america

This image provided by NASA March 16, 2014 shows a portion of the Florida Keys taken by Astronaut Rick Mastracchio from the International Space Station. (AP Photo/NASA, Rich Mastracchio)

Rich Mastracchio/Nasa/AP

This image provided by NASA shows a portion of the Florida Keys taken by Astronaut Rick Mastracchio from the International Space Station 

A worker power washes the West Wing of t...A worker power washes the West Wing of the White House January 15, 2014 in Washington, DC. AFP PHOTO/Brendan SMIALOWSKIBRENDAN SMIALOWSKI/AFP/Getty Images

Brendan Smialowski/AFP

A worker power-washes the West Wing of the White House in Washington D.C

The tower of New York's World Trade Center rises through a blanket of fog on Wednesday morning, Jan. 15, 2014, in this view looking south from the 48th floor at 42nd St. and 11th Ave in Midtown Manhattan. New Jersey is visible at top right.

Girish Tewani/AP

The tower of New York’s One World Trade Center pierces a blanket of fog. This photo is taken looking south from the 48th floor at 42nd Street and 11th Avenue in Midtown Manhattan. 

Travelling White House staff and press board the rear steps of Air Force One on a foggy morning in Seattle...Travelling White House staff and press board the rear steps of Air Force One on a foggy morning in Seattle, November 25, 2013. U.S. President Barack Obama is attending fundraisers and events on the economy and immigration in Los Angeles and San Francisco on Monday.

Jason Reed/Reuters

White House staff and press board the rear steps of Air Force One on a foggy morning in Seattle. US president Barack Obama is attending fundraisers and events on the economy and immigration in Los Angeles and San Francisco on Monday. 

An aerial view at night of the downtown Chicago skyline. An Arctic air mass is expected to chill much of the Central Plains and the East Coast through Monday with wind-chill temperatures dropping into the single digits overnight in some places.

Kiichiro Sato/AP

A nightime aerial view of downtown in the US city of Chicago

Artists A.Signl, left, and B.Shanti, second from right, of the artist group Captain Borderline paint their mural   'Surveillance of the fittest' at a wall in Cologne, Germany, Thursday, Oct. 24, 2013. The painting shows an American Bald Eagle with surveillance cameras watching a herd of sheep to draw attention to the spying program of the American National Security Agency. Germany demanded answers to ìall open questionsî about U.S. surveillance Thursday following allegations that American intelligence may have targeted Chancellor Angela Merkelís cellphone, and her chief of staff noted that Washington hasnít denied past snooping.

Frank Augstein/AP

Artists A Signl (left) and B Shanti (second from right), of the artist group Captain Borderline, paint a mural “Surveillance of the Fittest” on a wall in Cologne, Germany, to draw attention to the spying programme of the US intelligence services 

Police tape blocks a closed Lincoln Memo...Police tape blocks a closed Lincoln Memorial on the National Mall October 1, 2013 in Washington, DC. The US government is in a forced shutdown after lawmakers failed to pass a spending bill last night. AFP PHOTO/Brendan SMIALOWSKIBRENDAN SMIALOWSKI/AFP/Getty Images

Brendan Smialowski/AFP/Getty

Police tape blocks a closed Lincoln Memorial on Tuesday in Washington, DC. The US government is in a forced shutdown after lawmakers failed to pass a spending bill. 

An Iranian woman walks past a mural showing a gun painted with an interpretation of the American flag on the wall of the former US embassy in Tehran on September 25, 2013. Leaders from Iran and the United States have not met since the 1979 Islamic Revolution brought often open hostility to their contacts, particularly over Iran's contested nuclear program.

Atta Kenare/AFP

An Iranian woman walks past a mural showing a gun painted with an interpretation of the American flag on the wall of the former US embassy in Tehran on Wednesday. Leaders from Iran and the United States have not met since the 1979 Islamic Revolution brought often open hostility to their contacts, particularly over Iran’s contested nuclear program.

