How fast is Earth moving Q&A with an expert With a bit of simple calculation, using parallax we can also figure out the distance to that star. We see the star from different vantage points. If we look at a star (located relatively close to us) in the summer and look at it again in the winter, its apparent position in the sky changes because we are at different points in our orbit. It takes about 365 days for us to orbit the sun.
The same thing happens on Earth when we look at stars. That's because your left and right eyes look at the finger with slightly different angles. Then close your right eye, and look at the finger with your left. Look at it with your left eye only, closing your right eye. For a simple example of parallax, hold up your index finger in front of your face at arm's length. Another reason that humans started to realize that we might not be the center of the universe came from looking at parallax, or apparent change in the position of the stars with respect to each other.