Wikipedia:Reference desk/Archives/Science/2017 July 2

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July 2

Odds of AIDA mission ending humanity?

The AIDA (mission) proposes to smash a "refrigerator-sized" spacecraft into "Didymoon", the 170-meter satellite of 65803 Didymos. Didymos will pass 6 million km from Earth in November 2023.

As I understand it, the mission is expected to cause a noticeable change in the asteroid's orbit: "The impact of the 300 kg (660 lb) DART spacecraft at 6.25 km/s will produce a velocity change on the order of 0.4 mm/s, which leads to a significant change in the mutual orbit of these two objects, but only a minimal change in the heliocentric orbit of the system"

What I'm wondering is, first: what are the chances they break it? A 170-meter asteroid has very little self-gravitation, and this one passes near to Earth and Mars fairly often, though I'm not sure how often. So could an impact like this lead to Didymoon cracking apart, whether directly or under tidal stress during a future flyby?

And second: if Didymoon comes apart in two pieces, I assume there will be some complicated three-body interaction. I would think that eventually one of the two pieces would get "ejected" (albeit slowly) from the system. How much of a difference does that make in the asteroids' long-term trajectory?

And third: Does any disruption of Didymos, however small, increase its odds of actually hitting Earth rather than skimming past in hundreds or thousands of years? (This assumes a pessimistic scenario for human civilization in which future adjustments don't happen)

Oh, last but not least: Didymos is 0.75 km wide, versus 15 km for the K-T impactor. So... what's the damage like? Wnt (talk) 12:27, 2 July 2017 (UTC)

One of the sources cited [1] "there is no possibility that the DART deflection experiment would create an impact hazard." I don't know what "no possibility" means here but I don't see any intrisic reason to think hitting it will definitely result in an increase of the the chance it will hit earth in hundreds of thousands of years as opposed to decreasing it. I.E. for such a long time frame, it would seem likely our predictions are too limited such that you might as well think of any hit as having neutral odds. Nil Einne (talk) 13:28, 2 July 2017 (UTC)

[2] says

Large-scale restructuring is unlikely to occur given the energy regime of the impact event, which is orders of magnitude below the catastrophic disruption impact energy threshold at Didymoon’ size, despite its rather low gravitational binding energy. On the other hand, regolith displacement may occur in the vicinity of the impact point and crater, due to the very low gravity of the asteroid. Even small seismic waves may cause displacement or lift-off of loose material. However, there are no reliable existing tools and knowledge to quantify these effects.

Nil Einne (talk) 13:39, 2 July 2017 (UTC)

• 
  Scale model of the Earth–Moon system: Sizes and distances in real scale.

Even with their low gravity these objects are very sturdy backed together over the Billions of years. Also this "asteroide twin" seems to far away even in its closest visites. Its projected to come nearest earth in 2123 and nearest meaning 5.900.000 km. In real perspective even our own moon at a distance of only 360.000 km is infact much further away from earth then common pictures and our view from earth suggests. There is a tremendous amount of space inbetween all of these distances for objects to pass savely a million times and in all that our beloved homeplanet is infact a very, very tiny spot. So even if we would cause some new objects on new trajectories with this mission, its more likely that you win 20 million $ in next weeks lottery then any of these objects hitting earth in the next 20 million years. --Kharon (talk) 15:30, 2 July 2017 (UTC)

"Its more likely that you win 20 million $ in next weeks lottery then any of these objects hitting earth in the next 20 million years". Actually that's not true. The Earth impact rate for ~1 km objects is estimated at a few per million years. Objects at that size have an impact energy of approximately 10 gigatons of TNT (somewhat less than the biggest nuclear bombs), enough to destroy cities and cause regional devastation but not enough to trigger widespread or global disasters. Pick a near earth asteroid at random and the odds of a collision within 20 million years is roughly 1%, far higher than the odds of winning the lottery next week. Basically, 20 million years is a really long time when it comes to the orbital interactions of objects that circle the sun every few years. Dragons flight (talk) 16:52, 2 July 2017 (UTC)

10 gigatons is 100x the largest nuclear bomb ever made. Sagittarian Milky Way (talk) 22:37, 2 July 2017 (UTC)

