Wikipedia:Reference desk/Archives/Science/2019 July 27

= July 27 =

Soap
When I wash my hands with liquid soap I have to rinse them for ages and never get much of that water hardness feel. But if I wash them with ordinary soap immediately after washing with normal liquid soap, I can rinse them very quickly. Does this mean that liquid soap is very hard to wash off with water, or does normal soap somehow create a stronger effect of water hardness? 93.136.43.110 (talk) 08:05, 27 July 2019 (UTC)
 * What's the distinction between "normal" soap and "ordinary" soap? ←Baseball Bugs What's up, Doc? carrots→ 11:19, 27 July 2019 (UTC)
 * Fixed. 93.142.92.144 (talk) 21:20, 27 July 2019 (UTC)


 * "Liquid soap" is commonly a detergent, not a soap - depending on what products you've bought. It's likely to be labelled as "hadwash", rather than "soap". Andy Dingley (talk) 11:58, 27 July 2019 (UTC)


 * Here are the relevant links: soap, detergent. Note that the detergent link says detergents are "similar to soap but are more soluble in hard water, because the polar sulfonate (of detergents) is less likely than the polar carboxylate (of soap) to bind to calcium and other ions found in hard water". That seems opposite to the two theories you suggested. However, that means the hard water running over your hands is mixed with detergent, and thus no longer feels hard, while that hard water running over soapy hands does not mix well, so still "feels hard". Therefore, I suggest that you are mistaken in thinking you have all the soap off your hands, based on the feel, and if you smell them they will likely still smell like soap, or if you eat finger food right after, it may taste like soap. SinisterLefty (talk) 12:51, 27 July 2019 (UTC)


 * That means detergent isn't getting washed off until I wash again with solid soap? Does solid soap help removing the detergent? I can literally never get the same hardness feel after minutes of rinsing after detergent, compared to seconds of rinsing after using solid soap, so I guess I always have a good bit of detergent left on my hands anyway if I don't rinse with solid soap (and they certainly smell like it). I would think that solid soap helps with removal tho, since water does get hard after using both in sequence. FWIW the water is pretty hard here, around 10-25°dh. 93.142.92.144 (talk) 21:20, 27 July 2019 (UTC)


 * A little detergent on your hands likely won't hurt you. Heck, some detergents are even used as food additives: Sodium_triphosphate.


 * You might want to get a water softener, but avoid drinking the water, if it's the type that dissolves salt pellets in the water. It can be used bathing, dish washing, laundry, flushing, tooth brushing, hand washing, and, provided you reduce the salt you add, for cooking. Use bottled water for drinking. SinisterLefty (talk) 21:40, 27 July 2019 (UTC)


 * Interesting read. If anything, I was sure it's harder to wash hands in soft water, as you never know when to stop. As for drinking, soft water tastes nasty, no thanks. Not gonna pass up free Evian on tap :-) 93.136.43.218 (talk) 22:09, 27 July 2019 (UTC)


 * You're right that over-softened water can be a problem. I found shampooing to be the worst, where I must rely on the change in friction in my hair to tell me when the shampoo is all washed out, but overly-softened water makes the hair remain slippery no matter how long I rinse it. For hand-washing, there are other clues, like when the suds are gone. Hard to see those on the back of your head. SinisterLefty (talk) 22:22, 27 July 2019 (UTC)

Heat cycle in animals
When an animal, say a cat or a dog, enters the estrus heat cycle, does it know that it will result in pregnancy and kittens or puppies. Or is it just doing what it's body demands, and satisfying an instinct it has no control over? --Andrew 08:44, 27 July 2019 (UTC)


 * IIRC Paul Theroux wrote once of visiting a tribe that didn't meaningfully connect sex and childbirth. If that's true that'd say something about the likelihood of animals figuring it out. 93.136.43.110 (talk) 08:47, 27 July 2019 (UTC)


