Science desk
< December 31	<< Dec \| January \| Feb >>	January 2 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is a transcluded archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

January 1

Onion ring - Bispropenyl disulfide?

Hi all,

I have a little look around and the only mentions of this purported chemical seem to be quotations from Wikipedia.

Disulfide obviously means two Sulfurs in the middle.
"Propynyl"... a three carbon alkyne with a triple bond between the carbons?
Bis is an nonstandard form of di, so two "Propynyl" as the R's in R-S-S-R.

Hmm.... would Carbon triple-bonds survive cooking temperature? And is Bispropenyl disulfide - despite all what you might see on the internet - pretty much fictional? Pete AU aka --Shirt58 (talk) 12:37, 1 January 2021 (UTC)[reply]

The compound is more commonly called Diallyl disulfide. Propene is an alkene not an alkyne. Mike Turnbull (talk) 13:09, 1 January 2021 (UTC)[reply]

The term occurs in the old-fashioned spelling "bispropenyl disulphide" in an article in New Scientist. It contains an illustration with the chemical formula. I am not too familiar with the representation of chemical formulas, but I think this is not the same as diallyl disulfide: the double bonds are at different spots:

CH₃–CH=CH—S–S–CH=CH—CH₃ (bispropenyl disulfide)

CH₂=CH–CH₂–S–S–CH₂–CH=CH₂ (diallyl disulfide)

--Lambiam 17:39, 1 January 2021 (UTC)[reply]

Nice spot, Lambiam. There are a number of similar components in onion and the one named by the OP is indeed likely to be one of the isomers you drew (the double bonds can each be independently E or Z but usually Z, I think). There is a freely-available article that covers some of these compounds here: Eady, Colin C.; Kamoi, Takahiro; Kato, Masahiro; Porter, Noel G.; Davis, Sheree; Shaw, Martin; Kamoi, Akiko; Imai, Shinsuke (2008). "Silencing Onion Lachrymatory Factor Synthase Causes a Significant Change in the Sulfur Secondary Metabolite Profile". Plant Physiology. 147 (4): 2096–2106. doi:10.1104/pp.108.123273. PMC 2492635. PMID 18583530.. Mike Turnbull (talk) 18:13, 1 January 2021 (UTC)[reply]

Looking with "Find Similar Structures" for diallyl disulfide on PubChem turns up a compound with the IUPAC name1-(prop-1-enyldisulfanyl)prop-1-ene, with as a given synonym "dipropenyl disulfide". The two appear to be sufficiently different that the former has three safety warnings, including "acutely toxic", while the other has none. As far as I can tell its chemical structure is the same as seen in the New Scientist article, which mentions this as responsible for a "sweeter smell" when frying onions, so I think this is the compound referred to as "bispropenyl disulfide" in the Onion ring article. --Lambiam 19:57, 1 January 2021 (UTC)[reply]

What are candidates for the decade with the most weather records under various emissions scenarios?

Or only the limited set of all-time single-station records that most weather stations of long recordkeeping have, just count them and sum worldwide, that's simpler than trying to estimate complicated things like what year the world hurricane speed record etc is most likely to fall.

A spherical cow model doesn't seem too hard if you used some simple "what's the highest sigma reached by year x if weather station starts 1900 and climate didn't change" model which has probably been made and statistically found the most likely year to break a record if each temperature was boosted by the y-value of a simple curve that fits the average land temperature curve in the IPCC scenario but a degree of global warming doesn't necessarily cause 1 degree of boost to the highest temperatures in a place and correlation with precip, cold records etc would be bad. And those would have more effect than heat records by (collectively) outnumbering them. Sagittarian Milky Way (talk) 15:08, 1 January 2021 (UTC)[reply]

How to understand pitch in sound subject?

