Wikipedia:Reference desk/Archives/Science/2019 September 15

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September 15

What is the preferred solvent for acrylic paints used in art?

Acetone or something else? AboutFace 22 (talk) 16:09, 15 September 2019 (UTC)

It depends, to dilute the paint either water or acrylic medium is added, depending on the desired effect. For cleaning spills or brushes use water if the paint has not yet set, if it has already dried acetone works well. -- Roger (Dodger67) (talk) 18:01, 15 September 2019 (UTC)

• Typically water. Acrylics are becoming particularly popular these days, especially for applications where they weren't previously so common (they've been used for brush-on-paper artwork for decades): plastic models, spray cans. Much of this change is driven by an acrylic's ability to use a water-based solvent, which is one way to address the modern restrictions on VoC (volatile organic solvent content) in paint. Of course, they can still be used with a variety of other solvents, and acetone is one of those. I think it's used in a lot of the spray cans, because of its very rapid evaporation. Andy Dingley (talk) 18:11, 15 September 2019 (UTC)

References

Thank you, - AboutFace 22 (talk) 23:44, 15 September 2019 (UTC)

What was the advantage for the Russians to use nuclear reactor in the propulsion system of the rocket that exploded in the Arctic recently?

Somebody said that such a rocket can circle the globe many times and used at the Russians' convenience, but what is the advantage of that? It is safer for any rocket to be as short time as possible in the air. Did it give it additional speed increment? Was it potentially faster then rockets with chemical propulsion? Did they hope to kill two birds with one stone: to use it as a nuclear bomb (in the warhead) and a dirty bomb from disintegrated engine? Thanks, AboutFace 22 (talk) 16:20, 15 September 2019 (UTC)

9M730 Burevestnik is the article you're looking for, though it's rather skeletal. Henry^Flower 17:27, 15 September 2019 (UTC)

Dwell time over the target is important, as that can give them time to change targets, abort, etc. It could circle the area while they decide what to do. Also, this could give them more fuel to avoid interceptors, and still have enough left to reach the target. And note that some harder-to-detect routes below the radar require long detours down valleys, where denser air requires more fuel to overcome. SinisterLefty (talk) 17:33, 15 September 2019 (UTC)

Oh, and a dirty bomb is insignificant when compared to a nuke, so that theory doesn't make sense. You might also think it could be an alternative if the nuke doesn't detonate, but then the radioactive material from that would create a "dirty bomb" anyway. SinisterLefty (talk) 20:16, 15 September 2019 (UTC)

Being in the air could be safer than on the ground (well, if the rocket actually work as intended, of course): on the ground the rocket move slowly (or even not at all), and only on suitable road; while in the air it can be in more place and move far faster. Air forces of countries with nuclear missiles are known to have planes on the fly, ready. This rocket would do it, just without the trouble of a plane and crew. Gem fr (talk) 04:20, 16 September 2019 (UTC)

Thank you for the reference. 107.191.0.241 (talk) 00:40, 16 September 2019 (UTC)

I thought the Russian thing was supposed to be a jet rather than a rocket, i.e. the reaction mass is drawn in from the air rather than carried on board. Think of an unmanned strategic bomber that can stay in the air for months at a time and I'm sure you can think of applications. The US uses B-52's like that (they always have some in the air) but that creates big logistics problems regarding pilots, refueling, etc. 67.164.113.165 (talk) 22:35, 21 September 2019 (UTC)

What is the benefit of grass-fed beef?

Have there been conducted any scientific studies to say that grass-fed is better than grain-fed or otherwise.? AboutFace 22 (talk) 16:59, 15 September 2019 (UTC)

• It is known to taste better, which means that it is different somehow. One assumes that the USDA would be reluctant to fund studies that might discover that one kind of beef might be more harmful than another. Abductive (reasoning) 17:57, 15 September 2019 (UTC)
• Here in Europe (at least in the UK, where we're facing the impending chaos of brexit and an influx of US meat) this is a big issue at present. Mostly for animal welfare issues: the alternative to grass-fed, i.e. the US feed lot system is seen as inhumane. There's also the problem of antibiotic resistance which it causes, with the US fondness for "prophylactic" antibiotics, their ongoing use as growth promoters and the increased infection risks from such high stocking densities. Andy Dingley (talk) 18:14, 15 September 2019 (UTC)

