The dimensions of the Cosmos are so large that using familiar units of distance, such as meters or miles, chosen for their utility on Earth, would make little sense. Instead, we measure distance with the speed of light. In one second a beam of light travels186,000 miles, nearly 300,000 kilometers or seven times around the Earth. In eight minutes it will travel from the Sun to theEarth. We can say the Sun is eight light-minutes away. In a year,
it crosses nearly ten trillion kilometers, about six trillion miles, ofintervening space. That unit of length, the distance light goes in a year, is called a light-year. It measures not time but distances-enormous distances. - P3
There are some hundred billion (10 11) galaxies, each with, on the average, a hundred billion stars. In all the galaxies, there are perhaps as many planets as stars, 10" x 10" = 10 22, ten billion trillion. In the face of such overpowering numbers, what is the likelihood that only one ordinary star, the Sun, is accompanied by aninhabited planet? Why should we, tucked away in some forgottencorner of the Cosmos, be so fortunate? To me, it seems far morelikely that the universe is brimming over with life. But we humans do not yet know. We are just beginning our explorations.
* We use the American scientific convention for large numbers: one billion =1,000,000,000 = 10‘; one trillion = 1,000,000,000,000 = 1012, etc. The exponent counts the number of zeroes after the one. - P4
Blue stars are hot andyoung; yellow stars, conventional and middle-aged; red stars,
often elderly and dying; and small white or black stars are in thefinal throes of death. The Milky Way contains some 400 billionstars of all sorts moving with a complex and orderly grace. Of allthe stars, the inhabitants of Earth know close-up, so far, but one. - P5
In addition to Eratosthenes, there was the astronomer Hipparchus, who mapped the constellations and estimated thebrightness of the stars; Euclid, who brilliantly systematized ge-ometry and told his king, struggling over a difficult mathematical problem, "There is no royal road to geometry"; Dionysius ofThrace, the man who defined the parts of speech and did for thestudy of language what Euclid did for geometry; Herophilus, thephysiologist who firmly established that the brain rather thanthe heart is the seat of intelligence; Heron of Alexandria, inventorof gear trains and steam engines and the author of Automata, thefirst book on robots; Apollonius of Perga, the mathematician whodemonstrated the forms of the conic sections —ellipse, parabolaand hyperbola—the curves, as we now know, followed in theirorbits by the planets, the comets and the stars; Archimedes, thegreatest mechanical genius until Leonardo da Vinci; and the as-tronomer and geographer Ptolemy, who compiled much of whatis today the pseudoscience of astrology: his Earth-centered uni-verse held sway for 1,500 years, a reminder that intellectual capacity is no guarantee against being deadwrong.
Andamongthose great men was a great woman, Hypatia, mathematician andastronomer, the last light of the library, whose martyrdom wasboundupwith the destruction of the library seven centuries afterits founding, a story to which we will return. - P14
And if we are a speck in the immensity of space, wealsooccupy an instantin the expanse of ages. We know now that our universe—or atleast its most recent incarnation—is some fifteen or twenty billion years old. This is the time since a remarkable explosive eventcalled the Big Bang. At the beginning of this universe, there wereno galaxies, stars or planets, no life or civilizations, merely a uni-form, radiant fireball filling all of space. The passage from theChaos of the Big Bang to the Cosmos that we are beginning toknow is the most awesome transformation of matter and energythat we have been privileged to glimpse. - P16
Probably all the organic beings which have ever lived on this earth havedescended from some one primordial form, into which life was firstbreathed. ... There is grandeur in this view of life ... that, whilst thisplanet has gone cycling on according to the fixed law of gravity, from sosimple a beginning endless forms most beautiful and most wonderfulhave been, and are being, evolved.
- Charles Darwin, The Origin of Species, 1859 - P17
The fossil evidence could be consistent with the idea of a GreatDesigner; perhaps some species are destroyed when the Designerbecomes dissatisfied with them, and new experiments are attempted on an improved design. But this notion is a little discon-certing. Each plant and animal is exquisitely made; should not asupremely competent Designer have been able to make the intended variety from the start? The fossil record implies trial anderror, an inability to anticipate the future, features inconsistentwith an efficient Great Designer (although not with a Designer ofa more remote and indirect temperament). - P25
Evolution works through mutation and selection. Mutationsmight occur during replication if the enzyme DNA polymerasemakes a mistake. But it rarely makes a mistake. Mutations alsooccur because of radioactivity or ultraviolet light from the Sun orcosmic rays or chemicals in the environment, all of which canchange the nucleotides or tie the nucleic acids up in knots. If themutation rate is too high, we lose the inheritance of four billionyears of painstaking evolution. If it is too low, new varieties willnot be available to adapt to some future change in the environ-ment. The evolution of life requires a more or less precise balancebetween mutation and selection. When that balance is achieved,
remarkable adaptations occur. - P34
Biology is more like history than it is like physics. You have toknow the past to understand the present. And you have to knowit in exquisite detail. There is as yet no predictive theory of biol-ogy, just as there is not yet a predictive theory of history. The rea-sons are the same: both subjects are still too complicated for us.
But we can know ourselves better by understanding other cases.
The study of a single instance of extraterrestrial life, no matterhow humble, will deprovincialize biology. For the first time, thebiologists will know what other kinds of life are possible. Whenwe say the search for life elsewhere is important, we are not guar-anteeing that it will beeasy to find-only that it is very muchworth seekingWe have heard so far the voice of life on one small world only.
But we have at last begun to listen for other voices in the cosmicfugue. - P40
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