The Location of the Sun
At different times of the year, the sun appears at different locations at the same time of the day. Although it is quite easy to locate these positions during the course of the day, it is difficult to locate the differences between weeks or months. Different factors affect the position of the sun when viewed at the same time and at the same place year long.
Effects of Earth Motions
Rotation– the earth rotates at 15o per hour. This is equivalent to complete rotation within 24hrs. Rotation of the earth causes the sun to move in an arc across the sky (Denecke & Carr 46). As the earth rotates on its axis, the sun appears to move from East to West. As a result, at sun rise (6 A.M) an observer in the North Pole positions the sun to the east and low in the horizon.
At around 9 A.M. when the earth has rotated 45 degrees, the sun has moved to the south East and is much higher up in the sky. At 12 noon, the same observer will realize that the earth has rotated another 45 degrees from the west to East and the sun is now to the south and above the horizon. At 3 P.M., the sun appears at the southwest and is much lower in the horizon than at noon.
The sun finally set to the west and low in the sky. In Allentown PA, for example, the sun will never be directly overhead. On the first day of winter, the sun appears far down south of the equator and it is seen at an altitude of 26o at noon.
On the first day of summer, the sun takes 15 hours to cross the sky and finally sets in the North West. This ultimately affects its position when viewed from the town. This makes the sun change daily in its rise and set with respect to the horizon.
At the poles, at the beginning of spring, the sun only rises to 0.4 degrees into the sky everyday taking 30 hours at sunrise. The sun set also takes 30 hours as it moves around the horizon. This means that if you turned towards the sun all this time, you will have moved your head 360 degrees.
Someone viewing the sun from the Netherlands and Belgium, the sun is seen from the south; consequently, if you are in Australia, the sun is due north. The sun will be overhead to someone in the equatorial region.
Revolution
Assuming that the months of the year are on an axis, January in the beginning and December at the end of the axis, and the hours of the day placed on a vertical axis. The earth revolves around the sun once a year. The length and the position of the suns path are dependent on the seasons and latitude.
Because suns path determines the length of time that sunrays reach the earth, a longer sun path mean a longer time is taken to reach the earth and consequently a longer day. This path also determines the position of the sun in different parts of the earth.
When observed on different days, an observer will notice that the earth follows paths that are different. This arises because the sun’s position changes in response to the changes in the earth’s orbit.
In December, a person observing the sun from the US will realize that the sun is south of East and sets on south of west. In June, the sun rises at the North of East and sets at the North of west. It also rises very high at noon. This results in very long daylight.
During the Equinoxes in March and September, the sun rises due east and sets due west. The days are as long as nights. In December and in June, the suns path is much longer as days go by and the sun is even higher in the sky.
Summer solstice (sun stop) occurs in June 21 when the altitude of the sun ceases to increase. As December approach, the sun’s path becomes progressively shorter with the altitude of the sun at noon decreasing.
Precession
This is an alteration in the orientation of the rotation axis of the earth. The Earth’s rotation is not fixed in space. It slowly executes a slow precision over a period of 26000 years. This motion may not necessarily exert any visible changes in the location of the sun.
Can You Locate The Anti-Solar Point? Where Is It?
The anti-solar point is the point at the extreme end of the shadow 180o away from the sun. The anti-solar point keeps on changing depending on the position of the sun. When the sun is high up in the sky, the anti-solar point falls below the horizon, when the sun has already set, the anti-solar point appears above the horizon (Beeson & Mayer, 106).
The anti-solar point helps predict where the rainbow is likely to form. This is because the colored light from the raindrops exit from the raindrops at particular angles measurable with respect to the anti-solar point.
The presence of a rainbow in the sky is an indication that raindrops at 40.6o and 42o from the anti-solar point are present in the sky. These raindrops reflect colored light onto our eyes. On a rainbow, the anti-solar is on the outer rim.
What Color Is At The Top Of The Rainbow, Red Or Blue?
Rainbows are formed during rainy seasons as a result of the refraction and total internal reflection of rays falling on suspended water droplets (Singh 110). The different colors appear when sun’s rays hit rain drops, the rain drop then disperse the light and the different colors emerge due to internal reflection and refraction seen by the human eye.
An observer is then able to see different colors of the spectrum at different angles. To see the rainbow, the sun must be behind you, the center of the rainbow is opposite the sun while the rain droplets are in the direction of the rainbow.
Traditionally, it has been common description that the rainbow is made up seven colors; Red, Orange, Yellow, Green, Blue, Indigo, and Violet. The red is said to be at the top. However, in the actual sense, the rainbow is a whole continuum of colors from red to violet and beyond.
Colors of the rainbow are based on two facts;
- Sir Isaac Newton, in 1666, discovered that sunlight is made up of a wide range of colors that when combined looks white to the human eye.
- When light of different colors pass from one medium to another, it is reflected in different amounts.
This aspect of bending of light (refraction) as it traverses media of different densities was determined by Descartes and Willebrord. If one traces the paths of red and blue light in a rain drop, it becomes clear that the angle of deviation is unlike for both the colors. Blue tends to be refracted more than the red light.
Therefore, when looking at a rainbow, what we see is reflection and refraction of light by different raindrops. Some of these raindrops are viewed at 42 degrees while others are viewed at an angle of 40 degrees. The 42 degrees is the angle of deviation between the incoming light rays from the sun and that refracted onto the observer’s eyes for the red light.
The angle of the blue light, which is made up of shorter wavelengths, is less than that of the red light meaning that it appears in the base of the rainbow. These angles are in relation to the suns original ray. The blue color thus appears in the inner circle while the Red appears at the top.
Conclusion
The location of the sun depends on the motions of the earth and changes depending on location, time of the day, and time of the year. The color at the top of the rainbow is red although in the actual sense, the rainbow is made up of a continuum of colors.
The anti-solar point appears at 180 degrees opposite the sun. In a rainbow, this point appears at the farthest end of the sun’s rays and thus occurs at the tip of the rainbow.
Works Cited
Beeson, Steven, and Mayer James. Patterns of Light: Chasing the Spectrum from Aristotle to LEDs. New York: Springer, 2008. Print
Denecke, Edward, and Carr William. Let’s Review: Earth Science. Hauppauge NY: Barron’s Educational Series, 1995. Print
Singh, Ajay Pratap. Excel With Fundamentals Of Physics Vol.I – Optics. New Delhi: Golden Bells, 2008. Print