Setting aside antibiotics and growth hormone, etc, I recently travel to Wyoming in USA and while driving saw endless grass fields with black cows, no udders, feeding on green grass. Somebody in the know said they were "beef cows." If that corner of the USA is representative of the entire country, then where are the feed lot cows? With present emphasis on healthy nutrition, they might be a thing in the past. AboutFace 22 (talk) 18:44, 15 September 2019 (UTC)

Feed lots tend to be located well off the main roads, as the powerful stench the concentrated manure causes is highly objectionable to those not used to it. SinisterLefty (talk) 19:40, 15 September 2019 (UTC)

Actually, there is a gigantic feed lot that holds up to 100,000 cattle right on Interstate 5 about halfway between San Francisco and Los Angeles. You can see the cattle jammed in from your car window and it stinks to high heaven. Cullen³²⁸ Let's discuss it 19:57, 15 September 2019 (UTC)

Amazing the disgusted motorists can't get it banned. Them being voters in other districts, not there, may make the difference. SinisterLefty (talk) 20:01, 15 September 2019 (UTC)

Which side of the road is it on? ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:54, 15 September 2019 (UTC)

Bugs, it is on the east side of the freeway and highly visible when traveling northbound toward San Francisco. Cullen³²⁸ Let's discuss it 01:23, 16 September 2019 (UTC)

Also, if the density of cattle in feed lots is, say, 1000 times greater than in open fields, then an equal amount of cattle would mean 1/1000 as much feed lot space as open fields, making them far less noticeable (if far enough off the road as to hide the stench). SinisterLefty (talk) 20:13, 15 September 2019 (UTC)

Corn-fed beef tends to be fattier, and grass-fed leaner. So, the grass-fed is healthier for you. SinisterLefty (talk) 19:42, 15 September 2019 (UTC)

And the grain-fed is tastier. Always the dilemma: good health or good taste? ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:55, 15 September 2019 (UTC)

The grass-fed cattle can be considered free range, and the feed-lot are basically cage animals. Graeme Bartlett (talk) 02:15, 16 September 2019 (UTC)

Yes, that's a good point, in that walking around open fields leads them to burn fat and build up muscle. That makes for leaner, healthier meat. SinisterLefty (talk) 11:54, 16 September 2019 (UTC)

It is NOT what I expected to read. There is a belief, probably supported by statistics that people who eat beef have a slightly lower longevity. Does it concern grass-fed or corn-fed beef or both? AboutFace 22 (talk) 00:01, 16 September 2019 (UTC)

All red meat is unhealthy, but lean meat is better than fatty meat, and this implies that the leaner, grass-fed cattle are healthier. Of course, the fat can always be cut off the fattier cattle, but then there wouldn't be much point in fattening them up with corn, unless somebody eats that fat. SinisterLefty (talk) 03:04, 16 September 2019 (UTC)

Oh dear, pretty much every word of these sentences need ... grass-fed may or may not be leaner, lean meat may or may not be better (actually, gastronomy LOVE fatty things, and for meat there is a word for it: marbled meat), no food is per se unhealthy (just like every thing, it will depend on the dose), etc. Gem fr (talk) 04:06, 16 September 2019 (UTC)

It really shouldn't be necessary to provide links for the most obvious of these points, like lean beef being healthier than fatty beef, but here's a Mayo Clinic link: [1]. Here's a link from them about grass-fed beef being leaner and having more of other nutrients: [2]. That fatty beef tastes better to some (it's actually about what you are used to) is quite irrelevant to how (un)healthy it is. As for dosage, less fatty beef is certainly less unhealthy, but at no point does it become better than none (assuming you are getting your nutritional requirements for calories, protein, iron, vitamin B12, etc., fulfilled elsewhere). SinisterLefty (talk) 11:49, 16 September 2019 (UTC)

I am unimpressed by a ref from a source obviously for fat people. Of course, these would be advised to got to lean meat... assuming you are getting your nutritional requirements fulfilled elsewhere is actually the problem. As relevantly you point out below, the "as opposed to what" part (plus, the "who are you" part, depending on age, activity, being pregnant ...) is the tricky question. Gem fr (talk) 23:59, 16 September 2019 (UTC)

This is what happened. I avoid eating beef for that very reason: alleged shortening life expectancy, however an article in People magazine of September 9, 2019 took my attention, on page 71 there is an article: Eating for your brain written by someone whose mother had Alzheimer's dementia and at the end of the article he recommends a list of 10 foods to eat to avoid it: olive oil; avocados; blueberries; dark chocolate; eggs; grass-fed beef; etc. So he equated grass-fed beef with blueberries. I found it very audacious. Quite a comparison! Thanks AboutFace 22 (talk) 13:56, 16 September 2019 (UTC)

Two points:

• Lean beef could very well prevent Alzheimer's while also shortening life expectancy.

