Does Light Traveling Through Space Wear Out?

My telescope, set up for astrophotography in my light-polluted San Diego backyard, was pointed at a galaxy unfathomably far from Earth. My wife, Cristina, walked up just as the first space photo streamed to my tablet. It sparkled on the screen in front of us. “That’s the Pinwheel galaxy,” I said. The name is derived from its shape–albeit this pinwheel contains about a trillion stars. The light from the Pinwheel traveled for 25 million years across the universe–about 150 quintillion miles–to get to my telescope. My wife wondered: “Doesn’t light get tired during such a long journey?” Her curiosity triggered a thought-provoking conversation about light. Ultimately, why doesn’t light wear out and lose energy over time? Let’s talk about light I am an astrophysicist, and one of the first things I learned in my studies is how light often behaves in ways that defy our intuitions. Light is electromagnetic radiation: basically, an electric wave and a magnetic wave coupled together and trav ... Read full article.