So miss him. Send him some love and light every time you think about him, then drop it. You’re just afraid to let go of the last bits of him because then you’ll be really alone, and you’re scared to death of what will happen if you’re really alone. But here’s what you gotta understand. If you clear out all that space in your mind that you’re using right now to obsess about this guy, you’ll have a vacuum there, an open spot – a doorway. And guess what the universe will do with the doorway? It will rush in – God will rush in – and fill you with more love than you ever dreamed. So stop using that boy to block that door. Let it go.
—  Eat, Pray, Love (Elizabeth Gilbert)
9

Ask Ethan: Does Light Always Move At The Same Speed?

“Does light always move at the same speed? If it is slowed down by something, will is stay slower after it is no longer being slowed down? Will [it] speed back up to the speed of light?”

Throughout the entire Universe, there’s a fundamental law that governs the motions of all particles: Einstein’s relativity. It states that all particles with mass can never attain the speed of light, no matter how much energy you put into it. Additionally, all massless particles only move at the speed of light, no matter what you do to either them or to the device/person observing them. No matter what reference frame you’re in, the speed of light in a vacuum is a constant. But light isn’t always in a vacuum!  From air to quartz to acrylic to glass to many other media, light can pass through transparent material, and when it does, it slows down. Not only that, but light of different energy slows down by different amounts. In what ways is the speed of light always the same, and in what ways can it change?

And most importantly, what do the known properties of light mean for the rest of the Universe? Find out on this edition of Ask Ethan!