Simulation Content Guide

The table below contains a crude categorization scheme and pointers to simulations in both the NAAP and ClassAction packages. Thumbnails are available if you need to have your memory jogged. In ClassAction look under the Animations tab where simulations are organization by topic. In NAAP the simulations are a mixture of simulations that run in their own Native App windows and a few small ones are actually embedded in a web page. The table reflects a desire to retain the previous organization schemes while effectively pushing both of them together.

TopicTitleClassAction ExecutableNAAP Executable DescriptionThumbnail
Basic Motions & Ancient AstronomySmall-Angle Approximation DemonstratorCA-Basic Motions & Ancient Astronomy Shows how small angles can be approximated.Link
Basic Motions & Ancient AstronomyHeliacal Rising SimulatorCA-Basic Motions & Ancient Astronomy Demonstrates how the day of the year when a star is first visible in the morning (the heliacal rising) depends on the observer's latitude and the star's position on the celestial sphere.Link
Basic Motions & Ancient AstronomyBig Dipper ClockCA-Basic Motions & Ancient Astronomy Shows how stars rotate around the North Star over time (both daily and seasonal motions are shown).Link
Basic Motions & Ancient AstronomyPtolemaic System Simulator NAAP-Solar Systems ModelsDemonstrates how Ptolemy's geocentric model accounts for the movements of the planets.Link
Coordinates and MotionsMeridional Altitude Simulator - 2DCA-Coordinates and Motions Shows the geometry for calculating the meridional altitude of objects.Link
Coordinates and MotionsMeridional Altitude Simulator - 3D NAAP - Motions of the Sun - Meridional Altitude PageShows the geometry in a horizon diagram for calculating the meridional altitude of objects.Link
Coordinates and MotionsDeclination Ranges SimulatorCA-Coordinates and Motions Shows how an observer's latitude determines the circumpolar, rise and set, and never rise regions in the sky.Link
Coordinates and MotionsEcliptic SimulatorCA-Coordinates and Motions Shows how the sun's declination and right ascension change over the course of a year.Link
Coordinates and MotionsUnion Seasons DemonstratorCA-Coordinates and Motions Demonstrates the changing declination of the sun with a time-lapse movie, which shows how the shadow of a building changes over the course of a year.Link
Coordinates and MotionsAzimuth/Altitude DemonstratorCA-Coordinates and Motions Demonstrates the horizon coordinate system, where altitude and azimuth define an object's position in the sky. Link
Coordinates and MotionsDaylight SimulatorCA-Coordinates and Motions Simulation showing daylight and nighttime regions on a flat map of Earth. Daily and yearly motions of the sunlight pattern can be shown.Link
Coordinates and MotionsObliquity SimulatorCA-Coordinates and Motions Shows how obliquity (orbital tilt) is defined.Link
Coordinates and MotionsEcliptic (Zodiac)SimulatorCA-Coordinates and MotionsNAAP - Motions of the SunShows the sun's position in the sky relative to the background stars (the zodiac constellations) over the course of a year.Link
Coordinates and MotionsLongitude/Latitude DemonstratorCA-Coordinates and Motions Demonstrates latitude and longitude with an interactive globe, providing an analogy to the celestial and horizon coordinate systems.Link
Coordinates and MotionsFlat Map Explorer NAAP-Basic Coordinates and SeasonsDemonstrates latitude and longitude on an interactive flat map of Earth.Link
Coordinates and MotionsCelestial-Equatorial (RA/Dec) DemonstratorCA-Coordinates and Motions Demonstrates the celestial-equatorial (RA/dec) coordinate system, where declination and right ascension define an object's position on the celestial sphere.Link
Coordinates and MotionsFlat Sky Map Explorer NAAP-Basic Coordinates and SeasonsDemonstrates latitude and longitude on an interactive flat map of the celestial sphere.Link
Coordinates and MotionsPaths of the SunCA-Coordinates and Motions Shows how the declination of the sun varies over the course of a year using a horizon diagram.Link
