Wikipedia:Reference desk/Archives/Science/2011 August 6

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August 6

I've read that children dislike vegetables because they're bitter?

I don't see it in the vegetable article though. I'm also wondering if cooking vegetables change their bitterness, if any. Thanks. Imagine Reason (talk) 00:14, 6 August 2011 (UTC)

Most vegetables don't have much bitterness. The most widely eaten exception is spinach; chard and other greens are even more bitter. In Asian cuisine bitter melon is commonly used, and it's a lot more bitter. There are many more bitter spices than vegetables. Looie496 (talk) 00:37, 6 August 2011 (UTC)

Possibly relevant: slow acetylator. --Trovatore (talk) 00:44, 6 August 2011 (UTC)

... except it's a redlink; WADHAAOE. I'm shocked. --Trovatore (talk) 00:45, 6 August 2011 (UTC)

There is mention of the concept at Drug metabolism, Pharmacogenetics, N-acetyltransferase 2, Nutritional genomics and a bunch of articles on drugs and other stuff. One of these may be suitable as a redirect target, at least for now. Nil Einne (talk) 11:50, 6 August 2011 (UTC)

Children dislike vegetables because vegetables don't taste as well as sweets, cookies, icecream, cake etc. Count Iblis (talk) 01:06, 6 August 2011 (UTC)

There are other reasons not to like veggies. Some are tough, and cooking can help there. Adding fat, like butter, can also make them "go down easier". Some people also have a genetic tendency to dislike cruciferous vegetables, like broccoli. And, perhaps by bitter you meant "not sweet". In that case, they may like some of the sweeter veggies, like carrots and beets, or adding a sweet salad dressing to the rest. StuRat (talk) 01:08, 6 August 2011 (UTC)

Or just follow Amy Chua's advice. :) .Count Iblis (talk) 01:50, 6 August 2011 (UTC)

I guess you're thinking of supertasters Nil Einne (talk) 11:55, 6 August 2011 (UTC)

I refer to this sentence from the article to which I linked: "It has been found that cruciferous vegetables are less likely to be eaten by people who can taste PTC, due to the existence of compounds related to PTC in such vegetables." StuRat (talk) 04:11, 10 August 2011 (UTC)

Cooking can sweeten onions by caramelizing them, so yes cooking can help sweeten the pot. Still, with kids, sometimes their preferences must be acquired with time, as they get older. For instance, it can be difficult to eat something if one associates it with an illness, pest or an odd sensation. For a while, I would refuse to eat raisins from a box after having found ants in one. Similarly, for a number of years, I would relive being sick whenever I smelled macaroni and cheese. But I eventually realized these aversions were silly and now, like most adults I think, enjoy foods I may have shunned. With any food it helps if its prepared well, especially by a great cook. For instance, care must be taken to not over-cook any veggie into a bland mush (and even uncooked celery or a carrot needs a good dip). Various soups and side dishes are satisfying, but my preference has always been the casseroles my mom made. She mixed veggies such as carrots, beets, spinach, broccoli, and cauliflower with other ingredients such as cheese, chicken, pasta and potatoes. Her rhubarb cobbler is out-of-this world too. --Modocc (talk) 03:25, 6 August 2011 (UTC)

To begin with some subjective opinions, as someone still repulsed by raw onions to this day, I'd say it's not merely a matter of caramelization - maybe it's the breakdown of allicin or related compounds with a strong stench. But as a child I was much more sensitive to such scents - even smelling a bit of it in the tiny bits of onions in commercial spaghetti sauce, where I'd think every last molecule had been decomposed.

