text:
Talk:Artificial Intelligence

This is the discussion area for the Artificial Intelligence Wikibook. This book is intended as a central AI book, into which all other AI content will be merged (with exception of wikiversity articles and study guides). Please create a new title for a new area of discussion and please sign your comments with ~.

Current AI Content
There are currently two wikibooks on AI that can be merged into this one, once the layout is decided on. These are:

 * Computer Programming/AI (redirects here now)
 * Computer Science:Artificial Intelligence

Some other wiki(books) content on AI:

 * Artificial Intelligence Study Guide
 * Cyberbotics' Robot Curriculum/What is Artificial Intelligence?

Wikibooks content on more specific AI topics:

 * Artificial Neural Networks
 * Expert Systems

Some wikibooks and chapters on related fields:

 * Cognitive Psychology and Cognitive Neuroscience
 * Introduction to Philosophy/Philosophy of Mind
 * Lisp Programming
 * Prolog
 * Robotics

Outside of Wikibooks:

 * Artificial intelligence: wikipedia article
 * w:Portal:Artificial intelligence: wikipedia portal
 * AI Textbook survey, compares contents of several introductory AI textbooks
 * Out of date, but still a very good introduction to AI is the Dover book, Introduction to Artificial Intelligence by Philip C. Jackson Jr.here

(feel free to add any content you find to these lists)

Policy
Artificial Intelligence/How you can help is our WB:LMOS.

Layout
AI is a rather large field (especially considering its age) so dividing it into small easily digestible chapters takes some effort. The basic idea, I think, should not be to create a book that needs to be read from start to finish. If this book is ever going to be used in the classroom (or other learning environments) people will need to be able to pick and choose according to their interests or curriculum. Chapters should therefore be as much standalone as possible, and required knowledge should be described clearly (both in terms of previous chapters and other knowledge (such as a basic grasp of programming structures or familiarity with Linear Mathematics).

I think the basics of AI can be divided into around seven areas (like logic, machine learning, language etc.) To allow us to go into the more complicated areas as well (such as reinforcement learning or advanced neural models), I propose to set up a 'tiered' system.

The first section would describe basic techniques and knowledge (such as logic and state space search ), that can be read in any order and serve as required knowledge for the rest of the book. This section should have some simple examples of how to use the techniques for AI (to make it a little less dry), but it should basically serve to explain just the techniques.

Section two would describe the various subfields of Artificial Intelligence, based on the content of the first section (how predicate logic is used natural language processing and knowledge engineering, how state space searches are used in gameplay and nlp etc.) The reader is assumed to be familiar with the stuff from the first section.

Section three would expand on section two, to expand on certain narrow fields, like Neural Networks. The Machine Learning chapter from section two would touch on Neural Networks, but the chapter in section three would be an extensive description of all techniques

Section four would serve to describe the very latest techniques, that borrow from different fields of AI, or very specific subjects that have developed their own body of knowledge and techniques (such as Machine Vision).

(Note that the word chapter in this regard is rather arbitrary. Each of these chapters could (and hopefully will) grow to the size of a book in it's own right and will certainly need to be subdivided itself)

An (incomplete) example layout would be:
 * Introduction: An overview and an explanation of the field, to let the reader know what she's getting into. Includes some philosophy, history and future.

Section 1
 * Logic: Describing the basics of proposition logic and predicate logic.
 * Search: Decribing the basic idea of state space searches and search algorithms.

Section 2
 * Planning, Decision making and Problem Solving: From the towers of Hanoi puzzle to a (simplified) autonomous shopping agent.
 * Uncertainty: Introduction to reasoning, planning and decision making with uncertainty.
 * Machine Learning: The basic ideas and algorithms.
 * Natural Language: Stuff like Markov models and CFG's.
 * Knowledge engineering: Ways to describe and store complicated knowledge. Databases, OO concepts, knowledge bases, etc.

Section 3
 * Neural Networks and related models
 * Bayesian Networks
 * Inference in Logic: Backward and Forward chaining, Resolution and Logic Programming.

Section 4
 * Machine Vision
 * Speech Recognition, Text to Speech and OCR
 * Advanced Logics
 * Advanced NLP and NLG techniques: A description of the various techniques for dealing with tenses, sentence focus, presuppositions, etc.
 * Reinforcement Learning
 * Robotics''

Please commment and criticize freely. No layout will be perfect and this is certainly not the only possibility. risk 17:00, 29 December 2005 (UTC)

 * I really think that the first section should include the basics of probability theory and inference (of which logic is a special case) estimation and optimisation (with state space search being a special case). To section 3 I'd add Probabilistic Inference: The junction tree algorithm. In section 4, reinforcemnet learning is more a basic research field than an application field, so it should have its own section - perhaps a chapter on sequential decision making would it fit it very well, together with planning.Olethros

Subjects
I think it would be good to simply think of any subject that would fall into the field of AI, anything from Logic to Neural Networks in Reinforcement Learning. Just write down anything you can think of. It will give us an idea of what we're dealing with here and for anything that doesn't fit into the layout, we'll have to find a solution. risk 17:00, 29 December 2005 (UTC)
 * I'm a beginner in AI, so no way can i help out with this book... although here are some subjects I'm interested in

--Dragontamer 06:36, 30 December 2005 (UTC)
 * Many thanks for the input. Don't be so sure you can't help. I'm not saying it wouldn't be nice to have some experts contributing, but I always figure that the people that are actually learning from a wiki can help it the most. They're the readers that know how things should be explained. risk 00:19, 31 December 2005 (UTC)
 * In addition the hierarchy of this list is also open for change.

--Moxon 21:13, 30 December 2005 (UTC)
 * Good point. However, feel free to ignore the hierarchy and just add subjects to the bottom of the list. Other people will fit them into the list in their proper place (if possible). risk 00:19, 31 December 2005 (UTC)

 * AI approaches:
 * mathematics - soft computing
 * computer science - machine learning
 * mechanics - cybernetics (robotics)
 * biology - artificial life
 * psychology - cognitive science
 * phylosophy - logic, neats vs. scruffies etc.

 * expert systems
 * Bayesian networks
 * case based reasoning
 * Cognitive Models
 * Bases in Mathematics. Trig, statistics, a base to build a model upon. ???

 * neural networks
 * multi-layer perseptron
 * radial basis network
 * self-organising map
 * adaptive resonance theory network
 * recurrent neural network
 * Hopfield network
 * echo state network
 * instantaniously trained neural network
 * support vector machines

 * fuzzy logic
 * fuzzification
 * inference
 * Sugeno type
 * Mamdani type
 * Tsukamoto type
 * defuzzification
 * singleton
 * centriod
 * clustering techniques
 * nearest neighbor
 * k-mean
 * mountain clustering
 * growing neural gas
 * evolving classifier functions

 * evolutionary computation
 * evolutionary algorithms
 * evolutionary strategies
 * genetic algorithms
 * cultural algorithms
 * evolutionary programming
 * genetic programming
 * learning classifier systems
 * swarm intelligence
 * particle swarm optimization
 * ant colony optinization (ant-algorithms)
 * simulated annealing
 * artificial immune systems

 * hybrid intelligent systems
 * fuzzy clustering
 * adaptive neuro-fuzzy inference system (as used by Matlab)
 * genetic fuzzy systems
 * Michigan approach
 * Pitsburg approach
 * Incremetal approach
 * evolving connectionist systems (DENFIS, EFuNN, ESOM)

 * intelligent agents
 * software agents (bots)
 * multi-agents
 * reinforcement learning
 * dynamic programming
 * Monte Carlo method
 * temporal difference
 * emergent robotics
 * epigenetic robotics
 * cognitive robotics
 * developmental robotics
 * evolutionary robotics

 * Games with AI
 * Tic-Tac-Toe
 * Chess
 * shooting games, strategy games, path finding techniques:
 * ant algorithms
 * a* (a-star) algorithm
 * d* (d-star) algorithm
 * robocode
 * game of life

 * artificial life (a-life)
 * emergence
 * chaos theory
 * fractal theory (not sure it this can be considered as AI)

 * machine learning (alternative categorization)
 * supervised learning
 * gradient based methods (hill descent, backpropagation, etc.)
 * unsupervised learning
 * clustering methods
 * reinforcement learning

 * Applications(alternative categorization)
 * classifiers
 * controllers
 * optimizers

 * Basic Programming techniques (or another wikibook could be started for these subjects) - I think so, Moxon
 * Finite State Machines
 * Function pointers
 * Interpreters/Compilers
 * Functional programming

Layout Themes
With so much added to that last list, I think we need to rethink the layouts from scratch again, so here are some of my ideas.

How to do xxxx with AI
For example, chapter one would be "How to make a perfect Tic-tac-toe AI", chapter two would be "How to make a strong chess AI". Maybe they can be organized in themes like this:

 * Trees
 * List of requirements to understand section, with references to other wikibooks. Ex. This chapter would list "understands basic binary trees and searching techniques, such as depth-first and breadth first".
 * How to make a perfect Tic-tac-toe AI
 * Add other ways to make tic-tac-toe AIs, neural networks, genetic algorithms, whatever.
 * How to make a strong chess AI
 * Ditto.
 * Learning / pattern matching
 * List of requirements
 * How to make a program predict where you hid the ball. (basic game, 2 "cups" on the screen, user clicks one, an AI predicts where you would place it in advance.)
 * Other methods to complete this.
 * etc. etc.

The emphasis on this kind of book would be practicality, every AI technique would have a use. Advantages would be that students could skip around to whatever section they wanted, and editors/teachers can work on any section they want. It would be easy to split the work, and easy for someone to split their learning path to whatever they want. --Dragontamer 04:12, 31 December 2005 (UTC)

 * I like the idea, but I don't think it's going to work for the whole book. So many subjects (especially the basics) can be explained best 'bottom up', explaining the ideas and methods behind it, before starting to explain their uses. Take, for example, predicate logic. It's used pretty much everywhere in AI and should be one of the first chapters in any AI book, but I'd have a hard time thinking of a simple application that shows it's power. My main AI textbook tries to explain the uses of predicate logic (in planning systems) by trying to solve/play a simple game with it. Unfortunately, the game can be solved quite easily with some common sense programming, where predicate logic pretty much fails miserably, leaving the reader to wonder exactly what the point of the chapter (and predicate logic) was. Of course if you simply explain predicate logic bottom up and let the reader get a feel for it, the reader will see for herself what the advantages and disadvatages of predicate logic are (and begin to understand its importance). There are many AI techniques that, though useful, don't have a very specific use that explains why they're useful. Once you understand them it's easy to see why it's very helpful to understand them, but it's actually quite difficult to give a simple example of what you can do with them.

