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August 1

Is there a list of unhealthy ingredients, in order from most to least common?

I reckon High-fructose corn syrup will rank up near (or at?) the top.

The reason why is because I would someday like to lobby for an unhealth tax ("fat-tax" or "fatax") in order to turn the tide of the national obesity epidemic. The tax would pay for subsidies on healthier ingredients, to fund and subsidize healthcare, and education, especially courses pertaining to dieting, nutrition and health.

Instead of taxing individual items (example: A 2-liter bottle of Pepsi), it would be easier to tax any ingredient responsible for the obesity epidemic. Besides, there would be less opposition by the makers of the food & drink with the ingredients in them. Reason being is the makers would swap out the now-pricier unhealthy ingredients for the cheaper, healthier counterparts. That's why I ought to know what these ingredients are.

(I'd also lobby for a tax of too much unhealthy substances in proportion to the weight of the package or serving. Example: A brick of Ramen has too much sodium, so I guess too much salt, for the weight of the product. That's why Nissin, Maruchan or other ramen makers ought to substitute the refined salt for something healthier. However, that's besides the point of this submission.)

Now, without further ado, I look forward to seeing a list of common unhealthy ingredients, and how they're unhealthy in the first place. Thanks. --Shultz the Editor (talk) 00:43, 1 August 2014 (UTC)[reply]

This depends on one's definition of "unhealthy ingredients". I would put arsenic, mercury and cyanide high on the list; although no longer in vogue as "ingredients". 71.20.250.51 (talk) 01:02, 1 August 2014 (UTC) —Afterthough: I missed your addition of "common" ingredients, -sorry-. Perhaps caffeine? Alcohol? MSG? It can be highly dependent on the individual, for some folks it would be wheat or peanuts. 71.20.250.51 (talk) 01:09, 1 August 2014 (UTC)[reply]

Since this is the science desk, let's remember there's no strong evidence monosodium glutamate is particularly unhealthy, beyond that expected from the sodium level (but it's likely to be a less than from sodium chloride) and the fact that it may sometimes be used to make food that isn't particularly healthy taste good (but as much as it's hated in some circles, it could also be in preparation of a resonably healthy meal depending on personal preference and other things with a strong cultural factor at play).

For that matter, there's no strong evidence high fructose corn syrup is much worse than refined sugar. And before anyone accuses me of being some sort of industry shill, we don't get much HFCS in NZ and frankly I think it's generally a stupid thing primarily arising from silly US subsidies and tariffs. I'm not saying that refined sugar is a good thing or shouldn't be included, simply that if you want to include HFCS, there's no clear reason why it's much more important than refined sugar.

If you disagree with either of these claims, I welcome your edits to our articles to reflect the evidence from the preponderance of reliable source that you are I presume claiming exists.

Nil Einne (talk) 01:52, 1 August 2014 (UTC)[reply]

Almost any ingredient is unhealthy when there is too much of it in a product. And the evil is often just as much in the combination of ingredients as with individual ones. HiLo48 (talk) 02:00, 1 August 2014 (UTC)[reply]

Actually, if you look back to my answer for the "Salt Poisoning" question ([1]), sodium is not as nasty as it is made out to be - or, at least, that it so is not without controversy from decent sources. Moreover, very few things are purely "unhealthy", some things may no be healthy, or, perhaps, healthiest, but that's a different matter. But, moreover, weight gain, in most cases, is a matter of calories - if I eat 5000 calories worth of super clean health food, I will become obese in time; if I eat one big mac a day, I will end up starving to death in time. The problem with refined sugars, sodium, fats, etc. aren't because they, themselves, are extremely harmful, but because we are adding them to foods for taste reasons and people are accounting for calories; but, instead, eating lowgrade food and guiding when to eat off of how satiated they are. It is a complex problem and I don't think that you can reduce it down to "food additives" and "unhealthy ingredients", especially if you are levying some sort of monetary penalty.Phoenixia1177 (talk) 03:37, 1 August 2014 (UTC)[reply]

The thing I'd like to know about HFCS is why it has such a strong aftertaste and causes me to continue salivating even 15 minutes or more after consuming it, while sugar does not. There has to be something in it that isn't in sugar - I'm thinking of branched starch structures that might not be broken down in its preparation - but definitely I don't feel like it's interchangeable. And yes - not subsidizing unhealthy foods based on their lobbies would be a more obvious "intervention". Wnt (talk) 07:43, 1 August 2014 (UTC)[reply]

While I mostly agree we shouldn't think of most stuff as purely unhealthy, there's also a matter of degrees here. A key point is that certain ingredients like sugar (including HFCS) can be considered problematic because they themselves are likely to be a problem if used in sufficient quantities. And it's not surprising if they will be used in such quantities precisely because they mostly contribute basic nutrients (carbohydrates in the case of sugar/HFCS).

