Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

• Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
• Post your question to only one section, providing a short header that gives the topic of your question.
• Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
• Don't post personal contact information – it will be removed. Any answers will be provided here.
• Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
• Note:
  • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
  • We don't answer requests for opinions, predictions or debate.
  • We don't do your homework for you, though we'll help you past the stuck point.
  • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

• The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

February 27

Detergents

Manufacturers produce and market an array of detergents that supposedly are designed for different purposes - such as washing-up liquid, laundry liquid, floor cleaner, wooden floor cleaner, multi-purpose cleaner, toilet cleaner, shower cleaner etc. Yet when I look at the ingredients on different products, they seem to contain basically similar ingredients, namely surfactants (some kind of blend of anionic and/or non-ionic and/or amphoteric), water, perfume, preservative, and maybe a mild acid (presumably to tackle limescale) and something anti-bacterial. Is there really a significant difference between these products labelled for different purposes, or is it mostly a marketing ploy? PaleCloudedWhite (talk) 11:16, 27 February 2021 (UTC)

The article Laundry detergent lists quite a few ingredients that are peculiar to laundry needs, including enzymes. Phosphates in detergent have been banned. Laundry detergent and dishwashing soap for machines have anti-foaming agents. Hand dishwashing soap has been reformulated to prevent dishpan hands, which I used to experience but no longer. And I can attest to a noticeable difference between brand name laundry detergents such as Tide (known to be better by shoplifters everywhere) and cheaper generics. Abductive (reasoning) 18:18, 27 February 2021 (UTC)

If you live in an area of high water hardness, the reported anecdotal evidence for such a difference may be largely due to the absence of water softeners such as zeolites in your cheaper generics.  --Lambiam 09:14, 28 February 2021 (UTC)

Thanks. So it seems there are some differences, particularly regarding laundry cleaners. Though the differences between other products don't seem especially large, and to a certain extent many of the various products seem interchangeable on a day-to-day basis, e.g. the brand of washing-up liquid that I use seems just as effective at cleaning bathroom surfaces as the 'shower cleaner' that I bought, indeed it seems more effective, as it produces more lather and I therefore use less of it. PaleCloudedWhite (talk) 09:03, 1 March 2021 (UTC)

Some janitors I know swear by oven cleaner for cleaning bathtub scale and soap scum, as these are not responsive to detergents. Abductive (reasoning) 20:38, 1 March 2021 (UTC)

Lots of Google results for using white vinegar to dissolve limescale. Alternatively you could by a bathroom cleaner which includes an acid pre-mixed with detergent, which seems a lot easier to me. Alansplodge (talk) 14:11, 2 March 2021 (UTC)

Easier than spraying oven cleaner on the bathtub and walking away? Abductive (reasoning) 16:00, 2 March 2021 (UTC)

Maybe, I'll give it a try. Alansplodge (talk) 16:38, 2 March 2021 (UTC)

February 28

Question about a particular deadly condition for old people

What is the condition called where an old person's blood circulation stops working properly and this old person begins needing blood thinner and this old person's various organs and body parts also gradually begin to give out as a result of their poor blood circulation? Futurist110 (talk) 05:27, 28 February 2021 (UTC)

Are you talking about Congestive heart failure? ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:01, 28 February 2021 (UTC)

Probably Atherosclerosis.--Wikimedes (talk) 07:19, 28 February 2021 (UTC)

Or perhaps Peripheral artery disease? If properly treated (possibly including a change in lifestyle), the prognosis is not particularly bad, though. Poor blood circulation can arise as a result of several medical conditions, including (obviously) the already mentioned congestive heart failure, which in turn can have a variety of underlying causes. While statins may be prescribed, they are not blood thinners. Blood thinners may be prescribed if the underlying cause is coronary artery disease – not so much to improve circulation, but specifically to counter the formation of blood clots in the coronary arteries.  --Lambiam 08:18, 28 February 2021 (UTC)

