Of course he mentioned the Japanese attack of Pearl Harbor back on December 7th 1941 which drew America into WWII. But he also mentioned the photograph taken by a NASA Astronaut on December 7th 1972.
Apollo 17 was the last manned lunar mission. No humans since have been at a range where taking a whole-Earth photograph such as The Blue Marble would be possible.
The photograph is a spectacular image of Earth. We've all seen the photograph thousands of times. Contemplating this picture is a humbling experience. It was taken an a distance of about 18,000 miles away with the sun at the photographer's back which illuminates Earth in this stunning image.
Sometimes when I'm getting too big for my britches, I look at this photograph which hangs on my office wall and it never fails to put me in my place.