 * I can see where you're coming from, of course. Learning endless logic systems and dull algorithms without anybody explaining (or showing) what they're for an how powerful they can be, will deter even the most motivated student. So I think it'll be very important to keep the students aware of what they can achieve with the stuff they're learning (where possible), using (real world) examples and simple assignments. I also think we can use the 'how to do xxxx with AI' in the setting of a (more or less) conventional textbook. If we create regular chapters that follow a bottom up approach, but make them as modular as possible (if at all possible you should be able to read them on their own, if there's other required knowledge, it should be described at the start of the chapter), we could turn the 'how to do xxxx with AI' into special case study chapters, to tie some of the other chapters together. For instance, a case study on a strong poker AI could refer back use the gameplay chapter, the reasoning with uncertainty chapter as well as chapters on statistics and reinforcement learning. A case study of diagnosis systems could use the chapter on predicate logic, knowledge engineering and perhaps uncertainty. That way, teachers could simply follow the course of the main chapters, to make sure their students get a comprehensive overview of the field, and people learning stuff by themselves, start with a case study, and read up on the required knowledge for as far as they care to. The main function for these chapters would be to make the material come alive, so interesting and exciting subjects should be chosen (so much for the diagnosis system :). I'll try to think up some of the more juicy AI systems (at least int my opinion), and add them to the list. risk 02:37, 3 January 2006 (UTC)

 * We would need a variety of games too. Poker is a popular game, but not one that I'm very much interested in. (by all means though, put it in the book. The popularity of poker today is massive). Perhaps we should make a list of games that an AI should be able to solve? --Dragontamer 02:47, 3 January 2006 (UTC)

 * Dragontamer, bear in mind that in AI the possible problems are infinite, but there is a set of tools being used over and over to solve them, whether it is "How to make a strong chess AI" or "How to control a nuclear power plant". If you can solve the poker problem you can pretty much use the same technique to solve the chess problem. When new techniques are derived (e.g. swarm intelligence) it can be applied to almost all problems, but with various levels of success. It is much more efficient to just add a chapter covering a new technique, rather than revisiting and editing all the problems discussed. It is your job as AI expert to find the technique best suited for the problem at hand. You might not know them all, but the techniqes are categorised, and you should know where to start looking.

 * However, similar problems tend to favour certain types of techniques e.g. for discrete n-person games, geometrical object recognition, robotic motion control etc, so you can focus on a class of problems and the category of techniques most likely to hold the optimal solution, but sometimes a better/simpler solution can be found somewhere else quite unexpectedly. I addition most real life problems implement combinations and hybrids of techniques, making the possible solutions endless. --Moxon 18:35, 5 January 2006 (UTC)

Hi, I have started a wikibook on Knowledge Engineering for Historians and would like to keep in touch with you guys because that may or may not cut down on the explaining of knowledge engineering that I have to do. Also, you might want to cross link at appropriate points to my stuff. Coverage is going to be driven by what I currently work on, but if you need a specific knowledge engineering examples at any point, let me know and maybe we can help each other out. Thanx and good luck, --rck 17:05, 26 February 2006 (UTC)

Lesson -- Lesson -- Application layout
With that done, here is another Layout Idea. Simple really.

 * Lesson
 * Lesson
 * Chapter dedicated to application
 * Lesson
 * Lesson
 * Chapter on applications (can be on first 2 lessons as well)

Basically, modified version of the "how to do this" layout, with some more space for theory. --Dragontamer 02:54, 3 January 2006 (UTC)
 * Yep, that's exactly what I was thinking (fast response, btw). I forgot to mention that these case studies would of course be a far cry from the paragraph of light reading you get in a lot of textbooks (especially math) where they show very quickly how the material is used in real life, to make it a little less dry. I would like these chapters to be comprehensive studies of the subject. For instance, the chapter on chess AI's should pretty allow the reader to build a chess AI herself (which may actually be a project). risk 03:06, 3 January 2006 (UTC)

Giant program layout
I'm not sure if this could work out in AI, but it was done very well in Ivor Horton's "Beginning Java 2". What he did was create a problem at the beginning of the book, and then chapter by chapter after about chapter 10, he would start building a program to solve this problem. Beginning Java Objects also did this with a different problem and solution.

Layout:
 * Introduction and theory (5-10 chapters or so for intro...)
 * State a problem (For Beginning Java 2, it was "build a paint clone")
 * Chapter Lesson
 * Application to the problem
 * Lesson
 * Application to the problem
 * Lesson
 * etc. etc.

--Dragontamer 02:54, 3 January 2006 (UTC)

 * Well, in a way this is what AI is. We've got a problem (we want artificial intelligence) and every chapter should get us a little closer to the solution. On a more preactical note, I think this approach might work well for some subjects and not so well for others. We could take a single problem (like a poker AI), and go at it from different angles, but if we do that in the theory chapters we'll lose modularity (you would have to read how the logic chapter dealt with the problem to understand what the machine learning chapter was referring to), we'd pretty much be forcing people to read the chapters in a certain order. The case study chapters are actually a great solution to this; show the reader different approaches to a problem after she's read the chapters. However, since our chapters are going to be pretty big (at least in ambition, any chapter covering all its subject matter would be a small book in its own right), this approach might work for certain single chapters. Take one simple problem and keep using it to explain the subject matter of the subchapters. Since the subchapters won't have to be as modular, the approach would work better on this level. I think would have to be decided chapter by chapter, but it's definitely something to keep in mind. risk 03:18, 3 January 2006 (UTC)

Add your theme here
Just a stub, so anyone else with an idea, just tack it on like this message.

 * Artificial Life: I think this would make a great 'case study'. It's always been one of the most exciting AI subjects to me, but in three years of studying AI, it's only come up once, as a novelty. It's not something that's taken very seriously in academic circles, but I think it's one of the subjects that really illustrates how cool AI can be (and it's visual too). It draws mainly on machine learning techniques, with perhaps some reinforcement learning. risk
 * Data Mining: Doing some basic data mining on a large (real life) data set. I actually did this on a project, and it taught me a lot about how machine learning works in practical situations. We could actually provide a dataset (maybe something from the wikipedia servers) and show how to answer questions about it, using neural networks, decision trees, stuff like that. Everything from cleaning the data, running algorithms (Weka would probably be good for this), and interpreting the results. risk
 * Dialogue Systems: How to beat the turing test. :) In the end, this is still the holy grail of AI's. It would be nice study cbr systems like ALICE that are pretty much the closest we've come so far and what techniques might actually pass the test. Stuff like systems that translate everything into some expanded logic (and back) and other solutions that AI researchers like to fantasize about. risk

Statisics
Something on statistics should be placed in here. I've played "robocode" before, and neural networks, pattern matching, and so forth were all beaten by a simple statistical analysis of the enemy. --Dragontamer 15:51, 29 December 2005 (UTC)

Neural networks and pattern matching are, or should be, applied statistics. I think that the first chapter should be a background chapter, talking about: logic, search, optimisation, probability theory and inference. These are enough for describing any field of AI I think. --Olethros 12:09, 8 January 2006 (UTC)

Categorization
Good luck with your initiative Risk, I hope you can manage to create a feasible structure and merge the sources. On the Artificial_intelligence talk page there is a discussion on categorization and refactoring of the wikipedia page. The notion of categorizing according to applications rather than techniques is discussed. It might be worth while to read those ideas. Either way I think this task is next to impossible.

Sectioning as described in the schools of thought section, in the wikipedia pages, is becoming all the more difficult with so many hybrid systems developed. Another problem is the definition of terminology such as machine learning (any adaptive system can technically be considered as part of ML), and reinforcement learning (any AI technique can be applied to achieve this). Note that the IEEE Computational Intelligence Society divides the subject under Neural networks, Fuzzy systems & Evolutionary computation.

In addition to pseudo code I think browser ready scripts would also be cool. A philosophical section would also be nice. And how about a sections with new ideas and news?

I will also add some subjects to the uncategorised list above. Dragontamer please forgive me for chopping your message. Risk, maybe you should move it to the module page – maybe some index structure could self-emerge from this :-) If I went into to much detail, forgive me and remove it. (I can get a bit carried away since I've recently written up a literature study on the subject) --Moxon 21:13, 30 December 2005 (UTC)

 * Wow, great stuff, thanks. I'll try to fit all these subjects into the current layout to see how it holds up. I'll no doubt have to shift things about a bit. Of course, there's quite a difference between the perfect categorization of AI subjects and the perfect way to set up an AI textbook (although I don't think either goal is completely attainable). For instance, Machine Learning might be a very inefficient category, (since so many systems fall under it) but it's a chapter that (imo) no AI textbook should be without (because it shows very important techniques and design philosophies). Still, it's good to have a thought out list like this to see that all subjects will fit into the layout.

 * I like the other ideas too. A section for recent AI ideas and activity is a great idea (to give the reader an idea of where the action is). Most of my AI textbooks are only five years old and starting to get out of date already. Browsers script and applets would be a cool extra, but I'm not sure if wikimedia would allow that kind of code. I suppose we'll figure something out when (and if) we reach that point. risk 00:00, 31 December 2005 (UTC)

Categorization 2
I've started compiling all the ideas from this page into a layout on the article page. I haven't incorporated everything yet, (all the topics under subjects need to be checked to see if they can (or need to) be incorporated). Discuss it here. risk 14:55, 16 February 2006 (UTC)

Outlining AI
I am sorry to add to the mess here. I do not agree with the current direction. Headings like "Section 2: Basic AI topics" and "Section 3: More advanced topics and techniques" add to the confusion, albeit I appreciate the efforts that has been done.Connection 13:54, 7 March 2006 (UTC)

We should set "Applications of AI" and "Application Areas" apart. For example Robotics is an Application Area where AI is used. Expert Systems (the topic) is an Application of AI, where AI tools are used. Neural Networks are an Application of AI.Connection 13:54, 7 March 2006 (UTC)

Areas of Application where a body of knowledge has been developed separate of the area itself (like Computational Linguistics in NLP) has its specific Constructs. They need a special term. For example, "Application Constructs" may be used, pending a better name. This heading covers "Stuff like Markov models, POS taggers and CFG's", Semantic Nets, ... Connection 13:54, 7 March 2006 (UTC)

AI Application Constructs are in turn served by AI Constructs (again, pending a better name). These are Predicate Logic, Heuristic Modeling, ... Connection 13:54, 7 March 2006 (UTC)

Finally, "AI Tools" are formal systems used to implement and to assist in devlepoment AI Applications. This should cover Programming Languages (Lisp, Prolog), OO Implementations, ... This Book Section covers Techniques and "How to", and provides Program source code.Connection 13:54, 7 March 2006 (UTC)

This Layered Approach leads to the following Outline (currently at First Level): Connection 13:54, 7 March 2006 (UTC)

 * Overview

 * Background (introduces concepts needed to understand Constructs: Probability, ...)

