Science desk
< April 30	<< Apr \| May \| Jun >>	May 2 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

May 1[edit]

Why don't low-carbohydrate diets cure diabetes?[edit]

Low-carbohydrate diets have drawn a lot of criticism over the years. I know that large amounts of protein, for instance, might be hard on a diabetic's kidneys, and a high intake of saturated fat can raise cholesterol and LDL levels, further increasing the risk of heart disease in the high-risk diabetic population. I wouldn't recommend such a diet, but there's something that I don't understand: Why doesn't a low-carbohydrate diet eliminate the body's need for insulin-meditated glucose uptake? I know that the body would need to convert some of the protein in such a diet to glucose in order to supply the brain with energy (only a portion of its needs can be met by ketones), but the muscles and fat cells - which require insulin for glucose uptake - don't have to run on glucose. Why is that glucose levels don't drop dramatically on a low-carbohydrate diet? How much glucose can the body produce from the protein in a low-carbohydrate diet? I've read that the body tries to maintain homeostasis, so even after days of total starvation - a state in which the body runs on its own fat and protein reserves - glucose levels don't drop that much below normal. Does that have something to do with it?

I found a study in which subjects ate just 21 grams of carbohydrate per day. Their HbA1c improved, but it was still elevated at 6.8%.174.131.63.119 (talk) 01:05, 1 May 2016 (UTC)[reply]

Which diabetes? Diabetes mellitus type 1 is characterized by a non-functioning pancreas, specifically the loss of function of the beta cells. It has no connection to dietary intake, in the sense that it is neither caused by, nor particularly fixed by, changes to one's diet. Diabetes mellitus type 2 is a different beast entirely, it isn't about problems on the insulin production end, it's a problem with insulin resistance. As noted in Wikipedia's article, type 2 diabetes can be managed by dietary controls in ways that type 1 diabetes cannot. --Jayron 32 01:16, 1 May 2016 (UTC)[reply]

Type 2 diabetes ("diabesity") can be helped by a low carb diet, but note that diabetics also need to prevent low blood sugar levels, so low glycemic index foods, which don't cause the sugar spike and then collapse, are a better choice than just eliminating carbs. StuRat (talk) 05:07, 1 May 2016 (UTC)[reply]

One reason, I believe, is that the liver produces glucose through gluconeogenesis even if you don't consume any carbohydrates. And, diabetics usually have elevated levels of gluconeogenesis. One of the most widely-used drugs for treating type 2 diabetes, metformin, works in part by inhibiting gluconeogenesis. --71.110.8.102 (talk) 09:38, 1 May 2016 (UTC)[reply]

Its not carbs specifically that raise blood glucose, its the glycemic load of the carbs and other foods that do that. So if you decrease your glycemic load in meals, you are likeky to reduce your blood glucose values after eating.--178.103.251.111 (talk) 15:30, 1 May 2016 (UTC)[reply]

A small study has shown that a general low calorie diet can put type 2 diabetes into remission, although the long term prognosis isn't known yet.[1] Richerman (talk) 16:55, 1 May 2016 (UTC)[reply]

That study indicates its the loss of weight/fat due to restriced calories, not a low calorie diet as such. So one might expect same results by other weight/fat loss methods.--178.103.251.111 (talk) 18:06, 1 May 2016 (UTC)[reply]

However, other studies have shown that those who have had bariatric surgery show an immediate improvement in management of diabetes, corresponding to the reduction of calories, before any significant weight is lost. StuRat (talk) 04:16, 2 May 2016 (UTC)[reply]

Erm.... Bariatric surgery IS weight loss surgery Stu!! So after the surgery, you have lost weight.--178.103.251.111 (talk) 16:47, 2 May 2016 (UTC)[reply]

You must be thinking of liposuction, where they physically remove fat. I am talking about procedures where they limit the capacity of the stomach, by inserting a balloon, putting a band around it to limit expansion, or bypass most of it surgically. Those don't cause weight loss during the surgery, only after. StuRat (talk) 00:29, 3 May 2016 (UTC)[reply]

Yes you are right. My mistake. Didnt read article properly.--178.103.251.111 (talk) 17:07, 3 May 2016 (UTC)[reply]

Before insulin was discovered, diabetes type 1 patients were treated with a low-carbohydrate diet. It didn't cure the patients but it extended their lives with a year or so. Severe starvation diets were also tried with no better results [2]. Sjö (talk) 04:52, 2 May 2016 (UTC)[reply]

