Wikipedia:Reference desk/Archives/Science/2020 September 2

= September 2 =

Why do mice like peanut butter so much and where did the cheese thing come from?
Does it have the right percent of macronutrients to survive on as little as possible or something? Is it missing any mousie essential nutrients? Do they still need water if they only have fresh peanut butter that hasn't lost water yet? Would they eat it till they're obese if they could? Or even gorge till they puke? Or just stop when they're not hungry? Do they hide some for later like squirrels? Sagittarian Milky Way (talk) 02:36, 2 September 2020 (UTC)
 * According to this article (cited in our article on the house mouse), rodents can't actually vomit. PaleCloudedWhite (talk) 07:55, 2 September 2020 (UTC)


 * A quick Google search indicates that peanut butter is rich in nutrients that mice crave. We used to bait our mouse traps with a tiny dab of the stuff, or sometimes a tiny bit of bacon could also do the trick. ←Baseball Bugs What's up, Doc? carrots→ 09:10, 2 September 2020 (UTC)


 * As to where the mice and cheese meme originates, in The Taill of the Uponlandis Mous and the Burges Mous of 1480, the town mouse dines on delicacies unknown to the country mouse; "chies and butter" get the first mention . To be fair, they also eat candle wax, so perhaps it's the fat content - candles were made of tallow in those days "a rendered form of beef or mutton fat". Peanut butter wasn't invented until 1884, whereas both mice and cheese have been part of the human experience for millennia. Alansplodge (talk) 16:59, 2 September 2020 (UTC)
 * Dictionaire Oeconomique, Or, The Family Dictionary (1729) p. 128: "MOUSE; a little four footed Animal, so common and so universally, known as to need no Description... [they] are injurious in and about Houses, by eating Cheese, Meat, and other Provisions of the Houshold". Alansplodge (talk) 17:11, 2 September 2020 (UTC)
 * I recall reading somewhere that the association of mice and cheese comes from pre-20th century Western culture, where cheese was one of the foods that would be commonly found stored in a pantry. Remember, no refrigeration. It said mice don't have any real preference for the stuff, but they're omnivores and will eat what they can get. Flour and similar things can't be easily eaten by rodents because they can't bite them into chunks with their incisors. --47.146.63.87 (talk) 22:09, 3 September 2020 (UTC)
 * So what's the smallest crumb they'll eat? Will they eat crumbs past the point they start looking for bigger if they have no other choice? Perhaps by licking and swallowing whole? Sagittarian Milky Way (talk) 01:58, 4 September 2020 (UTC)
 * I'm not sure about that last statement:
 * "Mice can cause a surprising amount of damage in a cupboard or pantry, eating their way through flour, cookies, rice, beans, noodles and even meat contained inside pouches such as tuna or chicken. Dry soup mixes add flavor to the mouse's diet and cake mixes provide desert". What Do Mice Eat
 * "Generally speaking, mice are unlikely to get into your fridge or freezer. But if you have bags of flour or sugar or foods in cardboard boxes taking up space in your pantry, now is the time to stock up on airtight plastic or glass containers, according to Terminix" Things that attract mice
 * Not from authoritative sources, but opinions anyway. Alansplodge (talk) 11:44, 5 September 2020 (UTC)

