The wonder isn't so much that the sky is blue. The wonder really is that the sky is bright. Why shouldn't the sun appear as an intense white light surrounded by the blackness of space each day, like a flashlight suspended inside a box painted flat black? The daytime sky is bright and blue because of our atmosphere. Molecules of gas briefly absorb the highest energy wavelengths of light from the sun (the blue wavelength) and then bounce the blue light outward to our eyes. By the way, this is why the sun appears yellow...due to the absence of blue. Viewed from beyond our atmosphere, like from the space shuttle, the sun appears white, like any star's light. Just as the molecules of gas in our sky absorb energy from the sun, before bouncing that energy around to brighten the sky, so we as trusters of Christ receive the light from His spirit. We are illuminated, ourselves, and we brighten our world by passing the energy of His presence outward. This life would be dark indeed without His light running in and through us. It also gives rise to color as a yellow sun and a blue sky lead to a green earth. And so the indwelling illumination of our Lord's light paints our lives with rich color and warms our world.
Somehow I don't believe this is all a matter of chance or fortunate science.
Genesis 1:3-4 And God said, "Let there be light," and there was light. God saw that the light was good, and He separated the light from the darkness.
Job 38:19 "What is the way to the abode of light? And where does darkness reside?"
Psalm 36:9 For with you is the fountain of life; in your light we see light.