An interactive museum of astronomy reasoning instruments.
Explore observables, models, and inferences—like doing experiments on ideas.
Play with the universe. Learn the physics.
Begin with the core orbit ideas before branching out.
Key idea: Describe how orbital speed changes along an ellipse.
Use this instrument to connect orbit shape to speed changes (Kepler 2) and connect orbit size to period scaling (Kepler 3).
Key idea: Define retrograde motion as an apparent reversal caused by viewing geometry and relative motion.
Use a simple Keplerian model to visualize how the direction to a planet can briefly reverse in the sky (retrograde) even though the planet n
Key idea: Use momentum conservation to explain why the lighter body moves faster around the barycenter.
This instrument turns binary motion into a reasoning workflow: predict first, test conservation constraints, connect orbital dynamics to rad
A simple loop for every exhibit.
Moon phases, seasons, and the view from Earth.
Key idea: Explain why the Moon has phases using the Sun–Earth–Moon geometry.
A short, interactive model for relating phase angle to what fraction of the Moon appears illuminated.
Key idea: Relate an object’s apparent size to its physical size and distance.
This demo explores why objects can look big or small in the sky depending on both their physical size and their distance.
Key idea: Explain eclipses using alignment and shadow geometry.
This demo helps explain why eclipses do not occur every month: the Moon must be at New/Full *and* near a node so its ecliptic latitude $|\be
Key idea: Explain why axial tilt causes seasons.
This demo lets you change day-of-year, axial tilt, and latitude to explore how sun angle and day length change through the year in each hemi
Key idea: Define conjunction and opposition as seen from Earth.
Explore how conjunctions and oppositions are line-of-sight alignments caused by relative motion, and estimate how long it takes for the same
Kepler's laws, retrograde motion, and gravitational dynamics.
Key idea: Identify quantities that remain constant under specific assumptions.
Start with a circular case ($v/v_{\\rm circ}=1$), then move toward escape ($\\sqrt{2}$) and beyond to see how $\\varepsilon$ changes sign.
Key idea: Define conjunction and opposition as seen from Earth.
Explore how conjunctions and oppositions are line-of-sight alignments caused by relative motion, and estimate how long it takes for the same
Blackbody radiation, electromagnetic spectrum, and spectral analysis.
Key idea: Relate radial motion to observed wavelength and frequency shifts in spectral lines.
Explore how relative motion shifts spectral lines and why astronomers can measure radial velocity from light alone.
Key idea: Explain why atoms emit and absorb light only at specific wavelengths using the Bohr model.
Infer atomic structure from line wavelengths, then invert the task: observed $\lambda$ to inferred transition. The instrument links Bohr str
Key idea: Relate temperature to Planck-curve shape and Wien peak shift.
Use the temperature slider (or presets) to compare where the spectrum peaks and how the overall power changes.
Key idea: Order EM bands by wavelength and frequency.
This demo helps you connect wavelength, frequency, and photon energy across the electromagnetic spectrum.
Resolution, diffraction, and optical design.
Key idea: Distinguish magnification from resolution.
This demo shows how telescope resolution depends on wavelength and aperture, and how atmospheric seeing can blur images from the ground.
Statistics, measurement, and scientific reasoning.
Key idea: Relate radial motion to observed wavelength and frequency shifts in spectral lines.
Explore how relative motion shifts spectral lines and why astronomers can measure radial velocity from light alone.
Key idea: Interpret galaxy rotation curves as velocity-versus-radius observables inferred from Doppler measurements.
Explore why spiral-galaxy rotation curves stay nearly flat at large radius and what that implies about dark matter across scales.
Key idea: Trace causality: Earth moves in orbit, line-of-sight changes, apparent star position shifts.
This demo makes the full causal chain legible: Earth moves, line-of-sight changes, and the target star appears to shift against fixed backgr
Stellar structure, evolution, and equations of state.
Key idea: Use observer-space and theorist-space views to interpret stellar populations as measurement-built maps.
This ASTR 201 instrument treats the HR diagram as both a measurement-built map and a hidden-variable inference engine, with staged reveals a
Key idea: Compare gas, radiation, and electron-degeneracy pressure channels using cgs units.
A pressure-channel lab for ASTR 201 that keeps units explicit, assumptions visible, and model diagnostics tied to the same state.
Galaxy types, rotation, and large-scale structure.
Key idea: Interpret galaxy rotation curves as velocity-versus-radius observables inferred from Doppler measurements.
Explore why spiral-galaxy rotation curves stay nearly flat at large radius and what that implies about dark matter across scales.
Expansion, dark energy, and the cosmic microwave background.
Key idea: Interpret galaxy rotation curves as velocity-versus-radius observables inferred from Doppler measurements.
Explore why spiral-galaxy rotation curves stay nearly flat at large radius and what that implies about dark matter across scales.