 * Constructs

 * Application Constructs

 * Applications of AI

 * Application Areas

 * AI Tools

I can't understand this
I don't get what this book is about, reading above it seems like you people are going through every step to create an AI individually however since nobody created a really good AI, i.e. human intelligence, you can't give a step by step instruction since there are many completely different ways that head in different directions that didn't produce any better results than the other, e.g. artificial neural networks, genetic algorithms, heuristic probability search, etc. I hope you understand my concerns. 80.109.79.136 13:19, 27 April 2007 (UTC)

 * (Apologies for the necropost, but it's not very active around here.) I'm not quite sure where you get that impression apart from the one suggestion above ("Giant program layout"), which was shot down for the same reasons you gave. This book would be a broad introduction to AI concepts. --Mrwojo (talk) 01:31, 1 January 2009 (UTC)

Prerequisite: Discrete mathematics
I added the Discrete mathematics prerequisite because I'd expect it to cover the "review" aspects of the first section as it's currently listed (propositional logic, searching, probability). (Examples: (Chapters 1, 6, 10), [http://www.pearsonhighered.com/academic/product/0,3110,0130652474,00.html (Ch. 2, 7, 9)].) We might want to point people specifically to Formal Logic for first-order logic. This would help trim the scope of this book to its specific topic. --Mrwojo (talk) 04:18, 5 January 2009 (UTC)

Outline 1
Let me repost the only outline that has so far been presented, from the above section "Subjects". Posting further outlines, as extensive as this one, is a way to make sure all the content is convered and well organized. --Dan Polansky (talk) 14:22, 9 March 2009 (UTC)

 * AI approaches:
 * mathematics - soft computing
 * computer science - machine learning
 * mechanics - cybernetics (robotics)
 * biology - artificial life
 * psychology - cognitive science
 * phylosophy - logic, neats vs. scruffies etc.

 * expert systems
 * Bayesian networks
 * case based reasoning
 * Cognitive Models
 * Bases in Mathematics. Trig, statistics, a base to build a model upon. ???

 * neural networks
 * multi-layer perseptron
 * radial basis network
 * self-organising map
 * adaptive resonance theory network
 * recurrent neural network
 * Hopfield network
 * echo state network
 * instantaniously trained neural network
 * support vector machines

 * fuzzy logic
 * fuzzification
 * inference
 * Sugeno type
 * Mamdani type
 * Tsukamoto type
 * defuzzification
 * singleton
 * centriod
 * clustering techniques
 * nearest neighbor
 * k-mean
 * mountain clustering
 * growing neural gas
 * evolving classifier functions

 * evolutionary computation
 * evolutionary algorithms
 * evolutionary strategies
 * genetic algorithms
 * cultural algorithms
 * evolutionary programming
 * genetic programming
 * learning classifier systems
 * swarm intelligence
 * particle swarm optimization
 * ant colony optinization (ant-algorithms)
 * simulated annealing
 * artificial immune systems

 * hybrid intelligent systems
 * fuzzy clustering
 * adaptive neuro-fuzzy inference system (as used by Matlab)
 * genetic fuzzy systems
 * Michigan approach
 * Pitsburg approach
 * Incremetal approach
 * evolving connectionist systems (DENFIS, EFuNN, ESOM)

 * intelligent agents
 * software agents (bots)
 * multi-agents
 * reinforcement learning
 * dynamic programming
 * Monte Carlo method
 * temporal difference
 * emergent robotics
 * epigenetic robotics
 * cognitive robotics
 * developmental robotics
 * evolutionary robotics

 * Games with AI
 * Tic-Tac-Toe
 * Chess
 * shooting games, strategy games, path finding techniques:
 * ant algorithms
 * a* (a-star) algorithm
 * d* (d-star) algorithm
 * robocode
 * game of life

 * artificial life (a-life)
 * emergence
 * chaos theory
 * fractal theory (not sure it this can be considered as AI)

 * machine learning (alternative categorization)
 * supervised learning
 * gradient based methods (hill descent, backpropagation, etc.)
 * unsupervised learning
 * clustering methods
 * reinforcement learning

 * Applications(alternative categorization)
 * classifiers
 * controllers
 * optimizers

 * Basic Programming techniques (or another wikibook could be started for these subjects) - I think so, Moxon
 * Finite State Machines
 * Function pointers
 * Interpreters/Compilers
 * Functional programming

Outline 2
Here goas another outline, reposted from the section Layout above. However, the sections in this outline have no titles. --Dan Polansky (talk) 14:24, 9 March 2009 (UTC)
 * Section 1
 * Logic: Describing the basics of proposition logic and predicate logic.
 * Search: Decribing the basic idea of state space searches and search algorithms.
 * Section 2
 * Planning, Decision making and Problem Solving: From the towers of Hanoi puzzle to a (simplified) autonomous shopping agent.
 * Uncertainty: Introduction to reasoning, planning and decision making with uncertainty.
 * Machine Learning: The basic ideas and algorithms.
 * Natural Language: Stuff like Markov models and CFG's.
 * Knowledge engineering: Ways to describe and store complicated knowledge. Databases, OO concepts, knowledge bases, etc.
 * Section 3
 * Neural Networks and related models
 * Bayesian Networks
 * Inference in Logic: Backward and Forward chaining, Resolution and Logic Programming.
 * Section 4
 * Machine Vision
 * Speech Recognition, Text to Speech and OCR
 * Advanced Logics
 * Advanced NLP and NLG techniques: A description of the various techniques for dealing with tenses, sentence focus, presuppositions, etc.
 * Reinforcement Learning
 * Robotics

Orphan

 * Artificial Intelligence/Symbolic Programming -- Adrignola talk contribs 14:35, 17 May 2010 (UTC)

title: Talk:Artificial Intelligence


text:
Use the Source/OpenSolaris

Sun Microsystems started as a project at a university, the Stanford University Network. Its acronym, SUN, became representative of a company that provided computer hardware and software, especially for servers.

Sun also invented the Java programming language. The Java technology attracted much interest from the community of programmers. Many users wanted to create Java applets. A web browser with Java support would display interactive Java programs in web pages.

Java instead found more use at the server. There are several languages to script web servers, including Perl, Python, and PHP, but many owners of servers preferred Java and the backing of Sun Microsystems. Businesses spoke of "Java" much and the demand for servers with Java 2 Enterprise Edition was high. With Java at the web server, there was no need for clients to upgrade their computers or install Java.

To handle large amounts of data, a web server with Java needed a back-end database. A Sun server running Solaris was one way to host such a database.

But then, between years 2000 and 2005, came change. Many persons stopped saying "Java" and started saying "Linux". Businesses started looking for Linux products instead of Java products. Many GNU/Linux distributions provided functionality equal to Solaris. Commercial vendors of database software started providing it for Linux in addition to Solaris. IBM and the United States government became interested with Linux and wrote kernel code for Linux. Servers migrated from Solaris to Linux, which ended their need to pay Solaris licenses. Because Linux is free, licensing is gratis; Linux source code is public and several companies sell support for it.

Sun, which had dropped support for Java at the Macintosh platform, added the Linux platform, bringing the number of Java platforms to three. However, many users became interested in "LAMP".

LAMP refers to Linux the kernel, Apache the web server, MySQL the database. These are all free, and can all be called Free Software and Open Source, except possibly Apache, for which some users have reservations. But Apache source code, like Linux kernel code and MySQL code, is public without a licensing fee. The "P" of LAMP refers to Perl, PHP, or Python, but never Java. The P-languages are all free, but Java is not.

LAMP asked servers to consider switching from Solaris and other platforms to Linux. Sun wanted to answer "No". Sun wanted to exploit some advantages that Solaris retained versus Linux and LAMP.

Thus, Sun drafted the "Common Development and Distribution License", a generalised version of the Mozilla Public License. The Open Source Initiative approved the CDDL license; thus any programme with a CDDL license is now Open Source. Then Sun decided to gradually apply the CDDL license to Solaris code to create a free operating system called OpenSolaris.

Some welcomed OpenSolaris. Some even wanted to create a type of GNU/OpenSolaris, by taking the GNU Compiler Collection and other common tools from the Linux platform and using them to fill gaps in OpenSolaris.

But certain persons warned that the CDDL license was incompatible with the dominant GNU General Public License. For example, code from a CDDL-ed programme cannot be placed into the Linux kernel. They began discouraging the use of CDDL-licensed code.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Use the Source/OpenSolaris


text:
Special Relativity/Simultaneity, time dilation and length contraction

More about the relativity of simultaneity
Most physical theories assume that it is possible to synchronise clocks. If you set up an array of synchronised clocks over a volume of space and take a snapshot of all of them simultaneously, you will find that the one closest to you will appear to show a later time than the others, due to the time light needs to travel from each of the distant clocks towards you. However, if the correct clock positions are known, by taking the transmission time of light into account, one can easily compensate for the differences and synchronise the clocks properly. The possibility of truly synchronising clocks exists because the speed of light is constant and this constant velocity can be used in the synchronisation process (the use of the predictable delays when light is used for synchronising clocks is known as "Einstein synchronisation").

The Lorentz transformation for time compares the readings of synchronised clocks at any instant. It compares the actual readings on clocks allowing for any time delay due to transmitting information between observers and answers the question "what does the other observer's clock actually read now, at this moment". The answer to this question is shocking. The Lorentz transformation for time shows that the clocks in any frame of reference moving relative to you cease to be synchronised!

The desynchronisation between relatively moving observers is illustrated below with a simpler diagram:

The effect of the relativity of simultaneity is for each observer to consider that a different set of events is simultaneous. The relativistic phase difference between clocks ("relativistic phase") means that observers who are moving relative to each other have different sets of things that are simultaneous, or in their "present moment". It is this discovery that time is no longer absolute that profoundly unsettles many students of relativity.

The amount by which the clocks differ between two observers depends upon the distance of the clock from the observer ($$t = xv/c^2 $$). Notice that if both observers are part of inertial frames of reference with clocks that are synchronised at every point in space then the phase difference can be obtained by simply reading the difference between the clocks at the distant point and clocks at the origin. This difference will have the same value for both observers.

