Wikipedia:Reference desk/Archives/Science/2016 May 20

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May 20

Diamond in a rock tumbler

What if you put a big diamond in a rock tumbler? Anna Frodesiak (talk) 00:55, 20 May 2016 (UTC)

Define "big". ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:43, 20 May 2016 (UTC)

Like the size of a grape, but maybe the size wouldn't matter. Anna Frodesiak (talk) 01:46, 20 May 2016 (UTC)

The size might well matter, as more surface area could take longer to polish. The illustration doesn't have a scale, but some of the types of rocks suggest grape size or larger. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:51, 20 May 2016 (UTC)

But would it polish or just stay the same forever? Anna Frodesiak (talk) 01:59, 20 May 2016 (UTC)

If you're using standard polishing materials, it wouldn't polish as the prices relies on being able to scratch and smooth the surface. More likely the diamond would shatter or crack as they are brittle and easily chip along cleavages planes. You buffed with other diamonds, you could cut and polish it. EvergreenFir (talk) Please {{re}} 03:09, 20 May 2016 (UTC)

Rhenium diboride can be made harder than diamond, so you could polish diamonds with that. However, a polished diamond would just look like a glass marble. It's the facets that make them sparkle, and you get those by cleaving diamonds, not polishing them. StuRat (talk) 03:27, 20 May 2016 (UTC)

Very interesting. Thank you so much you two. Anna Frodesiak (talk) 05:37, 20 May 2016 (UTC)

It is a misunderstanding of hardness to assume that because diamond is harder than the other minerals involved, it will not be abraded at all. Diamond tipped drill bits do wear out, and have to be replaced - just not as often as other drill bits. When two minerals of differing hardness rub together, both are abraded - but the softer one is abraded much more quickly than the harder one. 86.141.19.154 (talk) 12:14, 20 May 2016 (UTC)

As an engineer who has done a lot of work with matterials rubbng and weraing, I can tell you that it is a well-known effect that the intuitive "the softer surface is abraded much more quickly than the harder surface" only hold true when both surfaces are harder than silicon dioxide (a major component of dust and dirt). If you have, say, teflon rubbing against stainless steel, the metal wears out. That's because little bits of dust get embedded in the soft plastic and act like a file to wear down the metal. --Guy Macon (talk) 15:59, 20 May 2016 (UTC)

• Hi User:Anna Frodesiak, interesting question as usual! If you'd like some scientific reference for rock tumbling: Here [1] is a whole study that gives empirical results on how size and shape of particles influence roundness, abrasion, and size reduction in the end product. Then they develop a theoretical model based on that that uses exponential functions to predict/relate how the various factors influence the tumbling process. A very nice little paper, IMO. While you could tumble larger diamonds in diamond dust, you could also tumble raisin-sized diamonds together and they would performs abrading action on themselves. Industrial diamonds are also sometimes prepared using a tumbling mill, see here [2] for a study involving that and a new way to impregnate diamonds in cutting tools. SemanticMantis (talk) 13:35, 20 May 2016 (UTC)

And thank you again. :) Very informative. Anna Frodesiak (talk) 00:46, 22 May 2016 (UTC)

• It would depend a lot on the quality of your diamond. Diamonds are hard, but they're also somewhat brittle, depending on their crystal structure. A monocrystalline diamond (i.e. "flawless", but also pretty much any natural diamond) is strong. Factory-made diamonds from published technologies are mostly polycrystalline: this makes them prone to splitting between the separate crystals. Diamonds aren't strong because they have magic chemistry, it's because they have simple chemistry with high valence and this allows a densely packed, well-interconnected lattice. Anything (like the discontinuity at the surface of a crystal) that disrupts this lattice loses the quality which makes diamonds what they are.

When buying diamond abrasives, a big cost and quality difference is whether they're mono- or poly- crystalline. For abrasive powders (small grains), it's practical to make monocrystalline diamond powders, but it's cheaper to have shorter-lasting polycrystalline. Smaller crystals are quicker to grow, for one thing. A "lab-grown jewellery diamond" isn't yet practical by any published process, as it would have to be both large and monocrystalline (as is already cheap and widespread for sapphires). Many conspiracy theories exist for De Beers et al. having such a process and keeping it secret.

So "big monocrystalline diamond in a rock tumbler" is something of a thought experiment. "Big polycrystalline diamond" in there is more likely, but also (and some synthetic abrasives are quite hard themselves) it's not going to last as long as you might think. Andy Dingley (talk) 12:14, 22 May 2016 (UTC)

Dinosaur skeletons

Are most dinosaur skeletons found in pieces and not assembled together? 50.68.118.24 (talk) 04:02, 20 May 2016 (UTC)

Yes, in fact only a few bones may be found. A fully intact and articulated dinosaur skeleton is a rare find. But, since scientists can put them together in the proper order, and make fake bone to fill in for any missing pieces, it's not a problem. StuRat (talk) 04:11, 20 May 2016 (UTC)

