# Earth’s Rotation, Coordinates, Time Zones

### ROTATION OF EARTH

Earth has a circumference of 25,000 miles | 40,000 kilometers, rotates from west to east, to be more precise eastward. If viewed, from the North Pole it will appear to be in a counterclockwise direction. The North Pole or we call it Geographic/Terrestrial North Pole is located in the Northern Hemisphere, also known as the Arctic, a place where Earth’s axis of rotation exists, which is a distinct point from Earth’s Magnetic North Pole. The other point is the South Pole located in Antarctica. Earth is not a true sphere. It is in fact Oblate Spheroid. It means there are two axes, which is the Minor Axis which runs between Earth North Pole and Earth South Pole, also known as Polar Diameter, whereas, the Large Axis runs between Earth West to East, also known as Equatorial Diameter. Larger Axis or Equatorial Diameter is greater than Minor Axis or Polar Diameter, that is, the Polar Diameter equals 6356.77 km, while the Equatorial Diameter equals 6378.16 km. The difference is 21.39 km. The Earth rotates about its Polar Axis which is also inclined at 23° 26.6’ to the vertical. The rotation of Earth about its Polar Axis takes 24 hours with respect to Sun, which is actually 23 hours, 56 minutes, and 4.09 seconds.

The question of difference arises. The fact is, Earth is orbiting around the Sun in just over 365 days to complete one orbit. Whereas, in actual 4 minutes are left per day. Explaining it own words, Earth happens to spin on its axis in a counter-clockwise motion, 360 degrees every 24 hours, at the same time Earth is orbiting and/or moving in elliptical orbit along with axial tilt around the Sun as well, with four minutes every day being caught by virtue of Sun’s position. Moreover, due to sidereal day consisting of 23.9344696 hours, a term explained as the span of time taken by Earth to rotate once on its axis, whose day-measurement is dependent on Stars and Earth in terms of their relative position. The other term is Solar Day which is explained as a span of time taken by the Sun in returning to the same spot in 24 hours. It is worth noting that Earth and other planets in the universe do not rotate around the Sun in a circular form, instead, it is in elliptical form.

As it is evident from the image of Earth Orbit above the Earth’s orbital speed varies according to its relative position to the Sun, that is, increases when it is closest to the Sun. At an average the Earth’s orbital speed is 29.8 km/s | 18.5 m/s | 107,000 km/h | 66,487 m/h. The Earth’s rotation through an elliptical orbit around the Sun is the reason resulting in a year lasting 365.2 days approximately leading to adjustment during every fourth year in February an extra day in the form of February 29th is added and known as Leap Year. Moreover, there is a slight eccentricity of 0.0167° in terms of our Plant Earth’s rotation about the Sun. This also clearly certify Earth’s periodic closeness or farther location from the Sun at certain times of the year in particular. During the months of March and September, apparent solar days are shorter as compared to the months of June or December.

### COORDINATES

Talking about the time zones we need first to understand the importance of imaginary lines of latitude drawn east and west to measure North and South. Latitude lines are initiated at the equator and meant to measure the distance from 0 degrees to 90 degrees North and South both. The Longitude lines on the other hand are drawn North and South drawn east and west to measure North and South. Longitude lines are initiated at prime meridian and/or 0 degrees and meant to measure the distance from 0 degrees to 180 degrees East and West both. This is known as Spherical Coordinate System whose origin is written as 0-degree latitude and 0-degree longitude | 0° Lat. / 0° Long…

### TIME ZONES

Taking the concepts of coordinates can help in establishing time zones as one day | 24 hours is required to complete a full circle divided into 360°, indicating earth is divided into 24 time zones and rotates 15 degrees every hour, that is, 360/24 = 15 degrees, which is a key concept in establishing time zones. In the case of Russia and the United States, they have multiple time zones, While India and China have only one time zone. We conveniently say about strict 24-hour divisions, however, some states, regions, or countries happen to shift their times by half an hour. Here, it is to be noted about the term GMT – Greenwich Mean Time or Greenwich, England was established in 1852, a zero-degree line of longitude from the North Pole to the South Pole. A standard UTC – Coordinated Universal Time was officially adopted in 1967 as the primary timekeeping standard by which all time zones are based and synchronized globally. Mind you UTC is a standard and not to be taken as a time zone. Moreover, it is to be remembered that Latitude measures your location on the globe in the North-South direction. Whereas, Longitude measures your location on the globe in an East-West direction. In order to find your time zone for example of the Philippines. First of all find Longitude from Google Earth or Internet Search, which is 121.7740 E. Convert it to Degrees, Minutes, and Seconds. 121° (0.7740 X 60 = 46.44) = 121° 46’ (0.44 X 60 = 26.4) = 121° 46’ 26.4”. Convert this to Seconds of Longitude, that is, (121 X 3600) + (46 X 60) + (26.4) = (435600) + (2760) + (26.4) = 438,386.4’. Divide this big number by 15, that is, 438386.4 / 15 = 29225.76 seconds advance or east of GMT. Convert to hours = 29225.76 / 3600 = 8.118267 Hours. 0.118267 X 60 = 7.09602 Minutes. 0.09602 X 60 = 5.7612 Seconds. Finally, the Philippines Time Zone is 8 Hours 7 Minutes 5.7612 Seconds.