But my reaction to almonds was much, much weirder. As a child I was incredibly sensitive to a terrible, oily smell in them - something like a cigarette which to merely touch it for a moment left a reek on my fingers that took soap and hot water and scrubbing to clean off. But when I was around 15 the scent became much less pronounced, so much so that within a year or two I could actually eat a few experimentally. Within a few years after that, the scent became so weak that they became an acceptable snack, and after a decade or two the scent was truly undetectable. I'm thinking that there must be odorant receptors which are activated by promoters that shut off in adulthood. Wnt (talk) 05:01, 6 August 2011 (UTC)

But the next question is "Why ?". What evolutionary path would lead to almonds being objectionable to some children, but not to adults ? Are they actually harmful to some children, perhaps due to the cyanides present in small quantities ? Maybe those chemical stunt some growth process at low levels ? StuRat (talk) 05:21, 6 August 2011 (UTC)

I wonder if diversity in food preferences actually represents an evolution of the scientific method. If some people in a tribe eat a food and others don't, people might recognize that the food is responsible... Wnt (talk) 13:43, 6 August 2011 (UTC)

Children are know to try a lot of things, and hence are at higher risk from dangerous foodstuff. Adults will have learned to be more discriminating. Also, once you're past 25, you're supposed to have done your bit for the propagation of the species, of course, so evolution wouldn't give a hoot if you jumped off a cliff ;-). --Stephan Schulz (talk) 08:50, 6 August 2011 (UTC)

If you jumped off a cliff at 25, your 5 children would starve. :(

You should be 45 at least before you jump off a cliff I think. Rckrone (talk) 22:24, 6 August 2011 (UTC)

You should be well past 70, and have walked your children through all the stages of parenting, long before you consider tetherless bungee jumping. μηδείς (talk) 03:42, 7 August 2011 (UTC)

We do have an article, perhaps not that useful, on Selective eating disorder Nil Einne (talk) 11:52, 6 August 2011 (UTC)

Humans have evolved as Omnivores and thrive on a balanced diet of plants and animals. However catching animals is harder than picking plants because plants don't run away. To compensate for the difference and favour a balanced diet, instinct gives a greater pleasure reward from eating animal products than vegetables. Cuddlyable3 (talk) 13:16, 6 August 2011 (UTC)

I've read, and it seems more probable, that we like meat because it is a far more efficient way (for us, not the energy producers) to obtain calories and some other nutrients. We should always be mindful of culture as well. Imagine Reason (talk) 20:19, 10 August 2011 (UTC)

Vegetables are not bitter, unless you are not cooking them properly or are a supertaster. I had no problems eating vegetables when I was a kid. I understand that in the US almost everything has sugar added to it: perhaps you are describing the rare taste of something sugar-free. Update: when years ago I used to take sugar with my tea, then tea without sugar would taste unpleasant, "bitter". But after very gradually over years reducing the sugar in my tea to nothing, sugarless tea does not taste bitter at all, but nice. Now I much prefer sugarless tea. 92.28.252.178 (talk) 15:36, 6 August 2011 (UTC)

Alkaloid toxins are generally bitter. And it certainly doesn't help a poisonous plant to taste good and be eaten up before it kills you. μηδείς (talk) 03:42, 7 August 2011 (UTC)

I'm surprised that no other old fart has yet responded with something along the lines of "The kids of today have too much choice. When I was young we ate what was put in front of us or went without." It was certainly true in my case, and I suspect for most of human history for most people. Having a choice of foods at every meal, and in between meals, is the unnatural thing here. Maybe we should get deeper into this issue of actually having this choice. It would have been rare in the past, and maybe there was a point to our preferences when it occured. HiLo48 (talk) 03:49, 7 August 2011 (UTC)

A choice of foods is fine, provided they are all healthy, and, in some cases, kids may crave foods containing nutrients they lack. However, the choice between eating healthy food or junk food should be denied to those too young to make the responsible choice. StuRat (talk) 17:12, 9 August 2011 (UTC)

Judging by the waistlines I see, the age of responsible choice seems to be somewhere in the mid 70s. Googlemeister (talk) 14:37, 10 August 2011 (UTC)

And, even then, the lack of obese elderly people isn't due to them having attained self-control so much as the obese dying (or losing weight due to disease or out of fear of imminent death if they don't). StuRat (talk) 17:00, 10 August 2011 (UTC)

