"Physics tells you what you can and can't do. If you know the physics anything else is possible." — Taylor Wilson James Duncan Davidson/TED hide caption

itoggle caption James Duncan Davidson/TED

Jim and Lyn Schneider installed solar panels and batteries because bringing grid power to their house in central Wyoming was going to cost around $80,000. Leigh Paterson/Wyoming Public Radio hide caption

itoggle caption Leigh Paterson/Wyoming Public Radio

President Obama's environmental plan won't be so hard for states that have moved to cut emissions. But for others it will be more difficult. Scott Olson/Getty Images hide caption

itoggle caption Scott Olson/Getty Images

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