Quantum Entanglement

I am clearly getting in the area where I don't belong, however, the issue bothers me. A couple of years ago an experiment was conducted to prove the quantum entanglement "once and for all." I first ran into the description in the Amazon documentary "Einstein's quantum puzzle" or similar. It is in their Prime Video section. Then there are two descriptions, one by the Austrians [1] who did the experiment, the other by MIT people [2]. The Prime Video channel provides a nice animated diagram, very helpful. In short, they needed two random numbers generators that must be totally independent. They found them in signals from two quasars on opposite sides of the sky, as they said in the opposite sides of the Universe. The distances to the quasars were enormous. They have their reasoning about it, which you can read there. The problem is that they say that those two quasars, to have been created in a very young Universe, never shook hands with one another physically because of the enormous distance between them. They implicitly assume that the history of quasars began at the time of their creation.

I don't think it is correct. In the very early Universe in the first billionth of a second or so there were quantum fluctuations that deformed the universe or perhaps parts thereof which eventually resulted in appearance of those two quasars. It is possible that both areas which much later became those quasars were subjected to the same pressure fluctuations because of the small size of the Universe at that time.

I also can offer a solution for the random number generators for this experiment. They got the computer numbers by some conversion of light signals which are constantly in a flux. They should have selected a small sequence of numbers e.g. 100 from one quasar and tried to find a match (or better a simple correlation) of this sequel in another quasar. Then they had to do such comparison with a slightly larger sequence, perhaps 110 numbers from the first quasar, etc. After repeating this numerous times they could prove total independence of the sources.

I wonder it all makes sense? AboutFace 22 (talk) 21:19, 28 February 2021 (UTC)

You're asking good questions. Bell's inequalities rely on a "no-conspiracies" assumption that's difficult to pin down exactly. See [3], [4] for some discussion. The version of the experiment that uses quasars as a source of random numbers can't completely eliminate this loophole. However, it can say that the "conspiracy" that could fool you would have to be on the scale of the entire universe and lasting many billions of years. From an MIT press release [5]:

“If some conspiracy is happening to simulate quantum mechanics by a mechanism that is actually classical, that mechanism would have had to begin its operations — somehow knowing exactly when, where, and how this experiment was going to be done — at least 7.8 billion years ago. That seems incredibly implausible, so we have very strong evidence that quantum mechanics is the right explanation,” says co-author Alan Guth, the Victor F. Weisskopf Professor of Physics at MIT.

The version you describe, going back to the quantum fluctuations that seeded the structures that went on to form the quasars, is something like superdeterminism. It may be impossible even in principle to rule this out. Your idea about comparing 100 random numbers doesn't help, because the kind of correlation relevant to the Bell-type experiment is a three-way one that would involve the two quasars and the experimental results on Earth. It would not necessarily produce a correlation between the two quasars alone that could be detected by any possible statistical test. --Amble (talk) 18:19, 1 March 2021 (UTC)

A little more about looking for correlations in the quasar signals... No statistical test of the quasar signals could eliminate the loophole, even in principle. That’s because it’s not about whether the quasar signals themselves are correlated. They could be perfectly good, completely independent random numbers. The loophole is about whether the experimental apparatus on Earth and the entangled particles could somehow already “know” those numbers before they arrive. It’s like a one-time pad in cryptography. There is no test you can perform on the secret key that can tell you whether your enemy has somehow managed to get a copy. —Amble (talk) 17:01, 2 March 2021 (UTC)

March 1

A stationary object in outer space

Is it meaningful to refer to "a stationary object in outer space" in our buoy article? Is it nonsense or is there a better way to express the idea?--Shantavira|^{feed me} 11:12, 1 March 2021 (UTC)

This appears under Buoy#Other:

• The space buoy is a common element in science fiction that refers to a stationary object in outer space that provides navigation data or warnings about that particular area.

Whether or not it belongs in our article, it is a common element of science fiction.

And you needn't get hung up on "stationary" as suggesting some privileged frame, as it is instead shorthand for a an object which propulsively (via whatever science-fictiony method) maintains a relatively fixed position with respect of some other bodies.