Example: flashing lights

Two lights that are stationary with respect to each other are separated by 3000 metres. The lights flash one after another with a time interval of 4 microseconds between the flashes. How fast would you need to travel along the line of the lights to see the lights flashing simultaneously?

This problem is a straightforward example of relativistic phase, events that are simultaneous for a moving observer being successive events in their own frame of reference. The phase difference between clocks with distance is given by:

$$\Delta t = vx/c^2$$

So $$v = \Delta tc^2/x$$

Dividing by $$c$$ to express $$v$$ as a fraction of the speed of light gives:

$$v_c = \Delta tc/x$$

Therefore: $$ v_c = \frac{4 \times 10^{-6} \times 3 \times 10^8}{3 \times 10^3} $$

Thus $$v_c = 0.4 c$$

(See the "explosion" example in Scherr et al. (2001))

Discuss the relationship between the times that a stationary and a moving observer will assign to the flashes in the example: the Lorentz transformation for the time of an event is $$t' = \gamma (t - vx/c^2)$$, it is composed of an elapsed time, $$t$$ and a phase difference, $$vx/c^2$$. The flashing lights example is arranged so that $$t = t' = 0$$ when the observers in the two inertial frames of reference pass each other at the first flash and so that $$t = t$$ and $$t' = 0$$ is the time of the second flash.

If $$t' = 0$$ then $$0 = \gamma (t - vx/c^2)$$ so, according to the Lorentz transformation the moving observer finds events to be simultaneous in the stationary inertial reference frame when $$t = vx/c^2$$, ie: when the elapsed time in the stationary frame is equal to the phase difference between the frames.

Scherr, R.E., Shaffer, P.S. and Vokos, S. Student understanding of time in special relativity: simultaneity and reference frames. Physics Education Research, American Journal of Physics Supplement, 69, S24-35 (2001)

Example: Relativistic Bug Capture
How fast would a 1000 m long spaceship need to travel to observe a nanosecond difference between stationary clocks aligned with its bow and stern?

From $$t = xv/c^2 $$:

$$10^{-9} = 10^3 v/(9 \times 10^{16}) $$

Therefore $$v = 9 \times 10^4 ms^{-1}$$ or 90 km per second.

This effect could be used to bring together bugs of different ages that are twins in their own inertial frame of reference:

Bill travels past Jim in a very long spaceship and simultaneously captures two bugs, one coincident with the bow of the spaceship and one coincident with the stern. Although the bugs are twins in their own frame of reference they are different ages in Bill's reference frame. The captured bugs are free to wander up and down Bill's spaceship and could meet each other.

What length of spaceship travelling at 90 km per second would be needed to capture the bugs in the picture?

The Andromeda Paradox
What do we mean when we say that events are occurring "now"? If we are looking out over a cityscape, watching the traffic, lots of things appear to be happening all at once. We can take a snapshot with a camera and the scene on the photo consists of all those things that happened at very nearly the same time. They are only "very nearly" at the same time because the events on the photo that were furthest away actually occurred slightly earlier than those that were nearby because of the time taken for light to reach the camera. If we want to discover the events that really happened at the same time we would need to subtract the time taken for the light to get to us. This would be highly necessary if you were observing events on the Moon: if you were on the Earth and saw the time on a lunar clock you would know that the real time on the moon was more than a second later. But would this be enough? What about the relativistic phase differences between clocks due to motion?

Special Relativity introduces yet another factor, in addition to the travel time of light, that upsets our knowledge of which events are simultaneous. The relativistic phase differences between clocks are tiny at the distance of the moon but have the startling consequence that at distances as large as our separation from nearby galaxies an observer who is driving on the earth can have a radically different set of events that are simultaneous with her "present moment" from another person who is standing on the earth. The classic example of this effect of relativistic phase is the "Andromeda Paradox", also known as the "Rietdijk-Putnam-Penrose" argument. Penrose described the argument:

"Two people pass each other on the street; and according to one of the two people, an Andromedean space fleet has already set off on its journey, while to the other, the decision as to whether or not the journey will actually take place has not yet been made. How can there still be some uncertainty as to the outcome of that decision? If to either person the decision has already been made, then surely there cannot be any uncertainty. The launching of the space fleet is an inevitability." (Penrose 1989).

The argument is illustrated below:

Notice that neither observer can actually "see" what is happening on Andromeda now. The argument is not about what can be "seen", it is purely about what different observers consider to be contained in their instantaneous present moment. The two observers observe the same, two million year old events in their telescopes but the moving observer must assume that events at the present moment on Andromeda are a day or two in advance of those in the present moment of the stationary observer. (Incidentally, the two observers see the same events in their telescopes because length contraction of the distance from Earth to Andromeda compensates exactly for the time difference on Andromeda.)

This "paradox" has generated considerable philosophical debate on the nature of time and free-will. The advanced text of this book provides a discussion of some of the issues surrounding this geometrical interpretation of special relativity.

A result of the relativity of simultaneity is that if the car driver launches a space rocket towards the Andromeda galaxy it might have a several days head start compared with a space rocket launched from the ground. This is because the "present moment" for the moving car driver is progressively advanced with distance compared with the present moment on the ground. The present moment for the car driver is shown in the illustration below:

The net effect of the Andromeda paradox is that when someone is moving towards a distant point there are later events at that point than for someone who is not moving towards the distant point. There is a time gap between the events in the present moment of the two people.

The twin paradox
The "Twin Paradox" derives from an article by Langevin (1911) who used travel to a distant star and back to describe the relationships between times in different inertial reference frames. Langevin's original example was called the "Clock Paradox" and showed that a space traveller who travels to a distant star and back finds that he has aged less than the people who stay on Earth. Benguigui (2012) provides a detailed account of how, over time, this example became the story of two twins, one who travels out into space and one who stays at home, and how it became described by Weyl in 1922 as the "Twin Paradox". The "Twin Paradox" is an interesting example of the relativity of simultaneity and time dilation and deserves close study so that these features of Special Relativity can be understood. However, be warned, the reason that the "twin paradox" has attracted so much puzzlement is that, although superficially a simple problem, the analysis of the various inertial frames of reference is complex.

A one way trip
The twin "paradox" consists of two journeys, an outbound journey and a return journey. Much can be learnt about the relativity of simultaneity by considering just the outbound journey without any return. The single journey without any return might consist of the following scenario: Jim stays at home on Earth and Bill goes off in a spaceship, Bill flies past Jim at a velocity of 0.8c, they both set all of their clocks to zero as they pass each other and Bill flies straight to Mars where he drops off a record of his clock reading. Jim, who stays on Earth, finds that Bill's clocks record less time than his own for the journey.

The journey to Mars consists of two inertial frames of reference. In Jim's frame of reference Bill is moving and Jim is stationary. In Bill's frame of reference Jim, Earth and Mars move and Bill is stationary. There are only two reference frames so questions such as "what does Jim observe if he considers himself to be moving" are equivalent to asking "how does Jim move in Bill's frame of reference?".

The start of the journey is shown below:

Suppose for ease of calculation Mars is assumed to be 100 light seconds away from Earth. Jim's view of the journey is straightforward and is shown below:

If Mars is 100 light seconds away, Jim will time Bill's journey to take 125 seconds ($$100/0.8$$). Relativistic time dilation will cause Bill's clocks to read 75 seconds ie:

Bill's clocks will read: $$125/\gamma $$

where gamma is: $$\frac{1}{\sqrt{1-\frac{v^2}{c^2}}} = 1.667$$

so $$ 125/1.6667 = 75$$ seconds.

In Jim's inertial frame of reference Jim has aged by 125 seconds when Bill gets to Mars but Bill, as a result of time dilation, has only aged by 75 seconds.

The reason that this lack of aging by Bill seems to be paradoxical is that it might be thought that Jim must also have aged less than Bill, after all, Jim travels away from Bill as much as Bill travels away from Jim so Bill should find Jim to have aged less than himself in the same way as Jim finds Bill to have aged less than himself. In fact there is no paradox because Bill and Jim have very different ideas of the journey. Bill's view of the journey is shown below.

As a result of relativistic phase, Bill finds that the clocks on Mars start the journey 80 seconds ahead of his own. The Martian clocks record another 45 seconds for the journey. The 45 seconds elapsed time for the journey is what Bill expects when time dilation is taken into account (ie: $$75/\gamma = 75/1.6667 = 45$$ seconds). More surprising still, when Bill considers Jim's clock readings back on Earth he finds that only 45 seconds have elapsed on Jim's earth-based clocks during the journey because the 80 seconds of relativistic phase difference mean that Bill's clocks as he passes Mars are simultaneous with events on Earth that are only 45 seconds later than when he passed Earth.

If Bill had an absurdly long rocket he could use a version of "relativistic bug capture" (see above) to net one of Jim's clocks the moment Bill reaches Mars. Bill could then show there was a Jim on Earth whose clocks had only progressed by 45 seconds for Bill's journey in Bill's inertial frame of reference. If Bill had captured one of Jim's clocks, the Jim who is simultaneous in his own frame of reference with the moment that Bill passes Mars would remember a giant net coming down from the tail of a spaceship and taking one of his clocks 45 seconds after Bill passed him.

Notice that there are two Jims in this story, one who is simultaneous with the Mars that Bill visits and another who is simultaneous with Bill in Bill's frame of reference. The Jim who is simultaneous with Bill in Bill's frame of reference would be an earlier Jim than the Jim who is simultaneous in his own frame of reference with Mars when Bill arrives.

The one way journey is symmetrical in the sense that Jim observes Bill to age less than himself during the journey and Bill also observes an earlier Jim to have aged less than himself.

The one way journey would become fully symmetrical if Bill continued past Mars until his clocks read that 125 seconds had elapsed, at this point he would assess that Jim had experienced 75 seconds of elapsed time. When Jim's clock's read 125 seconds Jim finds Bill's clocks read 75 seconds and, symmetrically, when Bill's clocks read 125 seconds Bill finds that Jim's clocks read 75 seconds. This symmetry is emphasised in the schematic diagram below which compares Jim and Bill's clock readings:

What happens when there is a change of velocity?
In the previous section it was shown that time dilation is symmetrical when observers separate at a constant velocity. The symmetry is evident in the way that, during the one way journey, Jim observes Bill's clocks to go slow and Bill also observes Jim's clocks to go slow. The symmetry between the observers means that Bill can regard himself as stationary and observing Jim departing or vice versa.

