Parallax: The trickery of eyes that unveils the universe

by Sridevi · May 27, 2023

An illustration showing the parallax effect. When viewed from "viewpoint A" the object appears in front of the blue background. By contrast, when viewed from "viewpoint B", the object appears in front of the red background. Image by Sarang (CC BY 2.0)

Have you ever noticed while going on a drive that the objects in the distance move much slower than the objects that are closer to you? If not, let me come up with another activity you can try. Close your right eye, hold your thumb in front of you, and concentrate on it. Now open the right eye and close your left eye. Did you see an apparent shift in the position of your right thumb without you moving it? This phenomenon is known as the parallax effect and is caused by the way our eyes perceive depth. The ability to perceive depth is essential for our survival and allows us to navigate the world around us and avoid potential dangers.

The parallax effect, or simply parallax, occurs because each eye sees the world from a slightly different angle. This allows our brain to create a three-dimensional image of the world around us, but it also means that the position of objects appears to shift slightly when we view them through different eyes. Astronomers use this effect to calculate the distance to nearby stars by observing the position of the star from two different points on earth. This technique is known as stellar parallax, and having first been used by the German astronomer Friedrich Bessel in the early 19^th century, has since become a standard tool in astronomy ^[1].

Parallax also plays an important role in fields like computer vision and robotics. By capturing multiple images of an object from different angles, engineers can create realistic 3D models of objects and environments^[2]. This technique is called stereo vision, and is used in creating immersive experiences like virtual reality, especially in the video game industry.

While parallax seems to be a relatively simple phenomenon, its applications are far reaching. By exploring the physics and neuroscience behind this effect, scientists continue to uncover new insights into how our brains process visual information and perceive the world around us.

[1] Schindler, G. (2018). A Brief History of Stellar Parallax. Sky & Telescope

[2] Cap. O’Rourke to the rescue”. New Straits Times Malaysia. 1988-09-01. Retrieved 2009-07-06.

Edited by Hazel Imrie

Copy-edited by Molly Donald