Wikipedia:Reference desk/Archives/Science/2010 July 4

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July 4

Forward-swept wings

How stealthy are forward-swept wings? And would a forward-wing fighter make a good carrier aircraft? And how efficient are they at high speeds? --The High Fin Sperm Whale 00:39, 4 July 2010 (UTC)

(1) Not very, they tend to focus radar waves when viewed from head-on. (2) Forward-swept wings alleviate the boundary layer separation problems associated with swept-back wings, which allows a higher critical angle of attack and thus a lower landing speed. (3) About as efficient as swept-back wings, the reduction in wave drag is a function only of the absolute value of sweep angle without regard as to which way the wing is swept. FWiW 67.170.215.166 (talk) 01:35, 4 July 2010 (UTC)

Stealth: I would have thought that stealth wise it would be much the same as a back sweep, but not as good as 'current' steath aircraft (thinking of the B2 here) where blending the wing/body reduces reflective surfaces. However this site enemyforces.net says of the Sukhoi Su-47 'Berkut', "The forward-swept wing has a lower radar signature from the front hemisphere"

Carrier: What makes a "good carrier aircraft"?. Low take off speed would be one factor, which is why some (F-14 Tomcat) had variable-sweep wings, (though back-swept and which also seem out of fashion now, see [1]) Swept wings have better stall charateristics at high angle of attack, which is relevant for all fighter aircraft. Supposedly, no forward-swept wing(FSW) planes are in production, so I don't think anyone are contemplating Variable forward sweep, yet. Then again, see this at dreamlandresort.com which purports to show a Grumman Northrop design for a FSW with variable sweep! Here too [2] more recently. And Northrop Switchblade on Wikipedia!

This site century-of-flight.net says "Aircraft with forward-swept wings are highly manoeuvrable at transonic speeds". --220.101 (talk) ^\Contribs 01:54, 4 July 2010 (UTC)

Variable FORWARD sweep?! Sounds like a perfect recipe for structural failure! 67.170.215.166 (talk) 05:08, 4 July 2010 (UTC)

Why? I can't see why it would be any more of a problem than variable backward sweep. --Tango (talk) 06:18, 4 July 2010 (UTC)

More twisting loads on the wing pivots, for one thing -- what do you think is the reason why swept-back wings can be made from ordinary aluminum but swept-forward wings require fancy-schmancy composites? 67.170.215.166 (talk) 08:00, 4 July 2010 (UTC)

"More twisting loads on the wing pivots" - I can't see any justification for that statement.77.86.10.42 (talk) 12:18, 4 July 2010 (UTC)

If you experiment with a piece of paper, then you'll see why... 67.170.215.166 (talk) 23:48, 4 July 2010 (UTC)

You know I have absolutely no idea what that means, please read Wikipedia:Reference_desk/Guidelines#Guidelines_for_responding_to_questions - it's quite counterproductive to make unverifyable claims.87.102.23.18 (talk) 01:37, 5 July 2010 (UTC)

What I mean is, take a long, fairly narrow strip of paper and a portable fan, and hold it at an oblique angle to the fan's airflow at the end nearest the fan (as if it were a swept-back wing with the wing root facing into the airflow); the strip of paper should flutter a little about the horizontal, but come back to the horizontal after each oscillation. Got that? Good, now reverse the strip of paper so that you're holding it at the end farthest from the fan (as if it were a swept-forward wing with the wing tip facing into the airflow); now the strip of paper should twist one way (either up or down) as far as it will go, and stay that way. This is such a basic experiment for illustrating the aeroelastic properties of swept-back vs. swept-forward wings that I'm perfectly shocked that the three of you (Tango, 77.86 and 87.102) have no idea about it or about the implications of its results. Seriously, if the three of you had at least a little basic visualization skills between you, then you would've got my point about twisting loads without me having to digest the very basics for you. 67.170.215.166 (talk) 04:38, 5 July 2010 (UTC)

Yes but a wing isn't a completely unrigid structure - in the experiment you describe the strip of paper just bends back completely and flaps about in both cases - there is an article aeroelasticity and I can't see a mention of what you are describing it's not flutter. I originally thought you were talking about up/down (flapping) torsion, but I'm not sure if you mean torsion force that attempts to force the wing back.. (The link to 'responding to questions' was to explain the usefulness of supplying interwiki links or external references to help confirm or explain what you are saying)'.87.102.23.18 (talk) 13:30, 5 July 2010 (UTC)

