The speed of light is approximately 1,079,000,000 kilometers/hour (670,600,000 miles/hour). On average, the Sun is 150 million kilometers (93 million miles) away from Earth. This means that it takes a photon of light about 8 minutes and 20 seconds to travel from the Sun to Earth.
Objects in our universe are extremely far away. They’re so far away that kilometers or miles aren’t a useful measure of their distance. So we speak of space objects in terms of light-years, the distance light travels in a year. Light is the fastest-moving stuff in our universe. It travels at 186,000 miles per second (300,000 km/sec). And thus a light-year is 5.88 trillion miles (9.46 trillion kilometers).
But stars and nebulae – not to mention distant galaxies – are vastly farther than one light-year away. And, if we try to express a star’s distance in miles or kilometers, we soon end up with impossibly huge numbers. Yet miles and kilometers are what most of us use to comprehend the distance from one place on Earth to another. In the late 20th century astronomer Robert Burnham, Jr. – author of Burnham’s Celestial Handbook – devised an ingenious way to portray the distance of light-years in terms of miles and kilometers.
Credit : Earth Sky
Picture Credit : Google