Something like MSG shouldn't be put in to that category because there's limited evidence it's actually much of a problem. Of course if you use too much, it may become a problem, probably because of the sodium but I don't know how likely it is to be used in such quantities since I suspect it will just make things taste bad if used too much. In fact, a lot of the time people are probably adding sodium chloride with their MSG so it's even more questionable to claim it's a problem. (The secondary effects claimed for MSG appear to be very poorly supported.)

Snack food or fried rice or whatever with MSG may not be particularly healthy but the MSG is at best, probably only a minor contribution to what makes it healthy (the high levels of fat, sodium only some of which probably comes from the MSG and lack of much fibre or many micronutrients are what makes it problematic).

By comparison something like fudge or soft drinks, where the refined sugar (or HFCS) is a key part of what makes it unhealthy even if the lack of fibre and micronutrients also contributes and it obviously depends on quantity.

Of course if you eat a healthy diet, even if have a small soft drink or piece of fudge every other day, you'll still have a better diet than someone who eats a cheese burger and fried chicken every day with little vegetables, fruit etc even if the second person doesn't eat fudge or drink soft drinks, but that's somewhat missing my point.

BTW, as for sodium, I agree people have traditionally overestimated how bad it is. However there are clearly people for who it's a problem. And I think there is some decent evidence a very high level that isn't uncommon in certain diets probably does have sufficiently negative health effects with few positive effects that it's fair to say it can be a problem.

Nil Einne (talk) 15:59, 2 August 2014 (UTC)[reply]

Sodium is a very healthy ingredient - without it in your food you will die, horribly. DuncanHill (talk) 04:12, 1 August 2014 (UTC)[reply]

Not sure you need any in your food. If you have a water softener, for example, and drink the tap water, then you have salt in your water. And for everyone else, you probably don't need any added salt in your food, as some foods have plenty, like saltwater fish and seafood. It would be rather difficult to suffer from a sodium deficiency in the West these days, and would require quite an effort on your part, unless you have some biological inability to absorb it. StuRat (talk) 13:51, 2 August 2014 (UTC)[reply]

You really should look to sources - saltwater fish do not have higher sodium, nor is fish a generally high sodium food: [2], [3], [4], [5], [6], [7], [8] (varying degrees of quality). You may also notice that sea fish do offer potassium and omega-3 fats, which are good for blood pressure and reduced cardiovascular issues - in other words, sea fish != sodium, but may equal heart healthy. As for adding salt to food, the majority of sodium comes from prepackaged meals, if you cut out low quality prepackaged processed junk and cook for yourself (instead of eating out), you don't have much to worry about. As for low sodium intake, there is controversy, these [9], [10], [11], [12], and [13] demonstrate that low sodium diets can be risky (and, then , there's the other 10, or so, cites from the "Salt Poisoning" question I mentioned/responded to earlier). Of course, I can find cites indicating the opposite, so take with a grain of salt (:-)); but, it is not universal that low sodium is healthier than reasonable sodium intake levels, and could be less healthy. Finally, as mentioned, the major culprit in high sodium/added sodium cases is low quality prepackaged food eaten in excess - indeed, a lot of the issues involving nutrition, actually, are a result of this. --I'm not trying to be a giant jerk, just a topic that I'm passionate about.Phoenixia1177 (talk) 15:31, 2 August 2014 (UTC)[reply]

I never claimed that fish was a high sodium food, only that it contains enough sodium to meet our dietary sodium requirements. In terms of how much sodium Americans consume, this would actually be a considered a low sodium food, while in terms of what we actually need, it's not low at all. StuRat (talk) 15:44, 2 August 2014 (UTC)[reply]