Doesn't matter- I think Acroteroin has explained it below.87.102.23.18 (talk) 13:35, 5 July 2010 (UTC)

sorry for the inconveinience - it just wasn't clear what you were saying87.102.23.18 (talk) 13:49, 5 July 2010 (UTC)

Yeah, the Goa'uld really loved their death gliders. nerd joke. --mboverload@ 07:12, 4 July 2010 (UTC)

The WP article on FSW makes only passing mention, but FSWs exhibit divergent aeroelastic flutter characteristics which amplify wing twist in certain flight regimes, leading to failure. It can be controlled using composites, but the structure necessary to deal with it increases weight unacceptably in metal construction. Digital flight controls are also helpful. In general, in stealth design, re-entrant angles are avoided, as they focus reflections (think of a headlight's shape) rather than diffusing them. Acroterion _(talk) 16:35, 4 July 2010 (UTC)

Tin allotrope conversion

Why didn't the tin in my pewter spoon change from the beta form to the alpha form when it was in a freezer for a couple weeks? --Chemicalinterest (talk) 12:20, 4 July 2010 (UTC)

Firstly the change doesn't always happen immediately - ie the reaction can be delayed like crystallisation from a supersaturated solution.

Secondly Pewter contains metals that inhibit the allotrope change - see also Tin_pest#Modern_tin_pest_since_adoption_of_RoHS 77.86.10.42 (talk) 12:40, 4 July 2010 (UTC)

Yes it contained antimony and that is one of the substances used to prevent the conversion. --Chemicalinterest (talk) 18:24, 4 July 2010 (UTC)

Only pure tin is subject to tin pest -- that's why these days you always find it alloyed with other metals. 67.170.215.166 (talk) 23:33, 4 July 2010 (UTC)

No. Please stop giving incorrect answers. (Some forms of) Alloyed tin is also subject to tin pest. eg [3] p17/64_{what happened} google books. 87.102.23.18 (talk) 01:38, 5 July 2010 (UTC)

Fine, from now on I will not answer questions about metallurgy, since my knowledge of this subject is admittedly not up to date. As for questions about aerodynamics, I would recommend that you refrain from answering, considering the obvious lack of knowledge about the subject that you demonstrated during the discussion about swept-forward wings. 67.170.215.166 (talk) 10:23, 5 July 2010 (UTC)

Most tin alloys are not subject to tin pest. --Chemicalinterest (talk) 11:56, 5 July 2010 (UTC)

So the tin buttons on the French tunics which caused Napoleon to retreat from the Russian winter (tall story from chemistry teacher that one) were supposed to be pure? Does anyone know if its actually true? --BozMo talk 11:38, 5 July 2010 (UTC)

It would be hard to tell whether that story was true. --Chemicalinterest (talk) 11:58, 5 July 2010 (UTC)

The story is actually not true -- Napoleon had to retreat because his food supplies ran out -- but AFAIK there was a similar incident involving a Russian army unit posted in Siberia (in peacetime) during a winter that was so exceptionally cold (I believe it was some time during the early 19th century, but after the Napoleonic wars) that the tin buttons on their uniforms crumbled and they all had to be issued replacement uniform buttons. I think this was the source of the story about Napoleon. FWiW (OK, no more metallurgy answers from me for the next couple months at least -- I've realized that much of what I learned about the topic way back when has been disproved, and I gotta update the huge database in my cranium with reliable, up-to-date info on this subject.) 67.170.215.166 (talk) 00:17, 6 July 2010 (UTC)

Clarify.. As far as I know nobody makes and sells an alloy that is more susceptible to tin pest than pure tin for obvious reasons (it would be useless). So to say 'tin alloys' don't get tin pest is sort of true - since alloys of tin will be produced with an eye on retarding or eliminating tin pest.94.72.242.84 (talk) 01:54, 6 July 2010 (UTC)

Piano Lid Prop angle

Most modern grand pianos' lid props appear to form a 90º angle where they meet the underside of the piano's lid. It seems logical to me that the lid prop is less likely to slip at that angle because there would be a direct load transfer of the weight of the piano's lid to the support stick. That is, grand piano manufacturers intentionally use a 90º angle for safety reasons. Could someone show me the mathematics, perhaps using vector analysis, to prove my hypothesis? The reader may want to visit http://en.wiki.x.io/wiki/Grand_Piano to see a couple of pianos that do not appear to use the 90º angle. Note the Louis Bas grand piano of 1781 and Walter and Sohn piano of 1805.Don don (talk) 16:52, 21 June 2010 (UTC)

here with an angle less than 90 degrees downward slippage is impossible without raising the mass of the lid

