12/11/2012 01:31 pm ET Updated Feb 10, 2013

Blue Marble Dreams: 40th Anniversary of Iconic Photograph of Our Home

I remember the mission clearly. I was five years old. We sat in a circle on the floor in our Montessori classroom.

The teacher brought in a small black and white television and we quietly watched it unfold.

On December 7, 1972 the crew of Apollo 17 pointed their 70 mm Hasselblad out the window and snapped the most famous photograph of all time, an image that "changed humankind's view of Earth forever." They called it Blue Marble.

It's an image that at once reminds us how small, fragile and connected we are. And that we are a water planet. A small, gorgeous blue marble.

Later, I attached a poster of the cockpit of the Apollo spacecraft to the wall above my bed, next to the window.

Every night I'd carefully fly that mission from my bedroom to the moon. Out there I'd look back through the window at our beautiful blue home.

Then I'd fall asleep and dream.

Today I share blue marbles around the world with friends, strangers and colleagues to conjure up that feeling of smallness and connectedness, and to remind us of our propensity to do great things together.

As we got farther and farther away it diminished in size. Finally it shrank to the size of a marble, the most beautiful marble you can imagine. That beautiful, warm, living object looked so fragile, so delicate, that if you touched it with a finger it would crumble and fall apart.
-- James Irwin, American Astronaut