• When considering whether any food is healthy, we must ask "as opposed to what" ? So, grass-fed beef may well be a better alternative to corn-fed beef, if we make the assumption that the person eating beef would be willing to make that switch, but not to eliminate beef entirely. SinisterLefty (talk) 14:46, 16 September 2019 (UTC)

To answer your original question, yes, there have been a number of scientic studies on this suject see: [3], [4], [5], [6], [7]. To quote from the abstract of the last one which was a literature review "Effects on fat colour were variable and, in six of the nine experiments where fat colour was measured, grain feeding failed to “improve” fat colour. It is concluded that there is little scientific justification for the claim that grain feeding is necessary to produce high quality beef. Beef of comparable quality can be obtained from cattle finished on forage‐based diets (i.e., pasture) provided that acceptable carcass weights and degrees of finish can be achieved at a young age".Richerman (talk) 15:59, 16 September 2019 (UTC)

There is another peer reviewed study published online here concerning the consumption of red meat which concludes: "Increases in red meat consumption, especially processed meat, over eight years were associated with a higher risk of death in the subsequent eight years in US women and men. Increased consumption of healthier animal or plant foods was associated with a lower risk of death compared with red meat consumption. Our analysis provides further evidence to support the replacement of red and processed meat consumption with healthy alternative food choices." Richerman (talk) 16:21, 16 September 2019 (UTC)

Your comment miss the usual CAVEAT: we do not give health advice, Correlation does not imply causation, and Most Published Research Findings Are False Gem fr (talk) 23:59, 16 September 2019 (UTC)

"Correlation does not imply causation" always seemed too strong, to me. It does imply causation, what it doesn't do is prove it, at least not alone (some mechanism for A to possibly cause B helps in that regard). And, if a certain diet may cause disease, then avoiding it seems prudent, rather than risking your health to wait until there is absolute proof (by which time you may well be dead). Now, if there's just no possible way A can cause B, then any correlation can safely be ignored. SinisterLefty (talk) 14:00, 19 September 2019 (UTC)

Ye, well, NO. Just NO. IT DOES NOT IMPLY CAUSATION, period. not at all. Below at Wikipedia:Reference_desk/Science#Clinical_trials_for_drug_addiction you have a very nice comment of @tigraan about about you can get a correlation with no meaning whatsoever, and Most Published Research Findings Are False is all about how frequent it is. As for your if a certain (whatever) may cause disease..., well, this is just the rationale of antivaccination, says it all about how dumb that is. Also, there is a strong correlation between going to hospital and dying, while there is a very well acknowledged way for hospital to cause death: Hospital-acquired infection; I leave it to you the obvious conclusion. Gem fr (talk) 19:07, 19 September 2019 (UTC)

Many meds are in use despite us not knowing how they work, but only noticing that they do work from the correlation between taking them and the condition improving: [8]. Contagion theory was developed before the microscope, so there was no known mechanism for how a disease spread from one person to another, but nonetheless, mechanisms like quarantine showed promise in stopping the spread of disease. As for potential harm, that needs to also be taken into account, too. In the case of the anti-vaccine group, the correlation between taking vaccines and avoiding those diseases is far better established than any correlation between vaccines and autism. The original study which claimed to find a correlation was apparently a fraud.

As for hospitals, the correlation between going to hospitals and getting an infection is enough to avoid hospitals for some rather basic procedures, which can be done in a clinic on an outpatient basis, with no infected patients present. However, the risk of death from not going to a hospital following a massive heart attack, say, would far outweigh the risk of death from an acquired infection.