About a decade ago, a book call Why We Get Sick was published where the authors attempted to illustrate how evolutionary pressures need to be taken into account when dealing with any kind of sickness, disorder, etc. I'd have to flip through it to find the exact reference, but they discussed this very topic and (IIRC) stated outright that children by and large dislike many vegetables because of the bitterness. Unlike cooked animal flesh, which (barring allergies or infections) is basically always safe to eat by all people, plants can be toxic to eat. In fact, many plants we eat are exactly that, but we've become accustomed to it and call it a "flavour". Examples there include hot peppers, mint, and other strong spices/herbs where the oil we consider flavourful is simply a part of a pesticide control program by the plant. What the authors posit is that many vegetables have a very mild bitterness as part of their own pest control solution. As adults, we barely notice that bitterness, but children, who are much more susceptible to eating toxins, notice it much more easily. In essence, not liking your broccoli or spinach is the end result of evolutionary pressure on kids to not eat too many strong tasting plants to reduce the risk of consuming toxins. How correct the premise is, I don't know, but it's an interesting theory and you may want to hunt up that book for a proper understanding (it's been a long while since I read it). Matt Deres (talk) 17:20, 9 August 2011 (UTC)

cosmic strings

what are cosmic strings? — Preceding unsigned comment added by 175.110.242.217 (talk) 02:46, 6 August 2011 (UTC)

They are topological defects of space-time. As you can see stated on the first line of the article cosmic strings. Hair whorls are familiar examples of a topological defects. Dauto (talk) 03:16, 6 August 2011 (UTC)

pretzel making

What are the byproducts after baking of submerging pretzel dough in sodium hydroxide (or potassium hydroxide) to produce a glaze? --DeeperQA (talk) 10:45, 6 August 2011 (UTC)

Water. See Neutralization (chemistry). Plasmic Physics (talk) 12:18, 6 August 2011 (UTC)

The above may be true for lye as a reagent, but it would also be good to consider its role as a catalyst. It should be clear from the formation of the crust that there's been substantial chemical change in the dough, but I didn't find much of interest on NCBI (only PMID 14733520, which is more about what the lye prevents by neutralizing acid). And nothing on Google. But there's a lot of information out there - there are probably specialized food resources that I don't know about. Wnt (talk) 14:37, 6 August 2011 (UTC)

The Maillard reaction, one of the reactions involved in the browning process, is affected by pH (enhanced under alkaline conditions). I assume other related reactions are affected as well (not sure which other specific ones are accelerated or slowed). DMacks (talk) 16:35, 6 August 2011 (UTC)

Caramelization is also affected by pH (and also enhanced under alkaline conditions)--I just added that content (with ref:) to its article. DMacks (talk) 17:48, 6 August 2011 (UTC)

space/time, energy/matter

Is it safe to say that space/time is the only place energy/matter is located? --DeeperQA (talk) 10:50, 6 August 2011 (UTC)

Yes. Plasmic Physics (talk) 12:15, 6 August 2011 (UTC)

Better to say that it's the only place that we know about. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:46, 7 August 2011 (UTC)

That can be said about any scientific extrapolation. Plasmic Physics (talk) 23:15, 7 August 2011 (UTC)

Bingo! ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:24, 7 August 2011 (UTC)

gravity

Is there any time or place where gravity does not or did not or will not exist? --DeeperQA (talk) 10:52, 6 August 2011 (UTC)

Depends what you mean by "exist". Does zero gravity answer your question?--Shantavira|^{feed me} 11:08, 6 August 2011 (UTC)

No, gravity fields extend indefinitely into space-time, like electric and magnetic fields. Plasmic Physics (talk) 12:21, 6 August 2011 (UTC)

Yes, see Lagrangian point. Cuddlyable3 (talk) 13:05, 6 August 2011 (UTC)

Isn't there plenty of gravity at Lagrangian points, but just pulling in the right way to keep in orbital sync? 81.159.105.227 (talk) 13:34, 6 August 2011 (UTC)