You already asked, [4] as Dmcq might have hinted(?) - your hypothesis is wrong - at 90 degrees the only thing that is stopping slippage is friction. Whereas at more acute angles slippage is impossible since the mass of the lid needs to be raised for the support to be able to fold into the resting position.Sf5xeplus (talk) 13:59, 4 July 2010 (UTC)

Yes, after I posted my question on the mathematics page I thought that it should have been placed in the physics section. How can the original entry be deleted?Don don (talk) 18:25, 5 July 2010 (UTC)

I don't think it's necessary to delete it, I'll add a link to here. [5] 94.72.242.84 (talk) 01:57, 6 July 2010 (UTC)

I assume you didn't mean upward slippage of the support which should be prevented by a block.Sf5xeplus (talk) 13:59, 4 July 2010 (UTC)

Perhaps the most sensible solution would be to have slippage prevention blocks on both sides of support? Sf5xeplus (talk) 14:00, 4 July 2010 (UTC)

Also aren't some fixed and hinged at the lid ? Sf5xeplus (talk) 14:05, 4 July 2010 (UTC)

I know of no piano that has a hinge at point C. (See following paragraph.)Don don (talk) 20:21, 5 July 2010 (UTC)

Perhaps I should clarify the angle to which I am referring in my original question. Looking at the picture of a grand piano found at the right, let point A be the center of the piano lid hinge pin to the left of the pianist; point B is the center of the support stick’s hinge pin; and point C is where the support stick contacts the piano lid. Currently, I have in my possession data (segment lengths AB, BC, and CA) from more than one hundred pianos. Using trigonometry, I have found that the average for angle C is approximately 90 degrees, plus or minus one degree.Don don (talk) 18:45, 5 July 2010 (UTC)

The premise of your question is wrong; most concert grand pianos don't have a fixed angle for the lid. Generally the lid angle can be adjusted either by elongating a telescopic prop (like this one) or by using a replacement prop (this article on recording gives 38° for the long prop and 10° for the short one). The piano lid functions as a reflector for mid- and high-frequency sound; Music, physics, and Engineering by Harry F. Olson shows a 15dB differential of 4kHz volumes horizontally rightward (outward) of the lid vs. the hingeward side. In performance, concern grands have to function well in a variety of settings - on the level with the audience, above them (e.g. on the stage in a multi-use hall where the audience is seated on a flat floor like a basketball court) or below them (e.g. on the stage in a concert hall where the audience on raked seating). So the musician will want the lid adjusted to best present the piano's sound to the audience (further diagrams in Olson suggest this effect is marked for at least the top half of the piano's range). So they'll set the lid angle to suit the performance space. It's not going to slip because it's not relying on flat friction to hold it up (there's a hole, or several). -- Finlay McWalter • Talk 15:34, 4 July 2010 (UTC)

I have been unable to find the "telescopic prop" on the website to which you refer above (beethovenpianos.com). However, I thank you for your comments on angle A. (See my clarifying paragraph above.) Using the data that I have collected so far, angle A is approximately 32 degrees, plus or minus 2 degrees, when the longest lid prop is used on a grand piano. (Some concert grands have as many as four different lid props!) As far as I know, there are only three lid prop sizes readily available commercially, 31", 30" and 22".Don don (talk) 19:01, 5 July 2010 (UTC)

The prop resists the moment of the lid tending to turn on its hinge. The value of the moment is MGR.cosØ where M=mass of lid, G = gravitational constant, R = distance from hinge to center of gravity of lid, Ø = angle of elevation of lid. The force P exerted by the prop on the lid may have two components: P.sine@ and P.cos@ where @ is the angle between the prop and the lid. P.cos@ is a force parallel to the underside of the lid and, if present, it will cause the top of the prop to slide against the lid unless this is prevented by a block, notch or hole. P.sine@ counteracts the lid turning moment which implies that MGR.cosØ = PS.sine@ where S = distance from hinge to prop contact. The situation @ = 90 degrees is interesting because P.cos(90 degrees) = 0 meaning the prop has no tendency to slide against the lid. Nothing here requires R = S so the lid angle Ø can be chosen by the prop length and the OP's hypothesis is not unreasonable. I add the diagram below at request of the OP.

