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

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 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

Globe

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.
Seasons

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

Globe

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

Sidereal vs. Synodic

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.

Enactment
Synodic vs Sidereal month is harder. But you can use people to be moving Earth with Moon orbiting. Requires good 'actors' - TAs probably.

Precession

Gyroscope* + weight
Set the power-driven gyroscope going pointing towards Polaris.

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.

Parallax

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.

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
http://solarsystem.colorado.edu - 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

Acceleration

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

Orbits

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)

Light

Spectrum
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*

Spectroscopy

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)

Telescopes

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

Properties of Planets

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

Age

Repeat.

Spectra

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

Videos

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