- 2673 - EYE TRICKS - Your Eyes are Playing Tricks? - Your eyes are how you perceive the outside world. But, what you see does not exist in your eyes. Your eyes are the detectors that send data to your brain. What actually exists as an image is in the occipital lobes of your brain. In a very real sense there is no outside world, everything that exists for you is inside your head.
-
-
--------------------- 2673 - EYE TRICKS - Your Eyes are Playing Tricks?
-
- The eyes are detecting and sending to our brains just a very, very small part of the radiation data that exists in the outside world. The environment is packed full of radiation, electromagnetic radiation. Radio waves, microwaves, infrared rays, red light, blue light, ultraviolet radiation, X-rays, gamma rays are all over the place. They are all filling the same space that you can see.
-
- What would it be like if we could stair out the window and see all the radiation that is out there. It would be information overload for sure. The wavelengths of radiation that we can detect with instruments extends from miles long down to nanometers in length (10^6 meters to 10^-12 meters) with visible light wavelengths only 400 to 700 nanometers (4*10^-10 meters).
-
- The retinas in your eyes have two kinds of detectors, cones and rods. Images from the outside world are focused through your pupils onto the fovea, the center spot of the retina.
-
- There are 8,000,000 cones in the center of your retina. Cones work sort of like prisms, due to their triangular shape they are sensitive to different wavelengths of light, in the 400 to 700 nanometer range. Therefore, cones see colors from blue to red. But, cones require bright light. They do not work well in dim light.
-
- Around the fovea are 20,000,000 rod shaped cells. Because of their cylindrical shape they can not distinguish colors. But, they work well in dim light . Rods are 15 degrees to 20 degrees from the fovea center. Cones cover 1 degree in the center.
-
- So, in dim light we suffer from a 1 degree blind spot in the center of our eyes. However, we can see quite well with “averted vision“. Look 15 degrees away from the object and in dim light you can see it better, but only in black and white. Your color vision is gone in dim light.
-
- In fact, rods are totally blind to red light. Check out the Christmas tree lights next time. Put a dimmer on the lights and slowly turn the brightness down. At some point colors vanish and you only see gray lights. At that point your cones no longer work and you rods are seeing the gray lights.
-
- However, the red-lights will disappear entirely. We can not see dim red light, even as gray. Also, if a dim object is smaller than one degree it vanishes when we look at it directly. Only averted vision can pick it up.
-
- Cones respond quickly to bright light but rods respond slowly to dim light. It can take up to 20 minutes for you eyes to acquire night vision sensitivity. Almost everything in the night sky and through the telescope requires night vision sensitivity.
-
- Once acquired night vision is 10 times sharper than daylight vision. That is the reason galaxies appear as a smudge of light and the full Moon appears sharp with lots of detail.
-
- That is the great thing about CCD’s. Charge Coupled Diodes can continue to accumulate photons to acquire an image over time. Even in the dimmest light, stair at one spot with a long enough time exposure and every object becomes visible. Hubble’s Deep Field view of far away galaxies took a time exposure of 400 days.
-
- Use your averted vision to see objects in the night sky. The Beehive Cluster (M44) will first appear as a blob, a nebula. With averted night vision normal eyesight can resolve individual stars.
-
- It’s weird, and takes practice, but in dim light the clearest vision materializes only when you don’t look at it.
-
- That is an eye trick for you.
-
- March 18, 2020 780 2673
----------------------------------------------------------------------------------------
----- Comments appreciated and Pass it on to whomever is interested. ----
--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
-- email feedback, corrections, request for copies or Index of all reviews
--- to: ------ jamesdetrick@comcast.net ------ “Jim Detrick” -----------
- https://plus.google.com/u/0/ -- www.facebook.com -- www.twitter.com
--------------------- Saturday, March 21, 2020 --------------------
-----------------------------------------------------------------------------------------
No comments:
Post a Comment