Wikipedia:Reference desk/Archives/Science/2019 May 24

Science desk
< May 23	<< Apr | May | Jun >>	May 25 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

May 24

Which species of spider?

Can anyone identify this species of spider? Bubba73 ^{You talkin' to me?} 00:14, 24 May 2019 (UTC)

The yellow and black one is an orb spider. They are very common and go by many different local names. 97.82.165.112 (talk) 01:12, 24 May 2019 (UTC)

Thanks, I forgot to say that the second photo is its web. Bubba73 ^{You talkin' to me?} 01:25, 24 May 2019 (UTC)

Amazing web! In that case I would suggest it's an orb-weaver spider.--Shantavira|^{feed me} 07:46, 24 May 2019 (UTC)

See web decoration. Mikenorton (talk) 10:59, 24 May 2019 (UTC)

The top image shows the underside of possibly a wasp spider. Mikenorton (talk) 12:42, 24 May 2019 (UTC)

If the spider is not causing a problem for you, I strongly suggest leaving it alone. They are very friendly spiders that do a great job in controlling ground pests like grasshoppers. Plus, if you can get over the often grotesque appearance, they make very pretty webs. 12.207.168.3 (talk) 12:44, 24 May 2019 (UTC)

They're actually rather attractive, as spiders go. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:15, 29 May 2019 (UTC)

I doubt they object to being photographed. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:45, 24 May 2019 (UTC)

Just don't let them get their…legs? on any drugs. --47.146.63.87 (talk) 07:47, 27 May 2019 (UTC)

My wife called my attention to the interesting web. The spider behind the web (hardly visible) is the same one in the other photo. I have not bothered it. The photo turned out to not be as sharp as I wanted. I think I had the shutter speed too low. Bubba73 ^{You talkin' to me?} 19:00, 24 May 2019 (UTC)

I'm not a spider expert, but a quick web search (lol) suggests Argiope aurantia as a good match. PaleCloudedWhite (talk) 01:02, 29 May 2019 (UTC)

Having said that, the legs of A. aurantia don't seem to have the banded patterning as shown in your pic, and the web patterning is also different, so an alternative species could be Argiope trifasciata. PaleCloudedWhite (talk) 01:24, 29 May 2019 (UTC)

Is a single photons light particle emitted in every direction?

Or is a photon particle directed in one direction?

The question that my friend pondered is if we look at the sun, are we receiving the same photon particles or if he is receiving separate photons.

I read many pages on the subject but am still unsure.

Thank you.

107.199.78.194 (talk) 01:26, 24 May 2019 (UTC)

The probability that the photon will be encountered is emitted in all directions. Whether the photon "itself" is emitted in all directions seems to be a matter of interpretation. Some interpretations of quantum mechanics, like Bohmian mechanics, say a very clear no, while others, fulfilling the same math requirements (like Copenhagen interpretation) say yes.

However, in either case, the individual photon is a particle that might hit your retina or his, but not both. Wnt (talk) 02:00, 24 May 2019 (UTC)

As Wnt has hinted at, this is a question that sounds simple but is surprisingly deep. To restate your question: can the same photon interact with both your friend's eye and your own eye? If you look at things based on the classical photon model, which models the photon as a particle, the answer is a pretty simple "no". Things can't be in two places at once, silly! The problem is, we now know that classical mechanics is not "fundamentally" correct; it's just an approximation that works well under certain conditions. Quantum mechanics (QM) more accurately describes the world, but it does so in ways that defy our intuition. In QM, a photon is described by a wavefunction, and the wavefunction simply gives you a probability of finding the photon at any given point in space. So does that mean the photon is everywhere at once? It depends on how you interpret QM. All the math does is give you numbers. This is what the famous wave–particle duality is about: you can view a photon as either a wave or a particle, but in QM a photon isn't really either: sometimes it can behave like a wave, and sometimes like a particle. Some of the responses here may help give some more detail: [1] [2]. This might seem unsatisfying; you might want to know what a photon "really is". Well, it's a photon, which according to quantum field theory is an excitation in the electromagnetic field. It shouldn't really be surprising that it's difficult to visualize such things. Our intuition developed to survive on the savannah, not to figure out how photons behave. If you want to learn more about QM in general, try introduction to quantum mechanics for a starting point. There are some good books listed there in the bibliography. I also recommend PBS Space Time on YouTube. --47.146.63.87 (talk) 03:34, 24 May 2019 (UTC)

Oops, the bibliography is actually in the main quantum mechanics article. --47.146.63.87 (talk) 06:54, 24 May 2019 (UTC)