Here's a NOAA page which speaks of DSCOVR (The Deep Space Climate Observatory which maintains position at the Sun-Earth L₁ Lagrange point) as, "acting as a solar storm buoy in deep space." -- ToE 12:56, 1 March 2021 (UTC)

Thanks Thinking of England. So there really is a "space buoy". That's quite interesting and I'll give some thought to working that into the article.--Shantavira|^{feed me} 13:46, 1 March 2021 (UTC)

I don't believe it's a commonly used phrase for Lagrange point satellites, but here is NOAA again, in their "50 Years of Science, Service & Stewardship" 2020 publication.

Most of the definitions for the term space buoy read as follows: a common element in science fiction that refers to a stationary object in outer space that provides navigation data or warnings.

This, while true, leaves out an important fact: space buoys are real. Since 2016, NOAA's Space Weather Prediction Center (SWPC), one of the National Weather Service's (NWS) National Centers for Environmental Prediction, has been receiving data from its own space buoy -- the Deep Space Climate Observatory, or DSCOVR -- to help the agency monitor space weather.

...

See page 72 of this document. (Page 76 of the PDF itself.)

Funny, as I assume that their "most of the definitions" definition originated with WP! -- ToE 17:23, 1 March 2021 (UTC)

Here's a link directly to that one article. -- ToE 17:24, 1 March 2021 (UTC)

As far as the science fiction usage, its a "In popular culture" type reference, which could be hard to source.

Here's the Memory Alpha entry: Space buoy (which I assume we do not accept as RS). Interestingly, it does not mention Spectre of the Gun, where our very own article uses the phrase in question. -- ToE 17:30, 1 March 2021 (UTC)

Why can't snow melt here?

Recently USA Texas people posting videos about ice can't melt instead it turned black:

“You’ll see it’s not melting and it’s going to burn. Snow don’t burn. Snow f***ing melts. No water, no dripping, no nothing.

Source

Why can't snow melt here? Rizosome (talk) 13:34, 1 March 2021 (UTC)

The article you linked explained the effect; there's a combination of soot forming from the fire source, and that they aren't waiting long enough for significant melting to occur. Also, there are some faked videos as well. All of that is already explained in the page you linked. --Jayron32 13:39, 1 March 2021 (UTC)

Ice/Snow is surprisingly hard to melt quickly. "XKCD-What If" discusses the math behind why that is. The small drips that do form are probably either absorbed by the snow or boiled off by the flame.

As for the blackness, that's just soot from the lighter. Lighters not not the most efficient flame source in the world, and some of the fuel is only half-burnt. Try pointing it at sheet of glass. Same result. A hotter, cleaner flame wouldn't leave a mark. ApLundell (talk) 04:59, 3 March 2021 (UTC)

March 2

Colliding EM waves and energy conservation

Please refer to the image.

I create 2 EM waves by the simplest method - moving 2 charged objects back and forth once.

Both E and B fields values are opposite to each other. That is, at any given time, if in wave 1 B=a and E=b, than for wave 2 at the same time B=-a and E=-b.

Problem - At the instance both waves overlap they cancel each other completely.

This cannot be - It breaks conservation of energy.

What is answer to this seemingly contradiction?

I asked this question a while ago, got a horrible (and partially wrong) answer that I didn't think through. The false claim in the answer was that the drawings are irrelevant. This is wrong: at any given moment E and B fields have a distinct value at any point in space, and this is what the drawing depicts.

אילן שמעוני (talk) 05:32, 2 March 2021 (UTC)

The drawing is not "irrelevant", but it's underspecified. Taken literally, it seems that you're giving the E and B fields at one instant in time, and only on two line segments. In that case, the total energy is zero, and nothing measurable happens.

Probably that's not what you really mean, but I can think of at least two other things you might mean. If you'd be more precise about exactly what you do mean, someone might be able to answer your question, or you might find out you've answered it yourself. --Trovatore (talk) 05:58, 2 March 2021 (UTC)

I fail to understand what you mean by "...and only on two line segments.". If you refer to that the B and V values are only supplied for the waves, just assume we do this in intergalactical space where the background B and V values are negligible. If you refer to that I only measure values along this single axis and ignore that the waves are in fact 3D - this is true but I can't see why it's relevant.

