Blue skies remind us of God’s grace bestowed on all mankind. The beautiful canopy of blue means a good day at the beach or great weather for a barbecue. But why is the sky blue and not green or purple? Without an atmosphere, daytime would consist of the bright sun against a black sky. There would be no heat, instead of mere sunburn you would get x-ray radiation poisoning, and we’d have no oxygen to breath. Such an earth would be inhospitable to life. God, in His grace, provides layers of covering for us including the atmosphere, the magnetosphere, and the orbital geometries of our solar system which ensure a stable distance from earth to the sun. Each layer secures our safety and security so we can grow crops, drink water, and gaze out at the garden in the early evening and watch the sun set. Everyone enjoys this common grace and I think the error many people make is to presume they are entitled to this grace and may even attribute it to ‘mother nature’ or just plain chance formation of the universe. As if hidden in plain sight, God has given us fantastic evidence of His grace in a finely tuned universe that creates just the right conditions for us to live on earth. Though the evidence of a designer is all around us we do not see. This is one aspect of what Jesus meant when He said to the disciples “Having eyes, do you not see?” (Mark 8:18). It’s not that some lacked the sense of hearing; rather, their hearts were hardened. Nonetheless, appreciated or not, God sheds His grace on all mankind, all the time.
Blue skies are one evidence of this common grace and under them we grow crops, sunbathe, and watch baseball games. When sunlight hits our atmosphere, light explodes off trillions of nitrogen and oxygen molecules scattering light in all directions. The sky lights up in all directions in the way that God’s grace abounds to every man, woman, and child, whether they know Him or not. In the absence of an atmosphere the sky would remain black – just look at pictures of the astronauts on the moon back in 1969 to see the blackness all around them. God is light and the scattering of light enveloping us in all directions bathes us in His presence and mirrors His omnipresence. His grace explodes on the scene every time the sun rises, and this is why I love the hymn Great is Thy Faithfulness, by Thomas Chisholm, with the refrain “Morning by morning new mercies I see”. We endure the darkness of the night knowing that God will rescue us. What a picture sunrise is of His enduring grace!
But why blue? A scientist who lived long ago, named Rayleigh, discovered that light scatters much more toward the blue end of the spectrum than the red. In fact, Rayleigh scattering is proportional to the inverse of the wavelength raised to the fourth power. The short blue wavelengths scatter a lot, but the longer reds not so much. Since blue wavelengths scatter more, the sky lights up blue. The red skies at sunset and sunrise happen because, with the sun low in the sky, light must travel farther through the atmosphere before it reaches you but by then the blue light is mostly scattered away leaving predominantly red wavelengths of light. Light scattering doesn’t stop in the sky but scattering of sunlight and skylight find their way in your windows and the cracks around your door. It is everywhere. North of the arctic circle where darkness lingers for months in winter with no sun takes a psychological toll on residents there. Even the darkest corners of earth (metaphorically, as in most sinful) still enjoy a measure of God’s grace which should give you pause when contemplating the true horror of hell where there will be no grace whatsoever. Those in hell will experience the complete absence of God’s grace and presence for eternity. We need God’s grace and mercy. Please do not take His grace for granted. Today is the day of salvation. Jesus has made the way of salvation with His death on the cross where He paid the penalty for your sins and mine. Let the Light into your life and embrace Jesus as your substitute who takes the wrath of God away from you and onto Himself! After all, the common grace He shows you is intended to lead you to repentance not complacency.