02 / SPACE
A universe
of questions.
Orbits, planets and the light from distant worlds. Big distances become more approachable when we start with one clear model.
Conceptual diagram, not to scale. Gravity bends a satellite’s path toward Earth.
An orbit is a
continuous fall.
Gravity is still present. Sideways motion makes all the difference.
A pull inward
Earth’s gravity accelerates a satellite inward. It changes the direction of the satellite’s motion, curving its path.
Keep moving sideways
With suitable speed and altitude, a satellite falls around Earth instead of reaching the ground. Its path need not be a perfect circle.
Why astronauts float
An orbiting spacecraft and the people inside fall together. Their apparent weightlessness does not mean gravity has disappeared.
MAKE THE SCALE VISIBLE
The solar system
needs more room.
An astronomical unit, or AU, is about the distance from Earth to the Sun: roughly 150 million kilometres. It is useful for comparing planetary orbital distances.
If 1 AU becomes 10 centimetres on a model, Neptune’s roughly 30 AU distance becomes about 3 metres. Planet sizes would need a different scale to stay easy to see.
A line of planet markers is a distance comparison, not a picture of where all the planets are at one time.
Background: NASA: gravity and mechanics · NASA JPL: scale solar system
CHECK YOUR MODEL
What does this drawing leave out?
Are the planets lined up?
No. They travel in their own orbits. A classroom line makes distances easy to compare, but does not show their changing positions.
Are orbital distances fixed?
No. Planetary orbits are ellipses. A scale model using one characteristic distance simplifies that changing separation.
Is a planet’s size shown to scale?
Only if the model explicitly uses the same scale for diameter and distance. Our printable activity models orbital distance, not planet diameter.
PUT CURIOSITY TO WORK
Read it. Try it. Question it.
Explore new space research, or take a paper-first investigation into your classroom.