On Valentine’s Day in 1990, 6 billion kilometres from home, NASA’s unmanned Voyager 1 took the first ever family portrait of the Solar System. This included a famous image of the Earth known as the "Pale Blue Dot."

The Pale Blue Dot is easily the most inspiring, humbling, and thought-provoking image I’ve ever seen. Carl Sagan’s famous caption for the image is also exceptionally powerful and, I think, essential reading!

The term "life-changing" is overused in everyday parlance ("this burger is going to change your life!"), but I think this photograph + caption really does come about as close to any insofar as life-changing potential goes. Certainly the image did a great deal to convince me that I wanted to study and be awed by the universe.