No Rainbows before The Flood?

No Rainbows before The Flood?

A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multi-colored arc. Rainbows caused by sunlight always appear in the section of sky directly opposite the sun. The traditional description of the rainbow is that it is made up of seven colors - red, orange, yellow, green, blue, indigo, and violet.

 Actually, the rainbow is a whole continuum of colors from red to violet and even beyond the colors that the eye can see. A rather beautiful sight to observe on a bright day. The colors of the spectrum of white light are violet, indigo, blue, green, yellow, orange and red (VIBGYOR). The white light is a mixture of different colors. Each color is associated with light of a particular wavelength. The red light has longer wavelengths than the blue light.

 
When sunlight encounters a raindrop, part of the light is reflected and the rest enters the raindrop. The light is refracted at the surface of the raindrop. When this light hits the back of the raindrop, some of it is reflected off the back. When the internally reflected light reaches the surface again, once more some is internally reflected and some is refracted as it exits the drop. 

According to The Bible, God created the rainbow as a sign after the struggles of Noah.

“Then God said to Noah and to his sons with him: "I now establish my covenant with you and with your descendants after you. and with every living creature that was with you--the birds, the livestock and all the wild animals, all those that came out of the ark with you--every living creature on earth. I establish my covenant with you: Never again will all life be destroyed by the waters of a flood; never again will there be a flood to destroy the earth." And God said, "This is the sign of the covenant I am making between me and you and every living creature with you, a covenant for all generations to come: I will place my rainbow in the clouds, and it will become a guarantee of the covenant between me and the earth.” Whenever I bring clouds over the earth and the rainbow appears in the clouds, I will remember my covenant between me and you and all living creatures of every kind. Never again will the waters become a flood to destroy all life. Whenever the rainbow appears in the clouds, I will see it and remember the everlasting covenant between God and all living creatures of every kind on the earth." So God said to Noah, "This is the sign of the covenant I have established between me and all life on the earth."
(Genesis 9: 8-17) 

The rainbow was an established promise for the people of Noah and for all the generations to come. Biblical commentators argue that this is not a blanket-statement implying that there has never been an occurrence of a rainbow. However, when one empirically analyses the text, free form all prejudice self-fulfilling and previous-existing notions. God declared that it was a sign he was establishing between Noah and “for all generations to come.” Does this not objectively signify that the presence of a rainbow was seen before? If an individual argues against this. Then why would God give them a “promise” and “sign” of something they have already seen before? Otherwise it would not have been classified it as a sign and is utterly non-sensible to claim so. 

Established by definition is: set up on a firm or permanent basis.

In conclusion:

The rainbow was set up as a promise for Noah and all future generations while also being a Reminder for God not to cause an extinction of the human race (as discussed here). However, rainbows are mainly caused by the reflection of sunlight. The best rebuttal provided by Biblical Scholars so far is that rainbows were “obviously seen prior to the flood”. But the points provided here will further render them weightless objections.