Scientist debunks flying myth. (Cambridge, UK)

One of the most common myths in science, why aircraft fly, has been debunked by a Cambridge University scientist, Prof Holger Babinsky.

http://www.youtube.com/watch?v=UqBmdZ-BNig

By David Millward, and Nick Collins

 Aeroplanes can fly because their wings cause the air pressure underneath to be greater than that above, lifting them into the air.

But engineers have for years been frustrated by a theory which wrongly explains what causes the change in pressure to occur.

The myth is commonly found in school textbooks and aeroplane flight manuals, and is so widely believed that even Einstein was rumoured to subscribe to it.

Now a Cambridge scientist has become so fed up with the bogus explanation that he has created a minute-long video to lay it to rest once and for all.

The video, published on YouTube by Prof Holger Babinsky of the university’s engineering department, seeks to explain in simple terms why the myth goes against the laws of physics.

According to conventional wisdom the pressure change happens because the air on the curved upper surface of the wing has further to travel than that below the flat underneath surface, meaning it must travel faster to arrive at the other side of the wing at the same time.

In fact the real explanation is nothing to do with the distance the air has to travel. The curvature of the wing causes the change in air pressure because it pushes some of the air upwards, which reduces pressure, and forces the rest beneath it, creating higher pressure.

A law known as the Bernoulli equation means that when pressure is lower, air moves faster – so the air stream above the wing does move more quickly than the one below, but this is not what causes the difference in pressure.

Prof Babinsky proved his theory by filming smoke passing across a wing.

If traditional wisdom had been correct the smoke above and below the wing should have reached the front edge at the same time.

The video demonstrates that the explanation is fundamentally flawed because the plume above the wing reached the edge much sooner than the plume below.

If the distance the air had to travel was causing the pressure to change, then a boat's sail – where the air travels the same distance on the inside and outside of the curve – would not work, Prof Babinsky said.

He added: "I don’t know when the explanation first surfaced but it’s been around for decades. You find it taught in textbooks, explained on television and even described in aircraft manuals for pilots.

"There is no law in physics which states when streams of particles start at the leading edge of the wing they should reach the tailing edge at the same time.

"I've even heard a story that Einstein drew a design for an aircraft wing with a long, squiggly line on top of an aerofoil to make the distance for the air to travel greater, but this would not work."

Source:   http://www.telegraph.co.uk

Status of General Aviation: Some Notes/Links

Harry R. Clements, The Rise and Fall of General Aviation — An Economists View with Focus on Single Engine Aircraft and the Impact of Airline Deregulation (2000 conference paper)

Matt Thurber, Free Fall: The Unexpected Decline of the Billion Dollar General Aviation Industry (Tab Book, 1995).  Seems to be out of print (Amazon link) Author indicates it was never published.

Janet R. Daly Bednarek and Michael H. Bednarek, Dreams of Flight: General Aviation in the United States.  College Station, Tex.: Texas A&M University Press, 2003. Pp. xviii+191   (Reviewed in Technology and Culture, Volume 45, Number 3, July 2004, pp. 629-630).  "Overexpansion and increased federal regulation precipitated a steep and apparently permanent decline in sales of general aircraft [...] commercial and military aviation interests have largely succeeded in limiting general avia- tion’s influence. [...] Faced with declining numbers of pilots and increasing costs for flight training, aircraft, and maintenance, American general aviation enters its second century facing an uncertain future. Still, interest and enthusiasm among America’s general aviators remain strong, and new technologies such as ultralight aircraft continue to fuel a fascination with powered flight."  (TL 721.4.B38)  Also see Bednarek's bibliography in General Aviation: An Overview.

Joseph J. Corn, The Winged Gospel (OUP, 1983) [TL 521.C643]. 

Dominick Pisano, "The Social and Cultural History of Aviation and Spaceflight" 2003

J.G. Wensveen, Air Transportation: A Management Perspective (6th ed, 2007, link), see section 4, The General Aviation Industry, pp 111ff, for a useful overview.

General Aviation Statistics (AOPA)
FAA Aviation Statistics

James Lardner and Robert Kuttner, Flying Blind: Airline Deregulation Reconsidered (Demos, June 24, 2009).

GAO:  AIRLINE DEREGULATION: Reregulating the Airline Industry Would Likely Reverse Consumer Benefits and Not Save Airline Pensions (2006).

