Science desk
< December 19	<< Nov \| December \| Jan >>	December 21 >

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.

December 20[edit]

Clementine[edit]

Did Clementine (nuclear reactor) produce any gold from its (her?) mercury coolant? 2601:646:8E01:7E0B:F865:F22A:92D:104D (talk) 02:56, 20 December 2016 (UTC)[reply]

Don't know about Clementine, as the mercury was merely a coolant, not something specifically subjected to the sort of radioactive process designed to transform it into gold. Google turns up nothing in this regard. But as a general concept of transforming mercury into gold, you may be onto something here. Of course, as a practical matter, it doesn't seem a commercially feasible way to manufacture gold. To quote:

Repeat five zillion times, until you have enough gold to make an ingot. Success! However, if you didn’t do so earlier, you must now separate the stable gold deriving from Hg-196 from the unwanted crud deriving from the rest of the mercury, which I remind you constitutes 99.85 percent of what’s out there and a good chunk of which I’ll bet is now radioactive. So it could be a long afternoon.

So you get that whilst this is an interesting experiment, practically, it wouldn't work beyond producing trace amounts. What we can't do, as far as I'm aware, is truly mimic nature's way of producing gold - a Supernova. This is a massive cosmic phenomenon. But the day may yet arrive where we can send robots to mine space. Underwater mining of gold is another area which may become commercially feasible at some point as robotics become cheaper and more advanced. In part, though, this will depend on the gold price. Eliyohub (talk) 11:55, 20 December 2016 (UTC)[reply]

Given that nature's main way of producing gold is the r-process, we actually do have the means of mimicking the high neutron fluxes you would need in a supernova: it is after all how we synthesised einsteinium and fermium. However, the method necessary (exploding hydrogen bombs) is perhaps not a very cost-effective way to produce gold, though it is certainly an impressive-looking one, and you don't make anywhere near enough to justify the costs.

It so happens that we have an article about producing precious metals in a nuclear reactor: synthesis of precious metals. It has been seriously considered, although the yield from Hg would produce more Tl than the minuscule amount of Au, and Pt would work better (though then we're not making as much money). Double sharp (talk) 12:02, 20 December 2016 (UTC)[reply]

Wow, you learn something new every day. So our equivalent to a supernova would be to explode a Hydrogen Bomb? Er, I don't think we'll be manufacturing Hydrogen bombs for that purpose, thank you! BUT, as arms-control deals between the major Nuclear powers lead to agreements on mutual reductions in stockpiles (what happened to those taken out of active deployment under the Strategic Offensive Reductions Treaty, for example?), we will be left with some surplus Hydrogen warheads no longer needed by militaries. Blasting them into gold does look like an interesting proposal... some sort of new experiment in Peaceful nuclear explosion technology? Currently, such explosions are limited by treaty to a yield of 150 kilotons, and I do think a Hydrogen blast would breach this limit. But treaties can be amended to allow for this - my question is, how do we do this safely, without destroying the world in the process? If we already have the Hydrogen bombs as military surplus, would this be commercially viable?

Also, if this is the idea, why did previous peaceful nuclear explosion experiments not look at this? Eliyohub (talk) 12:16, 20 December 2016 (UTC)[reply]

The answer to your second-to-last question is "no" -- not only would the gold yield be miniscule, but the gold would also be dangerously radioactive and therefore unusable (except perhaps as a means to covertly dispose of a foreign spy). And that, in turn, is the reason why nobody seriously looked at this. 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 03:20, 21 December 2016 (UTC)[reply]

There is so much I don't know about nuclear transmutation, and I wonder how much of it is known to anyone. These articles talk about hitting isotope X with something. It doesn't say what the nuclear spin state of the target is or anything about orienting it with a magnetic field. It doesn't say whether "monochromatic" neutrons all with a single speed will have different results based on the speed, or whether some kind of absorption or other effect (along the line of induced gamma emission) could occur with the right background photons. I've never heard of anyone trying to do muon-catalyzed transmutation either, though looking up the phrase I found one hit for a Star Trek forum and one for this "exciting proposal" at Fermilab [1]. I feel like 99.9% of the nuclear applications possible haven't even been poked at yet. Wnt (talk) 16:40, 20 December 2016 (UTC)[reply]

Circumcision as HIV prevention in gay men (particularly insertive anal sex)[edit]

Excuse the graphic nature of this question, but it's fair science. And I don't consider it nearly as graphic as Brokie22222's question above, and it's a much more realistically practical question. There has been quite a bit of research looking at circumcision's chances of reducing the risk of a man catching HIV from having sex with a woman. Such female-to-male transmission is common in sub-Saharan Africa, but rare in the western world.

