Wikipedia:Reference desk/Archives/Science/2015 November 22

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November 22

Steel mill type

Judging by [1], Google aerial view at 41°34′24″N 84°2′35″W, and my picture, what kind of facility is the North Star BlueScope Steel mill near Delta, Ohio? Trying to figure out which subcategories of Commons:Category:Steel production I should use for the image. Nyttend (talk) 00:05, 22 November 2015 (UTC)

"Since 1997, North Star BlueScope Steel LLC has been providing hot rolled bands...". They also have furnaces (including an electric arc furnace) that input pig iron and other raw materials. That would make it a refinery, a foundry, and a rolling mill: it's a facility that takes in ore and raw material, melts it and mixes it to produce steel, and finally hot rolls the output steel to produce coiled sheet metal. Nimur (talk) 02:02, 22 November 2015 (UTC)

preserving ornamental squashes

Perty much every year I buy ornamental squash / pumpkins in mid-october as gifts. They are solid, hard, weigh only a few ounces each, and seem to be wax covered. Nevertheless, the ones I buy my mother are almost always mold-ridden by Thanksgiving. (I give the others away to store clerks I deal with regularly, they don't report on their demise.) Is there some way to preserve them by washing or heating or the like? Thanks. μηδείς (talk) 00:49, 22 November 2015 (UTC)

Regular washes in a dilute bleach/water solution (like a capful of Clorox bleach in a kitchen sink full of water)? When we buy fruit we do that to make it last longer, at my estimate we can about double the shelf-life of a 3 pound bag of mandarin oranges that way. --Jayron32 01:29, 22 November 2015 (UTC)

The enemy here is moisture. If the skin is not damaged and no part of the squash is exposed to constant moisture, it should last months without getting moldy. Looie496 (talk) 13:05, 22 November 2015 (UTC)

Location (location, location) is probably the key here. Just move your mom to Canada and the pumpkins will easily last from mid-October to Thanksgiving! Okay, more seriously, only getting a month on squash seems awfully short. Per Looie, moisture is the problem, so the place of storage is going to be key; keeping them in a bowl in the kitchen is a high-risk activity. Moisture from cooking and dishwashing will inundate the place (and roll out an invite for mold). You may also want to make sure that she's not sticking it in a bowl with fruit, such as apples or bananas. They outgas ethylene quite vigorously, aging the squash prematurely. 99.235.223.170 (talk) 13:28, 22 November 2015 (UTC)

Think the above have laid out the gist of the problem. Fruit waxing is a cheap and easy way to get produce from field to market but does not let the produce breath. Also, it allows the farmer to harvest before produce is fully ripe. I don't know if your familiar with Marrow (vegetable), my father used to grow them and keep them for winter. Pick only when ripe (when the skin has matured and hardened -and marrow skins are very thin), wash (bleach is OK – hydrogen peroxide may be better than chlorinated but I don't have any references) and store at a low temperature – not in the house. He placed them in a string-bag so that air could circulate and thus not encourage mold. Suggestion: Find a supplier from which to buy un-waxed squash. Bleach, dry, place in string bag and store at or below 10º centigrade. Just a little bit of salt and white pepper (not black pepper in this case) brings out the subtle flavor. Do please, let us know next year how you get on.--Aspro (talk) 17:27, 22 November 2015 (UTC)

Thanks for the above answers. Yes, I did actually consider the Canadian solution. And yes, she does keep them in a bowl on the kitchen table, but the bowl already has carved wooden 'fruit' in it, and the squash sit on top, and do not touch each other. Humidity is not a huge issue, since the house is rather dry--I have never seen any condensation. Most years the squash last until Christmas. I suspect the real problem is that they were allowed to get moldy at the store. I was going to buy some bigger and very bizarrely shaped bumpy multicolored melons, but they were already moldy on the stand. Next year I will wash them and dry them before putting them on the table. That might have prevented these going bad so unexpectedly quickly. Oh, and interesting about the marrow. We call them zucchini here. μηδείς (talk) 18:46, 22 November 2015 (UTC)

As was mentioned before, it can be more humid in the kitchen than the rest of the house, and it doesn't need to get to the point of condensation to promote mold. I'd make sure the ones you buy are rock hard. Also, you might consider getting fake squash to go along with the other fake fruit. Keeping live squash in the fridge when not on display might also help. StuRat (talk) 18:58, 22 November 2015 (UTC)