No, you're right, I did misrepresent what you said - not on purpose, I was in a hurry, read it quickly, and responded poorly. I apologize for that - and you make a good point, while sodium is not the boogeyman it is portrayed in many cases, for the normal American it is irrelevant as they are, already, getting more than any safe limit (and can get within a safe lower limit without going out of their way). Again, I apologize, it was entirely my mistake due to a hasty read, over passionate interest, and too many open tabs:-)Phoenixia1177 (talk) 21:51, 3 August 2014 (UTC)[reply]

Unfortunately I think researching exactly this kind of question on the internet will actually come up with far more baloney than fact. With popular blogs like “the food babe” created by scientifically illiterate self-proclaimed diet “experts” who literally have no idea what they are talking about. Proclaiming ingredients are bad or even dangerous based on how “scary” they think the chemical sounds (see Azodicarbonamide). I’m with Nil Einne on this one. Basically, avoid too much of anything. People see to be very quick to blame their health issues on ingredients, "oh, I'm fat because of HFCS", while they drink a gallon of soda a day. Vespine (talk) 04:22, 1 August 2014 (UTC)[reply]

I have one for the list, partially hydrogenated vegetable oils. Those added trans fats are completely unnecessary for life, unlike sodium, and I don't think anyone argues that they are healthy. Yet, here in the US, they remain in half the food we buy, because they don't tend to spoil (maybe the bacteria don't recognize them as food, either). Incidentally, I just now picked the croutons out of my salad from Applebee's, because they are full of trans fats. StuRat (talk) 04:46, 1 August 2014 (UTC)[reply]

Croutons in salad? Their natural environment is soup. DuncanHill (talk) 05:50, 1 August 2014 (UTC)[reply]

Croutons are quite common in salad in the US. I always ask for them to skip those, knowing they are likely laced with trans fats, or at least saturated fats and carbs, making my healthy salad into junk food. Unfortunately, Applebee's ignored my request. StuRat (talk) 11:27, 1 August 2014 (UTC)[reply]

According to the overview of the most recent version of the Dietary Guidelines for Americans, the six food components they recommend eating less of are sodium, saturated fats, trans fats, cholesterol, added sugars, and refined grains.[14] In addition, the full guidelines also lists alcohol. For details, see Chapter 3 of the full guidelines, "Foods and Food Components to Reduce".[15] Red Act (talk) 06:41, 1 August 2014 (UTC)[reply]

True, but that guideline of "reducing" is built around the idea that for the average American their intake of those nutrients is too large. Each of those, save transfat and alcohol, are necessary in some quantity - and for sodium, saturated fat, and cholesterol, I've read decent arguments for each as to why they aren't outright bad for you and ought not be demonized. Refined grains are another interesting case, the recommendation to "eat less" is not because they are bad, in themselves, so much as people are not eating any non-refined ones; it's predicated on the assumption that they end up replaced with better sources, for various reasons. The general problem isn't "these are bad", it's "people eat 3 times the calories they need and are doing so from cheap low quality foods - what can we do?". The mentioned things are only bad because of the excess of consumption and general lack of exercise - in various athletic endeavours, each of those substances (save the two I excluded) has a place in the diet and a value; recommending, globally, that people avoid these gives people very bad misinformation about how nutrition works - this is you get people who buy "whole grain" bread, eat a loaf a day with their "organic low sodium low fat" fillings as sandwiches and stay unhealthy; the name of the game is moderation and education, not "avoid these, they're real bad!".Phoenixia1177 (talk) 07:08, 1 August 2014 (UTC)[reply]

And, and to Stu above, after a little looking, turns out that not everything called "transfat" is bad either, see: [16], [17], Conjugated linoleic acid, and Vaccenic acid. Of course, this is not to say that the PHVO is good, or required, or that it contains these and should be consumed because of - just that, once again, you can't give blanket statements like "transfats aren't good, avoid".Phoenixia1177 (talk) 07:24, 1 August 2014 (UTC)[reply]

