Exploring Earth's Imaginary Lines

Geographic Divisions

• Earth is divided into two equal parts by an imaginary line midway between the North Pole and the South Pole, called the Equator.
• The part of the Earth north of the Equator is called the Northern Hemisphere.

Latitude and Longitude

• Circles running from east to west are called parallels or lines of latitude.

Earth's Rotation

• The Earth rotates on its axis.
• The end points on the axis are called the North Pole and the South Pole.

Supersonic Airliners

• The Concorde and the Tupolev Tu-144 are the only supersonic airliners to have seen regular service.
• The last passenger flight of the Tu-144 was in June 1999.
• Concorde's last commercial flight was in October 2003.
• Supersonic business jets have been proposed as a means to bring back supersonic transport.
• Excessive noise generation is one of the drawbacks and design challenges of supersonic airliners.