I can understand "volume", but I can't understand "pitch" term. How to understand pitch in sound subject?Rizosome (talk) 15:22, 1 January 2021 (UTC)[reply]

We have an article at Pitch (music) - does that help? Matt Deres (talk) 16:35, 1 January 2021 (UTC)[reply]

See also This YouTube video for an basic explanation. Alansplodge (talk) 16:46, 1 January 2021 (UTC)[reply]

Small children speak at a higher pitch than adults. Adult women generally speak at a higher pitch than adult men. On a standard musical keyboard such as a piano the keys go left to right from a low pitch by small steps to a high pitch; the sounds produced differ only in pitch. --Lambiam 17:02, 1 January 2021 (UTC)[reply]

Wiki articles are too technical for readers so I prefer reference desk to learn. Low Pitch means first key in piano? Rizosome (talk) 18:31, 1 January 2021 (UTC)[reply]

The lowest pitch on a piano is the key farthest to the left; the highest pitch is the key farthest to the right. The pitch increases from left to right. --R. S. Shaw (talk) 20:15, 1 January 2021 (UTC)[reply]

If you find the Wikipedia articles too technical, try the Simple English Wikipedia.--Shantavira|^{feed me} 20:35, 1 January 2021 (UTC)[reply]

(edit conflict) Low and high are relative attributes, just like tall and short. A man with a height of 240 centimetres is tall, but no one would call a tower of that height tall. The leftmost key of a standard piano (corresponding to the key with key number 1 in this table) is close to the lowest pitch humans can hear as a tone, but many pipe organs have a pedal keyboard that goes even lower. The pitches of whale songs can also be lower. But sounds that have a much and much lower pitch than the highest key of a piano may still be referred to as having a high pitch, and sounds that have a much higher pitch than the lowest key may be referred to as having a low pitch, because they are high or low in comparison to something else. No human singer, not even Diana Damrau, can get as high as the highest key on a piano, and not even Yuri Wichniakov can get as low as the lowest key, and still here we read: "A Basque woman recently performed this remarkable shout for me. She started with a loud, high tone and gradually descended to a low pitch."

By the way, there is also a Wikipedia written in a simpler English; see for example their article about Pitch. --Lambiam 20:49, 1 January 2021 (UTC)[reply]

So "low pitch" sounds like "low decibel" sound? Rizosome (talk) 23:48, 1 January 2021 (UTC)[reply]

No. Decibel, as a measure of sound pressure level, relates to loudness or volume. Pitch relates to that character of a musical note which is independent of its duration. While our article -- pitch (music) -- describes the mechanism, the perception or qualia is difficult to put in writing, other then by referring to sounds you may have heard -- such as the low pitch of a key on the left side of a piano (YouTube: Hear Piano Note - Lowest A 0m20s) vs. the high pitch of a key on the right (YouTube: Hear Piano Note - Highest C 0m7s) (Here are notes in ascending pitch: YouTube: Hear White Piano Keys - All 52 Notes 2m45s.), or the low pitch of a foghorn (YouTube: Sounding the Sumburgh Foghorn 2m22s -- first sounds at 1m45s) vs. the high pitch of a penny whistle (YouTube: Traditional Irish Tin Whistle Songs 2m51s).

If you are deaf or sufficiently hearing impaired to not discern these difference, let us know and we might be able to give an analogy, otherwise here are some additional videos on the subject:

YouTube: Sound Waves: High Pitch and Low Pitch 2m32s -- demonstrates with voice, guitar string, xylophone, and resonate bottle.
YouTube: Pitch – Higher and Lower 3m14s -- a quiz comparing pairs of piano notes. (A non-interactive demo video of an interactive program.)

You may find dog whistle interesting; its pitch is above that which most humans can hear. -- ToE 00:48, 2 January 2021 (UTC)[reply]

You could watch the "Do Re Mi" segment from The Sound of Music. Each note has a different pitch. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:43, 2 January 2021 (UTC)[reply]

One way to think of pitch is like color. Both are psychological perceptions of physical phenomena (qualia). Just as color is a way we perceive different wavelengths of light, pitch is how we perceive different wavelengths of sound. Humans perceive sound waves in two ways: slower waves are perceived as rhythm and faster waves are perceived as pitch, but there's no fundamental difference between the two physically. Adam Neely has a great video on this, demonstrating the transition between rhythm and pitch. I'll see if I can dig it up. --Jayron 32 14:06, 4 January 2021 (UTC)[reply]
This video here. I've timestamped it to start at the point where he discusses the relationship between rhythm and pitch and the transition between them, but the entire lecture is a great discussion on the psychology of sound, and the analogies to light and vision are in there as well. It is a great introduction to the topic, and if you have time to watch the whole lecture, I highly recommend it. --Jayron 32 14:27, 4 January 2021 (UTC)[reply]

Why nuclear fusion instead of breeder reactors

Dear Wikipedians:

Why are so much attention and effort being directed towards nuclear fusion when breeder reactors are already shown to work? I read a piece by Bernard Cohen which calculates that just the amount of uranium-238 alone (not counting thorium) is enough to power the world for as long as the sun is in a state to support life on earth.

