Teaching About Transparency
Glass is transparent, which means it allows light to pass it.
There are two reasons why glass is transparent. First glass has an amorphous body, which means that glass does not consist of crystallization. However metals, stones, and most types of material include crystalline bodies. Most of substances consist of two or more crystalline bodies. Incoming light is scattered at borders between two crystalline parts in such a substance. On the other hand, glass does not contain crystalline bodies like liquid.
(Diamond and quartz are made of single crystalline body, so that they can be transparent.)
Second, glass consists of silicon dioxides that do not absorb visible light rays. Incoming light to metal, a stone, or an ordinary substance surly hits an electron of an atom included in such a substance. Energy of the electron is increased when light hits the electron. But in most cases, the electron soon decreases its energy by discharging light whose wavelength is pre-determined and different than that of the incoming light. This discharged light is observed as reflected light to human eyes. If electrons of a substance energized by incoming light discharge only green light, it looks green to our eyes no matter if it is exposed to natural light.
So, in most cases, a substance cannot be transparent. But electrons of atoms composing a silicon dioxide molecule energized by incoming visible light discharge light with the same wavelength as that of the incoming visible light. If light hits an electron of a silicon dioxide molecule, the electron increases its energy but it soon discharges the light with the same wavelength to return to the original energy level, which means that virtually silicon dioxides composing glass do not absorb or retain incoming light. But, visible light is passed from one electron to another till it gets through the glass, though the propagation velocity of light through glass becomes slower.
In this way glass consisting of silicon dioxides is transparent, since it does not include crystalline parts, like liquid, and electrons included in atoms of its constituent silicon dioxides do not absorb and retain energy of visible light but relay it from one electron to another.
If a man has ability to see though minds of others, his ability must be like glass. Or, if a man has a mind like glass, he must be able to see truth of others.
Little children have a mind that is not crystallized yet and that does not include desire that obstacle straight propagation of truth. So, they can be taught well by God or angels.
Anyway, it is a miracle that some substances or some molecules and atoms in this world can be transparent to visible light. It must be extremely difficult to design silicon dioxides, diamond, and other molecules to become transparent at the beginning of the universe.
And, of course, if wave lengths of visible light for living things on the earth are different from the current ones, glass must look opaque even to the our eyes.
Crystalline Body Amorphous Glass
http://optica.cocolog-nifty.com/blog/2011/12/post-541a.html
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Joh 4:27 And upon this came his disciples, and marvelled that he talked with the woman: yet no man said, What seekest thou? or, Why talkest thou with her?
Joh 4:28 The woman then left her waterpot, and went her way into the city, and saith to the men,
Joh 4:29 Come, see a man, which told me all things that ever I did: is not this the Christ?