Matt Thurber, Can general aviation reverse its decline (Blog: 03-2011)

Robert Goyer, Is Flying really that Expensive?  (Blog: 03-2011) References an APA whitepaper: "Role of Prices in the Decline and Renewal of General Aviation" (2009).  Both make case that expenses apart from A/C have tracked inflation.  A/C have been 2.5-4x rate of inflation, hourly cost of operation now far exceeds rental rates for most users.  Goyer has another blog post Part 23 Do Over where he mentions a number of experimentals which he would never fly again, but does not list them.  One comment:  "Come on Robert! First you dangle your list of scariest homebuilts right in front of our noses; Then you yank it away again [...] Be a man and fess up the list. Informing the public about designs which you believe top be really scary to fly would be a valuable public service. Perhaps your bosses are more worried about the flood of lawsuits such an admission might cause,"

Kerry Kovarik, A Good Idea Stretched Too Far: Amending the General Aviation Revitalization Act to Mitigate Unintended Inequities (article, 2008) 

Eric A. Helland, Alexander T. Tabarrok, Product Liability and Moral Hazard: Evidence from General Aviation (article, 2008)

Eric Helland and Alex Tabarrok, Crash and Learn: Consumption Externalities and the Reduction of Aircraft Accidents (working paper, 2007)

Phillip J. Kolczynski, GARA: A Status Report (Blog, 2001)

Scott Tarry, "Issue Definition, Conflict Expansion, and Tort Reform: Lessons from the American General Aviation Industry" (article, 2001)

William Keith Stockman, The Crash of General Aviation: A Public Choice Perspective (PhD Dissertation, George Mason University, 1996).  Argues that "rent seekers" are the primary cause of the decline of general aviation.  "The industry and its users have fallen victim to the successful rentseeking of of others and have only recently had any success in reversing this trend.  {MVO notes passage of GARA} Though durable good's models do offer some explanations for the industries woes, the majority of the evidence points to a public choice explanation.  Thus, the industry should look toward public choice solutions if it desires to reverse the current trend"  (p. 8)

Lawrence J. Truitt, Scott E. Tarry, The Rise and Fall of General Aviation: Product Liability, Market Structure, and Technological Innovation (article, 1995)

GARA: The General Aviation Revitalization Act of 1994 (Public Law 103-298)
The complete text of the 1994 law.

United States Airline Deregulation Act (1978):  Alfred Kahn Overview.  

MotoCzysz E1PC

Finally, an electric bike that packs some serious performance. The E1PC produces 100 hp and can top at least 140 mph. Not close to the stock Hayabusa, but still very impressive. True it broke down at the recent Isle of Man TTs, but this may well be a peek at "the motorcycle of the future". Not indications of weight and cost is astronomical at this time. Well, they are using batteries built by the same folks that build 'em for NASA. Check out related article here. My next bike?

More Google Goodies

Russ pointed out two new Google APIs which are of particular interest. The Prediction API "enables access to Google's machine learning algorithms to analyze your historic data and predict likely future outcomes". It will take your labeled data, run supervised learning algorithms, and allow you to predict. I've not looked too hard, but I don't see just which ML algorithms they are offering (Naive Bayes, SVM, KNN, etc). But how cool is this? Well, pretty cool. But, Russ also points out BigQuery by Google: "a web service that enables you to do interactive analysis of massively large datasets. Scalable and easy to use, BigQuery lets developers and businesses tap into powerful data analytics on demand". Terrabytes, billions of rows per seconds. Wow.

Also check out Lessons learned developing a practical large scale machine learning system. And the first lesson? "Keep it simple (even at the expense of a little accuracy)".

Now these, all by themselves, are a really good reason to learn Python. :-)

Berkeley DB/GDBM Links

PhiloLogic uses GDBM (GNU Database Manager) for word searches. As we are starting to think about a new PhiloLogic series (the infamous "4"), we have been looking at a number of design and implementation issues, including advanced indexing schemes. For example, Clovis did a preliminary examination of various fuzzy matching systems. Richard and I have been starting to look at newer GDBM tools as well as Berkeley DB. Here are a few links and alternatives Richard proposed which I think we should experiment with and/or read:

Older perl-5 style: the tie function:
http://perldoc.perl.org/functions/tie.html
this lets you tie any complex data structure into a perl scalar, array, or hash, as you wish.
http://perldoc.perl.org/perltie.html
This is great for "hiding" object-oriented interfaces in a simple, "perl-ish" way. It can wrap GDBM or Berkeley, or MySQL, or SQLite, or Hadoop...and so on.

The low-level perl GDBM_File module:
http://search.cpan.org/~dapm/perl-5.10.1/ext/GDBM_File/GDBM_File.pm
tie and dbmopen both use this core perl module. On some mac's, I have had to Recompile perl to get GDBM_file working. You can't get it from CPAN.