172.97.139.62 (talk) 23:57, 1 January 2021 (UTC)[reply]

For something as big as what will end Earth's clean energy shortage it's good to not put all eggs in one basket. Sagittarian Milky Way (talk) 00:06, 2 January 2021 (UTC)[reply]

Agree with your perspective 172.97.139.62 (talk) 14:59, 2 January 2021 (UTC)[reply]

Safely disposing of radioactive waste is an unsolved issue. Breeder reactors produce less than other types of fission reactors, but if applied on a grand scale, the waste will become a growing and eventually unmanageable problem. --Lambiam 01:58, 2 January 2021 (UTC)[reply]

Agree with your perspective 172.97.139.62 (talk) 14:59, 2 January 2021 (UTC)[reply]

It's certainly an issue that needs to be dealt with, but I don't think it's clear at all that it's "unmanageable" or even "unsolved".

There are lots of solutions. They carry varying levels of near-term and long-term risk. The problem is that people have expectations for bounds on the risk that they don't apply to things other than nuclear power. Some would require, for example, assuming that civilization might fall and our descendants might lose knowledge about the repositories. That indeed could happen, but in my view, in that case the repositories will simply become one of many things in the natural world that can hurt them because they don't know about them.

That said, there are indeed some significant challenges in dealing with the waste, particularly given that we have to consider that it might be spread by deliberate human activity (war or terrorism). --Trovatore (talk) 19:18, 6 January 2021 (UTC)[reply]

Thanks for your perspective. 172.97.139.62 (talk) 12:41, 7 January 2021 (UTC)[reply]

The amount of available fuel is not currently a limiting quantity - there is little practical difference to a contemporary society between using uranium to run FBRs for a billion years or the same uranium to run LWRs for 10 million years. Moving beyond the issue of fuel, the breeder reactors really only have one thing going for them - the waste consists of isotopes with much shorter halflives than that of conventional nuclear reactors. But that is where the major advantages end. Breeder reactors currently require a greater capital investment than conventional reactors of similar output; they are more prone to accidents, which is a rather huge deal when it comes to nuclear; and it's theoretically possible to use a breeder reactor to generate fuel for nuclear weapons. It seems likely that the increased cost and accident risk may be a sort of self-reinforcing issue - i.e. that the existence of these issues may contribute to more conventional reactor designs receiving more attention and research moneys, causing the difference in cost and safety to persist regardless. Anyway, fusion power comes without concern for the kind of radiation leaks of either of these types of fission reactor, without the concern of massive quantities of radioactive waste, and without the concern of waste being turned into fission bombs. Someguy1221 (talk) 11:29, 2 January 2021 (UTC)[reply]

"same uranium to run LWRs for 10 million years" -- by this phrase do you mean current LWRs running on uranium-235? But I do agree with your other points. 172.97.139.62 (talk) 14:58, 2 January 2021 (UTC)[reply]

I was honestly thinking in terms of the initial mass of raw uranium before being processed for one type of reactor or the other, but you could work it in different ways. U-238 turned into P-239 can be burned in a LWR as well in the form of mixed oxide fuel, although this raises the temperature of the reactor and may diminish some of the safety benefits. It does not come close to covering the gap in fuel efficiency. Someguy1221 (talk) 08:44, 3 January 2021 (UTC)[reply]

I see I see. 172.97.139.62 (talk) 18:54, 6 January 2021 (UTC)[reply]

Breeder reactors can be used to produce fissionables leading to nuclear proliferation, as alluded above. And fission reactors in general (except for some inefficient designs not used so far in powerplants) present a risk of meltdown accidents etc. One can debate whether that risk is overhyped, but it exists. Everyone knows what Chernobyl is. With fusion, the hard technical problem is to keep the reaction going at all, not to prevent it from going out of control. 2602:24A:DE47:BB20:50DE:F402:42A6:A17D (talk) 08:28, 8 January 2021 (UTC)[reply]