 * An article on the realisation of the connection in humans. I recall an article at least a decade ago on older female chimpanzees who began to avoid sex, where the article author suggested they had realised sex led to pregnancy and they did not want that, but I don't remember where I read that, and I suspect it was highly speculative.- gadfium 09:12, 27 July 2019 (UTC)


 * Yes, the more likely explanation is that it's simply instinct, since getting pregnant at that point is unlikely to result in an adult chimp, due to the age of the mother and her inability to protect the baby into adulthood. Thus, the cost in terms of extra food is a net negative to both the mother and the group. Such instincts evolve over time, with those individuals and groups which randomly have such an instinct being more likely to survive to pass it down. Incidentally, the "heat cycle" is called estrus. SinisterLefty (talk) 12:49, 27 July 2019 (UTC)


 * It's fascinating to me that there is an instinct in many animals not only to mate, but also to prepare for the delivery of offspring. Think about how many animals find or even prepare a future home for the little ones. They sure act like they know what's going on, but of course, who knows. Though I would say I feel like cats and dogs do sometimes have a "surprised" look when they see something unexpected or unusual, but cats and dogs who give birth seem ready for it. Of course, again, something something instincts. Someguy1221 (talk) 01:24, 28 July 2019 (UTC)


 * Nesting instinct is our article about that. DMacks (talk) 16:36, 28 July 2019 (UTC)


 * Administering pregnancy hormones, such as progesterone, in the proper amounts ought to make it clear that nesting is based on those, and not something they've thought through. SinisterLefty (talk) 12:11, 29 July 2019 (UTC)


 * "They had realised sex led to pregnancy and they did not want that" How on Earth did these researchers know what a female chimp want? Did she explain in sign language? Sounds very unlikely to me they had a good argument for knowing, or even guessing this. --Lgriot (talk) 13:30, 31 July 2019 (UTC)


 * The correlation between sex and childbirth in humans has been touched on here multiple times, usually linked via the classic example of the Trobriand Islands. Stuff here may be germane. Their concept of baloma is a lot like transubstantiation in that believers do not examine it critically because there is no desire to go down that path of thinking. Matt Deres (talk) 15:21, 31 July 2019 (UTC)

Dream meaning
What does it mean if you had a dream of a loved one dying and then a couple of weeks later they did die of the same reason that you have dreamed of? -- Randomuseronelol — Preceding unsigned comment added by Randomuseronelol (talk • contribs) 18:38, 27 July 2019 (UTC)
 * No one here is qualified to interpret your dreams. If you're concerned, see your doctor. ←Baseball Bugs What's up, Doc? carrots→ 19:07, 27 July 2019 (UTC)
 * Anyone is qualified to interpret a dream or prophecy online. It's easier than selling herbal potions. It means death comes for us all and ghosts only remember what we never forget. InedibleHulk (talk) 20:16, 27 July 2019 (UTC)


 * But yeah, don't expect such service at the Science Desk, normally. Ask Twitter. They'll know. InedibleHulk (talk) 20:22, 27 July 2019 (UTC)


 * The likelihood of the dream being right would greatly depend on the details. If somebody with severe heart disease who already survived 3 heart attacks finally dies of the 4th one, that's not exactly a surprise. But if the person died of being hit by a meteor that would be truly remarkable. Of course, there would need to be actual proof that the dream occurred as described. And if you dreamed they would be shot, right before you shot them, that's makes you more psycho than psychic. SinisterLefty (talk) 20:34, 27 July 2019 (UTC)
 * This. It is hard to even imagine a loved one death, quite often while just everybody else knows he is dying, you keep telling "ye, he is not great, sure, but it happened before and he recovered", but somewhere you already knows it is the end, and it can show in dreams Gem fr (talk) 23:02, 27 July 2019 (UTC)


 * Sympathy. We can offer Death anxiety (psychology), Precognition, Dream interpretation and associated links Gem fr (talk) 23:02, 27 July 2019 (UTC)