They are a rather cheap novelty item, so it is not a big deal. I was simply surprised they went so quickly this time. There were eight. Of the four still left I have noticed they are all getting soft on the bottom, so I expect they'll be gone by Turkey Day. I've never cut one open, so if there is one left perhaps I'll dissect it. Thanks. μηδείς (talk) 00:53, 23 November 2015 (UTC)

Waitaminnit. The "ornamental" nomenclature is just because they're neat to look at - why aren't you cooking them and eating them? I don't think I've ever found any that weren't perfectly edible, though some of them are difficult to cook evenly due to their odd shape. 99.235.223.170 (talk) 02:06, 23 November 2015 (UTC)

You can keep the same squash for several years if you dry them properly [2] [3]. SemanticMantis (talk) 15:25, 23 November 2015 (UTC)

Thanks. The drying methods linked to are basically for edible gourds grown at home. These gourds are very small (smaller than commercially sold apples) and have been "waxed" and the stems are dry; I suspect drilling holes in the bottom and hanging them outside might work. They are so small I doubt there would be enough pulp to eat; the smaller the fruit, the more rind and seeds in proportion. Perhaps I will cut one open after Thanksgiving dinner. I did give a rather large grapefruit-sized gourd to my physical therapist on my last day with her, she said that she would cook and eat it, but it easily massed 10 times what the ones I got for Mom's dinner table do. μηδείς (talk) 18:46, 23 November 2015 (UTC)

What would it feel like to stand on a planet with a really high speed of rotation?

Can anyone describe what it would feel like, for an average human, if one were standing at the equator on a planet the size of Earth, but this planet is rotating on its axis many orders of magnitude faster than Earth's rotation? Would one 'fly off into space'? Would one get squashed by inertial forces? Would there be any physical effects at all? Or would the person just see the stars whizzing by really fast? -- œ^™ 06:43, 22 November 2015 (UTC)

If Earth were to spin at more than about 18 times its present rate, nothing on the equator would stay down. I don't know what you mean by "squashed by inertial forces". —Tamfang (talk) 08:01, 22 November 2015 (UTC)

Actually the higher centrifugal force at the equator causes the spheroid to deform - expanding at the equator (increased oblateness) to maintain hydrostatic equilibrium. -- Roger (Dodger67) (talk) 08:48, 22 November 2015 (UTC)

Yes, exactly. The Earth shouldn't be considered as a solid 'thing' - it's a relatively loose collection of stuff held together by gravity. If the rotational speed were to increase, the particles at the equator that are experiencing more centrifugal force will move outwards somewhat and material from the poles would move inwards a little to fill the void. The earth would go from being a perfect sphere to becoming squashed a little. In fact, this has already happened and the earth is about 44 kilometers wider than it is tall.

So with increased spin, the shape of the earth would flatten more and more. The experience for someone standing at the equator would indeed feel like a reduction in gravity...and that's true right now. If you currently weigh 100lbs at the north pole, you'd only weigh 99.65lbs at the equator.

But even one order of magnitude increase in spin rate would be catastrophic...the shape of the planet would change drastically...and much more than that would cause the whole thing to break apart - there would be catastrophic consequences long before a person would fly off of the surface. SteveBaker (talk) 16:09, 22 November 2015 (UTC)

The increase in spin speed might make you feel lighter, but the increased mass of rock underfoot would increase gravity, right? Gravity varies locally depending on what's underfoot - surely a more greatly deformed earth would affect that as well? 99.235.223.170 (talk) 16:32, 22 November 2015 (UTC)

That's why I linked hydrostatic equilibrium. Roger (Dodger67) (talk) 16:36, 22 November 2015 (UTC)

Steve's 99.65 lbs. isn't exactly right. You feel lighter at the equator for two reasons. One is the direct effect of the centrifugal force (i.e. centripetal acceleration of the Earth away from you). This is given by v²/r and works out to about 0.35% of 1 g-force, so I assume that's what Steve had in mind. But the other reason is because you are farther from the center of the Earth. If the Earth was a sphere, the force of gravity would be proportional to 1/r² and you would be about 0.71% lighter for that reason, compared to the poles; but the whole point of this calculation is that the Earth is not a sphere, and so you will feel additional weight due to the equatorial bulge, reducing the effect I just described. Perhaps someone can cite a reference that provides the correct value. --70.49.170.168 (talk) 16:51, 22 November 2015 (UTC)

Probably the easiest way to get an estimate is this: the effective gravitational potential in the rotating frame should be roughly constant over the Earth's surface (because any variation is a hill and at large distance and time scales there will be a downhill flow that equalizes it again). The potential at the center of the Earth is constant because it's just one point. Therefore the average acceleration (= first derivative of the potential) along a straight line from the pole/equator to the center will be larger/smaller by an amount equal to the ratio of the path lengths. If that difference is distributed uniformly over the length of the path, then equatorial acceleration / polar acceleration ≈ polar radius / equatorial radius ≈ .9967.

