Out of This World

3. The scientist who suggested that the planets orbit in an elliptical orbit.
7. The model of the solar system with the sun at the centre.
11. The third planet from the sun.
12. Day and night occur because of the __________ of the Earth on its axis.
14. When an aircraft is travelling at a constant speed in the air, the forces acting on the aircraft are _____________.
15. The force that keeps planets in orbit.
16. A force is a push or ________

1. A force can change the shape, speed or __________ of an object.
2. The distance light travels in one year.
4. The largest planet in our solar system.
5. The model of the solar system in which the Earth is at the centre and all the planets orbit around the Earth.
6. The galaxy that Earth is in.
8. The time taken for the Earth to orbit around the sun is one _____.
9. The scientist who invented the telescope.
10. The planet closest to the sun.
13. The north end of a bar magnet will ___________ the south end of another bar magnet.
15. A cluster of solar systems held together by gravity.