Energy Conservation in Sulfur Oxidizers[edit]

I was curious if any of you knew anything about the sulfur-oxidizing bacteria. I have several sources saying that if the bacteria use the enzyme sulfur dioxygenase to oxidize elemental sulfur to sulfite, they conserve no energy from the reaction. It is clear that energy is conserved from the oxidation of sulfite to sulfate, which is catalyzed by sulfite oxidase, but scientists don't know if energy is conserved from the first reaction. I came across a book that said there was evidence that even aerobic sulfur bacteria conserve energy from the oxidation of elemental sulfur to sulfite, and that they use an enzyme other than sulfur dioxygenase. I was wondering what that enzyme might be. I didn't know if anyone here could tell me anything about this.174.131.63.119 (talk) 01:27, 1 May 2016 (UTC)[reply]

~~Did you read the obvious article Sulfate-reducing bacteria and perhaps Sulfur-reducing bacteria (both linked from Sulfur bacteria) and associated refs? Nil Einne (talk) 17:39, 1 May 2016 (UTC)~~[reply]

Sorry for the useless answer. I was a bit tired at the time and didn't read the question properly. Nil Einne (talk) 12:50, 2 May 2016 (UTC)[reply]

The review [3] (2014) should be more helpful. It says "Extensive research has been done with chemolithotrophs that use sulfur oxidation for energy or with some phototrophic bacteria that extract electrons from reduced sulfur for photosynthesis ... SDO activities were first identified for chemolithotrophs, but the enzymes have not been purified, and the genes are unknown. SDOs are known as GSH-dependent sulfur dioxygenases because GSH spontaneously reacts with sulfur to produce GSSH, which is oxidized by the enzymes to sulfite and GSH." The enzymes are present in other organisms, like humans, for purposes of detoxification, and they know more about those enzymes; but I gather they're not really optimized for energy production. Wnt (talk) 18:09, 1 May 2016 (UTC)[reply]

Great article! Thank you!174.131.42.176 (talk) 00:50, 2 May 2016 (UTC)[reply]

Cancer bringing partners back together[edit]

20 years ago, the wife of my cousin left him. They had been married quite a while and their children had grown up. 8 years ago he developed cancer. His wife returned and cared for him while he was ill, took him on daily trips to hospital for chemotherapy, x-rays, etc. He is now cancer free 7 years+ and they are still living together. I have a friend with a not dissimilar experience. I suspect it may be not at all uncommon for major negative experiences to restore a marriage or relationship, and for others, help destroy it.

Have any studies been done on the effect of cancer on marriage stability, positive or negative? Where would I find them? 60.228.85.120 (talk) 02:01, 1 May 2016 (UTC)[reply]

You might try a support organization for those with cancer, their families, and friends. StuRat (talk) 05:11, 1 May 2016 (UTC)[reply]

This question is better placed on the Humanities page methinks.--178.103.251.111 (talk) 15:50, 1 May 2016 (UTC)[reply]

Yes, lots of studies. I'd add "psychology" or "psychological" to your search terms - the medical literature tends to focus on the reverse question (how the spousal situation affects the cancer) so you need to find the psychological literature. Try this search as a starting point. 184.147.128.57 (talk) 19:38, 1 May 2016 (UTC)[reply]

Question regarding Physics[edit]

Why do every moving body (most of the time- round objects) in air or vaccum rotate about its axis in a fixed speed? For example: If we throw a ball in air then we will see that the ball is moving with some rotations. In the space also same thing happens. But how and why? sahil shrestha (talk) 02:27, 1 May 2016 (UTC)[reply]

@Sahil shrestha: Please remember to post your questions at the bottom of the page. What you describe will only occur if the object is given some initial non-zero angular momentum. As long as no net torque is applied after the object is thrown, that angular momentum is conserved and the object keeps spinning.--Jasper Deng (talk) 06:21, 1 May 2016 (UTC)[reply]

@Jasper Deng: Huh! Bottom of the page? But I just ask and post the question by clicking on 'Ready? Ask a new question' button. I really don't know how to post it on the top or bottom of the page. When I ask a question it appears on the top in the beginning and after sometime when I look up for answer it appears in the bottom of the pagr automatically.Can you help me to do so then? sahil shrestha (talk) 08:20, 1 May 2016 (UTC)[reply]

@Sahil shrestha: Make sure that you are filling out the resulting form exactly as it says (you should not have to type == at any point). I am also not sure whether it works on mobile.-Jasper Deng (talk) 08:28, 1 May 2016 (UTC)[reply]