Yes, you are right. Dauto (talk) 14:35, 6 August 2011 (UTC)

Yes. If there was no gravity, the object would fly off into deep space. Objects at L-points are still in orbit around the primary and any orbit needs gravity to close it. --Tango (talk) 21:36, 6 August 2011 (UTC)

No, gravity is still active at a langranian point, it is just a metastable position. Plasmic Physics (talk) 19:26, 6 August 2011 (UTC)

If you were sitting between two galaxies, wouldn't the gravitional pull there be pretty much negligible? ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:58, 7 August 2011 (UTC)

You'd be at a tipping point where you need just the right push to be pulled to either side. That's besides the point thought, there is still gravity. Plasmic Physics (talk) 23:11, 7 August 2011 (UTC)

Sure. What I'm getting at is whether the "pull" of a given object (the sun, for example) is just as strong several light years away as it is where we are now. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:14, 7 August 2011 (UTC)

Obviously not, though gravity is still present, just weaker. Plasmic Physics (talk) 23:39, 7 August 2011 (UTC)

Is the "strength" of a gravitational field, an inverse-square relation? ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:47, 8 August 2011 (UTC)

Yes. And electromagnetism is inverse-cube. --Goodbye Galaxy (talk) 14:16, 8 August 2011 (UTC)

An object inside a hollow spherical shell feels no net gravitic acceleration from the shell because the force exerted by the mass in opposite directions cancels out. Theoretically one could build a shell which adjusted local thickness to counter external influences, effectively shielding out gravity. There would still be the microgravity exerted between the parts of your body. μηδείς (talk) 00:58, 9 August 2011 (UTC)

There was no gravity before the Big bang. There will be no gravity after the Big crush. There is no gravity at the presumed singular points where the gravitational force from all material in the Universe cancels. A suitably shaped object of arbitrary size with its center of mass at such a point would experience no nett gravitational force at an instant of time. I don't know whether it would then start rotating and if so, relative to what. Cuddlyable3 (talk) 15:08, 9 August 2011 (UTC)

While there might be no net gravitational force on such an object taken as a whole, that shouldn't be taken to mean that there is no gravity. Individual particles within our hypothetical object would still feel gravitational attraction to one another. Even if there were just a single particle present, it would still locally distort spacetime through its own gravitational field. TenOfAllTrades(talk) 16:14, 9 August 2011 (UTC)

We don't know what it was like before the big bang, we can say for certain that there was no gravity, and canceling the effects of gravity, doesn't mean that gravity does not exist. Plasmic Physics (talk) 21:50, 9 August 2011 (UTC)

Power outages

Hi. Could recent power outages in the local area been caused by solar geomagnetic storms that hit the Earth? Do those typically cause outages lasting on the order of 1 minute? Is it usually possible to trace or identify the source or otherwise an exact cause of a local outage? Thanks. ~AH1 ^(discuss!) 12:28, 6 August 2011 (UTC)

I doubt it. The geomagnetic induced currents are not that large that they would directly cause problems. You would need circuits of huge areas to get large induced currents. What can happen is that such currents cause tranformer cores to get magnetized, and then the power transmission from the powerplant to the grid becomes less efficient. It is this dissipatated power originating from the powerplant that can destroy transformers. Count Iblis (talk) 17:00, 6 August 2011 (UTC)

What do you mean by "recent"? Our article on geomagnetic storms affirms that they can indeed cause outages, and there was speculation that the storm that struck yesterday/today might be strong enough to have effects, but a quick scan of news doesn't show any specific reports. Looie496 (talk) 20:28, 6 August 2011 (UTC)

It's doubtful that news organizations would report on strings of localized power outages lasting on the order of seconds to minutes without severe effects. ~AH1 ^(discuss!) 23:43, 7 August 2011 (UTC)

distinction between coordinate covalent bond and covalent bond

why does the distinction between coordinate covalent bond and covalent bond vanishes after bond formation in NH4+ H3O+ and CH3NH3+? — Preceding unsigned comment added by 175.110.242.217 (talk) 16:48, 6 August 2011 (UTC)