The answer would be incomplete without a redirect to Demolition Man, but it is more essential to understand the component of sin in a sin tax. Sin emanates from poverty, and can only be expiated by taxing the poor. Thus, while all men die, even at roughly the same time, a program like this can only succeed if the lower classes are taxed to the point where a single person's food is very nearly unaffordable; and indeed only to the degree that it is unaffordable the penalty of sin is paid. The revenue collected from these per capita taxes can be used, first and foremost, to be certain that the blasphemy of taxation against the rich is avoided, then further to compensate them for the Sun-like social grace they shed upon us all by being rich, for instance, by granting them modest millions for producing public service announcements calling on the poor to turn over their hoarded food. And yet, poverty is so tenacious! that after such healthful bloodletting the poor are even poorer, and poverty as always correlates directly with obesity.^[18] Like the War on Drugs, the loyal fighter must perceive that the battle can be won only through taking the harshest measures to assure a final solution to the problem. Wnt (talk) 07:26, 1 August 2014 (UTC)[reply]

Regarding cholesterol, I believe a distinction must be made, with LDL cholesterol and triglycerides (not cholesterol themselves, but related) being bad and HDL cholesterol being good. Unfortunately, current labeling in the US fails to distinguish the good cholesterol from the bad. StuRat (talk) 11:23, 1 August 2014 (UTC)[reply]

Food labeling doesn't distinguish because dietary cholesterol has almost no influence on blood cholesterol. See Cholesterol#Physiology. --Carnildo (talk) 01:37, 2 August 2014 (UTC)[reply]

Then why require the total amount to be listed ? The US gov seems to think it's important, as they recommend reducing cholesterol intake. Given that, I'd like to concentrate on reducing my intake of bad cholesterol only. StuRat (talk) 13:54, 2 August 2014 (UTC)[reply]

I'm sorry, on what basis are you disagreeing? See: [19], [20], [21], [22], [23], and [24]. Dietary cholesterol does not appear to have any impact on health risks in otherwise healthy individuals. As with sodium and fat (and carbs), this is another case of picking out a single nutrient and making it a "boogeyman", as opposed to actually educating a populace about nutrition. I'll say it again: there are no simple fixes like "avoid this!", if you want to be healthy: you need to eat in moderation with an awareness towards all nutrient levels, exercise, sleep regularly, manage stress, and avoid addictive damaging substances. Of course, those things are real hard, so we, in America, have a nation of people looking for shortcuts; and the evidence is clear that those shortcuts just don't work.Phoenixia1177 (talk) 14:43, 2 August 2014 (UTC)[reply]

I already explained my basis for disagreeing, the US government recommendations. They were linked to by a previous responder, but here they are again: [25]. That was in 2010. Has the science showing dietary cholesterol doesn't matter emerged since then ?

Also, your 2nd source says "Although numerous clinical studies have shown that dietary cholesterol challenges may increase plasma LDL cholesterol in certain individuals, who are more sensitive to dietary cholesterol (about one-quarter of the population), HDL cholesterol also rises resulting in the maintenance of the LDL/HDL cholesterol ratio, a key marker of CHD risk." Then, logically, if I am one of those individuals, wouldn't consuming more good cholesterol and less bad cholesterol improve my LDL/HDL ratio ?

And your 4th source says "For much of the past 50 years, a great deal of the scientific literature regarding dietary fat and cholesterol intake has indicated a strong positive correlation with heart disease. In recent years, however, there have been a number of epidemiological studies that did not support a relationship between cholesterol intake and cardiovascular disease." I get suspicious when a well-established science is overturned by new studies. How were these studies funded ? Specifically those advocating eating more eggs had better not have been funded by the American Egg Board: [26]. StuRat (talk) 15:15, 2 August 2014 (UTC)[reply]

I'll look into the ldl/hdl question later (I have a birthday party to attend for a cousin at the moment) - but, I don't think a vague worry over egg council funding, recentness of studies, and a US dietary guideline support a great deal of dispute with anything posted by me; moreover, I'm quite positive I could dig up 10 more papers if I had to (which I don't believe I do). But, while the specific point is "Cholesterol isn't as bad as you've been told", the general point I'm making here is this: "Don't eat low quality preprocessed junk food for every meal, make your own food from decent ingredients, exercise" - that's the root of being healthy, not avoiding sodium/fat/cholesterol/carbs/etc. The latter are all things that you want to be aware of (as are all nutrients), but none of them are poisons, nutrients and nutrition are something we should be using, in an educated manner, to fuel our activities and increased health through exercise; they are not something to be fearful of, nor are they culprits causing us to become unhealthy. How many people do you know who the following sentence applies to, "Oh yes, he works out every day, uses all natural ingredients, get's good rest, isn't stressed, manages an appropriate caloric intake...but he's so out of shape because he eats two eggs a day and uses the salt shaker."? Unless you have an underlying disorder, that's just not going to apply.Phoenixia1177 (talk) 15:47, 2 August 2014 (UTC)[reply]