Bill finds that there are two Jims at two separate times involved in going to Mars then suddenly changing direction to return to Earth: these are labelled A and C in the diagram. The first Jim has clocks that read 45 seconds since Bill passed Earth, this is the Jim who is simultaneous with Bill in Bill's frame of reference as Bill passes Mars. The second Jim has clocks that read 205 seconds since meeting Bill, this Jim is simultaneous with Bill, in Bill's frame of reference, the moment after he has turned around at Mars and reached a velocity of -0.8c for the return journey.

The lack of any single Jim that is simultaneous with Bill when Bill changes velocity introduces an asymmetry into Special Relativity. Bill turning around at Mars to come back to Earth is not equivalent to Earth turning to meet Bill because it is not clear, until Bill has made the turn, which Earth and which Jim is making the journey. Langevin (1911), who first proposed the example of a traveller departing and returning younger, was well aware of the asymmetry and stated that: "Thus the asymmetry – which occurred because only the traveler, in the middle of his journey, has undergone an acceleration that changes the direction of his velocity".

In Special Relativity the laws of physics are the same for each observer in an inertial frame of reference. An inertial frame of reference might be all the clocks and measuring rods in a room on board a ship or in an entire city, the crucial feature of an inertial reference frame being that the clocks and measuring rods are stationary with respect to each other. Motions are measured so that the rest of the universe moves relative to the observer's inertial frame of reference. There are three inertial frames of reference in the example of Bill going to Mars and returning to Earth: Jim, outbound Bill and inbound Bill. Outbound and inbound Bill are separated by a period of varying velocity when Bill turns around. This period of changing velocity can also be regarded as a non-inertial hiatus in Bill's single inertial reference frame after which the relations between Bill's clocks and measuring rods and those in the rest of the universe have changed.

Questions such as "how does the Jim who is simultaneous with Bill after the turn view events if he regards himself as moving towards Bill?" are really about the inbound Bill's reference frame. In Jim's own inertial frame of reference Bill just goes to Mars, turns round and comes back again. Jim always regards himself as stationary unless his reference frame becomes non-inertial by experiencing a change in velocity in which case Jim would regard himself as moving from one stationary state to another that has a different set of relationships with the universe. Special Relativity holds that the laws of physics are the same in all inertial reference frames, it does not hold that all motion is relative, even in non-inertial changes.

The gap in time between the Jim who is simultaneous with Bill as Bill reaches Mars and the Jim who is simultaneous with Bill as he starts the journey back to Earth is known as the "Time Gap". The time gap in the "twin paradox" consists of the sum of the outgoing and incoming phase differences and in this case the time gap is 160 seconds.

The time gap description of the "twin paradox"
Once it is accepted that Bill and Jim have very different views of the journey these views can be summarised in the "Time Gap" description of the journey. In this description Bill flies to Mars and discovers that the clocks there are reading a later time than his own clock. He turns round to fly back to Earth and realises that the relativity of simultaneity means that, for Bill, the clocks on Earth will have jumped forward and are ahead of those on Mars, yet another "time gap" appears. When Bill gets back to Earth the time gaps and time dilations mean that people on Earth have recorded more clock ticks that he did.

For ease of calculation suppose that Bill is moving at a truly astonishing velocity of 0.8c in the direction of a distant point that is 100 light seconds away (about 30 million kilometres). The illustration below shows Jim and Bill's observations:

From Bill's viewpoint there is both a time dilation and a phase effect. It is the added factor of "phase" that explains why, although the time dilation occurs for both observers, Bill observes the same readings on Jim's clocks over the whole journey as does Jim.

To summarise the mathematics of the twin paradox using the example:

Jim observes the distance as 100 light seconds and the distant point is in his frame of reference. According to Jim it takes Bill the following time to make the journey:

 * Time taken = distance / velocity therefore according to Jim:

 * $$t = 100/0.8 = 125$$ seconds

 * Again according to Jim, time dilation should affect the observed time on Bill's clocks:

 * $$T = t \times \sqrt {1 - v^2/c^2}$$ so:

 * $$T = 125 \times \sqrt {1 - 0.8^2} = 75$$ seconds

So for Jim the round trip takes 250 secs and Bill's clock reads 150 secs.

Bill measures the distance as:

 * $$X = x \times \sqrt {1 - v^2/c^2} = 100 \times \sqrt {1 - 0.8^2} = 60$$ light seconds.

 * For Bill it takes $$X/v = 60/0.8 = 75 $$ seconds.

Bill observes Jim's clocks to appear to run slow as a result of time dilation:

 * $$t^' = T \times \sqrt {1 - v^2/c^2}$$ so:

 * $$t^' = 75 \times \sqrt {1 - 0.8^2} = 45$$ seconds

But there is also a time gap of $$vx/c^2 = 80 $$ seconds.

So for Bill, Jim's clocks register 125 secs have passed from the start to the distant point. This is composed of 45 secs elapsing on Jim's clocks at the turn round point plus an 80 secs time gap from the start of the journey. Bill sees 250 secs total time recorded on Jim's clocks over the whole journey, this is the same time as Jim observes on his own clocks.

Further reading:

Benguigui, L (2012). A tale of two twins. arXiv:1212.4414v1

Bohm, D. The Special Theory of Relativity (W. A. Benjamin, 1965).

D’Inverno, R. Introducing Einstein’s Relativity (Oxford University Press, 1992).

Eagle, A. A note on Dolby and Gull on radar time and the twin "paradox". American Journal of Physics. 2005, VOL 73; NUMB 10, pages 976-978. http://arxiv.org/PS_cache/physics/pdf/0411/0411008v2.pdf

Langevin, P. (1911) L'Evolution de l'espace et du temps Scientia 10 (1911), 31-34

The nature of length contraction
According to special relativity items such as measuring rods consist of events distributed in space and time and a three dimensional rod is the events that compose the rod at a single instant. However, from the relativity of simultaneity it is evident that two observers in relative motion will have different sets of events that are present at a given instant. This means that two observers moving relative to each other will usually be observing measuring rods that are composed of different sets of events. If the word "rod" means the three dimensional form of the object called a rod then these two observers in relative motion observe different rods.

The way that measuring rods differ between observers can be seen by using a Minkowski diagram. The area of a Minkowski diagram that corresponds to all of the events that compose an object over a period of time is known as the worldtube of the object. It can be seen in the image below that length contraction is the result of individual observers having different sections of an object's worldtube in their present instant.

(It should be recalled that the longest lengths on space-time diagrams are often the shortest in reality).

It is sometimes said that length contraction occurs because objects rotate into the time axis. This is actually a half truth, there is no actual rotation of a three dimensional rod, instead the observed three dimensional slice of a four dimensional rod is changed which makes it appear as if the rod has rotated into the time axis. In special relativity it is not the rod that rotates into time, it is the observer's slice of the worldtube of the rod that rotates.

There can be no doubt that the three dimensional slice of the worldtube of a rod does indeed have different lengths for relatively moving observers. The issue of whether or not the events that compose the worldtube of the rod are always existent is a matter for philosophical speculation.

Further reading:

[http://philsci-archive.pitt.edu/archive/00002408/ Vesselin Petkov. (2005) Is There an Alternative to the Block Universe View?]

[http://arxiv.org/abs/1005.4623 Dragan V Redžić (2010). Relativistic length agony continued]

More about time dilation
The term "time dilation" is applied to the way that observers who are moving relative to you record fewer clock ticks between events than you. In special relativity this is not due to properties of the clocks, such as their mechanisms getting heavier. Indeed, it should not even be said that the clocks tick faster or slower because what is truly occurring is that the clocks record shorter or longer elapsed times and this recording of elapsed time is independent of the mechanism of the clocks. The differences between clock readings are due to the clocks traversing shorter or longer distances between events along an observer's path through spacetime. This can be seen most clearly by re-examining the Andromeda Paradox.

Suppose Bill passes Jim at high velocity on the way to Mars. Jim has previously synchronised the clocks on Mars with his Earth clocks but for Bill the Martian clocks read times well in advance of Jim's. This means that Bill has a head start because his present instant contains what Jim considers to be the Martian future. Jim observes that Bill travels through both space and time and expresses this observation by saying that Bill's clocks recorded fewer ticks than his own. Bill achieves this strange time travel by having what Jim considers to be the future of distant objects in his present moment. Bill is literally travelling into future parts of Jim's frame of reference.

In special relativity time dilation and length contraction are not material effects, they are physical effects due to travel within a four dimensional spacetime. The mechanisms of the clocks and the structures of measuring rods are irrelevant.

It is important for advanced students to be aware that special relativity and General Relativity differ about the nature of spacetime. General Relativity, in the form championed by Einstein, avoids the idea of extended space and time and is what is known as a "relationalist" theory of physics. Special relativity, on the other hand, is a theory where extended spacetime is pre-eminent. The brilliant flowering of physical theory in the early twentieth century has tended to obscure this difference because, within a decade, special relativity had been subsumed within General Relativity. The interpretation of special relativity that is presented here should be learnt before advancing to more advanced interpretations.

The Pole-barn paradox
The length contraction in relativity is symmetrical. When two observers in relative motion pass each other they both measure a contraction of length.

(Note that Minkowski's metric involves the subtraction of displacements in time, so what appear to be the longest lengths on a 2D sheet of paper are often the shortest lengths in a (3+1)D reality).

The symmetry of length contraction leads to two questions. Firstly, how can a succession of events be observed as simultaneous events by another observer? This question led to the concept of de Broglie waves and quantum theory. Secondly, if a rod is simultaneously between two points in one frame how can it be observed as being successively between those points in another frame? For instance, if a pole enters a building at high speed how can one observer find it is fully within the building and another find that the two ends of the rod are opposed to the two ends of the building at successive times? What happens if the rod hits the end of the building? The second question is known as the "pole-barn paradox" or "ladder paradox".

The pole-barn paradox states the following: suppose a superhero running at 0.75c and carrying a horizontal pole 15 m long towards a barn 10m long, with front and rear doors. When the runner and the pole are inside the barn, a ground observer closes and then opens both doors (by remote control) so that the runner and pole are momentarily captured inside the barn and then proceed to exit the barn from the back door.

One may be surprised to see a 15-m pole fit inside a 10-m barn. But the pole is in motion with respect to the ground observer, who measures the pole to be contracted to a length of 9.9 m (check using equations).

The “paradox” arises when we consider the runner’s point of view. The runner sees the barn contracted to 6.6 m. Because the pole is in the rest frame of the runner, the runner measures it to have its proper length of 15 m. Now, how can our superhero make it safely through the barn?