Cher...Cher arrives by police motorcycle for her performance on NBC's "Today" show on Monday, Sept. 23, 2013 in New York. (Photo by Charles Sykes/Invision/AP)

AP/Charles Sykes

Cher, the US singer and actor, arrives by police motorcycle for a performance on NBC’s Today show on Monday. 

US Army Private First Class Bradley Mann...US Army Private First Class Bradley Manning arrives alongside military officials at a US military court facility to hear his sentence in his trial at Fort Meade, Maryland on August 21, 2013. A sentencing decision will be announced later Wednesday. AFP PHOTO / Saul LOEBSAUL LOEB/AFP/Getty Images

Saul Loeb/AFP

Army Private First Class Bradley Manning arrives at a US military court facility to hear his sentence in his trial at Fort Meade, Maryland, on Wednesday. Manning was sentenced for 35 years for his part in the WikiLeaks affair 

Cyclists ride past the reflecting pool in front of the Lincoln Memorial in Washington...Cyclists ride past the reflecting pool in front of the Lincoln Memorial in Washington August 20, 2013. The Rev. Dr. Martin Luther King, Jr., delivered his "I have a Dream" speech on August 28, 1963 on the steps of the Lincoln Memorial during the March on Washington for Jobs and Freedom. This coming week, Washington will play host to an array of events marking the historic anniversary.  REUTERS/Kevin Lamarque

Kevin Lamarque/Reuters

Cyclists ride past the reflecting pool in front of the Lincoln Memorial in Washington The Rev. Dr. Martin Luther King, Jr., delivered his “I have a Dream” speech on August 28, 1963 on the steps of the Lincoln Memorial during the March on Washington for Jobs and Freedom. This coming week, Washington will play host to an array of events marking the historic anniversary

Lightning strikes above the Mandalay Bay and Luxor casinos on the Las Vegas Strip as a thunderstorm moves through Las Vegas...Lightning strikes above the Mandalay Bay (L) and Luxor (C) casinos on the Las Vegas Strip as a thunderstorm moves through Las Vegas, Nevada July 20, 2013. REUTERS/Steve Marcus (UNITED STATES - Tags: ENVIRONMENT CITYSCAPE TPX IMAGES OF THE DAY)

Steve Marcus/Reuters

Lightning strikes above the Mandalay Bay and Luxor casinos on the Las Vegas Strip as a thunderstorm moves through Las Vegas, Nevada in the US. 

Re-enactors march away from the Old State House following a public reading of the United States Declaration of Independence, part of July Fourth Independence Day celebrations, in Boston...Re-enactors march away from the Old State House following a public reading of the United States Declaration of Independence, part of July Fourth Independence Day celebrations, in Boston, Massachusetts July 4, 2013. People across the United States gathered on Thursday for parades, picnics and fireworks at Independence Day celebrations, held under unprecedented security following the Boston Marathon bombings. Spectators waving U.S. flags and wearing red, white and blue headed for public gatherings in Boston, New York, Washington, Atlanta and other cities under the close watch of police armed with hand-held chemical detectors, radiation scanners and camera surveillance, precautions sparked by the deadly April 15 bombings.      REUTERS/Brian Snyder  (UNITED STATES - Tags: ANNIVERSARY SOCIETY)

Brian Snyder/Reuters

Re-enactors march away from the Old State House after a public reading of the US Declaration of Independence, part of July 4 Independence Day celebrations, in Boston, Massachusetts on Thursday. 