Please note that the test is conducted after the situation depicted in the image, where both waves advanced to the point they overlap.

I'll rephrase - what data regarding B and V values you seek that is absent from the drawing?אילן שמעוני (talk) 07:27, 2 March 2021 (UTC)

I'm not sure where V came from; before you were talking about E and B.

The reason it's relevant that you only measure values along a single axis is that Maxwell's equations are three-dimensional. How are you going to compute a curl in one dimension?

So the information I'm missing is, what are the E and B values at all other points in space? Let's say the direction you're taking to be the direction of propagation is the z-axis. What is the dependency on the x- and y-coordinates, and what are the values of E and B at z-coordinates other than those of the two wave packets you show? --Trovatore (talk) 07:44, 2 March 2021 (UTC)

My bad, it's E, not V.

Mmmmm, I think I understand your question and can not answer it (last time I dealt with cross-products and calculus was 30 years ago), BUT I can't see why this matters to energy conservation.

Energy is supposed to be conserved for any volume without flow of energy in or out.

This true for a volume as small as you wish around the overlapping segment on the z-axis. We can reduce the x and y coordinates around this segment to our liking, and the E and B values will converge to zero.

In the same manner - flow of energy in and out of given volume requires time. Since we talk abot the instance of overlapping, we can again reduce the interval around measurement, and the flow will converge to zero.

I suspect that somehow the cross product that dictates E and B is such that they cannot both be opposites - that if for given time (for wave 1 E values are positive while wave 2 are negative) than (at the same time, B values for both waves must be equal). Buy I lack the knowledge how to check this. I only found how to check the values for moving charged particle, not for EM wave.

אילן שמעוני (talk) 12:14, 2 March 2021 (UTC)

Link to previous discussion: WP:Reference_desk/Archives/Science/2019_October_31#Destructive_interference_and_conservation_of_energy. You're still assuming you can choose a direction for the E field, choose a direction for the B field, and also independently choose a direction of propagation for the wave. This is not correct. They are related by a cross product as described in Poynting vector. Therefore, the direction of propagation shown in the right-hand half of your drawing is not consistent with the indicated E and B fields. --Amble (talk) 17:29, 2 March 2021 (UTC)

Ah, thanks, I missed that too. I was trying to figure out how the energy would get in and out of a standing-wave region — I think there's no speed-of-light problem per se, but the energy flow would increase without bound as the region got bigger, which seemed at the very least odd. But it's just the wrong picture. The energy doesn't need to go anywhere; it just sloshes back and forth between electric and magnetic fields. --Trovatore (talk) 20:58, 2 March 2021 (UTC)

So my suspicion was correct. Thanks. אילן שמעוני (talk) 19:24, 2 March 2021 (UTC)

Steel bollards on road - higher risk of accidents

Are there any scientific studies to what extent steel bollards on the streets increase the risk of accidents?

The type of bollards I'm talking about: https://www.bz-berlin.de/data/uploads/2019/05/radweg_1558535427-1024x576.jpg --88.78.14.45 (talk) 15:51, 2 March 2021 (UTC)

Probably decrease the risk of accidents at the expense of average vehicle speed. Abductive (reasoning) 16:02, 2 March 2021 (UTC)

It's worth considering what type of accident we are talking about. As positioned in the photo, it would appear that they are designed to prevent accidents involving a automotive vehicle hitting a bicycle or hitting a pedestrian. A moving chunk of metal vehicle, even at a gentle 40 km/h, hitting a pedestrian has a pretty large chance of killing said pedestrian. A vehicle moving at 40 km/h and hitting one of those bollards is unlikely to kill the occupants, especially if they are wearing seat-belts. On a risk/benefit analysis, I'd say that even if they somewhat increase the frequency of accidents as cars hit the things (cost), the benefit in eliminating a large portion of fatal accidents and replacing them with non-fatal accidents is high. --OuroborosCobra (talk) 17:14, 2 March 2021 (UTC)

Different types of barriers have certainly been studied. I don't know if you'll be able to find a paper on exactly the kind of barrier in that picture. They might not have been common enough long enough.

