Two vortices, created by the United States Coast Guard C-130J Super Hercules aircraft, rotate in the clouds over North Carolina, United States of America, on 16 April 2009. Photographer: Dave Silva, United States Coast Guard (USCG)

Two vortices, created by the United States Coast Guard C-130J Super Hercules aircraft, rotate in the clouds over North Carolina, United States of America, on 16 April 2009. Photographer: Dave Silva, United States Coast Guard (USCG)

Rear turret of Short Stirling I heavy bomber BF517 of 75 Squadron riddled with holes after being attacked by a night fighter near Duesburg – 27th April 1943 [720×930]

Rear turret of Short Stirling I heavy bomber BF517 of 75 Squadron riddled with holes after being attacked by a night fighter near Duesburg – 27th April 1943 [720×930]

‘Infantrymen of the 2nd Bn, VI Corps, 255th Inf. Regt., move down a street in Waldenburg to hunt out the Hun after a recent raid by a 63rd Div., US Seventh Army’ 1945 April 16. [1192 x 1487]

‘Infantrymen of the 2nd Bn, VI Corps, 255th Inf. Regt., move down a street in Waldenburg to hunt out the Hun after a recent raid by a 63rd Div., US Seventh Army’ 1945 April 16. [1192 x 1487]

“Choked with debris, a bombed water intake of the Pegnitz River no longer supplies war factories in Nuremberg, vital Reich industrial city and festival center of the Nazi party, which was captured April 20, 1945, by troops of the U.S. Army.” [1076 x 1424]

“Choked with debris, a bombed water intake of the Pegnitz River no longer supplies war factories in Nuremberg, vital Reich industrial city and festival center of the Nazi party, which was captured April 20, 1945, by troops of the U.S. Army.” [1076 x 1424]

The ammunition-laden Liberty ship SS Paul Hamilton is completely destroyed after being struck by a German aerial torpedo launched from a Junkers Ju 88A, 20 April 1944 [1985 x 1349]

The ammunition-laden Liberty ship SS Paul Hamilton is completely destroyed after being struck by a German aerial torpedo launched from a Junkers Ju 88A, 20 April 1944 [1985 x 1349]

Smoke rising from burning buildings in northeast Washington, D.C. on April 5, 1968 from the riots in the aftermath of the assassination of Dr. Martin Luther King Jr. [1500 x 1166]

Smoke rising from burning buildings in northeast Washington, D.C. on April 5, 1968 from the riots in the aftermath of the assassination of Dr. Martin Luther King Jr. [1500 x 1166]

San Francisco earthquake, April 18, 1906. Photographer Arnold Genthe said it shows “the results of the earth quake, the beginning of the fire and the attitude of the people.” It was taken the morning of the first day of the fire. Shows Sacramento St. at Miles Place near Powell St. [3599 x 2141]

San Francisco earthquake, April 18, 1906. Photographer Arnold Genthe said it shows “the results of the earth quake, the beginning of the fire and the attitude of the people.” It was taken the morning of the first day of the fire. Shows Sacramento St. at Miles Place near Powell St. [3599 x 2141]