Coordinates and MotionsSun Motions OverviewCA-Coordinates and MotionsNAAP - Motions of the Sun - Sun Paths PageShows the paths of the sun on the celestial sphere.Link
Coordinates and MotionsSun Motions Demonstrator, Motions of the Suns SimulatorCA-Coordinates and Motions NAAP-Motions of the SunModels the motions of the sun in the sky using a horizon diagram, demonstrating daily and seasonal changes in the sun's position.Link
Coordinates and MotionsSun's Rays SimulatorCA-Coordinates and Motions Shows how the sun's most direct rays hit different parts of the earth as the seasons change.Link
Coordinates and MotionsSun's Position on Horizon CA-Coordinates and Motions Shows how the direction of the sun at sunrise or sunset changes over the course of the year.Link
Coordinates and MotionsBig Dipper 3DCA-Coordinates and Motions Demonstrates how the stars of the big dipper, which are at various distance from earth, project onto the celestial sphere to give the familiar asterism.Link
Coordinates and MotionsSeasons Simulator CA-Coordinates and MotionsNAAP-Basic Coordinates and SeasonsShows the geometry of Earth and Sun over the course of a year, demonstrating how seasons occur. This simulator allows both orbital and celestial sphere representations of the seasonal motions.Link
Coordinates and MotionsCoordinate Systems Comparison, Rotating Sky ExplorerCA-Coordinates and MotionsNAAP-The Rotating SkyShows how the rotation of the earth leads to the apparent rotation of the sky, and how celestial sphere and horizon diagram representations of the sky are correlated.Link
Coordinates and MotionsDaylight Hours ExplorerCA-Coordinates and Motions  Shows the hours of daylight received during the year for an observer at a given latitude. This is an important factor contributing to the seasons. Link
Coordinates and MotionsAntipodes ExplorerCA-Coordinates and Motions Demonstrates antipodal points, which are points on opposite sides of Earth from each other.Link
Coordinates and MotionsSidereal Time and Hour Angle DemonstratorCA-Coordinates and Motions Shows how sidereal time and the hour angle of a star are related.Link
Coordinates and MotionsCelestial and Horizon Systems ComparisonCA-Coordinates and Motions Demonstrates how the celestial sphere and horizon diagram are related.Link
Coordinates and MotionsSidereal and Solar Time SimulatorCA-Coordinates and MotionsNAAP-Motions of the SunHelps demonstrate the difference between sidereal and solar time.Link
Coordinates and MotionsBands in the Sky NAAP - The Rotating Sky - Bands in the Sky PageShow a horizon diagram for a certain latitude and the bands (logcations) in the sky where the sun, moon, and planets can be found.Link
Lunar CyclesLunar Phase VocabularyCA-Lunar Cycles Shows the appearance of the moon at each of the named moon phases.Link
Lunar CyclesBasketball Phases SimulatorCA-Lunar Cycles  Shows an illuminated basketball that can be viewed from multiple directions, providing an analogy to moon phases.Link
Lunar CyclesThree Views SimulatorCA-Lunar Cycles Shows how the phase of the moon depends on the viewing geometry by allowing the moon to be viewed from the earth, the sun, and an arbitrary point in space.Link
Lunar CyclesLunar Phases SimulatorCA-Lunar CyclesNAAP-Lunar Phase SimulatorDemonstrates the correspondence between the moon's position in its orbit, its phase, and its position in an observer's sky at different times of day.Link
Lunar CyclesMoon InclinationCA-Lunar Cycles Demonstrates how the inclination of the moon's orbit precludes eclipses most of the time, leading to distinct eclipse seasons.Link
Lunar CyclesEclipse TableCA-Lunar Cycles Consists of a table of solar and lunar eclipses, showing the banding that represents the eclipse seasons that occur about twice a year.Link
Lunar CyclesEclipse Shadow SimulatorCA-Lunar Cycles Provides draggable earth and moon discs with shadows, which can be used to demonstrate how the umbral (complete) and penumbral (partial) shadows give rise to different types of eclipses.Link
