Wikipedia:Reference desk/Archives/Science/2020 August 28

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August 28

Large and small moons

I was fascinated to find out through our Main page today, that the asteroid 243 Ida has its own tiny moon.

What are the largest and smallest moons currently known to science? --Dweller (talk) Become old fashioned! 08:34, 28 August 2020 (UTC)

In our solar system, the largest known moon is Ganymede, and the smallest currently listed as a moon is S/2009 S 1. You could make an argument every grain of dust orbiting a planet is a moon though. Some potentially larger moons may be found outside our solar system. Fgf10 (talk) 08:47, 28 August 2020 (UTC)

I believe Titan is larger if astronaut eyeball opaque air layers count, Ganymede if only solids and liquids count. Sagittarian Milky Way (talk) 13:39, 28 August 2020 (UTC)

• (edit conflict) Natural satellite#Definition of a moon may get in the way of a definitive answer (as hinted in the answer above by the "grain of dust" argument). Tigraan^{Click here to contact me} 08:51, 28 August 2020 (UTC)

If you want the largest moon relative to its primary, the smaller component of 90 Antiope is a candidate. —Tamfang (talk) 01:04, 29 August 2020 (UTC)

Interesting stuff, thanks. My non-scientific perception is that science is so precise with its definitions of everything, so it's quite fun to find there's no precision here. --Dweller (talk) Become old fashioned! 09:24, 28 August 2020 (UTC)

Wow. Did you ever misunderstand "science". --Jayron32 09:37, 28 August 2020 (UTC)

Lol. I've persistently misunderstood it. Just ask any of my science teachers from my school days. --Dweller (talk) Become old fashioned! 11:30, 28 August 2020 (UTC)

It's part of the problem with our education system. There's two things that get meant by "science", and in schools we're really only taught one. The first is a list of "facts" (scare quotes intentional) that we're taught to memorize about things like biology and chemistry and geology and stuff. "Dmitri Mendeleev invented the periodic table" "The mitochondria is the powerhouse of the cell". Shit like that. An endless series of trivia questions for which we can repeat the answers of; as a small point we do sorta need to know these things, because understanding how the world works is of course the goal of science. But this is BY FAR the less important aspect of science. The more important aspect of science is the PROCESS of science, which is extremely messy and not at all packaged like the way we learn it in school, as a list of already-proven facts that are written in stone and will be true forever. Don't get me wrong, it's okay to operate on that level for some things. A ball dropped near the surface of the earth will accelerate at 9.8 m/s/s. But when we get to the more fundamental stuff where we ask "why" something is happening (instead of just describing what is happening) you really need to ask before hand "what level of approximation are you willing to tolerate". The answer to "why" becomes vastly different and ever changing. Scientists operate on that level all the time. And that doesn't even get into the issue of linguistics and classifications, which really are just arbitrary things we create to give order to our world and are not fundamental to anything in the universe, like "What is a planet" and "What is a moon" and stuff like that; those are just descriptions we made up out of whole cloth, and as such, are subject to whatever whim we want when setting the parameters. --Jayron32 11:58, 28 August 2020 (UTC)

I am rather reminded of Lord Ernest Rutherford's quip that "All science is either physics or stamp collecting". The school system does have a certain focus on the stamp collecting. (Not to say that there isn't real science outside of physics, though.) --184.146.89.141 (talk) 18:22, 28 August 2020 (UTC)

Watch Richard Feynman discuss the question "why" something is happening.  --Lambiam 19:16, 28 August 2020 (UTC)

Well, and of course there are two, non-overlapping, definitions of the word "Why?". One could be asking "what is the antecedant cause of X?", as in "Why did the ball roll down the hill?" Or one could be asking "for what purpose did "X" happen?" For example "Why did you kick the ball down the hill?" Science is really only concerned with the first set of whys. The why of the second kind presuposes an intelligence to have purpose, and laws of nature do not presupose such things. --Jayron32 13:00, 1 September 2020 (UTC)

Just look at the Plutonic fights and ongoing controversies over the definition of "planet". Any measurement-derived classification boundary in the natural sciences is bound (sorry) to have a certain degree of arbitrariness.  --Lambiam 10:03, 28 August 2020 (UTC)

The working definition of "moon" is a non-star that orbits another non-star and is more or less the junior partner in the relationship, meaning the primary body's gravitation is the dominant factor. The universe doesn't care what names we give to things, so like just about any human classification there's a grey area. At some point the bodies' masses approach equality and they both have a strong gravitational effect on the other, as with Pluto and Charon, and then you might want to call them a double planetary system instead. But every moon tugs back on its primary because that's how gravity works; here on Earth the Moon tugs on us and causes tides. And anything can theoretically have a moon if something stays inside its Hill sphere, though at some point it gets kind of silly to bother classifying it as a moon, in particular because it's not likely to stay there for a long time (in astronomical terms). At tiny enough scales, it will be easily perturbed by other astronomical bodies, radiation, and/or the galactic tide. --47.146.63.87 (talk) 09:33, 30 August 2020 (UTC)

Would a frozen sauce pouch defrost faster in room-temperature water or room-temperature air?

I have a watertight plastic pouch of sauce. The sauce is still liquid despite spending months in my freezer.

Imagine I had two of these pouches, both identical, and I submerged one in room-temperature water and the other I left on the countertop in room-temperature air. Which of those two pouches would reach room-temperature faster? --Aabicus (talk) 21:01, 28 August 2020 (UTC)

Water. See: Thermal conduction 107.15.157.44 (talk) 21:09, 28 August 2020 (UTC)

It will certainly start warming faster in the water, but if you're talking about a small volume of water in a pan, say, then the water is getting cooler as the pouch warms up, so it will tend to reach a thermal equilibrium temperature cooler than the water originally was. You therefore need to start with water that is warmer than room temperature. The air in the room is circulating and being replaced by normal ventilation, so while it will help to use warm air, the pouch will eventually come close to room temperature anyway. --184.146.89.141 (talk) 21:34, 28 August 2020 (UTC)

As heat flows from the water to the pouch and thereby lowers the temperature of the water, heat will also start flowing from the air to the pot and its watery content. Therefore there is no theoretical need to start at a higher temperature for the water than room temperature; in the limit all will have the same temperature. However, also theoretically, the shared limit of thermal equilibrium between all connected systems (air, pot, water, pouch) is never reached but only approached. For submersion in water, the initial incline may be much steeper, but the pouch temperature curve may begin to flatten out sooner, only to be overtaken by the curve for the air case; this could happen, for instance, if the thermal conductivity of the pot is extremely low.  --Lambiam 11:41, 29 August 2020 (UTC)

All this answers the detailed question, which does not match the title's question, answered already by 107.15.157.44 (under the somewhat safe assumption that "room temperature" is significantly above 0°C). Tigraan^{Click here to contact me} 16:05, 31 August 2020 (UTC)

Theory aside, practical experience shows that frozen food thaws faster in a sink (or pot, etc.) full of water. Perhaps thermal dissipation from water to air is also a factor. 107.15.157.44 (talk) 21:51, 28 August 2020 (UTC)

You might find our article on Sous vide interesting. It talks about heating the contents of plastic pouches in water. Zindor (talk) 21:53, 28 August 2020 (UTC)