Rainbow is a representation of the visible light spectrum. It requires rain and Sun to be seen.
Visible light coming from the Sun, comes at different colors mixed with each other. If you pass that light through a prism, the different colors are separated and you can see a range of colors from red to violet. Rain droplets can serve as a prism, and break up visible light into its different colors.
The first instance of the rainbow is recorded in Genesis 9:12-15.
“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: 13 I have set my rainbow in the clouds, and it will be the sign of the covenant between me and the earth. 14 Whenever I bring clouds over the earth and the rainbow appears in the clouds, 15 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.“
A rainbow is a very good thing to see, as it is our gaurantee that our planet will not face another worldwide flood again.
One thing that dawned on me recently is that the rainbow is sort of a confirmation that there was no rain before the Flood. I've heard of the theory about no rain before the Flood from a number of creation scientists. It's called the water canopy theory. But I was wondering where they got that from. It does say in Genesis 2:5 that there was no rain at least at the time of creation. There was another mechanism that watered the earth. But for how long did that mechanism was at work? And how could there be no rain?
Rain and other precipitation is driven by the Sun. As the Sun heats up the Earth, it causes water on the surface of the Earth to evaporate. This leads to build up of water vapor in the atmosphere which then falls back to the ground by means of rain happening today or "mist" mechanism present at the time of creation. The difference between today's rain and the previous mist mechanism, is that water vapor before didn't seem to accumulate into clouds. From what Genesis 2:5 says.
For rain to happen, you also need wind. Collision of cold air and warm air is what causes real rain. So for rain to not happen, there would have to be no such cold air/warm air collisions. Which means the air temperature would have to be uniform throughout the Earth. And the only way that could have been achieved is if there was some sort of a water shield around the Earth. Such shield would make the entire Earth like a giant greenhouse, keeping the air everywhere at room temperature.
Just some ramblings caused by thinking about the rainbow phenomenon.
Image credit: Eric Rolph