is full of forum questions of similar types, where people are being answered there would be too many undefined variables in their question than to really give an answer. However, I'm trying to find a simple online calculator (or maybe a formula, but I'm afraid it won't be easy to calculate on paper) for the following given specific conditions:

Let's assume we have a fully flat area for hundreds and hundreds of square miles, like a desert or prairie, without any forests, hills, or mountain obstacles.
We have a number of FM radio towers. Each being a simple, omnidirectional isotropic radiator, which sets antenna gain at 0dB on the transmitter side. They all broadcast at or around a frequency of 100 MHz. The towers only differ in height and watt power.
We know the exact individual height of every tower above sea level (in metric MASL), ranging between c. 60 to c. 250 meters.
We know the individual watt power of every tower, ranging from 0.01 kW to 20 kW.
The receivers are simple car or home kitchen radios with small whip antennas (which probably gives them an antenna gain of c. 2 to 3 dB), all at c. 1 to 2 meters above ground.
We define the limit of transmission range as the area within which the signal quality or strength for the receivers does not drop off below 50dBuV per meter.

So, what I'd like to calculate would be the individual distance range of every single tower, based on those factors and atmospheric path loss, while ignoring specific weather conditions. And no, I'm not asking about radio aka radar horizon, as that limit is most likely far above the capacities of those towers, anyway. --46.93.157.63 (talk) 23:48, 4 February 2021 (UTC)[reply]

Since you already give a strength limit of 50dBuV per meter a lot of your other assumptions are not required. So your volts per meter, can convert to watts per square meter (V/m)²/377, which for you is 2.65×10⁻¹⁰. You can then work out the size of the sphere 4πR² so your power flux: P/(4πR²) > 2.65×10⁻¹⁰. Substitute your transmitter power in P and solve for R. For 10000 watts I get 1730 km. This may sound big, but don't forget that the Earth is curved and there are hills and trees that absorb. So reality will be less. Due to reflection from the ground, the signal can also be doubled in some places, (and zeroed in others). Also consider that the transmitter will not be isotropic, and will avoid transmitting power down into the ground, and up into the sky. Graeme Bartlett (talk) 00:57, 5 February 2021 (UTC)[reply]

This does not take the path loss into account that is due to signal attenuation in the atmosphere. I further notice that Friis' transmission formula involves the wavelength, so presumably this should be of some significance. --Lambiam 10:09, 5 February 2021 (UTC)[reply]

Yeah, I was about to say that quite a lot of sources and websites make a huge deal out of path loss, Friis formula, wattage, and antenna gain (both on the transmitter and the receiver side), and there are even some websites with tables that claim you can calculate range from kW and HAAT, such as [11] ("How far will my signal go?", source: professional electronics dealer Broadcast Warehouse), and [12]. (Granted, with the first website, the power wattage examples are much smaller, and with the second, the figures are for highly directed transmitters.) (Although some sources claim you have to convert kW into effective radiated power first, not the actual power used or emitted, and that the results from kW (or ERP) and HAAT would be officially grouped into so-called "station classes" designated by the FCC, such as A, B, C, etc., where each FCC "station class" would equal a broadcast range class.)

To the contrary, quite a lot of *OTHER* sources even pretty much claim in response to "How many miles per watt?" questions that power wattage would have no impact at all once you have a tower, and then you could simply take the height of the tower in feet, and 75% of that or so would be the range in miles, acting as if 1 Watt would carry all the way to the radio horizon unchanged once you're 20 feet high. That's rather confusing, as you seem to have radicals on both sides: There seems to be a camp that says HAAT would be everything, and then there's a camp that says it would be entirely up to path loss, Friis formula, wattage, and antenna gain. And all over the internet, both camps seem to be entirely ignoring the other camp's existence, actively denying that the factors given by the other camp have much of any effect at all upon range, or they say those other factors would be far too diverse in real life that you can't really calculate them.

