How does Skyclock work?
Skyclock shows relative specific solar time. That is, using the current date, sunrise and sunset times, and a specific location, Skyclock calculates and displays daylight, slice-of-pie twilight, and night. Sunrise and sunset times are based on calculations, or algorithms, that result in a large set of tables. The facts have been checked for hundreds, if not thousands of years, going back to the Egyptians, who had a 365 day calendar. We know when sunset occurs for a specific place on a certain date. Our ancestors watched and marked and measured, so that today we can predict where the sun is—we know its hour angle for any place if we know the date. What we know is transient, or dynamic, because the earth s surface is in constant motion. Four solid facts combine to inform when sunset and sunrise occur: • the date (relative) • the location (specific) • the hour angle of the sun (solar) • the time (time) Twilight is then displayed as a distinct pie-shape on an analog face between blue (day)