File:Piano lid.png Cuddlyable3 (talk) 13:05, 6 July 2010 (UTC)

Yes angle=90 is a Saddle point Local extrema, but saddle points local extrema aren't really safe at all.77.86.10.42 (talk) 16:50, 4 July 2010 (UTC)

No. It's just a local extremum. Cuddlyable3 (talk) 13:31, 5 July 2010 (UTC)

thanks corrected 87.102.23.18 (talk) 13:38, 5 July 2010 (UTC)

Surely the most logical reason for choosing the angle they do is to best project the sound from the piano towards the audience as it reflects off of the heavy lid. I doubt it has anything whatever to do with the angle of the prop. SteveBaker (talk) 04:46, 5 July 2010 (UTC)

Respond to DonDon - one advantage of having an angle of 90degrees is that it minimises the compressive force in the support making it less likely to break. I still don't entirely agree that it is done for safety reasons since there are safer angles (ie internal angle less than 90) that work in combination with a block stopping the support slipping upwards. Nevertheless your point has a lot of truth in it.94.72.242.84 (talk) 19:31, 5 July 2010 (UTC)

That's possible - but piano lids just aren't that heavy and there is little or no penalty in having a totally over-engineered strut that could comfortably withstand ten times that weight. It's utterly trivial for the piano maker to design a strut that could place the lid at any angle he pleases. Hence the crux of the design here is most certainly not about saving 10 cents worth of wood in the strut and placing at the safest possible angle! It's about getting the lid to the optimum angle for sound reproduction...and all of this stuff about what is the least force and at what angle and slippage versus longitudinal force is totally irrelevant twaddle! SteveBaker (talk) 13:40, 6 July 2010 (UTC)

After the optimum angle of the lid is determined it remains to design the point on the lid where the strut is going to touch, and the angle between the lid and the strut. The tangential component of the force from the strut provides the torque to prevent the lid from closing, while radial and axial components of the force are of no use and can be chosen to be zero. That's why the strut should be perpendicular to the lid. Bo Jacoby (talk) 19:35, 6 July 2010 (UTC).

SI prefixes (redux)

The earlier question about 10²⁷ got me wondering... Among the SI prefixes, why was deca- given the two-letter prefix da? I realize it couldn't be d because that is for deci-, but why couldn't it have been D, just as we have m for milli- and M for mega-? Thank you kindly. — Michael J 16:41, 4 July 2010 (UTC)

Did you spot SI_prefixes#Proposed_changes - it seems they are aware of the inconsistences, but haven't done anything yet.77.86.10.42 (talk) 17:32, 4 July 2010 (UTC)

I saw that. I just wondered why it wasn't done in the first place. — Michael J 17:43, 4 July 2010 (UTC)

I see what you mean. The page Kilo- has the answer - the odd ones out hecto, deca, kilo (and centi, deci, milli) are original Metric system prefixes (year 1795) so they were already introduced and in use when the SI-system was started. I suppose it would have been confusing or impossible to get people to change from lower case prefixes which they had been using for over 100 years

Clearly the original metrix prefixes don't follow the 'same word root/ upper or lower case pattern' as do the later SI type.

In fact the metrix prefixes use a greek derived word for 10,100,1000 and a latin derived word for 0.1,0.01,0.001 .... Metric_system#Prefixes 77.86.10.42 (talk) 18:27, 4 July 2010 (UTC)

Adidas Jabulani

Please see http://commons.wikimedia.org/wiki/Category:Adidas_Jabulani - as far as I can tell all official 'jabulani' balls are the '8 sided' truncated tetrahedron design, yet there are other designs in commons

Can anyone confirm that this is a fake? Thanks.77.86.10.42 (talk) 16:46, 4 July 2010 (UTC)

I can't directly confirm, but I would note the presence of the word "Replique" in the name of the file (replica?), and also the fact that the match balls seem to be smooth, whereas there is distinct stitching on the one shown in the file. --TammyMoet (talk) 16:49, 4 July 2010 (UTC)