Anyways, from loooooooots of googling and reading, I've found two different solutions to my problem:

a.) Nautel’s Radio Coverage Tool: [13] It's free (though requiring registration). All you have to do is pick your location conveniently from a global map, then enter frequency in MHz, power wattage in kW, HAAT, and pick your type of receiver, and there you go. The thing has access to massive databases of global terrain data to calculate and draw your actual range as a circle around your tower on a map for you at the click of a button. You can also additionally download Google Earth to make the results look really neat, make even more realistic range calculations, and do lots of other stuff.
b.) I've found that there are official, publicly accessible FCC databases for pretty much every single commercial FM station in the USA that also list ranges in miles for every single station. Wikipedia even has a short list like that on its own at List of North American broadcast station classes#Station class description (where Wikipedia even claims that you can calculate ERP from HAAT and kW somehow, though without giving a formula). Unfortunately, no such official lists seem to be available for Germany, which is the actual area I'm trying to find this out for, and when you google for terms such as "FM radio technical broadcast range" in German, all you'll get is results not in miles, but in number of potential listeners, as if listeners would be the official physical electronic measure unit of "technical range". However, I've now come upon an amateur website where thousands of radio enthusiasts have reported FM bandscans from all over Germany to, and the site has used that data to draw rather detailed, confusing maps with ranges depicted as circles, either for every commercial or public broadcaster or for every radio tower used by that station, and are listing the rough broad range radius of every single station or tower derived from all that amateur data also in rough numerical values of kilometers. --46.93.157.63 (talk) 14:07, 5 February 2021 (UTC)[reply]

February 5

Substance in cardoon stalk

I boiled an cardoon stalk. The boiling water, after the addition of vegetable bouillon cube (therefore substantially salt, glutamate and flavorings), was kept in the pot for a few hours, and from clear as it was (slightly yellowish, color substantially due to the addition of the bouillon cube) has turned green! I would have expected to find at the limit a brown liquid, almost black, having had all the time to oxidize, but that color just I would never have expected. To which I think: "... is it pH sensitive?" (the cooking water is particularly calcareous, so the broth should be slightly basic). I add a splash of lemon juice and the broth turns yellow. And adding baking soda turns green again. And here is the question: which substance (or chromophore group) could be responsible for the color change? --87.0.134.53 (talk) 10:26, 5 February 2021 (UTC)[reply]

It's most probably one or more anthocyanin responding to the pH change. Roger (Dodger67) (talk) 14:18, 5 February 2021 (UTC)[reply]

Per Roger, some pigment or combination of pigments is responsible. Anthocyanins are generally blue/red indicators (antho=red, cyan=blue), while something like Curcumin is a yellow/red indicator (the main coloration of turmeric). I am not familiar with a "yellow/green" indicator natural to plants, but clearly they exist. Not sure what specific chemical these are in this case, but such types of compounds are common enough. --Jayron 32 14:25, 5 February 2021 (UTC)[reply]

Carbon emission of rail vs air

If you look at the greenhouse gas emissions of the whole system over a period of time (for example 50 years), are electric trains still much better then air travel? Has this been modelled? 2A02:C7F:C42F:6400:E1C2:D924:23F8:470E (talk) 17:18, 5 February 2021 (UTC)[reply]

Cecil Adams provides a nice overview to this question here.

I believe the paper he mentions at the start of the article is this one. I think that paper, and its citations could provide a very detailed answer to your question. ApLundell (talk) 19:14, 5 February 2021 (UTC)[reply]

Wikipedia has an article on Environmental impact of transport.--Shantavira|^{feed me} 10:28, 6 February 2021 (UTC)[reply]

"A journey from London to Madrid would emit 43kg (95lb) of CO2 per passenger by train, but 118kg by plane (or 265kg if the non-CO2 emissions are included)... The increased warming effect other, non-CO2, emissions, such as nitrogen oxides, have when they are released at high altitudes can also make a significant difference to emissions calculations". BBC: Climate change: Should you fly, drive or take the train?. Note that in Western Europe, most main rail lines are electrified, a majority of which comes from low-carbon generation. Alansplodge (talk) 12:30, 6 February 2021 (UTC)[reply]

Whilst I certainly don't disagree rail travel is better than air travel, I wonder if the emissions comparisons are complete. There's probably a reason these comparisons are always between two well connected capital cities. For instance, generally rail travel from anywhere in the UK outside the Southeast/London area to anywhere on the continent outside the Paris/Brussels corridor will be a two day affair, requiring a hotel stay either in London to catch an early Eurostar, or somewhere along the way on the continent. I doubt the comparisons take into account the extra emissions from the hotel stay etc. Like I said, I very much doubt that would make a difference in the long run, but I do wonder. That is an issue in wider adoption of international train travel from the UK though, for instance, it would take twice as long and cost three times as much for me to make my most regular UK-Europe journey, that's just not feasible in many circumstances. Fgf10 (talk) 14:57, 6 February 2021 (UTC)[reply]

That seems to ignore the possibility of sleeping on overnight trains. Are sleeper cars not a thing any more? It's been a while since I've done it. 2602:24A:DE47:BB20:50DE:F402:42A6:A17D (talk) 18:19, 6 February 2021 (UTC)[reply]

Not many of those left, although there is a movement for their renaissance. Fgf10 (talk) 19:40, 6 February 2021 (UTC)[reply]

February 6

Why would black holes emit Hawking radiation?