However, Gravity of Earth#Latitude says "effective gravity increases from about 9.780 m/s² at the Equator to about 9.832 m/s² at the poles", which is a ratio of .9947, so something is wrong with that argument, possibly the assumption that the difference is distributed uniformly. -- BenRG (talk) 19:19, 22 November 2015 (UTC)

I heard on a science podcast that I listen to, that if the earth stopped spinning gently, you could walk around the equator on dry land, since the water there now is due to the bulge caused by the earth's rotation. I must admit I haven't looked for a source to confirm this claim. 00:09, 23 November 2015 (UTC)

If there was a cat orbiting the sun, what would its name be?

See headline.

There are many cats orbiting the sun. We don't know what their names are, only what their owners choose to call them. SteveBaker (talk) 15:58, 22 November 2015 (UTC)

Cats don't have owners, they have slaves. Roger (Dodger67) (talk) 16:35, 22 November 2015 (UTC)

And anyway, the naming of cats is a difficult matter; it isn't just one of your holiday games. --70.49.170.168 (talk) 16:53, 22 November 2015 (UTC)

To get back to the OP's question, the technical term is Small Solar System body - meteoroid is also a possibility, although we'd have to use the definition of "metal" as "anything other than hydrogen or helium" for this particular case. See also Asteroid#Terminology. Tevildo (talk) 16:40, 22 November 2015 (UTC)

I rather disagree. You're absolutely correct that some stellar physicists would call a cat a metal, because its metallicity is quite high. But, it's premature to assume we ought to use that specialized jargon when we write about orbital cats.

First, let's describe the composition of a cat. To draw on the science-fiction series Star Trek, carbon-based life forms are termed "ugly bags of mostly water." You can read a more encyclopedic breakdown of the typical mass composition of an ordinary mammal here: Composition of the human body. For stoichiometric purposes, a cat and a human are nearly identical. By mass, a cat (like most mammals) is mostly liquid water; a small fraction is made of organic molecules - largely carbon, nitrogen, and oxygen, with traces of a few other elements like sodium, sulfur, calcium, and so forth.

For the purposes of stellar physics, those materials including carbon and oxygen are, indeed, "metals." But, an orbital cat is not a star: it does not exhibit any indications of nuclear fusion; it does not incandesce; it hardly self-gravitates; it certainly is not in hydrostatic equilibrium. So, a cat is not a star; it is not a planet; if it orbits the sun, it is a "non-planetary" body.

It is much more likely that we would apply the terminology that is commonly reserved for non-planetary worlds that exist within our solar system: comets, asteroids, and meteoroids. The classification schema for non-planetary bodies distinguishes between many types of objects. First are icy worlds (water, ammonia, and methane are common); a cat is not made of frozen water or methane ice. The next general category are the "metallic" bodies: these are mostly iron and nickel asteroids, consistent with the chemical spectrum we associate with the Iron peak. A cat is not primarily made of these materials. The last category, which is the "catch-all" for everything else floating in our solar system, is the term "chondritic". This includes other solid bodies that would be neither a metallic nor an icy world - so a cat would be a chondrite - even more specifically, a carbonaceous chondrite.

If a chondritic body were discovered in orbit of our Sun, and we learned that it did contain organic chemicals, it would be a high priority for our best space scientists to study this object. The NASA Astrobiology Roadmap highly emphasizes our ongoing search for organic macromolecules and amino acids on extraterrestrial worlds.