All of your sources regarding eggs being healthy looked rather similar, making me suspect they aren't all truly independent studies. I certainly agree that eating healthy foods and cooking from scratch is the ideal, but that pretty much means never eating at a restaurant, at least around here. People in my family all seem to have sodium sensitive hypertension, so yes, even if we ate food made from scratch using all natural ingredients we'd still feel sick if we poured too much salt in the food we make. I also get acne whenever I consume more than about a gram of trans fats, and never otherwise, so I certainly do think we need to watch for specific ingredients added to our foods. Trans fats in particular can be in foods you'd never suspect. Cold Stone Creamery, for example, adds trans fats to all their ice cream. Now, I don't have any particular immediate symptoms from consuming either HDL or LDL cholesterol, but based on my experience with sodium and trans fats, I'm not willing to just ignore the harmful or helpful effects they could have. StuRat (talk) 00:19, 3 August 2014 (UTC)[reply]

BTW, is the birthday cake for the party all made from scratch from organic ingredients ? StuRat (talk) 00:38, 3 August 2014 (UTC) [reply]

Another perspective: nothing is inherently unhealthy about any of the ingredients listed above. The dose makes the poison. E.g. as mentioned, zero sodium diets would be eventually lethal, but so will massively high sodium diets. To understand effects of food on health, one must consider the diet as a whole. SemanticMantis (talk) 16:12, 1 August 2014 (UTC)[reply]

I disagree. Partially hydrogenated vegetable oils are inherently unhealthy and completely unnecessary, in any quantity, in the human diet. StuRat (talk) 22:33, 1 August 2014 (UTC)[reply]

As far as a tax on unhealthy ingredients, I see a problem. If there was a tax on salt, wouldn't a bag of road salt be absurdly expensive ? If not taxed, how about a canister of salt for refilling salt shakers ? Seasoned salt ? Celery salt ? Garlic salt ? A canister of dried Parmesan cheese, which is used as a condiment, and also heavily salted ? Pickles, used the same way ? Potato chips, used the same way ? French fries ? Chili cheese fries ? Wherever you draw then line, those manufacturers of foods on the wrong side will be angry. StuRat (talk) 22:39, 1 August 2014 (UTC)[reply]

Apparently, wiener protein tends to rapidly accumulate in the throats of children, whether it's salty or not. And yes, I could have phrased that differently. InedibleHulk (talk) 23:02, 1 August 2014 (UTC)[reply]

You pervert!.. 24.5.122.13 (talk) 00:08, 3 August 2014 (UTC)[reply]

The only way to keep your health is to eat what you don't want, drink what you don't like, and do what you'd rather not. Mark Twain (talk) 14:05, April 27, 1872 (UTC)

If you have untreated onychomycosis, but use athlete's foot prophylaxis daily, is swimming OK?

One of the reason we don't answer medical advice-type questions is that we don't want to be liable or to harm anyone through our ignorance. But that's only one reason - the other reason we don't do it is that we're not doctors and we don't know the specifics. We can't see the infection, don't know the history, aren't sure of the diagnosis, aren't schooled in the latest information about transmission rates, and so on. I also appreciate your attempts to fictionalize this question, but we're still not able to answer it properly. It's not just that we shouldn't; we are also unable. Matt Deres (talk) 16:18, 1 August 2014 (UTC)[reply]

The following discussion has been closed. Please do not modify it.

Imagine a man by the name of John Doe. This man:

Has had distal lateral subungual onychomycosis for years.
Is otherwise in 100% perfect health.
Uses topical antifungal medication daily to prevent athlete's foot.
Was advised by his doctor not to treat the onychomycosis, so as to avoid the possible adverse effects of systemic antifungals.

He wants to go swimming with some friends, but doesn't want them to catch anything.

