The Value Of An Apology, At Least From A Republican's Perspective!!
in [Digital Cameras]
|
Prev: Pittsburgh
Next: Incompatible jpeg?
From: Neil Harrington on 26 Sep 2009 12:49 Chris Malcolm wrote: > In rec.photo.digital D. Peter Maus <DPeterMaus(a)worldnet.att.net> > wrote: > >> No one has ever said that the bumblebee can't fly. Clearly it >> can, it happens every day. Science has never been so blind as to >> make such a claim. But what Science HAS said, is that the bumblebee >> is UNSTABLE in flight, an aerodynamically unsound design. This >> doesn't mean or even imply that it can't fly. Just that there would >> be easier and better ways to achieve flight. > > Not so. What science said until recently was simply that according to > our understanding of fixed wing aeroplane flight the bumblebee had > insufficient wing area to fly. That's the story as I always heard it too, "insufficient wing area to fly." But the idea that "SCIENCE said" that is something I'm very skeptical about. What sort of science could possibly arrive at such a conclusion? In the first and most obvious place, a bumblebee is in no way comparable to a fixed wing aircraft. What it is comparable to is an ornithopter, and I don't think anyone ever built an ornithopter that could actually fly, so that's a kind of aircraft that you wouldn't expect there to be enough scientific data on to arrive at any conclusions about bumblebees. > Not that it was unstable. It is in fact > unusually stable in flight due to its relatively low centre of gravity > and large effective dihedral. How do you establish the "effective dihedral" of wings that are beating at such an incredibly fast rate, though? I don't believe dihedral has anything to do with it. Even if you could calculate the AVERAGE dihedral of a bumblebee's wings, you'd still have to establish the incidence in order for it to mean anything. Dihedral produces lateral stability only because (or if) the wing also has positive incidence. > The problem was that theoretically the > wings weren't large enough to do the job they clearly were doing. So > something was wrong with a simplified analysis of bee flight based on > fixed wing aerodynamics. > > In the 1990s the important missing factor was discovered -- the > trailing edge vortices which are such an important source of lift loss > in fixed wing aerodynamics were exploited to add lift in the flight of > many insects. In the 2000s high speed cinematography and mechanical > simulations of bee wing motion demonstrated in practical detail that > this was in fact what the bee was doing. That's interesting. I'd still like to know where the original "insufficient wing area" story got started, though. Absent some proof of a serious scientific analysis in the past claiming that, I'm inclined to believe it may be more of an urban myth. It's a popular one anyway, and will probably go on forever -- like the widely held belief that before Columbus everyone thought the earth was flat.
From: Ray Fischer on 26 Sep 2009 14:49 Neil Harrington <secret(a)illumnati.net> wrote: >Chris Malcolm wrote: >> In rec.photo.digital Bill Graham <weg9(a)comcast.net> wrote: >> >>> The principal is simple and logical. When you make laws against >>> carrying guns, only the law abiding citizens will obey these laws, >>> and so only the criminals will carry guns, and the crime rate will >>> go up. When you allow everyone to carry guns, some percentage of the >>> honest people will do so, and this is bad news for the criminals, >>> and the crime rates will go down. Or. at least, the criminals will >>> go elsewhere. >> >>> Why the hell the stupid liberals can't see and understand this is >>> beyond me, but they can't, and haven't been able to for all of my >>> life. >> >> It's the evidence, Bill. What those stupid liberals consider is the >> evidence. What the stupid fools don't realise is that if you take >> facts seriously you might have to change your mind about some >> things. That's why if you know you're right it's so important to >> ignore facts. But liberals are too stupid to realise that. > >All the evidence and facts are on the pro-gun side of the argument, Chris. That explains the positive correleation between gun availablility and gun deaths? What flavor was your KoolAid? -- Ray Fischer rfischer(a)sonic.net