The low-level perl Berkeley DB module:
http://search.cpan.org/~pmqs/BerkeleyDB-0.39/BerkeleyDB.pod
Pretty nice, but doesn't support all of the awesome Berkeley DB features, like joins. the python binding will do joins for you, at C speed. the $db->associate($secondary, \&key_callback) function lets you automatically maintain a secondary index. the DBM Filter functionality will do customized byte packing and unpacking for you transparently.

One other DBM product you might want to look at it is Tokyo Cabinet:
http://1978th.net/tokyocabinet/
It runs Mixi, the Japanese equivalent of Facebook, as I understand it, and some googling suggest that it's quite hot in the noSQL world. It's certainly faster than BerkeleyDB, and lightweight, and has nice Ruby bindings--Perl, not so hot.
Some people claim it's more stable than Berkeley. There's an impressive set of benchmarks here:
http://tokyocabinet.sourceforge.net/benchmark.pdf
This should be compared with Oracle's benchmarks:
http://www.oracle.com/technology/products/berkeley-db/pdf/berkeley-db-perf.pdf
which shows bulk read of 5,000,000 records/sec. "un de ces" indeed.

Berkeley has more features, Tokyo might be faster, we'd probably want to test both of them out at scale to see how they hold up. Tokyo is designed to do cloud-style partitioning and stuff.

We also might want to look at Project Voldemort, which runs LinkedIn:
http://project-voldemort.com/
This one keeps its database in-memory, and has really sophisticated protocols for distributed hash tables, load balancing, consistency, etc.

Lots to think about indeed. And he sent along a little script as an example to tinker with, which I won't post here....

Thanks, Richard.

Conventional versus electron flow

The nice thing about standards is that there are so many of them to choose from.

Having a couple of motorcycles means that I also own a couple of battery chargers. During the winter, you need to keep them charged when not riding, since letting them go completely flat wrecks the battery. Even during riding season, the combination of big engines, small batteries, and periods when one does not ride much, you can don the helmet and leathers, stride confidently to the machine of choice, and get .... nothing. I was charging the 'buza's battery the other day, and asked the simple question: "which way does electricity flow"? Sure, in a DC system, electricity flows from the positive (red) to the negative (black) posts. That's odd. Why would negatively charged electrons move from the positive to the negative? Shouldn't they move from negative to positive? The amount of misinformation on the Internet regarding this simple question is staggering. Thankfully, Andrew Tanenbaum provides the answer in his discussion of "Conventional versus electron flow" in the very helpful All About Circuits site.

There are two ways to consider the direction of electricity flow, which are pretty much contradictory. The "conventional" view, where electricity flows from positive to negative, dates back to Franklin. He detected flow and assumed that there was a surplus of charge (hence positive) on one pole and a lack of charge on the other (hence negative). Of course, many years later, it was found that the true flow of electrons was the opposite, from negative to positive.

By the time the true direction of electron flow was discovered, the nomenclature of "positive" and "negative" had already been so well established in the scientific community that no effort was made to change it, although calling electrons "positive" would make more sense in referring to "excess" charge. You see, the terms "positive" and "negative" are human inventions, and as such have no absolute meaning beyond our own conventions of language and scientific description. Franklin could have just as easily referred to a surplus of charge as "black" and a deficiency as "white," in which case scientists would speak of electrons having a "white" charge (assuming the same incorrect conjecture of charge position between wax and wool).

However, because we tend to associate the word "positive" with "surplus" and "negative" with "deficiency," the standard label for electron charge does seem backward. Because of this, many engineers decided to retain the old concept of electricity with "positive" referring to a surplus of charge, and label charge flow (current) accordingly. This became known as conventional flow notation

He goes on to discuss the distinction in useful detail, concluding

I sometimes wonder if it would all be much easier if we went back to the source of the confusion -- Ben Franklin's errant conjecture -- and fixed the problem there, calling electrons "positive" and protons "negative."

Mystery resolved. Now, if I can only figure out how to get light bulbs out of sockets on ceiling fan/light systems without breaking them, I will be forever grateful. The vibration of the fan tends to wedge them in pretty tightly.....

Projekt DeutschDiachronDigital

Alain suggests that Projekt DeutschDiachronDigital is involved in some interesting efforts that might be related to some work we are doing. There are a number of useful papers on the project's publication list, including

Lukas C. Faulstich, Ulf Leser und Anke Lüdeling. Storing and Querying Historical Texts in a Relational Database. Informatik-Bericht Nr.176 des Instituts für Informatik der Humboldt-Universität zu Berlin, Februar 2005

Lukas C. Faulstich, Ulf Leser und Thorsten Vitt. Implementing a Linguistic Query Language for Historic Texts. Query Languages and Query Processing (QLQP-2006): 11th Intl. Workshop on Foundations of Models and Languages for Data and Objects (FMLDO), 2006.

Interesting to see they are using SQL to power this project.