Public Health Queensland says that nobody with untreated athlete's foot should swim.[27] Even in chlorinated pool water, dermatophytes survive for months or longer.[28] "But," John thinks to himself, "I don't have athlete's foot. Maybe onychomycosis is different. Anyway, even if I do swim despite my infection, I surely won't be the only one to have done so lately."

(Note: Using Google, I found a second article about fungal infections which also mentions swimming pools. I have no idea whether or not it's relevant here. My public library doesn't offer me access. Maybe I'll email one of the authors and ask for a copy I can post online.)

Anyway:

Is it fine for John and friends to swim in a chlorinated public swimming pool?
Or in a nearby river?
How about in a natural pond?
What if John covers his feet with transparent plastic bags, and covers the bags with water shoes?

P.S. Feel free to edit this post. You can even make major changes if you like.

Regards, —Unforgettableid (talk) 07:44, 1 August 2014 (UTC)[reply]

While I do appreciate the phrasing in terms of John Doe, the specifics of this question do amount to asking for medical advice - even if it is entirely in earnest about a fictional "John Doe" the only answer would amount to medical advice for any reader that fit the above. Phoenixia1177 (talk) 08:12, 1 August 2014 (UTC)[reply]

Dear answerers:

I think this is a borderline case. And so the question should not be hatted: please see the relevant guideline section. Each responder should form his or her own opinion on whether or not the question is seeking treatment advice. Any answer which provides treatment advice should be hatted or removed.

(Dear all: What do you think? Does the question seek treatment advice, or is it borderline, or is it acceptable?)

Plus, keep in mind that the question does not relate to heart disease or liver failure or anything really serious. It's only about a fungal infection in a healthy John Doe, which is much less serious.

Please see also Kainaw's words.

Cheers, —Unforgettableid (talk) 12:48, 1 August 2014 (UTC)[reply]

Latex condom

Why is it that when latex condoms tear while it is being used, they completely tear open? Are they designed this way? Is it the same theory as cutting a stretched elastic band which snaps or popping a balloon which makes it break open? 176.254.45.139 (talk) 09:26, 1 August 2014 (UTC)[reply]

Once a tear starts, all the force is then applied to the damaged front ends of the tear, which is much more than when it was spread out relatively evenly over the entire surface, so it would be difficult to stop it. However, I have seen some plastics that seem to somehow stop tears after a certain distance, even when the same force is applied. I'm not sure how they do it.

There could also be a case made for making condoms "tear evident", so that the users know a tear occurred and take other measures to prevent pregnancy and STDs (morning after pill, showering, douching, etc.). StuRat (talk) 11:06, 1 August 2014 (UTC)[reply]

We have a stub article on tear propagation, and here are some additional references on how tear initiation and propagation can be tested [29] [30]. I don't believe that this behavior in latex condoms is by design. It is, as you say, similar to how a balloon breaks, and due to the concentration of force after tear initiation, as Stu described. There is some info at Condom#Causes_of_failure. One way that tear propagation is commonly halted is through reinforcing with another material, see e.g. ripstop nylon. However, It's not clear that ripstop condoms would have any advantage, even a pinhole is enough to compromise the intended function. SemanticMantis (talk) 16:08, 1 August 2014 (UTC)[reply]

The most common cause of condom breakage is artificial lubricants or other substances which dissolve latex. Water based lubricants usually do not, but people often use oils and other substances which do. 104.128.96.117 (talk) 20:02, 1 August 2014 (UTC)[reply]

Are dark cars hotter than other colors?

Did someone studied scientifically how big the difference is? OsmanRF34 (talk) 22:19, 1 August 2014 (UTC)[reply]

They certainly should absorb more sunlight and change it into heat, however, they may also radiate more heat, so might cool down faster at night. But, assuming conditions are such that any car would absorb more heat than it radiates, then a darker car should get hotter faster, and reach a higher max temp. A darker interior might also make more difference than the exterior color, since interior heat doesn't have to pass through the surface to heat the vehicle. I use reflective window car shades to keep the car from getting hot when parked in the sunlight, but white would work, too. StuRat (talk) 22:24, 1 August 2014 (UTC)[reply]

