Question: 2.15. One of the most startling scientific discoveries of the twentieth century was the announcement in 1929 by the American astronomer Edwin Hubble that the universe is expanding. If v is a galaxy's recession velocity (relative to any other galaxy) and d is its distance (from that same galaxy), Hubble's law states that v = Hd, where H is known as Hubble's constant. (To cosmologists, Hubble's constant is a critically important number—its reciprocal, after being properly scaled, is an estimate of the age of the universe.) The following are distance and velocity measurements made on 11 galactic clusters (24). Use the formula cited in Question 11.2.14 to estimate Hubble's constant.