What does AD, BC, BCE, and CE means?

We usually hear, or read these words on history books, and Bibles. But what do they really mean?

A Planet With Three Suns

Have you watched Star Wars? No? Me too. On the movie Star Wars, Luke and Anakin Skywalker's home planet, Tatooine, have two suns.

What is a Light-Year?

I remember when I was in elementary, someone (I can't remember who, specifically.) told me that one light year is equivalent to eighty Earth years. And believed that until I was in 2nd year high school. How stupid is that?! I was taught wrong.