Mya McNeal looks for her mother, U.S. Army Sgt. Kionna Huewitt, during a homecoming ceremony for 184 troops in the 1st Armor Brigade Combat Team after a 9-month deployment to Afghanistan, Wednesday, July 3, 2013 at Fort Stewart, Ga. (AP Photo/Stephen Morton)

Stephen Morton/AP

Mya McNeal looks for her mother, US Army Sgt. Kionna Huewitt, during a homecoming ceremony for 184 troops in the 1st Armor Brigade Combat Team after a nine-month deployment to Afghanistan on Wednesday at Fort Stewart, Georgia 

Confetti falls on the new police officers during a graduation ceremony for the July 2013 New York City Police Academy class, Tuesday, July 2, 2013 at Barclays Center in New York.  (AP Photo/Mary Altaffer)

Mary Altaffer/AP

Confetti falls on police officers on Tuesday during the graduation ceremony for the July 2013 New York City Police Academy class at Barclays Centre in New York. 

A wildfire burns homes in the Glenn Ilah area near Yarnell, Ariz. on Sunday, June 30, 2013. An Arizona fire chief says the wildfire that killed 19 members of his crew near the town was moving fast and fueled by hot, dry conditions. The fire started with a lightning strike on Friday and spread to 2,000 acres on Sunday amid triple-digit temperatures. (AP Photo/The Arizona Republic, David Kadlubowski)

David Kadlubowski/AP

A wildfire burns homes in the Glenn Ilah area near Yarnell, Arizona in the US. An Arizona fire chief says the wildfire, which killed 19 members of his crew near the town, was moving fast, fueled by hot, dry conditions. 

U.S. President Barack Obama waves as he arrives to give a speech in front of the Brandenburg Gate at Pariser Platz in Berlin.

Michael Kappeler/Reuters

Barack Obama, US president, waves as he arrives to give a speech in front of the Brandenburg Gate at Pariser Platz in Berlin on Wednesday 

A Marine closes a door to Marine One with US President Barack Obama on the South Lawn of the White House on May 28, 2013 in Washington. Obama is traveling to the New Jersey shore to survey rebuilding efforts in areas effected by last year's hurricane Sandy.     AFP PHOTO/Brendan SMIALOWSKIBRENDAN SMIALOWSKI/AFP/Getty Images

Brendan Smialowski/AFP

A Marine on Tuesday closes the door to Marine One, carrying President Barack Obama, on the south lawn of the White House, Washington. Mr Obama is travelling to the New Jersey shore to survey rebuilding efforts in areas affected by last year’s Hurricane Sandy

Michelle Obama Visits Local Washington DC School...WASHINGTON, DC - MAY 24:  U.S. first lady Michelle Obama dances with pre-kindergarten students while she visits the Savoy School May 24, 2013 in Washington, DC. The Savoy School, once one of the lowest performing schools in the District of Columbia, has shown significant signs of improvement since being designated as one of eight schools selected last year for the Turnaround Arts Initiative by the President's Committee on the Arts and the Humanities.  (Photo by Win McNamee/Getty Images)

Win McName/Getty

US First Lady Michelle Obama dances with pre-kindergarten students while she visits the Savoy School on Friday in Washington, DC. The school, once one of the lowest performing in the District of Columbia, has shown significant signs of improvement since being designated as one of eight schools selected last year for the Turnaround Arts Initiative by the President’s Committee on the Arts and the Humanities. 

S First Lady Michelle Obama (C) is surr...US First Lady Michelle Obama (C) is surrounded by 6th graders from Fairfax, Viginia's Willow Springs Elementary School during a surprise visit to the Decatur House in Washington, DC, May 22, 2013. The Decatur House is a National Trust for Historic Preservation Site which received a $ 1 million grant from American Express to preserve the Slave Quarters structure and fund educational programming.     AFP PHOTO/JIM  WATSONJIM WATSON/AFP/Getty Images

Jim Watson/AFP

Michelle Obama, the US first lady, meets sixth graders from Willow Springs elementary school in Fairfax, Virginia, during a surprise visit to Decatur House, a historic building in Washington, on Wednesday. Decatur House is a National Trust for Historic Preservation site, which received a $1m grant from American Express to preserve its slave quarters and fund educational programming