(Adapted from the author’s The Genesis Account. A theological, historical, and scientific commentary on Genesis 1–11.
After the Flood, Noah and all the Ark’s human and animal passengers disembarked. Then God made the Noahic Covenant. Then, as the historical account reads, God provided a sign for His covenant with Noah’s family and all living creatures—the rainbow:
And God said, “This is the sign of the covenant that I make between me and you and every living creature that is with you, for all future generations: I have set my bow in the cloud, and it shall be a sign of the covenant between me and the earth. When I bring clouds over the earth and the bow is seen in the clouds, I will remember my covenant that is between me and you and every living creature of all flesh. And the waters shall never again become a flood to destroy all flesh. When the bow is in the clouds, I will see it and remember the everlasting covenant between God and every living creature of all flesh that is on the earth.” God said to Noah, “This is the sign of the covenant that I have established between me and all flesh that is on the earth.” (Genesis 9:12–17)
Coming from the sun shining through the dark clouds, the rainbow symbolized the heavenly pervading the earthly. And as it spans the horizon, it reminds man that God’s covenant is universal, as was the Flood that will never recur.1
Although the rainbow is a spectacular sight for man, the assurance we have that there will never be another global flood comes from God. He is the one who will ‘remember’ His covenant. Note that God ‘remembering’ doesn’t mean that he had previously forgotten; rather, it is an idiom meaning that the rainbow would signify that He is acting again on behalf of the Covenant beneficiaries, ensuring that no subsequent flood would become global.
Rainbows before the Flood?
The Noahic Covenant was certainly the first mention of the rainbow. But the Bible is silent on whether they had previously occurred. However, there are some considerations that suggest there would have been rainbows, which will be addressed in turn: the science of the rainbow, the natural laws that operated before and after the Flood, and God’s sovereign authority to ordain meanings to phenomena.
The Science of the rainbow
Rainbows are the result of well-known physics. When light enters at an angle into a substance where it travels more slowly (like a prism),2 different wavelengths are bent differently. This effect is called dispersion. Since colour depends on wavelength, we see this as a band of different colours. The shorter wavelengths (violet and blue) are bent the most, the longer wavelengths (red and orange) are bent the least.
The great creationist physicist Sir Isaac Newton experimented on dispersion by glass prisms. His experiments demonstrated that colour is a property of the light itself; coloured objects don’t generate colour, they absorb or reflect light that is already coloured.3
Actually, the dispersion is continuous; we see coloured bands because of the design of our colour vision.4 Newton designated seven colours to the rainbow by analogy with the seven notes of the musical scale: red, orange, yellow, green, blue, indigo, and violet, hence the mnemonic initialism ROYGBIV. But there are different designations and numbers of colours. For example, I don’t see ‘indigo’, but sometimes see a small band of blue-green (also called ‘aqua’, ‘cyan’ or ‘turquoise’).5 Actually, the difference might be with the names we give colours—one author suggests:
A careful reading of Newton’s work indicates that the color he called indigo, we would normally call blue; his blue is then what we would name blue-green or cyan.6
Also, dispersion can be produced from water drops, including rain. The drops also reflect the light, so we normally see rainbows only if we are between the sun and the raindrops. The reflection also explains why the sequence seems reversed: violet on the inside and red on the outside. Yet we can also see smaller rainbows with mist and sea spray.
Natural laws did not change
God mainly used natural causes in the preservation of Noah and the animals e.g. Noah had to build a wooden Ark; the cause and rise of the Flood—fountains of the great deep plus 40 days of rain; and its abatement—a wind, and continents rising and ocean basins sinking. This suggests a continuity between ‘natural laws’ before and after the Flood.
There is simply no evidence from the biblical text that natural laws functioned so differently that dispersion of light would not have occurred before the Flood. Rather, what the text does say suggests that there was no difference in the natural laws. Also, natural laws are our description of God’s normal, repeatable ways of upholding His creation, while miracles are His extraordinary means.7 So if rainbows were not produced, we would need to deduce that God was actively preventing dispersion. There is not the slightest evidence in the text for this.
Applying a new meaning to an existing phenomenon
Calvin, commenting on “I have set my bow in the cloud” (9:13), said:
From these words certain eminent theologians have been induced to deny, that there was any rainbow before the deluge: which is frivolous. For the words of Moses do not signify, that a bow was then formed which did not previously exist; but that a mark was engraven upon it, which should give a sign of the divine favor towards men. … Hence it is not for us to contend with philosophers respecting the rainbow; for although its colors are the effect of natural causes, yet they act profanely who attempt to deprive God of the right and authority which he has over his creatures.8
There are other examples of existing materials or practices that God decreed to be a new sign. E.g., Jesus ordained the Lord’s Supper out of bread and wine. He declared that this was now to be a memorial to His sacrifice of His body and blood.