The "coordinate" part of the Coordinate covalent bond name simply refers to where the electrons of the bond came from before the bond exited. Once the bond forms, there is no longer any evidence of this aspect of the bond. You can point to a bond in a drawing and say "this one's electrons came from that atom", but that is not a property of the molecule itself in real life. The electrons are not individual particles that are specifically part of a one specific bond in the molecule. DMacks (talk) 17:08, 6 August 2011 (UTC)

Indeed, electrons have no memory about where they came from. More importantly the same "bond" could be "formed" in different ways, and get the same result. Describing a bond as a "coordinate covalent" bond really just implies that the bond formed via a Lewis acid-base reaction whereby the bond is formed as a 2-electron filled orbital in one atom merges with an empty orbital in another atom to form a new filled bonding orbital and unfilled antibonding orbital. The other method of bond formation occurs when two 1-electron half-filled orbitals form the bonding/antibonding pair of molecular orbitals. Once the result is done, however, the bonds behave the same whether they formed via the former method or the latter. --Jayron32 17:50, 6 August 2011 (UTC)

How much (embedded) energy is needed to build different kind of power plants?

How much (embedded) energy is needed to build different kind of power plants? And with embedded energy, I mean the energy used by machines of different kinds: electrical sources, fossil fuels as well as renewable sources, etc. And with machines I mean the machines involved in the creation of the power plant, that is: transportation of components to the place, the production elsewhere of different components needed for the construction, and perhaps also the extraction of the raw material needed for the production of components. So, I would like to know how much energy that is needed to build, for example a nuclear plant or a wind turbine, and then I also wonder how long time it would take for the different kinds of power plants to create (transform) the same amount of energy as it took to construct the plant? I know that this is a hard thing to answer, but it would be very interesting if someone could make at least some simple calculations on it. //moralist 19:32, 6 August 2011 (UTC)

At the risk of angering many energy "activists" - there is absolutely no meaningful way to define "embedded energy" without incurring a wild goose chase of infinite recursion. It is for this reason that reliable sources, such as the United States Department of Energy and the Energy Information Administration, make essentially no reference to this parameter. You can verify this for yourself using your favorite web search utility or by perusing the websites of such organizations. I highly recommend reading their reports, incliding the EIA's short- and long-term energy outlooks, to gain perspective into this issue. This is not to say that embedded energy doesn't "exist" - of course energy is used to build new energy production facilities; it's just that quantifying that energy is more a game of politics than of science. You may find similarities between embedded energy and the energy returned on energy invested - another similar economic parameter typically applied to fossil fuel extraction. Nimur (talk) 20:48, 6 August 2011 (UTC)

Here is a good article: "How can we compare or add up our energy consumption?" This article explores the difficulties of adding different types of energy used in different scenarios, and presents the methods used by the United States for statistical purposes. Nimur (talk) 20:58, 6 August 2011 (UTC)

From reading that article it seems trivially easy. Its only "difficult" because they don't use metric. 92.28.249.101 (talk) 23:13, 6 August 2011 (UTC)

Here are some more resources for you to read: Energy Efficiency, which outlines a statistic called the "Primary Energy Conversion Factor" and is based on real data, and Interactions in the National Energy Modeling System, which expresses market and economic interactions with various primary energy conversion factors via a sophisticated computer model. Nimur (talk) 21:16, 6 August 2011 (UTC)

Well, actually, in a free market where all real costs, including those of insurance, waste disposal, and other hidden variables are rationally assigned--rather than assuming "someone" will clean it up, you can make such calculations as best is possible. The problem is incurred when free markets in immediate costs are mixed with the assumption that someone else, usually the tax payer, will deal with the costs of things like long term toxic waste disposal, birds killed by noisy windmills, dam collapse, or poorly designed and managed nuclear plants in quake zones and tsunami shadows. There is no such thing as absolute knowledge. But if you disabuse private investors of the notion that the state will clean up in the case of emergency and require rational preparation to address all costs, the free market will price in such costs for you. Sorry if that provides no specific answer in any concrete case. μηδείς (talk) 03:21, 7 August 2011 (UTC)

