Acronym: sandy made very edible jumbo mango juice- for her- s. u. n. (pronounced son ) Because light always travels at the same speed, we can measure the distance (d) between 2 places by measuring how long it takes to get from pt. Formula: speed of light = 300,000 km/sec = 186,000 mi/sec. 1 sec = 300,000 km / 186,000 mi. 1 min = 18,000,000 km / 11,000,000 mi. 1 hr = 1,000,000,000 km / 669,000,000 mi. 1 day = 25,000,000,000 km / 16,000,000,000 mi. 1 year = 10,000,000,000,000 km / 6,000,000,000,000 mi. Beside the sun, the closest star is Alpha centauri = 4. 4 light years away. Milky way galaxy = 100,000 light years wide (very big) Local supercluster (of galaxies) = 100,000,000 light years wide. Hubble fields: gave astronomers a look at how immensely large the universe is for the first time by examining the number of galaxies present. Each galaxy has 100 billion stars in it.