Most definitely yes. I used to live in Phoenix, and built a VW-based off-road vehicle, and decided to paint it in two-tone. I chose for the part that included the roof, an industrial "zinc white" (catalyzed urethane) and for the lower part, "cobalt blue". On a hot day (115+ F° is not unusual there) you could put your hand on the (white) roof without burning it, but on the (blue) hood, you could literally fry an egg. As for a "scientific study", you shouldn't have much trouble finding such from paint manufactures, etc., but "how much" depends on many factors. —71.20.250.51 (talk) 01:45, 2 August 2014 (UTC)[reply]

There are certain reflective buildings that melt cars. They're not themselves hot, just playing the middleman. In cases like those, the shininess is more important than the brightness of the colour. Like a building heats a car, a shiny white car can heat a nearby person without becoming so hot itself. By our senses, the hotter black, dusty car should be the more comfortable to stand by, but not sit on.

No idea about the interior. InedibleHulk (talk) 02:03, 2 August 2014 (UTC)[reply]

Note the recent practice in the US of painting school bus roofs white, as that is supposed to reduce heating considerably versus "school bus yellow". (They leave the rest yellow, so it's still recognizable as a school bus.) If they painted it black, presumably the kids would be well roasted, with the meat falling off their bones, by the time they got home. :-) StuRat (talk) 13:38, 2 August 2014 (UTC)[reply]

Possibly why decent gingerbread houses are pitched with molasses and shingled with dark chocolate squares. I doubt you can get the meat off without a cauldron, but it'd certainly soften them up for a stew, Stu. InedibleHulk (talk) 23:28, 2 August 2014 (UTC) [reply]

Remember the housewife who wrote that most of her time goes into "cooking the kids and the family"?

If you're wondering: it was a case of "Punctuation: Use It", not a "humanitarian" diet, so she wouldn't appreciate the black-roof bus either. - ¡Ouch! (^{hurt me} / _{more pain}) 10:54, 4 August 2014 (UTC) [reply]

what is worse, frontal crashing at 100 mph against a car exactly like yours driving at 100 mph or crashing at the same speed against a non-deformable wall?

OsmanRF34 (talk) 22:49, 1 August 2014 (UTC)[reply]

At those speeds they are both likely to be fatal. At lower speeds, I'd expect both to be just about as bad, although the two vehicle situation will almost certainly result in rotation, as they can never hit exactly straight on. StuRat (talk) 23:01, 1 August 2014 (UTC)[reply]

A typical physics excercise. Assuming perfect symmetry, there's theoretically no difference between the two scenarios. Imagine a thin paper sheet exactly between the two cars. That sheet of paper will not move at all, as it's being pushed equally from both sides. Therefore from the perspective of each driver the situation is equivalent to crashing into an immovable wall. - Lindert (talk) 23:08, 1 August 2014 (UTC)[reply]

That's a typical physics-exercise answer. But in most cars the left and right sides are not the same, because there is only one set of driving controls. Since a head-on collision puts the left side of each car against the right side of the other, the imaginary paper sheet will move, although it will do so in a symmetrical manner (for example, perhaps forming an S shape as seen from above). --69.158.94.114 (talk) 00:04, 2 August 2014 (UTC)[reply]

Worse to hit another car, because there's another driver (at least) in it. If you survive, there are a lot of probable legal and financial problems that hitting a wall doesn't pose, even if only the cars are hurt. Insurance rates are partly determined on the accident history of the makes and models, so destroying two of the same at once is marginally worse, if you intend to insure a third. InedibleHulk (talk) 23:14, 1 August 2014 (UTC)[reply]

This is a great chance to review the difference between elastic collisions and inelastic collisions...

Perfectly elastic collisions conserve kinetic energy and momentum. In those cases, whether the impactor hits a a brick wall or experiences an equal-energy collision with another moving object is pretty irrelevant.

Inelastic collisions conserve momentum but dissipate the energy by deforming the impactor. This changes the situation pretty gravely.

Because automobiles are usually made out of metals, plastics, and glass, they not very elastic. So, they will inelastically deform - and exactly how they deform will depend strongly on whether they hit a wall or hit another vehicle. Complex engineered crumple zones will crush; rigid metal structures and glass parts will undergo brittle failure or ductile deformation; connective parts will shear or snap...

