Wikipedia:Reference desk/Archives/Science/2019 August 18

= August 18 =

Heating the sun with water
If the sun were to begin to transition to a red giant could we prolong it by adding water / hydrogen/ mass into it ? Or would the radiation of the sun desipate/repel anything we threw at it before it got to the sun, Like a solar flare or something like that? — Preceding unsigned comment added by 76.203.37.29 (talk) 06:59, 18 August 2019 (UTC)


 * This will not happen for perhaps five billion years, by which time it is unlikely that anyone will be around to spray water onto the surface. As you suggest, anything we spray onto the surface will be blown off and have negligible effect on the core, where even photons take many thousands of years to escape, and the time to change the thermal equilibrium is millions of years.  Where would we get vast amounts of water?  If we have the technology to transport it at that time, then we will have long inhabited other parts of the galaxy and Earth will no longer be of significance.  Apologies for the opinion expressed here.  The "solid" information came from our article on the Sun.   Dbfirs  07:50, 18 August 2019 (UTC)
 * Adding mass makes a star's life shorter, not longer. The more mass, the more gravitational force trying to collapse the star, and thus the more pressure on the core, which accelerates the rate of fusion. --47.146.63.87 (talk) 09:52, 18 August 2019 (UTC)
 * ...the end comes quicker and, if enough mass were added, would be much more dramatic. SpinningSpark 11:05, 18 August 2019 (UTC)
 * relevant articles: Stellar evolution, Main sequence, etc. As pointed above, you would need to add hydrogen to the core, not just the star. Maybe you could reach the core with a high enough velocity projectile, but what need to be done would rather be to remove helium. have fun with that Gem fr (talk) 13:39, 18 August 2019 (UTC)


 * Removing helium is no problem. Just hit the star straight on with a Jupiter-sized slug, accelerated to near the speed of light. :-) SinisterLefty (talk) 14:42, 18 August 2019 (UTC)
 * My though exactly. hence the fun. Gem fr (talk) 23:34, 18 August 2019 (UTC)
 * Your average slug moves at a snail's pace. ←Baseball Bugs What's up, Doc? carrots→ 23:46, 18 August 2019 (UTC)
 * That would presumably cause a supernova and fuse all the helium, which I guess counts as "removing" since it's not helium anymore. It's also now a huge cloud expanding through space plus maybe a black hole, rather than a star. Anyone up to calculating that to check? Would you get a black hole, or would the star be totally disrupted like in a pair-instability supernova? Since it's a collision, not a stellar implosion, I suppose you'd need fluid dynamics calculations to get a precise answer… --47.146.63.87 (talk) 00:30, 19 August 2019 (UTC)


 * If you waited until "the last minute" to shoot the slug, when it was mostly helium, the supernova scenario would be more likely than if you did it early on. SinisterLefty (talk) 12:16, 19 August 2019 (UTC)


 * Representative lifetimes of stars as a function of their masses.svg No matter where you add mass, it won't make the star last longer. (Not sure if this is what you meant by you would need to add hydrogen to the core, but in any case I'll elaborate for readers.) I think a lot of people are led astray by intuitively thinking of a star as an engine you can just add more fuel to, making the engine run longer. But stars "burn" their "fuel" more quickly if you add more. It doesn't matter where in the star you stick the mass, because it will always cause the star's gravitational pressure to rise and therefore increase the rate of fusion. (See chart for reference.) Actually, adding mass to a red giant, I believe, shortens the star's lifetime even more than for a star on the main sequence, because you might increase the core pressure enough to trigger the helium flash, or helium burning in higher-mass red dwarfs, which accelerates the star's transition to a planetary nebula. In contrast, a main sequence star will just continue to fuse hydrogen more rapidly in its core. In general, if you want to prolong a star's lifetime, you remove mass rather than add it. Of course, this means the star produces less light and has weaker gravity, which has implications for any planetary system. The only sort-of exception is in "re-igniting" stellar remnants like white dwarfs and neutron stars, which are no longer fusing. In these cases, if you add mass, you can restart fusion and generate more energy. But, it has to be done gradually so as not to trigger a supernova. --47.146.63.87 (talk) 00:30, 19 August 2019 (UTC)
 * The plan would be to remove helium (mass) and replace the hydrogen consumed, to sort of reboot the star. Doing it continuously would be the best. Some practical issues, of course, but funny to imagine.Gem fr (talk) 11:51, 19 August 2019 (UTC)


 * I'm curious where the OP intends to get enough mass of anything to make any difference at all. The sun contains 99.8% of all mass in the solar system already, so even if we threw the entirety of every planet and moon and asteroid and cloud of interplanetary gas and the best we could hope to do is change the mass by some insignificant amount.  -- Jayron <b style="color:#090">32</b> 12:11, 19 August 2019 (UTC)

Pouring water onto the sun has been discussed on xkcd What If previously. Double sharp (talk) 14:23, 19 August 2019 (UTC)


 * The OP's premise is in the same league with Will Rogers' proposal to solve the German U-Boat problem by boiling the oceans. ←Baseball Bugs What's up, Doc? carrots→ 17:15, 19 August 2019 (UTC)
 * lol. Pretty sure Will Rogers was joking and OP was not. Gem fr (talk) 08:31, 20 August 2019 (UTC)
 * Yes. His followup, when asked just how to do that, was something like "That's up to the experts to figure out!" But unless the OP returns here, we may never know if he was joking or not. ←Baseball Bugs What's up, Doc? carrots→ 11:35, 20 August 2019 (UTC)