Lunar CyclesTidal Bulge SimulationCA-Lunar Cycles Shows how the sun, moon, and earth's rotation combine to create tides.Link
Lunar CyclesPhase Positions DemonstratorCA-Lunar Cycles Demonstrates how planet and moon phases depend on orbital geometry. Users can drag two bodies around to see how the observed appearances change.Link
Lunar CyclesMoon Phases and the Horizon DiagramCA-Lunar CyclesNAAP-Lunar Phase SimulatorProvides a method of learning the correlation between the phase of the moon, the time of day, and the position of the moon in the sky.Link
Lunar CyclesSynodic Lag CA-Lunar Cycles Demonstrates the difference between a sidereal and synodic (solar) day, which arises from Earth's revolution around the sun.Link
Lunar CyclesFull Moon Declination SimulatorCA-Lunar Cycles Shows the declination range of the full moon over the course of a year, and the corresponding changes in altitude for a northern hemisphere observer.Link
Lunar CyclesLunar Phase Quizzer CA-Lunar Cycles Shows the standard orbital view of the Moon, but with the option to hide the Moon's phase, the Moon's position, or the Sun's direction.Link
Lunar CyclesMoon Phases With BisectorsCA-Lunar CyclesNAAP-Lunar Phase SimulatorDemonstrates a method for determining moon phases using planes that bisect the earth and moon. Link
Renaisance AstronomyPhases of VenusCA-Renaissance Astronomy Shows what Venus looks like through a telescope as the planets go around in their orbits.Link
Renaisance AstronomyPtolemaic Phases of VenusCA-Renaissance Astronomy Shows what Venus would look like through a telescope if Ptolemy's model was correct. Compare with the other Phases of Venus simulation.Link
Renaisance AstronomyPtolemaic Orbit of MarsCA-Renaissance Astronomy Shows Ptolemy's model for the orbit of Mars.Link
Renaisance AstronomyEpicycles DemoCA-Renaissance Astronomy Demonstrates that the heliocentric and geocentric models are equivalent for predictive purposes when limited to circular orbits.Link
Renaisance AstronomyCopernican Solar System NAAP - Solar Systems Models - HeliocentrismA simple animation showing the circular orbits of the 6 inner planets around the Sun. Link
Renaisance AstronomyRetrograde MotionCA-Renaissance Astronomy Demonstrates the retrograde motion of Mars with an annotated animation.Link
Renaisance AstronomyKepler's Third Law CA-Renaissance Astronomy  Lets one calculate the period of a planet from its semimajor axis, and vice versa.Link
Renaisance AstronomySynodic Period CalculatorCA-Renaissance Astronomy Lets one calculate the sidereal period of the planet (P) from the synodic period (S), and vice versa.Link
Renaisance AstronomyPlanetary Configurations SimulatorCA-Renaissance Astronomy Models the movements of the planets around the sun in a simplified Copernican model of the solar system.Link
Renaisance AstronomyPlanetary Orbit SimulatorCA-Renaissance AstronomyNAAP-Planetary OrbitsModels the motion of a hypothetical planet that orbits the sun according to Kepler's laws of motion. This simulator includes controls for investigating each of Kepler's laws.Link
Renaisance AstronomyEccentricity DemonstratorCA-Renaissance AstronomyNAAP - Planetary Orbits - Kepler's Laws of Planetary Motion PageDemonstrates the parameters that define the eccentricity of an ellipse. Link
Renaisance AstronomyEarth Orbit PlotCA-Renaissance Astronomy Shows the orbital period as a function of orbital distance for satellites of Earth. Link
Renaisance AstronomyNewton's Law of Gravity CalculatorCA-Renaissance Astronomy Allows one to calculate the force of gravity acting on a variety of masses over a range of distances.Link
Renaisance AstronomyGravity AlgebraCA-Renaissance Astronomy Shows how the force of gravity would be different if the values used in Newton's law of universal gravitation formula are changed.Link
Renaisance AstronomyProjectile (Escape Velocity) Simulation   NAAP - Atmopheric RetentionAllow you to shoot projectiles with various speeds away from various solar system bodies and iteratively determine their escape speed.Link