Nimur (talk) 20:43, 22 November 2015 (UTC)

I'm not sure what you're disagreeing with, I'm afraid. Are you saying that a cat can't possibly be a meteoroid as it's not metallic in the geological as opposed to astrophysical sense? In that case, would it be an asteroid? Or, are you saying that the "rocky or metallic" qualification isn't necessary for it to be a meteoroid? In that case, our meteoroid article needs to be corrected. Tevildo (talk) 21:15, 22 November 2015 (UTC)

Sorry, my opening sentence was not clear: I do not think we would call a cat "metal" simply because it is mostly non-hydrogen/helium. After re-reading your comment, I see that you weren't actually suggesting we do that. Nimur (talk) 01:31, 23 November 2015 (UTC)

Surely, in the absence of life support systems, an isolated cat would be made of mostly frozen water in fairly short order? MChesterMC (talk) 10:23, 23 November 2015 (UTC)

It would probably not survive - interplanetary space is not suitable for unprotected mammals for many reasons. However, objects in space are not necessarily very cold: the temperature at which they equalize primarily depends on their radial distance from their parent star. In practice, not all objects actually reach thermal equilibrium - it all depends on their material properties, rotation rate, and so forth. If an object rotates slowly, relative to its thermal conductivity and thermal capacity, its day-side may remain hot, while the night-side remains colder, and a thermal gradient may be set up throughout the object.. Nimur (talk) 01:34, 24 November 2015 (UTC)

Sol. StuRat (talk) 19:00, 22 November 2015 (UTC)

That answer is open to a charge of affirming the consequent, though. The OP may be interested to know that the French did have an active space program for cats in 1963. Tevildo (talk) 19:39, 22 November 2015 (UTC)

Was it a catastrophe ? StuRat (talk) 01:03, 23 November 2015 (UTC)

Swcharzschild limit

What unit of measurement is used in the Swcharzschild limit? In other words, is the big Rs at the end of the equation measured in cm or m or km or what?Megaraptor12345 (talk) 18:01, 22 November 2015 (UTC)

It's spelled "Schwarzschild" BTW. The r has the same units as the c in the equation. The G and the m should also match the units in c. Basically the output unit is the same as the input unit. Ariel. (talk) 18:19, 22 November 2015 (UTC)

Thank you, Ariel. Sorry about the spelling mistake! It is a hard word to spell!:)Megaraptor12345 (talk) 22:31, 22 November 2015 (UTC)

For those of you playing along at home, Schwarzschild radius is the article on this topic. DMacks (talk) 04:05, 23 November 2015 (UTC)

It depends on which version of the equation you're looking at. There is a tendency in physics to use natural units, in which case various constants (usually at least c and ħ) are set to 1, but even then authors tend to have their own preferences (e.g. some authors set G=1, while others don't). This is extremely confusing if you aren't familiar with the subject matter (especially when authors neglect to state which convention they're using), but it really saves time when you get the hang of it. In any case, the SI-compatible expression for the Schwarzschild radius is R_s=2GM/c². This gives R_s in metres if you enter G in metre cubed per second squared per kilogram, M in kilogram, and c in metre per second. --Link ^(t•c•m) 22:33, 23 November 2015 (UTC)

Physicists normally work in SI units, which means distance will be measured in metres unless otherwise stated. You could use any distance unit though, but you would have to be consistent in the rest of the equation. For example, you could measure the distance in furlongs, but would therefore have to measure the speed of light in furlongs per time unit (say, fortnight) and the speed of light in furlongs per fortnight]]. This would also change the value of G. Iapetus (talk) 17:32, 24 November 2015 (UTC)

Serrula, Rastellum, Fovea; What?

Hello, I would like to ask a few questions about some of these spider-related terms. I have looked up these terms: rastellum, serrula, fovea, tegular; and not found anything that fits the context (which was in relation to Tarantulas). So what do these mean?Megaraptor12345 (talk) 22:40, 22 November 2015 (UTC)

Wait, I have found out what Tegular means, sorry! Still, I do not know what the others mean.Megaraptor12345 (talk) 22:46, 22 November 2015 (UTC)

Does fovea help ? StuRat (talk) 22:56, 22 November 2015 (UTC)

[ec] It looks as though Spider anatomy and Glossary of arachnology terms need some additions. For rastellum, see Trapdoor spider. For serrula, see wikt:serrula. Fovea is a general anatomical term - according to this site, a spider's fovea is "a depression in the middle of the carapace which is the internal attachment point for thoracic muscles". Tegular means "of or resembling a tile", and the various tegular apophyses are mentioned in our spider anatomy article. Tevildo (talk) 23:01, 22 November 2015 (UTC)