- Longitude and Latitude
Game: Latitude, longitude
2. Solar System
Explore the Solar System
Game: Solar Trading Cards System
The nine planets
3. Time Zones
4. The Earth
5. Reading Maps
Transport for London
- Equator, imaginary great circle around the earth, everywhere equidistant from the two geographical poles and forming the base line from which latitude is reckoned. The equator, which measures c.24,902 mi (40,076 km), is designated as lat. 0°. It intersects N South America, central Africa, and Indonesia. The celestial equator is the projection of the plane of the earth's equator on the celestial sphere (see equatorial coordinate system).
- Prime meridian, meridian that is designated zero degree (0°) longitude, from which all other longitudes are measured. By international convention, it passes through the original site of the Royal Observatory in Greenwich, England; for this reason, it is sometimes called the Greenwich meridian. Universal time, the standard basis for determining time throughout the world, is civil time measured at the prime meridian.
- Latitude, angular distance of any point on the surface of the earth north or south of the equator. The equator is latitude 0°, and the North Pole and South Pole are latitudes 90°N and 90°S, respectively. The length of one degree of latitude averages about 69 mi (110 km); it increases slightly from the equator to the poles as a result of the earth's polar flattening.
- Longitude, angular distance on the earth's surface measured along any latitude line such as the equator east or west of the prime meridian. A meridian of longitude is an imaginary line on the earth's surface from pole to pole; two opposite meridians form a great circle dividing the earth into two hemispheres. By international agreement, the meridian passing through the original site of the Royal Greenwich Observatory at Greenwich, England, is designated the prime meridian, and all points along it are at 0° longitude.
- Tropic of Cancer, parallel of latitude at 23°30− north of the equator; it is the northern boundary of the tropics. This parallel marks the farthest point north at which the sun can be seen directly overhead at noon; north of the parallel the sun appears less than 90° from the southern horizon at any day of the year. The sun reaches its vertical position over the Tropic of Cancer at about June 22, the summer solstice in the Northern Hemisphere. When the Tropic of Cancer was named, the sun was in the constellation Cancer at the time of the summer solstice.
- Tropic of Capricorn, parallel of latitude at 23°30− south of the equator; it is the southern boundary of the tropics. This parallel marks the farthest point south at which the sun can be seen directly overhead at noon; south of the parallel the sun appears less than 90° from the northern horizon at any day of the year. The sun reaches its vertical position over the Tropic of Capricorn at about Dec. 22, the summer solstice for the Southern Hemisphere. The term Capricorn comes from the Latin words caper [goat] and cornu [horn] and is the name given to one of the 12 constellations in the zodiac.
7. A bit of everything