how big is our universehome-download pdf-print-friendly pdf-credits
image one sombrero galaxy image

how far

- the sun
and planets


- across the
milky way



the distant

- how far
can we see
- how big is
the universe

point of view image
imagine this:

This composite image shows all the places in the universe that humans have been to.


the sun and planets

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.