• "The question that my friend pondered is if we look at the sun, are we receiving the same photon particles or if he is receiving separate photons." The question is, as noted, quite interesting if you ask it in different ways. If a photon of light did hit your eye, it cannot hit your friends eye. That is a different question than will a particular photon hit your eye or your friend's eye. The answer to that is not intuitively similar to the past-tense question, and gets down to what may be the fundamental difference between classical mechanics and quantum mechanics. Classical mechanics presumes certain (what seems to us) rather obvious, axiomatic assumptions: objects have a defined location in space and time, and if you know an object's location, and you know the forces on that object, you can predict reliably how that object's motion will change over time. That is perhaps the fundamental set of axioms for classical mechanics; it is the assumption that one makes in nearly all first- and second- year basic physics classes. The key bit that makes quantum mechanics different than classical mechanics is that very first part "objects have a defined location in space and time". Imagine a world where they didn't. I don't mean "imagine a world where you can't know an object's location because you don't have good enough instrumentation." I mean "Imagine a world where an object's location is not itself a well-defined concept." Now, try to predict the results of interactions between those objects, or the results of forces acting on those objects. Imagine trying to predict the flight of a soccer ball you are about to kick where you don't know where the ball is, where your foot is, and when your foot will strike the ball. You do know when you have struck the ball, because, lets say, you can see the mark the ball leaves on a wall. But can you tell what will happen before the ball hits the wall and makes the mark? That's what quantum mechanics looks like in macroscopic terms. If you want to understand anything about your system (like, how kicking soccer balls works) in your quantum world, you need to kick a bunch of soccer balls, and look where they hit the wall, and extrapolate some equations that give some predictive power over the behavior of the soccer ball. That's basically what quantum physicists do... Take observations of quantum behavior and devise mathematics that reliably predicts it. In simpler terms: you need to define your question carefully: are you picking a photon that is leaving the sun and trying to predict who's eye it will hit? Or are you picking a photon that has already hit your eye, and asking if it already hit your friend's eye too? Only the second question has a single, defined answer: it hit your eye. The first can only be answered in terms of probabilities. --Jayron32 11:21, 24 May 2019 (UTC)

  Not to add to my rambling above, but there is another implied question here: "What is the photon doing as it travels between the sun and us before it hits one of our eyes". The answer to that question is entirely unknowable, and what gets to the heart of all of the debates regarding the interpretations of quantum mechanics: unless and until you make a measurement of that photon, you don't know what it is doing. And you can only make a measurement by bouncing that photon off of something. And that only tells you when and where that photon was at a particular point in time; all you did was move your eyes to a different location, you didn't gain any insight on what the photon did between the sun and your eyes. --Jayron32 11:34, 24 May 2019 (UTC)

  In for a dime, in for a dollar: adding to this yet again; above I use the word "location" and "localization" in a physical, Cartesian sense, defining it as (for example) a set of four coordinates (x, y, z, and time) in space and time. But in quantum physics, the term "locality" refers more generally to any measurement one can make of a quantum particle or of a quantum system. Location in space and time is a convenient one to discuss, but any measurable quantity is subject to the same indeterminacy. So when you read some of the articles I linked above, they tend to speak in more general terms about what "local" means; I use it above meaning "a physical location in space", but it really means "any measurement you could make". --Jayron32 11:43, 24 May 2019 (UTC)

Do not eat raw batter!

I bought a lemon-poppyseed muffin mix from Martha White at the store yesterday. At the bottom of the packaging, near the manufacturing company's mailing address and telephone number, is a disclaimer: Do Not Eat Raw Batter. Why? It's dry mix with nothing perishable (ingredients), "best by" some time next year, and one creates batter by taking muffin mix and adding milk. (If your milk's gone bad, it's your fault; but are they afraid of spoiled-milk-drinkers suing?) I can't envision anything in the ingredients that could be dangerous but that would be neutralized by fifteen minutes in a 400°F oven. Nyttend (talk) 05:00, 24 May 2019 (UTC)

Presumably because we're not supposed to eat raw flour.[3] DMacks (talk) 05:32, 24 May 2019 (UTC)

(EC) A quick search finds the FDA and the CDC recommend against the consumption of flour, raw dough and raw batter apparently due to the risk of E. coli from the flour (and in some cases which probably don't apply here Salmonella from the eggs). [4] [5] BTW, for anything that isn't too thick, fifteen minutes in a 400°F oven is more than enough to kill most bacteria although maybe not their spores and probably also won't do much for toxins already produced. If the internal temperature reaches even 75°C for a short while, that's enough for most things [6] so it really depends on the thickness and other factors as to how long it takes for the internal temperature to reach that. To be clear, this is only in relation to bacteria, there are other things that need to be considered for some foods e.g. Antinutrient or toxins that sometimes need to be dealt with, sometimes with cooking and I'm not sure whether an internal temperature of 75°C for a short while is enough for them. (Think cassava etc.) So it's not intended as generally food safety advice simply a comment on the "can't envision anything in the ingredients that could be dangerous but that would be neutralized by fifteen minutes in a 400°F oven" bit. Nil Einne (talk) 05:41, 24 May 2019 (UTC)