Universe density without expansion
Could it be argued theoretically that without accelerating expansion of the Universe its density might gradually (possibly over some long period) increase (due to various matter -forming and shedding processes) to the point of becoming high enough to conduct sound waves? And is that acceleration actually essential to offset possible density increase which otherwise may overtake "slower" expansion, without acceleration? Brandmeistertalk  14:40, 2 September 2020 (UTC)
 * Matter-energy can't be formed. Expansion without any accelerating magic decelerates and will expand forever, stop on infinity AD or stop before infinity AD and go back to infinite* density. Probably tiny gray areas where outcome depends on quantum fluctuations too. Sagittarian Milky Way (talk) 14:57, 2 September 2020 (UTC)
 * I mean increase in gaseous density in particular, because various astrophysical processes generate gases, like hydrogen and oxygen. Presumably without accelerating expansion this continuous buildup of gases and molecules would affect average density of the Universe, making the space more dense. Brandmeistertalk  18:21, 2 September 2020 (UTC)
 * I'm not aware of any astrophysical processes that result in a net production of hydrogen - theoretically, Hawking radiation might occasionally produce a proton or electron around a black hole, but that would be (at least over normal cosmological time scales) be more than balanced by hydrogen falling into black holes. Oxygen is produced by stellar nucleosynthesis, but at the cost of using up much larger amounts of hydrogen. Typically, interstellar gas goes down as galaxies age (it's used up in star formation). --Stephan Schulz (talk) 19:57, 2 September 2020 (UTC)
 * Supernovae explosions, for example, are known to produce some elements (and reportedly, shock waves that compress gas clouds to aid new star formation). This raises an additional issue of possibly insufficient space for new stars and cluttering in the absence of Universe's expansion. Wow... unless there's something wrong with that assumption. Brandmeistertalk  20:42, 2 September 2020 (UTC)
 * Supernova explosions produce some elements, but not from nothing. They just rearrange existing matter into new configurations. Also, after a supernova explosion, there usually is one star less. --Stephan Schulz (talk) 20:53, 2 September 2020 (UTC)
 * But what about my question per se? Would the density increase without accelerated expansion? Brandmeistertalk  08:06, 3 September 2020 (UTC)
 * Matter & energy isn't being created or destroyed. If the size of the universe was held fixed, the overall mass density would be constant.  That said, the local mass density can change, especially as gravity causes clouds of hydrogen and helium to condense into stars.  The stars are very dense, but the surrounding area is then somewhat depleted.  Stars convert hydrogen and helium into heavier elements.  Over time the amount of hydrogen and helium will decrease and the amount of heavier atoms will increase.  The total number of atoms is likely decreasing.  Certain esoteric particles, such as neutrinos, are probably accumulating over time (however, their overall density will still be very low).  Dragons flight (talk) 10:20, 3 September 2020 (UTC)
 * Still, there is conversion of energy into mass per energy-mass equivalence. Would it contribute to the density increase in a fixed-sized Universe? A supernova explosion shoots elements and debris into space. Supernovae explode relatively rarely while new stars are formed continuously in the entire universe. Apparently, for every single supernova explosion at least several new stars emerge - which may be another issue in a fixed-size universe. Brandmeistertalk  11:40, 3 September 2020 (UTC)
 * No, there isn't. Mass-energy equivalence means that energy already has mass.  Everything else being equal, an object will weigh (very slightly) more when it hot than when it is cold because the thermal energy contributes (very slightly) to the total mass.  You can convert energy into matter, but you haven't actually changed the total mass.  Dragons flight (talk) 13:30, 3 September 2020 (UTC)
 * It might be even more accurate to say that energy is mass; neither energy nor mass is a kind of "stuff" that can possess something else, rather they are properties that are possessed by "stuff" (matter, space, etc.) The point of mass/energy equivalence is that these two properties are really the same property in different manifestations; which is to say that the property of "mass/energy" gets called "mass" in some situations (in a gravitational field, or when resisting forces) and gets called "energy" in other situations (when it is moving, or when it is motionless but under a force).  Energy cannot have mass because energy is not a stuff.  It is a property like mass is a property, moreso it is the same property.  -- Jayron 32 16:29, 9 September 2020 (UTC)
 * As a physicist I vehemently disagree with the statement that "energy is mass". Only internal energy of a system with inner degrees of freedom shows up as mass, hence a box of gas gains mass when it is heated because more energy is pumped into the inner dofs (the motion of the gas particles within the box). This is relativistic mass, which shows up as the mass defect in nuclear reactions and this is also what's important for the topic under discussion here. Hence you're free to talk about energy density or mass density in this context. However, there are forms of energy that do not show up as mass in any meaningful way. That is in particular the centre-of-mass motion of a particle or of the gas-filled box. The box does not gain mass when I wizz past it on a train compared to when I just stand next to it. Note that I deliberately put myself on the train and not the box — it does not matter by the relativity principle. The idea of "relativistic mass" is too often applied to that situation as well, but it is meaningless and useless. You cannot derive a gravitational field from that mass, you cannot derive inertial properties from that mass. In fact, the concept violates the relativity principle. So, energy and mass are two distinct quantities and concepts. What mass/energy equivalence means is that you have to take mass ("rest mass" if you must) into account when doing the energy balance in, say, particle or nuclear reactions, along with momenta. --Wrongfilter (talk) 16:59, 9 September 2020 (UTC)
 * Fair enough. But it is not more correct to say energy has mass.  I'm trying to picture what that even means.  -- Jayron 32 17:02, 9 September 2020 (UTC)
 * I'm reminded of the now discredited steady-state model which had matter created to fill the void created by expansion of the universe. Remove the expansion, keep the creation of matter and you're all set.
 * Steady state is dumb. It expanded from immense density and possibly bounces forever is simpler. Bouncing forever was later ruled by expanding forever of course. Sagittarian Milky Way (talk) 16:06, 3 September 2020 (UTC)
 * It appears dumb now, because we've latterly found evidence supporting a different model. That evidence hadn't been discovered when Steady State was first proposed by Fred Hoyle, at which Time Steady State was, if anything, a slightly simpler and seemingly more plausible model than what he derisively called "Big Bang". {The poster formerly known as 87.81.230.195} 2.122.2.158 (talk) 22:46, 3 September 2020 (UTC)