Here are some good starting points, though

• An insight into the performance of road barriers − redistribution of barrier-relevant crashes You'll need journal access for this one. Or you'll need to fork out $41.95
• Performance Assessment of Road Barriers in Indiana This one is free.

I really expected the NTSB to have something, but I could find anything. ApLundell (talk) 04:49, 3 March 2021 (UTC)

physical properties of octane isomers

I have searched for the following physical properties of octane isomers, "molar volume, total surface area and octanol-water partition coefficient", on internet but could not find anywhere, can any body help me to find it. — Preceding unsigned comment added by 182.187.18.182 (talk) 19:26, 2 March 2021 (UTC)

Before we run into an XY problem-type situation, can you elaborate the purpose for this information? If we know what larger problem you need this information for, perhaps we can better help you find the information that will help you. --Jayron32 19:30, 2 March 2021 (UTC)

This may be helpful for the octanol-water partition coefficient... I found n-octane and 2,2,4, trimethyl pentane. There are a lot of C8H18 compounds though. There's n-octane, 3 different methylheptanes, 2 different ethylhexanes, 6 different dimethylhexanes, and a bunch of pentane derivatives I don't feel like counting, plus your 2,2,4,4 tetraethylbutane. --Jayron32 19:42, 2 March 2021 (UTC)

The octanol-water partition coefficient article is too technical, in my opinion, and duplicates much of the information at partition coefficient (a much better article overall). The concept is very important in drug and pesticide design and chemists doing such work normally use the LogP as a vital parameter when comparing compounds within a given analogue series. Very many of Wikipedia's articles on commercial products of these types includes the LogP in the Chembox and there are online collections at repositories such as "The Pesticide Properties DataBase".. I have no idea why the OP wants the value for octane isomers but such values can be pretty reliably calculated when they have not been experimentally determined (see cLogP in the partition coeffficient article). Mike Turnbull (talk) 10:24, 4 March 2021 (UTC)

I have made a proposal to merge the articles and added the appropriate templates. Please comment at Talk:Partition coefficient#Merger proposal: Merge Octanol-water partition coefficient into this article if you wish. Mike Turnbull (talk) 10:37, 4 March 2021 (UTC)

To answer the OP's original question, many compounds in Pubchem have recorded data for their physical properties, so the the logP (octanol-water partition coefficient) is 5.18 [6], although our octane article says 4.783 without giving a specific source: it is probably a predicted value, since Chemspider agrees with Pubchem (the ultimate experimental source is MM Miller). No doubt Pubchem will have other isomers. Mike Turnbull (talk) 12:34, 4 March 2021 (UTC)

Higher taxa named after people

What higher taxa (from genus up to a family, order or higher, like Smithatris after Rosemary M. Smith) are named after people? Preferably full list, if available somewhere. 212.180.235.46 (talk) 23:58, 2 March 2021 (UTC)

Here's a query on WikiData: [7] that is as complete as the information on WikiData. It returns every taxon that's not at a low level (species, subspecies, variety, strain, or cultivar) and is listed as being named for something (not necessarily a person). There are quite a few genuses and some families named for people. There's a class arachnida named for the mythological person Arachne, and a phylum lokiarchaeota named for Loki's castle, so you can decide whether those count. This query doesn't return a fungal subdivision pucciniomycotina, which seems to be named for a Tommaso Puccini [8], although I'm not sure this is the right Puccini. --Amble (talk) 02:14, 3 March 2021 (UTC)

Ultimately, within taxonomic nomenclature, Pucciniomycotina gets its name from the genus Puccinia, which was established in 1729 by Micheli, named "in honor of Puccini, a Florentine professor".^[9] Its eponym cannot have been the art historian (not "professor of anatomy") Tommaso Puccini (1749–1811). Merriam–Webster states: "from Tommaso Puccini †1735 Italian anatomist".^[10] The bust shown in our article Tommaso Puccini is dated as being from 1718, and its sculptor died in 1725, so it also cannot depict the future art historian.  --Lambiam 09:17, 3 March 2021 (UTC)