@Sahil shrestha:I confirm that your posting works and you even used indent and signing correctly. There is a simple answer to your question here in Simple Wikipedia. A ball rotates, as you said, at a fixed speed in a vacuum. But in air a ball's rotation slows down very slightly because of friction with the air, and a rotating ice skater has a way to change her speed of rotation (explained in the article). AllBestFaith (talk) 10:55, 1 May 2016 (UTC)[reply]

Tangential syntax test: simple:Angular momentum —Tamfang (talk) 09:39, 4 May 2016 (UTC)[reply]

I just tried putting == in both the subject and text of a test posting, and the software handled it admirably. [4] It must be something else. Wnt (talk) 11:29, 1 May 2016 (UTC)[reply]

The problem is something Jasper Deng suggested. Sahil shrestha is using the mobile website to edit. (You can see this from their contrib tags Special:Contributions/Sahil shrestha.) The "ask a question" button which uses the mw:Extension:InputBox function doesn't work on the mobile site. You can check it for yourself here [5]. The section=new Query string doesn't seem to be intepreted by the mobile editor. There is a way to add a new section to a talk page with the mobile editor, but I'm not sure how to carry this over to a non talk page. Some other pages use a forced link to the non mobile site which gets around this problem. (I'm not sure if it's the reason.) Nil Einne (talk) 16:02, 2 May 2016 (UTC)[reply]

@Sahil shrestha: If you really used the "Ask a new question" button, you might have found a bug in the Wikipedia software. Wikipedia gets frequent updates, and I've gotten a related bug myself when I tried to edit a new section at Meta:Wikipedia_to_the_Moon/Discussion. (I thought the bug was only on Meta, and because of their crazy translation templates) Hitting the "new question" button opens a URL like this: https://en.wikipedia.org/w/index.php?action=edit&preload=&editintro=&preloadtitle=&section=new&title=Wikipedia%3AReference+desk%2FScience&create=Ready%3F+Ask+a+new+question%21 Wikipedia generates that URL on its own, and it interprets "section=new" on its own. You couldn't even chop off the end of the URL by accident, because the page to be edited comes after the "section=new". Next time you ask a question, please check to make sure that's the URL you see you are editing. We'll continue debugging from there. Wnt (talk) 11:24, 1 May 2016 (UTC)[reply]

When you toss a ball, unless you exert a force on it right in line with it's center of gravity, it will introduce a torque which causes the ball to rotate. While air resistance will eventually stop it from rotating in air, it will likely take far longer than the ball will be in the air. In space, with no air resistance, it could keep rotating for billions of years. By contrast, a ball floating in water won't rotate for long, due to the much higher resistance to movement exerted by water. StuRat (talk) 15:03, 1 May 2016 (UTC)[reply]

@Sahil shrestha: Conservation of angular momentum is a consequence of inertia, which is a consequence of relativity. If you have two unconnected masses in empty space that are moving relative to one another, they each keep moving at the same rate. But if you tie them together so they cannot move apart, then each pulls on the other with centripetal force. The rule by which centripetal force works is that they change their motion to go around and around in circles, but keep the same speed (assuming a constant length cord). That is, incidentally, the only way to conserve energy. A spinning top is like those two connected masses in space, only there are more particles all around the top, each trying to fly out in a straight line but being pulled constantly in toward the center. Wnt (talk) 00:30, 2 May 2016 (UTC)[reply]

It is indeed possible to toss a ball that does not rotate. See knuckleball. → Michael J Ⓣ Ⓒ Ⓜ 15:47, 2 May 2016 (UTC)[reply]

Sufficiently symmetric objects (such as spheres or cubes) rotate at a constant rate because of conservation of energy: if they rotated faster/slower, the total kinetic energy of the moving parts would be higher/lower.

Less symmetric rigid objects don't rotate at a fixed rate or around a fixed axis in general, even in a frictionless vacuum. Here's an example (a spinning book on what I assume is the ISS). As the rotational axis changes, the rotational speed also changes, again because of conservation of energy: when rotating parts are nearer to/farther from the axis of rotation, they have less/more kinetic energy at a given rotational speed, so the rotation has to speed up/slow down to conserve energy.

