ANATOMY—-THE INCREDIBLE HUMAN EYE
Hey everyone! Hows it going out there? Super fine and super busy for me and my family! My adopted daughter is about to have her baby, we are helping our adopted son to find work, church life is busy, and there is all the outside work associated with spring weeds and all the beautiful spring flowers are coming up…so much to do and see!
And what makes all of this as easy as possible? Being able to see with our amazing eyes. Let’s take a deeper look at what our eyes and the eyes of other creatures can do…
Our eyes are an organ that reacts to light and has several different functions. This includes vision differentiations such as light perception, color distinctness and depth perception. Dr. George Marshall, Ph.D. in Ophthalmic Science at Glasgow stated for the March-May 1996 Creation magazine, “The more I study the human eye, the harder it is to believe that it evolved. Most people
see the miracle of sight. I see a miracle of complexity on viewing things at 100,000 times magnification. It is the perfection of this complexity that causes me to baulk at evolutionary theory…The retina is probably the most complicated tissue in the whole body. Millions of nerve cells interconnect in a fantastic number of ways to form a miniature ‘brain’. Much of what the photoreceptors ‘see’ is interpreted and processed by the retina long before it enters the brain.” To put in simple terms, our eyes actually function much like a digital camera. For example:
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| Dr. Marshal, a researcher of eye diseases from the University of Glasglow, Scottland (photo from AIG) |
“1. Light is focused primarily by the cornea—the clear front surface of the eye which acts like a camera lens.
“2. The iris (colored parted of the eye surrounding the pupil) functions like the diaphragm of a camera, controlling the amount of light reaching the back of the eye by automatically adjusting the size of the pupil (by dilation-like an aperture in a camera).
“3. The eye’s crystalline lens is located directly behind the pupil and further focuses light. Through a process called accommodation, this lens helps the eye automatically focus on near and approaching objects, like an autofocus camera lens (and helps us with depth perception).
“4. Light focused by the cornea and crystalline lens (and limited by the iris and pupil) then reaches the retina—the light-sensitive interlining of the back of the eye. The retina acts like an electronic image sensor of a digital camera, converting optical images into electronic signals. The optic nerve then transmits these signals to the visual cortex—the part of the brain that controls our sense of sight.”1
and 5. Cones are a type of photoreceptor that are tiny cells in the retina (the sensory membrane that lines the back and sides of the eye receiving images then converting the images to signals that reach the brain via the optic nerve). These cones (an amazing 6 to 7 million mostly concentrated on a 0.3 millimeter spot on the retina) pick up reflected light from everything we see and sends off singles that the brain then interprets as varying shades of colors.
As a matter of fact us humans can see about 7,000,000 shades of color. Amazing! That’s because we have three different types of cones. But as fantastic as that is, some animals have us beat. Many birds and fish possess four types of cones which allows them to see ultraviolet light—a wavelength shorter
than visible light. Hmmm, now aren’t humans supposed to be at the top of the evolutionary chain? Then how can birds and fish, which by the evolutionary tree definition, are less developed than humans, have more complicated and better eyes than us?
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| Depiction of a bird’s eye |
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| What birds see that we don’t! |
Oh…and then there are the insects, another much lower branch of the evolutionary tree. They too can see the ultraviolet spectrum enabling them to see patterns of flowers which are completely invisible to us. Why wouldn’t the most highly “evolved creatures” (humans) have ultraviolet vision? After all, it certainly would make it easier for us to avoid flowers with ultraviolet patterns that attract bees. And considering 8 percent of humans are highly (fatally) allergic to bee stings and another 32 percent are allergic on some
Until next week, God bless and take care,
Willow Dressel
This week in the night skies; For the southern skies there has been some geomagnetic activity this past week which produces auroras…keep your eyes open because there may be more nights of this. Also you may still be able to see a few lingering Lyrid meteors. "The Lyrids, the debris of comet C/1861 G1 (Thatcher) are a weak but reliable shower that occurs every year between April 16- April 25, with the peak this year around 24 hrs UT on April 22.”2
For the northern hemisphere; "Monday, April 27 The waxing gibbous Moon shines under Regulus this evening, as shown here.
Among Jupiter's moons, telescope users in the western half of North America can watch the shadow of Io eclipse Europa from 10:59 to 11:02 p.m. PDT. At mid-eclipse, Europa will be dimmed by 1.4 magnitudes.
(Now that Jupiter is far from opposition, we see shadows in the Jovian system falling far enough sideways that an eclipsed satellite and its eclipser appear widely separated in a telescope's view. So we can see the eclipsed satellite dimming by itself, uncontaminated by the light of the eclipser. The tables in Sky & Telescope for these events presume that the two satellites appear blended and give their combined magnitude. See Bob King's article Catch the Last Best Antics of Jupiter’s Moons.)
References:
www.experts123.com/q/what-is-the-percentage-of-people
2http://astroblogger.blogspot.com
http://www.skyandtelescope.com/observing/this-weeks-sky-at-a-glance-april-24-may-2/
2http://astroblogger.blogspot.com
http://www.skyandtelescope.com/observing/this-weeks-sky-at-a-glance-april-24-may-2/
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