We know that that the direction of light from a star in space can seem to be changed because of the earth's rotation and revolution around the sun. This is called "phenomenon aberration."

Scientists discovered this phenomenon by observing the difference of directions in which stars appear season by season. The position of a star seemingly changes because of the earth's motion, but the light itself goes directly to the earth. Aberration occurs for the same reason that rain seemingly pours down in front of you when you run, yet is actually dropping vertically.

It is also known that angles of aberration can be calculated.