I believe the first major recall that brought this issue to prominence was the 2009 Nestle Toll House cookie dough recall where flour was the source [7]. I can't prove this but I don't think the possibility that E. coli could live in flour was something that had really been considered in the industry prior to this. Interesting side note, Nestle started heat treating their flour afterwards because they are aware that even though their packages say "Do not consume raw cookie dough", a large percentage of their customers will do it anyways. shoy (reactions) 13:59, 24 May 2019 (UTC)

I'm not convinced that was true e.g. [8]. It may be true it wasn't believed there would be anything to cause health concerns if you're just eating small amounts of raw flour (considering quantity and type expected to be present). Definitely the fact that there would probably be some bacteria in your flour doesn't seem particularly surprising even if the assumption may be that there won't be enough of anything of concern to be a problem. Remember that the non perishability of something like flour most likely comes not so much from the fact that there's no microorganisms on it, but from the water activity being way way too low to support any growth. If you were to wet your flour e.g. by putting it in a container+water that had been autoclaved, I don't think any competent microbiologist even from the 1960s would have been surprised to find bacteria growing it in that came from the flour. Nil Einne (talk) 15:19, 24 May 2019 (UTC)

The answer is: because the cost of ink on a label is cheaper than the cost of a lawsuit. --Jayron32 11:01, 24 May 2019 (UTC)

Boron_nitride#Cubic_form_(c-BN) cutter

I am trying to find a way to cut 5/16" stainless steel rod at work. At present we are using disc grinders. This is time consuming and needs a large working area. I am hoping to modify a nut splitter by adding a boron nitride cutting edge. The nut splitter I have ordered is: https://www.otctools.com/products/universal-c-frame-nut-splitter The CBN material I have ordered is: https://www.spyderco.com/catalog/details/204CBN/891 The CBN knife sharpeners appear to be hollow and thus will probably crack. Plan A is to fill them with powdered glass or ceramic glaze and then heat to melting. Issues: Will the glass/glaze expand and crack the CBN rods? How to I 'snap' the rods to approx. 1/2" length to fit the nut splitter? I thought of putting them in a vise and either whacking them with a hammer or snapping them off with stainless steel pipe; both methods using soft metal padding. Any other wise ideas about modifying a nut splitter or cutting stainless rod would be very helpful, and please feel free to invent this gadget so I can just buy it from you next time. 96.55.104.236 (talk) 16:53, 24 May 2019 (UTC)

I know nothing nearly practical enough to answer your question, but I can link to a cute video of a water jet cutter. Website [9] says coefficient of expansion of cubic boron nitride is 3.8 x 10^-6 deg C^-1. But figuring out the coefficient of expansion for a ceramic glaze looks like a fine art [10], complete with a reprise of our non-ideal solution issues from a week ago. I don't know what's on your table for this. Wnt (talk) 00:18, 25 May 2019 (UTC)

If you think filling the void with whatever will prevent the CBN part cracking, that is simply NOT true. Interference fit is serious mechanical business, unproperly done you have higher a chance to weaken the thing, than to strengthen it. So I wouldn't bother, and use it as is, the way it is used in a diamond anvil cell (that is, softer material around it).

But then again, if I were you, I would refrain from reinventing a manual disc grinder, because this is what you are doing now (and I see no way you manually turning your intended tool at ~10 rpm speed can compete with a 3000 rpm grinder). If disc grinder are really consumming too much working time, so much so that some investment are worth it, consider aforementioned water jet cutter or laser cutter, but I guess there are too expensive for you.

Sorry to ruin your groove, but good luck with it.

Gem fr (talk) 06:23, 25 May 2019 (UTC)

Thank you both for your input. The time and space factors are because the stainless steel rod breaks regularly on our dough proofer conveyor belts which causes an alarm and the belt stops. We only have 15 minutes to get the belt moving or we lose all the product in the proofer. The water jet would be a good idea if we could make one small enough to fit in tight areas. I will ask why the broken conveyor link sensors aren't mounted outside the machine and close to the maintenance shop or a place where we can keep a disc grinder and face shield stationed. 96.55.104.236 (talk) 15:18, 25 May 2019 (UTC)

Would a portable Shear, such like alligator shear, be too large? It does the job in a matter of seconds https://www.youtube.com/watch?v=5QSfqHld-XY Gem fr (talk) 20:09, 25 May 2019 (UTC)