The angular momentum vector of a free-spinning object in vacuum never changes, but the axis of rotation isn't always parallel to the angular momentum. -- BenRG (talk) 00:39, 3 May 2016 (UTC)[reply]

WDM[edit]

Is it true that WDM can hide inside planets and keep them warm?--178.103.251.111 (talk) 18:12, 1 May 2016 (UTC)[reply]

Warm dark matter or warm dense matter? Tevildo (talk) 18:53, 1 May 2016 (UTC)[reply]

Dark--178.103.251.111 (talk) 19:54, 1 May 2016 (UTC)[reply]

No, due to lack of interaction with normal matter, and their high energy, WDM particles would not be confined to a planet. If there was enough of it, perhaps it could warm a planet, but would also warm a star even more in this situation. You may also wish to read http://arxiv.org/abs/0808.2823 and http://arxiv.org/abs/0903.4879 with Stephen L. Adler as the author promoting these ideas. Graeme Bartlett (talk) 22:23, 1 May 2016 (UTC)[reply]

OK. So it could permeate a planet?--178.103.251.111 (talk) 22:41, 1 May 2016 (UTC)[reply]

The dark matter making up the Milky Way is moving at less than 270 km/sec. But to hang around the Earth it would have to be under the escape velocity of Earth. Anyway dark matter if it is in small enough pieces would easily permeate a planet. If however it is in bigger pieces, eg 1 gram, up to millions of tons, it may actually interact quite strongly with planets, say if it was hydrogen snowflakes, or meteors. Even if it were pieces of neutron star material or mini black holes it could punch its way through Earth, but deposit energy and cause damage. Graeme Bartlett (talk) 03:29, 2 May 2016 (UTC)[reply]

So what is the likleyhood of WDM permeating OUR solar system?--178.103.251.111 (talk) 23:01, 2 May 2016 (UTC)[reply]

If WDM exists, and is the cause of the mass of dark matter, then it will be in the solar system, but since we do not know if dark matter is WDM or not then we cannot say if it is in the Solar System or not. Personally I think that the chance is 0% because I do not think it exists, but opinions count for nothing here. You should just be asking "Does warm dark matter exist?". The answer to that is that no one knows, and that assigning probabilities is almost impossible. Graeme Bartlett (talk) 08:36, 3 May 2016 (UTC)[reply]

To take a different tack on the question, our current theories appear to explain Earth's heat without involving dark matter. So either there's some overlooked flaw in those theories, or dark matter makes no noticeable contribution to Earth's heat, which means it likely doesn't for other planets either. As other respondents touched on, the most popular hypotheses about dark matter predict that it interacts with "ordinary matter"—what planets and stars are made of—extremely weakly, which means it would do nothing to affect planets' internal heat. Since this is in fact what we observe, we're probably on the right track. --71.110.8.102 (talk) 21:16, 3 May 2016 (UTC)[reply]

How large of an animal could exist?[edit]

How large could they get at Earth gravity? How close could we get to sandworms (Dune)? Sagittarian Milky Way (talk) 20:39, 1 May 2016 (UTC)[reply]

You may want to specify land animals, there is a considerable difference as to how large an animal could be if it supporting its own weight on land vs. being supported in the water. See Square-cube law#Biomechanics for some of the limiting factors.Naraht (talk) 20:43, 1 May 2016 (UTC)[reply]

Some land dinosaurs were pretty damn big. Almost as heavy as blue whales. And if a blue whale grew bigger maybe the pressure differential with depth would bother it. If the whale grew longer it might not have enough mouth area to volume to eat. If it grew wider it would be harder to streamline I would think. And if it ate above the bottom of the food chain instead of things like plankton or seaweed it might have difficulty finding enough food (the sperm whale, pliosaur and tyrannosaur-type dinosaurs being smaller than their plant-eating brethren). So I'm not sure it's obvious there's a big difference between land and sea. Sagittarian Milky Way (talk) 23:21, 1 May 2016 (UTC)[reply]

Almost as heavy? According to dinosaur size, the largest titanosaurs were roughly 70 to 90 tonnes, which is a very impressive ~10-12 elephants. By contrast, blue whales run more 170 tonnes, which is roughly double the largest known dinosaur. Dragons flight (talk) 11:32, 2 May 2016 (UTC)[reply]

Biology is the science of the possible, but physics is the science of the impossible. You can look at any large living or extinct organism and propose that evolution could design something better. It simply becomes unlikely as large organisms need large food sources, in addition to good engineering, but that is simply a question of what probability you accept. But it is hard to picture a true Dune sandworm based simply on the energy needed to push apart the sand vs. any plausible energy source in the sand. If someone can design an artificial sandworm, we can postulate a real one - though of course even then, postulating a stout is not the same as tasting it. I doubt they can, though... at least, not without relaxing the definition of sand to include a certain amount of fissionable material. (The sand could also be a conventional fuel, but then, why isn't it on fire already?)

