Here are the completed definitions:

1. sun = the star that shines during the **day**
2. explore = **look** round a place in order to learn about it
3. far-fetched = **not** easy to believe
4. revolve around something = go round something in a **circle**
5. experiment = a scientific **test** in order to learn or find out about something
6. scientist = a person who **studies** or teaches science
7. confirm = say or show that something is **certain** or definite
8. in other words: used for saying something in a **different** way
9. invent = create something that didn’t **exist** before