The resolution of the “paradox” lies in the relativity of simultaneity. The closing of the two doors is measured to be simultaneous by the ground observer. However, since the doors are at different positions, the runner says that they do not close simultaneously. The rear door closes and then opens first, allowing the leading edge of the pole to exit. The front door of the barn does not close until the trailing edge of the pole passes by.

What happens if the rear door is kept closed and made out of some impenetrable material? Can we or can we not trap the rod inside the barn by closing the front door while the whole rod is inside according to a ground observer? When the front end of the rod hits the rear door, information about this impact will travel backwards along the rod in the form of a shock wave. The information cannot travel faster than c, so the rear end of the rod will continue to travel forward at its original speed until the wave reaches it. Even if the shock wave is traveling at the speed of light, it will not reach the rear end of the rod until after the rear end has passed through the front door even in the runner's frame. Therefore the whole rod (albeit quite scrunched up) will be inside the barn when the front door closes. If it is infinitely elastic, it will end up compressed and "spring loaded" against the inside of the closed barn.

Evidence for length contraction, the field of an infinite straight current
Length contraction can be directly observed in the field of an infinitely straight current. This is shown in the illustration below.

Non-relativistic electromagnetism describes the electric field due to a charge using:

$$E = \frac{\lambda}{2 \pi \epsilon_0 r}$$

and describes the magnetic field due to an infinitely long straight current using the Biot Savart law:

$$B = \frac{\mu_0 I}{2 \pi r}$$

Or using the charge density (from $$I = \lambda v$$ where $$\lambda$$ is the amount of charges per unit length):

$$B = \frac{\mu_0 \lambda v}{2 \pi r}$$

Using relativity it is possible to show that the formula for the magnetic field given above can be derived using the relativistic effect of length contraction on the electric field and so what we call the "magnetic" field can be understood as relativistic observations of a single phenomenon. The relativistic calculation is given below.

If Jim is moving relative to the wire at the same velocity as the negative charges he sees the wire contracted relative to Bill:

$$l_+ = l \sqrt{1 - v^2/c^2}$$

Bill should see the space between the charges that are moving along the wire to be contracted by the same amount but the requirement for electrical neutrality means that the moving charges will be spread out to match those in the frame of the fixed charges in the wire.

This means that Jim sees the negative charges spread out so that:

$$l_- = \frac{l}{\sqrt{1 - v^2/c^2}}$$

The net charge density observed by Jim is:

$$\lambda = \frac{q}{l_-} - \frac{q}{l_+}$$

Substituting:

$$\lambda = \frac{q}{l} ( \sqrt{1 - v^2/c^2} - \frac{1}{\sqrt{1 - v^2/c^2}})$$

Using the binomial expansion:

$$\lambda = \frac{q}{l} (1 - \frac{v^2}{2c^2} - 1 - \frac{v^2}{2c^2})$$

Therefore, allowing for a net positive charge, the positive charges being fixed:

$$\lambda = \frac{qv^2}{l c^2}$$

The electric field at Jim's position is given by:

$$E = \frac{\lambda v^2}{2 \pi \epsilon_0 r c^2}$$

The force due to the electrical field at Jim's position is given by $$F = Eq$$ which is:

$$F = \frac{q \lambda v^2}{2 \pi \epsilon_0 r c^2}$$

Now, from classical electromagnetism:

$$c^2 = \frac{1}{\epsilon_0 \mu_0}$$

So substituting this into $$F = \frac{q \lambda v^2}{2 \pi \epsilon_0 r c^2}$$:

(1) $$F = \frac{q\mu_0 \lambda v^2}{2 \pi r}$$

This is the formula for the relativistic electric force that is observed by Bill as a magnetic force. How does this compare with the non-relativistic calculation of the magnetic force? The force on a charge at Jim's position due to the magnetic field is, from the classical formula:

$$F = Bqv$$

Which from the Biot-Savart law is:

(2) $$F = \frac{q\mu_0 \lambda v^2}{2 \pi r}$$

which shows that the same formula applies for the relativistic excess electrical force experienced by Jim as the formula for the classical magnetic force.

It can be seen that once the idea of space-time is understood the unification of the two fields is straightforward. Jim is moving relative to the wire at the same speed as the negatively charged current carriers so Jim only experiences an electric field. Bill is stationary relative to the wire and observes that the charges in the wire are balanced whereas Jim observes an imbalance of charge. Bill assigns the attraction between Jim and the current carriers to a "magnetic field".

It is important to notice that, in common with the explanation of length contraction given above, the events that constitute the stream of negative charges for Jim are not the same events as constitute the stream of negative charges for Bill. Bill and Jim's negative charges occupy different moments in time.

Incidently, the drift velocity of electrons in a wire is about a millimetre per second but a huge charge is available in a wire (See link below).

Further reading:

Purcell, E. M. Electricity and Magnetism. Berkeley Physics Course. Vol. 2. 2nd ed. New York, NY: McGraw-Hill. 1984. ISBN: 0070049084.

Useful links:

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/ohmmic.html

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/releng.html

De Broglie waves
De Broglie noticed that the differing three dimensional sections of the universe would cause oscillations in the rest frame of an observer to appear as wave trains in the rest frame of observers who are moving.

He combined this insight with Einstein's ideas on the quantisation of energy to create the foundations of quantum theory. De Broglie's insight is also a round-about proof of the description of length contraction given above - observers in relative motion have differing three dimensional slices of a four dimensional universe. The existence of matter waves is direct experimental evidence of the relativity of simultaneity.

Further reading: de Broglie, L. (1925) On the theory of quanta. A translation of : RECHERCHES SUR LA THEORIE DES QUANTA (Ann. de Phys., 10e s´erie, t. III (Janvier-F ´evrier 1925).by: A. F. Kracklauer. http://replay.web.archive.org/20090509012910/http://www.ensmp.fr/aflb/LDB-oeuvres/De_Broglie_Kracklauer.pdf

Bell's spaceship paradox
Bell devised a thought experiment called the "Spaceship Paradox" to enquire whether length contraction involved a force and whether this contraction was a contraction of space. In the Spaceship Paradox two spaceships are connected by a thin, stiff string and are both equally and linearly accelerated to a velocity $$v$$ relative to the ground, at which, in the special relativity version of the paradox, the acceleration ceases. The acceleration on both spaceships is arranged to be equal according to ground observers so, according to observers on the ground, the spaceships will stay the same distance apart. It is asked whether the string would break.

It is useful when considering this problem to investigate what happens to a single spaceship. If a spaceship that has rear thrusters is accelerated linearly, according to ground observers, to a velocity $$v$$ then the ground observers will observe it to have contracted in the direction of motion. The acceleration experienced by the front of the spaceship will have been slightly less than the acceleration experienced by the rear of the spaceship during contraction and then would suddenly reach a high value, equalising the front and rear velocities, once the rear acceleration and increasing contraction had ceased. From the ground it would be observed that overall the acceleration at the rear could be linear but the acceleration at the front would be non-linear.

In Bell's thought experiment both spaceships are artificially constrained to have constant acceleration, according to the ground observers, until the acceleration ceases. Sudden adjustments are not allowed. Furthermore no difference between the accelerations at the front and rear of the assembly are permitted so any tendency towards contraction would need to be borne as tension and extension in the string.

The most interesting part of the paradox is what happens to the space between the ships. From the ground the spaceships will stay the same distance apart (the experiment is arranged to achieve this) whilst according to observers on the spaceships they will appear to become increasingly separated. This implies that acceleration is not invariant between reference frames (see Part II) and the force applied to the spaceships will indeed be affected by the difference in separation of the ships observed by each frame.

The section on the nature of length contraction above shows that as the string changes velocity the observers on the ground observe a changing set of events that compose the string. These new events define a string that is shorter than the original. This means that the string will indeed attempt to contract as observed from the ground and will be drawn out under tension as observed from the spaceships. If the string were unable to bear the extension and tension in the moving frame or the tension in the rest frame it would break.

Another interesting aspect of Bell's Spaceship Paradox is that in the inertial frames of the ships, owing to the relativity of simultaneity, the lead spaceship will always be moving slightly faster than the rear spaceship so the spaceship-string system does not form a true inertial frame of reference until the acceleration ceases in the frames of reference of both ships. The asynchrony of the cessation of acceleration shows that the lead ship reaches the final velocity before the rear ship in the frame of reference of either ship. However, this time difference is very slight (less than the time taken for an influence to travel down the string at the speed of light $$x/c > vx/c^2 $$).

It is necessary at this stage to give a warning about extrapolating special relativity into the domain of general relativity (GR). SR cannot be applied with confidence to accelerating systems which is why the comments above have been confined to qualitative observations.

Further reading

Bell, J. S. (1976). Speakable and unspeakable in quantum mechanics. Cambridge University Press 1987 ISBN 0-521-52338-9

Hsu, J-P and Suzuki, N. (2005) Extended Lorentz Transformations for Accelerated Frames and the Solution of the “Two-Spaceship Paradox” AAPPS Bulletin October 2005 p.17 http://www.aapps.org/archive/bulletin/vol15/15-5/15_5_p17p21%7F.pdf

Matsuda, T and Kinoshita, A (2004. A Paradox of Two Space Ships in Special Relativity. AAPPS Bulletin February 2004 p3. http://www.aapps.org/archive/bulletin/vol14/14_1/14_1_p03p07.pdf

The transverse doppler effect
The existence of time dilation means that the frequency of light emitted from a source that is moving towards or away from an observer should be red shifted in directions that are perpendicular to the direction of motion. The transverse doppler effect is given by:

 * $$\nu = \nu^{\prime} \sqrt{ 1 - \frac{v^2}{c^2}}$$

Where $$\nu$$ is the observed frequency and $$\nu^{\prime}$$ is the frequency if the source were stationary relative to the observer (the proper frequency).

This effect was first confirmed by Ives and Stillwell in 1938. The transverse doppler effect is a purely relativistic effect and has been used as an example of proof that time dilation occurs.

