The Cosmic Echo

Everything you know about the universe is incomplete. When you look at the stars,

you're not seeing them as they are. You're seeing them as they were.

Light takes time to reach us. Some of that light began its journey millions,

even billions of years ago. Which means some stars you see tonight no longer

exist. They've already collapsed, exploded, vanished. But their light

is still traveling. Everything we can see, planets, stars,

galaxies, makes up just five percent of the universe. The rest is

dark matter and dark energy. Forces we cannot see and barely understand.