You're right, I was misremembering the size of historical nuclear bombs. For scale though, the impact event that killed the dinosaurs and caused planet-wide devastation is estimated at around 130,000 gigatons of TNT, which is still much larger and much rarer. Dragons flight (talk) 04:41, 3 July 2017 (UTC)

I have to confess i completely made these "20 million" up however the odds you cite refer to all the asteroids out there while i was only referring to probability this twin one will hit earth. Given that our Planet is over 4 Billion years old and this asteroid twin has obviously not seen a chance to "join us" in all that time, we are probably both millions of km and billions of years off with our madeup or cited estimations. --Kharon (talk) 17:49, 2 July 2017 (UTC)

I would take issue with Kharon's statement that "Even with their low gravity these objects are very sturdy backed together over the Billions of years." From Asteroid#Composition:

Most of the smaller asteroids are thought to be piles of rubble held together loosely by gravity, though the largest are probably solid.

Loraof (talk) 22:10, 2 July 2017 (UTC)

Thinking about it, a simple scenario: consider a "peanut-shaped asteroid" made from two pieces. A quick search turned up this link - I didn't find a Wikipedia article for a July 25, 2015 flyby; obviously a better link is possible. But the picture says a thousand words: you can have two asteroids stuck together fairly lightly. Now suppose the impactor, expected to cause a 0.4 mm/s velocity change in the Didymoon, causes a 0.8 mm/s velocity change in half of it instead. Then they would get 170000 mm apart - i.e. the diameter of Didymoon, with a 25-fold reduction in gravity between the halves - in roughly 200000 seconds. It would take on the order of a (0.8 mm/s)/200000 s gravity field, i.e. 4 x 10^-9 m/s^2, to stop that separation in that time. And ..... whoah. I just looked up asteroid gravity as a function of size and came up with this figure that claims a 100-meter asteroid pulls 0.0001 g = 0.001 m/s^2, which seems like an incredible amount of force for such a puny thing! So now I gotta actually do the math! That's 1 mm/s^2 velocity change, which ... seems to mean to me that the two halves would come crashing back against each other (with modified overall velocity) in just two seconds!

Unless I fouled up here, my overall impression of asteroid gravity was completely wrong. Yet thinking about it, the math isn't wrong - the Earth is 6000 km, divide by m^3/r^2 assuming constant composition means r, so 17085 m/6000 km = 31 x 10^-4, write the rest off as density difference. I just never realized that little rocks could have a meaningful pull to them. Wnt (talk) 00:34, 3 July 2017 (UTC)

Shouldn't it be 85 m and 6371 km? Sagittarian Milky Way (talk) 00:55, 3 July 2017 (UTC)

You're right. That said, this is an order of magnitude argument - the two would be no where near getting pried apart this way. Wnt (talk) 11:05, 3 July 2017 (UTC)

1. what are the chances they break it?

For sure, there will be some dust that will break away, so i guess the answer is: 100%. The questions are rather : "which size?" and "what direction?"

Obviously the ejecta will have energy from the impactor, and less than the latter does (1/2 300 6250² = 5.86 GJ ; 1kg TNT is 4184 kJ, so the impactor bring as much as ~1.4 t TNT).

Now, considering the effect of artillery shells (quite big but lighter than 1.4 t TNT) on Earth, or the impact of objects making impact crater, I guess the impact is expected to produce

- A thrust to the bigger part , keeping most of the momentum and kinetic energy from the impactor

- a cone of things expulsed away from the point of impact, none of them big enough to matter as far as Earth collision is considered (even-though some may be pretty big, from a human perspective: the size of a car or even a tree as evidenced by BLU-82 for instance could move trees)

1. Does any disruption of Didymos, however small, increase its odds of actually hitting Earth?

It does, in the very same proportion that it decreases its odds of hitting Earth if it were to happen. Chance for Earth to be hit just do not depends on whether didymos is hit by something launched by humans, it only depend on the size of Earth as a target and the density of potentially hazardous object in space (which 65803 Didymos already is, one of the reason it was chosen as target, i guess). Obviously disrupting the target would produce more objects of a smaller size, each having it's own chance to hit Earth, but with smaller chance to do significant damage. Since there are already so many PHO, one more or less do not make a difference.

