Aurora Borea

• Also known as polar auroras
• The northern lights are the most notable, but a southern aurora does occur in the southern hemisphere
• No specific or consistent measurements
• Appear as glowing sheets or dancing waves

Wonder of the World: Three Gorges Dam

When Three Gorges Dam goes fully online in China in 2009, after 17 years of construction, it will be 607 feet high and 1.4 miles long. Its reservoir will be 410 miles in length and 3,700 feet in width. It will be the largest dam on Earth, and probably the largest dam our planet will ever see.