How does sunset occur

The same information shown in Figure 7 is presented in Figure 7a, below, in the form of a polar plot of the position of the Sun in the coordinates of the azimuth and altitude of the Sun as seen by an observer at that latitude. Figure 8 and 8a show the apparent paths of the Sun as seen from Hawai'i, the southernmost State of the United States, 21 degrees north of the equator.

The paths are all parallel to each other, but are slanting at 21 degrees to the horizon. It will also be noticed that the horizon divides the total path of the Sun into equal periods only on the first days of spring and fall, i. In summer, the portion of the Sun's path above the horizon is much greater than the night portion, and the reverse is true in the winter.

This illustrates the geographical effect , which depends on the observer's latitude. A bead placed on one of the tracks simulates the Sun rising along the eastern horizon, travelong along the sky, and setting on the western horizon. Imagine a tiny version of yourself standing in the middle of the wooden disk. And imagine that the outside rim of the disk represents your horizon. On Summer Solstice, you would see the Sun rise on your "horizon" at the eastern point of the longest track. It would follow the track high in your sky, and eventually set on the western horizon.

It would be up for about 17 "hours", thus making summertime days long and warm. On the Winter Solstice, you would observe the Sun rising at the western end of the smallest track.

It wouldn't rise high in the sky, and would be up for only about 6 or 7 hours, making your days short on daylight and cold. At the Spring and the Fall equinoxes, the Sun would rise at the east end of the middle track and set at the west end. Build your own Sun Track Diorama What about the stars? The rising points of the stars don't change as much as the Sun's because they are so very far away. So the rising points of stars on the horizon were not as critical to ancient cultures.

Robustness to scattering is a common requirement for communications and for imaging Why electrons can even be ejected from an They have produced light sources that for the first time emit high-intensity light in only one direction.

This reduces scattering Print Email Share. Living Well. View all the latest top news in the environmental sciences, or browse the topics below:. Keyword: Search.