A World Without Rainbows?
by Wayne Anderson
The following article is from Free
Inquiry magazine, Volume 21, Number 3.
And God said, This is the token of the covenant which I
make between me and you and every living creature that is with you, for
perpetual generations: I do set my bow in the cloud, and it shall be for a token
of a covenant between me and the earth. Genesis, chapter 9, verses
One of the difficulties in adopting a literal
interpretation of the Bible is that you can wander off into some pretty strange
territory. Take, for example, the Genesis quote above. In it, God promises Noah
that he will never again drown the world and seals his promise by creating the
rainbow. Interpreted as a just-so story, it is a poetic little myth accounting
for a beautiful natural phenomenon. Taken literally, however, it leads Christian
fundamentalists into trouble.
For the symbol of God’s promise to mean anything, we must
assume that rainbows did not previously exist. The necessary ingredients for a
rainbow are light and water droplets suspended in the air, which breaks down the
light into different colors. Since rain, a natural occurrence, did not seem to
startle Noah or his contemporaries, it seems safe to assume that rain drops
existed before the Flood. We know that light already existed from verse 3 of
chapter 1 of Genesis, and God’s reference to the “green herb” just before
the rainbow covenant implies the presence of color. Therefore the necessary
ingredients were already present before the Flood, but they failed to make
A rainbow is created when sunlight enters water droplets in
the air. The different wavelengths (colors) of the light have slightly different
refractive indices in the water. This difference causes each wavelength to bend
through a slightly different angle in the drop, thereby dispersing the light
into its component colors.
For a rainbow not to be formed, the light must not have
been dispersed by the water. But this dispersion is caused by the interaction of
the electromagnetic waves of the light with the electrical charges in the atoms
of the water, a process governed by the laws of electromagnetism and quantum
mechanics. The appearance of a rainbow after the flood implies that God had
suddenly altered the fundamental laws of nature. But these laws affect much more
than water droplets. They also determine the structure of the atoms. Changing
the natural laws would therefore change the atoms, which would in turn affect
the light they give off. As is well established by observation, each atom gives
off its own unique set of wavelengths of light, called the “spectrum” of the
atom. Atomic spectra in pre-rainbow times would have been different from those
in the post-rainbow era. Now we have a testable prediction.
The obvious place to look for this effect is in astronomy,
because, by viewing the light from ever-more distant stars, we are looking
backward in time. Light from sufficiently remote stars was emitted by
pre-rainbow atoms and has been traveling through space ever since. Therefore the
spectra of those distant atoms should differ markedly from the spectra coming
from nearby post-rainbow atoms.
When did the Flood occur? Establishing the date can be a
bit dicey, but the ever-resourceful Bishop Ussher put it at 2,349 b.c.e. or
4,348 years ago.1 Since Christian fundamentalists favor his age for the Earth,
adopting his Flood date should offend few.
Using Ussher’s calculation, we should find a sharp
discontinuity in the appearance of atomic spectra at a distance of 4,348 light
years. Light from more distant stars has been traveling for more than 4,348
years and hence came from pre-rainbow atoms, while light from closer stars
originated in post-rainbow atoms. Does such a discontinuity exist? Of course
not! Even if we try other reasonable dates for the Flood, we never find such a
What does this little exercise tell us about the Bible? Not
much, except not to take it literally. Will it convince hardcore Christian
fundamentalists? Forget it!
1. This date comes from The Mound Builders by Robert
Silverberg (Ohio University Press, 1986), p. 59.
Wayne Anderson teaches physics and astronomy at Sacramento
City College. He has written on pseudoscience in Skeptical
Inquirer and the New York Times.