Light & SpectraBlackbody Curves of MeltingCA-Light & SpectraLight & SpectraA movie showing the heating and eventual melting of a nail, and the theoretical blackbody curve produced in the process.Link
Light & SpectraSpectrum ExplorerCA-Light & SpectraLight & SpectraAllows one to generate a variety of simulated spectra, depending on factors such as the type of source, luminosity class, spectral type, and individually selected elements.Link
Light & SpectraEM Spectrum ModuleCA-Light & SpectraLight & SpectraSurveys the electromagnetic spectrum, showing a typical astronomical image for different wavelengths of light and the kind of instrument that would take such an image.Link
Light & SpectraComparison of Three Blackbody CurvesLight & SpectraNAAP-Blackbody Curves and UBV Simulator - Spectral Types of Stars Page Allows the users to change the scale illustrating the blackbody curves for a 3000K, 6000K, and 12,000 K object.Link
Light & SpectraBlackbody CurvesCA-Light & SpectraNAAP-Blackbody Curves and UBV SimulatorDemonstrates how the blackbody spectrum varies with temperature. This explorer also shows how the relative intensities observed through different filters (a 'color index') can give an estimate of temperature.Link
Light & SpectraFilters SimulatorCA-Light & SpectraNAAP-Blackbody Curves and UBV SimulatorDemonstrates how different light sources and filters combine to determine an observed spectrum. This simulator also shows the perceived colors associated with the spectra shown.Link
Light & SpectraHydrogen Atom Simulator CA-Light & SpectraNAAP - Hydrogen Energy LevelsModels a hydrogen atom and its interactions with light, demonstrating the quantum nature of absorption and emission.Link
Light & SpectraHydrogen Energy Level AbundancesLight & SpectraNAAP - Hydrogen Energy Levels - Level Abundances PageShow the relative abundances of hydrogen atom electron levels for various temperatures.Link
Light & SpectraThree Views Spectrum DemonstratorCA-Light & SpectraLight & SpectraDemonstrates how different spectra can arise from a light bulb (a thermal source) and a cold, thin gas cloud. The spectrometer shows emission, absorption, or continuous spectra based on where the draggable telescope is pointed.Link
Light & SpectraExtrasolar Planet Radial Velocity DemonstratorCA-Light & SpectraLight & SpectraDemonstrates how the spectrum of a star is shifted as it and its planet orbit their common center of mass.Link
Light & SpectraDoppler Shift DemonstratorCA-Light & Spectra Shows circular waves expanding from a source. Movement of the source or observer affects the frequency of the waves seen by the observer, demonstrating doppler shift.Link
Telescopes and Astronomical InstrumentsTelescope Simulator CA-Telescopes and Astronomical InstrumentsTelescopes and Astronomical InstrumentsDemonstrates the properties of a telescope, and how these vary with aperture and eyepiece selection.Link
Telescopes and Astronomical InstrumentsCCD SimulatorCA-Telescopes and Astronomical InstrumentsTelescopes and Astronomical InstrumentsShows a rainfall and bucket analogy to CCD imaging. Link
Telescopes and Astronomical InstrumentsSnell's Law DemonstratorCA-Telescopes and Astronomical InstrumentsTelescopes and Astronomical Instruments Demonstrates Snell's Law, a formula that describes how light is refracted when it moves between different media.Link
Telescopes and Astronomical Instruments Registration SimulatorTelescopes and Astronomical InstrumentsNAAP-Variable Star PhotometrySimulates the alignment of CCD frames and identifying the offsets so that objects are at overlying locations.Link
Telescopes and Astronomical InstrumentsBlink Comparator Simulator  NAAP-Variable Star PhotometryAllow one to succesively "blink" CCD frames to identify moving objects.Link
Telescopes and Astronomical InstrumentsPhotometry Simulator NAAP-Variable Star PhotometryAllows one to perform differential photometery and calculate relative stellar magnitudes on a CCD frame.Link
Sun and Solar EnergyProton-Proton AnimationCA-Sun and Solar Energy Shows an animated diagram of the proton-proton chain reaction, which is the dominant fusion reaction in the sun's core.Link
