The universe's vastness challenges human comprehension. It contains trillions of galaxies and countless stars. Pluto's distance highlights cosmic scales. The observable universe spans 93 billion light ...

“The cosmos is also within us, we're made of star-stuff. We are a way for the cosmos to know itself.” - Carl Sagan Compared to the Sun, how big is the Earth? What is a scale model and how does it help ...

No one knows what kicked off the Big Bang that eventually allowed the stars to begin forming. Adolf Schaller for STScI, CC BY How can a Big Bang have been the start of the universe, since intense ...

The world's most popular museum is taking on one of the world's most daunting tasks: squeezing what scientists know about the universe into a windowless gallery the size of a suburban house. The , ...

A controversial new theory about how the universe began rejects the widely-held belief that it started with a giant cosmic eruption known as the Big Bang. One scientist suggests that the cosmos grew ...

Read the full transcript of this episode. In the year 1823, a doctor named Wilhelm Olbers looked out at the night sky and wondered: if we're surrounded by so many stars, why is the night sky so dark?

The universe is generally referred to as infinite, unknown, and limitless. With over 2 trillion galaxies and millions of stars and planets, the universe is so enormous that it stretches the boundaries ...