Gem fr (talk) 14:07, 3 July 2017 (UTC)

Mechanical clearance of the nasal passage

I noticed that some people suggest that picking a nose is unacceptable behaviour and introduces the risk of abrasion and infection of mucous membranes. It certainly does seem antisocial in my opinion. If a person was to refrain from mechanical clearance of their nasal passage, would the lumen become occluded at some point in infancy and remain that way for the rest of their life or does there exist a natural mechanism for preventing occlusion? --145.255.244.249 (talk) 14:08, 2 July 2017 (UTC)

Digging in your Nose is no real danger to health but a serious "Blasphemy" of the common concept of Hygiene because the resulting "mining products" are usually, discreetly spread everywhere. Nevertheless, like peeing in Public Baths, infact everyone does it and there are even scientific studies, not about "if" but "how much". --Kharon (talk) 14:34, 2 July 2017 (UTC)

Do people take showers in Rotherham? I won't give medical advice, but you can draw your own conclusion. μηδείς (talk) 01:08, 3 July 2017 (UTC)

Hmmm, do we have an article on nose picking? Indeed we do. I have no proof at all, but I am suspicious of some sort of instinctive role in antigen presentation by concentrating, drying, perhaps inactivating environmental dust and pathogens in a potentially controlled antibacterial environment... Wnt (talk) 15:25, 6 July 2017 (UTC)

Chemistry questions.

What's more dangerous, 2 hot gases combine to form a cold gas, or 2 cold gases combine to form a hot gas?

What's a chemical I can use to remove oil off of keyboards? (I've tried monitor wipes, isopropanol, hexane, and wipes to kill bacteria/viruses off of keyboards). According to a biochemistry professor, the oil released from our fingertips is a fatty acid, and so ask a organic chemistry professor to remove fatty acids, dichloromethane.

Who kills bacteria and viruses better, 70% isopropanol or 70% ethanol? As well as, 3% hydrogen peroxide and bleach (5.25%, 8.25%, and 10%).

Strongest known covalent bond is C triple bond O in carbon monoxide and does anyone have any values for how the strongest metallic bonds compare? Stongest metallic bonds likely tungsten-tungsten bonds.

Most dangerous endothermic reactions? (Chain reactions can be endothermic.). Endothermic reactions can cause implosions - the opposite of an explosion - where you get sucked in.

Biology: what happens when plants breathe in carbon monoxide? (Are plants capable of breaking the triple bond, or does the molecule bind somewhere.).

Thanks. 12.130.157.65 (talk) 14:13, 2 July 2017 (UTC).

Regarding your statement about strong metallic bonds, I would note that the 5d metals like W have such high melting points because the bonding is not only metallic, but has a partial covalent component. Double sharp (talk) 14:21, 2 July 2017 (UTC)

Regarding plants and CO, according to this article abstract [3], in light bean plants photosynthesize CO into sucrose, and in darkness they oxidize it into CO2 and release the CO2.--Wikimedes (talk) 16:19, 2 July 2017 (UTC)

I can't think of any really strongly endothermic gas reactions off the top of my head, but I should note that there is a minimum pressure (zero, a vacuum). Of course, a large evacuated chamber can produce a dangerous explosion but it is typically limited in impact. By contrast, a heated gas could develop any amount of heat and hence pressure in theory - hydrogen plus oxygen is a typical example. Also note that an endothermic reaction would get colder as it progressed, reducing reaction rate under nearly all circumstances, whereas an exothermic reaction does the opposite. Wnt (talk) 00:50, 3 July 2017 (UTC)

Danger has just nothing to do with whether the combined gas are cold or hot. Whether the produce is hot or cold just matter as far it is from tolerable range of humans (or other living things), but for sure you have rather breath 50°C or -20°C air than 20°C Chlorine, don't you?

There many ways to remove fat, but if you use a dissolvent of any sort (as opposed to : just destroy/burn/vaporize them) you obviously need something (a cloth most of the time) to wash them away. dichloromethane is just a solvent, in the matter.

You may want to produce saponification, an everyday way to get rid of fat.

