Demonstrations for Introduction to Astronomy: Solar System

* = equipment from Mike Thomason = MT

Useful things to remember:

- GO20/30 face south - so instructor faces north. So sides of room useful for NSEW

Test of Astrology

Omarr Reads the Stars

Get horoscope from yesterday's paper (Daily Camera's good)

Cut out horoscopes - separate signs+ dates - scramble. Number each.

Paste onto page and ask 3 questions:

  • Write down if horoscope read the day before
  • Put number corresponding to sign in box
  • Put number corresponding to best description of your yesterday in box
  • Analyize to show correlation weak, "sexy" horoscopes popular.  
    Earth's Spin -> Apparent Motion of Stars
    Gyroscope* (large, power-driven)
                Shows spin axis pointing in same direction even when moved around
                Analogy to Earth's spin axis pointing at Polaris
                Add weight to show precession


    Demonstrate spin with axis pointing towards Polaris
    New York leads Los Angeles -> direction
    Human (cut out and taped to globe) standing on Boulder -> orientation
    Latitude = angle between Polaris and N. horizon

    Hand-held pendulum + Globe

    Pendulum continues swinging in same direction even if surface underneath rotates
    Set pendulum swinging over globe and rotate globe to show how pendulum appears to rotate relative to person standing on the globe

    Foucault Pendulum - in Gamow Tower - window from outside

    Rotating Stage*

    Demonstrate pendulum - using large tripod pendulum*
    Demonstrate apparent motion of stars have some students on rotating stage and students in audience as stars. Compare apparent motions seen by each.
    Annual motions
    globe around "Sun" (= overhead or yellow ball)
    tilt towards vs. away from sun equinoxes where sun overhead at different times of year
    Zodiac Use overhead as sun and use objects in different directions (e.g. walls on 4 sides of room) as constellations - then walk around overhead and show how only some constellations visible at different times of year.
    Angular Size
    Arm waving
    Stretched hand = 15° = 1 hour of rotation
    Fist = 10°
    Width of index finger = 1°
    Width of little finger = 1/2° = angular size of Sun and Moon
    Get all students to judge angular size of lights in ceiling


    Stand at varying distance from globe and show with arms how angular size varies as you move towards / away from globe

    Sidereal vs. Synodic

    Globe + overhead
    Use object on wall as reference star. Show how Earth/globe motion around the Sun/overhead leads to day relative to stars is shorter than day relative to Sun.
    Synodic vs Sidereal month is harder. But you can use people to be moving Earth with Moon orbiting. Requires good 'actors' - TAs probably.


    Gyroscope* + weight
    Set the power-driven gyroscope going pointing towards Polaris.
    Add weights -> precession

    Moon Motions / phases

    "Moon on a stick"
    Ideally, give each student a polystyrene ball on a stick (about 50 available in Dept) and turn off all lights except one central light.
    Moving ball on stick around one's head (Earth) dramatically illustrates phases.
    Fruit - particularly cantaloupe - in sunshine also works well.
    Use a paper plate to show that a disk does not work - Greeks worked out the Moon had to be a sphere illuminated by the Sun.

    Globe + ball / fruit

    Advantage of fruit = novelty (= memory) - and it usually has a "feature" which can be used to be the "face" of the Moon - or non-spherical -> bulge.
    Move Moon around globe -> "phase lock" (orbital = spin period)+ third object (e.g. overhead) as Sun to show lunar vs. sidereal month

    Hula hoop

    Orbit of Moon - tilted 5 degrees with respect to the ecliptic
    Nodes - line up -> eclipses

    Eclipses to Scale

    This is hard - Colorado Model Solar System scale has Sun about 10 cm (= grapefruit) which puts the Earth as 1 mm (grain of rice) at about 20 m.
    Making realistic shadows is very difficult due to scattering of light in room.


    Get each student to hold finger up and blink.
    Move finger farther away / closer -> appear to move more or less?
    Pick object / person across room - move head side to side.
    Extend baseline to walking distance.

    Retrograde motion

    Planetarium = best
    Show retrograde motion of Mars using annual motion only.
    Show relative motions using orrery.

    Ptolemy vs. Kepler -

    JAVA applet demonstration - needs PC running windows + Netscape 4.0 - go to Kepler Module
    Newton's laws of motion & Gravity
    Newton's laws of motion - cabbages
    About 1 kg each - illustrates a kilogram
    Apply a force -> accelerates (throw cabbage across room)
    Apply bigger force - accelerates more (goes farther across room)
    Take smaller object (onion?) - less force needed for same acceleration

    Newton's third law

    Balloon rocket
    Skateboard - unless you have a large, stable skateboard or a "dolly"*, this does not work very well. Bricks* wrapped in towels to throw off the back.
    Newton's law of gravity - cabbages
    Force between 2 cabbages (one red, one green?)
    Force between cabbage and Earth


    Gravity applied to cabbage -> drop -> accelerates
    Drop 2 objects (red & green cabbages) from balcony

    Friction effect
    Drop sheet of paper. Crumple up into ball and drop


    Balance of centrifugal and gravitational forces - Eraser on a string - twirl around head, let go.
    Into orbit - throw object across room, throw harder -> farther (argue if thrown hard enough it would not hit the ground until over horizon where Earth curved down. Harder again -> orbital velocity, orbit)


    Overhead or incandescent bulb* + hand-held diffraction grating -> ceiling
    Projection through a grating onto screen*

    Colored objects - e.g. planets

    Colored card & transparencies with overhead -> reflection, absorption and transmission of light in different parts of the visible spectrum
    Black / white card -> albedo

    Wein's Law

    Electric stove / element - shows bright orange to deep red (to "heat" = IR)
    Incandescent lamp on rheostat*
    Rigel vs. Betelgeuse - slides of Orion & spectra

    Stefan-Boltzmann Law

    Incandescent lamp on rheostat*


    Transmission gratings for each student* (about 1" square)
    Gas discharge tubes* for different gases.
    Compare with incandescent and fluorescent lamps
    Atomic (simple) vs. molecular (complex)


    Large lenses + light source* to show light gathering + focus
    Curved mirror* + light source
    Refracting telescope*
    Cassegrain - SBO

    Properties of Planets

    Paper cups filled with different materials (e.g. sand, lead weights, polystyrene chips, water) labelled with density -> "feel" for range in density.


    Radioactivity - everybody stands up, each toss coin. Heads sit down.


    Slides of Jupiter and human in both reflected sunlight and thermal IR
    Reflected sunlight and thermal glow -> double hump
    Solar spectrum above atmosphere, on ground
    Thermal emission of Earth
    Viscosity of rock
    Lava lamp
    Silly putty



    Powers of Ten - Shows scales of universe in 40 orders of magnitude. Depending on version, may need to fast forward to the actual annimation (10mins)

    Seasonal Dance - Shows seasonal changes in vegetation, snow and ice coverage as sub-solar point moves in latitude with the seasons. (7 mins)

    Apollo - Shows astronaut dropping hammer on the Moon.

    Shuttle video of "weightless" astronauts?

    Hubble launch & refurbishing missions