Note 3 — BOOK IV. THE PHYSICAL PERIOD
Reading edition
Taking the velocity of light at 186,000 miles a second, and the earth’s mean distance at 93,000,000 miles, 1 light-year=5,865,696,000,000 miles or 63,072 astronomical units; 1 astronomical unit a year=2.94 miles a second; and the earth’s orbital velocity=18.5 miles a second.