The Replique's are the cheaper version for sale to the mass market. See http ://hubpages.com/hub/Which-adidas-Jabulani-World-Cup-2010-official-soccer-ball-is-right-for-you (url split as for some reason that site is on the blacklist) for a truncated list of the different available Jabulani's. Nanonic (talk) 17:35, 4 July 2010 (UTC)

Thanks, the replicas seem to be more expensive than the ones with the new design.. odd

Resolved

Diopters

magnifying lens

magnifying and a diminishing lens

In corrective lenses, what does the unit diopter determine? Is this to do with how curved the lens is, how thick it is? Clover345 (talk) 18:39, 4 July 2010 (UTC)

Please read the article Dioptre. Cuddlyable3 (talk) 18:45, 4 July 2010 (UTC)

Thank you. I read that before I asked but its too scientific for me to understand. Clover345 (talk) 21:26, 4 July 2010 (UTC)

It's a measure of the strength of the lens - a higher value means a more powerful (either magnifying or diminishing lens)

A higher power lens is more curved, and being more curved means it is thicker. For a magnifying lens it's thicker in the middle, for a diminishing lens it's thicker at the edges.

So a higher dioptre lens will be thicker, and more curved than a lower dioptre lens.

I found some useful images at Eyeglass prescription. Note that a negative value is used to denote a diminishing lens.77.86.10.42 (talk) 21:35, 4 July 2010 (UTC)

If it has a positive diopter value you can use a lens as a Burning glass, as some boys discover to the discomfort of a few ants. Cuddlyable3 (talk) 22:15, 4 July 2010 (UTC)

If the sun is bright enough, you can even use a lens to light a campfire (like in The Mysterious Island). 67.170.215.166 (talk) 23:30, 4 July 2010 (UTC)

Though note that in Lord of the Flies, William Golding got it completely wrong by describing the short-sighted Piggy's spectacles being used in this way, even though lenses to correct myopia (such as my own) are diverging, somewhat diminishing my respect for the author when I read the book as a child. I thought I also remembered him describing a crescent Moon rising at sunset, but have subsequently failed to find such a passage - anyone else recall this? 87.81.230.195 (talk) 23:59, 4 July 2010 (UTC)

I've read the Lord of the Flies in high school, but it was a long time ago and I don't remember the details; the one thing I do remember is the conflict between Ralph and Jack, and the gradual transformation of all those civilized schoolkids into savages. 67.170.215.166 (talk) 04:44, 5 July 2010 (UTC)

You (87.81) are right about the crescent moon mistake - I remember it being mentioned in one of Martin Gardner's books. I'll try to find a reference later. AndrewWTaylor (talk) 08:14, 5 July 2010 (UTC)

Reptiles' sense of time

NOTE: I added the above "null" sections so that everyone's links will still work. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:59, 6 July 2010 (UTC)

Reptile's sense of time

Would a reptile, being cold-blooded, subjectively experience a cold day as passing very quickly, but a hot day as going on for much longer? 92.15.12.165 (talk) 19:24, 4 July 2010 (UTC)

There is no reason why it would. Cold-blooded does not mean it has cold blood; it only mean that it is poikilothermic. --Chemicalinterest (talk) 20:07, 4 July 2010 (UTC)

Do I really need to point out to you that "cold-blooded" is a common synonym for poikilothermic and that I and other people using that phrase do not mean that it literally has cold blood?

I'm wondering if, since its body would be hotter on a hot day, therefore its neurones should be faster, therefore its gets more thinking done within a constant time period compared with a cold day. Hence subjectively objective time seems to go more slowly for it on a hot day. 92.15.12.165 (talk) 21:49, 4 July 2010 (UTC)

Haha I thought you meant that since it had cold blood it would see the "good" cold days passing quickly and the "bad" hot days (that heat up his blood) passing very slowly.--Chemicalinterest (talk) 10:59, 6 July 2010 (UTC)

This is an interesting question. We don't fully understand how humans keep time neurally on a minute-to-minute basis, much less reptiles. We do have a good understanding of how circadian rhythms are implemented in the brain, and I believe there is evidence that the day-clocks in cold-blooded animals are temperature-compensated to some degree, but do run a bit slower when body temperature drops. In short, the answer is not known. (And I haven't even addressed whether "subjective" actually means anything for a reptile.) Looie496 (talk) 21:55, 4 July 2010 (UTC)

