Pale Blue Dot: A Vision of the Human Future in Space

13

He so named it because of the words spoken by Miranda, the heroine of The Tempest: “O brave new world, That has such people in’t.” (To Which Prospero replies, “‘Tis new to thee.” Just so. Like all the other worlds in the Solar System, Miranda is about 4.5 billion years old.)

14

It takes so long to circuit the Sun because its orbit is so vast, 23 billion miles around, and because the force of the Sun’s gravity—which keeps it from flying out into interstellar space—is at that distant comparatively feeble, less than a thousandth what it is in the Earth’s vicinity.

15

Robert Goddard, the inventor of the modern liquid-fueled rocket, envisioned a time when expeditions to the stars would be outfitted on and launched from Triton. This was in a 1927 afterthought to a 1918 handwritten manuscript called “The Last Migration.” Considered much too daring for publication, it was deposited in a friend’s safe. The cover page bears a warning: “The[se] notes should be read thoroughly only by an optimist.”

16

The Earth, by definition, is 1 AU from its star, the Sun.

17

Radio signals that both Voyagers detected in 1992 are thought to arise from the collision of powerful gusts of solar wind with the thin gas that lies between the stars. From the immense .power of the signal (over 10 trillion watts), the distance to the heliopause can be estimated: about 100 times the Earth’s distance from the Sun. At the speed it’s leaving the Solar System, Voyager 1 might pierce the heliopause and enter interstellar space around the year 2010. If its radioactive power source is still working, news of the crossing will be radioed back to the stay-at-homes on Earth. The energy released by the collision of this shock wave with the heliopause makes it the most powerful source of radio emission in the Solar System. It makes you wonder whether even stronger shocks in other planetary systems might he detectable by our radio telescope.

18

Like “gosh-darned” and “geez,” this phrase was originally a euphemism for those who considered Sacre-Dieu!, “Sacred God!,” too strong an oath, the Second Commandment duly considered, to be uttered aloud.

19

For Titan, imaging revealed a succession of detached hazes above the main layer of aerosols. So Venus works out to be the only world in the Solar System for which spacecraft cameras working in ordinary visible light haven’t discovered something important. Happily, we’ve now returned pictures from almost every world we’ve visited. (NASA’s International Cometary Explorer, which raced through the tail of Comet Giacobini-Zimmer in 1985, flew blind, be devoted to charged particles and magnetic fields.)

20

Today many telescopic images are obtained with such electronic contrivances as charge-coupled devices and diode arrays, and processed by computer—all technologies unavailable to astronomers in 1970.

21

James B. Pollack made important contributions to every area of planetary science. He was my first graduate student and a colleague ever since. He converted NASA’s Ames Research Center into a world leader in planetary research and the post-doctoral training of planetary scientists. His gentleness was as extraordinary as his scientific abilities. He died in 1994 at the height of his powers.

22

The eruption of a nearby submarine volcano and the rapid construction Of’ new island in 197 B.C. are described by Strabo in the epigraph to this chapter.

23

Even with its mountains and submarine trenches, our planet is astonishingly smooth. If the Earth were the size of a billiard ball, the largest protuberances would be less than a tenth of a millimeter in size—on the threshold of being too small to see or feel.

24

The age of the Venus surface, as determined by Magellan radar imagery, puts an additional nail in the coffin of the thesis of Immanuel Velikovsky—who around 1950 proposed, to surprising media