There is this technical resource, George Reisman's Austrian economics-treatise Capitalism, available for pdf format download at capitalism.net and for hardcover purchase at Amazon. μηδείς (talk) 03:35, 7 August 2011 (UTC)

To paraphrase what I said the last time this came up: the free market won't insure against large uncertain future expenses because it's too risky. Insurance companies want certainty like everyone else, and they do that by insuring against frequent, small (at the scale of the insurance company) losses. This limitation of the market has nothing to do with whether it's a good idea to build nuclear plants or not. It probably is a good idea, since coal and petroleum are much worse, and nothing else can supply the modern world's energy needs. When there's something that needs to be done but the free market won't do it, governments step in; that's what they're for. I know there are people who believe that the market does everything perfectly and governments should be abolished, but those people are wrong, just like the people who think that homeopathy works, etc. This is the science desk. -- BenRG (talk) 04:30, 7 August 2011 (UTC)

Well, yes, god like knowledge is impossible. Wasn't it that famous free marketeer Keynes who said that in the end we are all dead? And no, I don't advocate anarchism, nor does Reisman--a staunch minarchist--although he is far more sceptical of the need or ability to price in the effects of pollution than am I. A free market without government/taxpayer subsidization of unseen costs like pollution and disaster relief is not perfect, just the best system at pricing things rationally. μηδείς (talk) 01:06, 9 August 2011 (UTC)

MOX UK

The UK is closing a MOX plant that's only a few years old and cost over a billion to build because there has been insufficient demand for its product, particularly after the Japanese tsunami.

But why is there is talk of building another MOX plant on the same site as the closed/bulldozed one that will cost six billion?

I understand that this is a way to get rid of a large plutonium stockpile, but would it not be cheaper to design future UK nuclear reactors to use the specification of MOX fuel that the 'old' plant produced? 92.28.249.101 (talk) 23:09, 6 August 2011 (UTC)

I take it (from this article) that the closing plant is at Sellafield. As for why... I'm not informed enough on the issues to be totally sure, but it does look an awful lot like a boondoggle. It doesn't look like experts think there is really a market for a new MOX plant. As for why you wouldn't just make reactors that could take old MOX fuel, the issue is likely that the new generation of reactors have inherently different fuel requirements. Reactor fuel requirements are often quite specific if the reactor is meant to be profitable — the margins of profit are not huge. With research reactors (because profit is not a big issue) you can often re-engineer them to take different types of fuel (e.g. changing a HEU reactor to a LEU one) but that usually changes the power output quite a bit and requires extensive design changes. So it's not an easy change. As to why they didn't design it in the first place, the tautological answer is probably "because it wasn't a good idea to do so, probably for economic reasons," but that's not a very interesting explanation.

Anyway, it is a very good question, and it seems a lot of experts and citizens are rightfully asking. The official answer given ("Don't worry, there will be a market! Plus: jobs!") is not very compelling on the face of it. It's really, really unclear right now what the future of the nuclear industry is. For awhile it looked like there would be a "Renaissance" (Nuclear renaissance) in nuclear power, but after Fukushima it is a lot more problematic. --Mr.98 (talk) 00:19, 7 August 2011 (UTC)

The Guardian article linked to above says that the government's talk of building another MOX plant was just a red-herring so that the plutonium stockpile would not be recorded as a massive liability (rather than an asset) on the government balance sheet. Why cannot politicians be honest for a change - we're not in Italy. I hope the putonium can be used up for power generation rather than being a dangerous stockpile for many centuries. 92.24.133.68 (talk) 12:55, 7 August 2011 (UTC)

It seems the problem is many in government are hoping the same thing, but experts believe the truth isn't so rosy Nil Einne (talk) 19:15, 7 August 2011 (UTC)