Even light can't escape black holes, then how it can emit Hawking Radiation? Rizosome (talk) 01:42, 6 February 2021 (UTC)[reply]

The second and third paragraphs of the overview section of the article you linked explain it. Matt Deres (talk) 04:10, 6 February 2021 (UTC)[reply]

Melatonin research journal

Does the journal "Melatonin Research" (example article) look any good? Not necessarily for Wikipedia RS purposes but as a research outlet? Thanks. 2602:24A:DE47:BB20:50DE:F402:42A6:A17D (talk) 18:17, 6 February 2021 (UTC)[reply]

It seems to be a new journal. The website design is... basic, but a quick scan of the author guidelines looks reasonable. Having say that, it's not in Medline, or has an impact factor yet. Also, most of the papers seem to be from developing countries. That in itself is not an issue, but when you see that exclusively it becomes a warning sign. (Note: this is not to say there is anything wrong with science from developing countries, but it is a hallmark of many a dodgy journal.) Many of the authors do not have institutional corresponding addresses. Another warming sign. A quick scan of randomly selected papers shows acceptance is universally within 3-6 weeks of submitting, suggesting the peer review is likely to be perfunctory (you'd expect some papers to have been sent back for extra work and several months between submission and acceptance). I can't judge the science, it's not my field. But at best I'd classify it as a new start-up journal which has yet to prove itself. Nothing I would sent any serious work in to. Fgf10 (talk) 19:55, 6 February 2021 (UTC)[reply]

Thanks, yeah, I had similar doubts, though I didn't spot nearly as much as you did. What do you think of the entire concept of a melatonin journal? Is that something like a Vitamin C journal? 2602:24A:DE47:BB20:50DE:F402:42A6:A17D (talk) 20:39, 6 February 2021 (UTC)[reply]

Kiwifruit with hollow or missing core

I have been eating kiwifruits more or less regularly the last 30 years, but cannot recall ever having seen a kiwifruit with a hollow – or missing – core. But in the box of kiwifruits I bought the other day I have so far seen two such fruits. See image. Is this normal? Are these fruits edible? --Andreas Rejbrand (talk) 19:42, 6 February 2021 (UTC)[reply]

Did you ask your grocer? And remember this motto: "If in doubt / Throw it out." ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:52, 6 February 2021 (UTC)[reply]

One of the pics on the article you linked is also hollow. Perhaps it's a varietal thing? The rest of the fruit seems pretty normal to me; I'd just eat it (assuming it tastes/smells normal and is not otherwise moldy/mushy, etc.) Matt Deres (talk) 03:15, 7 February 2021 (UTC)[reply]

February 7

Do Earth observatories better than space telescopes?

Do Earth observatories better than space telescopes? Even first Black hole image was produced by using observatory. Rizosome (talk) 02:17, 7 February 2021 (UTC)[reply]

Define "better". ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:19, 7 February 2021 (UTC)[reply]

Also, the image was produced by a global set of radio telescopes, as this NG article explains:[14] ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:58, 7 February 2021 (UTC)[reply]

This is largely explained at space telescope. You can often find the answers to your questions more quickly by doing even a tiny bit of searching. Matt Deres (talk) 03:09, 7 February 2021 (UTC)[reply]

Matt Deres I am comparing two things. Rizosome (talk) 06:22, 7 February 2021 (UTC)[reply]

If Earth observatories were indeed "better" than space telescopes, why do you think would anyone spend millions of dollars on developing them? Earth observatories and space telescopes are used for different purposes, so you do indeed need to specify what you mean by "better" if you want a meaningful answer, but it would be easier to actually study the articles, and then come back with a more specific question.--Shantavira|^{feed me} 09:29, 7 February 2021 (UTC)[reply]

What is the diagonal line in this satellite image?

