Thursday, May 26, 2011
Tuesday, May 24, 2011
Friday, May 20, 2011
How are Rainbows formed and Why did people in Ireland believe there was gold at the end of rainbows
Rainbows are formed when light hits droplets of rain. Each droplet acts like a prism, splitting the light into different colors, each of which is bent at a slightly different angle. That's what forms a rainbow. Because the light source, the sun, is a circle, and because light travels in a straight line, the rainbow is a circle as well. In order for the sun's rays to refract so we can see them, the sun has to be within 42 degrees of the horizon either rising or setting. That's pretty low, which means we can never see the full circle of a rainbow - we just see the top part of the arc. As far back as the 17th century, the Irish understood this. And they were fond of saying that one was as likely to find a pot of gold as to find the end of a rainbow. The people knew that we can't see the complete circle of the rainbow, and that we only see a portion of it, in the shape of a bow. The expression somehow changed and became a part of fairy mythology. |
Thursday, May 19, 2011
What and how are Fire Rainbows Created.
A fire rainbow is an extremely rare phenomenon that occurs only when the sun is high, allowing its light to pass through high-altitude clouds which have to contain high amount of ice crystals.'Through years of observation and study, meteorologists have discovered the exact conditions that give rise to a fire rainbow or CHM. For a fire rainbow to form, the Sun is always high up in the sky. Also cirrus clouds have to be present,which have a lot of present ice crystals. It is important that you are at the right location to be able to see the fire rainbow: the position of the Sun faced to you and its altitude decides it. "It is a known fact, that fire rainbows are not visible at positions north of 55 degree North latitude or South of 55 degree south latitude."Fire Rainbows occur mostly around summer solstice.
What are Moonbows and how do they form?
A rainbow is cause by the sun shining o moisture droplets, most commonly after a rainstorm. Rainbows contain many colors and are the most common.
The moon is the key, just as sunlight produces rainbows during the day, moonlight can produce rainbows at night. This is a lunar rainbow or 'moonbow'.
Moonbows are rare because moonlight is not very bright. A bright moon near to full is needed, it must be raining opposite the moon, the sky must be dark and the moon must be less than 42ยบ high. Put all these together and you do not get to see a moonbow very often! "To the unaided eye they usually appear, as in the small image, without colour because their light is not bright enough to activate the cone colour receptors in our eyes. Nonetheless colours have been reported and might be seen when the moon is bright."
Moonbows are rare because moonlight is not very bright. A bright moon near to full is needed, it must be raining opposite the moon, the sky must be dark and the moon must be less than 42ยบ high. Put all these together and you do not get to see a moonbow very often! "To the unaided eye they usually appear, as in the small image, without colour because their light is not bright enough to activate the cone colour receptors in our eyes. Nonetheless colours have been reported and might be seen when the moon is bright."
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