Other sources give 1666–1726 for the anatomist, who reportedly studied with Lorenzo Bellini and was connected to the Hospital of Santa Maria Nuova.^[11][12]  --Lambiam 09:32, 3 March 2021 (UTC)

Well done. Do you think the anatomist is notable enough for an article? —Amble (talk) 15:16, 3 March 2021 (UTC)

He obviously was notable in his days, not only having a fungus named after himself (what was the connection there?) but also having a bust in marble by a famous sculptor as well as a medal with his effigy. The bust is in a museum in Pistoia and the inscription patrit(ivs) pistorien(sis) on the medal also connects him to Pistoia, which makes it likely he was a relative – perhaps the grandfather – of the art historian, a native of Pistoia. I also saw that the anatomist was included in the circle of friends of the painter Pietro Dandini.^[13] Nevertheless, altogether I did not spot enough material for an article.  --Lambiam 23:54, 3 March 2021 (UTC)

One more snippet: Villone Puccini aka "Villa Puccini" in Pistoia was built by the anatomist.^[14]  --Lambiam 00:26, 4 March 2021 (UTC)

Our page list of fungal orders lists kickxellomycota as a division; but kickxellomycotina is a subdivision and that page doesn’t list a division (“incertae sedis”). Whether division or subdivision, it’s named for Jean Kickx. I wonder whether this could be the highest example of taxonomic “promotion through the ranks,” where originally a genus was named after him, and the genus name eventually filtered up to (maybe) a division... —Amble (talk) 16:08, 3 March 2021 (UTC)

March 3

Is there a sea in europe of which its color is green rather than blue?

ThePupil (talk) 09:31, 3 March 2021 (UTC)

The apparent color of a body of water will depend on various factors, including what's in it, and what the sky looks like that day. ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:51, 3 March 2021 (UTC)

To expand on that, if the water is clear, then it will look bluish (especially if the sky is blue too), as water absorbs red light and scatters and transmits blue. Sediment or algae in the water tend to absorb other colours, making the water look more green (or brown, or grey). See Ocean colour for a summary, or here for more detail. The sea around the UK often looks greenish (or greyish) due to sediment in the water and an overcast sky. Iapetus (talk) 10:35, 3 March 2021 (UTC)

Colour variations are probably better expressed in smaller bodies of water with particular conditions, such as at the Blue Pool in southern England, where the colour varies between "red-brown, through grey and green, to the more typical turquoise". PaleCloudedWhite (talk) 12:31, 3 March 2021 (UTC)

Why coronavirus Indian vaccine “Covishield” is more demanding than “pfizer” which has more efficacy?

• India has undertaken contractual supplies of coronavirus vaccines to Saudi Arabia, South Africa, Brazil, Morocco, Bangladesh and Myanmar, the Ministry of External Affairs (MEA) said in New Delhi on Friday.

Source Why coronavirus Indian vaccine "Covishield" is more demanding than "pfizer" which has more efficacy ? Rizosome (talk) 12:05, 3 March 2021 (UTC)

@Rizosome: What do you mean by "more demanding"? If you saw the expression somewhere then please link to it. It's not used in your link. PrimeHunter (talk) 13:05, 3 March 2021 (UTC)

I'd guess that by "more demanding" what's meant is "in greater demand". Deor (talk) 18:51, 3 March 2021 (UTC)

Maybe, but a story about some poor countries getting a cheap vaccine doesn't indicate a greater demand. Looking at other posts by Rizosome, I guess we shouldn't expect much. PrimeHunter (talk) 19:16, 3 March 2021 (UTC)

Covishield is the Indian name for the Oxford–AstraZeneca COVID-19 vaccine. It is easier to store and distribute than the Pfizer–BioNTech COVID-19 vaccine which needs to be stored at very low temperatures. The Indian-developed Covaxin has been criticised by some because it was approved for emergency use by the Indian regulator before the clinical trials had been completed. See BBC - Covaxin and Covishield: What we know about India's Covid vaccines. Initial doubts about the effectiveness of the AstraZeneca vaccine in the elderly have been dispelled by recent data from the UK where it has been widely used; see Pfizer, AstraZeneca COVID-19 vaccines may offer high efficacy in elderly. Alansplodge (talk) 15:01, 3 March 2021 (UTC)

March 4

Why is Nyiragongo a stratovolcano?