From: tony cooper on 26 Sep 2009 21:45 On Sat, 26 Sep 2009 16:50:07 -0700, "Bill Graham" <weg9(a)comcast.net> wrote: > >"Neil Harrington" <secret(a)illumnati.net> wrote in message >news:oOmdneO8vOH6piPXnZ2dnUVZ_jmdnZ2d(a)giganews.com... >> D. Peter Maus wrote: >>> On 9/23/09 10:01 , Chris Malcolm wrote: >>>> In rec.photo.digital Bill Graham<weg9(a)comcast.net> wrote: >>>> >>>>> The principal is simple and logical. When you make laws against >>>>> carrying guns, only the law abiding citizens will obey these laws, >>>>> and so only the criminals will carry guns, and the crime rate will >>>>> go up. When you allow everyone to carry guns, some percentage of >>>>> the honest people will do so, and this is bad news for the >>>>> criminals, and the crime rates will go down. Or. at least, the >>>>> criminals will go elsewhere. >>>> I think I unknowingly managed to take a photograph of you last week: http://tonycooper.smugmug.com/photos/651841603_9fsaJ-L.jpg -- Tony Cooper - Orlando, Florida
From: Savageduck on 26 Sep 2009 22:03 On 2009-09-26 18:45:02 -0700, tony cooper <tony_cooper213(a)earthlink.net> said: > On Sat, 26 Sep 2009 16:50:07 -0700, "Bill Graham" <weg9(a)comcast.net> > wrote: > >> >> "Neil Harrington" <secret(a)illumnati.net> wrote in message >> news:oOmdneO8vOH6piPXnZ2dnUVZ_jmdnZ2d(a)giganews.com... >>> D. Peter Maus wrote: >>>> On 9/23/09 10:01 , Chris Malcolm wrote: >>>>> In rec.photo.digital Bill Graham<weg9(a)comcast.net> wrote: >>>>> >>>>>> The principal is simple and logical. When you make laws against >>>>>> carrying guns, only the law abiding citizens will obey these laws, >>>>>> and so only the criminals will carry guns, and the crime rate will >>>>>> go up. When you allow everyone to carry guns, some percentage of >>>>>> the honest people will do so, and this is bad news for the >>>>>> criminals, and the crime rates will go down. Or. at least, the >>>>>> criminals will go elsewhere. >>>>> > I think I unknowingly managed to take a photograph of you last week: > http://tonycooper.smugmug.com/photos/651841603_9fsaJ-L.jpg No that couldn't be Bill. That guy is carrying openly, quite legally. Bill's preference is to carry concealed without a permit. -- Regards, Savageduck
From: Chris Malcolm on 27 Sep 2009 06:47
In rec.photo.digital Neil Harrington <secret(a)illumnati.net> wrote: > Chris Malcolm wrote: >> In rec.photo.digital D. Peter Maus <DPeterMaus(a)worldnet.att.net> >> wrote: >>> No one has ever said that the bumblebee can't fly. Clearly it >>> can, it happens every day. Science has never been so blind as to >>> make such a claim. But what Science HAS said, is that the bumblebee >>> is UNSTABLE in flight, an aerodynamically unsound design. This >>> doesn't mean or even imply that it can't fly. Just that there would >>> be easier and better ways to achieve flight. >> >> Not so. What science said until recently was simply that according to >> our understanding of fixed wing aeroplane flight the bumblebee had >> insufficient wing area to fly. > That's the story as I always heard it too, "insufficient wing area to fly." > But the idea that "SCIENCE said" that is something I'm very skeptical about. > What sort of science could possibly arrive at such a conclusion? > In the first and most obvious place, a bumblebee is in no way comparable to > a fixed wing aircraft. What it is comparable to is an ornithopter, and I > don't think anyone ever built an ornithopter that could actually fly, so > that's a kind of aircraft that you wouldn't expect there to be enough > scientific data on to arrive at any conclusions about bumblebees. >> Not that it was unstable. It is in fact >> unusually stable in flight due to its relatively low centre of gravity >> and large effective dihedral. > How do you establish the "effective dihedral" of wings that are beating at > such an incredibly fast rate, though? The point about dihedral is that as the plane (or insect) tips over to one side the effective length of the wing on the lowered side increases, increasing the lift on that side, and the effective length of the other wing decreases, decreasing the lift. So the forces naturally restore level flight. At a first approximation you could simply average over the range of motion of the flapping wing. As a second approximation you could assume simple harmonic motion of the wing and average over that, which would lead to much the same result :-) Or experimentally you could use high speed photography to map the trajectory of the flapping wing and integrate, or simply measure the forces (recent analysers of bee flight have developed various ways of doing all that). > I don't believe dihedral has anything > to do with it. I didn't say it had anything to do with the claim of bees not being able to fly. You raised the red herring of that claim having something to do with stability. I used the dihedral and low centre of gravity of the bee to point out that stability wasn't a problem in bee flight, and wasn't what the controversy was about. Bees are amongst the most basically stable of insect fliers, simply because their "design" is optimised for the carrying of heavy loads -- they're big nectar tankers for transporting nectar loads back to the hive. Regardless of exactly what the exact effective dihedral of a bee's wings is, there's no doubt that there's quite a fair dihedral. Modern high speed photography has shown that. > Even if you could calculate the AVERAGE dihedral of a > bumblebee's wings, you'd still have to establish the incidence in order for > it to mean anything. Dihedral produces lateral stability only because (or > if) the wing also has positive incidence. I think you're confusing incidence with angle of attack. Given a bee's bent and rather unaerodynamic shape, and the fact that it flies with its undercarriage down, it would be hard to decide what the longitudinal aerodynamic axis of a bee's body in flight actually was. The bee wing angle of attack varies all the time as the wing moves. But what the angles are doesn't matter. All that matters for dihedral to work is that lift is being generated by wings. It doesn't matter how. Since bees do actually fly then lift is obviously being generated therefore dihedral effects occur. >> The problem was that theoretically the >> wings weren't large enough to do the job they clearly were doing. So >> something was wrong with a simplified analysis of bee flight based on >> fixed wing aerodynamics. >> >> In the 1990s the important missing factor was discovered -- the >> trailing edge vortices which are such an important source of lift loss >> in fixed wing aerodynamics were exploited to add lift in the flight of >> many insects. In the 2000s high speed cinematography and mechanical >> simulations of bee wing motion demonstrated in practical detail that >> this was in fact what the bee was doing. > That's interesting. > I'd still like to know where the original "insufficient wing area" story got > started, though. Absent some proof of a serious scientific analysis in the > past claiming that, I'm inclined to believe it may be more of an urban myth. It has been difficult to track down the source of the claim. According to Wikipedia the earliest published claim comes from the introduction to "Le Vol des Insectes" in 1934 by the entomologist Antoine Magnan, who was relying on unspecified calculations done by his assistant Andre Sainte-Lague. But the story was verbally current long before that publication. What Wikipedia says about that is that "Some credit physicist Ludwig Prandtl (1875-1953) of the University of Gottingen in Germany with popularizing the myth. Others say it was Swiss gas dynamicist Jacob Ackeret (1898-1981) who did the calculations." and more generally "It is believed that the calculations which purported to show that bumblebees cannot fly are based upon a simplified linear treatment of oscillating aerofoils. The method assumes small amplitude oscillations without flow separation." > It's a popular one anyway, and will probably go on forever -- like the > widely held belief that before Columbus everyone thought the earth was flat. Such beliefs would soon die out if we gave our children a better scientific education. The problem is that a lot of people, especially in the US, think that our children are already being exposed to too much science, which carries the danger of encouraging scepticism about the literal truth of religious scriptures believed to be the Word of God. The "according to science bees can't fly" is a very popular simple way of explaining to ignorant gullible people why they shouldn't trust science. And so long as plenty of people are making plenty of money out of encouraging people to distrust science it's bound to go on. -- Chris Malcolm |