Momentum must be conserved, but energy can be dissipated in an inelastic collision. When a car hits another car, momentum can be conserved by bringing both vehicles to a halt. But, if a vehicle hits a wall, and the wall is "really immovable," then the momentum can only be conserved by disintegrating the vehicle. Relative to the other scenario, parts will go flying with much higher momentum. Nimur (talk) 23:24, 1 August 2014 (UTC)[reply]

I agree with Lindert that, assuming perfect mirror-image symmetry in the two-car scenario, the two scenarios are theoretically identical as to what will happen on the car side of the plane of collision. This was explored experimentally in the "Mythssion Control" episode of Mythbusters, which came to the conclusion that the two scenarios resulted in equal damage to the one car. Red Act (talk) 00:20, 2 August 2014 (UTC)[reply]

Well, at some point, "immovable wall" and "non-deformable wall" are in direct conflict. One, or other, of these statements must break down first. In the real world that we actually live in, both statements break down: the wall will move and deform - perhaps only by a tiny amount - but enough to satisfy conservation of momentum. Nimur (talk) 03:40, 2 August 2014 (UTC)[reply]

Not strictly. The momentum of the car against such a wall could transfer momentum to the entire planet...which of course couldn't be immovable - but would be accelerated by such a microscopic amount, it would be truly negligible. From the perspective of someone nearby, the effect would be effectively the same as a truly immovable object.

But this is a very old question - and the way to do it as a thought experiment is to consider a very thin, easily deformed surface to be placed at exactly the impact point of the two cars. A big sheet of kitchen foil, say. As a thought-experiment, that wall wouldn't move at all because the pressure against it is always the same on both sides (presuming a perfectly symmetrical impact). From the point of view of a car on one side, there is no difference whatever between the aluminium foil "wall" and the huge immovable concrete wall.

So on a very theoretical/thought-experiment level, there is no difference. But when you get down to practical situations, the impact won't every be perfectly symmetrical and the differences between hitting a wall and hitting another car will depend entirely on what those asymmetries are.

However, at a higher level of description, the total impact energy of two cars is twice as much as one - and it's distributed over two cars - so there is twice as much energy-absorbing crumple zones for example. So the amount of damage averaged over the two cars will be the same as if they'd each individually hit a brick wall.

SteveBaker (talk) 05:12, 2 August 2014 (UTC)[reply]

OTOH, If you want to fold a sheet of paper twelve times, you should first place it between the two cars, to hammer it as thin as possible. With the single car and hard wall, you could "only" fold the sheet 11 times.

Why did I come up with that? It was another Mythbusters episode. They used a huge sheet and, to say the least, "exotic" folding equipment, including a steamroller. - ¡Ouch! (^{hurt me} / _{more pain}) 11:00, 4 August 2014 (UTC)[reply]

Surely the two situations are nothing like equivalent: the one with the wall involves only half as much kinetic energy as the one with the other car. Or to express it another way: your motion relative to the second car is twice as fast as with respect to the wall. AlexTiefling (talk) 11:41, 4 August 2014 (UTC)[reply]

The same amount of energy goes toward destroying your car either way. For simplicity, I'm going to assume that cars collide completely inelastically in a collision, which is a good first order approximation.

If you initially travel at a speed of v=100 into a stationary, absurdly impervious wall, your initial kinetic energy is 1/2 m 100² = 5000 m, you wind up with no speed and hence no kinetic energy at the end, and that absurdly impervious wall doesn't budge to absorb any of your kinetic energy, so all of that 5000 m of initial kinetic energy goes toward destroying your car.

In the case of two cars, you seem to want to work in a frame of reference in which the other car is initially at rest, which is fine, so I'll do that. In that frame of reference, the other car has no initial kinetic energy, and since in that frame of reference your car has an initial speed of v=200, your car has an initial kinetic energy of 1/2 m 200² = 20000 m. The center of mass of the two cars moves at constant speed, so after the collision, both cars are moving at a speed of v=100 as measured in that reference frame in which the other car was initially at rest. I.e., after the collision, in the chosen frame of reference, your car and the other car each have a final kinetic energy of 1/2 m 100² = 5000 m that did not go toward destroying the cars, leaving an initial kinetic energy of 10000 m that did go toward destroying the cars. Each car uses up half of that car destruction energy. I.e., 5000 m of energy goes toward destroying your car, which is the same number as with the wall. Red Act (talk) 12:32, 5 August 2014 (UTC)[reply]