| Term | Definition |
|---|---|
| altitude | the distance above the Earth's surface |
| line of sight | the straight, unblocked path that is followed by light from an object to an eye (what you can see with your eyes without anything blocking it) |
| horizon | the imaginary line where the sky meets Earth or the ocean |
| point of view | the position where an observation is made from |
| rotation | spinning on axis |
| orbit | the path and length of time one object takes to travel around another object (Earth's path around the sun, moon's path around the Earth) |
| axis | an imaginary axle (stick) that a planet spins on |
