5 Crazy Facts About the Human Eye
5 The Rods and Cones
Your eye contains two different types of “photoreceptor cells,” which basically just means “light sensitive cells.” These are the rods and the cones. Rods help you see in low light and can distinguish between hues, so they help you see shapes and contrasts, but they cannot perceive the different colors. That’s the job of the cones, which can see all sorts of color variation, but only with sufficient light. So it’s not that the colors of things change at dawn or dusk or in a dimly lit room, it’s that your eye perceives colors differently depending on the amount of available light.
4 And You Thought Fiber Optics Were Cool?
The optic nerve is the bundle of little nerve fibers that connects your eyeball to your brain, transmitting the raw data signals the eye takes in to your processing center, which translates the various shapes, colors and lights into the vision of, say, a sandwich. And while the optic nerve is only around 2 inches long and less than 1/4 inch thick, each of them is made up of well over a million of those little nerve fibers.
3 We Can Rebuild … We Have the Technology
While you can’t get an “eye transplant,” in which your whole eyeball is replaced after damage, doctors can transplant the cornea, which is the thick, clear front layer of the eye. The cornea protects the eyeball and serves as a lens, helping to focus the light coming into the eye so you can see the clearest, sharpest images.
2 Going the Distance
At sea level, the average human can see about 10 or 12 miles away on a “clear” day. But that’s just because even on an ostensibly clear day, the air is filled with vapor, dust, particulate pollution and so on. In theory, there is hardly any limit to the distance you can see at all! You can see nighttime stars, can’t you? Their light is often reaching you from billions or even trillions of miles away. And as all vision is just the perception of light, be it direct or reflected, your eye is technically seeing something that is whole galaxies away.
1 Under Pressure
The “normal” human eyeball is at an internal pressure of between 10 and 20 mmHg, which is a totally strange unit of measure that correlates to the pressure in an “inch of mercury.” In plainer terms, that pressure translates to between 5 and 10 pounds per square inch, or an average of 7.5 pounds. The standard pressure in a regulation NBA basketball? You guessed it: 7.5 Psi.