Here are the completed definitions:

1. sun = the star that shines during the **day**.
2. explore = **to travel** round a place in order to learn about it.
3. far-fetched = **unlikely** 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 **true** or definite.
8. invent = create something that didn’t **exist** before.