Look at Hand sanitizer for isopropanol and ethanol efficiency for that matter. they are not significantly different, it seems.

hydrogen peroxide and bleach are too dangerous as hand sanitizers of regular use.

implosion has nothing to do with whether the reaction is endo- or exo- thermic, or if it is a chain reaction or not. It is just a matter of consuming significantly more gas (preferably: all of it) than it produce (preferably: none). If you start with air, consuming N2 is very hard (see Haber process), and consuming O2 is easy but always exothermic and reduce pressure by only 1/4 at most. Everyday way to produce implosion is to fill the vessel with steam and cool it brutally with cold water injection (a physical, not chemical, process).

Gem fr (talk) 15:09, 3 July 2017 (UTC)

Drugs

What portion of patients are prescribed psychoactive drugs to treat mental illness without fully understanding the potential side effects? Benjamin (talk) 16:32, 2 July 2017 (UTC)

Especially for psychoactive drugs, not even the physicians fully understand the effects, and there is little hope that the patients understand them better. Icek~enwiki (talk) 19:28, 2 July 2017 (UTC)

Perhaps not fully, but to a reasonable degree? Benjamin (talk) 23:32, 2 July 2017 (UTC)

You've been given the correct answer, and "to a reasonable degree" is not an objective standard that we can answer without mind reading and speculation. μηδείς (talk) 01:06, 3 July 2017 (UTC)

My pharmacy gives out lengthy bits of literature for each prescribed drug, with lists of potential side effects and the like. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:20, 3 July 2017 (UTC)

Due to the FDA reform bill of 1996 (?) it became mandatory for drug companies to list the most commonly reported side effects, which ended up being things like headache for ibuprofen, runny nose for benadryl, and "delayed back ache" for viagra. Obviously these are not actual side effects of the drug. Very few psychiatric medicines have had long term studies. Look at the problem of sleepwalking on Ambien. I laaughed when a certain congressman claimed he didn't remember driving to a bar at 2am. But I discontinued ambien myself when I started waking up with meals cooked from scratch on my bedstand. I actually boiled spaghetti and made meatballs from ground beef in my sleep. Basically, due to lack of research, poor instruction by doctors and pharmacists, and failure of the patient to read the 4pt small print inserts, the OP's answer is close to 100%. μηδείς (talk) 16:46, 3 July 2017 (UTC)

Are there sources that say so? Benjamin (talk) 21:13, 6 July 2017 (UTC)

I think I'll start taking Ambien, as waking up to meals, fully cooked from scratch, at my bedstand, sounds awesome. Were the dishes done, too ? :-) StuRat (talk) 21:31, 6 July 2017 (UTC)

Can a carbon triangle molecule exist, at least for a short time?

I mean -C-C-C, or (say) =C=C=C, etc, where the third carbon reaches around and bonds with the first carbon. My chemistry teacher told me no, there's too much strain, which I'm sure is true. But I wonder if it could exist briefly, just like the subatomic particles in particle physics that famously exist for only a picosecond, say. More generally, since physicists find briefly existing subatomic particles of interest, do chemists or chemical physicists find briefly exsting chemical particles of interest?--I'm not sure whether or not the logic holds that chemistry people should therefor find them of interest, because the physicists are trying to look at something going on at the underpinnings of reality, where as briefly existing molecules probably wouldn't help with that, except by analogy.-- Thanks.64.134.228.64 (talk) 19:03, 2 July 2017 (UTC)

Cyclopropane is a stable molecule. If you mean a cyclic tricarbon, it surely exists as a very short-lived molecule. Femtochemistry might be of interest. Icek~enwiki (talk) 19:20, 2 July 2017

• If your chemistry teacher doesn't even know about cyclopropane and strained banana bonds, I'd be very worried. Time to hire a new teacher! Cyclopropene is even more strained, and, although not particularly stable, occurs in natural products. As far as tricarbon goes, as our article states, it's a linear molecule. Fgf10 (talk) 19:29, 2 July 2017 (UTC)

I don't know what you'd call =C=C=C ... cyclocumulene pulls up some hits, but those are structures -C=C=C=C ... tetradehydrocyclopropene? I'm not sure if I can figure this out with the IUPAC guidelines... Wnt (talk) 01:00, 3 July 2017 (UTC)

