Double Rainbow

Rainbows are the result of refraction and reflection of light by water droplets. White light enters the water droplet and is refracted, and then is reflected off the back of the droplet. Before leaving the drop the light is split into several different colors, or again refracted. This is how a single rainbow is formed.
A second rainbow is produced when there is an extra reflection of light in the water droplet. Some light is always lost in the droplet, and therefore the second rainbow will be lighter than the first.
The reason that a rainbow is circular is because it is the only shape that will reflect back to your eyes at 42o (53o for a secondary rainbow). No two people see the same rainbow. The rainbows shape and position in the sky all depends on the viewers location and the angle of the sun.

This video, "A History of the Universe in Sound" by Honer Harger explains how we can use sound to increase our understanding of the universe. First of all, one has to understand that space has sound. It is not silent. The sun, Jupiter, and the rings of Saturn all make sounds. The study of astronomical sounds is called radio astronomy. Scientists use sensitive antennas and receivers to capture the sound. One can discover many things about space (scale/size, age, what it's made of) from listening to its sounds. The oldest noise ever heard was picked up in 1965 at Bell Lab. This cosmic radiation is evidence that the Big Bang existed.

This video "Light on Dark Matter" by Patricia Burchat is an explanation on the mysteries of the universe; dark matter and dark energy. In this video Patricia explains that ordinary matter (humans, planet, stars etc) make up only 4% of the universe. 26% is made up of dark matter and the rest (70%) is made up of dark energy. Surrounding a galaxy and surrounding a cluster of galaxies is a gravitational force called dark matter. It is a cloud that has mass. Light is involved in this concept as well. When looking at a galaxy, through a telescope or naked eye, you may be seeing it in a different place than it actually is. This could be because a clump of dark matter is obstructing your view. The light from the galaxy is bouncing around this matter and entering your eye at a different angle. Therefore we may see the galaxy in a different place than where it actually is!
Space is growing bigger and bigger. The distance between galaxies is getting greater. Instead of expanding at a slower rate, the rate is actually increasing. The universe is expanding at faster rate than it did billions of years ago. Dark matter pulls matter further apart and encourages expansion. Dark energy decreases gravitational pull and puts more space between the galaxies.

My Favourite Type of Light

There are many different types of light. You have radio waves (low frequency) up to gamma rays (high frequency). If I had to chose one that I would not like to live without I would have to chose "visible light." Visible light are the colours we can see. This makes up only a small part of the electromagnetic spectrum. With wave lengths of 10 to the power of -6 meters, visible light lands right in the middle of the electromagnetic spectrum. Without visible light we would not be able to see colour or light. Our vision would be restricted to black shadows and shapes as our eyes adjusted to the darkness. I think visible light, although not so vital to other animals, is a neccessary part of our lives and we would be very different without it.