Skylob

Explore NASA's universe: Pinch to zoom on Earth from space, swipe through today's APOD, and browse Mars rover photos on iPhone and iPad.

The observable universe stretches roughly 93 billion light-years across and holds an estimated one billion trillion stars. Yet the universe's expansion tells a stranger story: dark energy is accelerating galaxies away from one another at rates that exceed the speed of light, shrinking our cosmological horizon: The boundary beyond which no signal can ever reach us, to about 16 billion light-years. Beyond that threshold, the cosmos becomes permanently unknowable. And within all of that immensity, as Carl Sagan so movingly reminded us, we live on a pale blue dot. A single, fragile mote among countless heavenly bodies, most of which have never been named, let alone explored. That vastness isn't cause for despair, it's an invitation.