For laughs I went to a PubChem structure search just now, and entered C1=C=C=1 for a SMILES search. It pulled up a bunch of compounds, a surprising number of which have the rudest thing done to a benzene ring - the simplest is called Bicyclo[3.1.0]hexa-1,3,5-triene. [4] Now as far as I know ... Hueckel's rule still applies, and so those bonds are not single and double but roughly order 1.5 ... at least, all the ones around the edge of the ring should be. That other one in the middle, hmmm... you can't really draw a resonance structure for it as a double bond that doesn't have a + or a - at the apex of the triangle, but this probably needs to be looked at with some kind of molecular orbital theory... what kind, I'm not sure. ;) Searching (I was hoping to stumble across a crystal structure, but I don't really know the right way to check for non-protein crystal structures) I ran into part of a paper saying that this is the real structure of what is normally called m-benzyne [5] - given that I had not heard of "m"-benzyne before I should probably avoid weighing in on whether the different structure that article gives for one (with two unpaired electrons) is right or not. Wnt (talk) 23:29, 3 July 2017 (UTC)

Can dogs control their appetites?

Can dogs control their appetites, or do they depend on their human owners to feed them a specific portion? Is it possible to overfeed a dog, or will they just refuse to eat when they are full? Speaking of dog treats, I have seen one of those doggy treats before. They look like dried-up pig ears and chicken feet. Are they safe for human consumption too? Pig ears and chicken feet are sold in Asian supermarkets, so they are definitely made for human consumption. Plus, they still retain moisture. But what about the dried-up variety that is intended to be sold as "dog treats"? And what is "crude protein/fat/carbohydrates"? 50.4.236.254 (talk) 19:46, 2 July 2017 (UTC)

Obviously not all dogs can control their appetite. See Commons:Category:Fat_dogs :). From the evolutionary perspective such an ability is redundant and even harmful as wild animals rarely have food overabundance. Ruslik_Zero 19:54, 2 July 2017 (UTC)

So, if you feed a dog more and more and more, then it will eat everything you give indiscriminately? I think the amount of money you spend on the food is one limiting factor. If you budget $20 for home-made dog food, then the dog is only going to eat $20 worth of food. Budget less, and you provide less, and the dog will eat less. Meanwhile, when I am full, I can't take in any more food. Tried that, didn't work. I just felt very sick and vomited. 50.4.236.254 (talk) 20:15, 2 July 2017 (UTC)

If you want to chew on dog treats, go right ahead. They're designed to be palatable for dogs, not for humans, so you may not particularly enjoy chewing on a pizzle, but then, you might. Dogs are quite capable of overeating and puking too. --jpgordon^{𝄢𝄆 𝄐𝄇} 21:02, 2 July 2017 (UTC)

Careful, though dog food should generally be free from harmful bacteria and toxins, it may not be manufactured to human standards. In addition, animal food may contain ingredients (such as bone meal) that the animals are able to digest but that will cause problems for humans. In particular, I've heard of people eating food that cats enjoy and getting severe vomiting or diarrhea. Dragons flight (talk) 21:38, 2 July 2017 (UTC)

Depends on the dog. Our golden retriever often decides not to eat her whole portion of dog food, leaving 10-50% of the meal behind. I interpret this as her being full. However, just like how people make room for "dessert", even when she is done with her dog food, she will still gladly eat her dog treats. Based on what we have heard from other dog owners, this behavior is rather unusual as many dogs will rarely, if ever, leave food behind in their bowl. Dragons flight (talk) 21:30, 2 July 2017 (UTC)

Overfeeding in the sense that you'll eat a lot more than you should be eating if you only stop eating when you feel full, doesn't work with natural foods. If you eat your stomach full with healthy whole foods you'll probably not get enough calories, because your stomach hasn't adapted to eating such foods. If you get used to eating like this, then your stomach will expand, your intestines will start to make more enzymes, your microbiome will adjust itself. If you then eat your stomach full you may end up eating more calories than you are used to now, but your metabolic rate will have increased too, so you won't get obese. E.g. I weigh 55 kg but I eat 4000 Kcal a day, most of that come from whole grain carbs. I eat more than 1 kg of fruits and vegetables combined. A friend of mine is obese, he eats just 2000 Kcal a day but that's in the form of high fat, low fiber diet. Count Iblis (talk) 00:35, 3 July 2017 (UTC)

The topic is about dogs, not humans. I almost thought you were a talking dog. 50.4.236.254 (talk) 22:54, 3 July 2017 (UTC)

Many dogs do have the ability to stop eating when full, and save the rest for later. Burying food is a natural way for them to save it for later. Since dogs evolved from wolves, which tend to kill large animals, presumably these behaviors developed as a way to handle rare, but large, kills. StuRat (talk) 06:27, 3 July 2017 (UTC)

How can dogs eat white rice?