Of course it's been a problem. See here, for example. Or for a less academic source, here. --69.159.60.83 (talk) 06:38, 20 May 2016 (UTC)

Leave it to Stu to reduce an entire scientific discipline (shaped over centuries, with many famous debates over validity of reconstructions) to "not a problem." :) SemanticMantis (talk) 13:47, 20 May 2016 (UTC)

Here [3] is a link to piece from the Smithsonian that describes how scientists attempt to correctly reconstruct dinosaur skeletons from partial finds, and here [4] is another discussion of the topic from Ohio University. Sometimes nearly a whole animal is fossilized, this is called a Lagerstätte. SemanticMantis (talk) 13:56, 20 May 2016 (UTC)

• How do you find a skeleton in the first place? Many bones are found in the bends of ancient rivers etc., where they were washed by the current. This tends to disrupt a skeleton even before they're fossilised. A skeleton is also commonly found when it starts to be exposed by the surrounding rock splitting or weathering out. So the finder may only half of it to work with. Andy Dingley (talk) 12:16, 22 May 2016 (UTC)

Equal distribution

(moved to math desk here [5] SemanticMantis (talk) 17:50, 20 May 2016 (UTC))

Capacitor information sought

I have found amongst my components what I think are polystyrene capacitors hermetically sealed in metal cans. The wires come out via glass to metal seals. The only printing on the cans is 'KS'at the top, then the value in pF (confirmed with a capacitance meter) and the voltage then a long number and finally at the bottom what appears to be a date code like 8/88 or 1/89. I have searched the web to find who might have made these units without avail. Can anyone tell me where to search to find details on these units?--178.106.99.31 (talk) 16:58, 20 May 2016 (UTC)

KS stands for Polystyrene Film/Foil capacitor. It doesn't seem to have anything to do with the manufacturer. --Jayron32 17:38, 20 May 2016 (UTC)

May I ask why the OP wants to know. If he is a radio-ham or old wireless repairer and thinks he may be able to use them, then all that is required is pF and the voltage rating. Being polystyrene they are not electrolytic nor tantalum or anything else but ones exhibiting polystyrene caricaturistics. I think 8/88 is more likely the batch code. These low value pF capacitors in metal cans with glass to metal seals became obsolete many years before 1988. Cut one open, is it really polystyrene or waxed/varnished paper? A photo may help to identify the manufacture and locate the data sheets. But it would help to know why.--Aspro (talk) 21:03, 20 May 2016 (UTC)

I dont have a specific application in mind. Just thought if they were stable capacitors I may be able to use them as references or something. But Im curious as to why these should be sealed in cans. Is it something to do with preventing moisture ingress?--178.106.99.31 (talk) 16:14, 21 May 2016 (UTC)

Staphylea colchica flowers

(I'm posting this here rather than at Talk:Staphylea colchica because I suspect that will not get seen). The article currently says "orange flowers"; but the illustration (like the example I saw this week at Nostell Priory) has white flowers. I notice that the external reference (for which I have just found and added an archived link) also shows white flowers, and has the text "Orange blossom fragrant flowers". This is a strange way of saying "orange flowers", and my hypothesis is that it means "flowers with the fragrance of orange blossom". Anybody got any thoughts (or knowledge!) on this? --ColinFine (talk) 21:18, 20 May 2016 (UTC)

I think you're right. I think the flowers smell either like orange flowers or maybe have a citrus scent. Dave's garden [6] says "white or near white" while the eminently reliable Missouri Botanical Garden says "greenish white" [7] and also describes the flower as fragrant. I felt WP:BOLD and removed the confusing "orange" bit from the article, as I cannot even find evidence of an orange-blooming variant. SemanticMantis (talk) 21:27, 20 May 2016 (UTC)

Are both soft and hard brake checks dangerous?

Could safety be improved by a soft brake check? After all, this could get a tailgating car off your tail. --Llaanngg (talk) 23:28, 20 May 2016 (UTC)

Maybe? It might also start a positive feedback loop of braking that suddenly slows traffic (traffic congestion#Causes) or causes a 13-car crash. The butterfly effect-like mechanics is very complicated. Sagittarian Milky Way (talk) 00:16, 21 May 2016 (UTC)

This article seems relevant to your question. --Jayron32 00:17, 21 May 2016 (UTC)

As a safer alternative to actually touching your brake pedal (which might slow you enough to cause the tailgater to hit you), you might consider just switching your rear fog lights on and off. This might momentarily cause the tailgater to think you're braking, and if the tailgating is not deliberate, this might alert them to the fact that they're too close.

However, if it is deliberate, you might just provoke them, and someone who is deliberately tailgating is not the clearest thinker to start with. The advice in Jayron's link is good.

For interest, I personally know of instances of the tailgater being a local police car apparently hoping to provoke the victim (a local publican) into exceeding the speed limit or "driving in an unsafe manner" (which brake-testing would be), presumably so that they could stop and charge or at least inconvenience him. {The poster formerly known as 87.81.230.195} 185.74.232.130 (talk) 14:37, 23 May 2016 (UTC)