Falling oil prices have put downward pressure on gasoline prices, now averaging $2.65 a gallon — about 85 cents cheaper than a year ago. Gene J. Puskar/AP hide caption

itoggle caption Gene J. Puskar/AP

The first foundation jacket installed by Deepwater Wind in the nation's first offshore wind farm construction project is seen next to a construction crane on Monday, on the waters of the Atlantic Ocean off Block Island, R.I. Stephan Savoia/AP hide caption

itoggle caption Stephan Savoia/AP

Kenyan graffiti artist Bankslave created a mural of Barack Obama. The president himself will visit Kenya on Friday. One of the president's agenda items is to promote solar power. Ben Curtis/AP hide caption

itoggle caption Ben Curtis/AP

Iran's Supreme Leader Ayatollah Ali Khamenei delivers a sermon during morning prayers for the Eid al-Fitr holiday, marking the end of the holy month of Ramadan. He signaled his approval of the nuclear agreement with Western powers but reiterated that Tehran's policy toward the "arrogant" United States would not change. Reuters/Landov hide caption

itoggle caption Reuters/Landov

"We've under-priced water, we've over-exploited it, we don't regulate how people pump groundwater out of the ground.... we just use too much."--Jonathan Foley Courtesy of TEDxTC hide caption

itoggle caption Courtesy of TEDxTC

"Our degree of oil dependency is our degree of vulnerability."--Rob Hopkins James Duncan Davidson/TED hide caption

itoggle caption James Duncan Davidson/TED