Wikipedia:Reference desk/Archives/Science/2021 February 4

= 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)


 * 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)

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


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

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)
 * Yes. ←Baseball Bugs What's up, Doc? carrots→ 22:13, 4 February 2021 (UTC)
 * 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)
 * Maybe. ←Baseball Bugs What's up, Doc? carrots→ 01:57, 5 February 2021 (UTC)


 * 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)
 * 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)

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)


 * 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)


 * 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)


 * 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 ("How far will my signal go?", source: professional electronics dealer Broadcast Warehouse), and . (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: 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 (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)