EcoWatch: Solar Impulse 2, the first solar airplane able to sustain flight at night with a pilot on board has been making its way around the world over the past few months. The plane took off today a little after 2 a.m. on Sunday in Nanjing, China. The flight from Nanjing to Honolulu, Hawaii is the seventh and longest leg of the first round-the-world solar flight. It will take an estimated six days to complete the roughly 5,000-mile journey. The first leg of the journey took place in early March, taking off...