Sun and Solar Energy CNO Cycle Animation CA-Sun and Solar Energy Shows an animated diagram of the CNO cycle, which dominates in stars larger than the sun.Link
Stellar PropertiesDistance Modulus ExplorerCA-Stellar PropertiesStellar Properties Shows how the distance modulus formula combines apparent and absolute magnitudes to give the distance to a star.Link
Stellar PropertiesStellar Velocity CalculatorCA-Stellar PropertiesStellar PropertiesShows how the distance to a star, its doppler shift, and its proper motion allow one to calculate the star's true space velocity.Link
Stellar PropertiesStellar Luminosity CalculatorStellar PropertiesNAAP - Hertzsprung-Russell Diagram - Luminosity PageShows how the luminosity of a star depends upon its surface temperature and radius.Link
Stellar PropertiesParallax CalculatorCA-Stellar PropertiesStellar PropertiesDiagrams the geometry and shows the math involved in determining a star's distance via parallax.Link
Stellar PropertiesParallax ExplorerStellar Properties NAAP - Cosmic Distance LadderAllow one to experiement with parallax using different baselines and errors in the observations.Link
Stellar PropertiesSpectroscopic Parallax SimulatorCA-Stellar PropertiesNAAP - Cosmic Distance Ladder Demonstrates how the technique of spectroscopic parallax works.Spectral type and luminosity class determine the observed spectrum of a star, from which the star's luminosity can be estimated.Link
Stellar PropertiesStellar Luminosity CalculatorCA-Stellar PropertiesStellar PropertiesDemonstrates how a star's luminosity depends on its temperature and radius.Link
Stellar PropertiesFlux SimulatorCA-Stellar PropertiesStellar PropertiesDemonstrates the inverse square law of light with a lightbulb and detector.Link
Stellar PropertiesHR ExplorerCA-Stellar PropertiesStellar PropertiesIntroduces the Hertzsprung-Russell Diagram, a plot showing the relationship between luminosity and temperature for stars.Link
Stellar PropertiesHR Diagram Star Cluster Fitting Explorer NAAP - Cosmic Distance LadderAllows determining the distance to a cluster by fitting the cluster's stars to the main sequence in an HR diagram.Link
Binary and Variable StarsEclipsing Binary SimulatorCA-Binary and Variable StarsNAAP-Eclipsing Binary SimulatorModels the motions of two stars in orbit around each other, and the combined lightcurve they produce. This simulator allows the user to control multiple parameters to see how they effect the lightcurve. Includes several real datasets.Link
Binary and Variable StarsAliasing in Wagon WheelsCA-Binary and Variable StarsBinary and Variable StarsDemonstrates aliasing through the analogy of a wagon wheel being filmed. For some combinations of frame rates and true rotation speeds the wheel can appear to rotate backwards.Link
Binary and Variable StarsCenter of Mass SimulatorCA-Binary and Variable StarsNAAP - Eclipsing Binary Stars - Center of Mass PageShows how the center of mass of two objects changes as their masses change.Link
Binary and Variable StarsLightcurve Simulator CA-Binary and Variable StarsNAAP - Eclipsing Binary Stars - Light Curves PageShows how a lightcurve is constructed from observations of an eclipsing binary system.Link
Binary and Variable StarsVariable Star Photometry AnalyzerCA-Binary and Variable StarsNAAP-Variable Star Photometry Centerpiece for an advanced lab on variable star photometry.Link
Milky Way Galaxy Milky Way Rotational VelocityCA-Milky Way Galaxy A plot of the rotational velocity of stars at varying distances from the center of the milky way. A draggable cursor allows determining the contained mass implied by the curve.Link
Milky Way GalaxyTraffic Density AnalogyCA-Milky Way Galaxy The build-up of traffic behind a slow moving tractor provides an analogy to the density wave formation of spiral arms.Link
CosmologyLookback Time SimulatorCA-Introductory Concepts An animation of coins attached to a balloon, providing an analogy to the expansion of the universe. The coins represent galaxies, which maintain their scale while the space between them grows.Link
