Suppose you and I still wondered whether all of the pinpoints of light in the night sky are the same distance from us. Suppose none of our contemporaries could tell us whether the Sun orbits the Earth, or vice versa, or even how large the Earth is. Suppose no one had guessed there are mathematical laws underlying the motions of the heavens.
How would - how did - anyone begin to discover these numbers and these relationships without leaving the Earth? What made anyone even think it was possible to find out “how far,” without going there?
In Measuring the Universe we join our ancestors and contemporary scientists as they tease this information out of a sky full of stars. Some of the questions have turned out to be loaded, and a great deal besides mathematics and astronomy has gone into answering them. Politics, religion, philosophy and personal ambition: all have played roles in this drama.
There are poignant personal stories, of people like Copernicus, Kepler, Newton, Herschel, and Hubble. Today scientists are attempting to determine the distance to objects near the borders of the observable universe, far beyond anything that can be seen with the naked eye in the night sky, and to measure time back to its origin. The numbers are too enormous to comprehend.
Nevertheless, generations of curious people have figured them out, one resourceful step at a time. Progress has owed as much to raw ingenuity as to technology, and frontier inventiveness is still not out of date.
When you wish upon a star, do you ever consider that the bright one over there in the Hyades might be closer than the one in the Big Dipper that you usually wish on? Or that your wish might get there faster? Although even the closest star (Proxima Centauri) is so far away (25 1/4 trillion miles) that humanity will probably never travel to it, Ferguson (Prisons of Light: Black Holes) demonstrates why knowing its distance from us is important, and not just for reasons of wish fulfillment. For only by drawing an accurate scale map of the universe, she explains, can scientists estimate its age, one of the most hotly contested issues of our time. Ferguson begins with attempts in antiquity to establish the distance to the sun and the five planets seen by the naked eye. She discusses the findings of Copernicus, Kepler and Galileo, and how each drew on the others' work. Her simple explanations of the discoveries of stellar parallax, the Doppler effect and redshift, and of absorption spectra make important scientific concepts clear for general readers. She goes on to elucidate how astronomers determine how far away other stars are by using a type of star called Cepheid, as well as the spectacular stellar self-destructions known as supernovae as "standard candles." To conclude her engrossing survey, Ferguson covers some of the paradoxes that scientists confront, such as that some estimates of the age of the universe have determined that it is younger than some of its oldest stars, and that the amount of observable mass in the universe is only about 10% of what should be there.