At URJ 6 Points Sci-Tech West we aim to use science and technology as a portal through which to connect with Judaism. This week, we read the story of Noah’s Ark—the big boat, the flood, the animals and of course the meteorological phenomenon of reflection, refraction and light dispersion. We Jewish scientists love the part about the rainbow!
Light is many colors
Light from the sun and many artificial sources might appear white to our eyes, but it is actually made up of light with many different wavelengths, which our eyes interpret as many colors. When light is bent (we’ll get to that below), the different wavelengths that make up the white light cause different colors to bend at different angles and those variations in the angles create the spread of colors in the spectrum that we see as a rainbow.
What makes light bend?
Light bends, or refracts, when it passes through certain transparent material such as glass, plastic or water. Each material has a different refractive index characteristic to that material, which is a ratio of how fast light travels in a vacuum compared to how fast light travels through that specific, more dense material. It’s the difference from one refractive index to another at the interface of the two materials that the light is passing through — from air to water and back to air in this case — that causes the light to bend. This bend of the light, or refraction, separates the wavelengths of light (each wavelength bends at a different angle) into the rainbow that our eyes can see.
What is this doing in our story?
This part of the story is more reminiscent of a Greek origin myth than our Torah. It is likely that this entire narrative was borrowed from our Mesopotamian neighbors, but that is for a different blog post! We know the rainbow is supposed to be a sign of God’s promise never to destroy the Earth again, but a close read will show that this is actually a reminder to God to help God remember; not a reminder to us. Why an omnipotent and omniscient God needs a reminder is a topic for a different day. As science-lovers, its clear why a rainbow is a reminder of how spectacular and miraculous the Earth is.
The size of the raindrop must be just right. The angle of the light must be just right. There can’t be too many clouds. Sometimes it is so dim, we can barely see it, other times it is dazzlingly bright. One water droplet can have a refraction and a reflection of that refraction to create a double rainbow! A clear reminder, indeed, that science is awesome and we are surrounded by our miraculous world.
To learn more about rainbows, check out this video.