Relativistic transformation of angles
If a rod makes an angle with its direction of motion toward or away from an observer the component of its length in the direction of motion will be contracted. This means that observed angles are also transformed during changes of frames of reference. Assuming that motion occurs along the x-axis, suppose the rod has a proper length (rest length) of $$L^{\prime}$$ metres and makes an angle of $$\theta^{\prime}$$degrees with the x'-axis in its rest frame. The tangent of the angle made with the axes is:

 * Tangent in rest frame of rod = $$\tan \theta^{\prime} = \frac{L^{\prime}_y}{L^{\prime}_x}$$

 * Tangent in observer's frame = $$\tan \theta = \frac{L_y}{L_x}$$

 * Therefore:

 * $$\frac {\tan \theta}{\tan \theta^{\prime}} = \frac {L_y L^{\prime}_x} {L^{\prime}_y L_x}$$

 * But $$L_x = L^{\prime}_x \sqrt {1 - v^2/c^2}$$

 * And $$L_y = L^{\prime}_y$$

 * So

 * $$\tan \theta =\frac {\tan \theta^{\prime}} {\sqrt {1 - v^2/c^2}}$$

Showing that angles with the direction of motion are observed to increase with velocity.

The angle made by a moving object with the x-axis also involves a transformation of velocities to calculate the correct angle of incidence.

Addition of velocities
How can two observers, moving at v m/sec relative to each other, compare their observations of the velocity of a third object?

Suppose one of the observers measures the velocity of the object as $$u^'$$ where:

$$u^' = \frac{x^'}{t^'}$$

The coordinates $$x^'$$ and $$t^'$$ are given by the Lorentz transformations:

$$x^' = \frac{x - vt}{\sqrt{(1 - v^2/c^2)}}$$

and

$$t^' = \frac{t - (v/c^2)x}{\sqrt{(1 - v^2/c^2)}}$$

but

$$x^' = u^' t^'$$

so:

$$\frac{x - vt}{\sqrt{(1 - v^2/c^2)}} = u^' \frac{t - (v/c^2)x}{\sqrt{(1 - v^2/c^2)}}$$

and hence:

$$x - vt = u^' ( t - vx/c^2)$$

Notice the role of the phase term $$vx/c^2$$. The equation can be rearranged as:

$$x = \frac{(u^' + v)}{(1 + u^'v/c^2)} t$$

given that $$x = u t$$:

$$u = \frac{(u^' + v)}{(1 + u^'v/c^2)}$$

This is known as the relativistic velocity addition theorem, it applies to velocities parallel to the direction of mutual motion.

The existence of time dilation means that even when objects are moving perpendicular to the direction of motion there is a discrepancy between the velocities reported for an object by observers who are moving relative to each other. If there is any component of velocity in the x direction ($${u_x} $$, $${{u^'}_x}$$) then the phase affects time measurement and hence the velocities perpendicular to the x-axis. The table below summarises the relativistic addition of velocities in the various directions in space.

Notice that for an observer in another reference frame the sum of two velocities (u and v) can never exceed the speed of light. This means that the speed of light is the maximum velocity in any frame of reference.


text:
Speech-Language Pathology/Parkinson's

A survey of Parkinson's patients found that

 27% reported "difficulty getting started." 9% reported "stuttering." 9% reported "fast speech." 9% reported "impaired stress of rhythm of speech."

The speech disorder associated with Parkinson's disease is also characterized by low volume and poor articulation. The combination sounds like mumbling. The standard treatment for Parkinson's speech is Lee Silverman Voice Therapy. LSVT focuses on increasing vocal volume, largely through consciously increasing airflow and vocal fold activity. A secondary benefit is improved articulation or vocal clarity.

Studies found varying results of DAF with Parkinson's patients.

References

 * 1) Blanchet, Paul. "Treating Fluency and Speech Rate Disorders in Individuals with Parkinson's Disease: The Use of Delayed Auditory Feedback (DAF)," Journal of Stuttering Therapy, Advocacy and Research, Volume 1, Number 2.
 * 2) Blanchet, Paul. "Treating Fluency and Speech Rate Disorders in Individuals with Parkinson's Disease: The Use of Delayed Auditory Feedback (DAF)," Journal of Stuttering Therapy, Advocacy and Research, Volume 1, Number 2.

title: Speech-Language Pathology/Parkinson's


text:
Special Relativity/Mathematical Appendix

Mathematics of the Lorentz Transformation Equations
Consider two observers $$O$$ and $$O^'$$, moving at velocity $$v \,$$ relative to each other who synchronise their clocks so that $$t=t^'=0$$ as they pass each other. They both observe the same event as a flash of light. How will the coordinates recorded by the observers of the event that produced the light be interrelated?

The relationship between the coordinates can be derived using linear algebra on the basis of the postulates of relativity and an extra homogeneity and isotropy assumption.

The homogeneity and isotropy assumption: space is uniform and homogeneous in all directions. If this were not the case then when comparing lengths between coordinate systems the lengths would depend upon the position of the measurement. For instance, if $$ x^' = a x^2 \,$$ the distance between two points would depend upon position.

The linear equations relating coordinates in the primed and unprimed frames are:

 * $$x^' = a_{11} x + a_{12} y + a_{13} z + a_{14} t \,$$
 * $$y^' = a_{21} x + a_{22} y + a_{23} z + a_{24} t \,$$
 * $$z^' = a_{31} x + a_{32} y + a_{33} z + a_{34} t \,$$
 * $$t^' = a_{41} x + a_{42} y + a_{43} z + a_{44} t \,$$

There is no relative motion in the $$y$$ or $$z$$ directions so, according to the 'relativity' postulate:

 * $$z^' = z \,$$
 * $$y^' = y \,$$

Hence:

 * $$a_{22} = 1 \,$$ and $$a_{21} = a_{23} = a_{24} = 0 \,$$
 * $$a_{33} = 1 \,$$ and $$a_{31} = a_{32} = a_{34} = 0 \,$$

So the following equations remain to be solved:

 * $$x^' = a_{11} x + a_{12} y + a_{13} z + a_{14} t \,$$
 * $$t^' = a_{41} x + a_{42} y + a_{43} z + a_{44} t \,$$

If space is isotropic (the same in all directions) then the motion of clocks should be independent of the y and z axes (otherwise clocks placed symmetrically around the x-axis would appear to disagree). Hence:

 * $$ a_{42} = a_{43} = 0 \,$$

so:

 * $$t^' = a_{41} x + a_{44} t \,$$

Events satisfying $$x^' = 0 \,$$ must also satisfy $$x = vt \,$$. So:

 * $$0 = a_{11} vt + a_{12} y + a_{13} z + a_{14} t \,$$

and

 * $$-a_{11} vt = a_{12} y + a_{13} z + a_{14} t \,$$

Given that the equations are linear then $$a_{12} y + a_{13} z = 0 \,$$ and:

 * $$-a_{11} vt = a_{14} t \,$$

and

 * $$-a_{11} v = a_{14} \,$$

Therefore the correct transformation equation for $$x^' \,$$ is:

 * $$x^' = a_{11} (x - vt) \,$$

The analysis to date gives the following equations:

 * $$x^' = a_{11} (x - vt) \,$$
 * $$y^' = y \,$$
 * $$z^' = z \,$$
 * $$t^' = a_{41} x + a_{44} t \,$$

Assuming that the speed of light is constant, the coordinates of a flash of light that expands as a sphere will satisfy the following equations in each coordinate system:

 * $$x^2 + y^2 + z^2 = c^2t^2 \,$$
 * $$x^{'2} + y^{'2} + z^{'2} = c^2t^{'2} \,$$

Substituting the coordinate transformation equations into the second equation gives:

 * $$a_{11}^2(x - vt)^2 + y^2 + z^2 = c^2(a_{41}x + a_{44}t)^2 \,$$

rearranging:

 * $$(a_{11}^2 - c^2 a_{41}^2)x^2 + y^2 + z^2 - 2(va_{11}^2 + c^2a_{41} a_{44}) xt = (c^2 a_{44}^2 - v^2 a_{11}^2)t^2 \,$$

We demand that this is equivalent with

 * $$x^2 + y^2 + z^2 = c^2t^2 \,$$

So we get:

 * $$ c^2 a_{44}^2 - v^2 a_{11}^2 = c^2 \,$$
 * $$ a_{11}^2 - c^2 a_{41}^2 = 1 \,$$
 * $$va_{11}^2 + c^2a_{41} a_{44} = 0 \,$$

Solving these 3 simultaneous equations gives:

 * $$ a_{44} = \frac{1}{\sqrt{(1 - v^2/c^2)}} \,$$
 * $$ a_{11} = \frac{1}{\sqrt{(1 - v^2/c^2)}} \,$$
 * $$ a_{41} = -\frac{v/c^2}{\sqrt{(1 - v^2/c^2)}} \,$$

Substituting these values into:

 * $$x^' = a_{11} (x - vt) \,$$
 * $$y^' = y \,$$
 * $$z^' = z \,$$
 * $$t^' = a_{41} x + a_{44} t \,$$

gives:

 * $$x^' = \frac{x - vt}{\sqrt{(1 - v^2/c^2)}} \,$$
 * $$y^' = y \,$$
 * $$z^' = z \,$$
 * $$t^' = \frac{t - (v/c^2)x}{\sqrt{(1 - v^2/c^2)}} \,$$

The inverse transformation is:

 * $$x = \frac{x^' + vt^'}{\sqrt{(1 - v^2/c^2)}} \,$$
 * $$y = y^' \,$$
 * $$z = z^' \,$$
 * $$t = \frac{t^' + (v/c^2)x^'}{\sqrt{(1 - v^2/c^2)}} \,$$

Einstein's original approach
How would two observers measure the position and timing of an event by using light rays if the speed of light were constant? The modern analysis of this problem, exposing the assumptions involved, is given above but Einstein's original reasoning (Einstein 1905,1920) is as follows.