In the western world, by far the biggest source of HIV transmission is "men who have sex with men". And from my understanding, the riskiest sexual act in this regard is anal sex. (Oral sex poses a much lower risk). So my question is purely regarding anal sex, not other male-male sex acts.

Now, for the receptive partner, or, in gay slang, the "bottom", being circumcised would logically make no difference whatsoever to the chance of catching HIV.

My question is regarding those men who have sex with men who purely play the role of the insertive partner - in gay slang terms, the "top". Has there been any research looking at these men, and once adjusting for other factors (e.g. condom use and number of partners), whether there is any correlation between being circumcised or not, and the chance of catching HIV? And further, whether it would be medically prudent to recommend to such men (insertive anal sex performers with other men), that they consider getting circumcised?

(I've never personally engaged in anal sex in my life and don't intend to. BUT, if anyone claims this falls into a "medical advice" question - does it, I don't know - you can stick to posting links to published research on this question). Eliyohub (talk) 11:34, 20 December 2016 (UTC)[reply]

Are you able to check references 13 and 14 in Circumcision? CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 14:22, 20 December 2016 (UTC)[reply]

Or you could paste the first and third words of the title of your question into Google Scholar. Seek and ye shall find. Alansplodge (talk) 16:21, 20 December 2016 (UTC)[reply]

Strange solid brown stuff inside banana[edit]

Recently I opened a banana which looked fine from the outside but inside was in a state I'd never seen before. I took a picture before discarding it. What's going on with this banana? The brown stuff wasn't bruising. None of the other bananas in the bunch were affected. http://imgur.com/LKRmXlX.png --88.105.113.43 (talk) 18:04, 20 December 2016 (UTC)[reply]

Unbruised bananas can also spoil, apparently. I've seen that before. Some type of spoilage, presumably. I discard that portion and eat the rest. StuRat (talk) 18:06, 20 December 2016 (UTC)[reply]

There are a variety of plant diseases that can cause the inside of bananas to take on a red discolouration. Nigrospora is a fungal disease that causes the centre of the banana to turn dark red. Mokillo, moko, and blood disease bacterium are bacterial diseases that can also cause red discoloration in bananas. While unappealing to eat, these diseases affecting bananas are not a threat to human health, however when in doubt, throw it out or compost them. - Canadian Food Inspection Agency (((The Quixotic Potato))) (talk) 18:13, 20 December 2016 (UTC)[reply]

BTW, some idiots have claimed that those bananas are injected with HIV infected blood, but that is a hoax/urban legend/bullshit. (((The Quixotic Potato))) (talk) 18:48, 20 December 2016 (UTC)[reply]

It is cute that you can see the brown stuff marking the divisions between the three carpels inside the banana. Honestly, it was only on seeing that just now in your picture that it first occurred to me that bananas are monocots... I'd never thought about it. :) As to what that means... well, I have no idea. But it sort of hints at a fruit-wide sort of organization to whatever this color is. Wnt (talk) 19:35, 20 December 2016 (UTC)[reply]

There is a very long list of the many diseases that bananas can get here - List of banana and plantain diseases. Your one looks rather like "Blood disease" - but I can't guarantee the diagnosis. Wymspen (talk) 19:51, 20 December 2016 (UTC)[reply]

[Banned user's contribution deleted]

It is not true that "all previous varieties have suffered this fate". See the banana article. What happened was Panama disease made the Gros Michel variety uneconomical to cultivate, so the global banana industry switched to the Cavendish variety. Gros Michel is not extinct; it's just not widely grown anymore. Other banana varieties exist as well, and researchers are trying to create ones more resistant to disease. --47.138.163.230 (talk) 21:24, 20 December 2016 (UTC)[reply]

Agreed. Out list of banana cultivars article says: "The total number of cultivars of bananas and plantains has been estimated to be anything from around 300 to more than 1000." So, if Cavendish went extinct, we would switch to others. StuRat (talk) 21:47, 20 December 2016 (UTC)[reply]

Then there's always plantains, if you have some strange compulsion to fry your fruit. StuRat (talk) 21:42, 20 December 2016 (UTC)[reply]