The sun at the heart of our solar system provides heat, energy, and light, which is fundamental to life on Earth. Just about all living things have developed ways of sensing and making use of light. Fossil evidence shows that the eye developed over 450 million years ago. Some researchers say that the development of stereoscopic vision, along with our larger brain and ability to walk upright helped accelerate human evolution to where we are today.
Vision is the dominant sense for humans; about 30 percent of the cortex in the human brain is dedicated to processing what we see. In comparison, touch uses 8 percent, and hearing just 3 percent. The retina at the back of each eye contains 150 million light-sensitive cells and is an outgrowth of the brain.
Rather than viewing a completely objective reality, what we see is actively constructed by our brains in real time. A bit like a video camera connected to a computer, the powerful visual system processes what we see into a consistent and coherent view of reality. To do this efficiently and effectively the eyes and brain have evolved shortcuts and best guesses. For instance, only the centre of our vision is ever fully processed in high definition and colour. Although our peripheral vision is good at spotting things coming into view, it’s not very good at colour, shape, or detail. Many visual illusions make use of these processing gaps and how the brain adapts to them.