We cannot know for .certain when humans first began to carefully observe objects in the sky. but it is highly likely that it was important from prehistoric times to understand the environment around them. If you were living many thousands of years ago， you would have been aware of the passage of the Sun and Moon across the sky. Also the apparent rotation of the star constellations in their fixed patterns， together with those strange objects (planets Venus. Mars. Jupiter and Saturn) that looked like stars to the naked eye， but seemed to wander between the fixed stars ih an odd way.