CosmologyBalloon Universe CA-Cosmology An animation of coins attached to a balloon, providing an analogy to the expansion of the universe. The coins represent galaxies, which maintain their scale while the space between them grows.Link
CosmologyGalactic Redshift Simulator CA-Cosmology  Demonstrates the redshift of a galaxy due to the expansion of the universe, and the effect this shift has on the galaxy's brightness as observed through various filters.Link
CosmologySupernova Light Curve Fitting Explorer NAAP - Cosmic Distance Ladder Allows determining the distance to a supernova by fitting observations to a theoretical Type Ia curve.Link
Solar SystemPlanet Formation Temperatures PlotCA-Solar System Characteristics Shows planet formation temperature as a function of distance from the Sun. Also indicates the state (gas or solid) of several substances at the given distance and temperature. Link
Solar SystemSolar System Properties ExplorerCA-Solar System Characteristics Allows one to explore a set of histograms for characteristics like number of satellites, mass, orbital period, etc. for the terrestial and jovian planets, plus Pluto. Link
Solar SystemMaxwell Distribution NAAP - Atmospheric RetentionSimple animation shows the distribution of the speeds of gas particles.Link
Solar SystemGas Retention Plot NAAP - Atmospheric RetentionShows how the molecular mass, temperature, and escape speed determine whether a gas will remain gravitationally bound to a planet.Link
Solar SystemGas Retention Simulator NAAP - Atmospheric RetentionDemonstrates how gases of different molecular masses behave when maintained at thermodynamic equilibrium in a chamber. The chamber can be set to allow particles that exceed a certain speed to escape, providing an analogy for the bleeding of a planet's atmosphere into space. Link
Solar SystemDriving Through SnowCA-Animations Shows a snow shower from the perspective of a car driving through it, demonstrating how the snow seems to diverge from some central point (the radiant). Provides an analogy to a meteor shower.Link
ExtraSolar Planets Influence of Planets on the Sun CA-Animations NAAP - Atmospheric RetentionShows the movement of the sun due to the gravitational pull of the planets. The contribution from each planet can be isolated by toggling checkboxes.Link
ExtraSolar PlanetsRadial Velocity GraphCA-Animations Shows a star and planet in orbit around each other while tracing out the star's radial velocity curve.Link
ExtraSolar PlanetsTransit SimulatorCA-Animations Demonstrates how a planet passing in front of its parent star can cause dips in the star's lightcurve, potentially leading to the planet's detection.Link
ExtraSolar PlanetsExtrasolar Planet Radial Velocity DemonstratorCA-Animations Demonstrates how the spectrum of a star is shifted as it and its planet orbit their common center of mass.Link
ExtraSolar PlanetsRadial Velocity Simulator CA-Animations Models the motion of an extrasolar planet and its star around their common center of mass, and the effect this motion has on the star's observed radial velocity.Link
ExtraSolar PlanetsPulsar Period SimulatorCA-Animations Demonstrates how the movement of a pulsar and planet around their common center of mass affects the timing of pulse arrivals.Link
ExtraSolar PlanetsHammer Thrower ComparisonCA-Animations Illustrates how the movement of a star and its planet about their center of mass compares to a hammer thrower swinging a heavy metal ball.Link
ExtraSolar PlanetsCircumstellar Habitable Zone Simulator NAAP - Habitable ZonesDemonstrates location and evolution of the stellar habitable zone, which is the region around a star where surface water may exist on a earth like planet.Link
ExtraSolar PlanetsMilky Way Habitability Explorer NAAP - Habitable ZonesShows how two factors important to life – metallicity and extinction risk – vary throughout the Milky Way Galaxy.Link

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