Given the fluidity of its lava, why isn't it a shield volcano? ZFT (talk) 04:27, 4 March 2021 (UTC)

That's a good question, the neighbouring Nyamuragira is a shield volcano, although it erupts high potassium basalts. I've looked through this thorough review and I can't find a clear explanation - apart from the earliest stage eruptions, the volcano is dominated by lava flows. Mikenorton (talk) 09:04, 4 March 2021 (UTC)

Do astronomical observatories really shoot laser into sky like this?

Do astronomical observatories really shoot laser into sky like this? Here is the picture taken from Optical amplifier Rizosome (talk) 06:28, 4 March 2021 (UTC)

See laser guide star for an explanation of the technique - why would you doubt it? Mikenorton (talk) 08:44, 4 March 2021 (UTC)

In usual terminology, space observatories are observatories located in outer space. Observatories observing space (usually from the ground, but sometimes from space or even a high-altitude balloon, aircraft or from below the Earth's surface) are called astronomical observatories. And yes, sometimes they shoot a laser into the sky. Apart from lunar ranging, it's sometimes done for adaptive optics. Adaptive optics uses a deformable mirror to correct for diffraction of light in moving bubbles of air of different density. To measure the required corrections, the system has to observe a sufficiently bright reference star (much brighter than the object you're interested in). If no sufficiently bright star is available close enough to the object you want to observe, a laser can be used to project one in the higher parts of the atmosphere. Of course, they have to make sure they don't hit an aircraft passing over, as those lasers can be very annoying to pilots (just as aircraft can be annoying to astronomers). PiusImpavidus (talk) 09:02, 4 March 2021 (UTC) @PiusImpavidus: I changed my title, still your answer supports my question? Rizosome (talk) 13:46, 4 March 2021 (UTC)

Yes, that was already the question I answered. The laser-equipped observatories are always ground-based, not in the air, in space or below ground. Except gravitational wave observatories, which are laser-equipped and can be below ground, but don't shoot their laser beams into the sky. PiusImpavidus (talk) 16:35, 4 March 2021 (UTC)

The Royal Observatory, Greenwich has a similar laser, The Meridian Laser, which only serves to show the location of the Greenwich Meridian and has no scientific purpose beyond education. It's more of a museum than a working observatory, but one of their historic telescopes has been brought back into use recently. Alansplodge (talk) 15:30, 4 March 2021 (UTC)

Yes, I once saw that, when leaving the Maritime Museum on a winter afternoon/evening (after the fire alarm went off). PiusImpavidus (talk) 16:35, 4 March 2021 (UTC)

March 5

Seabird IDs

In this video, what are the cliff-nesting birds first seen at 23 seconds, and the tern-like birds at 3:30? --24.43.123.79 (talk) 00:19, 5 March 2021 (UTC)

Why Space X didn't reveal the reason behind SN 10 failure?

Why Space X still didn't reveal the reason behind SN 10 failure? Rizosome (talk) 02:49, 5 March 2021 (UTC)

Is that the one that blew up within the last day or so? ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:26, 5 March 2021 (UTC)

Maybe because they aren't yet completely sure what the reason was? Our article already says "due to a suspected methane leak." In any case, as a privately owned company conducting tests on prototypes, they are under no obligation to reveal their findings immediately, and will doubtless only do so when and if it becomes advantageous for them. {The poster formerly known as 87.81.230.195} 2.125.75.168 (talk) 06:20, 5 March 2021 (UTC)