If you want a more sciency prediction of maximum mass, you can go to the article that fortunately was cited in insular dwarfism here [6] (freely available), which gives a graph of herbivore or carnivore size relative to island area. I note however that it looks like you could extrapolate it to roughly 100,000 kg for a land herbivore by that logic, whereas Brontosaurus (isn't it lovely to use that term again without being tsk-tsked!) is only around 15,000 kg according to that article. Of course, the continents break up the existing land mass, so that wouldn't be valid ... question is, if all the continents were together, could you get 100,000 kg? Maybe, though it didn't happen last time that we know of. Our blue whales are 173,000 tons, and I suppose that is roughly where the line should come out for the ocean, which is all one mass, if you guesstimate it on that graph. (Funny part is, according to this logic, blue whales are larger because the oceans are bigger, not because the water supports their skeleton! I wonder if I can confirm that...) Anyway, this logic might be put to the test on Super-Earths, where engineering requirements are much more demanding, but the land mass is truly colossal. Wnt (talk) 00:15, 2 May 2016 (UTC)[reply]

Argentinosaurus approaches 100 tons and lived in South America. The parts of land bodies that cannot be in the range for a species should be considered, too. For continents with multiple biomes this could be considerable. Sagittarian Milky Way (talk) 08:49, 2 May 2016 (UTC)[reply]

OMG. I knew the titanosaurs were a trifle bigger, but I didn't realize it was such a difference. But I guess that's what taking the cube of the length will do. I should have looked up Dinosaur size. Wnt (talk) 13:14, 2 May 2016 (UTC)[reply]

Dune-style sandworms couldn't exist for reasons other than size. You can't "swim" through sand like water. There's way too much friction between sand grains. --71.110.8.102 (talk) 02:33, 2 May 2016 (UTC)[reply]

Awww, but they are so awesome :( So you mean that what earthworms do in soil doesn't scale? Sagittarian Milky Way (talk) 03:06, 2 May 2016 (UTC)[reply]

Maybe it's an alien type of sand. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:18, 2 May 2016 (UTC)[reply]

The friction between sand grains can be greatly reduced by sonic lubrication. However, sand isn't very compressible, so they couldn't really tunnel through it like an earthworm does. Perhaps they could "swim" through it on the surface, though, somewhat like a sidewinder does. StuRat (talk) 04:04, 2 May 2016 (UTC)[reply]

Hey User:71.110.8.102: got a ref for that? Because I think you're wrong. I think think that if we allow smaller sized critters, they can swim through sand. I think that because here is some video of snakes and lizards swimming through sand [7]! It is produced by real research biologists and NYT. They used X-ray photography to see what is going on under the surface. Very cool stuff. Anyway, this we should post references at the reference desk, it is not a "post something I think is true" desk. You made a claim with no support, and OP believed you, and it turned out you gave false info. For that, I think you deserve a mild trouting. I also thought User:Sagittarian Milky Way, User:Baseball Bugs and User:StuRat might appreciate the update :) (P.S. I had read about this research when it came out, but I had to find it again. That NYT link was literally my top google hit for /move through sand/)SemanticMantis (talk) 15:18, 2 May 2016 (UTC)[reply]

To be fair, the OP was talking about Dune style sandworms, i.e. unprecedentedly large creatures that were supposed to be filter feeders deep underground. (How they filter feed from sand is an even bigger objection, I suppose) The NYT video is cool, but it shows animals that would come out and hunt, and it doesn't show them going very deep. They were still able to freely displace the sand upward along their path. I don't know what the scaling law is for pushing something up one body diameter though - if you suppose Dune sandworms were only as deep, relatively speaking, as the animals in the video, could they do it with an equal expenditure of energy relative to their size, or would the requirement scale up proportional to their diameter? Wnt (talk) 23:00, 2 May 2016 (UTC)[reply]

Since the largest plants are considerably larger than the largest animals, I would postulate that larger animals may be possible, but that they would then need to emulate plants. That is, they would need to move very little. We already have small animals that emulate plants, like corals and sea anemones. Is there some reason something like a single sea anemone, but with multiple mouths and digestion centers, couldn't grow and spread to cover many square kilometers of sea floor ? (The fact that it hasn't happened yet makes me think there are disadvantages versus many small ones.) StuRat (talk) 04:08, 2 May 2016 (UTC)[reply]