Right, the question as phrased is about reptiles' qualia, which in principle are not amenable to objective analysis. The only way to know them for sure is to be the reptile in question. --Trovatore (talk) 22:12, 4 July 2010 (UTC)

Yes, but sleep passes very quickly for people (?) and there must be some objective difference in brain activity between the two.. Surely someone must have done a study on 'nerve activity in hot and cold reptiles' for us to be able to draw some sort of conclusion about the 'level of awakeness' or 'quality of experience' in reptiles as they get colder, if not whether times passes quick for them.77.86.10.42 (talk) 22:26, 4 July 2010 (UTC)

Nerve activity certainly slows down as body temperature drops. But there is no guarantee that timekeeping has a simple relationship to neural activity. Circadian timekeeping, for example, doesn't depend on neural activity -- the timekeeping process is driven by gene transcription. As I said, we really don't know at this point what mechanism determines subjective time, even in humans. It is probably neural activity at some level, but there are many types of neural activity, with different temperature dependencies, some of them pretty shallow. Human time estimation is definitely affected by body temperature, but since we are warm-blooded it is possible that there is less evolutionary pressure to counteract this in mammals than in reptiles. Looie496 (talk) 22:52, 4 July 2010 (UTC)

Discussion moved to Wikipedia_talk:Reference_desk#Grammitical_edits_to_question_header_on_science_desk_causing_offence please discuss there, and do not edit the questioneer's section heading further. Thank you.

Is there a behavioral explanation?

Is there a behavioral explanation for why the toilet-trained cat in this video is putting toilet paper in the toilet bowl? Bus stop (talk) 20:03, 4 July 2010 (UTC)

Yes, the cat has probably seen the human "parents" using paper after doing shit. So it has recorded the scene and trained itself to do so though of course it cannot understand why they do this. For the cat it is a ritual that its "parents" (who are humans of course) but to cat they are just big cats who are leaders of the pack who provide the cat food and protection, and what they do must be followed as a sign of respect  Jon Ascton  (talk) 21:57, 4 July 2010 (UTC)

No. It is instinctive behaviour of a cat to scratch earth over its stools. Tame cats try to do this even when there is nothing to scratch, as when the one in the video scratches at the plastic seat. At some point it discovers that a paper roll gives endless scratching satisfaction, that's all. Training a cat this way does not involve the owner performing for the cat to imitate. Cuddlyable3 (talk) 22:08, 4 July 2010 (UTC)

No, I have seen dogs and cats trying to involve the acts they have seen humans doing, and trying to reach out for electric switchs etc for no reason  Jon Ascton  (talk) 23:04, 4 July 2010 (UTC)

I could understand cats and dogs hitting switches for things because there's an immediate "reward" in that some action occurs that they desired. I find it harder, nigh impossible, to believe that a cat would paw at toilet paper just because they had seen a human do it. There's no "reward" for the cat. If the paper is close enough, as in the video, they may paw at that. Notice also that the cat in the video paws all around the seat. It's not unusual for a cat to paw at the walls and other vertical surfaces around a litter box either. (WP:OR warning) Around one of our litter boxes, we have a piece of hard plastic because we found the cats were scratching at the wall and causing damage. They still scratch at the plastic sheet but now it doesn't damage the walls. PS That's a good sized deuce for a cat! Dismas|^(talk) 00:19, 5 July 2010 (UTC)

Maybe pet psychology is different in India than in the West (!) Perhaps the evolutionary relation between human and cat/dog followed a different route to evolve in India, you know due to we-are-spiritual-you-are-materialistic factor  Jon Ascton  (talk) 03:50, 5 July 2010 (UTC)

I very much doubt they do it out of respect. Animals do things to show respect to the alpha, but I've never heard of them doing things to show respect to their parents (unless the parent is the alpha, of course). They probably do it because they have learnt from their parents and assume their parents were doing it for a reason. Animals don't do detailed analyses of the reasons for the things they learn (humans often don't either), they just imitate it when they want the same result (in this case, to not need the toilet any more). It could just be the usual cat instinct to scratch after defecating, as Cuddyable says, though - they certainly will scratch and things other than dirt if there isn't dirt around for no reason other than instinct. --Tango (talk) 19:47, 5 July 2010 (UTC)

Strange beetle

I took a picture of a beetle and uploaded it to Flickr. Can anyone help me identify it?

