When scientists talk about light-years, they don’t mean time—they mean distance. Light moves at about 299,792 kilometers per second (≈186,000 miles per second). In just one second, it can circle Earth more than 7 times. Over a full year, that speed adds up to: • 9.46 trillion kilometers (≈5.88 trillion miles) = 1 light-year. • That’s the yardstick astronomers use to measure the universe. Why it matters: • The nearest star system, Alpha Centauri, is about 4.37 light-years away. So the “starshine” we see left there more than four years ago. • When we look at galaxies millions of light-years away, we’re seeing them as they were millions of years in the past. Our telescopes are time machines. • Even within our own galaxy, the Milky Way, it takes light about 100,000 years to cross from one side to the other. The takeaway: A light-year isn’t just a big number. It’s a bridge between distance and time, letting us read the history of the cosmos every time we look up. 🌌 👉 Save this for...