Parallax is the apparent motion of an object based on different lines of sight.
Calculating Parallax
Edit
Here we see an example of a parallax problem setup
In the example to the right, we see that from the movement of the Earth, there has been an angle $ \theta $ introduced between where the earth was and where it currently sits.
In this sort of problem, we will primarily be using the fact that :
$ tan\theta = \frac {1 AU}{d} $
Therefore, given either $ d $ or $ \theta $, we can solve for the other. Note that $ d $ is the distance from the sun to the object.