Americanfreedom (talk) 22:03, 4 July 2010 (UTC)

Reminds me of a Cockchafer, (which is probably isn't) - maybe you could look at the family Scarabaeidae while you wait.. or http://commons.wikimedia.org/wiki/Category:Species_of_Scarabaeidae (there's only 287 to go through..)

I think you need to tell us where you are to aid the indentification, eg region of the country you're in, not your address :) 77.86.10.42 (talk) 22:07, 4 July 2010 (UTC)

And how big is it, _{and what is that thing in the background - a tray with a picture on or something?}77.86.10.42 (talk) 22:10, 4 July 2010 (UTC)

This is definitely not a cockchafer, look at the antennae. Kinda hard to tell from that angle, but my guess would be that this is a fairly large longhorn beetle, maybe Cerambyx sp. or Neocerambyx sp., family Cerambycidae. Some of those guys, although of course not the largest of the beetles in general, tend to get impressively large. Let me know where you took the picture and maybe I can narrow it down to the species. --Dr Dima (talk) 23:08, 4 July 2010 (UTC)

I can't help directly, but here is a site [6] that may help you now or in the future. Caesar's Daddy (talk) 07:27, 5 July 2010 (UTC)

I took a closer look at the longhorn beetle picture you've got, it may be Prionus sp.. --Dr Dima (talk) 08:04, 5 July 2010 (UTC)

Without giving away to much (My dad's worried about security) i live in Northern California.

Americanfreedom (talk) 03:02, 6 July 2010 (UTC)

The beetle is not a security threat :) . Northern California is precise enough, so no need to tell us more than that about your location. I will look up the species tomorrow when the library opens. It does not look like Prionus californicus (AFAIR, P. californicus has prominent spines on the sides of the pronotum, which I can't see in your specimen). Anyway, tomorrow I will probably have a better guess of what it is. All the best, --Dr Dima (talk) 05:40, 6 July 2010 (UTC)

This is probably Prionus lecontei. There are only two Prionus species found in California: P. californicus and P. lecontei. The former has 12 antennal segments, the latter has 13. Looks like your one has got 13 ... --Dr Dima (talk) 03:08, 7 July 2010 (UTC)

abbe or v number

I haven't been able to find a thing on this - I was wondering what would be a typical abbe number (or some other comparative figure at other wavelengths) (whatever measure of chromatic aberration is relevant) for a camera lens assembly - ie is it higher than 59 as per crown or CR39 glass. I was thinking about a mid priced lens rather than super expensive, or super cheap..77.86.10.42 (talk) 23:02, 4 July 2010 (UTC)

Mig-29

Does the Mig-29 require a starter cart to start its engines? Or does it have self-start capability? Thanks in advance! 67.170.215.166 (talk) 23:37, 4 July 2010 (UTC)

This article says it has a "GTDE-117 gas-turbine starter-APU". Moreover this article has a "RD-33 Engine Start" section which says that stored air (from engine bleed) is normally used to start the engines, with the APU or battery-only as fallbacks. I dread to think how quickly you'd flatten your battery starting (presumably just one) engine. -- Finlay McWalter • Talk 00:04, 5 July 2010 (UTC)

Don't know about this Mig thing, but think I heard very interersting thing about the starting-of-engine process of a large propellor (probably a pre WW2 model) aircraft. They put a 12 gauge shotgun cartridge and fire it to start the engine ! Is that true...? Jon Ascton  (talk) 03:20, 5 July 2010 (UTC)

Yep - they really exist. See Coffman engine starter. SteveBaker (talk) 04:37, 5 July 2010 (UTC)

I knew that the Canberra bomber used a cartridge starter; didn't know that piston-engine aircraft also used this system... 67.170.215.166 (talk) 04:48, 5 July 2010 (UTC)

Well, talking of novel uses of 12 gauge shotgun cartridge, is there any machine which exploits the rush of its blast to dig a hole in ground when you have no time for a shovel ? Jon Ascton  (talk) 05:56, 5 July 2010 (UTC)

That would not be very effective, a shovel would work much better. Now if you want to get at water underneath a layer of ice an inch or so thick, maybe you could have more luck with that. Googlemeister (talk) 13:12, 6 July 2010 (UTC)

Submarine aircraft carriers of Japan employed pre-heaters for aircraft engine oil so that minimum time would be spent while vulnerable on the surface for starting and launching floatplanes. Cuddlyable3 (talk) 13:18, 5 July 2010 (UTC)