Light is transmitted along the positive x axis according to the equation $$x = ct$$ where $$c$$ is the velocity of light. This can be rewritten as:

 * $$x - ct = 0$$

Another observer, moving relatively to the first may find different values for x and t but the same equation will apply:

 * $$x^' - ct^' = 0$$

A simple relationship between these formulae, which apply to the same event is:

 * $$(x^' - ct^') = \lambda (x - ct)$$

Light is transmitted along the negative x axis according to the equation $$x = -ct$$ where $$c$$ is the velocity of light. This can be rewritten as:

 * $$x + ct = 0$$

 * $$x^' + ct^' = 0$$

And:

 * $$(x^' + ct^') = \mu (x + ct)$$

Adding the equations and substituting $$a = \frac{\lambda + \mu}{2}$$ and $$b = \frac{\lambda - \mu}{2}$$:

 * (1) $$x' = ax - bct$$
 * (2) $$ct' = act - bx$$

The origin of one set of coordinates can be set so that $$x^' = 0$$ hence:

 * $$x = \frac{bc}{a} t$$

If $$v$$ is the velocity of one observer relative to the other then $$v = \frac{x}{t}$$ and:

 * (3) $$v = \frac{bc}{a}$$

At $$t = 0$$:

 * (4) $$x^' = ax$$

Therefore two points separated by unit distance in the primed frame of reference ie: when $$x^' = 1$$ have the following separation in the unprimed frame:

 * (5) $$\Delta x = \frac{1}{a}$$

Now $$t$$ can be eliminated from equations (1) and (2) and combined with $$v = \frac{bc}{a}$$ and (4) to give in the case where $$x=1$$ and $$t^' = 0$$:

 * (6) $$x^' = a (1 -\frac{v^2}{c^2}) x$$

And, if $$\Delta x = 1$$:

 * (7) $$\Delta x^' = a (1 -\frac{v^2}{c^2})$$

Now if the two moving systems are identical and the situation is symmetrical a measurement in the unprimed system of a division showing one metre on a measuring rod in the primed system is going to be identical to a measurement in the primed system of a division showing one metre on a measuring rod in the unprimed system. Thus (5) and (7) can be combined so that:

 * $$\frac {1}{a} = a (1 -\frac{v^2}{c^2})$$

So:

 * $$a^2 = \frac {1}{(1 -\frac{v^2}{c^2})}$$

Inserting this value for $$a$$ into equations (1) and (2) and solving for $$b$$ gives:

 * $$ x^' = \frac {x - vt}{\sqrt {1 -\frac{v^2}{c^2}}}$$

 * $$ t^' = \frac {t - (v/c^2)x}{\sqrt {1 -\frac{v^2}{c^2}}}$$

These are the Lorentz Transformation Equations for events on the x axis.

Einstein, A. (1920). Relativity. The Special and General Theory. Methuen & Co Ltd 1920. Written December, 1916. Robert W. Lawson (Authorised translation). http://www.bartleby.com/173/


text:
Talk:MythTV

To the people who assembled this wikibook, thank you!
I once went to a presentation by a friend who made himself a wicked cool little MythTV box in one of those sexy transparent plastic cases, about one cubic foot, and he did a demo of all kinds of wild and fascinating stuff. I got greedy for one, but couldn't find enough knowledge to do it, and ended up with a Tivo (with the lifetime subscription).

I'd be interested to see a comparison of the merits of a MythTV box compared to a Tivo box. What I myself know on the topic is that a MythTV box can do some things a Tivo can't, and the video is in an open format. The Tivo gets commercially supported, which is good and bad; the bad side is that there's a lot of advertising for what studios and broadcasters want me to see, and a bit less emphasis on my own choices. I know MythTV uses XMLTV listings and other stuff. Do you find that gives full coverage of what's available? Are there lapses for some cable TV providers? Just curious.

-- WillWare 18:14, 29 December 2005 (UTC)

 * (Note: I started this wikibook and added the first wave of content.)
 * I hope people are finding this wikibook helpful for setting up their own functional MythTV. Mine is working great and I love it. The fact is (as it says in the wikibook), MythTV can do a LOT more than any commercial offering. The downside is that you have to get your hands dirty sometimes to configure and maintain it. It's been worth it, for me.
 * MythTV is NOT for people who want a "just works" machine. They should get a Tivo. I've heard lots of good things about Tivo, but I'm a control freak. I want to be able to transfer shows to different places. For instance, burning episodes of TV shows to DVD is very useful... or I can transfer them to a laptop for a trip (as far as I know, that's not possible with Tivo).
 * XMLTV has always been pretty accurate for me. I have digital cable, so I get a listing with my cable box (although MythTV has to use XMLTV, the cable company doesn't make it possible to interface with the cable box). Whenver the XMLTV listing is wrong, so is the listing in my cable box... that is, the only problems occur when they change around show times at the last minute (or when sports shows run long, etc.). You can't blame XMLTV or MythTV for that. Again, I emphasize that XMLTV had a full listing for every channel that I get (I'm in Canada, by the way), but obviously it might vary from region to region. This is just my experience.
 * Kebes 19:09, 14 January 2006 (UTC)

Section Split
I'd like to split this book up into sections. Anyone opposed? -Matt 04:52, 8 March 2006 (UTC)
 * Splitting. -Matt 00:05, 16 March 2006 (UTC)

title: Talk:MythTV


text:
User:Bulgaria mitko

Здрасти,

Би ли гласувал за Българската уикикнига също и на Collaboration of the Month/January 2006 voting тъй като са я преместили там. Благодаря ти. --Vanka5 19:28, 29 December 2005 (UTC)

title: User:Bulgaria mitko


text:
User:Rashev~enwikibooks

Здрасти,

Би ли гласувала за Българската уикикнига също и на Collaboration of the Month/January 2006 voting тъй като са я преместили там. Благодаря ти. --Vanka5 19:29, 29 December 2005 (UTC)

title: User:Rashev~enwikibooks


text:
User:Plamendp~enwikibooks

Здрасти,

Би ли гласувал за Българската уикикнига също и на Collaboration of the Month/January 2006 voting тъй като са я преместили там. Благодаря ти. --Vanka5 19:30, 29 December 2005 (UTC)

title: User:Plamendp~enwikibooks


text:
US Constitutional Law

Introduction

 * /Introduction/
 * /The Constitution/
 * /Judicial Review/

Governmental Structure

 * Introduction
 * /Legislative Branch/
 * /Executive Branch/
 * /Judicial Branch/
 * /State Government/

Liberty

 * /Freedom of Religion/
 * /Freedom of Speech/
 * /Freedom of the Press/
 * /Criminal procedural rights/
 * /Privacy Rights/

Equality

 * /Race and Ethnicity/
 * /Sex/
 * /Sexual orientation/

Jurisprudence

 * /Living Constitutionalism/
 * /Originalism/
 * /Textualism /
 * /Strict Constructionism/
 * /Purposive Approach/
 * /Minimalism/

title: US Constitutional Law


text:
User:WillWare~enwikibooks

I think Wikibooks are way cool. It's fascinating to see how many interesting topics have been filled in. This is a great good, maybe in the long run a greater good than Wikipedia.

title: User:WillWare~enwikibooks


text: Template:Previous edit history

title: Template:Previous edit history


text:
Speech-Language Pathology/Stuttering/Overview of the Six Factors that Contribute to Stuttering

The experts each say that one thing causes stuttering. They don't agree what that one thing is, but they all insist that their one thing is the only thing that causes stuttering. And each insists that his therapy program is the only effective treatment for stuttering.

But at least six factors contribute to stuttering. No single stuttering therapy is a "miracle cure." Treating stuttering requires a multifactoral approach—different treatments for each of the six factors:

Developmental Disorder

Stuttering is a developmental disorder. In other words, if you're an adult stutterer, the primary reason that you stutter is that you stuttered as a child. That may seem obvious, but the implications are important, as you'll see in the chapter Childhood Stuttering.

Auditory Processing Underactivity

Brain scans have found that the auditory processing area is underactive during stuttering. It appears that stutterers can't integrate what we hear ourselves saying with how we feel our muscles moving. Electronic altered auditory feedback devices appear to correct this neurological abnormality. This factor is presented in the chapter Auditory Processing.

Speech Motor Control Overactivity

Brain scans have also found that stutterers' speech motor (muscle) control area is overactive. Stutterers overtense their respiration (breathing); vocal folds; and lips, jaws, and tongues (articulators). These overtense muscles lock up or fail to coordinate, making speech impossible. Fluency shaping therapy trains stutterers to speak with relaxed speech production muscles. This factor is presented in the chapter Speech Motor Learning and Control.

Response Selection to Stress

Most stutterers speak fluently when relaxed, but stutter under stress. Personal construct therapy trains stutterers to handle stress in ways that result in fluent speech. This factor is presented in the chapter Response Selection Under Stress.

Genes and Neurotransmitter

Another neurological abnormality associated with stuttering involves too-high levels of the neurotransmitter dopamine in the left caudate nucleus speech motor control area. This appears to contribute to speech motor (muscle) overactivity. Dopamine antagonist medications treat this abnormality. This factor is presented in the chapter Genes and Neurotransmitters.

Psychological Effects

Stuttering causes psychological fears and anxieties. For some individuals, these fears and anxieties are more disabling than their physical stuttering. Some individuals use stuttering as an excuse for deeper problems, such as inability to maintain relationships. Some individuals obsessively try to hide their stuttering, e.g., counterproductively refusing to go to speech therapy for fear that someone may see them entering the speech clinic. These individuals may need treatment with a psychologist in addition to speech therapy. This factor is presented in the chapter Psychological Issues.

Multifactoral Treatment

Most stutterers have one or two factors strongly. The other factors may be less significant. You might find a speech clinic that treats you successfully, especially if the speech clinic combines two or more therapies.

But a speech-language pathologist can treat at most three of the six factors. Electronic devices can treat one or two factors. Medications treat one factor. You may have to go to see several speech-language pathologists, and possibly buy an electronic device or get a medication prescription, to treat all of the factors that contribute to your stuttering.

Additional Factors

I have no doubt that additional stuttering factors will be discovered. Likely other genes contribute to stuttering. The neurotransmitter acetylcholine might play a role.

Some advances in stuttering will be treatments for co-existing conditions. In the future children (and adults) will be tested for a variety of disorders, and treatment designed accordingly. E.g., a child with stuttering and phonological dysfunction will be treated differently than a child with stuttering and ADHD. An adult with stuttering and social phobia will be treated differently from an outgoing mentally retarded adult who stutters.

References

 * 1)  Pharmacist and stutterer Richard Harkness believes: "My long-held hunch, based on my understanding of Parkinson's disease, is that the neurotransmitter acetylcholine (Ach) might be a key player in stuttering. Parkinson's disease is commonly described as a condition of relative imbalance between dopamine (DA) and Ach (low DA/high Ach). Hypothetically at this point, stuttering might be thought of as just the opposite (high DA/low Ach). Research in schizophrenia indicates that a decrease in striatal DA levels is accompanied by an increase in Ach levels. Thus, the tx condition brought about by D2 inhibitors (antipsychotics)—less dopaminergic activity—might result in a relative increase in Ach activity—in effect, could it be that antipsychotic-induced fluency improvement is actually due to increased Ach activity? One problem is that current Ach agonists tend to cause intolerable side effects. But there is ongoing research on Ach agonists/antagonists, primarily for drugs aimed at schizophrenia. There's much more to be learned."

Next: Stuttering Therapy (In)Effectiveness

Back to Table of Contents


text: Talk:Speech-Language Pathology/Stuttering/Childhood Stuttering


text:
User:Fruggo

My userpage on nl.Wikipedia.

title: User:Fruggo