Cosmic falling

What the Activity is for

'Down' on different planets.

Here you can explore how the idea of down varies as you move from one planet to another, from one planetary system to another, from one star system to another, or from one galaxy to another. Down depends on the local gravity arrows.

There are significant links between this activity and the activity Falling all over the world which can be exploited.

What to Prepare

• large spectacular images of clearly separated astronomical objects, perhaps shown using a data projector
• a selection of small plastic toy people – astronauts, if possible
• Some cardboard arrows labelled down, scaled for the people
• some cardboard force arrows labelled gravity
• Balls of different diameters to model planets

What Happens During this Activity

Start with showing the large image. Add the astronaut, and ask:

Teacher: If she dropped something, which way would it fall?

Then build on the answers to add a down arrow at this location. Move the astronaut around the astronomical object, repeating the question and discussions to leave a trail of down arrows around the astronomical object, at a variety of locations surrounding the object, at a number of distances from the centre.

As a next step you might add gravity arrows to each of the figure's locations, giving a reason such as:

Teacher: Gravity is the name that we give the force that makes things fall. Wherever we see things falling, we expect to find the force of gravity at work. Things fall down, as we've seen. So the gravity arrows and the down arrows point in the same direction.

We'd suggest repeating this for a number of distinctive astronomical objects, from planets, through asteroids, to the stars and moons.

At several stages you might add in a three-dimensional model using one of the balls and a number of astronomical figures. It all depends on how well you think the transition between the three-dimensional and two-dimensional is progressing.

As a summary of the whole exercise you might produce a two-dimensional diagram, where the central object is deliberately labelled as a number of astronomical objects explicitly. Surround this with a number of pairs of down and gravity arrows. Add astronomical figures as observers if that seems to make this thought experiments more concrete.

You might supplement this activity with some video clips of people dropping things in space: just make sure the people and the camera are not falling as well to avoid conceptual difficulties.