I watched on YouTube that humans could feed their dogs white rice with chicken, various vegetables, and assorted fruits. But white rice was also used. Hmmm... if dogs can eat white rice, then how can white rice be unhealthy for humans? And why do humans never cook a family meal that is dog-friendly (no garlic, onion, pepper, avocado, eggplant, or chocolate)? Why should humans eat whole grain but dogs can eat white rice? 50.4.236.254 (talk) 23:44, 2 July 2017 (UTC)

White rice is not toxic, it simply lacks micronutrients found in brown rice. Whole grain is, on the balance, better to eat not because processed grains are toxic, but because unprocessed grains retain more micronutrient content, what is known as nutrient density. White rice doesn't kill you. Neither does it kill dogs.--Jayron32 00:12, 3 July 2017 (UTC)

If whole grain has more micronutrients, then why not just feed the dog whole grain rice with vegetables and some meat chunks? 50.4.236.254 (talk) 00:28, 3 July 2017 (UTC)

That is not a question that can be answered here without resorting to speculation and debate. You will have to go an ask each pet owner in person. MarnetteD|Talk 00:45, 3 July 2017 (UTC)

So, you are saying that the answer is subjective, and that the answer varies from dog to dog? 50.4.236.254 (talk) 00:57, 3 July 2017 (UTC)

He's saying that questions of a "why" nature that seek to explain individual choices are not the purview of this desk. --Jayron32 01:05, 3 July 2017 (UTC)

I think some questions are exceptional. Why do humans walk on two legs? is a why question, and humans do choose to walk on two legs. They can, if they want to, walk on all fours. 50.4.236.254 (talk) 01:08, 3 July 2017 (UTC)

Not very easily. Humans' legs tend to be significantly longer than their arms, making literally walking on all fours kind of awkward. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:18, 3 July 2017 (UTC)

There is a matter of value judgment involved - pet owners do make trade offs of various sorts, expense vs. lifespan vs. "quality of life" and so on. A quick web search turns up leading brands of dog food that contain rice, though some are snooty about using brown rice. There are lots of references about it [6]. Bottom line: it doesn't kill them, they eat it, so it's up to the owners to decide when and how much. Wnt (talk) 01:32, 3 July 2017 (UTC)

White rice is considered easy to digest. When our dog is sick, we feed her white rice with chicken and carrots. It is a simple meal that she likes very much and tolerates well even when she has been sick. However, that is not a complete diet which is why we give her more complete meals most of the time. Her normal pet food does not include any rice, though many pet foods do. As with most foods, white rice by itself is not harmful. It is more a question of how much is consumed and whether it is mixed with a sufficient variety of other foods to ensure that the overall diet meets one's complete nutritional needs. Dragons flight (talk) 04:35, 3 July 2017 (UTC)

Sounds a bit like people eating saltines when they have upset stomachs. Certainly not a complete food, but better than nothing, if that's all you can keep down. StuRat (talk) 06:21, 3 July 2017 (UTC)

"how can white rice be unhealthy for humans?"

Sorry to say to the OP, you are assuming something completely incorrect here, a couple of billion people eat white rice every single day, and are fine, so clearly is not unhealthy for humans. There may be more healthy things to eat, but it is not unhealthy, unless abused in large quantities, like anything else (even water). Jayron tried to correct this assumption, but I think he was a little weak on this.--Lgriot (talk) 15:16, 3 July 2017 (UTC)

I agree. I think the whole question about brown rice vs white rice is arbitrary and based on context. For some people, eating white rice is healthy, and they get dietary fiber and micronutrients from the vegetables that go along with the rice. They don't eat the rice alone. 50.4.236.254 (talk) 23:00, 3 July 2017 (UTC)

Well I have taken to soaking rice before using it to reduce any arsenic level in it. I think it helps the texture too. I quite like wild rice. Dmcq (talk) 18:30, 3 July 2017 (UTC)