2007-04-30 Workshop on Software Trends 1

The Antikythera Mechanism on the OLPC

Diomidis SpinellisAssociate ProfessorInformation Systems Technology LaboratoryAthens University of Economics and Businesshttp://www.dmst.aueb.gr/dds

2007-04-30 Workshop on Software Trends 2

Overview

Overview of the Antikythera MechanismOLPC initiativeOLPC platformSqueak and EToysEToys implementation

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Antikythera Mechanism

Discovered 1900Dated 150-100 B.C.At least 35 gearsAstronomical calculatorStudies

D. de Solla Price (1960)Nature (2006)

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Front Dial Function

Sun Zodiac positionMoon Zodiac position (anomalistic month)Moon phase

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Front Dial

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Luni-Solar Calendar

Meton29 ½ day synodic month19 seasonal years contain almost 235 synodic months

Callipuscycle containing 125 full months of 30 days 110 hollow, 29 day, months

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Eclipse Prediction

Saros cycle223 ⅓ synodic months

ExeligmosThree Saros cycles

Software engineeringLookup tableDesign pattern for increasing the resolution

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Back Dial

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Educational Context

AstronomyArithmeticGeometryMechanical engineeringPhysicsArcheologyComputer scienceScience

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One Laptop per Child

Computers are toolsImagine a writing lab…Build an affordable machine tailored to childrenOLPC as an enabler

Learn by doingExperimentCommunicate and collaborateAccess knowledge

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Platform Overview

SturdyNo hard diskSpill proof keyboard

Thrifty on power consumptionSize, weight, form suitable for children1200×900 screen readable under the sunlightBook modeMesh networkingI/O for experiments

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Software Overview

LinuxX11Sugar

Web browserPaintWriteSlideshowCameraTam-tamSqueak EToys

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Squeak

Smalltalk in the 21st

centuryRe-implementation of Smalltalk in SmalltalkVM-basedRuns bit-identical images on any platform

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EToys

Visual programming environmentBuilt on top of SqueakSuitable for

building learning activitieslearning by doing

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Basic Idea

One interface mechanismAvailable everywhereControlling everything

No distinction between producers and consumers

Children can explore and change what they’re seeing

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A Simple Example

Let’s draw a flag

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Processing

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A Student’s Toolbox

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Programming

Everything is an objectAll objects have similar propertiesWe can modify properties by direct manipulationProgramming is the changing of properties

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EToys Context

EToys lacks sophisticated data structuresmathematical functionsbitmap drawing primitives

Use facilities that children can understandAvoid

trigonometryvectorscalculus

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Polygons

Add a sideIncrement the Χ and Υ coordinatesAdd a sideIncrement Χ, decrement ΥRotate

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Calculating with Gears

Gear A: 24 teethGear B: 16 teethRatio: 24/16 = 3/2

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Functional Decomposition

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Gear Placement

NorthSouthEastWestcoCenter

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Gear Movement

Concentric: maintain headingEngaged: rotate if overlapping

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Example: Luni-Solar Calendar

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Eclipse Prediction

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Sidereal Month

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Hipparchos’s Mechanism

Reuse

Reuse

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Tens of Other Applications

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Contact Details

Diomidis Spinellishttp://www.dmst.aueb.gr/dds

dds@aueb.grhttp://www.dmst.aueb.gr/dds/sw/ameso

http://www.laptop.org