On a beautiful, clear night, the stars seem so close you could almost reach out and touch them. How far away are the stars? What lies beyond them? How large is the universe as a whole?

Without knowing distances, the sky is just a starry bowl over our heads - like the dome of a planetarium. If we can figure out the distance to the stars, we will begin to see what the universe looks like in three dimensions, and we will begin to answer some of the greatest of questions: How old is the universe? Is it infinitely large? What is our place in the cosmos?

This website shows how generations of explorers have taken us, step by step, ever further into the vast expanse of the universe. It is a journey of discovery that has only just begun.

Third century BC. Aristarchus of Samos measures the distance to the Moon by looking at the shadow of the Earth during a lunar eclipse.