Apple varieties and nutrition
When I buy apples from the supermarket there are a few varieties available. By taste, and description, it feels like some are much sweeter than the others. Gala, for example, compared to Braeburn. Are these meaningfully more sweet nutritionally, and if not how do they taste so different? I've done some Google searches but I just get articles with vitamin differences in mg. My question essentially boils down to "Are the differences big enough to matter?" For example, would it be sensible to treat different types of apples as different foods on a diet plan, or are all apples essentially the same? 51.9.138.192 (talk) 12:13, 18 August 2019 (UTC)


 * Organic apples are thought to be healthier due to containing a more diverse bacterial community Count Iblis (talk) 12:22, 18 August 2019 (UTC)
 * please, encyclopedia here. Advertorials are not a relevant information source. You should just delete such baseless health allegation, which BTW are banned for a reason: Organic_food No health agency ever found health benefits of eating organic (but everyone "knows" they sold their souls to evil non-organic food corps...) Gem fr (talk) 14:05, 18 August 2019 (UTC)
 * That article cites a published scientific study:
 * for the level and diversity claims, though one could debate the reliability of a Frontiers Media journal, and notes that the other claims are based on an interview with one of that study's authors. The journal article also cites other studies noting microbiome differences. DMacks (talk) 14:32, 18 August 2019 (UTC)
 * for the level and diversity claims, though one could debate the reliability of a Frontiers Media journal, and notes that the other claims are based on an interview with one of that study's authors. The journal article also cites other studies noting microbiome differences. DMacks (talk) 14:32, 18 August 2019 (UTC)


 * Yes, different varieties will have slightly different nutritional values. However, how ripe the apples are and what type of soil and fertilizer they get, and the temps and amount of water and sunshine they get, will all affect the final nutritional values. So, rather than take this all into account, they just list nutritional averages. However, if it tastes sweeter, it probably does have more sugar, although the acidity also plays a (negative) role in sweetness. Also, most of the nutrition is in the peel, so if you peel them, the numbers will be quite diferent. SinisterLefty (talk) 14:23, 18 August 2019 (UTC)

Cox apple availability ?
As everyone knows, although apples are a seasonal crop, they are available all year round. However, Coxes have recently disappeared from supermarket shelves and a worker I asked didn't know when they will be back. Does anyone know when Coxes will be back in season? 92.31.141.118 (talk) 13:56, 18 August 2019 (UTC)


 * I made this into a sub-question for you. SinisterLefty (talk) 14:24, 18 August 2019 (UTC)


 * No idea about your local supply issue, but for those wondering about the apple itself, see Cox's Orange Pippin. DMacks (talk) 14:35, 18 August 2019 (UTC)


 * That article says they are susceptible to disease, which could affect supply either directly or because growers choose a hardier variety. SinisterLefty (talk) 14:37, 18 August 2019 (UTC)
 * Assuming that we're in the UK, English Apples & Pears - The British Season says that Cox's are in season from "Mid-September to early April". We used to be able to get Cox apples from New Zealand during the British summer, but the advent of hardier (but not quite as good) equivalents such as Gala and Braeburn seems to have put an end to that. If you like a traditional English apple, look out for Worcester Pearmains which can appear at the very end of August, weather depending. 50 years ago, Cox's totally dominated the British apple market, but seem to be a niche product now. Alansplodge (talk) 15:19, 18 August 2019 (UTC)
 * I think this is purely down to consumer demand. According to this article Cox's anly account for 21% of sales as consumers prefer the newer varieties which have been selected for sweetness - as well as shape, colour, and resistance to disease - rather than the older varieties like the Cox with their more subtle, complex flavours. Richerman  (talk) 18:11, 19 August 2019 (UTC)


 * Resistance to disease isn't something consumers care about, unless you try to sell them diseased apples. But it is something farmers care about if it lowers production levels of sellable apples. SinisterLefty (talk) 18:18, 19 August 2019 (UTC)


 * I wasn't suggesting they did, only that it is one of the main selection criteria for new varieties. Richerman  (talk) 19:15, 19 August 2019 (UTC)


 * One of the fruit stalls in a local market was owned by Irene Hunt.  She started in 1944 and was the mother of one of the metric martyrs (Reference desk/Archives/Miscellaneous/2017 August 22).   She owned the shop behind her stall, and one day while it was being renovated I found their diary for 1943 discarded outside (which I still have).   When Irene fell ill she was placed in Cox ward at the local hospital, so when we went to visit we had no difficulty remembering where she was.   In the same market I picked up two large bound folio journals which would have been collected by the dustcart if I hadn't noticed them. They turned out to be the handwritten journal for a New England estate for several months in the early nineteenth century with details of staff, purchases, payments, etc.   I left them on top of an empty stall and a few hours later they had gone.   Are such books valuable and, if so, could they have been sold at auction and what would have been the likely sale price? 2A00:23C5:3186:E600:3D9B:C5C7:2662:1431 (talk) 16:17, 20 August 2019 (UTC)


 * Might be of interest to a museum or historical society, but it doesn't sound like something that would generate much interest for private collectors. SinisterLefty (talk) 11:42, 21 August 2019 (UTC)