The universe is big – really big.* Galaxies, for instance, are often large enough to hold a trillion stars. But how did these heavenly heavyweights come to be? Hear how still-mysterious dark matter is implicated in the birth of galaxies.
Also, gamma ray bursts - explosions more energetic than anything since the Big Bang - take place somewhere in the visible universe every day. What are they, and could they obliterate life on Earth?
And, the biggest cosmic mystery de jour: dark energy. Why new, super-size telescopes may finally reveal just what it is.