Geocentrism died on August 23, 1966. Centuries had passed since human beings first dispensed with the old notion that the Earth was the hub around which the universe turned. But what we know rationally and embrace intuitively are often two different things. No matter where we stood on our home planet, after all, no matter how high we climbed into — or even above — the atmosphere, Earth’s horizon still defined the limits of our vision. We could see how out-there looked from down-here, but what we never saw was the reverse. And then, 45 years ago this month, we all at once could.
In that otherwise unremarkable summer, NASA’s Lunar Orbiter 1 arrived at the moon. As it rounded the far side on one of its early orbits, it snapped this head-turning image of the Earth — carved to a mere crescent like our own little moon — rising over the dominating arc of the lunar horizon. Our species had seen the sun rise and the moon rise, but we had never seen an Earthrise. It was both an illuminating and a humbling experience — one, some scientists hoped, that would help us appreciate the fragility of our little soap bubble world. Two generations on, that’s a hope worth recalling.
Jeffrey Kluger is a senior editor for TIME and oversees science and technology reporting. He has written or co-written more than 35 cover stories for the magazine and regularly contributes articles and commentary on science and health stories. His notable cover stories include reports on global warming, the science of appetite, the Apollo 11 anniversary, and the roots of human morality.