Astronomical distances refer to the vast spaces between celestial objects in the universe. These distances are often measured in units like kilometers or miles, but due to their enormity, astronomers use light-years, which is the distance light travels in one year, approximately 9.46 trillion kilometers (about 5.88 trillion miles). For example, the nearest star system, Alpha Centauri, is about 4.37 light-years away from Earth. To put this into perspective, our own galaxy, the Milky Way, is about 100,000 light-years in diameter. This means that light from one edge of the galaxy takes 100,000 years to reach the other side. Understanding these distances helps scientists study the structure and evolution of the universe.