Common sense must also be applied, for example if people owning private jets are shown to live longer, there's no known mechanism where A could directly cause B, but there is the obvious factor C, that the person is rich, causing both A and B (living longer due to access to better food, medical care, etc.). SinisterLefty (talk) 22:44, 21 September 2019 (UTC)

Thank you, very thorough answers. I appreciate all contributions. A lot of good knowledge, well referenced. AboutFace 22 (talk) 22:55, 16 September 2019 (UTC)

I think it's also worth mentioning that there's another reason some people prefer grass-fed, which is the perception that it imposes less suffering on the cattle. As someone mentioned, the lives of corn-fed beeves are not what you would call enviable. --Trovatore (talk) 23:03, 21 September 2019 (UTC)

There's also the environmental effects. Cattle manure spread out over vast fields tends to be broken down by natural processes and not cause much harm, while in a feed lot there's too much in too small of an area for it to break down before it runs off into the nearest body of water, causing e. coli contamination, etc. SinisterLefty (talk) 23:11, 21 September 2019 (UTC)

Are dreams stereoscopic?

Are dreams stereoscopic? I mean, when we dream of a cow for instance, are there two images of the cow that fuse into one image of the cow, similar to stereopsis when we are awake? Or is it always just one image when we dream of the cow? Yellow Sunstreaker (talk) 21:23, 15 September 2019 (UTC)

What does your own experience tell you? ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:28, 15 September 2019 (UTC)

If it were that easy to figure out, I wouldn’t be asking. Yellow Sunstreaker (talk) 02:22, 16 September 2019 (UTC)

And if you can't tell, how could anyone else? ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:23, 16 September 2019 (UTC)

Baseball Bugs, you do not need to give crap replies even to what you perceive as crap questions. I mean, usually, you are at least somewhat funny. OP's question might be answerable with MRI (or other methods), as a 10-s GScholar search shows many studies on stereoscopy and brain activity. Tigraan^{Click here to contact me} 08:48, 16 September 2019 (UTC)

And you do not need to jump to assumptions and insult the OP. It's an interesting question which I had not thought of. Being conscious of it now, the next time I'm dreaming I'll try to notice if it seems stereoscopic or "flat". ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:41, 16 September 2019 (UTC)

The way I read And if you can't tell, how could anyone else? is "your question is speculation and unanswerable" with added sarcasm, which is why I reacted harshly (because in fact there is a non-obviously-wrong way to investigate the question). I guess I was wrong to read it that way. Tigraan^{Click here to contact me} 12:50, 17 September 2019 (UTC)

I doubt if they occur at the level where that term has any meaning. Let me explain:

When you see things, your optic nerves send images from both eyes, which are then combined in the visual processing center of the brain, with depth and size interpreted as part of the process, and the items in the image are then matched against known objects, such as "chair". I believe dreams are more likely to pick up at this point, as opposed to doing the whole simulation of images coming from the eyes. So, you dream of a chair, not of two images (or one image) of a chair. SinisterLefty (talk) 02:59, 16 September 2019 (UTC)

You are wrong, if you believe the signal processing is one way. The visual system process information from itself and other parts of the brain just as much as from the eyes, since the lateral geniculate nucleus. Eyes and optic nerves still work when you sleep, they just produce/transport some signal of a non specific dark image, but this would allow the brain to produce whatever it feels like plausible, and of course the system that match both eyes signal into something consistent would still work. So, for my 2 cents, this would be sort of "eh, left eye, I see a chair, don't you too?" / "Ye well, was not sure, but now you say so, I indeed see a chair. " (CAVEAT: this is analogy, not an homunculus argument where centers in the brain would be homonculi talking to each other to reach an agreement on what is to be seen) Gem fr (talk) 03:47, 16 September 2019 (UTC)

One way of considering this question is to close your eyes and imagine a scenario. Is this scenario stereoscopic, does it have depth? From personal experience I find it quite hard to decide. Dreams are largely, not wholly, based on memory so generating a memory might be as close as we can get, at an everyday level, to dreaming. Good luck Bugs on remembering to look at your dreams. Richard Avery (talk) 11:30, 17 September 2019 (UTC)

Maybe try to visualize the scene from Vertigo where the camera pulls back and zooms in at the same time, giving a sense of depth to that staircase Jimmy Stewart is looking down upon. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:38, 17 September 2019 (UTC)