In this satellite image, there is a long straight diagonal line in the upper left corner cutting across a headland of the westernmost island and with a slight but abrupt and arbitrary change of shade all across it. What does it represent? Is it natural? StellarHalo (talk) 06:04, 7 February 2021 (UTC)[reply]

Even at high resolution, I can't see what you describe.--Shantavira|^{feed me} 09:32, 7 February 2021 (UTC)[reply]

I can see a line heading away from the island on a bearing of about 7 or 8 degrees (i.e. slightly to the east of north), if that's the one? It's rather faint, so much so that I wonder why it is of concern? I suspect it's natural, but how to tell? PaleCloudedWhite (talk) 09:46, 7 February 2021 (UTC)[reply]

So that island is Ushant, yes? I can also see a lighter line, which crosses the island, at about 15 degrees from due North. I suspect it's an artefact of the image construction. Either that or maybe a secret underground tunnel between France and Plymouth. Martinevans123 (talk) 10:00, 7 February 2021 (UTC)[reply]

You're right about the heading - I misread my protractor. I suspect that the tunnel theory is going off at a bit of a tangent though (pun intended), even by my standards of protractor competence.... PaleCloudedWhite (talk) 10:13, 7 February 2021 (UTC)[reply]

You can thank my trusty perspex school protractor.... What, no tunnel?? I'll have you know I "put the ys in Wikypedya". Martinevans123 (talk) 10:32, 7 February 2021 (UTC)[reply]

The line is there, but I think it's an artefact. Sentinel-2 tells us the satellite is in a sun-synchronous orbit with a descending node at 10:30 local mean solar time. That means that the satellite made a pass to the SSW in the morning or to the NNW in the evening. Shadows clearly indicate this picture was taken during the morning pass (it would be after sunset in the evening). So the line appears to be parallel to the satellite's ground track. Maybe some effect in the detector? Or, Sentinel-2 scans a strip 290 km wide and the image, when measured perpendicular to the line, is about 180 km. Maybe the northwestern most part was filled in from a different observation? Sentinel-2 (consisting of 2 satellites) makes 1 or 2 scans of this area every 5 days. PiusImpavidus (talk) 10:37, 7 February 2021 (UTC)[reply]

I see a long line, going from the left to the top edge of the image and cutting through the eastern headland of Ushant at a bearing of 21°, and another one, much harder to detect, passing between the two ships close to the upper left corner at a bearing of 16.6° (assuming "up" is true North). Can these be an artifact of image stitching? I cannot think of a plausible natural origin. --Lambiam 10:42, 7 February 2021 (UTC)[reply]

Oh dear, my trusty school protractor has just delaminated. Martinevans123 (talk) 10:53, 7 February 2021 (UTC) [reply]

@@ Line 222: / Line 222: @@
 :The line is there, but I think it's an artefact. [[Sentinel-2]] tells us the satellite is in a sun-synchronous orbit with a descending node at 10:30 local mean solar time. That means that the satellite made a pass to the SSW in the morning or to the NNW in the evening. Shadows clearly indicate this picture was taken during the morning pass (it would be after sunset in the evening). So the line appears to be parallel to the satellite's ground track. Maybe some effect in the detector? Or, Sentinel-2 scans a strip 290 km wide and the image, when measured perpendicular to the line, is about 180 km. Maybe the northwestern most part was filled in from a different observation? Sentinel-2 (consisting of 2 satellites) makes 1 or 2 scans of this area every 5 days. [[User:PiusImpavidus|PiusImpavidus]] ([[User talk:PiusImpavidus|talk]]) 10:37, 7 February 2021 (UTC)
 :::I see a long line, going from the left to the top edge of the image and cutting through the eastern headland of Ushant at a bearing of 21°, and another one, much harder to detect, passing between the two ships close to the upper left corner at a bearing of 16.6° (assuming "up" is true North). Can these be an artifact of [[image stitching]]? I cannot think of a plausible natural origin. &nbsp;--[[User talk:Lambiam|Lambiam]] 10:42, 7 February 2021 (UTC)
+::::<small>Oh dear, my trusty school protractor has just [[Six degrees of separation|delaminated]]. [[User:Martinevans123|Martinevans123]] ([[User talk:Martinevans123|talk]]) 10:53, 7 February 2021 (UTC) </small>