Across
- 3. Things that revolve around another object in space.
- 6. Two objects that attract each other due to their mass.
- 7. A source of energy that is endless.
Down
- 1. Trees cannot produce fruit without them.
- 2. We will run out of this in 39 years.
- 4. This is caused by the Moon's gravitational pull on Earth.
- 5. Our Solar system is one of many millions of solar systems inside this.