The Believing Brain - Michael Shermer [165]
In the 1830s, an Irish nobleman named William Parsons, third earl of Rosse, constructed a thirty-six-inch telescope. Through his eyepiece he managed to barely discern spiral arms in M51—the fifty-first object in Messier’s catalog—which took everyone by surprise because even those who believed in the island universe theory had no notion of what the structure of these other galaxies (let alone our own) might be. The Whirlpool galaxy, as it came to be known, seemed to indicate movement through arms coiled around a central axis that very much resembled a whirlpool, from whence its name.8 In 1846, a supporter of the island universe theory named John Nichol suggested that some of the nebulae “are situated so deep in space that no ray from them could reach our Earth, until after traveling through the intervening abysses, during centuries whose number stuns the imagination.”9 In Nichol’s imagination that number could be as high as thirty million years. This was a stunning figure to contemplate given that the prevailing worldview among the public at the time was a biblical age no older than ten thousand years. Privately, many scientists had their doubts, but none could have known how shy of the mark their educated guesses were—off, as it turns out, by orders of magnitude of very deep lookback time.
Once again we are getting ahead of ourselves in singling out our prognosticating champions of truth. There were other lines of evidence piling up against the island universe theory, and none more powerful than what was being imaged through a new device capable of discerning the elementary constituents of light. As Isaac Newton demonstrated back in the seventeenth century, if you pass white light through a glass prism it can be spread out into its component colors. Over the centuries scientists discovered that if you magnify a band of those colors you can see vertical lines that appear to represent the elements in the substance of the object that is generating the light. For example, if you heat up an element so hot that it burns bright enough to give off light, pass this light through a prism, and magnify it, you will find a characteristic set of lines that represent that element and no other—always and everywhere.
This device is called a spectroscope, and it was first employed by a German optics technician named Joseph von Fraunhofer, who attached a crude spectroscope to his telescope and noticed that similar patterns of lines appeared in the spectra of the sun, moon, and the other planets, which followed from the fact that the moon and planets are reflecting sunlight. But when Fraunhofer analyzed other stars he found different line patterns. Was the light from the stars coming from a different source? A few decades later a physicist named Robert Bunsen (of “Bunsen burner” fame) imaged a local fire through his spectroscope and found barium and strontium in the flames. Others followed, recording spectra of all manner of heated elements, and thus was born the technology of spectroscopy and the science of astrophysics. By cataloging the characteristic lines for elements on Earth, astronomers could then turn their spectroscopes (yoked to their telescopes) to the stars—and eventually the nebulae—in order to determine their composition.
In 1861, a physicist named Gustav Kirchhoff imaged the closest star to the earth—the sun—and found lines matching those of sodium, calcium, magnesium, iron, chromium, nickel, barium, copper, and zinc. On August 29, 1864, an English amateur astronomer named William Huggins turned a spectroscope to the light coming from the bright stars Betelgeuse and Aldebaran, where he identified iron, sodium, calcium, magnesium, and bismuth, confirming that the sun was just another star, and, alternatively, that the stars are the same species of celestial object as the sun. But then Huggins confused the debate when he did a spectroscopic analysis of one of Herschel’s planetary nebulae and found only one distinct line.
At first I suspected some displacement of the prism,